,
,1,*1 2
Responses of soil inorganic nitrogen to increased temperature and plant removal during the growing season in a Sibiraea angustata scrub ecosystem of eastern Qinghai-Xizang Plateau
MA Zhi-Liang1,2, ZHAO Wen-Qiang1, ZHAO Chun-Zhang1, LIU Mei1,2, ZHU Pan1, LIU Qing,,1,*1 2
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Online:2018-01-20
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马志良, 赵文强, 赵春章, 刘美, 朱攀, 刘庆. 青藏高原东缘窄叶鲜卑花灌丛生长季土壤无机氮对增温和植物去除的响应. 植物生态学报[J], 2018, 42(1): 86-94 doi:10.17521/cjpe.2017.0086
MA Zhi-Liang.
在高寒生物区(高海拔、高纬度地区), 氮作为植被生长发育所必需的营养元素, 同时也是其最主要的限制因子(K?rner, 2003)。在高寒生态系统中, 土壤氮主要来源于动植物残体分解、根系分泌物以及大气氮沉降等过程(Bahri & Berndtsson, 1996)。土壤氮动态主要受土壤温度和水分、冻融循环、大气干湿沉降、植物群落和土壤生物活动等非生物与生物因素的综合调控(Powlson, 1993)。土壤中的氮有多种形态和性质, 可归为无机氮和有机氮两大类(罗绪强等, 2007)。无机氮主要包括硝态氮和铵态氮, 是植物从土壤中吸收氮的主要形态。土壤有机氮是土壤氮的主要组成部分, 占土壤总氮的95%左右(Wang & Bettany, 1995)。大部分的土壤有机氮虽不能直接被植物吸收, 但是可以通过土壤微生物矿化作用转化为能被植物吸收利用的无机氮(Deluca et al., 2002)。
高寒生态系统已成为响应全球气候变暖最敏感的一个区域。高寒地区土壤生物活动和酶活性长期受低温限制, 导致土壤有机质大量积累, 土壤氮矿化速率缓慢, 土壤氮被固定在较为稳定的有机质中(Boot et al., 2016)。而且这类区域冬季漫长且常具有季节性雪被覆盖以及土壤冻融, 随着全球温度升高, 低纬度高海拔地区冬季降水节律将发生变化, 雪被厚度与土壤冻融节律随之变化(IPCC, 2013)。有关研究表明, 冬季雪被及冻融循环显著影响土壤微生物活动和生物量, 进而影响凋落物分解与土壤有机质矿化过程(Bombonato & Gerdol, 2012; 胡霞等, 2014); 同时这些区域土壤生物长期适应低温环境, 土壤温度升高, 土壤生物群落结构及生物活性将会发生变化(Xiong et al., 2016), 土壤有机质矿化作用的低温限制效应减弱, 最终改变土壤氮循环过程。因此, 全球气候变暖背景下, 高寒生态系统土壤氮循环过程将发生怎样的变化, 我们并不清楚。
然而, 目前对土壤氮动态的研究主要集中在森林、草地和农田生态系统, 且主要关注土壤氮矿化过程(Bade et al., 2015; Sjogersten & Wookey, 2015; Chen et al., 2016), 尚缺乏对高寒灌丛生态系统土壤氮循环过程的研究。与森林生态系统相比, 高寒灌丛生态系统由于灌丛物种多样性和植被覆盖度较低、昼夜温差较大, 其环境条件(水分、温度)存在较大差异(吴宁, 1998; Wang et al., 2017), 且具有更为明显的季节动态。高寒灌丛生态系统土壤氮过程可能与森林生态系统不同。不同季节植物生长发育对土壤不同形态氮的需求量存在较大差异, 且与土壤微生物之间形成相对稳定的氮源竞争关系(M?nsson et al., 2009), 土壤不同形态氮可能具有明显不同的季节动态。
高寒灌丛是青藏高原东缘第二大植被类型, 在区域生态系统碳氮平衡中起着极为重要的作用(Wang et al., 2017)。窄叶鲜卑花(Sibiraea angustata)灌丛是青藏高原特有的、具有代表性的典型高寒灌丛类型, 垂直分布于海拔3β000-4β000 m (吴宁, 1998), 在川西岷江源区具有较高的群落稳定性(冶民生等, 2009)。在该区域已开展了一些关于环境变化对高寒灌丛生态系统影响的研究, 主要集中在氮添加对灌丛土壤呼吸(李娇等, 2014)、植物生物量分配和生态系统碳氮库(Wang et al., 2017)以及根系分泌物碳输入(何为等, 2017)的影响等方面。目前, 对于高寒灌丛生态系统土壤无机氮的季节动态及其如何响应全球气候变暖等相关研究仍明显不足, 这严重限制了我们对高寒灌丛生态系统土壤氮循环过程的认识。
此外, 近年来高强度的人类活动(如过度放牧、砍伐等)正在加速改变该区域灌丛植被覆盖度。植被覆盖度的改变不仅会导致土壤微环境条件的改变, 而且将打破长期以来植物与土壤微生物之间对无机氮的竞争关系(M?nsson et al., 2009; 韩雪, 2015), 进而影响土壤氮循环过程。植物生长对土壤无机氮的影响具有双重作用。一方面, 植物从土壤中吸收无机氮, 降低其含量(罗绪强等, 2007); 另一方面, 植物也为土壤矿化过程提供底物, 加速土壤氮矿化, 提高土壤无机氮含量(Yin et al., 2013)。高寒灌丛生态系统温度升高将会促进植物生长, 增加植物对土壤无机氮的竞争能力; 同时, 凋落物分解、细根周转加快, 促进土壤氮矿化过程。可见, 增温和植物将共同影响高寒灌丛土壤无机氮动态, 但是缺乏相应研究。因此, 充分理解植被干扰条件下高寒灌丛土壤无机氮的季节动态及其对增温的响应将有利于全面认识土壤氮循环过程。
本研究以青藏高原东缘窄叶鲜卑花灌丛为研究对象, 进行模拟增温、对照试验, 并设置去除/不去除植物处理, 研究植被干扰条件下土壤硝态氮和铵态氮的季节动态及其对增温的响应, 以期为更清晰地认识全球气候变暖背景下高寒灌丛生态系统土壤氮循环过程提供基础理论依据。
1 材料和方法
1.1 研究区概况
研究区位于中国科学院设在四川省阿坝州松潘县川主寺镇卡卡沟的高寒灌丛定位研究点(32.98° N, 103.67° E, 海拔3β300 m)。地势低平, 坡度约为20°。气候类型为典型的高原山地气候, 昼夜温差大。年平均气温4.8 ℃, 年降水量693 mm, 且主要集中于5-8月。季节性冻土期长达5个月。土壤类型为雏形土, 表层土壤pH值、土壤容重、有机碳和全氮含量分别为5.79、0.67 g·cm-3、89.24 g·kg-1和7.73 g·kg-1。研究区域内灌木层主要包括窄叶鲜卑花、山生柳(Salix oritrepha)、高山绣线菊(Spiraea alpina)、金露梅(Potentilla fruticosa)、刺黑珠(Berberis sargentiana)等; 草本层主要包括羊茅(Festuca ovina)、红花绿绒蒿(Meconopsis punicea)、条纹龙胆(Gentiana striata)、黄花野青茅(Deyeuxia flavens)、钟花报春(Primula sikkimensis)等。1.2 试验设计
本试验采用二因素完全随机实验设计, 设置变量为去除/不去除植物、是否增温。去除/不去除植物处理: 于2015年10月初选择研究区域内物种组成、群落结构和生境相对均匀的窄叶鲜卑花灌丛群落。在去除植物处理下(样方面积5 m × 5 m), 首先去除地表凋落物层和所有植物地上生物量, 为避免邻近灌木根系对该样方的影响, 在样方的边缘挖掘一条宽0.2 m、深0.75 m的壕沟(植物根系分布层以下), 2 mm厚的塑料薄膜贴放在壕沟周围, 然后用土回填。在不去除植物处理样方, 我们选择一株生长势良好、高度大体一致、具有相似生长势的窄叶鲜卑花植株, 在样方内不对植物进行任何处理, 保持窄叶鲜卑花植株自然生长。
模拟增温试验: 由于研究区域实际条件, 模拟增温试验使用开顶式生长室(OTC)对环境进行增温。基于窄叶鲜卑花灌丛群落的平均盖度和高度, OTC材料采用1.6 m × 1.6 m × 5 mm、透光性极好的有机玻璃板制成, 地表增温面积为2.56 m2。2015年10月中旬在每个增温样方建立一套OTC装置。特别地, 在不去除植物处理中, 我们选择1株窄叶鲜卑花植株生长于每个OTC装置的中央。在之后的采样和测定过程中, 尽量避免对窄叶鲜卑花植株生长造成影响。同时在每个OTC的附近随机设置一个对照样方。每个处理设置4个重复样方, 整个样地内共建立8套OTC, 去除/不去除植株处理下各4套。所有样方在样地内完全随机分布。
1.3 空气温度、土壤温度和水分监测
为了避免干扰对土壤环境造成的影响, 空气温度、土壤温度和水分监测于2016年5月初开始进行。利用纽扣式温度传感器(DS1921G-F5#, Maxim/Dallas semiconductor, Sunnyvale, USA)分别对各处理下70 cm空气温度和5 cm土层土壤温度进行连续监测。传感器设置为每120 min读取一次数据, 自动记录试验期间空气温度和土壤温度变化。从2016年生长季节开始, 逐月对5 cm土层土壤含水量使用便携式土壤水分测定仪(TRIME TDR, IMKO, Ettlingen, Germany)进行监测。各处理条件下70 cm空气温度、5 cm土层土壤温度和5 cm土层土壤含水量动态变化如图1所示。图1
新窗口打开|下载原图ZIP|生成PPT图1试验期间各处理下5 cm土层土壤日平均温度、70 cm空气日平均温度和5 cm土层土壤含水量(平均值±标准偏差)的季节动态。P0W0、P0W1、P1W0、P1W1分别指不同处理方式: 去除植物+不增温、去除植物+增温、不去除植物+不增温、不去除植物+增温。
Fig. 1Seasonal transitions of daily mean soil temperature at 5 cm below the soil surface, daily mean air temperature at 70 cm high and soil volumetric moisture at 5 cm below the soil surface under different treatments (mean ± SD) during the experiment period. P0W0, P0W1, P1W0, P1W1 are refer to the different treatments, indicated removal-plant + controlled temperature, removal-plant + increased temperature, unremoval-plant + controlled temperature, unremoval-plant + increased temperature, respectively.
1.4 土壤样品采集与指标分析
土壤样品采集分别于2016年灌丛植物群落生长季初期(5月20日)、中期(7月21日)和末期(9月21日)进行。土壤样品取样前, 首先小心移除地表凋落物及其他杂物。取样时, 在每个取样样方内, 沿对角线用土钻取0-15 cm土壤, 每个样方内取5钻, 然后将5个土样混合均匀作为一个混合土壤样品, 所有土样于4 ℃条件下保存并尽快带回实验室。去除石块、动植物残体后, 过2 mm筛。土壤样品均贮存于4 ℃条件下, 用于土壤含水量、硝态氮、铵态氮的测定, 所有指标测定于1周之内完成。其中, 硝态氮含量采用紫外比色法测定, 土壤铵态氮含量采用靛酚蓝比色法测定(鲁如坤, 2000)。土壤硝态氮和铵态氮含量均换算成mg·kg-1干土。
1.5 数据统计分析
使用student-t检验分别比较同一植物处理下增温和对照样方土壤温度、空气温度以及土壤含水量之间的差异。采用重复测量方差分析检验植物、增温和取样时期以及它们之间的交互作用对土壤硝态氮和铵态氮含量的影响; 采用最小显著差异法(LSD)进行同一采样时期不同处理下土壤硝态氮和铵态氮含量的多重比较。采用Pearson相关分析进行土壤水分、温度与土壤硝态氮和铵态氮含量的相关性检验。所有统计分析均在SPSS 20.0中进行, 作图使用Origin 8.5完成。2 结果和分析
2.1 温度、水分动态
如图1所示, 整个生长季节内, 与对照样方相比, OTC分别使去除/不去除植物样方70 cm处平均气温增加了1.6 ℃ (p < 0.05)和0.5 ℃, 分别使去除/不去除植物样方5 cm土层土壤平均温度增加了0.6 ℃和1.3 ℃ (p < 0.05)。并且不管增温与否, 去除植株样方的空气温度和土壤温度均高于不去除植物样方。此外, OTC没有改变空气温度和土壤温度的季节动态, OTC和对照样方(无OTC)内空气温度都随季节变化呈现有规律的动态变化。OTC明显降低了去除/不去除植物样方5 cm土层土壤含水量(图1)。在整个生长季节, 与对照样方相比, OTC分别使去除/不去除植物样方土壤含水量降低了1.35%和3.17% (p < 0.05)。纵观整个生长季节, 不管增温与否, 不去除植物样方的土壤含水量均高于去除植株样方, 且OTC对不去除植物样方土壤含水量的影响幅度大于去除植物样方。与温度变化动态类似, OTC并没有改变5 cm土层土壤含水量的季节动态, OTC和对照样方内土壤含水量都随季节而呈现有规律的动态变化。
2.2 土壤硝态氮动态
OTC增温对土壤硝态氮含量的影响因季节和植物处理的不同而存在明显差异(图2; 表1)。生长季中期(7月)和末期(9月), OTC增温使去除植物样方土壤硝态氮含量显著降低; 在不去除植物样方, OTC增温在生长季中期使土壤硝态氮含量显著升高, 却显著降低了生长季末期土壤硝态氮含量。但是, OTC增温在生长季初期(5月)并未改变去除/不去除植物样方土壤硝态氮含量。然而, 植物处理对土壤硝态氮含量的影响仅表现在对照样方, 也因季节不同而有显著差异(图2; 表1)。与不去除植物处理相比, 去除植物处理显著升高了生长季初期和中期土壤硝态氮含量, 显著降低了生长季末期土壤硝态氮含量。整个生长季节不同时期各处理下土壤硝态氮含量存在显著差异(表1), 且均表现为先增加后降低的趋势, 在生长季中期达到峰值(图2)。图2
新窗口打开|下载原图ZIP|生成PPT图2不同处理下土壤硝态氮含量的季节动态(平均值±标准偏差)。P0W0、P0W1、P1W0、P1W1分别指不同处理方式: 去除植物+不增温、去除植物+增温、不去除植物+不增温、不去除植物+增温。不同小写字母表示同一采样时期不同处理之间差异显著(p < 0.05)。
Fig. 2Seasonal dynamics of the soil nitrate contents under different treatments (mean ± SD). P0W0, P0W1, P1W0, P1W1 are refer to the different treatments, indicated removal-plant + controlled temperature, removal-plant + increased temperature, unremoval-plant + controlled temperature, unremoval-plant + increased temperature, respectively. Differences lowercase letters indicated significant differences between different treatments at the same sampling dates (p < 0.05).
Table 1
表1
表1增温(W)、植物处理方式(P)以及取样时间(D)对土壤硝态氮、铵态氮和硝态氮/铵态氮的重复测量方差分析
Table 1
| 因子 Factor | D | D × P | D × W | D × P × W | P | W | P × W |
|---|---|---|---|---|---|---|---|
| 硝态氮 Nitrate | <0.001 | <0.001 | <0.001 | 0.002 | 0.002 | 0.001 | 0.086 |
| 铵态氮 Ammonium | <0.001 | 0.949 | 0.232 | 0.368 | 0.051 | 0.496 | 0.516 |
| 硝态氮/铵态氮 Nitrate/ammonium | <0.001 | <0.001 | 0.015 | 0.025 | <0.001 | 0.001 | 0.046 |
新窗口打开|下载CSV
2.3 土壤铵态氮动态
OTC增温仅在生长季中期使不去除植物样方土壤铵态氮含量显著升高; 同时去除植物处理显著降低了OTC增温样方生长季中期土壤铵态氮含量, 在其余时期影响不显著(图3)。不同时期各处理下土壤铵态氮含量存在显著差异(表1), 整个生长季节土壤铵态氮含量均表现为一直增加的变化趋势, 在生长季末期达到峰值(图3)。此外, Pearson相关分析结果表明, 土壤铵态氮与土壤水分含量呈显著正相关, 与硝态氮含量呈显著负相关关系(表2)。图3
新窗口打开|下载原图ZIP|生成PPT图3不同处理下土壤铵态氮含量的季节动态(平均值±标准偏差)。P0W0、P0W1、P1W0、P1W1分别指不同处理方式: 去除植物+不增温、去除植物+增温、不去除植物+不增温、不去除植物+增温。不同小写字母表示同一采样时期不同处理之间差异显著(p < 0.05)。
Fig. 3Seasonal dynamics of the soil ammonium contents under different treatments (mean ± SD). P0W0, P0W1, P1W0, P1W1 are refer to the different treatments, indicated removal- plant + controlled temperature, removal-plant + increased temperature, unremoval-plant + controlled temperature, unremoval- plant + increased temperature, respectively. Differences lowercase letters indicated significant differences between different treatments at the same sampling dates (p < 0.05).
Table 2
表2
表2土壤水分、温度与土壤硝态氮和铵态氮含量的相关性
Table 2
| 指标 Index | 温度 Temperature | 水分 Moisture | 硝态氮 Nitrate | 铵态氮 Ammonium | 硝态氮/铵态氮 Nitrate/ammonium |
|---|---|---|---|---|---|
| 温度 Temperature | 1 | ||||
| 水分 Moisture | -0.527** | 1 | |||
| 硝态氮 Nitrate | 0.457** | -0.159 | 1 | ||
| 铵态氮 Ammonium | 0.047 | 0.294* | -0.404** | 1 | |
| 硝态氮/铵态氮Nitrate/ammonium | 0.232 | -0.228 | 0.829** | -0.813** | 1 |
新窗口打开|下载CSV
2.4 土壤硝态氮/铵态氮动态
与土壤硝态氮类似, OTC增温对土壤硝态氮/铵态氮的影响因季节和植物处理的不同而存在明显差异(图4; 表1)。生长季中期和末期, OTC增温显著降低了去除植物样方土壤硝态氮/铵态氮; 在不去除植物样方, OTC增温在生长季初期使土壤硝态氮/铵态氮显著升高, 而在生长季末期显著降低了土壤硝态氮/铵态氮。类似地, 植物处理方式对土壤硝态氮/铵态氮的影响也因增温和季节不同而有显著差异(图4; 表1)。与不去除植物处理相比, 在对照样方,去除植物处理显著升高了生长季初期和中期土壤硝态氮/铵态氮, 显著降低了生长季末期土壤硝态氮/铵态氮。在OTC增温样方, 去除植物处理使土壤硝态氮/铵态氮在生长季初期和中期显著升高。不同时期各处理下土壤硝态氮/铵态氮存在显著差异(表1), 整个生长季节土壤硝态氮/铵态氮大体上表现为一直降低的变化趋势, 在生长季末期达到谷值(图4)。图4
新窗口打开|下载原图ZIP|生成PPT图4不同处理下土壤硝态氮/铵态氮的季节动态(平均值±标准偏差)。P0W0、P0W1、P1W0、P1W1分别指不同处理方式: 去除植物+不增温、去除植物+增温、不去除植物+不增温、不去除植物+增温。不同小写字母表示同一采样时期不同处理之间差异显著(p < 0.05)。
Fig. 4Seasonal dynamics of soil nitrate/ammonium under different treatments (mean ± SD). P0W0, P0W1, P1W0, P1W1 are refer to the different treatments, indicated removal-plant + controlled temperature, removal-plant + increased temperature, unremoval-plant + controlled temperature, unremoval-plant + increased temperature, respectively. Differences lowercase letters indicated significant differences between different treatments at the same sampling dates (p < 0.05).
3 讨论
3.1 土壤硝态氮和铵态氮的季节动态
硝态氮和铵态氮是陆地生态系统土壤活性氮库的最主要组成部分, 同时也是陆地生态系统土壤氮循环最重要和最活跃的部分(Belaytedla et al., 2009)。在高寒生态系统中, 植物生长发育所能利用的有效氮主要形态为硝态氮和铵态氮, 土壤硝态氮和铵态氮的含量也成为衡量土壤肥力的重要指标, 其含量成为陆地生态系统植被生长发育最主要的限制因子(Rennenberg et al., 2009)。高寒生态系统中, 不同植物在不同生长发育期对土壤硝态氮和铵态氮的吸收利用格局具有明显差异(Wang et al., 2012), 土壤微生物群落结构与活性存在明显的季节变化, 导致土壤氮矿化速率存在显著的季节性差异, 因而土壤硝态氮和铵态氮含量在植物不同生长发育期有明显不同的动态(殷睿等, 2014)。本研究中, 窄叶鲜卑花灌丛土壤硝态氮和铵态氮含量呈现明显不同的季节变化(图2; 图3)。各处理下土壤硝态氮含量在不同时期差异显著(表1), 且在生长季中期达到峰值(图2)。生长季初期各处理下土壤硝态氮含量较低的原因可能是此时期土壤氮矿化速率较低, 非生长季末期冰雪融化也可能造成大量硝态氮淋溶损失(殷睿等, 2014)。土壤硝态氮含量在生长季中期达到峰值, 此时期土壤温度升高、含水量下降(图1), 土壤透气性较好, 土壤硝化作用增强(王改玲等, 2010); 另外, 土壤微生物生物量碳、氮在这一时期均明显升高, 硝化细菌在这一时期的群落优势度可能增加, 在一定程度上可提高土壤硝态氮含量(Steven et al., 2006)。而在生长季末期各处理下土壤硝态氮含量降低至最低值, 生长季末期各处理土壤温度在5-10 ℃之间波动, 土壤体积含水量保持在25%左右(图1), 土壤透气性不如生长季中期, 喜厌氧环境的反硝化细菌可能大量生长、繁殖, 反硝化作用的加强消耗了土壤中大量的硝态氮(Lu et al., 2015), 可能造成硝态氮含量显著降低。窄叶鲜卑花灌丛土壤铵态氮和硝态氮含量的季节动态不一致, 土壤铵态氮含量在生长季初期和中期较低, 原因可能是由于受土壤温度和水分的影响, 此时期氨化作用过程较弱、土壤硝化作用较强, 土壤中大量的铵态氮转化成硝态氮, 导致此时期内铵态氮含量较低(Suseela et al., 2014; 殷睿等, 2014)。相关分析结果也表明, 土壤硝态氮含量与铵态氮含量显著负相关(表2)。同时, 土壤中大量的铵态氮转化成硝态氮, 也导致了这两个时期土壤硝态氮/铵态氮较高(图4)。在生长季末期, 土壤铵态氮含量达到峰值, 此时期土壤温度和水分条件可能有利于土壤微生物氨化和反硝化过程的进行(Liu et al., 2016; Palta et al., 2016), 土壤硝态氮/铵态氮在这一时期也较低(图4)。本研究还发现, 在生长季初期和中期, 各处理土壤硝态氮含量均显著高于铵态氮含量, 而在生长季末期土壤硝态氮含量均显著低于铵态氮含量(图4)。这说明该区域土壤氮矿化在生长季初期和中期以硝化作用为主, 而在生长季末期以氨化作用为主。3.2 土壤硝态氮和铵态氮对增温的响应
土壤硝态氮和铵态氮含量对OTC增温的响应因季节和植物处理的不同而存在显著差异(图2, 图3; 表1), OTC增温使不去除植物样方在生长季中期土壤硝态氮和铵态氮含量显著升高(图2, 图3)。一般来说, 土壤温度升高会提高微生物活动、促进土壤氮循环, 土壤硝态氮和铵态氮的转化过程也随温度增加而加快(Bai et al., 2013)。与去除植物样方相比, OTC使不去除植物样方的土壤增温幅度更大(图1), 尤其在生长季中期, 这将有利于土壤硝态氮和铵态氮积累。这一时期土壤中较高的硝态氮和铵态氮含量将能满足正处于生长旺季的灌丛植被对氮的需求, 有利于植物的生长发育。生长季中期(7月)和末期(9月), OTC增温使去除植物样方土壤硝态氮含量显著降低(图2), 可能是增温导致了土壤含水量降低(表1), 土壤受到严重的水分限制, 从而抵消了增温对微生物氮矿化的正效应(Bai et al., 2013; Hu et al., 2017)。武丹丹等(2016)的研究结果也表明, 增温使土壤硝态氮含量降低了46.1%。他们认为增温导致的土壤水分下降对微生物氮矿化的限制作用是其最主要原因。去除植物样方同时去除了地上凋落物和地上部分生物量, 其根系分泌物的数量也显著减少, 土壤有机质的来源不足导致土壤矿化过程底物减少, 进一步限制了增温对氮矿化的促进效应(Bruijn & Butterbach-Bahl, 2010; Yin et al., 2013)。我们同时观察到去除植物样方土壤铵态氮含量受增温的影响不显著(图3), 因而土壤硝态氮/铵态氮在这两个时期显著降低(图4)。因此, 增温对窄叶鲜卑花高寒灌丛土壤硝态氮和铵态氮含量具有双重影响, 同时受到植物生长的调控。但是, OTC增温在生长季初期并未影响去除/不去除植物样方土壤硝态氮和铵态氮含量(图3)。原因可能是增温时间短, 而且此时期内土壤温度、含水量较低, 土壤氮矿化过程受增温的影响不显著(Xu et al., 2010)。而且, 整个生长季节, 土壤铵态氮含量对OTC增温的响应不如硝态氮敏感(表1; 表2), 这说明土壤硝化过程受温度的影响更大(Steven et al., 2006), 土壤温度较小的波动(0.6-1.3 ℃) (图1), 即可引起土壤硝化细菌作出强烈的反应。相关分析也表明, 土壤温度与土壤硝态氮含量呈显著负相关关系(表2)。3.3 土壤硝态氮和铵态氮对植物处理方式的响应
植物处理方式对土壤硝态氮和铵态氮含量的影响也不一致。与土壤铵态氮含量相比, 土壤硝态氮含量受植物生长的影响更大(表1), 且仅表现在对照样方。不去除植物处理在对照样方显著降低了生长季初期和中期土壤硝态氮含量, 而对土壤铵态氮含量的影响不显著, 从而显著降低了土壤硝态氮/铵态氮(图2, 图3, 图4), 说明窄叶鲜卑花灌丛植被在生长季初期和中期可能主要吸收利用硝态氮, 而且吸收过程受土壤增温的影响不大, 此时期土壤矿化过程以硝化作用为主, 土壤中硝态氮的含量显著高于铵态氮含量(图4), 也进一步促进了植物对硝态氮的吸收; 增温和植物处理的交互作用对土壤硝态氮含量的影响不显著也说明了这一点(表1)。这与一些研究结果相悖, 如在高寒草地生态系统的相关研究表明, 一些植物偏好对铵态氮吸收(王金牛等, 2013)。产生这种差异的原因可能是高寒生态系统木本植物和草本植物的自身特性差异以及因物候格局的不同所导致的对土壤有效养分利用存在很大差异(Moreau et al., 2015)。不去除植物处理显著增加了对照样方生长季末期土壤硝态氮含量(图2)。与去除植物样方相比, 不去除植物样方为土壤微生物提供了丰富的有机质来源(凋落物、根系分泌物、细根周转), 这将有利于土壤硝化细菌的生长、繁殖, 加强土壤硝化作用(Yin et al., 2013); 此时期植物处于生长季末期, 对土壤氮的吸收速率减弱, 有利于土壤硝态氮的积累(Moreau et al., 2015)。同时, 不去除植物处理显著增加了OTC增温样方在生长季中期土壤铵态氮含量, 显著降低了土壤硝态氮/铵态氮(图3, 图4), 这说明植物生长为土壤氨化细菌提供底物可能加速增温条件下土壤氨化作用。有研究表明, 植物因素对土壤有效态氮的影响大于微生物因素(Jackson et al., 2008), 在本研究中主要体现在灌丛植被对土壤硝态氮的吸收方面。综上所述, 青藏高原东缘窄叶鲜卑花灌丛土壤硝态氮和铵态氮含量具有明显的季节动态, 增温和不同植物处理在植物不同生长季节对土壤铵态氮和硝态氮含量具有不同的影响。植物生长季初期和中期, 土壤氮矿化过程以硝化作用为主, 高寒灌丛植被在生长旺季可能增加对硝态氮的吸收。以上结果可为进一步理解高寒灌丛生态系统土壤氮转化及其循环过程提供一定的基础理论依据。
参考文献 原文顺序
文献年度倒序
文中引用次数倒序
被引期刊影响因子
DOI:10.1007/s13595-014-0394-0URL [本文引用: 1]
Context Old-growth forests with natural forest development and complex stand structure have become extremely rare in Central Europe. Changes of biogeochemistry and the N cycle across a full forest development cycle are not well understood.61 Aims We tested the hypothesis that net N mineralization and the relative importance of nitrification are increasing with proceeding forest development from regeneration to decay stages.61 Methods In an unmanaged old-growth spruce forest, we measured net ammonification and nitrification rate in the five forest development stages in 202years using the intact soil core incubation method.61 Results Net N mineralization (and ammonification) rates were higher in the closed stands of the optimum and over-mature stages than in the more open decay and regeneration stages. Only a small proportion of NH4+ was oxidized to NO361 in the studied acidic soils.61 Conclusion Lower N mineralization in the more open than the closed patches of this natural forest is unexpected, contrasting with the findings from artificial gaps. Possible reasons are reduced litter supply and lower canopy N interception in gaps in this forest under exposure to high N deposition. Further studies in other old-growth forests are needed to better understand the mechanisms causing long-term change in N cycling with forest development.61 Key messageNitrogen mineralization was higher in the optimum and over-mature stages with closed canopy than in the more open decay and regeneration stages of an unmanaged old-growth forest with high atmospheric nitrogen load, in contrast to published experiments with artificial gaps.
DOI:10.1097/00010694-199605000-00004URL [本文引用: 1]
ABSTRACT Sewage sludge amendment of soils leads to an increase in soil fertility, but may induce heterogeneities not initially present in the soil. Spatial variation of soil organic carbon (C) and nitrogen (N) was studied in a heavy clay soil after a sewage sludge application and NPK-treatment (nitrogen, phosphorus, and potassium) using geostatistical approaches. In total, 314 soil samples were taken on two adjacent 40 m 40 m plots (one sludge-amended and one NPK-treated) at three different scales (scale 40 m: 40 m 40 m, scale 10 m: 10 m 10 m, and scale 2.5 m: 2.5 m 2.5 m). The coefficient of variation almost doubled for both C and N after sludge treatment. Because of this, more samples were needed to estimate mean values for the sludge-amended plot compared with the NPK-treated plot. To estimate the population mean at the 95% confidence level with 10% uncertainty (for all scales and all treatments), 5 to 13 samples were required for C and 4 to 7 for N. The C was spatially more structured compared to N. Semivariances of the sludge-amended plot displayed higher values compared with the NPK-treated plot, except for N at the smallest scale. This was probably due mainly to the sludge characteristics and the application technique of the sewage sludge. Constant semivariance (sill) was reached at ranges up to 15 m for C, but it was often unbounded (>40 m) for N.
DOI:10.1111/nph.12252URLPMID:23550663 [本文引用: 2]
Global warming may have profound effects on terrestrial ecosystems. However, a comprehensive evaluation of the effects of warming on ecosystem nitrogen (N) pools and dynamics is not available.Here, we compiled data of 528 observations from 51 papers and carried out a meta-analysis of experimental warming effects on 13 variables related to terrestrial N pools and dynamics.We found that, on average, net N mineralization and net nitrification rate were increased by 52.2 and 32.2%, respectively, under experimental warming treatment. N pools were also increased by warming, although the magnitude of this increase was less than that of N fluxes. Soil microbial N and N immobilization were not changed by warming, probably because microbes are limited by carbon sources. Grassland and shrubland/heathland were less responsive to warming than forest, probably because the reduction of soil moisture by warming offset the temperature effect in these areas. Soil heating cable and all-day treatment appeared to be the most effective method on N cycling among all treatment methods.Results of this meta-analysis are useful for better understanding the response of N cycling to global warming and the underlying mechanism of warming effects on plants and ecosystem functions.
DOI:10.1016/j.soilbio.2008.10.003URL [本文引用: 1]
Carbon (C) and nitrogen (N) fluxes are largely controlled by the small but highly bio-reactive, labile pools of these elements in terrestrial soils, while long-term C and N storage is determined by the long-lived recalcitrant fractions. Changes in the size of these pools and redistribution among them in response to global warming may considerably affect the long-term terrestrial C and N storage. However, such changes have not been carefully examined in field warming experiments. This study used sulfuric acid hydrolysis to quantify changes in labile and recalcitrant C and N fractions of soil in a tallgrass prairie ecosystem that had been continuously warmed with or without clipping for about 2.5 years. Warming significantly increased labile C and N fractions in the unclipped plots, resulting in increments of 373 mg C kg 1 dry soil and 15 mg N kg 1 dry soil, over this period whilst clipping significantly decreased such concentrations in the warmed plots. Warming also significantly increased soil microbial biomass C and N in the unclipped plots, and increased ratios of soil microbial/labile C and N, indicating an increase in microbial C- and N-use efficiency. Recalcitrant and total C and N contents were not significantly affected by warming. For all measured pools, only labile and microbial biomass C fractions showed significant interactions between warming and clipping, indicating the dependence of the warming effects on clipping. Our results suggest that increased soil labile and microbial C and N fractions likely resulted indirectly from warming increases in plant biomass input, which may be larger than warming-enhanced decomposition of labile organic compounds.
DOI:10.1007/s10584-012-0405-9URL [本文引用: 1]
Snow amount is expected to decline in the Northern hemisphere as an effect of climate warming. However, snow amount in alpine regions will probably undergo stronger interannual fluctuations than elsewhere. We set up a short-term (1 year) experiment in which we manipulated snow cover in an alpine bog, with the following protocol: snow removal at the end of winter; snow removal in spring; snow addition in spring; removal of all aboveground plant tissues with no snow manipulation; no manipulation at all. We measured, at different dates from late spring to early autumn: ecosystem respiration (ER), and concentrations of carbon (C), nitrogen (N) and phosphorus (P) in the soil and in microbes. We hypothesized that longer duration of snow cover will lead to: i) higher ER rates associated with increased microbial biomass; and ii) decreased soil nutrient availability. Contrary to our first hypothesis, ER and microbial C content were unaffected by the snow cover manipulations, probably because ER was decoupled from microbial biomass especially in summer, when CO 2 efflux was dominated by autotrophic respiration. Our second hypothesis also was partially contradicted because nutrient content in the soil and in plants did not vary in relation to snow cover. However, we observed unexpected effects of snow cover manipulations on the N : P ratio in the microbial biomass, which declined after increasing snow cover. This probably depended on stimulation of microbial activity, which enhanced absorption of P, rather than N, by microbes. This may eventually reduce P availability for plant uptake.
DOI:10.1016/j.soilbio.2015.10.002URL [本文引用: 1]
61N amendments decreased organic soil pH, microbial biomass C and % C.61N amendments altered microbial community structure.61Fertilization decreased arbuscular mycorrhizal and saprotrophic fungal abundance.61Spring, but not fall bacterial abundance was reduced by N amendments.61N degrading enzymes activities were elevated in N amendment plots.
DOI:10.1007/s11104-009-0108-9URL [本文引用: 1]
Simulation of decomposition and inorganic nitrogen release in complex biogeochemical models can be based on different principles. A major problem is the link between carbon and nitrogen mineralization and a description of microbial growth dynamics in dependence of a suite of possible substrates. This contribution considers a first order decomposition model with several carbon pools and one nitrogen pool to investigate how the decomposition of plant types and mineralization of nitrogen is related to carbon quality. The model structure assumes that nitrogen is mobilised with the rate at which the lignin compounds decompose. The decomposition module is coupled with microbial dynamics by adjusted Michaelis Menten equations that relate microbial growth to the availability of various substrates. The model was calibrated using Markov Chain Monte Carlo ( MCMC ) applied to measured litter remnants, concentrations of lignin, cellulose and nitrogen from 30 in situ incubations of foliage litters. Additionally, data from a laboratory incubation experiment were used to analyse the formation of microbial biomass, dissolved organic nitrogen, ammonium (NH 4 + ) and microbial respiration. Parameter sensitivity was analysed according to the rate of acceptance of various settings in the MCMC calibration chain. The most important parameters for the decomposition process were the decomposition rate of lignin, and the temperature response parameter Q 10 . The most important parameters for the formation of microbial biomass, dissolved organic nitrogen, ammonium and microbial respiration, were the potential growth rate of the microbial population and the rate of microbial decay. Estimated optimal decomposition rates for field experiments are 0.00365±650.002 d 611 for lignin like compounds, 0.00665±650.004 d 611 for cellulose like compounds and 0.028665±650.052 d 611 for solutes. The temperature response parameter Q 10 is 3.265±650.6 and the optimum decomposition temperature is 28.165±654.3°C. Important model parameters on microbial biomass and nitrification are the maximum microbial growth rate μ MAX 65=650.1365±650.82 gC mic gC mic 611 d 611 or the rate of microbial decay D 65=650.00665±650.014 gC mic gC mic 611 d 611 . The model performance was tested for independent datasets. Generally, correlations between modelled and measured values, expressed in R 2 , were high for the remaining tissue dry weight, or concentrations of lignin, cellulose and solutes or organic nitrogen ( R 2 65>650.84). Due to uncertainties in measurements of DON and NH 4 + concentrations, microbial biomass or basal respiration and significant site variability in these parameters, the model performance for these parameters as expressed as R 2 was somewhat lower, but statistically highly significant, and in the range of 0.1-0.96.
DOI:10.1007/s12665-015-4786-8URL [本文引用: 1]
Soil organic matter (SOM) and total nitrogen (STN) play an important role in terrestrial ecosystems. Knowledge of their regional distribution and dynamical change is an important basis for reasonable utilizing and protecting soil resources. However, very little attention has been paid to this in cultivated land of the southern Loess Plateau. In this study, Heyang County, an agricultural county located in the southern Loess Plateau, was chosen as study area. SOM and STN data were collected in 1983 and 2006. Spatial autocorrelation, geostatistics, and fractal methods were used to analyze their spatio-temporal variability. Results showed that mean contents of SOM and STN had significantly increased in the past 23 years. A relatively more increase was found in the southeast and relatively less increase in the northern half. Compared with those in 1983, SOM and STN contents in 2006 showed a higher nugget/sill ratio, shorter spatial autocorrelation distance, and larger fractal dimension, indicating that the spatial dependence of SOM and STN showed a weakening trend and a stronger spatial variability of the 2006 dataset. The main factors affecting SOM and STN changes were topography, soil type, and farm management practices. But, more and more impacts were derived from anthropogenic activities.
DOI:10.1007/s00442-002-1025-2URLPMID:28547308 [本文引用: 1]
Scots pine ( Pinus sylvestris L.) forests of northern Sweden are often considered to be N limited. This limitation may have been exacerbated by the elimination of wildfire as a natural disturbance factor in these boreal forests. Phenolic inhibition of N mineralization and nitrification (due to litter and exudates of ericaceous shrubs) has been proposed as a mechanism for N limitation of these forests, but this hypothesis remains largely untested. N mineralization rates, nitrification rates, and sorption of free phenolic compounds were assessed along a fire-induced chronosequence in northern Sweden. A total of 34 forest stands varying in age since the last fire were identified and characterized. Overstorey and understorey vegetative composition and depth of humus were analysed in replicated plots at all 34 sites. Eight of the forest stands aged 3–35202years since the last fire were selected for intensive investigation in which ten replicate ionic resin capsules (used to assess net N mineralization and nitrification) and non-ionic carbonaceous resin capsules (used to assess free phenolic compounds) were installed at the interface of humus and mineral soil. A highly significant correlation was observed between site age and net sorption of inorganic N to resin capsules. Net accumulation of NH 4 + and NO 3 – on resin capsules followed a linear decrease ( R 2 =0.61, P <0.01) with time perhaps as a result of increased N immobilization with successional C loading. NO 3 – sorption to resin capsules followed a logarithmic decrease ( R 2 =0.80, P <0.01) that may be related to a logarithmic increase in dwarf shrub cover and decreased soil charcoal sorption potential along this chronosequence. A replicated field study was conducted at one of the late successional field sites to assess the influence of charcoal and an added labile N source on N turnover. Three rates of charcoal (0, 100, and 1,00002g M –2 ) and two rates of glycine (0 and 5002g N as glycine M –2 ) were applied in a factorial design to microplots in a randomized complete block pattern. Net ammonification (as assessed by NH 4 + sorption to resins) was readily increased by the addition of a labile N source, but this increase in NH 4 + did not stimulate nitrification. Nitrification was stimulated slightly by the addition of charcoal resulting in similar levels of resin-sorbed NO 3 – as those found in early successional sites. Resin-sorbed polyphenol concentrations were decreased with charcoal amendments, but were actually increased with N amendments (likely due to decomposition of polyphenols). Net N mineralization appears to be limited by rapid NH 4 + immobilization whereas nitrification is limited by the lack of an appropriate environment or by the presence of inhibitory compounds in late successional forests of northern Sweden.
URL [本文引用: 1]
目前我国氮沉降量仅位列欧洲、北美之后,日益增加的氮沉降会改变森林土壤氮素供应,进而影响土壤氮(N)循环及植物、土壤微生物对氮素的吸收利用。本文通过野外模拟氮沉降,运用充分运用野外监测、同位素示踪、室内分析等方法,来研究温带森林土壤微生物、植物对氮素的竞争在增氮情况下的响应,以期为森林系统生态管理及对氮沉降的深入研究提供参考。本研究以温带森林土壤为研究对象,分析不同形态氮(硝态氮、铵态氮和混合态氮)和不同剂量氮添加(对照0 kg·hm-2·a-1、低氮处理50 kg·hm-2·a-1和高氮处理150kg·hm-2·a-1)对温带森林土壤可矿化氮、土壤N20排放通量,及土壤微生物、植物对氮素的竞争的影响,并从土壤酶活性的角度来解释其变化机制。主要研究结果表明：氮添加均促进了土壤氮的矿化速率,且以硝态氮添加氮的平均日净氮矿化速率最高,是对照样地的5.9倍。不同形态、不同剂量的氮添加均显著提高了土壤无机氮含量,其中,铵态氮添加对土壤铵态氮含量影响最大,硝态氮添加对土壤硝态氮含量影响最大,高氮添加比低氮添加对无机氮的增幅更大。施氮显著促进了森林土壤N20的排放。对于不同形态氮添加,混合态氮添加对土壤N20排放的促进作用最为显著,不同剂量氮添加,土壤N20排放随着施氮剂量的增加而增加。土壤脲酶、磷酸酶和过氧化氢酶活性的提高增加了土壤无机氮的含量,即促进了土壤氮的输入；土壤脲酶、多酚氧化酶、磷酸酶和过氧化氢酶活性能显著促进森林土壤N20的排放,即促进了氮的输出。本文通过利用同位素示踪方法对温带森林植物-微生物竞争氮素影响进行研究,结果表明：无论施加NH4+-N还是NO3--N,植物固持的氮均高于土壤微生物,沉降到森林生态系中的氮大部分被植物固持。外加氮源显著提高了植物和微生物对氮素的固持。在氮添加样地和对照样地中,N03--15N的总恢复率分别为50.63%和85.68%,相应NH4+-15N的恢复率则为28.35%和39.59%。土壤微生物和植物对NO3--N的吸收产生了偏好。
URL [本文引用: 1]
目前我国氮沉降量仅位列欧洲、北美之后,日益增加的氮沉降会改变森林土壤氮素供应,进而影响土壤氮(N)循环及植物、土壤微生物对氮素的吸收利用。本文通过野外模拟氮沉降,运用充分运用野外监测、同位素示踪、室内分析等方法,来研究温带森林土壤微生物、植物对氮素的竞争在增氮情况下的响应,以期为森林系统生态管理及对氮沉降的深入研究提供参考。本研究以温带森林土壤为研究对象,分析不同形态氮(硝态氮、铵态氮和混合态氮)和不同剂量氮添加(对照0 kg·hm-2·a-1、低氮处理50 kg·hm-2·a-1和高氮处理150kg·hm-2·a-1)对温带森林土壤可矿化氮、土壤N20排放通量,及土壤微生物、植物对氮素的竞争的影响,并从土壤酶活性的角度来解释其变化机制。主要研究结果表明：氮添加均促进了土壤氮的矿化速率,且以硝态氮添加氮的平均日净氮矿化速率最高,是对照样地的5.9倍。不同形态、不同剂量的氮添加均显著提高了土壤无机氮含量,其中,铵态氮添加对土壤铵态氮含量影响最大,硝态氮添加对土壤硝态氮含量影响最大,高氮添加比低氮添加对无机氮的增幅更大。施氮显著促进了森林土壤N20的排放。对于不同形态氮添加,混合态氮添加对土壤N20排放的促进作用最为显著,不同剂量氮添加,土壤N20排放随着施氮剂量的增加而增加。土壤脲酶、磷酸酶和过氧化氢酶活性的提高增加了土壤无机氮的含量,即促进了土壤氮的输入；土壤脲酶、多酚氧化酶、磷酸酶和过氧化氢酶活性能显著促进森林土壤N20的排放,即促进了氮的输出。本文通过利用同位素示踪方法对温带森林植物-微生物竞争氮素影响进行研究,结果表明：无论施加NH4+-N还是NO3--N,植物固持的氮均高于土壤微生物,沉降到森林生态系中的氮大部分被植物固持。外加氮源显著提高了植物和微生物对氮素的固持。在氮添加样地和对照样地中,N03--15N的总恢复率分别为50.63%和85.68%,相应NH4+-15N的恢复率则为28.35%和39.59%。土壤微生物和植物对NO3--N的吸收产生了偏好。
DOI:10.17521/cjpe.2016.0329URL [本文引用: 1]
为探究高寒灌丛生态系统根系分泌物碳（C）输入通量对大气氮（N）沉降的响应规律,该文以青藏高原东缘窄叶鲜卑花（Sibiraea angustata）灌丛为研究对象,采用根系分泌物野外原位收集法,分析了不同施N水平（对照N0=0 g·m~（–2）·a~（–1）;低N处理N5=5 g·m~（–2）·a~（–1）;高N处理N10=10 g·m~（–2）·a~（–1））对根系分泌物C输入速率与通量季节动态变化规律的影响。结果表明：（1）窄叶鲜卑花灌丛单位根生物量、单位根长、单位根表面积根系分泌物C输入速率均表现出明显的季节性动态变化,具体表现为8月〉6月〉10月,并呈现出与5 cm土壤温度相一致的变化趋势。（2）施N降低了窄叶鲜卑花灌丛单位根生物量、单位根长和单位根表面积根系分泌物C输入速率,但仅N10处理与对照（N0处理）间存在显著差异（p〈0.05）。（3）N5和N10处理下,窄叶鲜卑花灌丛细根生物量与N0处理相比分别降低了23.36%和33.84%。（4）由于施N导致根系分泌物C输入速率与细根生物量二者均显著降低,使得施N对窄叶鲜卑花灌丛根系分泌物C输入通量（g·m~（–2）·a~（–1））有显著的抑制作用,并随着施N浓度的增加抑制作用增大。推测其可能的原因是N素富集在一定程度上缓和了植物根系对养分的微生物驱动需求,从而降低了植物根系分泌物C输入通量,即N素富集条件下植物采取了低N收益-低C投入的生理策略。该研究结果对于进一步认知不同环境变化下高寒灌丛生态系统根系分泌物C输入及其介导的土壤生物C-养分循环过程具有重要的理论意义。
DOI:10.17521/cjpe.2016.0329URL [本文引用: 1]
为探究高寒灌丛生态系统根系分泌物碳（C）输入通量对大气氮（N）沉降的响应规律,该文以青藏高原东缘窄叶鲜卑花（Sibiraea angustata）灌丛为研究对象,采用根系分泌物野外原位收集法,分析了不同施N水平（对照N0=0 g·m~（–2）·a~（–1）;低N处理N5=5 g·m~（–2）·a~（–1）;高N处理N10=10 g·m~（–2）·a~（–1））对根系分泌物C输入速率与通量季节动态变化规律的影响。结果表明：（1）窄叶鲜卑花灌丛单位根生物量、单位根长、单位根表面积根系分泌物C输入速率均表现出明显的季节性动态变化,具体表现为8月〉6月〉10月,并呈现出与5 cm土壤温度相一致的变化趋势。（2）施N降低了窄叶鲜卑花灌丛单位根生物量、单位根长和单位根表面积根系分泌物C输入速率,但仅N10处理与对照（N0处理）间存在显著差异（p〈0.05）。（3）N5和N10处理下,窄叶鲜卑花灌丛细根生物量与N0处理相比分别降低了23.36%和33.84%。（4）由于施N导致根系分泌物C输入速率与细根生物量二者均显著降低,使得施N对窄叶鲜卑花灌丛根系分泌物C输入通量（g·m~（–2）·a~（–1））有显著的抑制作用,并随着施N浓度的增加抑制作用增大。推测其可能的原因是N素富集在一定程度上缓和了植物根系对养分的微生物驱动需求,从而降低了植物根系分泌物C输入通量,即N素富集条件下植物采取了低N收益-低C投入的生理策略。该研究结果对于进一步认知不同环境变化下高寒灌丛生态系统根系分泌物C输入及其介导的土壤生物C-养分循环过程具有重要的理论意义。
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DOI:10.1016/j.catena.2017.02.014URL [本文引用: 1]
Global warming and nitrogen (N) deposition are important factors impacting soil carbon (C) and N cycling. Termites are important ecosystem engineers that can also strongly affect C and N cycling, potentially in interaction with warming and N deposition. In addition, non-additive effects that magnify or reduce their impacts on soil element cycles may occur when termite nests and adjacent soils are mixed due to their divergent properties but this has not been investigated. Here, we collected termite nests and trails built in wood (“termite nest soils”) and adjacent control soils in forests at Lu Mountain (Jiangxi, China) to investigate effects of termites, warming, and N deposition on C and N processes. We measured CO 2 emissions, N 2 O emissions, net N mineralization, and net nitrification when soils were incubated at different temperatures (1502°C, 2502°C, or 3502°C) and levels of N deposition (control vs. 402g02N02m 61022 ). Termite nest soils were characterized by higher dissolved organic C and CO 2 emissions. CO 2 emissions decreased with N addition and increased with temperature. N 2 O emissions increased with N deposition and increased with temperature, especially in termite nest soils and mixed soils. Net N mineralization rates increased with temperature but increases were smaller and more gradual in control and mixed soils than in termite soils. Mixing termite nest soils and control soils imposed synergistic (N mineralization: up to 57% higher than expected; nitrification: up to 170% higher; N 2 O emissions without N addition: 18% higher) and antagonistic (CO 2 emissions: 7% lower; N 2 O emissions with N addition: 28% lower) mixing effects, indicating termite impacts on soil C and N cycling might be under- and over-estimated, respectively, based on each soil alone. In light of the remarkable abundance of termites, the effects of mixing termite nest soils and the control soils on soil C and N cycling should be considered in the context of global change.
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DOI:10.1146/annurev.arplant.59.032607.092932URL [本文引用: 1]
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DOI:10.1111/gcb.13372URLPMID:27234363 [本文引用: 1]
Abstract Soil net nitrogen (N) mineralization (Nmin) is a pivotal process in global N cycle regulating the N availability of plant growth. Understanding the spatial patterns of Nmin its temperature sensitivity to changing temperature (Q10) and regulatory mechanisms is critical to improve the management of soil nutrients. In this study, we collected 379 peer reviewed scientific papers to explore how Nmin and the Q10 of Nmin vary among different ecosystems and regions at global scale. The results showed that Nmin varied significantly among different ecosystems with a global average of 2.41 mg kg 1 soil d 1. Furthermore, Nmin significantly decreased with increasing latitude and altitude. The Q10 varied significantly among different ecosystems with a global average of 2.21, ranging from the highest found in forest soils (2.43) and the lowest found for grassland soils (1.67) and significantly increased with increasing latitude. Path analyses indicated that Nmin was primarily affected by the content of soil organic carbon (C), soil C:N ratio, and clay content, while Q10 was primarily influenced by the soil C:N ratio and soil pH. Furthermore, the activation energy (Ea) of soil N mineralization was significantly and negative correlated with the substrate quality index among all ecosystems, which indicates the applicability of the carbon quality temperature (CQT) hypothesis to soil N mineralization at a global scale. These findings provide empirical evidence that under global warming scenarios soil N availability is expected to increase stronger in colder regions as compared with low latitude regions due to the higher Q10. This may alleviate the restriction of N supply for increased primary productivity at higher latitudes.
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DOI:10.1657/1938-4246-44.2.188URL [本文引用: 2]
Nitrification and denitrification are key microbiological processes in the soil nitrogen cycle and are the main biological sources of N 2 O emissions from soils. In this work, we measured gross nitrification and denitrification rates of northern Tibet alpine grassland ecosystems during the growing season and evaluated the influence of soil environmental factors. The results showed that the soil inorganic nitrogen concentration and gross nitrification and denitrification rates of both alpine meadow and alpine steppe varied obviously across the season. During the growing season mean values of gross nitrification and denitrification rates of the alpine meadow site were 3.0 and 2.3 times greater than those of the alpine steppe site, respectively. Both gross nitrification and denitrification rates were not significantly correlated with the determined soil characteristics which include soil microbial biomass, inorganic nitrogen, and soil temperature, except that gross nitrification seemed associated with the microsite where soil moisture was higher. Our results demonstrate that soil moisture can explain partly the higher soil nitrogen (N) transformation rates in alpine meadow sites, but soil N transformation microorganisms and enzyme activities studies covering prolonged observation periods are still needed to clarify the key soil environmental factors that control gross nitrification and denitrification processes in alpine grassland ecosystems.
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DOI:10.1111/oik.2009.118.issue-12URL [本文引用: 2]
DOI:10.1890/14-1761.1URLPMID:26405754 [本文引用: 1]
Abstract Plant species are important drivers of soil microbial communities. However, how plant functional traits are shaping these communities has received less attention though linking plant and microbial traits is crucial for better understanding plant-microbe interactions. Our objective was to determine how plant–microbe interactions were affected by plant traits. Specifically we analyzed how interactions between plant species and microbes involved in nitrogen cycling were affected by plant traits related to nitrogen nutrition in interaction with soil nitrogen availability. Eleven plant species, selected along an oligotrophic–nitrophilic gradient, were grown individually in a nitrogen-poor soil with two levels of nitrate availability. Plant traits for both carbon and nitrogen nutrition were measured and the genetic structure and abundance of rhizosphere microbial communities, in particular the ammonia oxidizer and nitrate reducer guilds, were analyzed. The structure of the bacterial community in the rhizosphere differed significantly between plant species and these differences depended on nitrogen availability. The results suggest that the rate of nitrogen uptake per unit of root biomass and per day is a key plant trait, explaining why the effect of nitrogen availability on the structure of the bacterial community depends on the plant species. We also showed that the abundance of nitrate reducing bacteria always decreased with increasing nitrogen uptake per unit of root biomass per day, indicating that there was competition for nitrate between plants and nitrate reducing bacteria. This study demonstrates that nitrate-reducing microorganisms may be adversely affected by plants with a high nitrogen uptake rate. Our work puts forward the role of traits related to nitrogen in plant–microbe interactions, whereas carbon is commonly considered as the main driver. It also suggests that plant traits related to ecophysiological processes, such as nitrogen uptake rates, are more relevant for understanding plant–microbe interactions than composite traits, such as nitrophily, which are related to a number of ecophysiological processes.
DOI:10.1016/j.soilbio.2016.06.011URL [本文引用: 1]
Urban wetlands potentially play an important role in nitrate (NO 3 61 ) removal from stormwater, but nitrogen loading from the atmosphere and surface water must intersect with soil properties optimal for NO 3 61 removal for this potential to be realized. We examined predictors of NO 3 61 removal via the microbial process of denitrification in an urban wetland system in New Jersey, USA with highly heterogeneous soils. Soil cores representing the wide range of soil textures at the site were collected to examine relationships between intact core denitrification rates, denitrification enzyme activity (DEA), available inorganic nitrogen, and soil water retention characteristics. Water retention curves were characterized for pressure potentials ranging from 611 to 615000cm and used to estimate pore size distribution parameters. The highest intact core denitrification rates occurred in soils located at low elevations, with high macroporosity, and low variability in soil pore radius. High DEA corresponded with high available soil NO 3 61 and high elevation. Soil samples collected at 118 points from the site and analyzed for soil organic matter and texture fractions were used to create interpolated raster layers of properties related to high denitrification rates (“hot spots”). Weighted estimations of whole-site NO 3 61 removal based on denitrification hot spots were higher than site estimations based on average denitrification rates, suggesting that studies using the latter approach may be underestimating NO 3 61 removal at the landscape level. Stormwater channels at the site intersected with denitrification hot spots over 20% of total channel area, indicating that soils may be at least partially reducing total NO 3 61 loads to the adjacent creek. These results show that soil physical properties that are relatively immutable can be used for predicting the location of potential hot spots of microbial activity at the landscape scale.
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DOI:10.1111/j.1438-8677.2009.00241.xURLPMID:19778364 [本文引用: 1]
Forest ecosystems with low soil nitrogen (N) availability are characterized by direct competition for this growth-limiting resource between several players, i.e. various components of vegetation, such as old-growth trees, natural regeneration and understorey species, mycorrhizal fungi, free-living fungi and bacteria. With the increase in frequency and intensity of extreme climate events predicted in current climate change scenarios, also competition for N between plants and/or soil microorganisms will be affected. In this review, we summarize the present understanding of ecosystem N cycling in N-limited forests and its interaction with extreme climate events, such as heat, drought and flooding. More specifically, the impacts of environmental stresses on microbial release and consumption of bioavailable N, N uptake and competition between plants, as well as plant and microbial uptake are presented. Furthermore, the consequences of drying wetting cycles on N cycling are discussed. Additionally, we highlight the current methodological difficulties that limit present understanding of N cycling in forest ecosystems and the need for interdisciplinary studies.
DOI:10.1657/1523-0430(2005)037[0118:TROSOM]2.0.CO;2URL [本文引用: 2]
Nitrogen availability is considered limiting for plant growth at the forest-tundra ecotone, and it might modulate ecosystem response to climate warming. The aim of this research was to compare the impact of climate, vegetation cover, and soil organic matter (SOM) chemistry on N mineralization rates at the forest-tundra ecotone. We therefore estimated N mineralization in mountain birch (Betula pubescens Ehrh. ssp. czerepanovii) forest and tundra soil across a broad-scale latitudinal gradient in Fennoscandia, which incorporated 4 research sites (Dovrefjell, Vassijaure, Abisko, and Joatka). During the summer period, ammonium was the dominant form of mineralized nitrogen in forest soils, while nitrate mineralization rates were higher at tundra sites during the winter. A negative regression relationship between an index of climatic continentality and N mineralization was found. Further, summer NH4+ mineralization rates increased with total N content in soils, while NO3- mineralization seemed to be associated with C availability. Our study showed markedly contrasting inorganic N release in forest and tundra soil, and that, although mineralization rates differed between the summer and winter period, the winter activity was relatively high and should not be ignored. We conclude that a shift in the forest-tundra ecotone in response to climate warming will have stronger effects on nitrogen availability at these sites than the direct effects of warming.
DOI:10.1007/s00792-006-0506-3URLPMID:16550305 [本文引用: 1]
Abstract Permafrost represents 26% of terrestrial soil ecosystems; yet its biology, essentially microbiology, remains relatively unexplored. The permafrost environment is considered extreme because indigenous microorganisms must survive prolonged exposure to subzero temperatures and background radiation for geological time scales in a habitat with low water activity and extremely low rates of nutrient and metabolite transfer. Yet considerable numbers and biodiversity of bacteria exist in permafrost, some of which may be among the most ancient viable life on Earth. This review describes the permafrost environment as a microbial habitat and reviews recent studies examining microbial biodiversity found in permafrost as well as microbial growth and activity at ambient in situ subzero temperatures. These investigations suggest that functional microbial ecosystems exist within the permafrost environment and may have important implications on global biogeochemical processes as well as the search for past or extant life in permafrost presumably present on Mars and other bodies in our solar system.
DOI:10.1016/j.soilbio.2014.03.022URL [本文引用: 3]
Warming generally accelerates the decomposition of plant litter. However, changes in precipitation could alter the sensitivity of litter decomposition to warming, thereby affecting the formation of litter-derived soil organic matter. As grassland soils store 6520% of Earth's soil carbon, understanding the effect of climatic changes on the decomposition dynamics of grasses is important. However, little is known about how projected changes in climate would affect litter microbial communities and enzyme activities, and the consequences of these changes for the mass loss and compound-specific degradation of grass litter that possess complex lignocellulosic chemistry. Over a period of two years, using litter of the grass Poa trivialis , we studied how mass loss, microbial enzyme activity and fine-level litter chemistry responded to a factorial combination of 4 levels of warming (up to ambient+654°C) and three levels of precipitation [ambient, wet (+50%) and dry (6150%)] at the Boston-Area Climate Experiment (BACE), in Massachusetts, USA. After 393 days of decomposition, supplemental precipitation accelerated mass loss compared to the dry treatment, as a consequence of faster loss of hydroxycinnamates, which protect carbohydrates through cross-linkages with lignins. Only a third as much of the cell wall-bound ferulic and p -coumaric acids remained in litter from the supplemental precipitation treatment compared to the ambient controls. In contrast, the warming treatments did not affect mass loss until later, after 740 days, when the litter in the warmest treatment (+654°C) had lost the most mass. Although warming significantly affected mass loss after 740 days, there was also a trend in the warmest treatments toward greater mass loss in the wet (78% mass loss) and ambient (68%) plots compared to dry plots (61%), possibly due to the higher activity of β-glucosidase. Though mass loss at this final time point varied with both warming and precipitation treatments, the compound-specific degradation of litter captured by diffuse reflectance infra-red Fourier transform (DRIFT) and 13 C Nuclear Magnetic Resonance (NMR) spectroscopy revealed that only the precipitation treatments significantly altered the chemistry of carbon compounds in the decomposed tissue. Litter that decomposed in the dry treatment had a higher proportion of carbohydrates remaining than litter in the wet and ambient treatments. Similarly, although ergosterol content and potential activity of phenol oxidase decreased in the warmer treatments, the consequences of this response were not observed in the degradation of specific compounds in litter, which varied only with precipitation treatments. Our results suggests that mass loss and enzyme activities may not accurately capture the complexity of compound-specific degradation of litter during decomposition. Our results also identified non-linear responses of β-glucosidase and N-acetyl-β-D-glucosaminidase (NAG) activities to warming. These results thus emphasize the complexities of litter decomposition and suggest that similar changes in decomposition across other grass species could alter the carbon budget of grasslands.
DOI:10.1111/ejss.12414URL [本文引用: 1]
Abstract To explain the effects of short-term N addition on plant biomass allocation and on carbon (C) and nitrogen (N) pools in an alpine scrub ecosystem, we carried out a field experiment in Sibiraea angustata scrubland on the eastern margin of the Qinghai-Tibetan Plateau of China. After one and a half years of N addition at four rates (N0, control; N20, 20; N50, 50; N100, 100 kg N ha611 year611), we investigated the amount and allocation of biomass and the C and N pools in several parts of the ecosystem, including shrubs (leaves, shoots and branches, coarse roots and fine roots), grass (above- and below-ground) and litter (wood and leaf debris) components, and seven depth intervals within the soil (0–5, 5–10, 10–20, 20–30, 30–50, 50–70 and 70–100 cm). The results were as follows: (i) total vegetation biomass showed a linear increase with the increase in N (P < 0.05), mainly from the increased root biomass in both shrubs and grasses, (ii) the ecosystem C and N storage were 36 and 3.26 kg m612, respectively, of which the shrub, grass, litter and soil components contributed 11.08, 0.47, 0.25 and 88%, respectively, to the C pool and 3.07, 0.16, 0.08 and 97%, respectively, to the N pool, (iii) the ecosystem N pool did not change in response to the addition of N, whereas the ecosystem C pool responded linearly to increasing N (P < 0.05). These results suggest that the alpine scrub ecosystem functions as a net C sink under increasing atmospheric N deposition, mainly by promoting belowground C sequestration. Effects of short-term N addition on biomass allocation and C and N pools in alpine scrub. Response to N addition in C pool of components of the ecosystem and soil at depth (0–100 cm). Root:shoot ratio of vegetation and ecosystem C pool increased linearly with increasing N. Alpine scrub ecosystem may function as a net C sink under increasing atmospheric N deposition.
DOI:10.4141/cjss95-048URL [本文引用: 1]
After 8 wk of incubation, the amounts of soluble organic carbon leached by 0.001 M CaCl2 solution from flooded soils ranged from 153 to 630 mg C kg-1. In contrast, only 28-107 mg C kg-1 was leached from nonflooded soils. The amounts of soluble organic nitrogen leached from the flooded soils ranged from 10 to 30 mg N kg-1 compared with 5.9-12 mg N kg-1 from nonflooded soils. In the flooded soils, ammonium nitrogen dominated the total inorganic nitrogen leached (99.5-99.9%) whereas in nonflooded soils leachable N was mainly nitrate and nitrite (97.4-99.9%). Methane was emitted from the flooded soils (10-138 mg C kg-1 over 8 wk). The rate of carbon dioxide evolution in flooded soils increased linearly with time and total evolution ranged from 72 to 552 mg C kg-1, whereas CO2 evolution in the nonflooded soils was steady with total evolution ranging from 159 to 1279 mg C kg-1 after 8 wk. -from Authors
[本文引用: 1]
[本文引用: 1]
URL [本文引用: 1]
在高海拔地区，较短的生长季和较低的温度是限制植物生命活动最重要的因子。高山生态系统中严重匮乏的土壤有效氮限制了植物的生长发育，植物如何更好地适应随着海拔增加的极端气候环境，以及高山草地生态系统中氮的有效利用如何实现亟需研究。高山植物在较宽的温度范围内维持新陈代谢并且积极生长，在较短的周期内完成营养生长和生殖生长，且具有较高的物种丰富度，并在季节明显的高山地带具有适应气候条件的节律性变化，而丰富多变的植物物候期与生活史对策有关。土壤中不同化学形态的氮素为植物生长发育过程中的养分利用提供了多元选择。植物物候格局...
URL [本文引用: 1]
在高海拔地区，较短的生长季和较低的温度是限制植物生命活动最重要的因子。高山生态系统中严重匮乏的土壤有效氮限制了植物的生长发育，植物如何更好地适应随着海拔增加的极端气候环境，以及高山草地生态系统中氮的有效利用如何实现亟需研究。高山植物在较宽的温度范围内维持新陈代谢并且积极生长，在较短的周期内完成营养生长和生殖生长，且具有较高的物种丰富度，并在季节明显的高山地带具有适应气候条件的节律性变化，而丰富多变的植物物候期与生活史对策有关。土壤中不同化学形态的氮素为植物生长发育过程中的养分利用提供了多元选择。植物物候格局...
DOI:10.1007/s11430-012-4461-9URL
We studied the uptake of ammonium,nitrate,and a variety of amino acids by alpine plant species in the Kobresia humilis alpine meadow ecosystem in situ.We examined the extent of niche separation in uptake of N source by different plant species in alpine communities,and investigated the contribution of symbiotically fixed N to the total N in alpine meadow.The results are(1) δ 15 N natural abundance values of 13 plant species lie between 2.680‰ and 5.169‰,and the scope is 7.849‰.(2) Leguminous plants,such as Trigonella ruthenica,Gueldenstaedtia diversiffolia,and Oxytyopis ochrocephala,and non-leguminous plant Gentiana straminea uptake low amounts of 15 N labeled ammonium,nitrate,glycine or aspartate in soil.(3) As far as the plant uptake of organic N is concerned,Kobresia humilis,Poa pratensis,and Gentiuna spathutifolta can effectively uptake organic nitrogen,and about 37%-40% of the nitrogen of these species comes from soil organic nitrogen sources(such as glycine and aspartate).Stipa aliena can effectively uptake nitrate,and 60% of its nitrogen comes from soil nitrate.Potentilla anserina,Poa pratensis,and Thalictrum alpinum can effectively absorb ammonium in comparason to other plant species in the meadow,and about 25%-27% of the nitrogen in these plants comes from soil ammonium.(4) The contribution of leguminous fixed N to total N is 7.48%-9.26% in Kobresia humilis alpine meadow.(5) These data show many plant species of alpine meadow may effectively utilize dissolved organic nitrogen such as amino acids,and these plants have diverse ways to uptake soil nitrogen in alpine meadows.Based on the results we can partly explain why there are abundant biodiversities and how plants at alpine habitat utilize the limited soil N sources.
DOI:10.13209/j.0479-8023.2016.061URL [本文引用: 2]
基于海北站野外长期增温和降水改变控制平台,研究高寒草甸生态系统生长季土壤无机氮对增温和降水改变的响应.结果表明,增温使铵态氮降低47.5％(p=0.001),硝态氮降低46.1％(p=0.021).降水的改变对无机氮的影响存在不对称性,增加降水使铵态氮增加74.7％(p=0.046),硝态氮增加154％(p=0.017);减少降水使铵态氮降低,对硝态氮无显著影响.铵态氮、硝态氮随着土壤湿度的增加而增加,与土壤温度无显著关系.这表明增温和降水改变主要通过改变土壤湿度而不是土壤温度影响生长季土壤无机氮.因此预测,未来气候变化背景下,土壤湿度的增加可能导致青藏高原高寒草甸土壤无机氮的可利用性增加.
DOI:10.13209/j.0479-8023.2016.061URL [本文引用: 2]
基于海北站野外长期增温和降水改变控制平台,研究高寒草甸生态系统生长季土壤无机氮对增温和降水改变的响应.结果表明,增温使铵态氮降低47.5％(p=0.001),硝态氮降低46.1％(p=0.021).降水的改变对无机氮的影响存在不对称性,增加降水使铵态氮增加74.7％(p=0.046),硝态氮增加154％(p=0.017);减少降水使铵态氮降低,对硝态氮无显著影响.铵态氮、硝态氮随着土壤湿度的增加而增加,与土壤温度无显著关系.这表明增温和降水改变主要通过改变土壤湿度而不是土壤温度影响生长季土壤无机氮.因此预测,未来气候变化背景下,土壤湿度的增加可能导致青藏高原高寒草甸土壤无机氮的可利用性增加.
DOI:10.3321/j.issn:1672-9072.1998.09.015URL [本文引用: 1]
窄叶鲜卑花灌丛是青藏高原东缘高山灌丛中特有的、具代表性的类型。选择该群落的典型分布区域，运用数值分类法，将窄叶鲜卑花群系分为４个群丛组、１０个群丛类型。用ＰＣＡ排序技术定量分析了各类型在空间地理上的分布格局，以及与环境因子之间的关系。结果表明：各类型的分布主要取决于环境中土壤条件（主要是土壤水分和土壤有机质含量）和热量条件的垂直梯度变化，而群落的分类等级越低，对环境因子的变化越敏感。生物量的研究表
DOI:10.3321/j.issn:1672-9072.1998.09.015URL [本文引用: 1]
窄叶鲜卑花灌丛是青藏高原东缘高山灌丛中特有的、具代表性的类型。选择该群落的典型分布区域，运用数值分类法，将窄叶鲜卑花群系分为４个群丛组、１０个群丛类型。用ＰＣＡ排序技术定量分析了各类型在空间地理上的分布格局，以及与环境因子之间的关系。结果表明：各类型的分布主要取决于环境中土壤条件（主要是土壤水分和土壤有机质含量）和热量条件的垂直梯度变化，而群落的分类等级越低，对环境因子的变化越敏感。生物量的研究表
DOI:10.1016/j.apsoil.2016.01.011URL [本文引用: 1]
DOI:10.1016/j.apsoil.2010.07.005URL [本文引用: 1]
In order to understand the effects of projected global warming on soils in different land-use types, we compared the impacts of warming on soils in two contrasting forest ecosystems (a dragon spruce plantation and a natural forest) using the open-top chamber (OTC) method in the Eastern Tibetan Plateau of China. The OTC on average enhanced daily mean soil temperatures by 0.61 C (plantation) and by 0.55 C (natural forest) throughout the growing season, respectively. Conversely, soil volumetric moisture declined by 4.10% in the plantation and by 2.55% in the natural forest, respectively. Warming did not affect dissolved organic C (DOC) and N (DON) in the plantation but significantly increased them in the natural forest. Elevated temperature significantly increased net N mineralization rates and extractable inorganic N pools in both sites. Warming had no effects on microbial biomass C (MBC) and N (MBN) and their ratios (MBC/MBN) in the plantation and significantly increased MBC and MBN only late in the growing season in the natural forest. Warming did not affect basal respiration in the plantation but significantly increased it in the natural forest. No clear change was observed in metabolic quotient between warming regimes for both forest types. Experimental warming tended to increase invertase and urease in both forest soils. Measured pools related to N turnover generally showed significant interactions in warming, forest type and sampling date. Taken together, our results indicate that responses of soils to experimental warming depend strongly on forest managements and seasons.
URL [本文引用: 3]
采取定性与定量相结合的方法，评价了岷江上游典型植物群落的稳定性。将植被盖度、多样性、复杂性、演替度等反映植被稳定性的数量特征指标结合气候、地形、土壤等外部环境因子建立评价体系，利用层次分析法确定指标权重，利用综合指数法计算群落稳定性。结果表明：源区植物群落中，云杉林、柳灌丛、窄叶鲜卑花灌丛、冷杉林、绣线菊灌丛有较高的稳定性值，沙棘和小果小檗灌丛稳定性值较低；草甸群落中，苔草草甸和白茅草草甸具有较高的稳定性值，蒿草草甸和高山草甸稳定性值较低。干旱河谷植物群落中，绣线菊灌丛、瑞香灌丛、小花滇紫草灌丛、小马鞍羊蹄甲-白刺花灌丛、莸灌丛有较高的稳定性值，西南野丁香灌丛、驼绒藜灌丛、川甘亚菊灌丛的稳定性值较低。
URL [本文引用: 3]
采取定性与定量相结合的方法，评价了岷江上游典型植物群落的稳定性。将植被盖度、多样性、复杂性、演替度等反映植被稳定性的数量特征指标结合气候、地形、土壤等外部环境因子建立评价体系，利用层次分析法确定指标权重，利用综合指数法计算群落稳定性。结果表明：源区植物群落中，云杉林、柳灌丛、窄叶鲜卑花灌丛、冷杉林、绣线菊灌丛有较高的稳定性值，沙棘和小果小檗灌丛稳定性值较低；草甸群落中，苔草草甸和白茅草草甸具有较高的稳定性值，蒿草草甸和高山草甸稳定性值较低。干旱河谷植物群落中，绣线菊灌丛、瑞香灌丛、小花滇紫草灌丛、小马鞍羊蹄甲-白刺花灌丛、莸灌丛有较高的稳定性值，西南野丁香灌丛、驼绒藜灌丛、川甘亚菊灌丛的稳定性值较低。
DOI:10.1111/gcb.12161URLPMID:23504744 [本文引用: 3]
Despite the perceived importance of exudation to forest ecosystem function, few studies have attempted to examine the effects of elevated temperature and nutrition availability on the rates of root exudation and associated microbial processes. In this study, we performed an experiment in which in situ exudates were collected from Picea asperata seedlings that were transplanted in disturbed soils exposed to two levels of temperature (ambient temperature and infrared heater warming) and two nitrogen levels (unfertilized and 25 g N m612 a611). Here, we show that the trees exposed to an elevated temperature increased their exudation rates I (μg C g611 root biomass h611), II (μg C cm611 root length h611) and III (μg C cm612 root area h611) in the unfertilized plots. The altered morphological and physiological traits of the roots exposed to experimental warming could be responsible for this variation in root exudation. Moreover, these increases in root-derived C were positively correlated with the microbial release of extracellular enzymes involved in the breakdown of organic N (R2 = 0.790; P = 0.038), which was coupled with stimulated microbial activity and accelerated N transformations in the unfertilized soils. In contrast, the trees exposed to both experimental warming and N fertilization did not show increased exudation rates or soil enzyme activity, indicating that the stimulatory effects of experimental warming on root exudation depend on soil fertility. Collectively, our results provide preliminary evidence that an increase in the release of root exudates into the soil may be an important physiological adjustment by which the sustained growth responses of plants to experimental warming may be maintained via enhanced soil microbial activity and soil N transformation. Accordingly, the underlying mechanisms by which plant root-microbe interactions influence soil organic matter decomposition and N cycling should be incorporated into climate-carbon cycle models to determine reliable estimates of long-term C storage in forests.
DOI:10.11707/j.1001-7488.20140701URLMagsci
采用封顶埋管原位培养法研究川西亚高山不同海拔3种森林群落（岷江冷杉原始林A、针阔混交林B和珉江冷杉次生林C）土壤氮转化的季节动态特征。结果表明：3种森林群落的土壤净氨化速率、净硝化速率、净氮矿化速率和净氮固持速率都存在明显的季节动态；在非生长季，3种森林群落的净硝化速率、净氮矿化速率和净氮固持速率都为正值，而净氨化速率极低且为负值；各时期土壤氮矿化过程以土壤硝化作用为主，且土壤净硝化速率与净氮矿化速率季节动态趋势一致；土壤净氮矿化速率在生长季初期最低，在生长季中期达全年最高峰；不同海拔之间土壤净氨化速率差异显著（<em>P</em><0.05）；B海拔的土壤净硝化速率和净氮矿化速率低于其他2个海拔，但差异未达到显著水平；非生长季氮素固持作用最强。
DOI:10.11707/j.1001-7488.20140701URLMagsci
采用封顶埋管原位培养法研究川西亚高山不同海拔3种森林群落（岷江冷杉原始林A、针阔混交林B和珉江冷杉次生林C）土壤氮转化的季节动态特征。结果表明：3种森林群落的土壤净氨化速率、净硝化速率、净氮矿化速率和净氮固持速率都存在明显的季节动态；在非生长季，3种森林群落的净硝化速率、净氮矿化速率和净氮固持速率都为正值，而净氨化速率极低且为负值；各时期土壤氮矿化过程以土壤硝化作用为主，且土壤净硝化速率与净氮矿化速率季节动态趋势一致；土壤净氮矿化速率在生长季初期最低，在生长季中期达全年最高峰；不同海拔之间土壤净氨化速率差异显著（<em>P</em><0.05）；B海拔的土壤净硝化速率和净氮矿化速率低于其他2个海拔，但差异未达到显著水平；非生长季氮素固持作用最强。
Nitrogen mineralization peaks under closed canopy during the natural forest development cycle of an old-growth temperate spruce forest
1
2015
... id="C6">然而, 目前对土壤氮动态的研究主要集中在森林、草地和农田生态系统, 且主要关注土壤氮矿化过程(
Nitrogen source impact on the spatial variability of organic carbon and nitrogen in soil
1
1996
... id="C4">在高寒生物区(高海拔、高纬度地区), 氮作为植被生长发育所必需的营养元素, 同时也是其最主要的限制因子(
A meta-analysis of experimental warming effects on terrestrial nitrogen pools and dynamics
2
2013
... id="C31">土壤硝态氮和铵态氮含量对OTC增温的响应因季节和植物处理的不同而存在显著差异(
... ), 土壤受到严重的水分限制, 从而抵消了增温对微生物氮矿化的正效应(
Labile, recalcitrant, and microbial carbon and nitrogen pools of a tallgrass prairie soil in the US Great Plains subjected to experimental warming and clipping
1
2009
... id="C30">硝态氮和铵态氮是陆地生态系统土壤活性氮库的最主要组成部分, 同时也是陆地生态系统土壤氮循环最重要和最活跃的部分(
Manipulating snow cover in an alpine bog: Effects on ecosystem respiration and nutrient content in soil and microbes
1
2012
... id="C5">高寒生态系统已成为响应全球气候变暖最敏感的一个区域.高寒地区土壤生物活动和酶活性长期受低温限制, 导致土壤有机质大量积累, 土壤氮矿化速率缓慢, 土壤氮被固定在较为稳定的有机质中(
Long-term reactive nitrogen loading alters soil carbon and microbial community properties in a subalpine forest ecosystem
1
2016
... id="C5">高寒生态系统已成为响应全球气候变暖最敏感的一个区域.高寒地区土壤生物活动和酶活性长期受低温限制, 导致土壤有机质大量积累, 土壤氮矿化速率缓慢, 土壤氮被固定在较为稳定的有机质中(
Linking carbon and nitrogen mineralization with microbial responses to substrate availability—The DECONIT model
1
2010
... id="C31">土壤硝态氮和铵态氮含量对OTC增温的响应因季节和植物处理的不同而存在显著差异(
Spatio-?temporal variability of farmland soil organic matter and total nitrogen in the southern Loess Plateau, China: A case study in Heyang County
1
2016
... id="C6">然而, 目前对土壤氮动态的研究主要集中在森林、草地和农田生态系统, 且主要关注土壤氮矿化过程(
Nitrogen mineralization and phenol accumulation along a fire chronosequence in northern Sweden
1
2002
... id="C4">在高寒生物区(高海拔、高纬度地区), 氮作为植被生长发育所必需的营养元素, 同时也是其最主要的限制因子(
土壤中的氮对温带森林植物-微生物竞争氮素的影响
1
2015
... id="C8">此外, 近年来高强度的人类活动(如过度放牧、砍伐等)正在加速改变该区域灌丛植被覆盖度.植被覆盖度的改变不仅会导致土壤微环境条件的改变, 而且将打破长期以来植物与土壤微生物之间对无机氮的竞争关系(
土壤中的氮对温带森林植物-微生物竞争氮素的影响
1
2015
... id="C8">此外, 近年来高强度的人类活动(如过度放牧、砍伐等)正在加速改变该区域灌丛植被覆盖度.植被覆盖度的改变不仅会导致土壤微环境条件的改变, 而且将打破长期以来植物与土壤微生物之间对无机氮的竞争关系(
氮素富集对青藏高原东缘窄叶鲜卑花灌丛根系分泌物碳输入的影响
1
2017
... id="C7">高寒灌丛是青藏高原东缘第二大植被类型, 在区域生态系统碳氮平衡中起着极为重要的作用(
氮素富集对青藏高原东缘窄叶鲜卑花灌丛根系分泌物碳输入的影响
1
2017
... id="C7">高寒灌丛是青藏高原东缘第二大植被类型, 在区域生态系统碳氮平衡中起着极为重要的作用(
雪被厚度和积雪周期对土壤氮素动态影响的初步研究
1
2014
... id="C5">高寒生态系统已成为响应全球气候变暖最敏感的一个区域.高寒地区土壤生物活动和酶活性长期受低温限制, 导致土壤有机质大量积累, 土壤氮矿化速率缓慢, 土壤氮被固定在较为稳定的有机质中(
雪被厚度和积雪周期对土壤氮素动态影响的初步研究
1
2014
... id="C5">高寒生态系统已成为响应全球气候变暖最敏感的一个区域.高寒地区土壤生物活动和酶活性长期受低温限制, 导致土壤有机质大量积累, 土壤氮矿化速率缓慢, 土壤氮被固定在较为稳定的有机质中(
The non-?additive effects of temperature and nitrogen deposition on CO2 emissions, nitrification, and nitrogen mineralization in soils mixed with termite nests
1
2017
... id="C31">土壤硝态氮和铵态氮含量对OTC增温的响应因季节和植物处理的不同而存在显著差异(
2
2013
... id="C5">高寒生态系统已成为响应全球气候变暖最敏感的一个区域.高寒地区土壤生物活动和酶活性长期受低温限制, 导致土壤有机质大量积累, 土壤氮矿化速率缓慢, 土壤氮被固定在较为稳定的有机质中(
... id="C32">植物处理方式对土壤硝态氮和铵态氮含量的影响也不一致.与土壤铵态氮含量相比, 土壤硝态氮含量受植物生长的影响更大(
Roots nitrogen transformations, and ecosystem services
1
2008
... id="C4">在高寒生物区(高海拔、高纬度地区), 氮作为植被生长发育所必需的营养元素, 同时也是其最主要的限制因子(
Alpine Plant Life: Functional Plant Ecology of High Mountain Ecosystems.
1
2003
... id="C7">高寒灌丛是青藏高原东缘第二大植被类型, 在区域生态系统碳氮平衡中起着极为重要的作用(
施氮对青藏高原东缘窄叶鲜卑花灌丛土壤呼吸的影响
1
2014
... id="C30">硝态氮和铵态氮是陆地生态系统土壤活性氮库的最主要组成部分, 同时也是陆地生态系统土壤氮循环最重要和最活跃的部分(
施氮对青藏高原东缘窄叶鲜卑花灌丛土壤呼吸的影响
1
2014
... id="C30">硝态氮和铵态氮是陆地生态系统土壤活性氮库的最主要组成部分, 同时也是陆地生态系统土壤氮循环最重要和最活跃的部分(
A global synthesis of the rate and temperature sensitivity of soil nitrogen mineralization: Latitudinal patterns and mechanisms
1
2016
... id="C16">其中, 硝态氮含量采用紫外比色法测定, 土壤铵态氮含量采用靛酚蓝比色法测定(
1
2000
... id="C30">硝态氮和铵态氮是陆地生态系统土壤活性氮库的最主要组成部分, 同时也是陆地生态系统土壤氮循环最重要和最活跃的部分(
1
2000
... id="C30">硝态氮和铵态氮是陆地生态系统土壤活性氮库的最主要组成部分, 同时也是陆地生态系统土壤氮循环最重要和最活跃的部分(
Gross nitrification and denitrification in alpine grassland ecosystems on the Tibetan Plateau
2
2015
... id="C4">在高寒生物区(高海拔、高纬度地区), 氮作为植被生长发育所必需的营养元素, 同时也是其最主要的限制因子(
... id="C8">此外, 近年来高强度的人类活动(如过度放牧、砍伐等)正在加速改变该区域灌丛植被覆盖度.植被覆盖度的改变不仅会导致土壤微环境条件的改变, 而且将打破长期以来植物与土壤微生物之间对无机氮的竞争关系(
陆地生态系统植物的氮源及氮素吸收
2
2007
... id="C6">然而, 目前对土壤氮动态的研究主要集中在森林、草地和农田生态系统, 且主要关注土壤氮矿化过程(
... id="C8">此外, 近年来高强度的人类活动(如过度放牧、砍伐等)正在加速改变该区域灌丛植被覆盖度.植被覆盖度的改变不仅会导致土壤微环境条件的改变, 而且将打破长期以来植物与土壤微生物之间对无机氮的竞争关系(
陆地生态系统植物的氮源及氮素吸收
2
2007
... id="C6">然而, 目前对土壤氮动态的研究主要集中在森林、草地和农田生态系统, 且主要关注土壤氮矿化过程(
... id="C8">此外, 近年来高强度的人类活动(如过度放牧、砍伐等)正在加速改变该区域灌丛植被覆盖度.植被覆盖度的改变不仅会导致土壤微环境条件的改变, 而且将打破长期以来植物与土壤微生物之间对无机氮的竞争关系(
Plant-microbial competition for nitrogen uncoupled from soil C:N ratios
2
2009
... id="C32">植物处理方式对土壤硝态氮和铵态氮含量的影响也不一致.与土壤铵态氮含量相比, 土壤硝态氮含量受植物生长的影响更大(
... ); 此时期植物处于生长季末期, 对土壤氮的吸收速率减弱, 有利于土壤硝态氮的积累(
Plant traits related to nitrogen uptake influence plant-microbe competition
1
2015
... id="C30">硝态氮和铵态氮是陆地生态系统土壤活性氮库的最主要组成部分, 同时也是陆地生态系统土壤氮循环最重要和最活跃的部分(
Soil texture and water retention as spatial predictors of denitrification in urban wetlands
1
2016
... id="C4">在高寒生物区(高海拔、高纬度地区), 氮作为植被生长发育所必需的营养元素, 同时也是其最主要的限制因子(
Understanding the soil nitrogen cycle
1
1993
... id="C30">硝态氮和铵态氮是陆地生态系统土壤活性氮库的最主要组成部分, 同时也是陆地生态系统土壤氮循环最重要和最活跃的部分(
Nitrogen balance in forest soils: Nutritional limitation of plants under climate change stresses
1
2009
... id="C6">然而, 目前对土壤氮动态的研究主要集中在森林、草地和农田生态系统, 且主要关注土壤氮矿化过程(
The role of soil organic matter quality and physical environment for nitrogen mineralization at the forest-tundra ecotone in Fennoscandia
2
2015
... id="C30">硝态氮和铵态氮是陆地生态系统土壤活性氮库的最主要组成部分, 同时也是陆地生态系统土壤氮循环最重要和最活跃的部分(
... id="C31">土壤硝态氮和铵态氮含量对OTC增温的响应因季节和植物处理的不同而存在显著差异(
Microbial ecology and biodiversity in permafrost
1
2006
... id="C30">硝态氮和铵态氮是陆地生态系统土壤活性氮库的最主要组成部分, 同时也是陆地生态系统土壤氮循环最重要和最活跃的部分(
Warming alters potential enzyme activity but precipitation regulates chemical transformations in grass litter exposed to simulated climatic changes
3
2014
... id="C6">然而, 目前对土壤氮动态的研究主要集中在森林、草地和农田生态系统, 且主要关注土壤氮矿化过程(
... id="C7">高寒灌丛是青藏高原东缘第二大植被类型, 在区域生态系统碳氮平衡中起着极为重要的作用(
... )、植物生物量分配和生态系统碳氮库(
Effects of short-term N addition on plant biomass allocation and C and N pools of the Sibiraea angustata scrub ecosystem
1
2017
... id="C4">在高寒生物区(高海拔、高纬度地区), 氮作为植被生长发育所必需的营养元素, 同时也是其最主要的限制因子(
Carbon and nitrogen losses from undisturbed soil columns under short-term flooding conditions
1
1995
... id="C30">硝态氮和铵态氮是陆地生态系统土壤活性氮库的最主要组成部分, 同时也是陆地生态系统土壤氮循环最重要和最活跃的部分(
土壤温度, 水分和NH4 +-N浓度对土壤硝化反应速度及N2O排放的影响
1
2010
... id="C32">植物处理方式对土壤硝态氮和铵态氮含量的影响也不一致.与土壤铵态氮含量相比, 土壤硝态氮含量受植物生长的影响更大(
土壤温度, 水分和NH4 +-N浓度对土壤硝化反应速度及N2O排放的影响
1
2010
... id="C32">植物处理方式对土壤硝态氮和铵态氮含量的影响也不一致.与土壤铵态氮含量相比, 土壤硝态氮含量受植物生长的影响更大(
植物物候分化格局对维持高山草地植物氮素利用及其动态平衡的适应性贡献
1
2013
... id="C30">硝态氮和铵态氮是陆地生态系统土壤活性氮库的最主要组成部分, 同时也是陆地生态系统土壤氮循环最重要和最活跃的部分(
植物物候分化格局对维持高山草地植物氮素利用及其动态平衡的适应性贡献
1
2013
... id="C30">硝态氮和铵态氮是陆地生态系统土壤活性氮库的最主要组成部分, 同时也是陆地生态系统土壤氮循环最重要和最活跃的部分(
The uptake diversity of soil nitrogen nutrients by main plant species in Kobresia humilis alpine meadow on the Qinghai-Tibet Plateau.
2012
青藏高原高寒草甸土壤无机氮对增温和降水改变的响应
2
2016
... id="C6">然而, 目前对土壤氮动态的研究主要集中在森林、草地和农田生态系统, 且主要关注土壤氮矿化过程(
... id="C7">高寒灌丛是青藏高原东缘第二大植被类型, 在区域生态系统碳氮平衡中起着极为重要的作用(
青藏高原高寒草甸土壤无机氮对增温和降水改变的响应
2
2016
... id="C6">然而, 目前对土壤氮动态的研究主要集中在森林、草地和农田生态系统, 且主要关注土壤氮矿化过程(
... id="C7">高寒灌丛是青藏高原东缘第二大植被类型, 在区域生态系统碳氮平衡中起着极为重要的作用(
川西北窄叶鲜卑花灌丛的类型和生物量及其与环境因子的关系
1
1998
... id="C5">高寒生态系统已成为响应全球气候变暖最敏感的一个区域.高寒地区土壤生物活动和酶活性长期受低温限制, 导致土壤有机质大量积累, 土壤氮矿化速率缓慢, 土壤氮被固定在较为稳定的有机质中(
川西北窄叶鲜卑花灌丛的类型和生物量及其与环境因子的关系
1
1998
... id="C5">高寒生态系统已成为响应全球气候变暖最敏感的一个区域.高寒地区土壤生物活动和酶活性长期受低温限制, 导致土壤有机质大量积累, 土壤氮矿化速率缓慢, 土壤氮被固定在较为稳定的有机质中(
Warming and nitrogen deposition are interactive in shaping surface soil microbial communities near the alpine timberline zone on the eastern Qinghai-Tibet Plateau, southwestern China
1
2016
... id="C31">土壤硝态氮和铵态氮含量对OTC增温的响应因季节和植物处理的不同而存在显著差异(
Initial soil responses to experimental warming in two constrasting forest ecosystem, Eastern Tibetan Plateau, China: Nutrient availabilities, microbial properoties and enzyme activities
1
2010
... id="C7">高寒灌丛是青藏高原东缘第二大植被类型, 在区域生态系统碳氮平衡中起着极为重要的作用(
岷江上游植物群落稳定性研究
3
2009
... id="C8">此外, 近年来高强度的人类活动(如过度放牧、砍伐等)正在加速改变该区域灌丛植被覆盖度.植被覆盖度的改变不仅会导致土壤微环境条件的改变, 而且将打破长期以来植物与土壤微生物之间对无机氮的竞争关系(
... id="C31">土壤硝态氮和铵态氮含量对OTC增温的响应因季节和植物处理的不同而存在显著差异(
... id="C32">植物处理方式对土壤硝态氮和铵态氮含量的影响也不一致.与土壤铵态氮含量相比, 土壤硝态氮含量受植物生长的影响更大(
岷江上游植物群落稳定性研究
3
2009
... id="C8">此外, 近年来高强度的人类活动(如过度放牧、砍伐等)正在加速改变该区域灌丛植被覆盖度.植被覆盖度的改变不仅会导致土壤微环境条件的改变, 而且将打破长期以来植物与土壤微生物之间对无机氮的竞争关系(
... id="C31">土壤硝态氮和铵态氮含量对OTC增温的响应因季节和植物处理的不同而存在显著差异(
... id="C32">植物处理方式对土壤硝态氮和铵态氮含量的影响也不一致.与土壤铵态氮含量相比, 土壤硝态氮含量受植物生长的影响更大(
Enhanced root exudation stimulates soil nitrogen transformations in a subalpine coniferous forest under experimental warming
3
2013
... id="C30">硝态氮和铵态氮是陆地生态系统土壤活性氮库的最主要组成部分, 同时也是陆地生态系统土壤氮循环最重要和最活跃的部分(
... ).生长季初期各处理下土壤硝态氮含量较低的原因可能是此时期土壤氮矿化速率较低, 非生长季末期冰雪融化也可能造成大量硝态氮淋溶损失(
... ;
川西亚高山不同海拔3种森林群落土壤氮转化的季节动态
2014
川西亚高山不同海拔3种森林群落土壤氮转化的季节动态
2014
