,1,*, 史亚博1, 梁茂伟1, 刘钟龄1Temporal changes in precipitation altered aboveground biomass in a typical steppe in Nei Mongol, China
Bai-Ling MIAO1,2, Cun-Zhu LIANG,1,*, Ya-Bo SHI1, Mao-Wei LIANG1, Zhong-Ling LIU1通讯作者: *bilcz@imu.edu.cn
编委: 唐志尧
责任编辑: 李敏, 赵航(实习)
收稿日期:2018-09-18接受日期:2019-06-21网络出版日期:2019-07-20
| 基金资助: |
Received:2018-09-18Accepted:2019-06-21Online:2019-07-20
| Fund supported: |
摘要
降水格局的变化是气候变化影响干旱和半干旱区草原植物群落结构和功能的关键过程。作为植物群落结构和功能的基本组成单位——植物功能群——对气候变化的响应差异明显。有关不同植物功能群如何响应降水格局的研究, 有助于揭示气候变化对干旱与半干旱区生态系统关键功能与过程稳定性的变异机制。该文利用1982-2015年的典型草原群落地上生物量长期动态监测数据及其所对应的气候数据, 系统揭示降水变化对干旱与半干旱区生态系统生产力的影响。主要研究结果如下: 1) 1982-2015年内蒙古典型草原区降水变化特征明显, 主要表现在降水集中度呈显著的降低趋势; 小降水事件(≤5 mm)明显增多。2)降水变化导致群落生物量呈下降趋势。其中, 多年生丛生禾草的生物量呈上升趋势; 一二年生植物、多年生杂类草、多年生根茎禾类草的生物量均呈下降趋势。3)群落生物量与生长季降水量、降水集中度呈显著的正相关关系。各功能群中, 多年生杂类草、半灌木和生长季降水量呈显著正相关关系, 灌木与降水集中度呈显著负相关关系。4)群落生物量与各等级降水的频率相关性均不显著, 但与I-II类(0.1-10 mm)降水贡献率显著负相关。各功能群中, 多年生杂类草与I类降水(0.1-5.0 mm)的发生频率和降水贡献率均呈显著的负相关关系, 与VI类降水(20-25 mm)的发生频率和贡献率均呈显著的正相关关系。多年生根茎禾类草和VIII类降水(>35 mm)的发生频率和贡献率均呈显著的正相关关系。说明小降水事件的增加将显著降低群落的地上生物量, 小降水事件对干旱、半干旱区植被生长具有重要的生态学意义。
关键词：
Abstract
Aims Precipitation and its spatiotemporal changes are crucial for determining the effects of climate on plant community assembly and functioning of ecosystem (CAFE) in arid and semi-arid regions. Plant functional groups (PFGs) - an effective representation of CAFE—have been widely reported for their identity-dependent response to the changing climate. Here, we examine the responses of different PFGs to the temporal changes in precipitation by using aboveground biomass (AGB) as the dependent variable.
Methods We conducted a long-term ecological research of AGB since 1982 in a typical steppe grassland of Nei Mongol, China. We used the monthly-observation dataset from 1982 through 2015 to quantify the empirical relationships between AGB of different PDFs and precipitation.
Important findings We found that: 1) the decline in precipitation-concentration degree (PCD) was coupled with an increase in small rainfall events (≤5 mm) during the 35-year study period; 2) temporal changes in precipitation resulted in AGB decreases of annuals and biennials (AB), perennial forbs (PF) and perennial rhizome grass (PR), whereas AGB increased for perennial bunchgrasses (PB); 3) AGB, PF and semi-shrubs (SS) were positively correlated with growing season rainfall with AGB positively correlated with PCD while AGB of the shrubs (S) was negatively correlated with PCD; 4) AGB showed no significant correlation with precipitation frequency, but a significant negative correlation for type I to II precipitation 0.1-10 mm; 5) AGB had negative correlations with frequency and amount of type I (0.1-5.0 mm) and type VI (20-25 mm) precipitation. We concluded that the increase in small precipitation events will significantly reduce the AGB. These small precipitation events should be further explored for their ecological significances in the arid and semi-arid regions.
Keywords：
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引用本文
苗百岭, 梁存柱, 史亚博, 梁茂伟, 刘钟龄. 降水变化对内蒙古典型草原地上生物量的影响. 植物生态学报, 2019, 43(7): 557-565. DOI: 10.17521/cjpe.2018.0230
MIAO Bai-Ling, LIANG Cun-Zhu, SHI Ya-Bo, LIANG Mao-Wei, LIU Zhong-Ling.
水分是干旱半干旱区植被生长发育的主要限制因子(Sala et al., 1988; Easterling et al., 2000; Schwinning & Sala, 2004), 并且能够影响陆地生态系统对其他气候驱动因子变化的响应(Niu et al., 2007; Dijkstra et al., 2010), 而降水是这些地区的重要水分获得途径。同时干旱半干旱地区的降水格局也表现出较强的脉冲特征, 包括降水量的变化、降水季节分布的变化, 以及降水间隔的变化(Noy- Meir, 1973; Schwinning & Sala, 2004; Schwinning et al., 2004)。许多大气环流模型都预测未来全球降水格局会发生重大改变(IPCC, 2013), 同时还伴随着降水间隔增大、小降水事件减少和极端降水事件增加的趋势(Groisman et al., 1999; Easterling et al., 2000)。降水格局的变化不仅使陆地生态系统接受降水的变幅增大, 还将从不同层次, 包括个体、群落、生态系统水平, 对陆地生态系统产生影响(Knapp et al., 2001, 2002, 2008)。与其他陆地生态系统相比, 草原生态系统对降水变化更为敏感, 对资源可利用性的瞬时波动响应更大(Knapp & Smith, 2001; Conant et al., 2004), 在应对未来气候变化, 尤其是降水变化时, 必须考虑草原生态系统结构与功能的重要作用及其对气候变化的响应。
近些年来, 国内外****对气候变化背景下草原生态系统的植被生长等方面开展了大量的研究, 普遍认为降水是影响植被生长和地上初级生产力的重要因子(Knapp et al., 2017)。特别是对地处半干旱区的草原生态系统, 降水是其主要水分来源, 对植被生产力、生态系统结构和功能具有重要的影响(Mowll et al., 2015), 在维持群落稳定方面起到重要作用(Hallett et al., 2014), 如多数研究表明草原生态系统地上净初级生产力与降水量存在线性正相关关系(Knapp et al., 2001; Bai et al., 2008)等。另外, 不仅降水量, 降水频度也可能对植被生产力有重要的影响(Fay et al., 2003; Schwinning & Sala, 2004; Knapp et al., 2008)。然而同一群落不同功能型的植物在长期的进化过程中形成了各自的降水利用策略, 使得它们对降水变化的响应也不尽相同(Robertson et al., 2009, 2010)。功能型、光合途径、形态生理特征和生活史的不同使得不同物种对降水格局变化的响应不同(Swemmer et al., 2007; Nippert et al., 2009)。为了更好地理解群落对降水格局的响应, 我们应该比较研究不同功能型植物之间对降水格局变化响应的差别。
位于内蒙古锡林郭勒典型草原区的中国科学院草原生态系统定位研究站羊草样地自1979年围封以来一直未被利用, 可以认为群落生产力的波动是由气候变化造成的(谭丽萍和周广胜, 2013)。该样地已经连续观测了35年, 具有较长时间序列的群落调查数据和气候观测数据, 能够反映降水变化和群落响应的情况。本文利用1982-2015年群落组成、生物量调查数据和相同时段的气候观测数据分析了近30年来降水变化对草原生态系统地上生物量的影响。
1 材料和方法
1.1 实验样地设置
研究区位于内蒙古锡林郭勒草原自然保护区, 靠近中国科学院内蒙古草原生态系统定位研究站(IMGERS, 43.63° N, 116.7° E, 海拔1 187 m)。该区域是中亚半干旱草原生态系统的一部分, 属大陆性温带气候(Kawamura et al., 2005), 年平均温度为0.7 ℃, 年降水量约为350 mm, 主要集中在6-9月。植被生长季从4月中旬开始, 到9月下旬结束, 生长期时间相对较短(<150天)。地带性植被类型以羊草(Leymus chinensis)群落和大针茅(Stipa grandis)群落为主(Tong et al., 2004)。土壤类型属于栗钙土, 土层厚度为20-100 cm及以上, 伴有继发性的钙积层(Wiesmeier et al., 2009)。该羊草样地建于1979年, 面积为600 m × 300 m, 本研究资料为1982-2015年的样地观测数据, 以10年为周期(A01-A10)监测群落的地上生物量(图1), 每年5-9月, 以半个月为间隔做1次植被调查, 共9期监测数据(1-9)(图1), 每次监测20个分种样方, 登记植物种类, 测定植株高度、分种频度、分种密度、分种地上生物量。同期气象资料来源于中国科学院定位研究站(Li et al., 2015)。根据植物生活型将群落分为多年生根茎禾类草(PR)、多年生丛生禾草(PB)、多年生杂类草(PF)、灌木(S)、半灌木(SS)和一二年生植物(AB) 6个功能群(Bai et al., 2004)(表1), 样地具体信息见表2。
图1
新窗口打开|下载原图ZIP|生成PPT图1内蒙古锡林郭勒典型草原生物量监测方法示意图。A01-A10, 群落地上生物量逐年监测样带; 1-9, 每年生长季生物量监测样地。
Fig. 1Layout of the biomass sampling plots in a typical steppe grassland of Xilingol, Nei Mongol. A01-A10, a belt of biomass monitoring over a 10-year period; 1-9, a transect of biomass measurements during the growing seasons.
Table 1
表1
表1内蒙古锡林郭勒典型草原依据植物生活型划分的群落功能群
Table 1
| 功能群 Plant functional group | 物种 Species |
|---|---|
| 多年生根茎禾类草 Perennial rhizome grass | 根茎冰草、黄囊薹草、羊草 Agropyron michnoi, Carex korshinskii, Leymus chinensis |
| 多年生丛生禾草 Perennial bunchgrasses | 糙隐子草、大针茅、渐尖早熟禾、阿尔泰溚草、羊茅、羽茅 Cleistogenes squarrosa, Stipa grandis, Poa attenuata, Koeleria macrantha, Festuca ovina, Achnatherum sibiricum |
| 多年生杂类草 Perennial forbs | 阿尔泰狗娃花、矮韭、细叶白头翁、瓣蕊唐松草、花苜蓿、柔毛蒿、串铃草、北芸香、多叶棘豆、二裂委陵菜、二色补血草、防风、甘草、狗舌草、黄花韭、火绒草、菊叶委陵菜、柳穿鱼、轮叶委陵菜、麻花头、红纹马先蒿、蓬子菜、披针叶野决明、乳白花黄耆、乳浆大戟、长柱沙参、山韭、伏毛山莓草、砂韭、费菜、细叶韭、细叶鸢尾、红柴胡、少花米口袋、达乌里芯芭、星毛委陵菜、宿根亚麻、野韭、直立黄芪、多裂叶荆芥、山蚂蚱草、女娄菜、翼茎风毛菊 Heteropappus altaicus, Allium anisopodium, Pulsatilla turczaninovii, Thalictrum petaloideum, Medicago ruthenica, Artemisia pubescens, Phlomis mongolica, Haplophyllum dauricum, Oxytropis myriophylla, Potentilla bifurca, Limonium bicolor, Saposhnikovia divaricata, Glycyrrhiza uralensis, Tephroseris kirilowii, Allium condensatum, Leontopodium leontopodioides, Potentilla tanacetifolia, Linaria vulgaris subsp. sinensis, Potentilla verticillaris, Klasea centauroides, Pedicularis striata, Galium verum, Thermopsis lanceolata, Astragalus galactites, Euphorbia esula, Adenophora stenanthina, Allium senescens, Sibbaldia adpressa, Allium bidentatum, phedimus aizoon, Allium tenuissimum, Iris tenuifolia, Bupleurum scorzonerifolium, Gueldenstaedtia verna, Cymbaria daurica, Potentilla acaulis, Linum perenne, Allium ramosum, Astragalus adsurgens, Nepeta multifida, Silene jenisseensis, Silene aprica, Saussurea japonica var. pteroclada |
| 灌木 Shrubs | 小叶锦鸡儿 Caragana microphylla |
| 半灌木 Semi-shrubs | 冷蒿、木地肤、燥原荠 Artemisia frigida, Kochia prostrata, Ptilotricum canescens |
| 一二年生植物 Annuals and biennials | 刺藜、大籽蒿、瓦松、鹤虱、猪毛蒿、藜、小花花旗杆、鳞叶龙胆、轴藜、猪毛菜 Dysphania aristata, Artemisia sieversiana, Orostachys fimbriatus, Lappula myosotis, Artemisia scoparia, Chenopodium album, Dontostemon micranthus, Gentiana squarrosa, Axyris amaranthoides, Salsola collina |
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Table 2
表2
表2内蒙古锡林郭勒典型草原羊草样地的基本信息
Table 2
| 地上生物量 Aboveground biomass (g·m-2) | 降水量 Precipitation (mm) | 相对多度 Relative Abundance (%) | ||||||
|---|---|---|---|---|---|---|---|---|
| 年 Year | 生长季 Growing season | 多年生根茎禾类草 Perennial rhizome grass | 多年生丛生禾草 Perennial bunchgrasses | 多年生杂类草 Perennial forbs | 一二年生植物 Annuals and biennials | 灌木 Shrubs | 半灌木 Semi-shrubs | |
| 195.8 | 330.8 | 287.9 | 63.4 | 19.3 | 9.9 | 4.8 | 1.9 | 0.7 |
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1.2 降水等级划分标准
通过分析历史数据, 并参考中国气象局降水等级标准(高继卿等, 2015)以及Sala和Lauenroth (1982)的研究结果, 本文将研究区降水分为以下8个等级(表3)。其中, 将0.1 ≤ R ≤ 5 mm定义为小降水事件, 并统计各等级降水的频率和贡献率。降水频率指各等级降水日数占年降水日数百分比, 降水贡献率指各等级降水量占年降水量的比值。Table 3
表3
表3内蒙古锡林郭勒典型草原羊草样地降水等级划分标准
Table 3
| 编号 ID | 日降水量 Daily precipitation (mm) | 降水等级 Precipitation grade |
|---|---|---|
| I | 0.1-5 | 小雨/小雪-中雪 Light rain/Light snow-Moderate snow |
| II | 5-10 | 小雨/中雪-大雪 Light rain/Moderate snow-Heavy snow |
| III | 10-15 | 中雨/暴雪 Moderate rain/Torrential snow |
| IV | 15-20 | 中雨/暴雪 Moderate rain/Torrential snow |
| V | 20-25 | 中雨/暴雪-大暴雪 Moderate rain/Torrential snow-Snowstorm |
| VI | 25-30 | 大雨/大暴雪 Heavy rain/Snowstorm |
| VII | 30-35 | 大雨/大暴雪 Heavy rain/Snowstorm |
| VIII | >35 | 大雨-暴雨/大暴雪-特大暴雪 Heavy rain-Torrential rain/Snowstorm- Historical extreme snow |
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降水变化可能仅仅是湿润土壤表面的小事件, 也可能是影响深层土壤水分动态、周期长达数十年的大事件。有研究表明, 2 mm的小降水事件只会引起表层土壤微生物的活动, 导致土壤硝态氮增加或发生短暂的分解变化, 大于3 mm的降水可提高某些高大植物的碳同化速率或者土壤结皮生物的净碳收益, 而大于25 mm的降水则可能引起多数荒漠植物萌发。因此, 研究干旱地区降水脉冲量级特征和变化趋势可更精细地了解荒漠植被与降水之间的关系(刘冰等, 2010; 郑新倩等, 2012)。
1.3 降水集中度计算方法
为研究年内降水分配不均匀性特征, 或年内降水分配情况, 本文采用张录军和钱永甫(2004)定义的表征单站降水量时间分配特征的参数, 即降水集中度(PCD), 其公式(张录军和钱永甫, 2004; 任志艳等, 2016)可表示为:式中, PCDi表示第i年的降水集中度; i为年份; j为旬序; Ri为第i年内总降水量(mm); Rij为第i年第j旬的降水量(mm); ${{\theta }_{j}}~=\ ~360{}^\circ \times (j-1)/36$, 为研究时段内各旬所对应的矢量角度。PCDi越接近于1, 则表示年降水量集中在某一旬内; 越接近于0, 则表示年降水量分布越均匀。
2 结果
2.1 1982-2015年研究区降水变化特征
1982-2015年研究区年降水量总体变化趋势不明显, 有降低趋势(-8.44 mm·10 a-1, p = 0.51), 但年际间波动较大(21.84%)。而降水集中度却呈极显著降低趋势(-0.04·10 a-1, p < 0.001), 导致生长季的降水也呈降低趋势(-14.27 mm·10 a-1, p = 0.22), 降水的年内分布格局已经发生了明显改变。为了进一步分析降水格局的年内分布特征, 对各等级降水的频率和贡献率分别进行了统计分析(表4), 结果表明: Ⅰ类降水的平均发生频率(79.15%)和贡献率(28.80%)均为最高, 随着降水等级的升高, 降水频率和贡献率逐渐降低, 变异系数逐渐加大, 降水波动性增强(Ⅶ类除外)。Ⅵ-Ⅷ类降水出现了43次, 其中Ⅷ类降水就占了16次; 90年代出现最多, VIII类降水出现10次。年降水的波动主要是由>25 mm的降水(Ⅵ-Ⅷ类)变化引起的。
Table 4
表4
表41982-2015年内蒙古锡林郭勒典型草原羊草样地各等级降水变化特征
Table 4
| 编号 ID | 日降水量(mm) Daily precipitation | 降水频率(%) Precipitation frequency | 降水贡献率(%) Contribution to the total rainfall | ||||||
|---|---|---|---|---|---|---|---|---|---|
| 平均值 Average | 变异系数 CV | 变化率 Change rate | p | 平均值 Average | 变异系数 CV | 变化率 Change rate | p | ||
| Ⅰ | 0.1-5 | 79.15 | 6.30 | 0.28** | 0.00 | 28.80 | 21.43 | 0.26* | 0.02 |
| Ⅱ | 5-10 | 10.62 | 40.81 | -0.15* | 0.04 | 21.71 | 44.11 | -0.07 | 0.66 |
| Ⅲ | 10-15 | 5.27 | 49.04 | -0.06 | 0.21 | 18.12 | 45.72 | 0.00 | 0.99 |
| Ⅳ | 15-20 | 2.43 | 61.63 | -0.04 | 0.17 | 12.10 | 61.22 | -0.08 | 0.53 |
| Ⅴ | 20-25 | 1.16 | 97.60 | -0.01 | 0.54 | 7.04 | 92.22 | -0.01 | 0.91 |
| Ⅵ | 25-30 | 0.52 | 121.14 | -0.01 | 0.24 | 3.67 | 118.56 | -0.07 | 0.40 |
| Ⅶ | 30-35 | 0.35 | 193.38 | -0.02 | 0.13 | 2.96 | 187.87 | -0.13 | 0.18 |
| Ⅷ | >35 | 0.49 | 171.51 | 0.01 | 0.63 | 5.60 | 163.85 | 0.11 | 0.50 |
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从变化趋势来看, 1982-2015年Ⅰ类降水的发生频率和贡献率均有显著增加趋势(p ≤ 0.001), Ⅱ类降水的发生频率呈显著降低趋势, 但降水贡献率没有明显变化趋势。小降水事件逐渐增多, 而5-10 mm降水发生频率呈逐渐减少趋势(表4)。可见, 小降水事件发生的频率较高, 对年降水总量的贡献率大且稳定。
2.2 1982-2015年研究区群落地上生物量的变化 趋势
1982-2015年, 研究区群落生物量(BTmax)(出现在7-8月间)略呈下降趋势(-1.79 g·m-2·a-1, R2 = 0.13, p = 0.04)。其中, 多年生杂类草、多年生根茎禾类草、灌木的生物量呈显著下降趋势(p ≤ 0.04), 变化率分别为每年-0.74 g·m-2、-1.15 g·m-2、-0.61 g·m-2; 多年生丛生禾草与一二年生植物的生物量变化趋势不显著(p ≥ 0.51), 斜率分别为0.29和-0.02; 而半灌木的生物量却呈显著上升趋势(0.44 g·m-2·a-1, p < 0.001)。2.3 降水变化对群落地上生物量的影响
本文利用1982-2015年群落、各功能型地上生物量与生长季降水量、降水集中度进行了回归分析。分析结果发现, 群落地上生物量与生长季降水量(R)、降水集中度呈显著的正相关关系, 随着生长季降水量的减少和降水集中度的降低, 地上生物量略有降低趋势(图2A、2B)。其回归方程分别为: BTmax = 0.27R + 112.06 (R2 = 0.17, p = 0.02); BTmax = 177.33PCD + 76.25 (R2 = 0.12, p = 0.05)。图2
新窗口打开|下载原图ZIP|生成PPT图2内蒙古锡林郭勒典型草原羊草样地群落和各功能群的地上生物量对降水变化的响应。
Fig. 2Response of aboveground biomass (AGB) by community and functional group to precipitation in the typical grassland of Xilin Gol, Nei Mongol.
在各功能群中, 多年生杂类草的地上生物量和生长季降水量显著正相关(BTPF = 0.15R - 14.86, R2 = 0.27, p < 0.01), 半灌木的地上生物量与降水集中度显著负相关(BTSS = -33.79PCD + 30.65, R2 = 0.16, p = 0.02)。随着研究区降水量的减少和集中度的降低, 多年生杂类草的地上生物量有减少趋势, 而半灌木有明显增加趋势。除此以外, 其他各功能群的地上生物量与生长季降水量和降水集中度的相关性均不显著, 对降水变化的响应较弱。
为了探讨不同等级降水事件对群落的影响程度, 本文还利用了1982-2015年不同等级降水的发生频率和贡献率分别与群落、各功能群的地上生物量进行了相关分析(表5, 表6)。从表5中可知, BTmax与各等级降水的频率相关性均不显著。各功能群中, 多年生杂类草与I类降水(0.1-5 mm)发生频率呈显著的负相关关系, 与VI类降水(20-25 mm)发生频率呈显著的正相关关系。多年生根茎禾类草和VIII类降水(>35 mm)发生频率显著正相关。
Table 5
表5
表5内蒙古锡林郭勒典型草原羊草样地群落地上峰值生物量与各等级降水发生频率之间的相关分析
Table 5
| 编号 ID | 日降水量(mm) Daily precipitation | 生物量 Biomass | 多年生杂类草 Perennial forbs | 多年生根茎禾草 Perennial rhizome grass | 多年生丛生禾草 Perennial bunchgrasses | 一二年生植物 Annuals and biennials | 半灌木 Semi-shrubs | 灌木 Shrubs |
|---|---|---|---|---|---|---|---|---|
| I | 0.1-5 | -0.23 | -0.50** | -0.02 | -0.04 | -0.01 | 0.40* | -0.27 |
| II | 5-10 | -0.06 | 0.19 | -0.13 | -0.14 | 0.15 | -0.28 | 0.18 |
| III | 10-15 | 0.15 | 0.25 | -0.01 | 0.12 | -0.13 | -0.16 | 0.23 |
| IV | 15-20 | 0.24 | 0.24 | 0.04 | 0.18 | -0.05 | -0.03 | 0.17 |
| V | 20-25 | 0.12 | 0.10 | 0.07 | 0.17 | -0.09 | -0.08 | -0.13 |
| VI | 25-30 | 0.33 | 0.55** | 0.19 | 0.04 | -0.04 | -0.17 | -0.08 |
| VII | 30-35 | 0.19 | 0.34 | 0.11 | -0.02 | -0.07 | -0.19 | 0.11 |
| VIII | >35 | 0.22 | -0.00 | 0.39* | -0.00 | -0.00 | -0.00 | -0.17 |
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Table 6
表6
表6内蒙古锡林郭勒典型草原羊草样地群落地上生物量与各等级降水贡献率之间的相关分析
Table 6
| 编号 ID | 日降水量(mm) Daily precipitation | 生物量 Biomass | 多年生杂类草 Perennial forbs | 多年生根茎禾草 Perennial rhizome grass | 多年生丛生禾草 Perennial bunchgrasses | 一二年生植物 Annuals and biennials | 半灌木 Semi-shrubs | 灌木 Shrubs |
|---|---|---|---|---|---|---|---|---|
| I | 0.1-5 | -0.53** | -0.58** | -0.28 | -0.22 | -0.02 | 0.23 | -0.07 |
| II | 5-10 | -0.30 | -0.08 | -0.30 | -0.21 | 0.21 | -0.08 | 0.10 |
| III | 10-15 | 0.00 | 0.04 | -0.06 | 0.03 | -0.15 | 0.01 | 0.16 |
| IV | 15-20 | 0.17 | 0.10 | -0.00 | 0.18 | -0.02 | 0.12 | 0.13 |
| V | 20-25 | 0.06 | -0.02 | 0.07 | 0.14 | -0.09 | -0.03 | -0.19 |
| VI | 25-30 | 0.26 | 0.50** | 0.10 | 0.06 | -0.02 | -0.15 | -0.11 |
| VII | 30-35 | 0.20 | 0.32 | 0.12 | 0.01 | -0.06 | -0.15 | 0.08 |
| VIII | >35 | 0.24 | -0.05 | 0.38* | 0.06 | 0.06 | 0.01 | -0.18 |
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从表6中可知, 只有I-II类降水贡献率与群落BTmax呈显著的负相关关系(p < 0.048), 其他等级降水贡献率与群落生物量相关性均不显著(p > 0.160)。在各功能群中, 多年生杂类草与I类降水贡献率呈显著的负相关关系, 与VI类降水贡献率呈显著的正相关关系。多年生根茎禾类草与VIII类降水贡献率呈显著的正相关关系。
3 讨论
3.1 研究区降水变化对群落地上生物量的影响
在干旱与半干旱区, 降水事件通常以脉动的形式发生, 降水发生时间、持续时间、强度等参数具有较大的变异性(Sala & Lauenroth, 1982; 赵学勇等, 2014)。本文发现: 1982-2015年研究区≤5 mm和 ≤10 mm降水分别占总降水频次的80%和90%, 与科尔沁沙地的统计结果(马赟花等, 2015)一致, 也与Sala和Lauenroth (1982)在北美草原的统计结果接近。近些年来, 研究区小降水事件的发生频率和降水贡献率都有逐年增加的趋势, 直接导致了降水集中度的降低。以往研究发现, 降水脉动可以导致土壤水分与养分等资源也呈脉动状态, 进而影响着种群动态、群落变化等生态系统过程(Noy-Meir, 1973)。Noy- Meir (1973)发现降水脉动可能是干旱与半干旱生态系统演替的核心驱动力和不同植物功能类型共存的重要原因。国内外****围绕降水脉动发生时间、强度及其对生态系统的影响等方面, 先后提出了脉动- 存贮理论(Pulse-Reserve)(Noy-Meir, 1973)、水分分割理论(Two-Layer Soil Water-Partitioning)(Walter, 1971)等理论模型。其中, 脉动-存贮理论是干旱与半干旱区生态系统研究中广泛应用的一个理论。该理论认为降水脉动能够触发植物生长脉动与碳和能量储存之间的关系, 这种存贮能力在两次降水间隔期内处于休眠状态, 此时生态系统初级生产力不再增长(Noy-Meir, 1973; Schwinning et al., 2004; 赵文智和刘鹄, 2011)。Ludwig等(1996)认为该理论体现了干旱与半干旱降水事件的生态学意义。但是Reynolds等(2004)认为, 在生态系统中, 大降水事件不一定使生态系统生产力出现净增长(Snyder et al., 2004), 而小降水事件却有可能导致明显的生态响应, 降水与生态系统之间的关系并不完全符合脉动- 存贮理论(Reynolds et al., 2000)。
在许多研究中, ≤5 mm的降水被认为是无效降水, 因其仅能润湿表层土壤, 不能到达植物根系(Dougherty et al., 1996)。Owens等(2006)研究发现, ≤2.5 mm的降水几乎全部被植物冠层截留。通常认为, 被冠层截留的这部分降水以蒸发形式返回大气, 而不能被根系吸收利用(Owens et al., 2006)。本文中群落生物量与≤5 mm的降水均呈显著的负相关关系, 与生长季降水量呈显著正相关关系。和生长季降水对群落地上生物量有促进作用不同, 小降水事件对群落地上生物量有明显的抑制作用, 可能是因为小于10 mm的降水在土壤里下渗较浅, 大部分水分将会被蒸发掉, 对土壤的补给较少, 能被植物利用的更少。郭柯等(2000)在毛乌素沙地的研究也表明, 小于5 mm的降水在固定沙地下渗的深度只有5 cm左右, 雨后绝大部分的雨水被蒸发掉, 对固定沙地灌木根系层土壤水分的补充基本没有效果。本研究进一步发现: 在过去的30多年间, 研究区小降水事件(0.1-5 mm)的发生频率和降水贡献率都呈逐年增加趋势, 导致了降水集中度下降, 造成BTmax略有下降趋势(p = 0.051)。综合来看, 小降水事件主要通过影响降水的分布和强度, 间接影响土壤水分, 进而对生态系统的功能造成影响, 这与Reynolds等(2004)在北美的研究结论基本一致。Lauenroth和Sala (1992)在科罗拉多的短草草原研究发现, 15-30 mm的降水是ANPP受影响的有效降水。本研究中发现, ≥25 mm的降水与多年生根茎禾类草、多年生杂类草的地上生物量显著正相关, 能够增加群落的地上生物量, 是有效降水。
3.2 不同生活型植物对降水变化的响应
本研究发现, 小降水事件(I)的增多降低了群落中多年生杂类草的地上生物量, 大降水事件(VI- VIII)的波动会对多年生根茎禾类草和多年生杂类草的地上生物量产生显著影响, 而降水变化对其他几个植物功能型均无显著影响, 这可能与不同植物功能型获得水资源的策略不同有关。Reynolds等(2004)认为植物的这种响应过程与群落组成、前期土壤水分状况和生长阶段都有密切关系。多年生丛生禾草与一二年生植物更多利用的是表层土壤水分, 它们的根系较浅, 大部分根系集中在土壤剖面的上部(Sims et al., 1978), 能够对土壤水分的增加做出非常迅速的反应。相反, 多年生杂类草与多年生根茎禾类草等植物根系相对较深, 利用的主要是深层土壤水分(Soriano & Sala, 1984)。Walter的水分分割理论认为, 小降水事件能有效地补给表层土壤水分, 而大降水事件则能补给深层土壤水分。随着研究区小降水事件的增多, 对深层土壤水分的补给越来越少, 从而对多年生杂类草和多年生根茎禾类草等深根系植物产生显著影响, 降水格局变化导致土壤水分变异性增加引起根系活性降低, 这可能是导致多年生杂类草生物量降低的一个机制。另外, 禾本科C4植物比多年生杂类草C3植物的光合水分利用效率更高(Knapp & Medina, 1999), 能够有效抵御降水变化的影响(Fay et al., 2003; 牛书丽等, 2004), 这可能是多年生丛生禾草等生物量相对稳定的一个机制。羊草与大针茅种群是研究区的主要建群种, 尽管它们广泛共生, 有着相似的光合生理和生活史, 但它们对降水的变化表现出截然不同的反应。本研究中发现以羊草为代表的多年生根茎禾类草与≥35 mm的降水发生频率与贡献率均呈显著的正相关关系, 而以大针茅为代表的多年生丛生禾草对水分梯度的响应并不显著, 这可能与两种植物的根系构型有关。鲍雅静等(2019)研究发现, 相比大针茅种群, 羊草根系特征对水分梯度的响应更为显著, 羊草主要是通过根茎长度和密度等数量特征来调节对水分梯度的响应, 而大针茅的根系对水分梯度的响应并不敏感, 可能把更多的能力投资在丛幅的扩大上, 这与崔骁勇等(2001)的研究结论基本一致, 其认为大针茅对干旱的调节机制不是通过调整根系提高水分利用效率实现的, 而是通过提高水分竞争能力、降低水分蒸腾来实现的。因此, 相对于优势种, 亚优势种受降水变化的影响可能更强, 正是因为应对降水变化策略的差异性, 才使得草原生态系统保持稳定。
3.3 结论
1) 1982-2015年, 研究区年降水量变化趋势均不明显, 而降水集中度呈显著的降低趋势。在各等级降水事件中, ≤5 mm降水事件的发生频率和对年降水量的贡献率均有增加趋势, 导致了降水集中度的显著降低; ≥25 mm降水事件和连续无降水日的变化造成了降水的年际间波动。2) 1982-2015年, 研究区群落地上生物量没有明显变化, 总生物量略显下降趋势。生长季降水的波动是群落地上生物量的主要限制因素。近些年来, 降水事件组合发生的改变, 对群落地上生物量产生了显著的影响。
参考文献 原文顺序
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High biodiversity aboveground tends to increase the stability of ecosystem functioning when faced with a changing environment. However, whether and how soil biota affect ecosystem stability is less clear. Here, we introduce a framework for understanding the effects of soil biota on variation in ecosystem functioning under environmental changes. We conclude that soil biota may be a neglected factor determining ecosystem stability through their direct and indirect effects on plant diversity, the net productivity of an ecosystem, and compensatory dynamics among plant species, and via altering ecosystem resistance and resilience. Furthermore, future research needs to consider that effects of soil biota on ecosystem stability will vary depending on extrinsic factors, and for a given perturbation and ecosystem function.
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DOI:10.1007/s11356-019-06538-4URLPMID:31838703 [本文引用: 1]
Valuation of environmental goods and services are frequently spatially heterogeneous, the significance of this heterogeneity for policy analysis is gradually recognized. For the valuation of environmental goods and services in the context of attaining a better environmental status across Heihe River basin (HRB), Northwest of China by 2020, a survey was conducted employing choice experiment approach across the entire river basin. In this research we estimate the impact of distance from inland rivers' origin (spatial attribute) on the inhabitants' willingness to pay for restoration of ecological attributes. A total of 11 ecological attributes were selected including 6 land related attributes and 5 water related attributes. The present study displays the outcomes of the research planned to examine differences in willingness to pay across different locations/distances. A total of five cities and 33 surround villages/townships were included to examine for location effect, while four ad hoc base distances split samples were recognized for distance effect i.e. ≤100?km, ≤200?km, ≤300 and?&gt;?300?km from rivers' origin. The results of mixed logit model recognized that people living at different locations value the attributes differently. For instance the people of Zhangye region are willing to pay RMB 95.66 annually for improvements in biodiversity while in Gaotai the individuals' willingness to pay (WTP) for the same attributes was RMB 45.68. Similarly, the respondents' living nearer to the origin of river were willing to pay relatively higher amount for the upgradation in the degraded ecosystem services than the remainders. The results of willingness to pay obtained by Krinsky Robb method confirmed that the attributes quality of agricultural products and water quality were the most preferred attributes with the willingness to pay RMB 91.09 and 122.89 respectively. The significant results of willingness to pay may serve as a reference for sustainable improvements and uplifting of the degraded ecological attributes.
DOI:10.1641/B580908URL [本文引用: 2]
DOI:10.1007/s100210000057URL [本文引用: 1]
DOI:10.1111/nph.14381URLPMID:28001290 [本文引用: 1]
Contents 41 I. 41 II. 42 III. 43 IV. 44 V. 45 Acknowledgements 46 References 46 SUMMARY: Precipitation (PPT) is a primary climatic determinant of plant growth and aboveground net primary production (ANPP) over much of the globe. Thus, PPT-ANPP relationships are important both ecologically and to land-atmosphere models that couple terrestrial vegetation to the global carbon cycle. Empirical PPT-ANPP relationships derived from long-term site-based data are almost always portrayed as linear, but recent evidence has accumulated that is inconsistent with an underlying linear relationship. We review, and then reconcile, these inconsistencies with a nonlinear model that incorporates observed asymmetries in PPT-ANPP relationships. Although data are currently lacking for parameterization, this new model highlights research needs that, when met, will improve our understanding of carbon cycle dynamics, as well as forecasts of ecosystem responses to climate change.
DOI:10.1126/science.1076347URLPMID:12481139 [本文引用: 1]
Ecosystem responses to increased variability in rainfall, a prediction of general circulation models, were assessed in native grassland by reducing storm frequency and increasing rainfall quantity per storm during a 4-year experiment. More extreme rainfall patterns, without concurrent changes in total rainfall quantity, increased temporal variability in soil moisture and plant species diversity. However, carbon cycling processes such as soil CO2 flux, CO2 uptake by the dominant grasses, and aboveground net primary productivity (ANPP) were reduced, and ANPP was more responsive to soil moisture variability than to mean soil water content. Our results show that projected increases in rainfall variability can rapidly alter key carbon cycling processes and plant community composition, independent of changes in total precipitation.
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DOI:10.1073/pnas.0700180104URLPMID:17360349 [本文引用: 1]
Understanding ecosystem processes as they relate to wildfire and vegetation dynamics is of growing importance as fire frequency and extent increase throughout the western United States. However, the effects of severe, stand-replacing wildfires are poorly understood. We studied inorganic nitrogen pools and mineralization rates after stand-replacing wildfires in the Greater Yellowstone Ecosystem, Wyoming. After fires that burned in summer 2000, soil ammonium concentration peaked in 2001 (33 mg NH(4)-N x kg(soil)(-1)); soil nitrate increased subsequently (2.7 mg NO(3)-N.kg(soil)(-1) in 2003) but was still low. However, annual net ammonification rates were largely negative from 2001 to 2004, indicating ammonium depletion. Thus, although net nitrification rates were positive, annual net nitrogen mineralization (net ammonification plus net nitrification) remained low. Aboveground net primary production (ANPP) increased from 0.25 to 1.6 Mg x ha(-1) x yr(-1) from 2001 to 2004, but variation in ANPP among stands was not related to net nitrogen mineralization rates. Across a broader temporal gradient (stand age zero to &gt;250 yr), negative rates of net annual ammonification were especially pronounced in the first postfire year. Laboratory incubations using (15)N isotope pool dilution revealed that gross production of ammonium was reduced and ammonium consumption greatly exceeded gross production during the initial postfire years. Our results suggest a microbial nitrogen sink for several years after severe, stand-replacing fire, confirming earlier hypotheses about postdisturbance succession and nutrient cycling in cold, fire-dominated coniferous forests. Postfire forests in Yellowstone seem to be highly conservative for nitrogen, and microbial immobilization of ammonium plays a key role during early succession.
DOI:10.2307/1941874URLPMID:27759270 [本文引用: 1]
We evaluated the relationship between annual forage production and annual and seasonal precipitation and temperature at a shortgrass steppe site in north-central Colorado using a long-term data set (52 yr). We also constructed a relationship between forage production and aboveground net primary production (ANPP). Precipitation fluctuated randomly, but temperature had clear warming and cooling trends including a 17-yr warming trend from 1974 to 1990. Forage production was significantly related to both annual and seasonal precipitation but not temperature. Precipitation events between 15 and 30 mm accounted for most of the variability in production because they accounted for most of the variability in precipitation and because they wetted the soil layers that have the largest effect on production. Forage production amplified variability in annual precipitation. Production showed time lags of several years in responding to increases in precipitation. Change in vegetation structure has a characteristic response time, which contrains production responses in wet years. Constraint caused by vegetation structure is the reason why regional ANPP-precipitation models have a steeper slope than long-term models and point out a weakness of exchanging space for time in predicting production patterns.
DOI:10.1007/s10980-014-0068-1URL [本文引用: 1]
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CSIRO Publishing, Melbourne.
[本文引用: 2]
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DOI:10.1007/s00442-015-3232-7URLPMID:25669452 [本文引用: 1]
Although climate models forecast warmer temperatures with a high degree of certainty, precipitation is the primary driver of aboveground net primary production (ANPP) in most grasslands. Conversely, variations in temperature seldom are related to patterns of ANPP. Thus forecasting responses to warming is a challenge, and raises the question: how sensitive will grassland ANPP be to warming? We evaluated climate and multi-year ANPP data (67 years) from eight western US grasslands arrayed along mean annual temperature (MAT; ~7-14 °C) and mean annual precipitation (MAP; ~250-500 mm) gradients. We used regression and analysis of covariance to assess relationships between ANPP and temperature, as well as precipitation (annual and growing season) to evaluate temperature sensitivity of ANPP. We also related ANPP to the standardized precipitation evaporation index (SPEI), which combines precipitation and evapotranspiration to better represent moisture available for plant growth. Regression models indicated that variation in growing season temperature was negatively related to total and graminoid ANPP, but precipitation was a stronger predictor than temperature. Growing season temperature was also a significant parameter in more complex models, but again precipitation was consistently a stronger predictor of ANPP. Surprisingly, neither annual nor growing season SPEI were as strongly related to ANPP as precipitation. We conclude that forecasted warming likely will affect ANPP in these grasslands, but that predicting temperature effects from natural climatic gradients is difficult. This is because, unlike precipitation, warming effects can be positive or negative and moderated by shifts in the C3/C4 ratios of plant communities.
DOI:10.1016/j.actao.2009.01.010URL [本文引用: 1]
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DOI:10.1111/j.1469-8137.2007.02237.xURLPMID:17944829 [本文引用: 4]
Global warming and a changing precipitation regime could have a profound impact on ecosystem carbon fluxes, especially in arid and semiarid grasslands where water is limited. A field experiment manipulating temperature and precipitation has been conducted in a temperate steppe in northern China since 2005. A paired, nested experimental design was used, with increased precipitation as the primary factor and warming simulated by infrared radiators as the secondary factor. The results for the first 2 yr showed that gross ecosystem productivity (GEP) was higher than ecosystem respiration, leading to net C sink (measured by net ecosystem CO(2) exchange, NEE) over the growing season in the study site. The interannual variation of NEE resulted from the difference in mean annual precipitation. Experimental warming reduced GEP and NEE, whereas increased precipitation stimulated ecosystem C and water fluxes in both years. Increased precipitation also alleviated the negative effect of experimental warming on NEE. The results demonstrate that water availability plays a dominant role in regulating ecosystem C and water fluxes and their responses to climatic change in the temperate steppe of northern China.
DOI:10.5604/01.3001.0011.6142URLPMID:30015424 [本文引用: 2]
Rhizobacteria are an active part of microbial population in the rhizosphere of plants. In this study, twenty rhizobacteria were isolated from the rhizosphere of a perennial grass, Haloxylon salicornicum, found in Cholistan desert, an arid landmass near Bahawalpur Pakistan, in one set of experimental conditions. Colony characteristics, biochemical and molecular analyses of these isolates were performed. All isolates were bacilli, gram positive with off-white colonies and exhibited typical bacilli colony morphology. None of the isolates was gelatinase, urease, indole, H2S and catalase producer. Eleven isolates were amylase producers and 8 isolates were acid producers. All isolates fermented glucose, 3 fermented lactose and 19 fermented fructose. Molecular data revealed that out of twenty isolates, 14 isolates showed 91-99% identity with Brevibacillus borstelensis, 4 with Bacillus subtilis (97-98%) and 2 with Bacillus licheniformis (94-99%) through BLAST analysis. All identified bacterial isolates cladded with their respective groups in the phylogenetic tree. Many (11-15 out of 20) of the isolates were more effective in inhibiting growth of the tested bacterial strains as compared to the positive control (Ampicillin 50 μg/disc). We conclude that bacilli are the predominant form populating rhizosphere of this desert grass. Among the isolated bacteria Brevibacillus borstelensis, Bacillus subtilis and Bacillus licheniformis are the most predominant species.
DOI:10.1002/(ISSN)1099-1085URL [本文引用: 1]
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DOI:10.1007/s00442-004-1524-4URLPMID:15042457 [本文引用: 3]
The 'pulse-reserve' conceptual model--arguably one of the most-cited paradigms in aridland ecology--depicts a simple, direct relationship between rainfall, which triggers pulses of plant growth, and reserves of carbon and energy. While the heuristics of 'pulses', 'triggers' and 'reserves' are intuitive and thus appealing, the value of the paradigm is limited, both as a conceptual model of how pulsed water inputs are translated into primary production and as a framework for developing quantitative models. To overcome these limitations, we propose a revision of the pulse-reserve model that emphasizes the following: (1) what explicitly constitutes a biologically significant 'rainfall pulse', (2) how do rainfall pulses translate into usable 'soil moisture pulses', and (3) how are soil moisture pulses differentially utilized by various plant functional types (FTs) in terms of growth? We explore these questions using the patch arid lands simulation (PALS) model for sites in the Mojave, Sonoran, and Chihuahuan deserts of North America. Our analyses indicate that rainfall variability is best understood in terms of sequences of rainfall events that produce biologically-significant 'pulses' of soil moisture recharge, as opposed to individual rain events. In the desert regions investigated, biologically significant pulses of soil moisture occur in either winter (October-March) or summer (July-September), as determined by the period of activity of the plant FTs. Nevertheless, it is difficult to make generalizations regarding specific growth responses to moisture pulses, because of the strong effects of and interactions between precipitation, antecedent soil moisture, and plant FT responses, all of which vary among deserts and seasons. Our results further suggest that, in most soil types and in most seasons, there is little separation of soil water with depth. Thus, coexistence of plant FTs in a single patch as examined in this PALS study is likely to be fostered by factors that promote: (1) separation of water use over time (seasonal differences in growth), (2) relative differences in the utilization of water in the upper soil layers, or (3) separation in the responses of plant FTs as a function of preceding conditions, i.e., the physiological and morphological readiness of the plant for water-uptake and growth. Finally, the high seasonal and annual variability in soil water recharge and plant growth, which result from the complex interactions that occur as a result of rainfall variability, antecedent soil moisture conditions, nutrient availability, and plant FT composition and cover, call into question the use of simplified vegetation models in forecasting potential impacts of climate change in the arid zones in North America.
DOI:10.1023/A:1026530522612URL [本文引用: 2]
DOI:10.1111/j.1469-8137.2008.02643.xURLPMID:19076724 [本文引用: 1]
Plant productivity in deserts may be more directly responsive to soil water availability than to precipitation. However, measurement of soil moisture alone may not be enough to elucidate plant responses to precipitation pulses, as edaphic factors may influence productivity when soil moisture is adequate. The first objective of the study was to determine the responses of the aboveground annual net primary productivity (ANPP) of three perennial species (from different functional groups) in a Chihuahuan Desert grassland to variation in natural precipitation (annual and seasonal) and a 25% increase in seasonal precipitation (supplemental watering in summer and winter). Secondly, ANPP responses to other key environmental and soil parameters were explored during dry, average, and wet years over a 5-yr period. ANPP predictors for each species were dynamic. High ANPP in Dasylirion leiophyllum was positively associated with higher soil NH(4)-N and frequent larger precipitation events, while that in Bouteloua curtipendula was positively correlated with frequent small summer precipitation events with short inter-pulse periods and supplemental winter water. Opuntia phaeacantha was responsive to small precipitation events with short inter-pulse periods. Although several studies have shown ANPP increases with increases in precipitation and soil moisture in desert systems, this was not observed here as a universal predictor of ANPP, particularly in dry years.
DOI:10.1007/s00442-009-1449-zURLPMID:19756763
Arid and semi-arid environments are dynamic ecosystems with highly variable precipitation, resulting in diverse plant communities. Changes in the timing and magnitude of precipitation due to global climate change may further alter plant community composition in desert regions. In this study, we assessed changes in species richness and plant density at the community, functional group, and species level in response to variation in the magnitude of natural seasonal precipitation and 25% increases in seasonal precipitation [e.g., supplemental watering in summer, winter, or summer and winter (SW)] over a 5-year period in a sotol grassland in the Chihuahuan Desert. Community species richness was higher with increasing winter precipitation while community plant density increased with greater amounts of winter and summer precipitation, suggesting winter precipitation was important for species recruitment and summer precipitation promoted growth of existing species. Herb and grass density increased with increasing winter and summer precipitation, but only grass density showed a significant response to supplemental watering treatments (SW treatment plots had higher grass density). Shrubs and succulents did not exhibit changes in richness or density in response to natural or supplemental precipitation. In this 5-year study, changes in community species richness and density were driven by responses of herb and grass species that favored more frequent small precipitation events, shorter inter-pulse duration, and higher soil moisture. However, due to the long life spans of the shrub and succulent species within this community, 5 years may be insufficient to accurately evaluate their response to variable timing and magnitude of precipitation in this mid-elevation grassland.
DOI:10.1007/BF00389004URLPMID:28311731 [本文引用: 3]
Small precipitation events account for a large proportion of the precipitation received in semiarid regions, and their potential ecological importance has previously been ignored. We investigated the effect of a small rainfall event (5 mm) upon Bouteloua gracilis, the dominant grass species of the central and southern Great Plains of North America. An effect of a small event on leaf water potential and leaf conductance to water vapor was observed in less than 12 h and lasted for up to two days.The remarkable short response time of Bouteloua gracilis to a rainfall stimulus enables this species to utilize small events and, therefore, may influence its persistence as a dominant species in the steppe region.We proposed response times to be one of the major species characteristics determining capacity for utilizing different portions of the water resource of the region. We suggest that small precipitation events are ecologically significant and a qualitatively distinct resource for ecosystems in semiarid regions.
DOI:10.1093/ee/nvz074URLPMID:31232452 [本文引用: 2]
Terrestrial arthropods are a critical component of rangeland ecosystems that convert primary production into resources for higher trophic levels. During spring and summer, select arthropod taxa are the primary food of breeding prairie birds, of which many are imperiled in North America. Livestock grazing is globally the most widespread rangeland use and can affect arthropod communities directly or indirectly through herbivory. To examine effects of management on arthropod community structure and avian food availability, we studied ground-dwelling arthropods on grazed and ungrazed sagebrush rangelands of central Montana. From 2012 to 2015, samples were taken from lands managed as part of a rest-rotation grazing program and from idle lands where livestock grazing has been absent for over a decade. Bird-food arthropods were twice as prevalent in managed pastures despite the doubling of overall activity-density of arthropods in idle pastures. Activity-density on idled lands was largely driven by a tripling of detritivores and a doubling in predators. Predator community structure was simplified on idled lands, where Lycosid spiders increased by fivefold. In contrast, managed lands supported a more diverse assemblage of ground-dwelling arthropods, which may be particularly beneficial for birds in these landscapes if, for example, diversity promotes temporal stability in this critical food resource. Our results suggest that periodic disturbance may enhance arthropod diversity, and that birds may benefit from livestock grazing with periodic rest or deferment.
DOI:10.1007/s00442-004-1520-8URLPMID:15034778 [本文引用: 3]
In arid/semi-arid ecosystems, biological resources, such as water, soil nutrients, and plant biomass, typically go through periods of high and low abundance. Short periods of high resource abundance are usually triggered by rainfall events, which, despite of the overall scarcity of rain, can saturate the resource demand of some biological processes for a time. This review develops the idea that there exists a hierarchy of soil moisture pulse events with a corresponding hierarchy of ecological responses, such that small pulses only trigger a small number of relatively minor ecological events, and larger pulses trigger a more inclusive set and some larger ecological events. This framework hinges on the observation that many biological state changes, where organisms transition from a state of lower to higher physiological activity, require a minimal triggering event size. Response thresholds are often determined by the ability of organisms to utilize soil moisture pulses of different infiltration depth or duration. For example, brief, shallow pulses can only affect surface dwelling organisms with fast response times and high tolerance for low resource levels, such as some species of the soil micro-fauna and -flora, while it takes more water and deeper infiltration to affect the physiology, growth or reproduction of higher plants. This review first discusses how precipitation, climate and site factors translate into soil moisture pulses of varying magnitude and duration. Next, the idea of the response hierarchy for ecosystem processes is developed, followed by an exploration of the possible evolutionary background for the existence of response thresholds to resource pulses. The review concludes with an outlook on global change: does the hierarchical view of precipitation effects in ecosystems provide new perspectives on the future of arid/semiarid lands?
DOI:10.1007/s00442-004-1683-3URLPMID:15300489 [本文引用: 1]
DOI:10.2307/2259192URL [本文引用: 1]
DOI:10.1007/s00442-003-1403-4URLPMID:14576930 [本文引用: 1]
Plant species and functionally related species groups from arid and semi-arid habitats vary in their capacity to take up summer precipitation, acquire nitrogen quickly after summer precipitation, and subsequently respond with ecophysiological changes (e.g. water and nitrogen relations, gas exchange). For species that respond ecophysiologically, the use of summer precipitation is generally assumed to affect long-term plant growth and thus alter competitive interactions that structure plant communities and determine potential responses to climate change. We assessed ecophysiological and growth responses to large short-term irrigation pulses over one to three growing seasons for several widespread Great Basin and northern Mojave Desert shrub species: Chrysothamnus nauseosus, Sarcobatus vermiculatus, Atriplex confertifolia, and A. parryi. We compared control and watered plants in nine case studies that encompassed adults of all four species, juveniles for three of the species, and two sites for two of the species. In every comparison, plants used summer water pulses to improve plant water status or increase rates of functioning as indicated by other ecophysiological characters. Species and life history stage responses of ecophysiological parameters (leaf N, delta15N, delta13C, gas exchange, sap flow) were consistent with several previous short-term studies. However, use of summer water pulses did not affect canopy growth in eight out of nine comparisons, despite the range of species, growth stages, and site conditions. Summer water pulses affected canopy growth only for C. nauseosus adults. The general lack of growth effects for these species might be due to close proximity of groundwater at these sites, co-limitation by nutrients, or inability to respond due to phenological canalization. An understanding of the connections between short-term ecophysiological responses and growth, for different habitats and species, is critical for determining the significance of summer precipitation for desert community dynamics.
DOI:10.1002/ecy.1703URLPMID:27987317 [本文引用: 1]
A proposed refinement to the stress-gradient hypothesis requires consideration of the strategies of the interacting species and the characteristics of the stress factors. While the strength and direction of these interactions can be predicted for different ecosystems, this idea remains largely untested in the field. We performed a manipulative field experiment complemented with a descriptive study to test the predictions in a natural setting that represents the extreme end of a precipitation gradient. There, wind driven desiccation and water availability are the main stressors (non-resource and resource-based stresses, respectively). We evaluated the interaction between the shrub and grasses that are dominant in the Patagonian steppe. The species had differences in morpho-functional traits and drought tolerance that fit into the C-S axis of Grime's strategies. We experimentally separated root zones to limit direct competition for soil moisture and reduce the resource-based stress on grasses. We also manipulated the distance to shrubs to evaluate non-resource stress amelioration by canopies (e.g., sun and wind) on grasses. Finally, we evaluated the distribution of naturally established C and S grasses in the neighborhood of C and S shrubs to infer process-pattern relationships. Our growth data coincide to a large degree to the predictions. We found positive effects on the growth of beneficiaries when stress was non-resource based and when strategies differed (i.e., Cshrub -Sgrass and Sshrub -Cgrass ). We also found strong negative effects when the abiotic stress was driven by water, particularly on C grasses. Additionally, shrubs only increased the survival of grasses when strategies differed (i.e., Cshrub -Sgrass and Sshrub -Cgrass ). Our manipulative and descriptive study supported previous results that showed that stress-tolerant species are important for the persistence of competitive species at high stress. While the applicability and generality of these predictions remains to be tested with more field experiments, some ecological factors, such as stress types and species traits, can explain much of the variation in how dominant shrubs and grasses interact in this extreme arid environment. Moreover, this framework could be extended to specifically test the importance of facilitation under different levels of stress.
DOI:10.1111/jec.2007.95.issue-4URL [本文引用: 1]
DOI:10.5846/stxbURL [本文引用: 1]
DOI:10.5846/stxbURL [本文引用: 1]
DOI:10.1016/j.jaridenv.2004.01.004URL [本文引用: 1]
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DOI:10.4014/jmb.1911.11003URLPMID:31838828 [本文引用: 1]
Deinococcus actinosclerus BM2T (GenBank: KT448814) is a radio-resistant bacterium that is newly isolated from the soil of a rocky hillside in Seoul. As an extremophile, D. actinosclerus BM2T may possess anti-inflammatory properties that may be beneficial to human health. In this study, we evaluated the anti-inflammatory effects of BM2U, an aqueous extract of D. actinosclerus BM2T, on lipopolysaccharide (LPS)-mediated inflammatory responses in RAW264.7 macrophage cells. BM2U showed antioxidant capacity, as determined by the DPPH radical scavenging (IC50 = 349.3 μg/mL) and ORAC (IC50 = 50.24 μg/mL) assays. At 20 μg/mL, BM2U induced a significant increase in heme oxygenase-1 (HO-1) expression (p <0.05). BM2U treatment (0.2 - 20 μg/mL) significantly suppressed LPS-induced increase in the mRNA expression of proinflammatory cytokines tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, and IL-6 (p <0.05). BM2U treatment also suppressed the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2), which are involved in the production of inflammatory mediators. BM2U treatment also inhibited the activation of nuclear factor-κB (NF-κB) and mitogen-activated protein kinases (MAPKs): JNK, ERK, and p-38 (p <0.05). Collectively, BM2U exhibited anti-inflammatory potential that can be exploited in attenuating inflammatory responses.
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URLPMID:21548315 [本文引用: 1]
Precipitation events in arid/semi-arid environment are usually occurred in &quot;pulses&quot;, with highly variable arrival time, duration, and intensity. These discrete and largely unpredictable features may lead to the pulsed availability of soil water and nutrients in space and time. Resources pulses can affect the life history traits and behaviors at individual level, numerous responses at population level, and indirect effects at community level. This paper reviewed the most recent research advances in the related fields from the aspects of the effects of resources pulses and the responses of ecosystems. It was emphasized that the following issues are still open, e.g., the effects of the pulsed features of resources availability on ecosystems, the discrepancy among the effects of resources pulses in different ecosystems, the eco-hydrological mechanisms that determine the persistence of pulsed resources effects, and the effects of the pulsed resources availability on ecosystem processes. Given the potential global climate and precipitation pattern change, an important research direction in the future is to determine how the resources pulses affect the ecosystem responses at different scales under different climate scenarios.
URLPMID:21548315 [本文引用: 1]
Precipitation events in arid/semi-arid environment are usually occurred in &quot;pulses&quot;, with highly variable arrival time, duration, and intensity. These discrete and largely unpredictable features may lead to the pulsed availability of soil water and nutrients in space and time. Resources pulses can affect the life history traits and behaviors at individual level, numerous responses at population level, and indirect effects at community level. This paper reviewed the most recent research advances in the related fields from the aspects of the effects of resources pulses and the responses of ecosystems. It was emphasized that the following issues are still open, e.g., the effects of the pulsed features of resources availability on ecosystems, the discrepancy among the effects of resources pulses in different ecosystems, the eco-hydrological mechanisms that determine the persistence of pulsed resources effects, and the effects of the pulsed resources availability on ecosystem processes. Given the potential global climate and precipitation pattern change, an important research direction in the future is to determine how the resources pulses affect the ecosystem responses at different scales under different climate scenarios.
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Ecosystem stability and compensatory effects in the Inner Mongolia grassland
1
2004
... 该羊草样地建于1979年, 面积为600 m × 300 m, 本研究资料为1982-2015年的样地观测数据, 以10年为周期(A01-A10)监测群落的地上生物量(
Primary production and rain use efficiency across a precipitation gradient on the Mongolia Plateau
1
2008
... 近些年来, 国内外****对气候变化背景下草原生态系统的植被生长等方面开展了大量的研究, 普遍认为降水是影响植被生长和地上初级生产力的重要因子(
羊草与大针茅根系构型对水分梯度响应的比较研究
1
2019
... 羊草与大针茅种群是研究区的主要建群种, 尽管它们广泛共生, 有着相似的光合生理和生活史, 但它们对降水的变化表现出截然不同的反应.本研究中发现以羊草为代表的多年生根茎禾类草与≥35 mm的降水发生频率与贡献率均呈显著的正相关关系, 而以大针茅为代表的多年生丛生禾草对水分梯度的响应并不显著, 这可能与两种植物的根系构型有关.
羊草与大针茅根系构型对水分梯度响应的比较研究
1
2019
... 羊草与大针茅种群是研究区的主要建群种, 尽管它们广泛共生, 有着相似的光合生理和生活史, 但它们对降水的变化表现出截然不同的反应.本研究中发现以羊草为代表的多年生根茎禾类草与≥35 mm的降水发生频率与贡献率均呈显著的正相关关系, 而以大针茅为代表的多年生丛生禾草对水分梯度的响应并不显著, 这可能与两种植物的根系构型有关.
Controls on soil respiration in semiarid soils
1
2004
... 水分是干旱半干旱区植被生长发育的主要限制因子(
半干旱草原主要植物光能和水分利用特征的研究
1
2001
... 羊草与大针茅种群是研究区的主要建群种, 尽管它们广泛共生, 有着相似的光合生理和生活史, 但它们对降水的变化表现出截然不同的反应.本研究中发现以羊草为代表的多年生根茎禾类草与≥35 mm的降水发生频率与贡献率均呈显著的正相关关系, 而以大针茅为代表的多年生丛生禾草对水分梯度的响应并不显著, 这可能与两种植物的根系构型有关.
半干旱草原主要植物光能和水分利用特征的研究
1
2001
... 羊草与大针茅种群是研究区的主要建群种, 尽管它们广泛共生, 有着相似的光合生理和生活史, 但它们对降水的变化表现出截然不同的反应.本研究中发现以羊草为代表的多年生根茎禾类草与≥35 mm的降水发生频率与贡献率均呈显著的正相关关系, 而以大针茅为代表的多年生丛生禾草对水分梯度的响应并不显著, 这可能与两种植物的根系构型有关.
Elevated CO2 effects on semi-arid grassland plants in relation to water availability and competition
1
2010
... 水分是干旱半干旱区植被生长发育的主要限制因子(
Response of a grassland cactus to frequency and size of rainfall events in a North American shortgrass steppe
1
1996
... 在许多研究中, ≤5 mm的降水被认为是无效降水, 因其仅能润湿表层土壤, 不能到达植物根系(
Climate extremes: Observations, modeling, and impacts
2
2000
... 水分是干旱半干旱区植被生长发育的主要限制因子(
... ;
Productivity responses to altered rainfall patterns in a C4-dominated grassland
2
2003
... 近些年来, 国内外****对气候变化背景下草原生态系统的植被生长等方面开展了大量的研究, 普遍认为降水是影响植被生长和地上初级生产力的重要因子(
... 本研究发现, 小降水事件(I)的增多降低了群落中多年生杂类草的地上生物量, 大降水事件(VI- VIII)的波动会对多年生根茎禾类草和多年生杂类草的地上生物量产生显著影响, 而降水变化对其他几个植物功能型均无显著影响, 这可能与不同植物功能型获得水资源的策略不同有关.
气候变化背景下中国北方干湿区降水资源变化特征分析
1
2015
... 通过分析历史数据, 并参考中国气象局降水等级标准(
气候变化背景下中国北方干湿区降水资源变化特征分析
1
2015
... 通过分析历史数据, 并参考中国气象局降水等级标准(
Changes in the probability of heavy precipitation: Important indicators of climatic change
1
1999
... 水分是干旱半干旱区植被生长发育的主要限制因子(
毛乌素沙地沙丘土壤含水量特点——兼论老固定沙地上油蒿衰退原因
1
2000
... 在许多研究中, ≤5 mm的降水被认为是无效降水, 因其仅能润湿表层土壤, 不能到达植物根系(
毛乌素沙地沙丘土壤含水量特点——兼论老固定沙地上油蒿衰退原因
1
2000
... 在许多研究中, ≤5 mm的降水被认为是无效降水, 因其仅能润湿表层土壤, 不能到达植物根系(
Biotic mechanisms of community stability shift along a precipitation gradient
1
2014
... 近些年来, 国内外****对气候变化背景下草原生态系统的植被生长等方面开展了大量的研究, 普遍认为降水是影响植被生长和地上初级生产力的重要因子(
2
2013
... 水分是干旱半干旱区植被生长发育的主要限制因子(
... 研究区位于内蒙古锡林郭勒草原自然保护区, 靠近中国科学院内蒙古草原生态系统定位研究站(IMGERS, 43.63° N, 116.7° E, 海拔1 187 m).该区域是中亚半干旱草原生态系统的一部分, 属大陆性温带气候(
Quantifying grazing intensities using geographic information systems and satellite remote sensing in the Xilingol steppe region, Inner Mongolia, China
1
2005
... 近些年来, 国内外****对气候变化背景下草原生态系统的植被生长等方面开展了大量的研究, 普遍认为降水是影响植被生长和地上初级生产力的重要因子(
Consequences of more extreme precipitation regimes for terrestrial ecosystems
2
2008
... 水分是干旱半干旱区植被生长发育的主要限制因子(
... 近些年来, 国内外****对气候变化背景下草原生态系统的植被生长等方面开展了大量的研究, 普遍认为降水是影响植被生长和地上初级生产力的重要因子(
Frequency and extent of water limitation to primary production in a mesic temperate grassland
1
2001
... 水分是干旱半干旱区植被生长发育的主要限制因子(
Reconciling inconsistencies in precipitation-productivity relationships: Implications for climate change
1
2017
... 近些年来, 国内外****对气候变化背景下草原生态系统的植被生长等方面开展了大量的研究, 普遍认为降水是影响植被生长和地上初级生产力的重要因子(
Rainfall variability, carbon cycling, and plant species diversity in a mesic grassland
1
2002
... 水分是干旱半干旱区植被生长发育的主要限制因子(
Success of C4 photosynthesis in the field: Lessons from communities dominated by C4 plants
1
1999
... 本研究发现, 小降水事件(I)的增多降低了群落中多年生杂类草的地上生物量, 大降水事件(VI- VIII)的波动会对多年生根茎禾类草和多年生杂类草的地上生物量产生显著影响, 而降水变化对其他几个植物功能型均无显著影响, 这可能与不同植物功能型获得水资源的策略不同有关.
Variation among biomes in temporal dynamics of aboveground primary production
1
2001
... 水分是干旱半干旱区植被生长发育的主要限制因子(
Long-term forage production of north American shortgrass steppe
1
1992
... 在许多研究中, ≤5 mm的降水被认为是无效降水, 因其仅能润湿表层土壤, 不能到达植物根系(
Long-term vegetation dynamics driven by climatic variations in the Inner Mongolia grassland: Findings from 30-year monitoring
1
2015
... 该羊草样地建于1979年, 面积为600 m × 300 m, 本研究资料为1982-2015年的样地观测数据, 以10年为周期(A01-A10)监测群落的地上生物量(
黑河流域荒漠区降水格局及其脉动特征
1
2010
... 降水变化可能仅仅是湿润土壤表面的小事件, 也可能是影响深层土壤水分动态、周期长达数十年的大事件.有研究表明, 2 mm的小降水事件只会引起表层土壤微生物的活动, 导致土壤硝态氮增加或发生短暂的分解变化, 大于3 mm的降水可提高某些高大植物的碳同化速率或者土壤结皮生物的净碳收益, 而大于25 mm的降水则可能引起多数荒漠植物萌发.因此, 研究干旱地区降水脉冲量级特征和变化趋势可更精细地了解荒漠植被与降水之间的关系(
黑河流域荒漠区降水格局及其脉动特征
1
2010
... 降水变化可能仅仅是湿润土壤表面的小事件, 也可能是影响深层土壤水分动态、周期长达数十年的大事件.有研究表明, 2 mm的小降水事件只会引起表层土壤微生物的活动, 导致土壤硝态氮增加或发生短暂的分解变化, 大于3 mm的降水可提高某些高大植物的碳同化速率或者土壤结皮生物的净碳收益, 而大于25 mm的降水则可能引起多数荒漠植物萌发.因此, 研究干旱地区降水脉冲量级特征和变化趋势可更精细地了解荒漠植被与降水之间的关系(
Landscape Ecology: Function and Management: Principles from Australia?s Rangelands
2
1996
... 在干旱与半干旱区, 降水事件通常以脉动的形式发生, 降水发生时间、持续时间、强度等参数具有较大的变异性(
... 以往研究发现, 降水脉动可以导致土壤水分与养分等资源也呈脉动状态, 进而影响着种群动态、群落变化等生态系统过程(
春季小降雨事件对科尔沁沙地尖头叶藜萌发的影响
1
2015
... 近些年来, 国内外****对气候变化背景下草原生态系统的植被生长等方面开展了大量的研究, 普遍认为降水是影响植被生长和地上初级生产力的重要因子(
春季小降雨事件对科尔沁沙地尖头叶藜萌发的影响
1
2015
... 近些年来, 国内外****对气候变化背景下草原生态系统的植被生长等方面开展了大量的研究, 普遍认为降水是影响植被生长和地上初级生产力的重要因子(
Climatic controls of aboveground net primary production in semi-arid grasslands along a latitudinal gradient portend low sensitivity to warming
1
2015
... 近些年来, 国内外****对气候变化背景下草原生态系统的植被生长等方面开展了大量的研究, 普遍认为降水是影响植被生长和地上初级生产力的重要因子(
Ecophysiological responses of two dominant grasses to altered temperature and precipitation regimes
1
2009
... 本研究发现, 小降水事件(I)的增多降低了群落中多年生杂类草的地上生物量, 大降水事件(VI- VIII)的波动会对多年生根茎禾类草和多年生杂类草的地上生物量产生显著影响, 而降水变化对其他几个植物功能型均无显著影响, 这可能与不同植物功能型获得水资源的策略不同有关.
C3与C4植物的环境调控
1
2004
... 水分是干旱半干旱区植被生长发育的主要限制因子(
C3与C4植物的环境调控
1
2004
... 水分是干旱半干旱区植被生长发育的主要限制因子(
Water-mediated responses of ecosystem carbon fluxes to climatic change in a temperate steppe
4
2007
... 水分是干旱半干旱区植被生长发育的主要限制因子(
... 以往研究发现, 降水脉动可以导致土壤水分与养分等资源也呈脉动状态, 进而影响着种群动态、群落变化等生态系统过程(
... 发现降水脉动可能是干旱与半干旱生态系统演替的核心驱动力和不同植物功能类型共存的重要原因.国内外****围绕降水脉动发生时间、强度及其对生态系统的影响等方面, 先后提出了脉动- 存贮理论(Pulse-Reserve)(
... )等理论模型.其中, 脉动-存贮理论是干旱与半干旱区生态系统研究中广泛应用的一个理论.该理论认为降水脉动能够触发植物生长脉动与碳和能量储存之间的关系, 这种存贮能力在两次降水间隔期内处于休眠状态, 此时生态系统初级生产力不再增长(
Desert ecosystems: Environment and producers
2
1973
... 以往研究发现, 降水脉动可以导致土壤水分与养分等资源也呈脉动状态, 进而影响着种群动态、群落变化等生态系统过程(
... 在许多研究中, ≤5 mm的降水被认为是无效降水, 因其仅能润湿表层土壤, 不能到达植物根系(
Rainfall partitioning within semiarid juniper communities: Effects of event size and canopy cover
1
2006
... 在许多研究中, ≤5 mm的降水被认为是无效降水, 因其仅能润湿表层土壤, 不能到达植物根系(
1960-2012年内蒙古降水集中度和降水集中期时空变化
1
2016
... 为研究年内降水分配不均匀性特征, 或年内降水分配情况, 本文采用
1960-2012年内蒙古降水集中度和降水集中期时空变化
1
2016
... 为研究年内降水分配不均匀性特征, 或年内降水分配情况, 本文采用
Modifying the “pulse-reserve” paradigm for deserts of North America: Precipitation pulses, soil water, and plant responses
3
2004
... 以往研究发现, 降水脉动可以导致土壤水分与养分等资源也呈脉动状态, 进而影响着种群动态、群落变化等生态系统过程(
... 在许多研究中, ≤5 mm的降水被认为是无效降水, 因其仅能润湿表层土壤, 不能到达植物根系(
... 本研究发现, 小降水事件(I)的增多降低了群落中多年生杂类草的地上生物量, 大降水事件(VI- VIII)的波动会对多年生根茎禾类草和多年生杂类草的地上生物量产生显著影响, 而降水变化对其他几个植物功能型均无显著影响, 这可能与不同植物功能型获得水资源的策略不同有关.
Effects of long-term rainfall variability on evapotranspiration and soil water distribution in the Chihuahuan Desert: A modeling analysis
2
2000
... 近些年来, 国内外****对气候变化背景下草原生态系统的植被生长等方面开展了大量的研究, 普遍认为降水是影响植被生长和地上初级生产力的重要因子(
... 以往研究发现, 降水脉动可以导致土壤水分与养分等资源也呈脉动状态, 进而影响着种群动态、群落变化等生态系统过程(
Precipitation timing and magnitude differentially affect aboveground annual net primary productivity in three perennial species in a Chihuahuan Desert grassland
1
2009
... 近些年来, 国内外****对气候变化背景下草原生态系统的植被生长等方面开展了大量的研究, 普遍认为降水是影响植被生长和地上初级生产力的重要因子(
Precipitation magnitude and timing differentially affect species richness and plant density in the sotol grassland of the Chihuahuan Desert
2010
Small rainfall events: An ecological role in semiarid regions
3
1982
... 通过分析历史数据, 并参考中国气象局降水等级标准(
... 在干旱与半干旱区, 降水事件通常以脉动的形式发生, 降水发生时间、持续时间、强度等参数具有较大的变异性(
... )一致, 也与
Primary production of the central grassland region of the United States
2
1988
... 水分是干旱半干旱区植被生长发育的主要限制因子(
... 以往研究发现, 降水脉动可以导致土壤水分与养分等资源也呈脉动状态, 进而影响着种群动态、群落变化等生态系统过程(
Hierarchy of responses to resource pulses in arid and semi-arid ecosystems
3
2004
... 水分是干旱半干旱区植被生长发育的主要限制因子(
... ;
... 近些年来, 国内外****对气候变化背景下草原生态系统的植被生长等方面开展了大量的研究, 普遍认为降水是影响植被生长和地上初级生产力的重要因子(
Thresholds, memory, and seasonality: Understanding pulse dynamics in arid/semi-arid ecosystems
1
2004
... 水分是干旱半干旱区植被生长发育的主要限制因子(
The structure and function of ten western north American grasslands: I. Abiotic and vegetational characteristics
1
1978
... 本研究发现, 小降水事件(I)的增多降低了群落中多年生杂类草的地上生物量, 大降水事件(VI- VIII)的波动会对多年生根茎禾类草和多年生杂类草的地上生物量产生显著影响, 而降水变化对其他几个植物功能型均无显著影响, 这可能与不同植物功能型获得水资源的策略不同有关.
Extensive summer water pulses do not necessarily lead to canopy growth of Great Basin and northern Mojave Desert shrubs
1
2004
... 以往研究发现, 降水脉动可以导致土壤水分与养分等资源也呈脉动状态, 进而影响着种群动态、群落变化等生态系统过程(
Ecological strategies in a Patagonian arid steppe
1
1984
... 本研究发现, 小降水事件(I)的增多降低了群落中多年生杂类草的地上生物量, 大降水事件(VI- VIII)的波动会对多年生根茎禾类草和多年生杂类草的地上生物量产生显著影响, 而降水变化对其他几个植物功能型均无显著影响, 这可能与不同植物功能型获得水资源的策略不同有关.
Intra-seasonal precipitation patterns and above-ground productivity in three perennial grasslands
1
2007
... 近些年来, 国内外****对气候变化背景下草原生态系统的植被生长等方面开展了大量的研究, 普遍认为降水是影响植被生长和地上初级生产力的重要因子(
内蒙古羊草群落、功能群、物种变化及其与气候的关系
1
2013
... 位于内蒙古锡林郭勒典型草原区的中国科学院草原生态系统定位研究站羊草样地自1979年围封以来一直未被利用, 可以认为群落生产力的波动是由气候变化造成的(
内蒙古羊草群落、功能群、物种变化及其与气候的关系
1
2013
... 位于内蒙古锡林郭勒典型草原区的中国科学院草原生态系统定位研究站羊草样地自1979年围封以来一直未被利用, 可以认为群落生产力的波动是由气候变化造成的(
A landscape- scale assessment of steppe degradation in the Xilin River Basin, Inner Mongolia, China
1
2004
... 研究区位于内蒙古锡林郭勒草原自然保护区, 靠近中国科学院内蒙古草原生态系统定位研究站(IMGERS, 43.63° N, 116.7° E, 海拔1 187 m).该区域是中亚半干旱草原生态系统的一部分, 属大陆性温带气候(
Natural savannahs as a transition to the arid zone
2
1971
... 研究区位于内蒙古锡林郭勒草原自然保护区, 靠近中国科学院内蒙古草原生态系统定位研究站(IMGERS, 43.63° N, 116.7° E, 海拔1 187 m).该区域是中亚半干旱草原生态系统的一部分, 属大陆性温带气候(
... 以往研究发现, 降水脉动可以导致土壤水分与养分等资源也呈脉动状态, 进而影响着种群动态、群落变化等生态系统过程(
Degradation and small-scale spatial homogenization of topsoils in intensively-grazed steppes of Northern China
1
2009
... 为研究年内降水分配不均匀性特征, 或年内降水分配情况, 本文采用
长江流域汛期降水集中程度和洪涝关系研究
1
2004
... 为研究年内降水分配不均匀性特征, 或年内降水分配情况, 本文采用
长江流域汛期降水集中程度和洪涝关系研究
1
2004
... 为研究年内降水分配不均匀性特征, 或年内降水分配情况, 本文采用
干旱、半干旱环境降水脉动对生态系统的影响
1
2011
... 以往研究发现, 降水脉动可以导致土壤水分与养分等资源也呈脉动状态, 进而影响着种群动态、群落变化等生态系统过程(
干旱、半干旱环境降水脉动对生态系统的影响
1
2011
... 以往研究发现, 降水脉动可以导致土壤水分与养分等资源也呈脉动状态, 进而影响着种群动态、群落变化等生态系统过程(
降水波动对荒漠草原生产力的影响
1
2014
... 在干旱与半干旱区, 降水事件通常以脉动的形式发生, 降水发生时间、持续时间、强度等参数具有较大的变异性(
降水波动对荒漠草原生产力的影响
1
2014
... 在干旱与半干旱区, 降水事件通常以脉动的形式发生, 降水发生时间、持续时间、强度等参数具有较大的变异性(
准噶尔盆地南缘降水脉冲量级分布及其变化规律
1
2012
... 降水变化可能仅仅是湿润土壤表面的小事件, 也可能是影响深层土壤水分动态、周期长达数十年的大事件.有研究表明, 2 mm的小降水事件只会引起表层土壤微生物的活动, 导致土壤硝态氮增加或发生短暂的分解变化, 大于3 mm的降水可提高某些高大植物的碳同化速率或者土壤结皮生物的净碳收益, 而大于25 mm的降水则可能引起多数荒漠植物萌发.因此, 研究干旱地区降水脉冲量级特征和变化趋势可更精细地了解荒漠植被与降水之间的关系(
准噶尔盆地南缘降水脉冲量级分布及其变化规律
1
2012
... 降水变化可能仅仅是湿润土壤表面的小事件, 也可能是影响深层土壤水分动态、周期长达数十年的大事件.有研究表明, 2 mm的小降水事件只会引起表层土壤微生物的活动, 导致土壤硝态氮增加或发生短暂的分解变化, 大于3 mm的降水可提高某些高大植物的碳同化速率或者土壤结皮生物的净碳收益, 而大于25 mm的降水则可能引起多数荒漠植物萌发.因此, 研究干旱地区降水脉冲量级特征和变化趋势可更精细地了解荒漠植被与降水之间的关系(
