摘要
摘要:农田土壤是大气甲烷（CH₄）的重要源和汇，以往关于农田CH₄净交换通量的研究多关注水稻、小麦、玉米等作物，而蔬菜地的观测研究不足。本研究采用静态暗箱-气相色谱法对亚热带地区一块种植包菜的典型露天蔬菜地开展将近1年的田间原位CH₄通量观测，以揭示蔬菜地CH₄净交换通量的周年变化特征及其影响因素，估算CH₄年累积净交换通量，并定量评估CH₄净交换通量的误差。本试验在包菜地的垄上和垄间同时布设观测点进行CH₄通量观测，并对环境因子进行同步测量，观测期为2016年1月1日至12月8日。结果表明，所研究的蔬菜地为大气CH₄的微弱汇，年平均通量为（-9.9±7.0）μg（C）·m^-2·h^-1，全年累积通量为-0.84kg（C）·hm^-2，较高的土壤水分条件和高施氮量可能是导致本研究蔬菜地CH₄吸收较弱的主要原因。全年CH₄累积通量的总体误差为-48%~-16%，其中，由于通量计算方法引起的系统误差会使估算的通量偏低32%，年尺度上的随机误差大小为16%，主要来自CH₄通量的空间差异，因此可适当增加空间重复，以减小空间随机误差。研究还发现垄上的CH₄吸收通量显著高于垄间（P < 0.01），因此在开展农田温室气体通量观测时应兼顾垄上和垄间、种植行和行间等农田管理措施存在显著差异的区域，均布设观测点，避免对通量观测结果造成系统性偏差。
关键词:亚热带蔬菜地/
甲烷/
净交换通量/
静态箱法/
年累积通量/
通量误差
Abstract:Agricultural soil forms an important source-sink of atmospheric methane (CH₄). Studies on net CH₄ flux exchange in agricultural soil have mainly been related to rice, wheat, maize and other crops. However, field studies on vegetable fields have been seldom reported. This study was a year-round situ measurement of CH₄ flux in a typical subtropical vegetable field cultivated with cabbages using the static chamber/gas chromatography technique. The aims were to determine the characteristics of annual net exchange flux of CH₄ and the influencing factors, to estimate annual cumulative CH₄ flux, and to quantify errors in measured CH₄ flux. The CH₄ flux measurements were conducted on ridges and on inter-ridges in vegetable fields for period from January 1^st to December 8^th 2016. Environmental conditions were simultaneously observed during the measurement period. The results showed that vegetable fields constituted a weak sink of atmospheric CH₄, with annual mean flux of (-9.9±7.0) μg(C)·m^-2·h^-1 and annual cumulative flux of -0.84 kg(C)·hm^-2. High soil water content and nitrogen fertilizer application rate were probably the main reasons for the weak uptake of CH₄. The overall error in the annual cumulative CH₄ flux was -48%——16%. The main source of systematic error was in the flux calculation method used, which underestimated the flux by 32% on average. Random error was mainly produced by spatial variations of CH₄ flux, which was estimated at 16% at annual time scale. As a result, it was recommended that high numbers of spatial replications were used in conducting greenhouse gas flux measurements in agricultural soil in order to reduce random error. Another finding of the study was that CH₄ uptake measured on the ridge was significantly (P < 0.01) larger than that measured on the inter-ridge. This implied that it was better to simultaneously place chambers on areas with different field management practices; e.g. ridge and inter-ridge, row and inter-row, which efficiently avoided systematic error in measured flux.
Key words:Subtropical vegetable field/
Methane/
Net flux exchange/
Static chamber technique/
Annual cumulative flux/
Flux error



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