黄土区夏闲期土壤呼吸变化特征及其影响因素

本文以1984年设立在黄土旱塬区长期田间定位试验为平台,于2009年采用动态密闭气室法(Li-8100,USA),监测了不同施肥措施下旱地冬麦种植系统中休闲期(7月至9月)土壤呼吸、10cm土层的温度和含水量变化,研究了休闲期土壤呼吸变化特征及其与环境因子的关系。结果表明:黄土旱塬农田休闲期土壤呼吸速率变化剧烈,最大值为5.05μmol m-2s-1,最小值为0.06μmol m-2s-1,平均值为2.00μmol m-2s-1,变异系数为116.5%;整个休闲期不同施肥处理的土壤呼吸速率大小为:化肥有机肥配施处理(NMP)有机肥处理(M)化肥氮磷处理(NP)化肥氮处理(N)和不施肥处理(CK);2009年7月7日至9月11日间NPM、M、NP、N和CK处理土壤CO2-C排放量分别为2.0、1.6、1.2、0.8和0.8 Mg hm-2;土壤呼吸与土壤水分为极显著抛物线关系(p0.01),可解释55%以上的土壤呼吸变异性;土壤呼吸与土壤温度呈显著线性相关(p0.01),但仅能解释呼吸作用变异性的19%~39%;土壤呼吸对耕作的响应强度与微生物量碳极显著线性正相关(p0.01),与土壤有机碳显著线性正相关(p0.05),与全氮、可溶性碳无明显关系(p0.05);降雨对土壤呼吸的促进或抑制主要取决于降雨前的土壤水分状况。长期水分亏缺降雨,降雨可明显促进土壤呼吸,而土壤水分充足时,降雨抑制土壤呼吸,其影响大小与土壤有机碳、全氮、土壤可溶性碳和微生物量碳密切相关。休闲期土壤呼吸受土壤水分、土壤干湿变化、土壤温度、翻耕及土壤有机碳水平等因素的影响。

Dynamics of soil respiration and its affecting factors in arid upland fields during summer fallow season on the Loess Plateau

Based on long-term fertilization experiments in the arid-highland on the Loess Plateau started form 1984, we measured soil respiration, soil temperature and moisture at a depth of 10cm during the fallow stage under different fertilizations by LI-8100 automated soil CO2 flux system from July to September in 2009, to analyze the relationship between soil respiration and environmental factors. The results showed that at the fallow stage, soil respiration has higher variation of 116.5% with the mean value of 2.00mol m-2 s-1, while max and min value were 5.05 mol m-2 s-1 and 0.06 mol m-2 s-1, respectively; For the whole of fallow stage, the order of soil respiration was NPM > M > NP > N and CK, the emission was 780 g m-2, 651 g m-2, 477 g m-2, 324 g m-2 and 312 g m-2, respectively; Soil respiration showed high significantly (P<0.01) connection with soil moisture with R2 of more than 55%, while the relationship with soil temperature was significant (P<0.05) excluding the treatment M; the increasing extent of ploughing for soil respiration was significant (P<0.05) relation with soil organic carbon, total nitrogen, soil dissolved organic carbon and soil microbial biomass carbon; the effects of precipitation on soil respiration depends the soil moisture before rain. At the drought stage, precipitation could accelerate soil respiration, while washy, precipitation could restrain soil respiration, and the effecting intensity was content with soil organic carbon, total nitrogen, oil dissolved organic carbon and soil microbial biomass carbon. All this showed that soil respiration may be effected by soil temperature, soil moisture, precipitation, ploughing and soil organic carbon.