民勤荒漠绿洲过渡带白刺沙堆土壤呼吸空间异质特征

对民勤绿洲-荒漠过渡带广泛分布的白刺(Nitraria tangutorum)灌丛沙堆的土壤呼吸进行了野外观测,研究灌丛沙堆不同部位的土壤呼吸速率在空间和时间上的异质性。结果表明,1)白刺灌丛沙堆上不同部位的土壤呼吸速率日动态在不同的生长时期表现不同:生长初期和生长休眠期土壤呼吸速率日变化基本呈"单峰曲线",但是在生长旺盛期沙堆各部位日动态变化既有"单峰曲线"又有"双峰曲线";2)各部位土壤呼吸速率峰值出现的时间段不一致:生长初期峰值集中出现在11:00左右,旺盛期上午各位点的峰值集中出现在09:00左右,下午峰值在17:00左右出现,休眠期峰值出现在13:00-15:00;3)白刺沙堆各位点土壤呼吸速率对水分含量的敏感性强,在低水分含量(1%)条件下二者相关性强,而在较高水分条件下(1%)二者的相关性降低;4)沙堆上不同部位土壤呼吸速率具有时空异质性:生长初期和休眠期各部位土壤呼吸速率差异不显著(P0.05),旺盛期各部位差异显著(P0.05),不同生长期之间沙堆土壤呼吸速率差异显著(P0.01),平均土壤呼吸大小为生长旺盛期0.53μmol·(m~2·s)~(-1)]生长初期0.24μmol·(m~2·s)~(-1)]生长休眠期0.12μmol·(m2·s)-1],白刺灌丛沙堆不同部位近地表层大气水分条件以及土壤5-20cm的温度和湿度共同导致了沙堆上各个位点土壤呼吸通量具有明显的异质性。

Spatial heterogeneity of soil respiration of Nitraria tangutorum nebkhas in the desert-oasis ecotone of Minqin

Applying Li-8100 soil respiration measurement system,we made field observations on the soil respiration rate of Nitraria tangutorum nebkhas,which is at the stable stage and is largely located in the oasis-desert ecotone at the southern fringe of the Badanjara Desert.The daily change and the spatial heterogeneity of soil respiration at different positions of the nebkhas in different growing periods were analysed and studied.The results showed:1) The daily change of the soil respiration rate of N.tangutorum nebkhas at different positions and at different growing periods were different.It exhibited a "one-peak curve" at the beginning of the growing period and at the dormancy period;but the "one-peak curve" and "double-peak curve" were overlapped in the flourishing period.2) The peaks of soil respiration in different growth periods were different:the peaks of each observed position occurred around 11:00 in the morning at the beginning of the growth period,the peaks of the flourishing period were concentrated around 09:00 and 17:00,and the peaks in the dormancy period occurred between 13:00-15:00 in the afternoon.3) The soil respiration rate of N.tangutorum at different observation points showed a strong sensitivity to water content,the correlation between them was higher at lower water content (＜1％) than at higher water content (＞ 1％).4) There was spatial heterogeneity of soil respiration rate at different positions on the nebkhas:there was a non-significant difference (P ＞0.05) between the soil respiration rate at the beginning of the growing period and in the dormancy period;whereas there was a significant difference (P＜0.01) in the flourishing period.The average soil respiration rate at different growing periods varied significantly,which was ranked as follows:flourishing period 0.53 μmol · (m2 · s)-1]＞at the beginning of the growing period 0.24 μmol · (m2 · s)-1]＞dormancy period 0.12μmol · (m2 · s)-1].The regression analysis showed that the significant spatial heterogeneity in the soil respiration rate was the result of the interaction between the near-surface water condition at different positions,the temperature,and humidity at the depth of 5-20 cm of N.tangutorum.