西藏高原草原化小嵩草草甸生长季土壤微生物呼吸测定

以西藏当雄县草原化小嵩草草甸生态系统为研究为对象,利用Li6400-09对生长季土壤微生物异养呼吸进行了测定。土壤异养呼吸R(h)动态与土壤温度T()变化趋势一致,尤其与5cm地温相关性最强,说明5cm地温是土壤微生物异养呼吸的主要限制因子。在生长季中土壤异养呼吸与5cm土壤温度呈现不同的函数关系:在降水比较集中的雨季(6～8月),函数关系是Rh=0.106exp0.133T;在降水相对较少的旱季(5月,9～10月),函数关系是Rh=0.18exp0.0833T。在生长季中,雨季土壤日异养呼吸量为2.4g CO₂.m-2,雨季异养呼吸总量为219.6g CO₂.m-2,Q 10为3.8;旱季日异养呼吸量为1.8g CO₂.m-2,呼吸总量为160.2gCO 2.m-2,Q 10值为2.3。结果表明,土壤异养呼吸在降水集中的雨季对土壤温度反应更敏感,在生长季不同时期由于降水格局的影响,土壤水分对土壤微生物异养呼吸对温度的响应有调节作用。2004年生长季(5～10月)土壤异养呼吸总量达379.8gCO₂.m-2。

Quantification of Soil Heterotrophic Respiration in the Growth Period of Alpine Steppe-Meadow on the Tibetan Plateau

Qualification of soil heterotrophic respiration is an important component to estimate ecosystem carbon balance.However,it is difficult to directly measure and distinguish it from root respiration.The heterotrophic respiration of Steppe-Kobresia meadow ecosystem was measured in situ in Dangxiong county,central Tibet Autonomous Region by using Li 6400-09 soil chamber.Soil heterotrophic respiration had a strong correlation with soil temperature especially with that at 5cm deep.It indicated that soil temperature at a depth of 5cm was the key factor to determine soil heterotrophic respiration.We analyzed how the soil heterotrophic respiration by soil temperature was affected under different soil moisture regime during the growth period.The variation of soil heterotrophic respiration was differentiated into rainy seaspm(June through August) and dry season(May,September and October).The regression equations between soil heterotrophic respiration and 5cm soil temperature were Rh=0.106exp0.133T in rainy season and Rh=0.18exp0.0833T in dry season respectively.By estimating the soil heterotrophic respiration,the daily mean and total soil heterotrophic respiration were 2.4gCO2·m-2 and 219.6gCO2·m-2 in rainy season,and the value of Q10 was 3.8;While the daily mean and total soil heterotrophic respiration were 1.8gCO2·m-2 and 160.2gCO2·m-2 in dry season,and the value of Q10 was 2.3.The result suggested that soil heterotrophic respiration was more sensitive in rainy season than in dry season during the growth period.The soil moisture caused by rainfall patterns in different months played an important role in regulating the relationship between microbial heterotrophic respiration and soil temperature.Based on established models of soil heterotrophic respiration in relation to soil temperature,the amount of soil heterotrophic respiration was estimated as 379.8gCO2·m-2 in the growth period(May through October) of 2004.