土地利用方式的改变对土壤呼吸及土壤微生物生物量的影响

土壤呼吸释放的CO2与土壤微生物生物量碳是全球碳循环中最为活跃的部分.作者对南京林业大学下蜀实习林场内天然次生栎林、马尾松人工林、毛竹林、板栗经济林和农田5种土地利用类型的土壤呼吸速率及土壤微生物生物量进行了测定,并分析了土地利用方式和各种土壤理化性质对土壤呼吸速率及土壤微生物生物量的影响.研究结果表明:①在5种不同土地利用类型中,农田的土壤呼吸速率显著大于马尾松林、栎林和毛竹林;板栗经济林的土壤呼吸速率显著大于毛竹林和马尾松林;其他各土地利用类型之间的土壤呼吸速率均无显著性差异.②在5种不同土地利用类型中,马尾松林的土壤微生物生物量显著小于农田、板栗经济林和毛竹林;农田的土壤微生物生物量显著大于栎林;其他各土地利用类型之间的土壤微生物生物量均无显著差异.③土壤呼吸速率与土壤微生物生物量、土壤温度(尤其是5cm深土壤温度)、土壤全钙含量、土壤全磷含量以及土壤碳氮比有显著相关关系;而与土壤全碳、全氮、土壤pH值等因子相关性不大.④土壤微生物生物量与土壤全钙含量、土壤全磷含量有显著相关关系;而与土壤pH值、土壤湿度等因子无显著相关关系.研究结果还表明:森林变为农田可能潜在地增加土壤CO2的释放;该地区土壤中磷的含量和有效性可能是限制土壤微生物生物量的重要因子.

Influence of land-use change on soil respiration and soil microbial biomass

Soil respiration is an important approach to study global carbon cycling, and soil microbial biomass is the active part of adjusting chemical process in terrestrial ecology system. They are both the sensitive indices reflecting the land-use change. There is a profound and consistent impact on predicting the direction and rate of carbon flow and global carbon cycling to understand the influence of land-use change on soil CO_2 emission and soil microbial biomass. In this study, the authors investigated the effects of soil conditions on soil respiration and soil microbial biomass in five different land-use types (oak, pine plantation, bamboo plantation, chestnut and cropland) in Xiashu Forest Experimental Site in Jiangsu Province, east China. Soil respiration, soil microbial biomass, soil temperature, soil moisture and some other soil physical and chemical properties were measured. The results showed that: 1) the soil respiration rate in cropland was significantly higher than that of pine, oak, and bamboo forests; the soil respiration rate in chestnut was significantly higher than that in pine and bamboo forests; 2) the soil microbial biomass in pine plantation was significantly lower than that in cropland, chestnut and bamboo forests; the soil microbial biomass in cropland was significantly higher than that in oak forest; 3) the soil respiration was strongly positively correlated with soil microbial biomass, soil temperature, soil calcium and soil phosphor concentration, however, strongly negatively correlated with the ratio of soil carbon and nitrogen; and 4) the soil microbial biomass was strongly positively correlated with soil calcium and soil phosphor concentration, but not soil pH value, soil moisture, the ratio of soil carbon and nitrogen, soil carbon and soil nitrogen concentration. Our results indicate that: 1) the land-use conversion from forestland to cropland might potentially increase the release of soil CO_2; 2) the concentration and availability of the phosphor in the area might be one of the factors controlling soil microbial biomass.