不同生态系统土壤生化特征及其与土壤呼吸和N2O排放的关系

通过室内培养实验,研究了不同生态系统土壤生化特征及其对土壤呼吸和N2O排放的影响.结果表明,不同生态系统土壤的生化特征不同,土壤呼吸和N2O排放也不相同.一般果园细菌数量最多,草地放线菌数量最多,林地真菌数量最多,而竹园细菌放线菌数量最少,果园真菌最少;微生物碳氮含量一般果园>林地>农田.相关分析表明细菌数量与微生物碳氮呈显著正相关,放线菌数量与土壤有机碳和全氮含量呈极显著正相关(P<0.01),而真菌数量仅与全氮含量呈显著正相关(P<0.05).土壤呼吸累积排放量从高到低为果园>竹林>农田>林地>草地.N2O累积排放量为农田>果园>草地>林地>竹林.土壤呼吸与细菌、微生物碳氮呈显著正相关(P<0.05);土壤的N2O排放与三大微生物、铵态氮呈显著正相关(P<0.05).逐步回归分析表明土壤呼吸主要取决于土壤细菌数量和pH的变化;土壤N2O排放主要取决于土壤细菌数量和铵态氮含量的变化.

Soil Biochemical Characteristics in Different Ecological Systems and Their Relationships with Soil Respiration and N2O Emission

The biochemical characteristics of soil in different ecological system and their effects on soil respiration(CO₂) and nitrous oxide (N₂O) emission were investigated by an indoor incubation method. The results showed that the biochemical characteristics of soils in the different ecosystems and CO₂ and N₂O emissions from different soils greatly varied with each other. In general, the highest abundance of bacteria was found in the orchard soil, the highest abundance of actinomycetes occurred in the meadows and the highest abundance of fungi appeared in the woodlands. The abundance of bacteria or actinomycetes in the bamboo soil was the lowest among all soils, and the orchard soil had the lowest content of fungi. The contents of soil microbial biomass carbon and nitrogen generally followed the order of orchard soil> woodland > cropland. Moreover, cumulative CO₂ and N₂O emissions from the different soils followed the order of orchard soil> bamboo soil > farmland > woodland > grassland and farmland > orchard > grassland> woodland > bamboo soil, respectively. Correlation analysis indicated that there was positive correlations between the abundance of soil bacteria and the contents of microbial biomass carbon and nitrogen, as well as between the abundance of soil fungi and the soil total nitrogen content (P<0.05), while the abundance of soil actinomycosis was positively correlated with soil organic carbon and total nitrogen contents (P<0.01). The soil bacteria, microbial carbon and nitrogen had a significant positive impact on soil respiration (P<0.05), and soil bacteria, actinomycetes, fungi and ammonium nitrogen had the same impact on N₂O emissions (P<0.05). Stepwise regression analysis suggested that soil respiration could be quantitatively determined by a linear combination of soil bacteria and soil pH, while N₂O emission was mainly dependent on the values of soil bacteria and ammonium nitrogen.