Effects Of Three Soil Organisms And Their Interactions On Soil Carbon Dynamics In Typical Forests,Yunnan,China

Soil carbon pool is the largest carbon pool in terrestrial ecosystems.Soil carbon emission directly affects the global carbon cycle and climate change.Controlling soil carbon emission could reduce atmospheric carbon dioxide and eliminate global climate change.Soil organisms are the engine of material circulation,energy flow and information transmission in soil ecosystems,which plays an important role in maintaining the stability of ecosystem structure and function.Soil organisms and their interactions could affect soil respiration and regulate carbon use efficiency(CUE).Yunnan Province includes various climatic typyes which is a hotspot for biodiversity,however,the effects of soil biotic factors and abiotic factors on forest soil respiration and microbial CUE remains unclear.Therefore,three typical soil organisms(bacteria,fungi,nematodes)and three forest soils of different climatic types(tropical forest,subtropical forest,and temperate forest)in Yunnan were selected to explore the impacts of soil organisms and their interactions on soil respiration and carbon dynamics.The microcosm experiments combined soil organisms and climatic types were conducted,and soil physico-chemical properties,respiration and microbial biomass were measured in lab.The results show that:(1)The order of background pH was tropical forest soil(6.30±0.10)>temperate forest soil(4.70±0.13)>subtropical forest soil(3.97±0.16),the order of soil organic carbon and total nitrogen were subtropical forest soil(SOC:123.35±10.42 g.kg^-1,TN:6.97±0.11 g.kg^-1)>temperate forest soil(SOC:93.54±3.76g.kg^-1,TN:5.23±0.06 g.kg^-1)>tropical forest soil(SOC:35.88±1.76 g.kg^-1,TN:2.85±0.11 g.kg^-1);(2)The changes of soil biological respiration rates were different among three forests:in tropical forest,it increased from 0¹2 days and reached maximum at the 12 day,and decreased form 12³0 days;in subtropical forest,it increased from 0³0days;in temperate forest,it remained stable from 0¹8 days,then increased from 18²8days and decreased from 28³0 days;(3)The total amount of soil respiration increased with the increase of temperature,and there was a significant correlation between soil respiration and temperature and C/N(P<0.05);(4)Fungi had significant effect on soil respiration of tropical forest and cold temperate forest,bacteria had significant effect on soil respiration of cold temperate forest(P<0.05),bacteria,fungi and nematodes had no interaction on soil organisms'respiration in three types of forest soil;(5)The soil microbial biomass of tropical and subtropical forests decreased with the increase of population richness.Effects of biotic factors(bacteria,fungi,nematode)and their interactions on soil microbial biomass were different in three forest soils;(6)In the three forest soils,there was no significant difference in microbial CUE among bacteria,fungi and bacteria+fungi.Bacteria,fungi and their interaction had significant effect on microbial CUE in three kinds of forest soil(P<0.001),microbial CUE was significantly related to total nitrogen and total phosphorus content in soil.Above results showed that carbon emission rates and amounts were different among three forests,which were regulated by both biotic(bacteria and fungi)and abiotic(temperature and C/N)factors.The carbon amounts fixed by microbial biomass were mainly controlled by biotic factors and their interactions but not abiotic factors.Microbial CUEs were influenced by both biotic factors(bacteria,fungi and their interaction)and abiotic factors(total nitrogen and total phosphorus).The differences among respiration and biomass of three forests were decreased with the increase of species numbers.Biotic factors and their interactions influenced the chemical properties of tropical and subtropical forests but not temperate forest.The results of this experiment revealed the effects of soil biological interaction on soil respiration,microbial biomass and CUE in different forests,and preliminarily explained the effects of soil biological interaction on soil carbon emission and carbon turnover process.Our study provides scientific evidence for soil biodiversity and ecosystem function,and provides theoretical support for evaluating impact of biodiversity loss on ecosystem function.