根系分泌物和凋落物对高寒沙化草地土壤微生物的影响

Effects of different root exudates and plant litter input on soil microbial enzyme activities and residues in alpine desertified grassland

根系分泌物和植物凋落物的输入显著改变土壤微生物和土壤碳循环.为探究不同浓度和多样性的根系分泌物以及不同质量的凋落物输入对高寒沙化草地土壤微生物及其残体的影响,人工添加不同碳浓度(0.5 g/kg、1 g/kg)和多样性(3种碳源、9种碳源)的根系分泌物以及垂穗披碱草(Elymus nutans)和野豌豆(Vicia sepium)两种不同质量的凋落物,研究土壤微生物量、4种微生物酶以及土壤氨基糖的变化.结果显示:(1)根系分泌物输入能够增加土壤微生物量碳,提高微生物酶活性,使总微生物残体碳含量增加18%-94%.其中高碳浓度处理更能提高微生物含量(为低碳浓度的1.3倍),促进真菌残体碳的积累;低多样性处理使微生物含量增加显著(比高多样性处理提高48%,P<0.05),提高酶活性的同时促进微生物残体碳的积累.(2)凋落物输入均显著提高微生物及其残体含量,促进微生物周转.其中质量较好(低C/N)的野豌豆凋落物更能刺激微生物量增加(为垂穗披碱草处理的4.1倍),促进微生物残体碳特别是真菌残体碳的积累.本研究表明不同根系分泌物和凋落物输入均对微生物的生长具有激发作用,影响其周转速率,促进微生物源有机碳对土壤有机碳库的固存,其效应与根系分泌物的浓度和成分及凋落物的质量(C/N)显著相关.

The addition of root exudates and plant litter can significantly alter the cycle of soil microorganisms and soil carbon content.In addition to studying the effects of root exudates at different concentrations and diversities and the litter of different qualities on soil microorganisms and their residues in alpine desertified grassland,root exudates of different carbon concentrations(0.5 g/kg,1 g/kg)and sources(3 carbon sources and 9 carbon sources)and litter of two different qualities(Elymus nutans and Vicia sepium)were artificially added to understand the changes in soil microbial biomass,four microbial enzymes,and soil amino sugars.The results showed that:(1)the addition of root exudates can increase carbon content in soil microbial biomass,improve microbial enzyme activity,and increase the total microbial residual carbon content by 18%–94%.Among them,high concentration carbon treatment increased the microbial content(1.3 times of the low carbon concentration)and promoted accumulation in fungal residual carbon,whereas low diversity treatment increased the microbial content significantly(48%higher than that of the high diversity treatment,P<0.05).Therefore,increased enzyme activity promoted carbon accumulation in microbial residues.(2)The input of litter can significantly increase the content of microorganisms and their residues and promote the turnover of microorganisms.Among them,the litter of Vicia sepium of a better quality can stimulate an increase in microbial biomass(4.1 times of Elymus nutans treatment)and promote the accumulation of microbial residual carbon,especially fungal residual carbon.This study showed that different root exudates and addition of litter could stimulate the growth of microorganisms,affecting their turnover rate,thereby promoting the sequestration of microbial organic carbon in the soil organic carbon pool.This effect is significantly related to the concentration and composition of root exudates and the quality of the litter.