A Meta-Analysis of Soil Microbial Necromass Accumulation in Response to Climate Warming
[Objective]The effect of warming on the accumulation dynamics of microbial necromass is of great significance to the balance of soil carbon(C)pool.However,the impact of climate warming on microbial necromass is poorly understood.Thus,the objective of this study was to evaluate the responses of microbial necromass to climate warming and the main factors controlling this feedback.[Method]In this study,a meta-analysis was conducted to reveal general patterns of climate warming on amino sugars(microbial necromass biomarkers)in soils under grasslands,forests,and croplands.Here,12 published publications from international and domestic journals were collected and extracted independent observations that met our criteria(29 for total amino sugars,35 for glucosamine,39 for muramic acid,and 25 for galactosamine).[Result]The results showed that the overall effects of warming could promote the accumulation of microbial necromass.However,warming effect sizes on microbial necromass were not consistent across different ecosystems,with the most sensitive responses occurring in cropland.The response of fungal and bacterial necromass differed under climate warming.Specifically,warming significantly increased the content of galactosamine and muramic acid,with an increase of 10.3%and 5.0%,respectively.Together with the significant decline in the ratio of glucosamine to muramic acid,the results suggested that warming benefited the accumulation of bacterial necromass compared to fungi.Also warming significantly increased the proportion of bacterial necromass to soil organic carbon(SOC),while the contribution of fungal and total necromass to SOC did not change significantly,suggesting that the contribution of fungal-derived C to SOC was weakened under warming scenarios.Warming magnitude was a key factor affecting the accumulation of microbial necromass.For instance,the accumulation of microbial necromass increased by 2.7%-14.6%,when the warming magnitude was less than or equal to 2℃relative to unwarmed control.However,when the warming amplitude was greater than 2℃,the accumulation of microbial necromass was decreased by 8.0%-14.3%.Interestingly,the duration of warming was an important factor affecting the accumulation of microbial necromass.[Conclusion]The results demonstrate that warming has significant effects on the accumulation dynamics of microbial necromass and their contribution SOC pool.The intensity and direction of the warming impact are largely dependent upon ecosystem type and soil depth,in which warming amplitude,warming duration,and mean annual precipitation are important factors controlling the sequestration of the microbial-derived C under global climate warming.
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