Abstract:

Soil erosion is an important driver of carbon loss, and the analysis of changes in soil microbial biomass carbon(SMBC) content and its related influencing factors under soil erosion conditions is pivotal for understanding the mechanism of soil nutrient turnover and carbon cycling driven by soil erosion. In this paper, 230 sets of experimental data from 35 published academic papers regarding the effects of soil erosion on SMBC were collected, and grouped by soil types (purple soil, black soil, loess soil and red soil), soil bulk density (high and low bulk density), land use types (forest land, agricultural land, grassland and sloping land), water erosion type regions (northeast black soil region, northwest loess plateau region, southwest soil and stone mountain region and southern hilly red soil region), average annual rainfall (1000-2000 mm, 500-1000 mm and ≤500 mm ) and mean annual temperature (≥20 ℃, 10-20 ℃, 5-10 ℃ and <5 ℃). A meta-analysis then was conducted to comprehensively analyze the variation characteristics of SMBC content under soil erosion conditions, and to investigate the effects of water erosion on SMBC by subgroup analysis. Experimental results under no erosion condition were set as controls. Results showed that (1) soil erosion significantly decreased SMBC content by 35.39% with a confidence interval from -0.4074 to -0.3005; (2) Erosion of purple, black, yellow and red soils showed a significant negative effect on SMBC content, with decreases of 78.72%, 43.49%, 42.52% and 18.48%, respectively. Soil erosion caused significant decreases in SMBC content under different soil bulk density conditions, and the decrease in SMBC under high bulk density conditions was 2.12 times greater than that under low bulk density conditions. Meanwhile, amongst different land use types, SMBC decreased the least in forest land (33.26%) and the most in grassland (39.73%). The decrease in SMBC content was the highest in the northeastern black soil region (43.55%), followed by the northwestern loess plateau region (42.57%) and the southwestern soil and rocky mountain region (33.68%), and the lowest in the southern hilly red soil region (27.51%); The decreases in SMBC content were 29.91%, 43.15% and 37.52% in areas with mean annual rainfall of 1000-2000 mm, 500-1000 mm and ≤500 mm respectively, and were 40%, 37.25% and 43.58% in areas with annual average temperature of 10-20 ℃, 5-10 ℃ and <5 ℃ respectively. It is therefore concluded that soil erosion significantly reduces SMBC content, and the decrease extents are different under various soil types, land use types, soil bulk densities, water erosion type regions and average annual rainfall.

Key words: China, soil erosion, soil microbial biomass carbon, meta-analysis, influence factors

摘要：

土壤侵蚀是碳流失的重要驱动力，分析土壤侵蚀条件下土壤微生物生物量碳（SMBC）含量变化及其相关影响因素，对理解土壤侵蚀对土壤养分周转与碳循环机制具有重要意义。以未发生侵蚀为对照，基于2003—2022年间相关学者在中国区域内开展的有关土壤侵蚀对SMBC影响研究已公开发表的35篇学术论文的230组试验数据，按照土壤类型（紫色土、黑土、黄土和红壤）、土壤容重（高容重和低容重）、土地利用方式（林地、农田、草地和坡耕地）、水力侵蚀类型区（东北黑土区、西北黄土高原区、西南土石山区和南方红壤丘陵区）、年平均降雨量（1000—2000 mm、500—1000 mm和≤500 mm）和年平均温度（≥20 ℃、10—20 ℃、5—10 ℃和<5 ℃）进行分组，采用Meta分析对土壤侵蚀条件下SMBC含量变化的特征进行综合分析，并通过亚组分析探讨了侵蚀对SMBC的影响。研究发现，与未发生土壤侵蚀相比，（1）土壤侵蚀导致SMBC含量显著降低（下降程度为35.39%，置信区间为-0.4074— -0.3005）；（2）紫色土、黑土、黄土和红壤中，土壤侵蚀对SMBC含量的影响均表现出显著的负效应，下降幅度分别为78.72%、43.49%、42.52%和18.48%。不同土壤容重条件下，土壤侵蚀使SMBC含量显著下降，SMBC下降程度在高容重条件下是低容重的2.12倍。同时不同土地利用类型中林地（33.26%）SMBC下降最少，草地（39.73%）下降最多。SMBC含量的下降程度在东北黑土区（43.55%）最高，西北黄土高原区（42.57%）和西南土石山区（33.68%）次之，在南方红壤丘陵区（27.51%）最低；不同年均降雨量和不同年均温条件下的SMBC含量下降程度在年均降雨量1000—2000 mm、500—1000 mm和≤500 mm的地区分别为29.91%、43.15%和37.52%，在年均温为10—20 ℃、5—10 ℃和<5 ℃的地区分别为40%、37.25%和43.58%。由此可见，土壤侵蚀显著降低SMBC含量；不同土壤类型、不同土地利用方式、不同土壤容重、不同水力侵蚀类型区、不同年均降雨量等条件下，土壤侵蚀对SMBC下降的作用程度不同。

关键词: 中国, 土壤侵蚀, 土壤微生物生物量碳, Meta分析, 影响因素