Effect of Forest Management Operations on Aggregate-Associated SOC Dynamics Using a 137Cs Tracing Method

Geng Guo,Jie Lin,Yanyin Xu,Guangruo Zeng,Xi Zhu,Xiao Li,Qiao Dai

doi:10.3390/f12070859

Geng Guo, Jie Lin + Show 5 more

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https://doi.org/10.3390/f12070859

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Abstract

Although forest conversions have long been a focus in carbon (C) research, the relationship between soil erosion and the dynamic change of soil organic carbon (SOC) has not been well-quantified. The objective of this study was to investigate the effects of converting CBF (coniferous and broad-leaved mixed forests) to economic forests, including CF (chestnut forest), HF (hawthorn forest), and AF (apple forest), on the soil structure and nutrient loss in the Huaibei Rocky Mountain Areas, China. A 137Cs tracer method was used to provide soil erosion data in order to quantify the loss of aggregate-associated SOC. The results showed that forest management operations caused macro-aggregates to decrease by 1.69% in CF, 4.52% in AF, and 3.87% in HF. Therefore, the stability of aggregates was reduced. The SOC contents in each aggregate size decreased significantly after forest conversion, with the largest decreases occurring in AF. We quantified the loss of 0.15, 0.38, and 0.31 Mg hm−2 of aggregate-associated SOC after conversion from CBF to CF, AF, and HF, respectively. These results suggest that forest management operations have a negative impact on soil quality and fertility. CF has better vegetation coverage and less human interference, making it more prominent among the three economic forests species. Therefore, when developing forest management operations, judicious selection of tree varieties and appropriate management practices are extremely critical. In addition, measures should be taken to increase surface cover to reduce soil erosion and achieve sustainable development of economic forests.

Highlights

Soil is the largest terrestrial carbon (C) pool in the world, and it contains at least three times as much C as the atmosphere [1]
Total soil organic carbon (SOC) concentrations in chestnut forest (CF), apple forest (AF), and hawthorn forest (HF) decreased by 38.9%, 62.6%, and 55.2%
There were no significant differences in Bulk density (BD) and Dissolved organic carbon (DOC) regardless of forest conversion and subsequent intensive management

Summary

Introduction

Soil is the largest terrestrial carbon (C) pool in the world, and it contains at least three times as much C as the atmosphere [1]. It was reported that the terrestrial C stock releases about 4% of its pool into the atmosphere each year [2]. The distribution of aggregate and aggregate-associated soil organic carbon (SOC) determines the capacity of the soil to store and retain C [4]. Aggregates are the structural units of the soil, and SOC is the critical binding material of aggregates. The differences in size distribution and the stability of aggregates control the changes of microbial activities and nutrient cycling, which in turn affects the soil biogeochemical and biophysical processes [5,6]. Aggregate formation is considered as one of the most important mechanisms of SOC sequestration [7].

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