Abstract
Research Highlights: Soil carbon storage (SOC) decreased due to forest fragmentation through lower proportion of macroaggregate distribution, higher storage of fine roots and litter falls, and lower fine root production rate. Background and Objectives: Globally, forest fragmentation processes lead to enormous losses of SOC in forests. We investigated SOC and its determinants in forest fragments experiencing edge disturbances in south China. Materials and Methods: Soil aggregate characteristics, dynamics of fine roots, and litter fall were studied from forest edges to interiors. Generalized linear mixed models were used to model the contributions of fine root and litter fall dynamics to carbon concentration in aggregates. Results: Large and small macroaggregates had higher proportion of aggregate distribution and contributed more carbon to SOC in all types of plots in the present study. SOC significantly increased from forest edges to interiors due to carbon concentration of these two aggregate types increasing from edges to interiors, while the proportion of different aggregate distributions was similar within each plot. The same trend was found with increasing forest patch size. Fine root biomass storage had the strongest impact on carbon concentration in large macroaggregates and microaggregates, with higher fine root biomass storage associated with lower carbon concentration. In addition, biomass storage and production rates of both fine roots and litter falls decreased from forest interiors to edges. Our results showed that SOC was significantly decreased due to the lower proportion of large and small macroaggregate distribution, and lower fine root production rate in forest fragments. Conclusions: SOC loss due to effects of forest fragmentation and forest edges occurred through decreased concentrations of soil aggregates and fine root production rates. Results from this study will enhance our ability to evaluate soil aggregate, fine root, and leaf litter fall contributions to SOC within forest fragments, and to suggest basic recommendations for the management and conservation of these forest fragments.
Highlights
Soil stores the largest reserve of organic carbon in terrestrial ecosystems [1]
Since physical protection of soil organic carbon within stable soil aggregates is considered to be one of the major soil organic carbon stabilization mechanisms, the effect of land management on aggregate stability in croplands is accepted as a key factor in determining soil organic carbon levels
For a better understanding of the underlying mechanisms of carbon uptake and loss in soil due to forest fragmentation, we investigated SOC, soil aggregate distributions, and dynamics of fine roots and litter in forest fragments in south China
Summary
In studies of soil organic matter, physical separation of soil into aggregate and particle-size fractions has received increased attention because it enables separation into pools of differing compositions and biological functions [2]. Soil aggregates are the basic units of soil structure and consist of primary particles. Forests 2019, 10, 1044 and binding agents They contain about 90% of the soil organic matter in the soil surface layers [2]. Aggregates play an important role in soil structure stability, soil organic carbon protection, and nutrient availability, as well as differential microbial activity. Aggregate formation is a key process of soil development, which promotes carbon stabilization by hindering decomposition of particulate organic matter and its interactions with mineral particles [3]. Much less is known about aggregate formation in fragmented forest soils
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