Abstract
Soil dissolved organic carbon (DOC) and nitrogen (DON) play significant roles in forest carbon, nitrogen and nutrient cycling. The objective of the present study was to estimate the effect of management practices and nitrogen (N) deposition on soil DOC and DON in Moso bamboo (Phyllostachys edulis (Carrière) J. Houz) plantations. This experiment, conducted for over 36 months, investigated the effects of four N addition levels (30, 60 and 90 kg N ha−1 year−1, and the N-free control) and two management practices (conventional management (CM) and intensive management (IM)) on DOC and DON. The results showed that DOC and DON concentrations were the highest in summer. Both intensive management and N deposition independently decreased DOC and DON in spring (p < 0.05) but not in winter. However, when combined with IM, N deposition increased DOC and DON in spring and winter (p < 0.05). Our results demonstrated that N deposition significantly increased the loss of soil DOC and DON in Moso plantations, and this reduction was strongly affected by IM practices and varied seasonally. Therefore, management practices and seasonal variation should be considered when using ecological models to estimate the effects of N deposition on soil DOC and DON in plantation ecosystems.
Highlights
Dissolved organic matter (DOM) is a mixture of organic molecules of different sizes and structures that can pass through a 0.45 μm sieve and dissolve in water and acidic and alkaline solutions [1,2]. DOM accounts for a small proportion of the soil organic matter pool, it plays an important role in microbial growth and metabolism, which regulate soil nutrient loss and affect the decomposition and transformation of soil organic matter [3,4]
The present study showed that intensive management (IM) significantly decreased dissolved organic carbon (DOC) and DON concentrations in spring (Figures 1 and 2), which partly supported our first hypothesis: IM practices decrease soil DOC
Our previous study on this site showed that IM significantly increased soil microbial biomass carbon (MBC) [21], indicating an increase in DOC consumption, which might greatly contribute to lower DOC concentrations in the IM plots than in the conventional management (CM) plots
Summary
DOM accounts for a small proportion of the soil organic matter pool, it plays an important role in microbial growth and metabolism, which regulate soil nutrient loss and affect the decomposition and transformation of soil organic matter [3,4]. DOC affects the regulation of cation leaching, mineral weathering, soil microbial activity, and anion adsorption and desorption, as well as other soil chemical, physical and biological processes [6]. DOC is a very important and active factor associated with terrestrial and aquatic ecosystems in the geochemical carbon cycle [6,7]. DON plays a dual role in N cycling in terrestrial ecosystems: on the one hand, it can be directly absorbed by plants and shorten the terrestrial nitrogen cycle; on the other hand, DON has high mobility and can cause pollution in aquatic ecosystems through surface runoff or leaching [8].
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