Decomposition and stabilization of the organic matter in an old-growth tropical riparian forest: effects of soil properties and vegetation structure

Abstract

Background: Nutrient cycling in tropical forests has large importance for primary productivity, and decomposition of litterfall is a major process influencing nutrient balance in forest soils. Although large-scale factors strongly influence decomposition patterns, small-scale factors can have major influences, especially in old-growth forests that have high structural complexity and strong plant-soil correlations. We evaluated decomposition rates and stabilization of soil organic matter using the Tea Bag Index in an old-growth riparian forest in southeastern Brazil to evaluate the effects of forest structure and soil properties on decomposition processes. These data sets were described separately using Principal Components Analysis (PCA). The main axes for each analysis, together with soil physical properties (clay content and soil moisture), were used to construct different structural equations models that evaluated the different parameters of the TBI, decomposition rates and stabilization factor. The best model was selected using Akaike’s criterion.Results: Forest structure and soil physical and chemical properties presented large variation among plots within the studied forest. Clay content was strongly correlated with soil moisture and the first PCA axis of soil chemical properties, and model selection indicated that clay content was a better predictor than this axis. Decomposition rates presented a large variation among tea bags (0.009 and 0.098 g g-1 day-1) and were positively related with forest structure, as characterized by higher basal area, larger trees, and tree density. The stabilization factor varied between 0.211 – 0.426 and was related to forest stratification and soil clay content. Conclusions: The old-growth forest studied presented high heterogeneity in both forest structure and soil properties at small spatial scales, that influenced decomposition processes and probably contributed to small-scale variation in nutrient cycling. Decomposition rates were only influenced by forest structure, whereas the stabilization factor was influenced by both forest structure and soil properties. Heterogeneity in ecological processes can contribute to the resilience of old-growth forests, highlighting the importance of restoration strategies focused on the spatial variation of ecosystem processes.

Dual inoculation of dark septate endophytes and Trichoderma viride drives plant performance and rhizosphere microbiome adaptations of Astragalus mongholicus to drought

“…Certain Ascomycota , including DSE, form mycorrhizae in plant roots and enhance plant nutrient uptake and growth (Surono and Narisawa, 2018 ). The genus Stachybotrys is a marked producer of cellulose‐degrading enzymes (Fernandes et al ., 2021 ). Trichoderma is an effective biofertilizer, soil amendment and biocontrol agent (Herrera‐Parra et al ., 2017 ; Saxena et al ., 2020 ).…”

“…Certain Ascomycota, including DSE, form mycorrhizae in plant roots and enhance plant nutrient uptake and growth (Surono and Narisawa, 2018). The genus Stachybotrys is a marked producer of cellulose-degrading enzymes (Fernandes et al, 2021).…”