Forests

Afforestation enhances soil carbon storage through plant and microbial necromass accumulation, yet the roles of carbohydrate-active enzymes (CAZymes) and the microorganisms that encode them (biomass-decomposers) during plantation development remain poorly understood. Here, we integrated shotgun metagenomics with network analysis to decipher the successional dynamics of CAZyme-encoding genes, biomass-decomposers, and their functional linkages across a chronosequence of plantation development in northeastern China. Plantation development increased the abundance of CAZymes involved in lignin, chitin, and glucan degradation. Network analysis of biomass-decomposers revealed that the dominant function of key module M1 gradually shifted from peptidoglycan to lignin degradation through network reorganization during development. Across all developmental stages, the key modules whose dominant functions were peptidoglycan and hemicellulose degradation consistently harbored keystone species. In the overlap-network, these two functions served as dominant functions in more than one key module, confirming their essential role in maintaining fundamental community functions. Stochastic processes predominantly governed the assembly of biomass-decomposers, with increasing influence during development (R² > 0.6). Variation in both biomass-degrading CAZymes and decomposers showed the strongest association with soil organic carbon, with CAZymes further structured by pH and nitrate nitrogen, whereas biomass-decomposers responded to moisture and total nitrogen. Overall, these findings provide new insights into belowground C cycling during plantation development, potentially guiding improved ecosystem management practices for forest restoration.

Soil organic matter (SOM) molecular composition governs its stability and ecological functions in forest ecosystems. Nevertheless, how land-use changes (LUCs) regulate the SOM molecular composition remains poorly understood, particularly the underlying mechanisms mediated by soil properties. This study investigated the effects of LUCs on SOM molecular composition in a subtropical coastal region and examined the driving roles of soil nutrient availability and enzyme activities. The research was conducted in Huanghai National Forest Park, Jiangsu Province, China, focusing on four land-use types converted from historical wheat cropland (W, as control): monoculture plantations of Ginkgo biloba (G) and Metasequoia glyptostroboides (M), a ginkgo–metasequoia mixed forest (GM), and a ginkgo–wheat agroforestry system (GW). Soil samples were collected from 0 to 20 cm and 20–40 cm layers and analyzed for SOM molecular compositions using solid-state ¹³C nuclear magnetic resonance (NMR) spectroscopy. Soil chemical properties and enzyme activity activities were also determined, with redundancy analysis (RDA) and correlation analysis applied to identify key influencing factors. Results demonstrated that LUCs significantly altered SOM molecular composition. The GW system exhibited the highest proportion of labile O-alkyl carbon (42.65%), while the M plantation accumulated greatest levels of stable aromatic carbon (up to 49.25%). During the initial decades following afforestation, soil nutrient availability and enzyme activities were confirmed as pivotal drivers of SOM molecular variation. Specifically, available potassium (AK), ammonium nitrogen (AN), and the carbon/phosphorus (C/P) ratio were significantly correlated with specific SOM components (p < 0.05). The elevated O-alkyl carbon proportion in GW was closely associated with its higher invertase activity. Notably, vertical differentiation in SOM stability was observed across land-use types, with the agroforestry system achieving the highest carbon pool management index in surface soil but showing a weakened capacity for subsoil C stabilization. RDA further confirmed that AK and AN were dominant factors shaping SOM molecular composition. In conclusion, LUCs modulate SOM chemical composition and stability primarily through altering soil nutrient availability and associated enzyme activities. Agroforestry system facilitates labile C accumulation in surface soil, whereas monoculture plantations are more conducive to stable C sequestration, especially in subsoil layers. These findings provide novel mechanistic insights into SOM dynamics following LUCs and offer a theoretical basis for formulating tailored management strategies to enhance C sequestration efficiency in subtropical coastal ecosystems.

This study provides a field evaluation of a deep container-based nursery system for tropical dry forest species. Deep containers are expected to improve seedling quality for dryland restoration, but their applicability to tropical dry forest species remains poorly documented. This study examined species-specific responses of five tropical dry forest species to two contrasting nursery systems, including a deep container system, under practical conditions. Five tropical dry forest species in Myanmar were raised in two nursery systems: conventional vinyl pots (18 cm depth) filled with soil-based media amended with manure and deep M-StAR containers (60 cm depth) filled with coconut peat and supplied with chemical fertilizer. Seedling morphology was assessed in the nursery, and survival and growth were monitored after outplanting. Seedlings raised in the deep container system exhibited substantially greater growth in the nursery phase across all species, attaining a several-fold larger size than conventional seedlings, and this size advantage persisted for 16 months after outplanting. However, higher survival was observed only for Tamarindus indica raised in this system (76%) compared with the conventional system (21%), whereas the other four species showed high survival (>80%) regardless of the nursery system. The observed benefits reflect the combined effects of the deep container system, and early post-planting survival may be species-specific and related to drought strategies.