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Purpose: High-diversity communities may mitigate the impact of environmental changes on soil erosion owing to the compositional, structural, and functional diversity of their species. In this field study, we explored the relative contributions of these biodiversity components to soil erosion and the mitigating effects of each index under environmental changes (e.g., rainfall intensity). Methods: We investigated the compositional (species diversity and evenness), structural (tree diameter and height diversity), and functional diversity (functional richness, evenness, and divergence) of 12 plant communities on Hainan Island, where biodiversity loss is severe. We measured soil erosion in each community using erosion plots under different rainfall intensities. The direction and relative contribution of biodiversity indices to soil erosion were analyzed. Results: Except for the functional evenness, high values of biodiversity indices were associated with significantly reduced soil erosion regardless of rainfall intensity, and the relative contribution of tree height diversity was greater than that of other biodiversity indices. In addition, multiple biodiversity factors alleviated the adverse effects of increased rainfall intensity on soil erosion, but plant structural diversity had a greater positive effect than compositional and functional diversity, predominantly because of tree height diversity. Conclusions: The results confirmed that the consideration of multiple biodiversity components provides an improved understanding of the relationship between biodiversity loss and soil erosion. We emphasize that protection of tree height diversity may not only effectively reduce current soil erosion, but also resist the adverse impact of increased rainfall intensity on soil erosion in the future. [ABSTRACT FROM AUTHOR]

Land‐use intensification has increased soil erosion through biodiversity loss, which affects ecosystem properties and services owing to changes in species compositional and structural diversity. However, information is limited on how land‐use intensity (LUI) affects soil erosion through species compositional diversity, structural diversity and ecosystem properties. In this study we monitored soil erosion in 15 plots over 12 consecutive months on tropical Hainan Island, where land‐use changes and biodiversity loss have been severe. We quantified the direct and indirect effects of LUI, species compositional diversity (plant species diversity and evenness) and structural diversity (tree diameter and height diversity), and ecosystem properties on soil erosion using Bayesian structural equation models (BSEM). The optimal BSEM accounted for 69% of the variation in soil erosion. The LUI did not affect soil erosion directly but showed indirect impacts via species diversity, tree height diversity, and ecosystem properties. Both high species diversity and tree height diversity reduced soil erosion directly and indirectly by promoting root length density (an ecosystem property), but tree height diversity mediated the more important indirect effect of LUI on soil erosion than species diversity and ecosystem properties. We provide evidence for loss of species diversity and tree height diversity as a result of LUI leading to aggravated soil erosion, but the impact of the latter was more serious. Therefore, we emphasize that maintenance of tree height diversity through management practices may be an effective approach to control soil erosion in the context of drastic land‐use changes in tropical areas. [ABSTRACT FROM AUTHOR]

Forest management can influence multistakeholders' benefits across the forest-water-energy-food nexus at the watershed scale. However, bringing synergistic gains for multiple stakeholders is still a challenge for regional sustainable management. We took the Changhuajiang basin in China's Hainan Island as a case to present the impacts of synergistic management for upstream forest and reservoir optimization on the benefits of downstream hydropower enterprise and different farmers. By multimodel ensembles and scenario analysis, we quantified the relationships among upstream forest ecosystem management (rubber-intercropped), reservoir, water flow and downstream stakeholders' benefits (i.e., hydropower generation for the energy company, and available irrigation water for two downstream sites' farmers). We also adopted the genetic optimization algorithm to obtain the optimal reservoir infrastructure operation rule for the benefit improvement of multiple stakeholders. We found that rubber-intercropped management significantly increased reservoir inflow in the dry seasons (5%–170%) and reduced it in the rainy seasons (0.5%–7%). The irrigation water availability for downstream farmers in the Gao Canal and downstream irrigation areas correspondingly increased by 7% and 24.3% on average, respectively, with a slight change in hydropower production. Further, we found that water regulation by reservoir optimization operation could enhance the irrigation water supply (36.6–92% and 0–100% in Gao Canal and downstream irrigation areas, respectively) and hydropower generation (14.8–28.4%). This study indicates that the effect of upstream forest management on downstream multistakeholders' benefits could be strengthened by reservoir water flow regulation across the forest-water-energy-food nexus, and demonstrates the key role of infrastructure in regulating ecosystem service flow for strengthening the benefits of multistakeholders in the context of ecosystem management. [Display omitted] • Change in water flow improved irrigated areas' water availability and slightly changed hydropower generation. • Reservoir optimization further improved benefits for farmers and hydropower company by regulating water flow. • Synergistic management of ecosystems and infrastructure can improve multistakeholders' benefits. [ABSTRACT FROM AUTHOR]

• Impact pathways of land-use intensity on soil water conservation were quantified. • Land-use intensity indirectly affects soil water conservation mainly via plant functional traits. • The main plant functional trait influencing soil water is tree height diversity. • Effects of tree height diversity on soil water conservation varied with rainfall intensity. • Tree height diversity is important to cope with seasonal drought under climate change. Land-use intensification has led to biodiversity loss, which affects ecosystem properties and services by altering plant functional traits. However, the mechanistic pathways through which land-use intensity (LUI) affects ecosystem services across functional traits and ecosystem properties remain unclear. We studied the relationships among LUI, plant functional traits, ecosystem properties, and soil water conservation in tropical Hainan Island, China, where land-use changes, biodiversity loss, and seasonal drought have had severe impacts. Soil water conservation was represented by two complementary processes, namely soil water retention (SWR) and soil water capture (SWC). SWR and SWC were observed along a LUI gradient after 27 rainfall events (14 light, 10 moderate, and 3 heavy). We quantified the direct and indirect effects of LUI, the community-weighted mean (CWM) and functional divergence (FDvar) of water-related plant functional traits (tree height, leaf thickness, specific leaf area, and leaf dry matter content), and ecosystem properties on SWC and SWR using Bayesian structural equation models. The results showed that LUI did not affect SWC and SWR directly but presented indirect impacts via functional traits and ecosystem properties. Importantly, tree height FDvar mediated the most important indirect effect of LUI on both SWC and SWR. Tree height FDvar indirectly affected SWC through ecosystem properties, while the direction of the effect changed from negative to positive with increasing rainfall intensity, and promoted SWR directly and indirectly by increasing litter fall and soil organic matter. Our results further provide evidence of an indirect effect of LUI on soil water conservation primarily through tree height FDvar. Loss of functional diversity of plant height caused by LUI resulted in a decrease in SWR and SWC, indicating that seasonal drought causes increased impacts. The results emphasize that maintaining functional diversity of tree height in tropical land use is conducive for soil water conservation to mitigate increased intensity of seasonal drought predicted under climate change. [ABSTRACT FROM AUTHOR]

Specific forest restoration aims to maximum ecosystem services (ESs); however, the complex trade-offs among ecosystem services pose considerable challenges for fulfilling such goals. Based on forest restoration on Hainan Island, China, we integrated spatially explicit models of ecosystem services and spatial prioritization techniques based on the efficiency frontier between habitat quality and plantation revenue to analyze the impacts of decision-makers' preferences on optimal configurations of forest restoration. We then investigated the effects of different optimal restoration schemes on water purification, soil retention, carbon sequestration, and coastal hazard mitigation. Based on our results, plantation revenue and habitat quality exhibited an obvious trade-off during the process of restoration. Forest restoration patterns also varied with the degree of preference for plantation yield or habitat quality, indicating that understanding ecosystem service tradeoffs can support the optimal selection of forest restoration schemes under different preferences. However, when the values of multiple ecosystem services associated with forest restoration were considered (e.g., water purification, soil retention, carbon sequestration, and coastal hazard mitigation), the optimal solution choice varied. Our results suggest the application of the efficiency frontier can deepen quantitative understanding of ecosystem service trade-offs, and the addition of multi-benefit evaluation based on optimal solutions can provide a more detailed and broader picture of forest restoration plans. Integrated efficiency frontier assessment with the valuation of ecosystem services associated with forest restoration provides a quantitative approach for optimal forest restoration, which can be applied in broad forest restoration programs. [ABSTRACT FROM AUTHOR]

Plantations support local economies and rural livelihoods in many mountainous regions, where poverty and a fragile environment are often interlinked. Managing plantations sustainably and alleviating poverty is a major challenge. This study reports on the findings of a household livelihood survey in the central mountainous region of Hainan Island, a global biodiversity hotspot. The survey aimed to identify rural household livelihoods, strategies to lift rural households out of poverty and potential environmental consequences of different livelihood strategies. Households were divided into five groups based on their main source of income: plantations, crops, livestock, local off-farm income and remittances. Plantations were the main source of income for 74% of households and provided 46% of the total income. Plantation land area, planting diverse tree species and intercropping were significantly associated with higher income. Reallocating land by family size could increase the proportion of households above the poverty line in the plantation group from 51.3% to 85.3%, while making only 3.3% of households worse off. Lower income households tended to apply more chemicals to plantations, which suggests that they create more strain on the environment. Improving household income through dynamically allocating plantation land and diversifying planted species could therefore be beneficial both socially and environmentally. Our results emphasize the importance of dynamic plantation land allocation and diverse plantation planting in poverty alleviation and environmental sustainability. [ABSTRACT FROM AUTHOR]