Agroforestry for soil health in a tropical national park of Gunung Halimun Salak, Indonesia

Abstract. Suharto FF, Wijayanto N, Wasis B. 2025. Agroforestry for soil health in a tropical national park of Gunung Halimun Salak, Indonesia. Asian J For 9: 346-360. This study evaluated the Visual Evaluation of Soil Structure (VESS) method as a rapid assessment tool for soil health across six stand types in Gunung Halimun Salak National Park, Indonesia. The research employed a comparative design across natural forest, mixed stand, and four agroforestry systems (damar-cardamom, damar-coffee, damar-chili, damar-eggplant), with three replicate plots per stand. VESS assessment followed standardized protocols, evaluating aggregate size, porosity, root distribution, and structural strength in the 0-30 cm depth. Laboratory analyses quantified bulk density, porosity, moisture content, pH, organic carbon, and Cation Exchange Capacity (CEC). Statistical analyses included ANOVA, Duncan's test, Principal Component Analysis, and Spearman correlation. We linked VESS scores to vegetation composition and laboratory-measured soil properties. Vegetation analysis revealed distinct dominance patterns: natural forest by Macropanax dispermus (IVI=120.57%), agroforestry systems by Agathis dammara (IVI=158.05-300.00%), and mixed stand by Altingia excelsa (IVI=248.50%). VESS evaluation showed good soil structure (Sq=1.0-1.84) in natural forest and low-intensity agroforestry, with moderate degradation (Sq=2.5) in intensive systems. PCA confirmed VESS as an integrative indicator, with PC1 explaining 73.55% of variance along a soil structure gradient. Principal Component Analysis (PCA) and Spearman correlations revealed strong correlations emerged between VESS and bulk density (ρ=+0.85), porosity (ρ=-0.85), moisture content (ρ=-0.85), organic carbon (ρ=-0.86), and CEC (ρ=-0.77). VESS scores exhibited strong and significant correlations with key soil health indicators, showing they increased with compaction and decreased with porosity, moisture content, soil organic carbon, and cation exchange capacity. The findings support VESS as a practical field tool and are effective for detecting management-induced soil degradation. We recommend its integration into the park's regular monitoring protocols to support soil conservation efforts. Promoting complex agroforestry systems is also advised. Study limitations include single-observer assessment and unmeasured environmental covariates, suggesting the need for further validation.