The Assessment of Soil Quality and Earthworms as Bioindicators in the Alas Bromo Education Forest, Central Java, Indonesia

Abstract

Understanding the environmental services provided by healthy forest ecosystems needs accurate soil quality (SQ) assessments. Selecting appropriate SQ indicators is one of the keys to the effectiveness of SQ assessment. Earthworms have the potential to be bioindicators of soil quality because they are sensitive to environmental changes. This study aims to assess the soil quality level and evaluate the potential of earthworms as bioindicators in six land covers at the Alas Bromo Education Forest of Universitas Sebelas Maret, namely: pine, pine-mahogany, mahogany, mixed, annual crops, and pine replanting. SQ assessment is measured by calculating the Soil Quality Index (SQI) using Principal Component Analysis (PCA) with 10 Minimum Data Sets (MDS), namely: bulk density, earthworm abundance, C-organic, N-total, pH, porosity, exchangeable Al, cation exchange capacity (CEC), base saturation (BS), and available K. Statistical analysis using ANOVA, Duncan's Multiple Range Test, correlation, and regression. The results showed that land cover significantly (p-value < 0.01) affected SQI. The SQI for all land cover categories is poor, with the highest value on mixed land cover (0.36) and the lowest on pine-mahogany (0.31). The land cover also significantly (p-value < 0.01) affected earthworm abundance, with the highest on mixed land cover (365 individuals/m 2 ) and the lowest on pine replanting (25 individuals/m 2 ). Earthworm density as a determining indicator significantly correlated with SQI (r = 0.495) and contributed 24.5% to the SQI. Future research needs to test the effectiveness of earthworms as a bioindicator of soil quality in other land uses in different areas.