Seasonal variation in soil macrofauna and soil physical and chemical properties in homegarden agroforestry systems of North Wollo, Ethiopia

Abstract

Homegarden agroforestry systems support soil biodiversity and nutrient cycling, yet seasonal variation in soil macrofauna remains insufficiently documented in northern Ethiopia. This study evaluated seasonal variation in soil macrofauna abundance, biomass, diversity, and selected soil physical and chemical properties in homegarden agroforestry systems of Habru Woreda, North Wollo, Ethiopia. A 2 × 2 factorial design comprising two agroecological zones (midland and lowland) and two seasons (dry and wet) was used. Thirty established homegardens, 15 from each agroecological zone, were sampled during both seasons, resulting in 60 observations. Soil macrofauna were collected using the Tropical Soil Biology and Fertility (TSBF) soil monolith method and pitfall traps, while composite soil samples were collected from 0 to 30 cm depth. Macrofauna were identified primarily to family level. Soil moisture, temperature, pH, bulk density, organic carbon, total nitrogen, and C/N ratio were determined. Data were analyzed using two-way ANOVA, Tukey’s HSD test, and Pearson’s correlation analysis. Macrofauna abundance increased from 246.3 to 300.8 individuals m⁻ 2 in the midland and from 212.7 to 251.7 individuals m⁻ 2 in the lowland from the dry to wet season. Earthworms, termites, and ants were the dominant groups, collectively accounting for 70.9–76.6% of total abundance. Shannon diversity increased from 1.68 to 1.82 in the midland and from 1.54 to 1.73 in the lowland. Soil moisture, organic carbon, and total nitrogen increased during the wet season, whereas temperature and bulk density decreased. Macrofauna abundance was positively correlated with soil moisture (r = 0.69), organic carbon (r = 0.66), and total nitrogen (r = 0.57), but negatively correlated with temperature (r = −0.53) and bulk density (r = −0.48). These findings demonstrate that seasonal environmental conditions, particularly soil moisture, are closely associated with soil macrofauna dynamics in homegarden agroforestry systems.