Effects of microhabitat characteristics on abundance of macroinvertebrate soil fauna in Ranibari community forest, Kathmandu, Nepal

Abstract

Microenvironmental characteristics like canopy cover, litter depth, soil moisture, soil organic matter, pH, nutrient content of soils are associated with the soil biodiversity. The soil faunal community are strongly affected by urban green space, community gardens and plotted lands. This study aimed to explore the association between the microenvironmental characteristics of forest ecosystem and the abundance of macroinvertebrate soil fauna (here after soil fauna) in Ranibari Community Forest, one of the biggest forest patches in the urban environment of the Kathmandu Valley. The effects of the microhabitat on the soil fauna were observed in 10 × 10 m 2 plots. Faunal sampling was done from 85 quadrates of each 1×1 m 2 to observe the richness and abundance of soil fauna. Highest number of soil fauna (n=200) were spotted under the canopy cover of Stranvaesia nussia. The canopy is predominately occupied by the bamboos and tree species of Stranvaesia nussia, Schima wallichilli, Persea duthiei. Soil physio chemical analysis was conducted to know the effects of the soil characteristics on soil fauna. The lowest canopy ranged between 65%– 85% and the most of the canopies (n=43) were in the range of 76%–80%. A total of 1011 soil fauna were observed out of which 56.4% (530) were recorded in the moist soil. The soil pH of the study area ranged from 6.2 to 8.3. Out of 85 samples tested, 59 samples had soil pH above 7. The most area in the forest was covered by the leaf litter under the canopies. About 81% (n=69) of the total studied quadrates had the presence of leaf litter and 19% (n=26) had no litter decomposed under their canopies. The pH, N, P, K of the soil also affect the abundance of the soil fauna; acidic soil condition and high nitrogen content in the soil can be toxic to the soil fauna. Clay soil had the most number of soil fauna (n=543) than loamy and sandy soil. Soil fauna abundance was higher in lower concentration of nitrogen and phosphorous and medium concentration of potassium.