Effects of Acacia plantation on tree species composition, soil properties, mineralization and microclimate in grassland of Mt. Makiling philippines

Abstract

Rehabilitation activities improve degraded ecosystems functionally, by changing, positively, species composition, soil properties, mineralization and microclimate. The study area in Mt. Makiling was rehabilitated and protected from fire for over 12 years, and changes in species composition, soil properties, mineralization and microclimate were examined. After the area was burned extensively in 1991, reforestation was done by planting Acacia mangium and Acacia auriculiformis. Three study sites were selected in 2003: two sites were planted with A. mangium and A. auriculiformis, and one was still dominated by Imperata cylindrica and Saccharum spontaneum. Air temperature and relative humidity were monitored every hour for 12 months and soil temperature every 2 hours for 11 months using HOBO data loggers in Aug. 2003 – Jun. 2004. A. auriculiformis showed higher growth of height and DBH than those of A. mangium in 10-year-old plantation. However, more species appeared in A. mangium plantation than in A. auriculiformis plantation. Soil nitrogen concentrations in the Acacia plantations were significantly greater than those in grassland. The soil C/N ratio in grassland was significantly greater than that in Acacia mangium plantations. Seasonal variation in net N mineralization was pronounced, with peak values occurring in September at Acacia plantation site. Grassland showed not only higher air temperature, relative humidity and soil temperature than Acacia plantation but its larger variations per hour. Highest peak of air temperature, relative humidity and soil temperature were shown in April. The result showed that site qualities in grassland have been improved by rehabilitation activities.