The effects of Acacia auriculiformis aged eight (Aa_s) and two years (Aa₂) old and Gmelina arborea eight year-old (Ga_s) stands on the soil and microclimate of degraded grassland in Carranglan, Nueva Ecija, Philippines were studied. Litterfall and leaf litter decomposition under the stands in relation to soil nutrient status and microclimate were evaluated.
The older A. auriculiformis stand modified more efficiently the microclimate in terms of reduced air and surface soil temperature, increased relative humidity, and reduced light intensity over the other stands and the open grassland.
Amounts of litterfall were 1,338 and 405.Skg/ha/yr for Aa_s and Ga_s, respectively. Litter disappearance was fastest in G. arborea than in A. auriculiformis.
The contents of soil available P, organic matter and total N were most improved under A. auriculiformis. However, the contents of exchangeable K, Ca and Mg tended to be temporarily lower due to the more active uptake by the Aa_s trees. A trend towards soil bulk density improvement over the grassland soil was in the order of Aa_s > Aa₂ > Ga_s.
No initial variations in soil pH were observed. However, burning markedly increased soil pH due to the release of exchangeable K, Ca and Mg from the ash. But pH later declined after the rainy months.