Characterizing soil properties of lowland and hill dipterocarp forests at Peninsular Malaysia.

A study was conducted to characterize soil properties of a rehabilitated-degraded forestland and an adjacent natural forest in two major forest types, representing the lowland and hill-dipterocarp forests at Bidor and Kinta Forest Reserves, respectively. Twelve soil profiles were dug at both sites. At Bidor site, the soil profiles were under rehabilitated secondaiy forests (B1 and B2), an abandoned Acacia mangium plantation (B3 and B4) and natural forests (B5 and B6) of lowland dipterocarp. However, at Kinta site, the soil profiles were located in differing topography: rehabilitated secondaiy forests at 450 m (K1 and K2), rehabilitated secondaiy forests at 550 m (K3 and K4) and natural forests at 650 m (K5 and K6) above sea level. The effect of rehabilitating the forests could be seen by the accumulation of organic matter in the uppermost layer, which was assumed to be at an intermediate stage of mineralization. The soil morphology in natural forests of Bidor site exhibited a thicker and darker upper horizon than that of the rehabilitated sites, whereas, those at Kinta site had pronounced soil color in the upper horizon, though to come from decomposition of organic matter. The soils were very acid (pH <5.5), having low activity clay resulting in low (<16 cmol c kg -1) Cation Exchange Capacity (CEC), available P (Av. P), total nitrogen and exchangeable bases, but high in exchangeable Al. High exchangeable A1 was the main cause of soil acidity. The main source of negative charge was the organic matter which affected the CEC, Points Zero Salt Effect (PZSE) and op values. The soils were considered as strongly weathered, devoid of 2:1 type clay minerals. Kaolinite and gibbsite dominated the clay fraction of the soils at both sites. It is recommended that soil characteristics be taken into consideration prior and during the rehabilitation of degraded forestland in tropical rainforests

Characterizing soil nutrient status and growth performance of planted dipterocap and non-dipterocarp species on degraded forest land in Peninsular Malaysia

This study aims to assess the soil nutrient status and growth performance of selected six dipterocarp species namely Dryobalanops aromatica, Hopea nervosa, Neobalanocarpus heimii, Shorea parvifolia, S. assamica and S. leprosula and three non-dipterocarp species of Azadirachta excelsa, Cinnamomum iners and Intsia palembanica were performed six years after planting on degraded forest land in Pasoh Forest Reserve, Negeri Sembilan, Peninsular Malaysia. This assessment consists of determining soil nutrient status based on physico-chemical properties both in rehabilitated and adjacent secondary forests along with measurement of diameter at breast height and height and survival rate. The results showed that rehabilitating degraded forest land with dipterocarp and non-dipterocarp species had improved both soil nutrient status and valuable timber stocks. The soils were acidic with low levels of organic matter and exchangeable bases associated with high level of Al saturation. The negative charges derived from the organic matter and clay minerals play an important role in retaining soil nutrients and probably influence the soil nutrient status. Principal component analysis revealed three most important PC scores which explained 73.8% of total variation. PC1 represents cation retention capacity and soil organic matter. PC2 infers soil acidity, while PC3 related to physical properties of the soils. In the case of growth performance, A. excelsa and C. iners showed significantly high mean annual increments in diameter and height and survival rate at six years after planting. Irrespective of different ages after planting, the growth performance and survival rate of planted dipterocarp species especially S. leprosula and S. parvifolia were comparable to similar species grown at other planting trials in Malaysia