Characteristics of Ultisols under Different Wildfire History in South Sumatra, Indonesia: I. Physico-chemical Properties.

Abstract

Fire has become a great threat to Indonesian rainforest. However, informative data quantifying the effects of wildfire on the soils are still limited. We have been studying the leftover effect of forest fire on characteristics of Indonesian Ultisols. Current experiment evaluated physico-chemical characteristics of soils under different ecosystems with different wildfire history. Seven sites, which could be grouped into unburnt sites (conservation forest (CF), Pine forest (iF), Acacia mangium plantation (AM), and home garden (HG)) and burnt sites (Acacia mangilan plantations bumt in i995, L997, and 1998) referred as AM-b95, AM-b97, and AM-b98, respectiveiy, were sampled. Organic layei was found in CR PR and AM but not in any other sites. Morphologically, soils of unbumi sites had darker A horizon than those of burnt sites. In spite of lack of significant differences, bulk density decreased with increasing period after fire, indicating the recovery process. Although the upper layer oi the bumt soils was physically harder than that of the unbumt soils, soil hardness did not aipear to be a limiting factor for plant growth. Soil in the unbumt sites was chemically more acid but contained mqre organic C and N than that in the bumt sites. Surface soil of PF, AM-b98, and HG had much higher exchangeable Ca than any other sites. However the CEC was low across the study sites, irrespectivi of the high clay content. Available P was also low, and conelated with high Al solubility. Crysialline Al, Si, and Fe contents of all soils were higher than amorphous Al, Si, and Fe oxides. ZpC values were low across the study sites. However, higher negative charge generated by organic matter had resulted in lower ZPC values at the surface layer as compared with the subsurface Lyer. Although soils in the unbumt sites showed a better physico-chemical potential than the bumt site;, in general Ultisols in the study sites had undergone strong weathering and showed low natural fertility potential.

Relationships between soil characteristics and productivity of Acacia mangium in South Sumatra

“…Lower exchangeable Al and Al saturation and higher soil pH in high productivity subsoil horizons than in low productivity soils suggests that high productivity soils have higher capacity for improved nutrient availability. Meanwhile in low productivity soils with lower soil pH and higher exchangeable Al and Al saturation might result in solubilization of larger amounts of Al and consequently increased toxicity for Acacia root growth (Kadir et al 2001), in addition to their lower capability to supply nutrients. The CEC of LPS subsoil is higher than HPS because of higher clay content.…”

“…: strong acidity, low nutrient supply, and retention capacity (Siradz 2000;Zaidey et al 2010), low resistance against soil surface erosion and susceptibility to soil compaction (von Uexkull and Mutert 1995), and they can cause problems for sustainable management of fast growing short rotation plantations (Sim and Nykvist 1991;Nambiar 1996). Ultisols also have a relatively wide range of physico-chemical characteristics (Ohta and Effendi 1992a;Ohta and Effendi 1992b;Ohta et al 1993;Kadir et al 2001) and a wide range of productivity potential (Hardiyanto pers. comm.).…”

Emphasizing the properties of soils occurring in different land use types of tropical rainforest in Sarawak, Malaysia

“…The soil profiles at RF, LF, OP and RP exhibit the A horizon with darker color, ranging from dark brown (7.5YR 3/2) and dark yellowish brown (10YR 4/4) to brownish yellow (10YR 6/8), probably due to the decomposition of organic matter. The lighter color of soils at OP and RP areas may be due to loss of organic matter caused by tillage and/or subsequent erosion (Kadir et al, 2001;Heshmati et al, 2012).…”

“…Meanwhile, consistency of soils at RF and OP are friable to very friable. With depth both the stickiness and plasticity increases mainly due to the increasing amount of clay content (Kadir et al, 2001). Roots are abundant in all pedons, ranging from few to many coarse to fine root sizes.…”

“…The increase in pH (H 2 O) with depth might be related to the increase in Fe and Al oxides and decrease of organic matter which inhibit high and low pH 0 values, respectively (Sanchez, 1976). Hydrolysis of Al under strong leaching condition produces acidity in these soils because at low pH Al is present in the exchange complex and diffuses into solution where it may lower the pH and cause toxicity (Kadir et al, 2001).…”