Kadir, Sabaruddin (2002) Effects of Forest Fire on Characteristics of Soil Ecosystem in South Sumatra, Indonesia. Doctoral thesis, Universitas Sriwijaya.
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Text (Doctoral Thesis)
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Abstract
Both conversion of natural forests into human-managed land and burning of forest ecosystems are still widely practiced in Indonesia. More frequently drought related to the El Niño-Southern Oscillation (ENSO) and the irresponsible use of natural resources have also exacerbated fire problems over the last twenty years. However, informative data quantifying the effects of conversion of natural forests into human-managed ecosystem and mainly the effects of fires on the soils are still lacking, hence the effects are still poorly understood. The objectives of the present study were to study the effects of forest ecosystem practices on the characteristics of Ultisols and to investigate both the immediate effects and delayed effects of wildfire on the dynamics of chemical and biological characteristics of Ultisols in South Sumatra Province, Indonesia. This was carried out by investigating the immediate changes in the chemical and biological characteristics of the soils both under laboratory and field conditions. The results of the preliminary study showed evident differences in soil characteristics between the natural forest and the human-managed ecosystems, and between the unburned and the burned sites. In spite of the fact that soils in the unburned sites showed a better physico-chemical potential than those in the burned sites, in general Ultisols in the study sites showed a low natural fertility potential. Artificial heating at 100C did not cause significant changes in soil chemical characteristics but increased the sand fraction and decreased the clay fraction of the soil. However, heating at 300 and 500C, a representative of intensive burning, for example during forest fires, adversely affected all soil characteristics investigated. Watering to some extent showed positive effects on chemical characteristics, except on the available phosphorous. Both forest management practices and wild fire occurrence significantly affected the dynamics of total carbon, total nitrogen, available phosphorous, pH, exchangeable bases, and cation exchange capacity of the soils. Surface soil total carbon, and total nitrogen in conservation forest, pine forest, and home garden varied significantly among periods of sampling but were generally stable. Total carbon, total nitrogen, available phosphorous, pH, and exchangeable bases significantly increased immediately after fire while Al saturation and cation exchange capacity significantly decreased. Soil nutrients still accumulated 1 yr after fire but depleted and returned to the pre-fire levels by year 2. Although fallowing aggraded the burnt sites, the nutrient levels in the burnt sites were still lower than those in the unburnt sites. Conversion of natural forest into human-managed ecosystems significantly reduced number of spores, species richness, and Shannon- Wiener’s Diversity index (H’) of vesicular arbuscular mycorrhizal fungal communities. Both predominant genus and species composition of VAM fungal community changed as a result of ecosystem conversion and fire occurrence. Similarly, bacterial populations decreased as the natural forest was converted into human-managed ecosystem except for the P-solubilizing bacteria in PF. The lowest population of all microbial groups was found in HG, reflecting that increases in agricultural practices had caused more pressure on microbial population. The immediate effect of wildfire on VAM fungal and bacterial community was striking but short-lived. Species richness and Shannon-Wiener Diversity index (H’) of VAM fungal community significantly decreased immediately after the fire but increased three months after the fire. Amongst the bacterial groups investigated, nitrifying bacteria were the most severely affected. Although fluctuating significantly with time, bacterial populations returned to the pre-fire levels two years after the fire. The temporal improvement in soil nutrients (abiotic factors) after fire was clearly an important factor for the increases in microbial population. However, the lag time of recovery showed by Rhizobia also reflected the importance of biotic factors (vegetations) in determining the survival of certain groups of soil microorganisms. Considering the long-term productivity, the declines in nutrient pools in the Acacia mangium site might have significant implications because Acacia mangium plantation has about 6- to 7-yr rotation. On the other hand continuous and regular organic matter turnover, for example in the PF and HG sites, successfully maintains levels of nutrient pools mainly C and N comparable to those found in the CF sites. The high intra-periodic variation reported here suggests that care must be taken in selecting control site and suggests the necessity of repeated sampling in order to determine the long-term effects of management practices and the long-term effects of wildfires on the dynamics of microbial populations in soils.
| Item Type: | Thesis (Doctoral) |
|---|---|
| Subjects: | S Agriculture > S Agriculture (General) > S590-599.9 Soils. Soil science. Including soil surveys, soil chemistry, soil structure, soil-plant relationships |
| Divisions: | 05-Faculty of Agriculture > 54294-Soil Science (S1) |
| Depositing User: | Ph.D. Sabaruddin Kadir |
| Date Deposited: | 24 Aug 2025 09:36 |
| Last Modified: | 24 Aug 2025 09:36 |
| URI: | http://repository.unsri.ac.id/id/eprint/182566 |
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