EFFECT OF FOREST FIRE ON SOIL AND REGENERATION OF TREE SPECIES IN TROPICAL DRY DECIDUOUS FOREST OF RANCHI FOREST DIVISION, JHARKHAND
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Date
2023
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Birsa Agricultural University, Ranchi
Abstract
The present investigation entitled “Effect of forest fire on soil and regeneration of tree species in tropical dry deciduous forest of Ranchi forest division, Jharkhand” was conducted in Nawadih beat of Burmu range forest, Ranchi during the year 2022-2023, with the following objectives: (i) To compare the phytosociology and regeneration of tree species under fire affected and unaffected areas of tropical dry deciduous forest. (ii) To understand the influence of forest fire on soil physico-chemical properties in comparison to undisturbed areas of tropical dry deciduous forest. (iii) To evaluate the impact of fire on phytosociology, regeneration of tree species and physico-chemical properties of soil in disturbed and undisturbed areas through correlation studies.
For both fire-affected and -unaffected sites, ten quadrats were laid. Using information from the Jharkhand Forest Department, the plots for fire-affected areas were located. The research was carried out in dry deciduous forests in various vegetation layers. To lay the quadrats, the simple random sampling approach was adopted. Based on estimates using the species area curve method, 12 m × 12 m quadrats were considered for trees; two 5 m x 5 m sub-plots were considered for shrubs; five 2 m x 2 m sub-plots were considered for regeneration; and five 1 m x 1 m sub-plots were considered for herbs within the main quadrat. The variations in the structure, diversity, and composition of the vegetation in the different layers were measured.
At the fire-undisturbed site, a total tree density of 1546 trees per hectare were observed, while the investigation at the fire-disturbed site recorded a total of 1384 trees per hectare. The overall tree basal area ranged from 41.59 to 43.79 m2 per hectare. Shrub encounters amounted to 2260 individuals per hectare at the undisturbed site, whereas the disturbed site documented 2580 shrubs per hectare. The cumulative shrub basal area varied from 3.00 to 3.72 m2 per hectare. For herbs, 1,89,400 individuals per hectare were identified at the undisturbed site, compared to 2,85,000 individuals per hectare at the disturbed site. The overall herb basal area ranged from 0.86 to 0.93 m2 per hectare. Shorea robusta exhibited the highest Importance Value Index (IVI) in the tree layer at both sites. Meanwhile, Eupatorium odoratum displayed the highest IVI among shrubs at both sites, and at the undisturbed and disturbed sites, Cynodon dactylon and Chrysopogon aciculatus demonstrated the highest IVI among herbs, respectively.
Concerning regeneration, the sites unaffected by fire exhibited a favorable status with 58% of tree species displaying good regeneration, 26% regenerating fairly, and 16% showing no signs of regeneration. In contrast, at fire-affected sites, 53% of tree species showcased good regeneration, 24% displayed poor regeneration, and 23% recorded no regeneration. The diversity analysis of regeneration indicated a density range of 2200 to 9700 individuals per hectare. In the sub-whippy layer, the undisturbed site registered 7300 individuals per hectare compared to 2200 individuals per hectare at the disturbed site. In the recruits’ layer, 9700 individuals per hectare
were observed at the undisturbed site, while the disturbed site recorded 3100 individuals per hectare. Shorea robusta exhibited the highest dominance with an Importance Value Index (IVI) ranging from 61.44 to 113.94 across all regeneration layers at both undisturbed and disturbed sites.
The Shannon index exhibited a range of 1.659 to 2.328 for regeneration and 1.986 to 2.865 for the phytosociology of trees, shrubs, and herbs. Concentration of dominance varied between 0.746 to 0.874 for regeneration and 0.761 to 0.937 for the phytosociology of trees, shrubs, and herbs. Equitability spanned from 0.793 to 0.923 for regeneration and 0.734 to 0.957 for trees, shrubs, and herbs. Species richness displayed a range of 0.852 to 1.574 for regeneration and 0.891 to 2.451 for trees, shrubs, and herbs.
The soil analysis results (0 to 15 cm depth) for both sites revealed significant disparities in physico-chemical properties. Notably, differences were observed in bulk density (1.35 for the fire-undisturbed site and 1.42 for the fire-disturbed site), soil moisture content (7.08% for the undisturbed site and 4.45% for the disturbed site), soil pH (5.36 for the fire-undisturbed site and 5.11 for the fire-disturbed site), soil organic carbon (0.42% for the fire-undisturbed site and 0.33% for the fire-disturbed site), available nitrogen (247.74 kg ha-1 for the fire-undisturbed site and 206.98 kg ha-1 for the fire-disturbed site), available phosphorous (7.28 kg ha-1 for the fire-undisturbed site and 3.62 kg ha-1 for the fire-disturbed site), and available potassium (205.86 kg ha-1 for the fire-undisturbed site and 187.71 kg ha-1 for the fire-disturbed site). Additionally, soil texture was identified as sandy loam at both sites, with variations in textural fractions, specifically a lower value of clay fraction at the fire-disturbed site. The soil color for both sites was recorded as reddish-yellow, with the fire-affected site displaying a lower value of chroma.
According to the Pearson correlation analysis, there was a significant positive correlation between the basal areas of established, woody, whippy, and sub-whippy regeneration and the density of established (r = 0.989**), woody (r = 0.963**), whippy (r = 0.938**), and sub-whippy regeneration (r = 0.961**) respectively. Additionally, a significant negative correlation was observed between available phosphorus and soil moisture content (r = -0.809**), as well as between available nitrogen and the basal area of herbs (r = -800**).
The findings of the current study indicate that fire disturbance has a considerable impact on the regeneration, soil physico-chemical properties, and phytosociology of shrubs and herbs. Consequently, there is a pressing need for collaborative efforts from both governmental organizations and local communities to preserve the indigenous diversity of Jharkhand's forests.