EFFECT OF BURNING ON SPECIES PERFORMANCE AND SOIL BEHAVIOUR OF ARID LAND PLANTATION

Abstract

Observations made after a fire in the experimental field of the Arid Forest Research Institute showed that out of seven species (viz. Acacia nilotica, A. tortilis, Albizia lebbeck, Azadirachta indica, Eucalyptus camaldulensis, Parkinsonia aculeata and Prosopis juliflora) planted, A. lebbeck showed the maximum mortality (45%) and A. indica the minimum (5%). In August 1995, three months after the fire, the growth in terms of height, crown diameter (CD) and collar girth was low in the burned area in all the species except for P. aculeata and E. camaldulensis which showed larger CD, compared to the unburned area. The growth differences were maximum in P. juliflora (viz. 22.2% in height, 22.6% in CD and 3.5% in girth) followed by Albizia lebbeck (12.5,17.8 and 18.2%) and A. tortilis (8.5, 21 and 16.2% in height, CD and girth respectively). The minimum effect of fire was observed in A. indica which showed only 2.1, 4.4 and 1.5% differences in height, crown diameter and girth respectively indicating that A. indica was more hardy to fire than the other species. However, in November 1995, the trend was reverse when a recovery was seen in the burned area with generally better growth than in the unburned area. Such increase in growth parameter was believed to be due to the stimulation of new vegetative growth and branching in the species during the first growing season after the fire. The moisture retention varied significantly between the species. The soil water content was higher under the burned area compared to the unburned area and was due to less usage of water in the area. Soil organic matter content and electrical conductivity increased in the burned area while the pH of the soil showed the reverse trend, and was believed to be due to the effect of organic matter and/or due to leaching of salts from the upper to the lower horizons and other mineral nutrients during the burning of ground vegetation.