The Role of Revegetation for Rehabilitation of Sodic Soils in Semiarid Subtropical Forest, India


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A 40-year-old rehabilitated forest developed on a sodic wasteland at Banthra, Lucknow, north India, was studied for the performance of various species in different vegetation strata as well as their overall impact in soil amelioration. The plant communities of the three selected stands (S1, S2, and S3) of this forest were categorized into three vegetation strata: overstory trees, understory trees and shrubs, and a ground layer with scattered herbs and tree seedlings. The three stands contained 44, 19, and 8 species in each stratum, respectively, and three climber species. Importance value index (IVI) and basal area/cover did not show a clear dominance for particular species, and this is identified as a mixed forest with deciduous as well as evergreen species. Therefore, dominant species in each layer were categorized according to an IVI value of 10 and greater than 10% relative basal area. Within each stratum, species richness and plant population density decreased with an increase in plant size. Both species diversity and productivity were relatively high compared to the reference site because of protection from biotic disturbances, which cannot be controlled on the reference site. Creation of new forest on the barren land has contributed significant soil amelioration in the degraded sodic soil of the Indogangetic plains. The soil properties of the three stands did not vary much, although different tree species dominated the stands. Maximum soil amelioration was recorded for total N, followed by mineralized N, available N, and organic carbon contents for the nutritional properties. With regard to chemical properties, exchangeable sodium was greatly reduced in comparison to other properties viz pH, electrical conductivity, cation exchange capacity, and exchangeable Ca content. During 40 years of growth and development of the diverse vegetation in the revegetated forest, microbial C increased to about five times that of the surrounding barren sodic soils. There were no significant changes in soil structure even though the water-holding capacity of the soil improved to about 53% of the once barren land due to a 7-fold increase in organic carbon content.