Impact of eco-restoration on nutrient balance in eastern Attappady, Kerala

Abstract

A study on “Impact of Eco-restoration on nutrient balance in eastern Attappady, Kerala” was carried out with the objective of analyzing the nutrient stock and flow of the ecosystem for evaluating the impact of eco-restoration work in eastern Attappady. The study sample included ten plantations, five biomass conservation areas and five non-eco-restored areas spread over seven locations in eastern Attappady. At each study site, a 50 x 50 m2 quadrat was enumerated for trees (GBH ≥ 10 cm) for analyzing the vegetation structure and species composition. Vegetation, soil and litter samples were collected from each sample plots for estimating the nutrient pool and its flow. Stem, leaves and branches were collected from all the tree species encountered during the study. Soil samples were collected up to a depth of 15 cm from all the sample plots and for litter sample collection, litter traps were placed in each sample plot and were collected four times throughout a year with an interval of three months. Organic C, Total N, Total P, Available P, Available K and CEC were estimated from soil. Carbon, N, P and K were estimated from vegetation and litter. Aboveground Biomass (AGB) of the study site was estimated using the universal allometric equation for tropical dry deciduous forests. Rainfall regimes of the region were found to be the main driving forces for the vegetation structure. The vegetation of plantations and BCAs in the locations Agali, Sambarcode and Palliyara, which fall in the wetter region of the study area had higher tree density compared to drier tracts. Floristic diversity studies revealed that species richness were higher among the BCA’s compared to plantations. The vegetation structure and species composition of plantations in the areas with medium rainfall was better than the BCA in drier tracts. The Aboveground Biomass (AGB) was observed to be higher among the BCAs compared to plantations. The higher AGB were correlated to higher density of larger girth class trees. Nutrient stock in vegetation was proportional to the AGB of the area. The vegetation nutrients were higher among the BCAs compared to plantations due to higher AGB. Species composition and richness was a factor which determined the litter turnover of the ecosystem. Litter turnover was higher among the BCAs compared to plantations. Litter turnover rate was the major factor which determines the litter nutrient stock in the area. Litter nutrient accumulation were higher among the BCAs compared to plantations in general. Soil nutrient stock was dependent on the above ground vegetation and its composition of the study area. Soil nutrients were higher among the BCA’s compared to plantations and non-eco-restored areas except for phosphorous which was higher in soils of non-eco-restored areas since it got absorbed in vegetated areas. The nutrient capital was higher among the BCAs compared to plantations and non-eco-restored areas. The total carbon stock of BCAs (44367.19 kg/ha) were found to be higher compared to plantations (24295.33 kg/ha) and non-eco-restored areas (5372.64 kg/ha) due to better vegetation structure and species composition among them. Nitrogen pool and potassium pool were also higher among the BCAs (3417.7 kg/ha and 344.52 kg/ha) compared to plantations (2075.52 kg/ha and 240.51 kg/ha) and non-eco-restored areas (705.6 kg/ha and 162.4 kg/ha). The only exception was in the phosphorous pool which was higher in non-eco-restored areas (1600.7 kg/ha). However, rate of nutrient flow in plantations and BCAs were similar. The study indicates that the nutrient flow pattern of plantation is similar to BCAs and if plantations are provided with adequate protection and management, it may attain the stock levels of BCA in due course.