Changes in vegetation and nitrogen mineralization during recovery of a montane subtropical broadleaved forest in North‐eastern India following anthropogenic disturbance

Abstract

Understanding the changes in the plant community and soil nitrogen (N) availability during natural recovery of a forest following clear-cutting is critical to develop post-disturbance forest management strategies. Therefore, post-clearcut changes in vegetation, net N mineralization rates and available N concentrations in soil were studied in a montane subtropical broadleaved forest during the early years of recovery following a chronosequence approach. Two replicate stands were selected for each treatment of old-growth undisturbed forest and recovering forest stands aged 1, 5 and 10 years. Following disturbance, tree species diversity and basal area declined but shrub and herb diversity increased. High percentage dissimilarity among the stands in tree, shrub and herb species composition indicated that species colonization varied with recovery age. NH₄ ⁺-N and NO₃ ^- -N concentrations increased significantly (P < 0.001) following clear-cutting and the increasing trend continued until 5 years post-recovery, after which it declined. While ammonification rate remained unchanged with recovery age, nitrification and net N mineralization rates in 10-year-old and undisturbed forest were significantly greater (P < 0.001) than in 1- and 5-year-old forest, indicating that mineralization rates increased with recovery age. Despite high mineralization rates, low availability of soil N in the later years of recovery was attributed to high N uptake by growing vegetation and leaching because of high rainfall in Cherrapunjee. To ensure N availability during the later years of recovery, we suggest that forest management intervention should encourage aided regeneration of native N-fixing trees, e.g., Myrica esculenta, during the initial years of recovery.