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.

Fine Root and Soil Nitrogen Dynamics during Stand Development Following Shifting Agriculture in Northeast India

“…The recovery of the N cycle with increasing stand age following disturbance showed a pattern similar to that seen in many other tropical forests [14,51,52], albeit not all [53], with increases in soil mineral N concentrations along with increased N-mineralization rates during succession. The increasing dominance in NH 4 -N over NO 3 -N with older stand age reflects a change in N cycling through the loss or rapid uptake of NO 3 -N in initial successional stages followed by accumulation of NH 4 -N in later successional stages leading to a "tighter" N cycle.…”

Assessing Restoration Potential of Fragmented and Degraded Fagaceae Forests in Meghalaya, North-East India

“…The subtropical broad-leaved wet hill forests of Meghalaya are highly diverse, and part of the Indo-Burma biodiversity hotspot, which is primarily dominated by broad-leaved oak-laurel forests [37][38][39][40]. Various studies have been conducted in these forests to study species diversity, composition and structure [37,[39][40][41], natural regeneration [42][43][44], nutrient dynamics [45,46], and litter decomposition [47,48].…”

“…On these degraded sites, a large portion of the topsoil has been eroded in this region of very heavy rainfall (averaging >11,000 mm a year). The remaining soil is shallow, nutrient-poor and acidic, and has low mechanical stability [46,52]. Consequently, forests in the region that once provided continuous cover, today, are fragmented into small remnant patches (Figure 1), which are often in a degraded state [46,53].…”

“…The remaining soil is shallow, nutrient-poor and acidic, and has low mechanical stability [46,52]. Consequently, forests in the region that once provided continuous cover, today, are fragmented into small remnant patches (Figure 1), which are often in a degraded state [46,53]. About 6967 patches or forest fragments of varying sizes have been identified in Meghalaya [51].…”

Plant-Soil Properties Associated with Nitrogen Mineralization: Effect of Conversion of Natural Secondary Forests to Larch Plantations in a Headwater Catchment in Northeast China

“…Numerous previous studies and practices have shown that seasonal changes in N mineralization result in patterns with the highest mineralization rates in the summer and the lowest rates in the winter, which appears to follow seasonal patterns of temperature and precipitation [8][9][10][11]. Soil temperature, moisture, and precipitation patterns are important drivers of soil N transformations, and each of these seasonal climate conditions may have different impacts on various forest types [12]. Forest types with varying plant communities may have different influences on the N cycle due to differences in the physiology, morphology, nutrient requirements, and life histories of various plant species [13][14][15].…”