Forest structure and soil properties of mangrove ecosystems under different management scenarios: Experiences from the intensely humanized landscape of Indian Sunderbans

The mangrove stands in and around the densely populated rural areas of Indian Sunderbans are experiencing intense human induced stresses in the forms of widespread small-scale logging, shrimp monoculture, riverside prawn-seed and crab catching, forest trespassing, oil-spill etc. Here, restoration of degraded sites and management of remaining mangroves often remain unsuccessful in serving the dual purposes of biodiversity conservation and sustainable livelihood generation. In this context, the present study aims to evaluate the effects of different management scenarios on vegetation structure and composition as well as soil physico-chemical properties along salinity gradients of two mangrove sites located at village-fringe areas of Sunderbans. Transect cum quadrant-based analyses of vegetation and soil samples were adopted for this purpose in consultation with local community members. The results showed that the mangrove site jointly managed by a non-governmental organization and local forest dependents was performing noticeably better than the other site under surveillance of the State Forest Department. Most of the vegetation (basal area, species diversity index, tree density) and few of the soil (pH, cation exchange capacity, exchangeable Na%, soil total C, and organic C stocks) parameters were in significantly superior conditions in the first site than the later in terms of ecological health (p < 0.01). Soil salinity exhibited significantly negative correlations with the vegetation characteristics of both sites from riverbank towards inland. While the first site represented the growth of a multi-layered canopy with mixed species association, the later site was characterized by mono-specific dominance of the Avicennia varieties primarily due to indiscriminate exploitative activities. Thus, passive restoration or self-recovery of mangroves was considered inadequate in these circumstances for regaining natural ecological functionality. Alternatively, an active human intervention engaging the local forest dependents in decision making and implementation initiatives regarding recognition of actual causes of degradation, zone wise selection of species, fixation of gestation period, protection, and equitable usufruct sharing was recommended as the prerequisite towards successful restoration of these fragile mangrove ecosystems. (C) 2017 Elsevier Ltd. All rights reserved.