Multivariate analyses of the vegetation of the western Himalayan forests of Muzaffarabad district, Azad Jammu and Kashmir, Pakistan

摘要

Muzaffarabad district, Azad Jammu and Kashmir, Pakistan is part of the western Himalaya and rich in phytodiversity, but until now little was known about its plant diversity on larger spatial scale and vegetation composition through multivariate statistical tools. To fill this research gap, the whole district was ecologically explored for the collection of field data from August 2014 to July 2016. For vegetation studies, a total of 16 altitudinal transects comprising 110 sampling stations (samples) with 990 plots were studied by using a stratified random vegetation sampling method. Different multivariate statistical tools including Monte Carlo permutation test, Indicator species analysis, hierarchical clustering, ordination, variation partitioning and multi-response permutation procedures tests were used for the first time for the study area to elucidate the number of significant vegetation groups, ranking and placement of plant species in these groups, classification of vegetation units, detection of important gradients, importance of groups of environmental variables and pairwise compositional differences of the species groups respectively. The results showed that all the recorded 343 plant species belong to seven significant plant associations which were further placed into 5 major forest types. Out of the total 19 variables studied, CCA detected the significant contribution of the majority (simple effects: 12; unique effects: 8) of them. The latter (unique effects) in descending order included altitude, forest cover, deforestation, community maturity, forest density, latitude, slope aspect, and longitudinal variations. Similarly, variation partitioning results depicted that topography was the leading driver affecting vegetation distribution, followed by the biotic and edaphic factors. The forest edges, especially the sub-alpine ecosystem, were most diverse, supported higher tree density and also faced maximum deforestation pressure. Furthermore, rangelands in the temperate to alpine zones were affected by heavy overgrazing. Due to the disrupted local ecosystem functioning, the study area needs proper management and conservations plans to save its biodiversity wealth in this part of western Himalaya.