| Popis: |
Recent studies suggest that two factors including climate change (especially precipitation) and human land use management (HLUM) are primarily driving greening trend around the world. However, studies targeting the impact of both factors on different vegetation layers (i.e. herbs, shrubs and tree layers) are lacking. This study hypothesize that precipitation relatively influence the under-storey vegetation cover more quickly, and HLUM (say afforestation/reforestation, deforestation) is more important towards top-storey layer. To investigate this, 13 randomly selected permanent stations in the wild natural west Himalayan coniferous forests of Sudhan Gali, Pakistan were explored from 2000-2016 to collect vegetation health data by two ways; Ground data (i.e. cover estimation of three layers), and indirect remote sensing (RS) data (i.e. MODIS NDVI/EVI 16-days-time series). Deforestation and grazing pressure as HLUM were measured by using some new and more intuitive mathematical operations, and climatic data (1979-2018) was also collected and compared. The results depicted that there is an overall greening trend in the study area coupled with significant increase in average herbaceous cover, NDVI, EVI and precipitation during 2009-2016. Contrastingly, high elevation microhabitats are facing maximum cover loss (especially top-storey), and have negative seasonal Sen’s slope values of the studied time series. The distance-based Redundancy Analysis (db-RDA) results confirmed that variations in RS-data were significantly explained by precipitation and herbaceous cover only. This study concluded that overall greening trend was driven by precipitation, and not remarkably by HLUM by supporting under-storey vegetation, whereas, top-storey tree layer is still declining, and need immediate attention. |
