Abstract
Forest cover dynamics are an important indicator for climate change as well as for land conversion studies. Based on an analysis of 30 years of Landsat data a forest cover time series was generated and analyzed for the Dhofar mountains in Oman. The Dhofar mountains in Southern Oman with its semi-arid cloud forest is an important asset for livestock, water resources, and tourism. In this study we investigated whether forest cover trends are distinguishable and what impact forest cover changes have on water availability. To cope with gaps in the Landsat dataset the Dhofar mountains were divided into regions of interest (ROIs) that were based on hydrologic catchment boundaries. The results show, that, despite increasing pressure from tourism and increasing livestock numbers, the forest cover shows slight but not significant increases in most ROIs and significant forest cover increases in three ROIs. Overall, forest cover during the past 30 years is at least stable and most probably slightly increasing. With regard to water resources results show that, the impact of cloud forest interception amounts to an additional subcanopy water input of about 15 to 150 % of annual rainfall. This additional water is only available below tree cover. Part of that water is, of course used by plant transpiration, however, the stemflow portion which is exceptionally high in this region infiltrates directly into deeper soil layers and eventually leads to groundwater recharge.
Highlights
Forest cover dynamics are an important indicator for climate change (Lenoir et al, 2008; Füssel et al, 2017) and can have a substantial impact on local water resources (Sahin and Hall, 1996)
For the study region we show, that, land cover threats are eminent through the development of touristic infrastructure and livestock pressure, forest cover is stable and even slightly increasing in some parts of the Dhofar mountains
Using reference pixels defined in Google Earth for forest and for grassland pixels, Normalized Difference Vegetation Index (NDVI) values from Landsat 5, 7, and 8 from 1987 to 2016 were extracted
Summary
Forest cover dynamics are an important indicator for climate change (Lenoir et al, 2008; Füssel et al, 2017) and can have a substantial impact on local water resources (Sahin and Hall, 1996). Tourism as well as agriculture have an impact on the natural forest vegetation as infrastructure in terms of roads or recreational areas are constantly being built up in the mountains and as increasing livestock numbers forage on the vegetation. These threats to the natural forest vegetation are reported, only few studies exist (e.g., Schlecht et al, 2014; Galletti et al, 2016) and no consistent, long-term analysis of forest cover, that would allow for a multi-annual trend analysis throughout the Dhofar mountains is available
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