Abstract
Grasslands in the upper Indus basin provide a resource base for nomadic livestock grazing which is one of the major traditional livelihood practices in the area. The study presents climate patterns, grassland phenology, productivity and spatio-temporal climate controls on grassland growth using satellite data over the upper Indus basin of the Himalayan region, Pakistan. Phenology and productivity metrics of the grasses were estimated using a combination of derivative and threshold methods applied on fitted seasonal vegetation indices data over the period of 2001–2011. Satellite based rainfall and land surface temperature data are considered as representative explanatory variables to climate variability. The results showed distinct phenology and productivity patterns across four bioclimatic regions: (i) humid subtropical region (HSR)—late start and early end of season with short length of season and low productivity (ii) temperate region (TR)—early start and late end of season with higher length of season and moderate productivity (iii) sub alpine region (SAR)—late start and late end of season with very high length of season and the most productive grasses, and (iv) alpine region (AR)—late start and early end of season with small length of season and least productive grasses. Grassland productivity is constrained by temperature in the alpine region and by rainfall in the humid sub-tropical region. Spring temperature, winter and summer rainfall has shown significant and varied impact on phenology across different altitudes. The productivity is being influenced by summer and annual rainfall in humid subtropical regions, spring temperature in alpine and sub-alpine regions and both temperature and rainfall are contributing in temperate regions. The results revealing a strong relationship between grassland dynamics and climate variability put forth strong signals for drawing more scientific management of rangelands in the area.
Highlights
Grasslands occupy around half of the Hindu Kush Himalayan region, which provides a resource base for nomadic livestock grazing as well as associated ecosystem services such as maintaining biodiversity and avoiding the erosion that might result from cropping systems
Normalised Difference Vegetation Index (NDVI) data, from moderate resolution sensor (MODIS) images taken at 16-day intervals and 250 m spatial resolution provided in a standard product (MOD13Q1, Level 3 Product), were used to extract phenology and productivity metrics (PPMs) of the grasslands: start of growing season (SGS), end of growing season (EGS) and length of growing season (LGS), seasonally integrated NDVI (SIN), and maximum seasonal NDVI (MSN) [24] (Table S2)
Rainfall was relatively low in all elevation zones in autumn; in the humid subtropical region, it was highest in summer, whereas in the upper part of the temperate region it was lower in summer than in winter or spring; and in the sub alpine and alpine regions, it was highest in spring
Summary
Grasslands occupy around half of the Hindu Kush Himalayan region, which provides a resource base for nomadic livestock grazing as well as associated ecosystem services such as maintaining biodiversity and avoiding the erosion that might result from cropping systems. The high altitude grasslands in mountainous areas including the Himalayas are thought to be especially critical in terms of susceptibility to climate change [1,2]. The pastoralists must adapt to the changes in climatic conditions to ensure sustainable grazing plans, but they need support including providing information on vegetation and climate patterns in the area. A systematic assessment is needed to understand the grasslands dynamics in the region as a basis for devising appropriate policies for management
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