QUANTIFYING THE VEGETATION HEALT BASED ON THE RESILIENCE IN AN ARID SYSTEM

Abstract

Proper management of natural ecosystems is not possible without the knowledge of the health status of its components. Vegetation, as the main component of the ecosystem, plays an important role in its health.
One of the key determinants of vegetation health is its resilience in the face of environmental disorders. is research was conducted in parts of the Namakzar-e Khaf watershed in Northeast of South Khorasan Province with the aim of quantifying the vegetative resilience on behalf of the ecosystem health in response to long-term precipitation changes. First, the annual precipitation standardization was performed
during a thirty-year period by the SPI method. en, the average variation in TNDVI index obtained
from the Landsat satellite images was examined and the resilience was tested by calculating the four eective factors (amplitude, malleability, damping and hysteresis). According to the results, the amplitude in the survey period was 6.04% and the vegetation has had dierent values of damping over the years. e
most prominent example of vegetation resilience occurred between 1986 and 1996, with malleability of
0.7 and damping of zero. Vegetation in this period, aer the elimination of drought eects (1986), has not only returned to the amount of vegetation of reference year with severe precipitation (1996) but also increased by 0.25%. is increase, as the index of hysteresis, has been presented for the rst time in the
ecosystem health discussion quantitatively in the present study. A set of quantitative calculations showed
that despite reduced annual precipitation and drought events, the vegetation has been able to maintain its
resilience, which indicates the health of vegetation in the studied ecosystem.-