Threshold of potential concern: an early way to identify the ecosystem structural thresholds in a grazing gradient

Document Type: Research Paper

Authors

1 GORGAN UNI

2 TEHRAN UNI

Abstract

Identification of ecosystem thresholds is a way to predict future changes and taking the best
management practices in restoration processes. Thresholds are an integral part of nonlinear
responses of ecosystems to disturbances such as climate change or human activities. In this
study, structural threshold of the total patch area and mean patch width in a grazing
gradient were identified using the nonlinear function and the concept of threshold of
potential concern. Other structural features including number of grass, shrub and forb
patches were also measured. The result showed that three-parametric sigmoid functions had
the highest ability to predict structural changes in ecosystem structure within a grazing
gradient radiating out from the livestock stock night corral (camp). The result also showed
that 1 to 2 Km radius from the livestock camp is the critical threshold in ecosystem
structure based on total patch area, landscape organization index and mean patch width
fitting to a sigmoid function. Generally, the area within 2 Km from the camp needed to
receive emergency remedial management actions. The present study showed that the
concept of threshold of potential concern is a useful and early way to predict the thresholds
in the ecosystem for management actions. Also, the present study revealed that threeparameter
sigmoid function provides a much better fit to structural data than other nonlinear
functions.

Keywords