<abstract xmlns="http://www.w3.org/1999/xhtml"><p>Soil moisture plays a key role in the ecological capability of arid and semi-arid woodland. Reducing soil moisture due to frequent droughts causes pest prevalence and disease outbreak and the consequence of forest dieback. On the other hand, soil moisture is strongly correlated with the amount of radiation received on the Earth’s surface. The sun’s radiation is traditionally described often by aspect and sometimes by toposhape. The use of the hillshade map for estimating solar radiation is possible through developing GIS. The present study aimed to compare the relationship and the ability of these indices to describe the phenomenon of arid and semi-arid woodland decline better and more accurately in a case study in the west of Iran. To this aim, the aspect and toposhape layers were generated in 5 and 12 classes, respectively. Then, the hillshade map in range of 0-255 was made during the peak of summer heat. The comparison of the dieback ratio in the three characteristic histograms showed that the shade index, unlike the other two indicators, had a significant effect on forest drought (R2=0.91 for linear equation and R2=0.94 for quadratic equation). The results indicated that the application of hillshade in describing and analysing ecological processes by relying on soil moisture such as woodland dieback is superior to the other two indicators. It is suggested that this index be used to obtain a risk model to predict woodlands dieback which are under the pressure of frequent droughts due to climate change or other mortal factors.</p></abstract>

Soil moisture plays a key role in the ecological capability of arid and semi-arid woodland. Reducing soil moisture due to frequent droughts causes pest prevalence and disease outbreak and the consequence of forest dieback. On the other hand, soil moisture is strongly correlated with the amount of radiation received on the Earth’s surface. The sun’s radiation is traditionally described often by aspect and sometimes by toposhape. The use of the hillshade map for estimating solar radiation is possible through developing GIS. The present study aimed to compare the relationship and the ability of these indices to describe the phenomenon of arid and semi-arid woodland decline better and more accurately in a case study in the west of Iran. To this aim, the aspect and toposhape layers were generated in 5 and 12 classes, respectively. Then, the hillshade map in range of 0-255 was made during the peak of summer heat. The comparison of the dieback ratio in the three characteristic histograms showed that the shade index, unlike the other two indicators, had a significant effect on forest drought (R2=0.91 for linear equation and R2=0.94 for quadratic equation). The results indicated that the application of hillshade in describing and analysing ecological processes by relying on soil moisture such as woodland dieback is superior to the other two indicators. It is suggested that this index be used to obtain a risk model to predict woodlands dieback which are under the pressure of frequent droughts due to climate change or other mortal factors.

The Role of Hillshade, Aspect, and Toposhape in the Woodland Dieback of Arid and Semi-Arid Ecosystems: A Case Study in Zagros Woodlands of Ilam Province, Iran

Agricultural Research, Extension and Education, Agriculture and Natural resources Research Center of Ilam

Department of Forest Sciences, Faculty of Agriculture

Journal of Landscape Ecology

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Soil moisture plays a key role in the ecological capability of arid and semi-arid woodland. Reducing soil moisture due to frequent droughts causes pest...

The Role of Hillshade, Aspect, and Toposhape in the Woodland Dieback of Arid and Semi-Arid Ecosystems: A Case Study in Zagros Woodlands of Ilam Province, Iran

Published Online: Aug 06, 2019

Page range: 79 - 91

Received: Dec 03, 2018

Accepted: May 31, 2019

DOI: https://doi.org/10.2478/jlecol-2019-0011

Keywords
Arid ecosystems, Aspect, Dieback, Decline, Hillshade, Toposhape, Zagros woodland

© 2019 Ali Najafifar et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

The Role of Hillshade, Aspect, and Toposhape in the Woodland Dieback of Arid and Semi-Arid Ecosystems: A Case Study in Zagros Woodlands of Ilam Province, Iran

Published Online: Aug 06, 2019

Page range: 79 - 91

Received: Dec 03, 2018

Accepted: May 31, 2019

DOI: https://doi.org/10.2478/jlecol-2019-0011

KeywordsArid ecosystems, Aspect, Dieback, Decline, Hillshade, Toposhape, Zagros woodland

© 2019 Ali Najafifar et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Keywords
Arid ecosystems, Aspect, Dieback, Decline, Hillshade, Toposhape, Zagros woodland