Assessment of Downscaling Planetary Boundaries to Semi-Arid Ecosystems with a Local Perception: A Case Study in the Middle Reaches of Heihe River

Arid and semi-arid ecosystems represent a crucial but poorly understood component of the global water cycle. Taking a desert ecosystem as a case study, we measured sap flow in three dominant shrub species and concurrent environmental variables over two mean growing seasons. Commercially available gauges (Flow32 meters) based on the constant power stem heat balance (SHB) method were used. Stem-level sap flow rates were scaled up to stand level to estimate stand transpiration using the species-specific frequency distribution of stem diameter. We found that variations in stand transpiration were closely related to changes in solar radiation (Rs), air temperature (T), and vapor pressure deficit (VPD) at the hourly scale. Three factors together explained 84% and 77% variations in hourly stand transpiration in 2014 and 2015, respectively, with Rs being the primary driving force. We observed a threshold control of VPD (~2 kPa) on stand transpiration in two-year study periods, suggesting a strong stomatal regulation of transpiration under high evaporative demand conditions. Clockwise hysteresis loops between diurnal transpiration and T and VPD were observed and exhibited seasonal variations. Both the time lags and refill and release of stem water storage from nocturnal sap flow were possible causes for the hysteresis. These findings improve the understanding of environmental control on water flux of the arid and semi-arid ecosystems and have important implications for diurnal hydrology modelling.

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Climate change adaptation in Semi-Arid Ecosystems: A case study from Ghana

Climate Risk Management ◽

10.1016/j.crm.2019.100206 ◽

2020 ◽

Vol 27 ◽

pp. 100206 ◽

Cited By ~ 2

Author(s):

Mawulolo Yomo ◽

Grace B. Villamor ◽

Mawuli Aziadekey ◽

Felix Olorunfemi ◽

Khaldoon A. Mourad

Keyword(s):

Climate Change ◽

Climate Change Adaptation ◽

Arid Ecosystems ◽

Semi Arid

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A process-based water balance model for semi-arid ecosystems: A case study of psammophytic ecosystems in Mu Us Sandland, Inner Mongolia, China

Ecological Modelling ◽

10.1016/j.ecolmodel.2017.01.005 ◽

2017 ◽

Vol 353 ◽

pp. 77-85 ◽

Cited By ~ 5

Author(s):

Yongmei Huang ◽

Xiaona Yu ◽

Engui Li ◽

Huiying Chen ◽

Liu Li ◽

...

Keyword(s):

Water Balance ◽

Inner Mongolia ◽

Water Balance Model ◽

Arid Ecosystems ◽

Balance Model ◽

Semi Arid

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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

Journal of Landscape Ecology ◽

10.2478/jlecol-2019-0011 ◽

2019 ◽

Vol 12 (2) ◽

pp. 79-91

Author(s):

Ali Najafifar ◽

Jaafar Hosseinzadeh ◽

Abdolali Karamshahi

Keyword(s):

Soil Moisture ◽

Risk Model ◽

Quadratic Equation ◽

The Other ◽

Arid Ecosystems ◽

Strongly Correlated ◽

Ecological Processes ◽

Forest Dieback ◽

Semi Arid

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.

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