Monitoring Effects of Land Cover Change on Biophysical Drivers in Rangelands Using Albedo

Zahn Münch,Anthony Palmer,Lesley Gibson

doi:10.3390/land8020033

Zahn Münch, Anthony Palmer + Show 1 more

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https://doi.org/10.3390/land8020033

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Abstract

This paper explores the relationship between land cover change and albedo, recognized as a regulating ecosystems service. Trends and relationships between land cover change and surface albedo were quantified to characterise catchment water and carbon fluxes, through respectively evapotranspiration (ET) and net primary production (NPP). Moderate resolution imaging spectroradiometer (MODIS) and Landsat satellite data were used to describe trends at catchment and land cover change trajectory level. Peak season albedo was computed to reduce seasonal effects. Different trends were found depending on catchment land management practices, and satellite data used. Although not statistically significant, albedo, NPP, ET and normalised difference vegetation index (NDVI) were all correlated with rainfall. In both catchments, NPP, ET and NDVI showed a weak negative trend, while albedo showed a weak positive trend. Modelled land cover change was used to calculate future carbon storage and water use, with a decrease in catchment carbon storage and water use computed. Grassland, a dominant dormant land cover class, was targeted for land cover change by woody encroachment and afforestation, causing a decrease in albedo, while urbanisation and cultivation caused an increase in albedo. Land cover map error of fragmented transition classes and the mixed pixel effect, affected results, suggesting use of higher-resolution imagery for NPP and ET and albedo as a proxy for land cover.

Highlights

Changes in land use and land cover (LULC) cause bio-geophysical changes to the land surface that disturb the Earth’s surface energy balance [1], which have noticeable impacts on ecological and environmental systems
Biophysical characteristics associated with land cover types are responsible for carbon storage in the landscape, and affect water use of vegetation driven by eco-hydrological processes [2], such as in grasslands in water scarce catchments in South Africa
Land use and land cover change in the selected catchments have affected ecosystem services provided by land cover classes, those provided by grasslands

Summary

Introduction

Changes in land use and land cover (LULC) cause bio-geophysical changes to the land surface that disturb the Earth’s surface energy balance [1], which have noticeable impacts on ecological and environmental systems. Biophysical characteristics associated with land cover types are responsible for carbon storage in the landscape, and affect water use of vegetation driven by eco-hydrological processes [2], such as in grasslands in water scarce catchments in South Africa. Ecosystem changes can be detected and quantified using biophysical parameters derived from multi-temporal satellite observations of the land surface [3]. Primary drivers of change within the rural catchments in the Eastern Cape have been linked to woody encroachment, commercial afforestation, urbanization, increased dryland cultivation and rangeland degradation to the detriment of native grasslands [4]. Conversion of grassland to woody vegetation results in higher actual evapotranspiration (ET) due to increases in biophysical attributes, such as leaf area and rooting depth.

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