Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
Journal topic
Volume 13, issue 16
Biogeosciences, 13, 4721-4734, 2016
https://doi.org/10.5194/bg-13-4721-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Biogeosciences, 13, 4721-4734, 2016
https://doi.org/10.5194/bg-13-4721-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 23 Aug 2016

Research article | 23 Aug 2016

Degradation of net primary production in a semiarid rangeland

Hasan Jackson and Stephen D. Prince Hasan Jackson and Stephen D. Prince
  • University of Maryland, College Park, Maryland 20742, USA

Abstract. Anthropogenic land degradation affects many biogeophysical processes, including reductions of net primary production (NPP). Degradation occurs at scales from small fields to continental and global. While measurement and monitoring of NPP in small areas is routine in some studies, for scales larger than 1km2, and certainly global, there is no regular monitoring and certainly no attempt to measure degradation. Quantitative and repeatable techniques to assess the extent of deleterious effects and monitor changes are needed to evaluate its effects on, for example, economic yields of primary products such as crops, lumber, and forage, and as a measure of land surface properties which are currently missing from dynamic global vegetation models, assessments of carbon sequestration, and land surface models of heat, water, and carbon exchanges. This study employed the local NPP scaling (LNS) approach to identify patterns of anthropogenic degradation of NPP in the Burdekin Dry Tropics (BDT) region of Queensland, Australia, from 2000 to 2013. The method starts with land classification based on the environmental factors presumed to control (NPP) to group pixels having similar potential NPP. Then, satellite remotely sensing data were used to compare actual NPP with its potential. The difference in units of mass of carbon and percentage loss were the measure of degradation. The entire BDT (7.45 × 106km2) was investigated at a spatial resolution of 250 × 250m. The average annual reduction in NPP due to anthropogenic land degradation in the entire BDT was −2.14MgCm−2yr−1, or 17% of the non-degraded potential, and the total reduction was −214MgCyr−1. Extreme average annual losses of 524.8gCm−2yr−1 were detected. Approximately 20% of the BDT was classified as “degraded”. Varying severities and rates of degradation were found among the river basins, of which the Belyando and Suttor were highest. Interannual, negative trends in reductions of NPP occurred in 7% of the entire region, indicating ongoing degradation. There was evidence of areas that were in a permanently degraded condition. The findings provide strong evidence and quantitative data for reductions in NPP related to anthropogenic land degradation in the BDT.

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Anthropogenic land degradation affects many terrestrial processes, including reductions of net primary productivity. This study identifies degradation through spatial comparison of areas with similar growth potentials in six semiarid river basins in Australia using satellite data from 2000 to 2013. Varying severities and rates of degradation were detected across the basins, most linked to indirect management. Evidence of permanent degradation was found despite an overall trend of greening.
Anthropogenic land degradation affects many terrestrial processes, including reductions of net...
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