The effects of anthropogenic degradation of rangelands on carbon sequestration in the southwestern drylands of U.S.A.

Praveen Noojipady, NASA-GSFC, praveen.noojipady@nasa.gov (Presenter)
Stephen D Prince, University of Maryland, sprince@umd.edu
Khaldoun Rishmawi, University of Maryland/College Park, rishmawi@umd.edu

Rangelands cover nearly 31% of US land surface and store about 5% of the Earth’s total soil organic carbon (C). Clearly the generally low productivity of arid rangelands means that their sequestration rates on area basis are lower than other types of land, but their large area makes them a significant C store in above and below-ground biomass. Furthermore, loss of productivity due to degradation has been reported in rangelands in the south and west US. Moderate Resolution Imaging Spectroradiometer (MODIS) Normalized Difference Vegetation Index and Net Primary Productivity (NPP), together with environmental variables related to productivity were used to map the extent of degradation and to quantify the NPP loss using a Local NPP Scaling (LNS) technique. The 12-year average (2000-2011) NPP reduction within the entire study region was 35.90 Tg C yr-1. Although, Shrubland/Herbaceous landscapes (using the NLCD land cover types) had high overall NPP reductions, the NPP loss per unit area was relatively low. However, the NPP loss per unit area was high (>0.5 Mg C ha-1 yr-1) for forest land cover types. The losses found in different land cover types, land ownership, USDA-Common Resource Areas, and USGS-GAP land cover types were high wherever there was significant forest cover. While, reductions within the Shrublands/Herbaceous can be linked to livestock grazing, the regional reductions within the forest cover types could be due to insect damage, diseases, and fire. Without changes in management, successive droughts, land cover changes, and land use may lead to significant further reductions in C sequestration. On the other hand, changes in management have the potential to increase the C stock and contribution to national and global C sequestration.

Presentation Type:  Poster

Session:  Theme 4: Human influence on global ecosystems   (Mon 4:30 PM)

Associated Project(s): 

• Prince, Steve: Vegetation dynamics in drylands and implications for regional climate: analysis of two decades of observations in the African Sahel ...details

Poster Location ID: 85