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United States Department of Agriculture

Agricultural Research Service

Research Project: MANAGEMENT TECHNOLOGIES FOR ARID RANGELANDS

Location: Range Management Research

Title: Spatiotemporal patterns of production can be used to detect state change across an arid landscape

Authors
item Williamson, Jebediah -
item BESTELMEYER, BRANDON
item PETERS, DEBRA

Submitted to: Ecosystems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 7, 2011
Publication Date: February 1, 2012
Repository URL: http://handle.nal.usda.gov/10113/57192
Citation: Williamson, J., Bestelmeyer, B.T., Peters, D.C. 2012. Spatiotemporal patterns of production can be used to detect state change across an arid landscape. Ecosystems. 15:34-47.

Interpretive Summary: Methods to detect and quantify shifts in the state of ecosystems are increasingly important as global change drivers push more systems towards thresholds of change. Temporal relationships between precipitation and aboveground net primary production (ANPP) have been studied extensively in arid and semiarid ecosystems, but rarely has spatial variation in these relationships been investigated at a landscape scale, and rarely has such information been viewed as a resource for mapping the distribution of different ecological states. We used the relationships between satellite-based estimates of ANPP (using the Normalized Difference Vegetation Index; NDVI) and precipitation across eight years to map of varying shrub cover at a landscape scale. The results suggest that remote sensing studies of temporal precipitation-NDVI relationships may be useful for deriving shrub canopy cover estimates in the region, as well as for mapping other ecological state changes characterized by shifts in long-term ANPP, plant functional type dominance, or both.

Technical Abstract: Methods to detect and quantify shifts in the state of ecosystems are increasingly important as global change drivers push more systems towards thresholds of change. Temporal relationships between precipitation and aboveground net primary production (ANPP) have been studied extensively in arid and semiarid ecosystems, but rarely has spatial variation in these relationships been investigated at a landscape scale, and rarely has such information been viewed as a resource for mapping the distribution of different ecological states. We examined the broad-scale effects of a shift from grassland to shrubland states on spatiotemporal patterns of remotely sensed ANPP proxies in the northern Chihuahuan Desert. We found that the Normalized Difference Vegetation Index (NDVI), when averaged across an eight-year period, did not vary significantly between these states, despite changes in ecosystem attributes likely to influence water availability to plants. In contrast, temporal relationships between precipitation and time-integrated NDVI (NDVI-I) modeled on a per-pixel basis were sensitive to spatial variation in shrub canopy cover, a key attribute differentiating ecological states in the region. The slope of the relationship between annual NDVI-I and two year cumulative precipitation was negatively related to, and accounted for 71% of variation in, shrub canopy cover estimated at validation sites using high spatial resolution satellite imagery. These results suggest that remote sensing studies of temporal precipitation-NDVI relationships may be useful for deriving shrub canopy cover estimates in the region, as well as for mapping other ecological state changes characterized by shifts in long-term ANPP, plant functional type dominance, or both.

Last Modified: 9/29/2014