|Estell, Richard - Rick|
|CIBILS, ANDRES - New Mexico State University|
|PEINETTI, H. RAUL - Universidad Nacional De La Pampa|
Submitted to: Frontiers of Agricultural Science and Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/22/2017
Publication Date: 3/1/2018
Citation: Browning, D.M., Spiegal, S.A., Estell, R.E., Cibils, A., Peinetti, H. 2018. Integrating space and time: A case for phenological context in grazing studies and management. Frontiers of Agricultural Science and Engineering. 5(1):44-56. https://doi.org/10.15302/j-FASE-2017193.
Interpretive Summary: Livestock grazing is a common agricultural practice in arid grasslands and savannas worldwide and localized overuse of specific areas can result in loss of perennial grasses and soil erosion. We integrated a measurement of vegetation greenness (Normalized Difference Vegetation Index; NDVI) obtained from satellite imagery with movement of beef cattle wearing GPS collars in a large pasture to evaluate the relationship of cattle distribution and plant growth stage (phenology). Our data showed that cattle foraging behavior was related to seasonal stages derived from NDVI. Cattle tended to explore smaller areas of the pasture and spent more time foraging as the pasture became greener. The ability to monitor vegetative greenness on large tracts of land in real time using free satellite imagery may improve livestock management on rangelands and provide a mechanism to improve our ability to compare findings from grazing studies conducted at different locations and times of year. These capabilities can benefit state and federal land managers, private land owners, and ecologists.
Technical Abstract: In water-limited landscapes, patterns in primary production are highly variable across space and time. Livestock grazing is a common agricultural practice worldwide and a concern is localized overuse of specific pasture resources that can exacerbate grass losses and soil erosion. On a research ranch in New Mexico (MAP = 217 mm), we demonstrate with a quantitative approach that annual seasons vary greatly and examine foraging patterns in Angus-Hereford (Bos taurus) cows. We define five seasonal stages based on MODIS NDVI: Pre-Greenup, Greenup, Peak Green, Drydown, and Dormant and examine livestock movements in 2008. Daily distance traveled by cows was greater and foraging area expanded during periods with higher precipitation. A regression model including minimum NDVI, rainfall, and NDVI*rainfall explained 81% of the seasonal variation in distance traveled by cows (P < 0.01). Cows explored a daily average 81.1 ha while foraging but tended to explore smaller areas as the pasture became greener (Greenup, Peak Green). Cows foraged an average 9.7 hours daily and spent more time foraging as pastures became greener. Our findings suggest that phenological context can expand the capacity to compare and integrate findings and facilitate meta-analyses of grazing studies conducted at different locations and times of year.