COS 109-6
The relationship between precipitation and aboveground vegetation biomass in arid grasslands: Exploring spatial and temporal dynamics

Thursday, August 14, 2014: 3:20 PM
302/303, Sacramento Convention Center
Jessica P. Parker, Natural Resource Management, New Mexico Highlands University, Las Vegas, NM

With an increasing focus on the importance of scale and hierarchy dynamics in ecological research, climate can serve as the broader context upon which to study how cross-scale spatial and temporal interactions influence ecosystems. It has long been recognized that climate is a key driving variable of the structure and function of grassland systems. However, the relationship between climate and vegetation production has yet to be consistently established. This may indicate that complex, non-linear interactions are occurring and that a more comprehensive, cross-scale, and long-term approach is need to understand the abiotic-biotic dynamics. Previous studies using the normalized difference vegetation index (NDVI) for vegetation cover have documented a positive linear correlation between rainfall and vegetation for arid grassland systems in North America and Africa. Using ten years of data from southwestern New Mexico, we analyzed the cross-scale relationship between annual and seasonal precipitation and above-ground vegetation biomass of Chihuahuan desert grasslands to determine the nature, strength, and direction of the relationship. We used spatial biomass and precipitation data at the m² and ha scale and temporal precipitation data from the current and previous season and years to detect a correlation between rainfall and vegetation biomass production.


Annual precipitation and above-ground vegetation biomass showed significant interannual differences from 2000-2009 at both the m² and ha scale. The occurrence of a severe drought from 2002-2003 provided optimal conditions for determining the magnitude of the effect climate has on biomass and detecting the presence of precipitation thresholds for biomass production. No relationship was detected between either seasonal or annual average precipitation, from either the current or previous season or years, and biomass from 2000-2009. However, both the magnitude and spatial variation of precipitation influenced the spatial and temporal response of biomass. Above-average precipitation with low spatial variation was correlated with an increase in spatial variation of biomass with a two-year lag time. Below-average precipitation with low spatial variation was correlated with lower spatial variation in biomass the following year until above-average precipitation generated a two-year time lag in the spatial response of biomass. From 2007-2008, there was a two-fold increase in vegetation biomass following a year of above-average precipitation. This study suggests that the relationship between precipitation and aboveground biomass is complex and non-linear while demonstrating discrete thresholds. Moderating factors may include the timing, intensity, and duration of precipitation events interacting with environmental conditions across a range of scales.