Current Research Projects

Our LTER research integrates studies on multiple global change drivers and pulse precipitation dynamics to determine how they affect the rate at which this grass- to shrubland transition occurs. Together, our research across multiple time and space scales is yielding a comprehensive understanding of how key abiotic drivers affect pattern and process in aridland ecosystems.

Humans are causing significant global environmental changes, including climate change, nitrogen (N) deposition, and invasion of woody species into grasslands. Although each of these factors has major impacts on plant community composition, it is not known how these factors will interact to affect ecosystem dynamics in the future. Furthermore, although arid and semiarid systems cover approximately a third of the earth’s surface, few experimental warming studies have been conducted in these systems. We are conducting a multi-factorial global change field experiment in an arid grassland community at the Sevilleta.

Savanna grassland distribution, structure and function are a product of three interacting drivers - fire, grazing by large herbivores, and extreme climatic fluctuations. Although all savanna grasslands share these drivers, evidence suggests that fire and grazing affect ecosystem structure and function in fundamentally different ways in southern Africa (South Africa (SA), in particular) and North America (NA).

Woody plant encroachment into grasslands is a global phenomenon that results from a variety of global change drivers. Over the last 150 years the southwestern US has undergone dramatic changes in the composition and structure of vegetation due to range expansion by Larrea and Prosopis spp.

The objective of the Monsoon Rainfall Manipulation Experiment (MRME) is to understand changes in ecosystem structure and function of semiarid grassland caused by increased precipitation variability, which alters the pulses of soil moisture that drive primary productivity, community composition and ecosystem functioning. The overarching hypothesis being tested is that changes in event size and variability will have differential effects on grassland dynamics and creosote invasion of desert grassland.

Aridland ecosystems are strongly limited by water availability and potentially by nitrogen availability, as well. The unimodal model of productivity and species diversity predicts that diversity will increase with productivity in low productivity systems such as desert grasslands. We analyzed the relationship between aboveground net primary production (ANPP), species diversity and climate variability in a long-term nitrogen fertilization experiment in low productivity desert grassland at the Sevilleta.

The Sevilleta LTER is a participant in the Nutrient Network (NutNet).