PARENT SESSION
Poster Session 9: Arid Lands and Deserts
Tuesday, August 9, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal
Aboveground annual net primary productivity and species composition response to variation in timing and magnitude of precipitation in Big Bend National Park, Texas.
Robertson, Traesha*,1, van Gestel, Natasja1, Patrick, Lisa1, Zak, John1, Loik, Micheal2, Tissue, David1, 1 Texas Tech University, Lubbock2 University of California - Santa Cruz, Santa Cruz
ABSTRACT- According to global climate change models, greater precipitation and shifts in timing of precipitation are predicted for Big Bend National Park within the next 50 years. Since water availability in arid ecosystems is often the crucial limiting factor, the timing and magnitude of precipitation events can have a significant impact on plant growth and species composition. To investigate how overall increases in seasonal precipitation will affect aboveground annual net primary productivity (ANPP) and species composition (e.g. shrubs, grasses, herbs, and succulents) in a perennial dominate sotol grassland, we have set up a series of plots using the following experimental manipulations: 1) no water addition, 2) summer water addition, 3) winter water addition, and 4) summer and winter water addition. From 2002-2004, natural precipitation events were supplemented by experimentally adding 25% more water as a single winter watering event and/or three summer watering events. For 2002, the annual precipitation was average (357 mm), while annual precipitation for 2003 (410 mm; 14% above average) and 2004 (567 mm; 53% above average) were higher than average. To evaluate the growth response, we measured leaf number, leaf area, aboveground biomass, and reproductive output of three dominant perennial plant species within the sotol grassland community: sotol (Dasylirion leiophyllum; C3), sideoats grama (Bouteloua curtipendula; C4), and brownspine prickly pear (Opuntia phaeacantha; CAM). In the past three years, ANPP of Bouteloua was significantly greater in the winter water treatment but there was no treatment effect on Opuntia or Dasylirion. Water treatment did not alter species richness, including annuals but plant density of some C4 grasses and herbs were increased by supplemental watering in the winter and/or summer.
Key words: annual net primary productivity, plant species richness, global climate change, Chihuahuan Desert