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PARENT SESSION
Poster Session #65: Global Change.
Friday, August 9. Presentation from 8:00 AM to 9:30 AM. Exhibit Hall B & C, TCC


44

Plant growth responses to timing and magnitude of precipitation Big Bend National Park.

Robertson, Traesha*,1, Walker, Erin1, Zak, John1, Tissue, David1, 1 Texas Tech University, Lubbock, Texas

ABSTRACT- The Hadley Climate Model predicts that winter and summer precipitation will increase by 25% at Big Bend National Park in the Chihuahuan Desert in Texas. Water availability in arid ecosystems is often the crucial limiting factor for plant recruitment and growth, nutrient dynamics, and ecosystem productivity. However, there are plant species differences in response to water availability that are dependent on photosynthetic pathway, plant morphology and root architecture. Many desert C3 plants respond most strongly to winter precipitation, whereas C4 grasses respond primarily to summer precipitation. CAM plants can respond to both summer and winter precipitation events. To address these issues, we have altered the amount and timing of precipitation on three dominant plant species within the sotol-grassland community: sotol (Dasylirion leiophyllum; C3), sideoats grama (Bouteloua curtipendula; C4) and brownspine prickly pear (Opuntia phaeacantha; CAM). We have established 36 plots covering 4 ha, with each plot containing one of the selected plant species. Experimental manipulations include: 1) no water addition, 2) summer water addition, 3) winter water addition, and 4) summer and winter water addition. In the first year of study, following the winter water addition, we found minimal growth response (i.e. changes in leaf area, leaf volume, and dry mass) for the C3, C4, and CAM plants.

KEY WORDS: Chihuahuan Desert, global change, growth response, winter precipitation