Robertson, Traesha , van Gestel, Natasja , Walker, Erin , Zak, John , Tissue, David .
Species composition in a sotol-grassland of Big Bend National Park: Responses to variation in timing and magnitude of precipitation.
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. This change could have a significant impact on species composition. To investigate how overall increases in seasonal precipitation will affect species composition (e.g. shrubs, grasses, herbs, and succulents) in a sotol grassland, we set up a series of plots using the following experimental manipulations: 1) no water addition, 2) summer water addition - S, 3) winter water addition - W, and 4) summer and winter water addition - SW. 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. Over the last three years there has been no significant change in species richness for shrubs, grasses, succulents, or herbs due to water treatment. However there have been changes in plant density due to treatment, specifically in the grasses (Lycurus setosus – SW; Andropogon gerardii – W; Bouteloua hirsute – SW; and Bouteloua curtipendula - S) and a few herbs. There have been few changes in shrub or succulent plant densities. Also, there has been little change in the annual vs perennial composition, although one annual species, Gnaphalium wrightii, has almost vanished from all plots since 2002 while the short lived perennial Erigeron flagellaris has practically doubled in all the plots in 2004.
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1 - Texas Tech University, Biological Sciences, Mail Stop 313, Lubbock, Texas, 79409, USA
global climate change.
Presentation Type: Oral Paper:Papers for Sections
Date: Tuesday, August 1st, 2006
Time: 9:00 AM