¿Û¿Û´«Ã½

GYPWORLD—a global consortium of researchers studying plants growing on gypsum soil

USDA-ARS Aquatic Weeds Research Unit

UNIVERSITY OF CALIFORNIAÌý Sierra Foothills Research and Extension Center David M. and Sylvia McLaughlin Reserve Ìý

TheÌý4Ìýmain areas of my research program:

1.Ìý Morphological and physiological traits associated with plant invasiveness. Exotic plant invasions pose a serious global ecological and conservation threat to native plant communities and can induce serious economic costs. Given their potential negative impacts, it is of interest to ecologists and invasion biologists to understand which traits makes some species more invasive than others. We know that some non-native species, following their arrival to a new area, simply naturalize and become part of the resident plant community. In contrast, other species experience rapid range expansion and are considered invasive. Determining which traits contribute most strongly to non-native organisms’ competitive ability is an essential first step in improving prediction and management of invasive species spread. Previous research has focused on species diversity or functional group diversity as a mechanism of invasion resistance. However, coarse functional or taxonomic groupings may not capture traits enabling invasive plants to outperform native ones. Our research focuses on key morphological and physiological functional traits involved in resource acquisition and use, particularly in resource poor environments.

2.Ìý Environmental and evolutionary constraints on plant nutrient resorption.Ìý I seek to understand the physiological, environmental, and evolutionary controls on internal plant nutrient recycling.Ìý Nutrient resorption and storage in perennial species conserves plant nutrient pools, decreasing plant reliance on current external nutrient supply and buffering the impact of annual variation in nutrient availability.Ìý At the whole-plant level, more complete nutrient resorption can increase plant fitness, a major driver of population dynamics.Ìý In contrast, complete resorption can negatively impact ecosystem processes.Ìý Since more complete resorption leads to nutrient-poor litter, decomposition processes are slowed, influencing site fertility and ultimately plant community composition.Ìý Despite the major role that nutrient resorption and storage may play in population, community, and ecosystem processes, there are significant gaps in our knowledge, such as:Ìý What is the relative importance of phylogeny versus environment on nutrient resorption?Ìý How do environmental factors influence realized resorption?Ìý Do other nutrient conservation or allocation mechanisms compensate in years of poor resorption?Ìý Using multi-year field sampling, manipulative experiments, and meta-analysis of published works, my ultimate goal is to gain a better understanding of how environmental variation, storage, and recycling drives community and ecosystem processes.Ìý By understanding plant physiological responses to these changes, we can predict feedbacks on community dynamics and ecosystem processes.Ìý

3.Ìý Plant adaptation to unique soil types.Ìý Unique soils, such as serpentine or gypsum, are hotspots of biological diversity.Ìý As such, they are excellent locations for asking questions related to adaptation and acclimation, as well as being areas of conservation concern.Ìý In addition to projects related to nutrient resorption and storage at the UC McLaughlin Reserve, I am investigating questions related to seed and seedling ecology of serpentine and non-serpentine shrubs, as well as plant-soil relations on gypsum outcrops in the Chihuahuan Desert.Ìý This work seeds to understand the physiological mechanisms promoting adaptation to these unique soils and how they relate to species evolution in these habitats.Ìý

4.Ìý Ecology of aridland communities.Ìý A common theme among my research program is studying aridland communities.Ìý Some of this work has focused on targeting species for restoration following invasive species management, particularly perennial bunchgrass systems.Ìý Other foci include the ecology of soil microbial crust communities and ecophysiological comparisons of common shrub and forb species.