Carla D'Antonio

Schuyler Endowed Professor of Environmental Studies and Ecology, Evolution, and Marine Biology	Office:	Bren Hall 4017
	Phone:	(805) 893-2796
	Fax:	(805) 893-4724
	E-mail:	dantonio@lifesci.ucsb.edu
	Website:	www.lifesci.ucsb.edu/eemb/faculty/dantonio/index.html
	Mailing Address:	Environmental Studies Program University of California, Santa Barbara Santa Barbara, CA 93106-4160
	Courses:	ES/EEMB 119, Resource Ecology and Management of CA Wildland Ecosystems ES/EEMB 128, Ecological Constraints to Ecosystem Restoration ES/EEMB 133, Biodiversity and Conservation Biology

My research focus has been to understand processes that control invasions by non-indigenous species into ecological communities and how and when the addition of some individual species affects ecosystem structure and functioning. I seek a mechanistic understanding of ecological patterns and process and although I work primarily at the community and ecosystem levels, I also examine individual plant and population processes. I believe that such an integrated approach is the best way to answer questions about the importance of individual species and how communities and ecosystems will change with increasing human population pressure, increasing movement of plant species, nitrogen deposition and climatic fluctuations.

Research in my laboratory that has focused on understanding both controls over vegetation change including species invasions, and the impact of individual species on 'native' ecosystems. While the studies of species invasions has important conservation implications, I believe strongly that non-native invasive species offer an important opportunity to probe both factors structuring plant communities and sources of variation in species effects on ecosystem processes. I have not, however, limited my research to introduced species as will be described below.

1. Plant Community Ecology
Processes influencing rates and patterns of biological invasion: Since its inception early this past century, a major theme of plant ecology has been to try to elucidate factors influencing plant community structure and the direction and magnitude of community change through time. The successful management of intact native plant assemblages depends on understanding community attributes as well as how native and introduced plants will respond to anthropogenically-driven environmental change. The prevalence of non-native species in most landscapes today introduces an element of unpredictability to studies of ecological succession yet at the same time they offer an opportunity to investigate factors structuring plant populations and assemblages. I have therefore used non-native species to conduct detailed mechanistic studies into the relative importance of different structuring forces in plant assemblages and to look at how species interactions control and will be influenced by invading species. I believe that such studies will ultimately assist with predicting, managing and restoring native biological diversity when that is the desired goal.

Research in my lab has focused on clarifying the importance of biotic interactions, propagule supply and the physical environment in determining the success of plant invasions and on putting invasion biology into mainstream ecology by discussing community resistance and 'invasibility' as part of general ecological theory. I and my students use both experimental field and greenhouse studies and observational approaches to understand mechanisms responsible for resistance to invasion and variability in resistance among communities.

Understanding causes of shrub invasion and vegetation change in montane meadow ecosystems: Over the past century many regions of semi-arid rangeland in the western USA have undergone a change from domination by native perennial grasses and forbs to invasion by and dominance of woody species. While the processes controlling encroachment of woody species likely differ in each setting, there is widespread belief that shrub invasion is symptomatic of and contributes to habitat aridification. With collaborator Dr. Eric Berlow of the White Mountain Research Station, we have been investigating controls over shrub invasion into montane meadows in the presence and following the cessation of livestock grazing in the eastern Sierra Nevada of California. Livestock grazing and subsequent stream incision earlier in the past century has resulted in the conversion of large expanses of herb meadow to sagebrush terraces. Nonetheless, shrub invasion continues in areas today that are no longer grazed and that are reasonably wet. Our work aims to understand both factors controlling shrub expansion and factors influencing the recovery of herbaceous species after the cessation of livestock grazing and after the removal of invading woody species.

Impacts of livestock grazing and fire on species composition of California grasslands. California grasslands are notorious for their persistent domination by European annual grasses and forbs. Not only has the lively debate over the pre-contact composition of these grasslands and influence of livestock grazing on compositional change not been resolved, but there also has been little resolution about the current influence of livestock grazing on grassland composition. In addition, the usefulness of fire as a tool to manipulate current composition is unclear. In collaboration with Claudia Tyler at UCSB, I am planning to examine the potential importance of soil factors (e.g. texture, depth, infiltration rates, C,N,P) in controlling the vegetation response to release from grazing across 26 paired exclosure/control sites at the Sedgewick Reserve. Our goal is to evaluate the sources of variability in response to release from grazing using sites that have had the same recent history of grazing/release, and experience similar climate but differ in soil properties. We then hope to explore possible approaches to restoring sites where invasive undesirable species have remained abundant, to more desirable, diverse plant assemblages.

2. Species effects on ecosystem structure and function
An exciting development in ecosystem ecology over the past decade is the rise in interest in the impacts of individual species or groups of similar species on ecosystem processes such as rates or patterns of nutrient accumulation and flux, energy flow, and soil and hydrological processes. My interest in this area is centered around trying to understand the conditions within which a species or group of similar species will have measureable impacts versus when climate, soils or other factors will be override the effects of individual species. I first became interested in this while a graduate student at UC Santa Barbara when I found that the introduced succulent Carpobrotus edulis, has significantly greater effects on soil chemistry in some sites than in others and that the strength of the effect was correlated with soil texture. Since then, my research in this area has focused on the effects of non-native invasive species on disturbance regime and nutrient cycling.

Exotic grasses & the grass fire cycle. Between 1991 and 2000, I worked extensively on the impact of exotic grass species on disturbance regimes. This work has focused largely on alteration of fire frequency as an important ecosystem level change occurring in semi-arid habitats as a result of the widespread movement of invasive exotic grasses. By changing the distribution and abundance of fine fuels through space and time, introduced grasses have increased the occurrence of fire in ecosystems with little prior history of fire, causing large scale loss of native species and profound alteration of ecosystem functioning. With resource management specialists at Hawaii Volcanoes National Park, I have investigated variation in the outcome of grass-fueled fires across an elevation gradient. I am interested in how environmental conditions influence fuel biomass and distribution and how this in turn affects the outcome of grass-fueled fires. Currently, with post-doc Karen Haubensak, I am investigating causes of variation in the outcome of grass-fueled fires in central Nevada where invasive European annual species have invaded sagebrush rangelands.

Species effects on nutrient cycling: The prevalence of invasive exotic plant species on the landscape has provided a tool for examining how species effects on nitrogen cycling develop. With former graduate student Michelle Mack and undergraduate students, we produced a major body of work on the effect of introduced grasses on nitrogen cycling in Hawaiian woodlands. We found that contrary to our expectations, introduced grasses had little to no effect on nitrogen cycling in otherwise undisturbed Hawaiian woodlands despite their very high abundance. This was because they did not replace native species but rather interacted with them in a competitive and compensatory manner. By contrast, after fire these woodlands become dominated almost exclusively by exotic grasses, nitrogen cycling is speeded up and overall ecosystem N retention greatly decreases. The increased leakiness of this system after fire is due to the loss of native species caused by fire after grass invasion rather than direct inputs from the grasses.

The extent to which large-scale ecosystem changes are caused by the loss of natives rather than by new traits introduced by the invaders is something I hope to investigate in invaded rangelands in southern California. Ultimately I would like to work with a modeler to explore questions relating to the conditions under which repeated fire will result in substantial declines in soil organic matter, mineralization potential and productivity and the extent to which these changes might be reversible with active restoration of native species.

With collaborator Jeff Corbin (UC Berkeley) we are investigating the effect of grass origin and life form on ecosystem N retention and cycling in a California coastal prairie. We have found that introduced annual grasses that have displaced native perennial species in California grassland, cause increased nitrate leaching from ecosystems and decrease nitrogen retention. In addition to comparing annual exotic to native perennial grasses, we are comparing both of these groups to a new group of invaders in coastal prairie, cold season perennial grasses from Europe. Using planted plots of known composition, we are comparing N retention and cycling among these three groups of species. We use a combination of field and lab soil and plant measurements and experimental additions of 15N labeled ammonium to evaluate species effects on N cycling in this system.

Species effects on water storage. Water is a critical, limited resource in the semi-arid western USA. Changes in plant composition can affect the amount of water moving into groundwater or stored in the soil. In collaboration with PI Tom Dudley and post-doc Robert Pattison, we are exploring the impact of partial control of the invasive tree, Tamarix ramosissima on soil water and evapotranspiration. This riparian tree is reputed to transpire enormous amounts of ground water because its high leaf area and ability to continue photosynthetic activity under extremely harsh conditions. We are investigating how the introduced biocontrol agent, Diorhabda elongata, which feeds exclusively on this tree but does not kill it, affects evapotranspiration by Tamarix. We are also comparing water loss by replacement vegetation with water lost by the intact Tamarix canopy.

Education:
Post-doctoral associate, Stanford University, 1990-1991.
PhD in Biological Sciences, University of California, Santa Barbara. 1990.
M.S. in Zoology, Oregon State University, Corvallis. 1982
B.A. in Zoology, University of Washington, Seattle. 9/76-6/78.
Mount Holyoke College, South Hadley. 9/74-6/76.

Selected Publications:
D'Antonio, C.M., T. Dudley and M. Mack. 1999. Disturbance and biological invasions. In, L Walker (ed), Ecosystems of disturbed ground, Elsevier, pp. 429-468.

Ewel, J., D. O'Dowd, J. Bergelson, C. Daehler, C.M. D'Antonio (+16 others). 1999. Deliberate introductions of species: Research needs. Bioscience 49: 619-630.

Levine, J. and C.M. D'Antonio. 1999. Elton revisited: a review of evidence linking diversity and invasability. Oikos 87: 15-26.

Weber, E. and C. D'Antonio. 1999. Effects of salinity on germination and growth of hybridizing Carpobrotus spp. in California. Am. J. Botany 86: 86:1257-1263.

Weber, E. and C.M. D'Antonio. 1999. Phenotypic plasticity in hybridizing Carpobrotus species in coastal California. Can. J. Bot. 77: 1411-1418.

Richardson, D.M., N. Allsopp, C.M. D'Antonio, S. Milton and M. Rejmanek. 2000. Plant invasions-the role of mutualisms. Biological Reviews, 75:65-93.

D'Antonio, C.M, J.T. Tunison and R. Loh. 2000. Variation in impact of exotic grass fueled fires on species composition across an elevation gradient in Hawai'i. Austral Ecol. 25:507-522.

D'Antonio, C.M. 2000. Fire, plant invasions and global changes. In, H. Mooney and R. Hobbs (eds). Invasive species in a changing world, pp. 65-94. Island Press, Covela.

Albert, M. and C.M. D'Antonio. 2000. Conicosium pugioniformis. In Bossard, C., Randall J. and M. Hoschovsky (eds). Invasive weeds in California wildlands. Univ. of CA. Press, Berkeley.

Vila, M, Weber, E. and C.M. D'Antonio. 2000. Conservation implications of invasion by plant hybridization. Biol. Inv. 2:207-217.

D'Antonio, C.M., R.F. Hughes and P.M. Vitousek. 2001. Factors influencing dynamics of invasive C4 grasses in a Hawaiian woodland: role of resource competition and priority effects. Ecology 82:89-104.

Tilman, D., J. Fargione, B. Wolff, C. D'Antonio and 6 others. 2001. Forecasting agriculturally driven global environmental change. Science 292:281-284.

Mack, M., C.M. D'Antonio and R. Ley. 2001. Pathways through which exotic grasses alter N cycling in a seasonally dry Hawaiian woodland. Ecological Applications 11:1323-1335.

D'Antonio, C.M., L. Meyerson and J. Denslow. 2001. Research Priorities related to invasive exotic species. In, M. Soule, G. Orians and D. Boersma (eds). Conservation Biology: Research priorities for the coming decade, Island Press, Covelo, CA pp. 59-80.

D'Antonio, C.M., J. Levine and M. Thomsen. 2001. Propagule supply and resistance to invasion: A California botanical perspective. J. Medit. Ecol., 2:233-245.