Because of the scale and significance of the conservation and restoration projects begun in 1999 by Audubon California in the Willow Slough Watershed, the project sites on local farms and ranches offer a number of opportunities for important ecological research. The following is a brief description of various research project currently being conducted on ranches in the Willow Slough Watershed.

Monitoring the environmental determinants of restoration success
Dr. Truman Young and PhD Candidate Megan Lulow, of University of California Davis Graduate Group of Ecology

Restoration of native grass and forb species offers the potential to increase the diversity and stability of plant communities in California rangelands. Although much has been learned over the last ten years about aspects important to the establishment of native grass species, much of the evidence for this success has gone undocumented. In addition, there is much more to learn about how the success of native grass establishment varies with environmental variables both as a whole and among different species. Even less is known about the potential for using native forbs to increase grassland biodiversity. Further research is needed regarding what management techniques are important to their establishment and how variable the nature of coexistence among these native grassland groups is among soil types and background weeds.

This project includes two separate studies: one on assessing the correlates of successful upland native perennial grass establishment, and a second on the feasibility of using native forbs in grassland restoration to increase biodiversity. Results from these studies will help in understanding how native grassland species used in restoration projects vary in their response to specific environmental variables. This may aid future projects in developing restoration techniques (e.g. seed mixes) for varied terrain and in determining the amount of resources to invest in management efforts. In addition, the studies will provide information on the feasibility of using particular native forb species in restoration of grasslands in this region, focusing both on their response to specific management tools and on their interactions with the perennial grasses being restored in the community.

Avian monitoring and assessment of perennial grassland and riparian restoration efforts in the Willow Slough Watershed
Dr. Dan Anderson and PhD Candidate Jan Goerrissen, University of California Davis Fisheries and Wildlife Biology

Degradation and alteration of native perennial grasslands and riparian areas have resulted in population declines of many bird species. Shifts in vegetative structure and species composition are thought to contribute to declines of habitat specialist species. Habitat restoration, through the establishment of native vegetation and control of exotic species, may provide valuable habitat and aid in conservation efforts of specialist species. Vegetative characteristics needed to support specialist species needs to be more fully understood. Monitoring bird abundance and species composition within recently restored and comparison sites over time will provide and avenue for evaluating the ability of current restoration techniques to provide suitable habitat for specialist species. This study will determine which characteristics of native vegetation are most influential in supporting habitat specialist bird species.

The proposed study will monitor the abundance and composition of the bird community during the establishment phase of the restorations. By comparing bird abundance and composition with quantitative vegetation measurements we hope to identify those components (e.g. vegetation height, species composition, percent cover, phenology) of the vegetation that have the greatest influence on the bird community. Incorporation of bird perches and brush piles into the restoration process will enable us to evaluate the efficacy of incorporation such structures to enhance wildlife habitat.

Using remote sensing to monitor vegetation response to land management activities
Dr. Carolyn Malmstrom, Michigan State University, Department of Botany and Plant Pathology

Successful long-term and large scale conservation and restoration efforts in the Willow Slough Watershed rangelands will require that spatial and temporal information about habitat and forage quality as well as species distributions be available at a watershed scale. Such watershed-scale analyses may be most effective when based on advanced remote sensing and spatial technologies. In this project, Michigan States Basic Science Remote Sensing Initiative will test and apply a new approach for quantifying dry biomass, which has been developed and used successfully in NASA-funded rangeland management project in Arizona. Remote sensing has also been used to develop vegetation maps for large areas. This project seeks to map four important vegetation types within the grasslands: annuals with good forage value (Avena sp. mix); native perennial grasses; medusahead, a significant rangeland weed; and yellow star thistle, another invasive. A good deal of the efforts in mapping vegetation types have relied on determining the spectral signature of plant types, often using hard-to-get hyperspectral data. In this project, we will develop and test a new phenological-based approach that we believe will be more effective in discerning vegetation types in this system, and may be less costly.

In addition to producing spatially explicit watershed data and analyses, this project will also make the data available to watershed stakeholders by means of a new web-based tool that has been prototyped in the Arizona project and has been used by individual ranchers there to help inform their land management decisions.

Field-based research on plant and soil response to restored native perennial grasslands versus non-native annual grasslands
Dr. Steve Griffith and Dr. Jeffrey Steiner, Agricultural Research Service, USDA, Corvallis, OR

California rangelands in the Central Valley and surrounding foothills have undergone a dramatic transformation in plant species composition over the past 100 years. Once dominated by deep-rooted perennial bunchgrasses such as Nassella species, they are now dominated by introduced Mediterranean annual species such as Avena, Bromus, and Hordeum species as well as more recent noxious invaders such as medusahead and goatgrass.

Changes at this ecological scale are apparent not only in plant species composition, but are also likely to change other less obvious, but important, ecological processes, such as nutrient acquisition by plants and soil microbes, nutrient retention by plants (storage), and soil water retention factors. For example, we know generally that nonnative annual species are lower in biomass and ground cover than perennials, increasing the potential for runoff, erosion, and weed invasion while also reducing soil water and nutrient retention. We know also that different species, and different species groups, such as annuals and perennials differ in acquisition of available resources such as N and C. Competitive advantages between species or groups of species may, consequently, dictate grassland plant species composition. Finally, research in the tallgrass prairies of the mid-west has shown that the bulk of C and N is stored below-ground in roots and rhizomes of perennial species, which contributes to new plant growth during times when nutrient availability is lower for annual plants.

How the species composition of grasslands affects abiotic and biotic plant and soil properties, however, is not well understood in California rangelands. Understanding this relationship now is critical, as interest in conserving and stabilizing soil and improving soil health in rangelands, along with a desire to preserve native ecosystems, have fueled a number of efforts to restore native perennial grasslands.

The researchers hypothesize that rangeland restoration, using deep-rooted native perennial grasses in California rangeland will improve rangeland quality over annual grassland systems by: 1) improving biotic plant and soil factors such as, nutrient acquisition by plants and nutrient processing in soils; and 2) improving abiotic soil factors, such as soil water percolation and retention, and soil compaction, and 3) altering the competitive relationship between species in part by changing the composition of the weed seed bank over time.

Research findings will provide a greater knowledge of both annual and perennial systems in California with respect to their plant and soil ecologies. Research findings will assist conservationists and landowners in making science-based management decisions that will improve overall ecosystem health. The specific objectives of this project are to: 1. Determine how restored native perennial grasslands compared to annual grasslands effect plant and soil factors, including, nutrient acquisition by plants and nutrient processing in soils; 2. Determine how restored native perennial grasslands compared to annual grasslands effect soil factors, such as soil water percolation and retention, and soil compaction.