Grazing and Rare Plants

Saturday, October 22 at 8:00-9:40 am, Fir Room

Session Description: Compared to landscape- or animal-grazing interactions, there is relatively little specific work that has gone into the rare plant-grazing interaction. In conservation work, “grazing” is often used as a blanket term, obscuring the complexity of using grazing as a management tool to promote rare plant populations. Often the specific needs of rare plant species that “grazing” could address are unique to the species and require knowledge of both the ecology of the species and an understanding of current grazing practices. Issues of scale, location, infrastructure, and goals can further make grazing management difficult requiring alternative solutions. Current work specific to grazing and rare plants is active with examples of both successes and failures. Discussion of ongoing work and encouraging further research is important for understanding long-term rare plant management and conservation.

Session Chair: Todd Lemein, PhD (U.S. Fish and Wildlife Service, Ventura, CA, USA)

32.1    A perspective on grazing as a management tool for rare plants

Todd Lemein (U.S. Fish and Wildlife Service, Ventura, CA, USA)

Grazing has been identified as being both beneficial and detrimental to the management of rare plants. A review of the academic and professional literature shows that relatively little direct research has been done to describe when, where, and how grazing can be effectively used for the specific management of individual rare plant species. The term “grazing” is often used generically, and carries with it implications for management actions that many practitioners may not fully understand. Best practices currently described for forage production, wildlife habitat, or general best management practices may not be the best course of action when the primary goal is the promotion of populations of a single species of rare plant. Standard practices also may not translate well to populations on small parcels of land, in urban environments, or where grazing infrastructure does not already exist. Even where grazing infrastructure exists, and grazing has been a historical aspect of the landscape cooccurring with rare plant species, interactions between land owners, grazing lease holders, regulatory agencies, and land trusts may not understand how best to comanage the needs of a herd with the needs of a rare plant. In this talk I will discuss case studies that highlight the difficulty in using grazing as a management tool using Santa Cruz tarplant, Gaviota tarplant, Scotts Valley polygonum, Scotts Valley spineflower, and San Joaquin Valley spineflower as focal species.

32.2    Livestock grazing’s role in the conservation of threatened and endangered plants in California

Sheila Barry (University of California Cooperative Extension, San Jose, CA, USA)

Based on United States Fish and Wildlife Service listing documents, 87 plant species or 48% of all the federally listed threatened or endangered plant species in California are found in habitats with grazing. A review of these documents reveals a complex and varied relationship between grazing and conservation. While livestock grazing is a stated threat to 66% (57) of the species sharing habitat with livestock, 56% (49) of the species are said to be positively influenced, with considerable overlap between species both threatened and benefitting from grazing. While the primary grazing threat to listed plant species is from direct impact to an individual plant from grazing or trampling or overgrazing, grazing is credited with benefiting listed plants by improving or maintaining habitat. Federally listed grasses and forbs, both annuals and perennials, primarily benefit from grazing’s control of the state’s novel vegetation and reduction of thatch. Grazing management can combat anthropogenic threats that alter habitat, such as invasive species and nitrogen deposition, and support efforts to reduce land use change and landscape fragmentation, supporting conservation-reliant species in California. Grazing threats and benefits are noted for species across all of California’s non-alpine terrestrial habitats including some aquatic habitats, such as riparian areas, wetlands, and temporary pools.

32.3    Cattle grazing effects on the federally endangered Contra Costa Goldfield

Jaymee Marty (Marty Ecological Consulting, Sacramento, CA, USA)

Cattle grazing is considered an important management tool in California grasslands and vernal pools. Travis Air Force Base in Solano County, California has one of the last remaining populations of a federally endangered plant, Contra Costa Goldfields (Lasthenia conjugens). This short-statured annual flower occurs only in vernal pools and in an area on the base where grazing had not previously occurred. Management of the grasslands and vernal pools on the site consisted of mowing during the late spring. Annual data collected from the population since 1997 indicated that it was in steep decline at this site and poor management was implicated. Grazing was introduced to the site in 2018 and a study was established to monitor the population of goldfields as well as the overall vernal pool and grassland plant community. Mowing treatments were included within the ungrazed plots for comparison. After 4 years of grazing, grazed plots had significantly higher cover of goldfields than the ungrazed (and mowed) plots. The ungrazed plots had significantly higher levels of non-native grass cover and thatch than the grazed plots. The goldfields population was also significantly impacted by extreme climatic variation including extensive algal crusts formed during prolonged pool inundation and a lack of ponding due to lack of winter rains.

32.4    Management and conservation of Santa Cruz Tarplant

Felix Ratcliff (LDFord, Consultants in Rangeland Conservation Science, Berkeley, CA, USA), Kaveh Motamed (LDFord, Consultants in Rangeland Conservation Science, Belmont, CA, USA)

Santa Cruz Tarplant (SCT; Holocarpha macradenia) is a rare plant that occurs in only a handful of locations in Santa Cruz, Monterey and Contra Costa counties. Several SCT populations have become extirpated or have declined since being listed as Threatened by the U.S. Fish and Wildlife Service (USFWS) in 2000. Reintroduction has failed at many locations and annual monitoring at sites with known populations suggest declining numbers of individuals despite adaptive management efforts. A major impediment hindering the reintroduction and recovery of these populations is that little is known about ecological site and sub-site characteristics required for occurrence and persistence of the species. Similarly, relationships between management practices and temporally-variable habitat conditions (such as: Residual Dry Matter (RDM) and spring biomass) have not been sufficiently evaluated in relation to Santa Cruz Tarplant population responses and long-term viability. Each of these variables has been shown in various similar grassland situations to be correlated with persistence of other special-status species (such as the endangered Ohlone Tiger Beetle, also in Santa Cruz County). We are currently conducting a two-phase project to evaluate ecological and management factors affecting the persistence of Santa Cruz Tarplant populations. In the first phase we are looking at ecological variability and management history across the range of the species using a combination of site visits and interviews. In phase two (beginning in summer 2022) we will implement grazing and mowing management trials to evaluate specific habitat management thresholds for this species.

32.5    Grazing for biodiversity in the Central Coast of California

Rodrigo Sierra Corona (Santa Lucia Conservancy, CA, USA)

Grasslands depend on disturbance, like grazing and fire, to maintain its vegetation composition. Prior European colonization of California, indigenous people utilized fire to manage vegetation, shaping and maintaining prairies and other communities. Post contact, the systemic displacement of native human communities altered California’s landscape. Native wildlife population levels changed, and the introduction of invasive plant species and livestock resulted in modified vegetation compositions and ecological dynamics. This, compounded by cattle ranching practices, resulted in a myriad of ecological problems, which modified ecosystem resilience and reduced biodiversity, presenting unique challenges to manage grasslands. The Santa Lucia Preserve, located in Carmel, California, includes 5,000 acres of grasslands with high levels of native vegetation components. Prior to the removal of livestock in the 1990’s, the preserve was a cattle ranch for two centuries. After the first decade, vegetation recovery was observed across ecosystems, followed by a decline of grassland diversity, noted in 2010. Managers hypothesized this was because of high levels of thatch covering the ground, preventing plant establishment, with invasive grass and forbs taking over the landscape. In 2013, a grazing program was established, with the objective of thatch removal, nutrient deposition, and vegetation growth stimulation. Since then, floristic data has been collected from paired grazed-ungrazed exclosures to explore the effects of grazing. Early analyses have shown promising trends, where 1) thatch levels and fuels have been significantly reduced, 2) native grass species have remained stable or slightly increased, 3) native forbs have increased in cover, and 4) noxious weeds are either stable or declining. In addition to presenting our early results, we will discuss lessons learned and give detailed insight on the management of our Conservation Grazing Program.