Local Biodiversity and Invasive Species
The Stanford Conservation program is committed to the protection of species of conservation concern, especially federally and state listed species and to the broader maintenance of native ecosystems. Our community-level approach to environmental stewardship acknowledges the value of species interactions for the conservation of single species and for the maintenance of ecosystems services such as clean water and carbon storage. Species diversity on Stanford lands is relatively high and includes 150 species of birds, over 45 species of mammals, 19 species of reptiles, 11 species of amphibians, 8 species of fish, and countless species of invertebrates (a full list of animal species found on Stanford lands can be found here).
The grasslands, woodlands, wetlands, and suburban areas of Stanford are home to more than 670 species of native plants and over 325 species of non-native plants (a full list of plant species can be found here). Native plants provide a number of benefits to people and ecosystems.
- Native seeds sourced from local counties are well adapted to local soils and historic climate and therefore tend to have higher establishment success.
- Native perennial grasses, in contrast to the annual Eurasian grasses that dominate a large proportion of California grasslands, store many times more carbon in their root biomass than annual grassland plant species.
- Native plants are used by indigenous people and define some of California’s most iconic landscapes.
- Native plants often provide the physical structures and food resources that other native species require for survival. California tiger salamanders and California red-legged frogs, two species of conservation concern on Stanford lands, are adapted to native grasslands and the ecosystem functions they provide.
Highly invasive, non-native species impact native biodiversity and ecosystem function. In addition to nonnative plants, over 30 nonnative vertebrate and invertebrate species have been found and some pose severe risks. Among the most problematic are the centrarchids (sunfish and largemouth bass), bullfrog, starling, Louisiana red crayfish, and red fox. To reduce invasive species’ ability to outcompete native species and damage local ecosystems, the Conservation Program staff and volunteers complete targeted control efforts on Stanford lands. If you’d like to help protect threatened species, reduce fire risk, and improve native biodiversity, join us for our regularly hosted volunteer days!
We use adaptive management to evaluate land management alternatives and refine our interventions to maximize effectiveness and efficiency. In the most rigorous form of adaptive management, we impose an experiment over the lands we manage. Since 2016, we have implemented a grassland restoration experiment to evaluate the effectiveness of mowing and broadcast seeding of native seed.
Since 2016, the Conservation Program has been conducting a grassland restoration experiment to 1) evaluate whether broadcast seeding of native species combined with timed mowing (designed to target flowering in weedy plant species) is an effective means of achieving restoration targets and 2) determine how much time and money would be required to achieve restoration targets. We monitor changes in overall native percent cover and species specific responses to experimental treatments. Because the experiment was independently initiated 3 years in a row and replicated across different aspects, we are also able to better understand treatment effects differ among aspects and initial year of treatment application.
2020 results showed no interaction between treatment and aspect. Mowing and seeding increased the percent cover of native species but only by roughly 5% relative to controls.
East-facing and flat slopes had the highest percent of seeded natives.
After the first and second year of treatment application the percent cover of seeded species was found to differ by year of initial seeding. Significantly, those rankings change over time. After the first year, plots seeded in 2018 had the highest percent cover of seeded species, but after two years of treatment application, the plots initially seeded in 2017 had the same percent cover of seeded species but both had higher percent coverage than the plots initially seeded in 2016.
One of the more surprising results of the study was that species richness, particularly of native species that were not seeded, was higher in restoration treatments. So either mowing alone or facilitation by seeded natives increases establishment or growth by non-target native plants and promotes native plant diversity overall.
Given the increases in plant biodiversity and native coverage seen with restoration treatments, we plan to mow and seed in target areas using adjusted species palates. We also plan to continue to apply treatments for additional years to evaluate the potential for increases in percent coverage of native plant species.