Project Overview

Reports

Commodities

Target Pests

Practices

This project will develop a novel approach for combatting weeds in working and natural lands by harnessing fuel reduction practices and native plant restoration to control weeds and prevent reinvasion. Some of the worst weeds of wildlands in the Western US are invasive annual grasses, which have severely altered – or in some instances completely replaced – a number of native ecosystems. These grasses lead to larger and more frequent wildfires, which further promote their dominance, but controlled fires could also be part of an IPM-based solution. In many western ecosystems, woodlands exist within a matrix of invasive annual grasslands. In these woodlands, reducing fuel loads is a high management priority to mitigate the risk of high severity fires. One approach is to thin and gather woody debris and burn these in controlled fires. We propose that these pile burns can be taken advantage of to kill grasses and other weeds in the soil seedbank. Further, by replanting these burned areas with native species, we can increase invasion resistance and enhance ecosystem services. We will develop a protocol for integrating pile burns and replanting into IPM for invasive-dominated oak woodlands in California by:

1. Surveying stakeholders throughout California to evaluate current practices for fuel reduction in mixed grassland-woodland landscapes and identify best practices for adoption and implementation
2. Monitoring the impact of pile burns on weed cover and soil seed banks
3. Establishing restoration trials within burn scars to determine which species and planting approach is most effective for preventing reinvasion
4. Using the results of these activities to develop a protocol for integrating fuel reduction practices and replanting into IPM for weed-dominated ecosystems

By focusing on multiple management stages – weed control through prescribed burns and weed prevention through restoration – this approach could provide practitioners with a useful and efficient tool for meeting multiple land management goals, including reducing fire risk, enhancing biodiversity, and improving forage. This grant will allow us to establish a pilot study to evaluate the success of controlled, high-intensity fires and native replanting for mitigating the impacts of invasive annual grasses. While the proposed activities are for a single year, this will be a powerful study system for testing the longer-term outcomes of this approach.

1. Assess current practices for fuel reduction and weed control in oak savannas

In order to develop management recommendations that are likely to be adopted and successful, we will first survey stakeholders and land managers throughout the State to gain insight into current practices for reducing fuel loads and controlling invasive grasses. Through these survey results, we will be able to gain insight into methods that land managers currently employ and their management priorities. We can then use this information to better align our management recommendations with current practices and identify potential barriers to implementation.

2. Evaluate the efficacy of pile burns for controlling invasive grasses

We will implement a pilot study to rigorously evaluate the effects of pile burning on invasive annual grasslands, both aboveground (i.e., plant density, cover, and biomass) and belowground in the soil seedbank. We will take advantage of existing management operations at the Pepperwood Preserve, where hundreds of pile burns are conducted in invasive-dominated grasslands each winter using brush harvested from adjacent woodlands as part of fuel reduction initiatives. We will monitor nonnative and native vegetation within burn scars of different ages and sizes. This will allow us to evaluate the effectiveness of control of invasive grasses, as well as how long these control methods persist.

3. Determine how to prevent reinvasion through native plant restoration

While high-intensity fires will likely have a profound negative impact on invasive grass seedbanks, burn scars will inevitably face pressure from recolonizing weeds. Therefore, a key aim of this project is to determine how to best reestablish native plants in order to prevent reinvasion. We will test this experimentally by restoring burn scars with different mixes of native plant functional groups (e.g., native perennial bunchgrasses and forbs) and monitoring recolonization by invasive weeds. We will also evaluate the effectiveness of reseeding vs. transplanting plugs. We will also monitor restored burn scars already established at Pepperwood Preserve (but for which no data has been collected to date). This will allow us to develop the most efficient and cost-effective method for revegetation following weed control efforts.

4. Develop guidelines for integrating fuel reduction and replanting into IPM for invasive annual grasslands

We will use the results of our stakeholder surveys and field trials – along with continued engagement with our collaborators – to develop a protocol and accompanying guidelines for how to best integrate fuel reduction activities and post-fire restoration into adaptive land management strategies. These will be disseminated to stakeholders through multiple avenues, including a concise written report, a peer-reviewed publication, and presentations. The goal of these research products is to maximize the impact of our work and communicate our results to the practitioners that will benefit the most from this approach.