Identifying effective restoration approaches to maximize plant establishment in California grasslands through ameta‐analysis

Abstract

One reason restoration often fails is a lack of native plant establishment. Establishment failure can occur due to a lack of dispersal into the site, inappropriate abiotic conditions for plant survival, or biotic interactions that reduce germination rates or seedling survival. Understanding what is limiting establishment is critical for restoration success. Unfortunately, there has been little synthetic work to identify which restoration practices (e.g., direct seeding, weeding, irrigation) are most likely to improve plant establishment. Here we used a meta-analytical approach to determine what practices are most likely to enhance establishment success in grassland communities in California. We explored the impact of these practices on whole communities as well as on different functional groups (grass and forb). We categorized techniques by the constraint they addressed (dispersal, abiotic, or biotic) to determine which restoration practices are more likely to improve plant establishment. We found that addressing the dispersal filter is the best way to improve plant establishment regardless of the functional group. This suggests that most native plants targeted in restoration are seed limited. While we were able to identify restoration techniques that improve plant establishment, our synthesis revealed that there were insufficient numbers of studies and a lack of uniformity between treatments that hampered efforts to make broad conclusions. If we can expand research to more ecosystems, and use standardized treatments within each ecosystem, the restoration community could synthesize research more efficiently, which would inform our ultimate goal of increasing the success of restoration.

Fear changes traits and increases survival: a meta‐analysis evaluating the efficacy of antipredator training in captive‐rearing programs

“…We conducted the meta‐analysis using standard approaches (Harrison 2011; Tetzlaff et al 2019; Nolan et al 2021) to ensure appropriate studies were identified and analyzed. We focused on published studies involving organisms born or reared in captivity, or naive prey, to eliminate impacts of predator‐exposure history (Martin 2014).…”

“…Given the variety of measures used in the collected studies, we calculated effect size using Hedges' g (Tetzlaff et al 2019; Nolan et al 2021). Hedges' g is defined as the difference in mean outcomes between two independent groups divided by the pooled and weighted standard deviation (Enzmann 2015).…”

Tertiary succession: a new concept to help vegetation restoration

“…In restorations, native species are routinely added, though often not in sufficiently great diversity to mimic natural systems (Hughes et al 2018). Restoration deliberately reduces dispersal constraints (Nolan et al 2021), while K‐selected species (with poor dispersal due to a tradeoff to a seed size favoring establishment in competitive conditions) normally dominate in secondary succession (Opler et al 1980). A large seedbank is similarly present in secondary succession and restoration, though in restorations, it is probably comprised of alien or inappropriate species (Bekker et al 1997), severely limiting succession.…”

Prescribed burning may produce refugia for invasive forb, Oncosiphon pilulifer

“…In heavily invaded areas, native seedbanks are often depleted (Cox & Allen 2008; Gioria & Pyšek 2015). Consequently, native seed addition and planting native seedlings are an essential management action for increasing native establishment (Nolan et al 2021). However, broadscale seed addition often does not translate to high native establishment, high postemergence seedling mortality results from environmental conditions and competitive pressures from invasive species (Shackelford et al 2021).…”