Persistent asymmetrical priority effects in a California grassland restoration experiment

Self Cite

113

Restoration success is often hampered by the failure of less dominant competitors to establish. An emerging literature on priority effects suggests the manipulation of community assembly as a useful technique to help overcome these difficulties by altering competitive relationships. We present data from a set of four priority experiments, carried out at each of three sites in restoration settings in California grasslands. These data, combined with patterns summarized from the literature, indicate that both short‐term priority (1–3 weeks) and long‐term priority (1 year) can profoundly shift interspecific relationships and benefit otherwise subordinate plant species, but that these effects are sometimes transitory, asymmetric, and contingent on environmental conditions and species composition. Restoration interventions that can produce priority effects include staggered planting times, weed control, seed pre‐germination, plug planting, and spatial aggregation. Such interventions are likely to be at least initially effective, but their strength and persistence can differ considerably across systems in space and time. Further research may help identify the conditions that maximize the strength and persistence of priority effects in restoration settings.

Section: Methodsmentioning

confidence: 66%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Using priority effects to manipulate competitive relationships in restoration

Young

Stuble

Balachowski

et al. 2016

Self Cite

113

“…Future work will build on these first‐year findings to see whether planting year differences persist over years to influence community assembly. Lasting year effects will likely vary by species (Werner et al ), and in some cases, first‐year communities may leave their mark on communities assembling into the future due to processes of historically contingent assembly (Lockwood & Samuels ; Fukami ). In the end, it will be important to examine how year effects matter alongside other major causes of variation in restored communities, e.g.…”

Section: Discussionmentioning

confidence: 99%

Interannual variation in precipitation and other planting conditions impacts seedling establishment in sown plant communities

Groves

Brudvig

2018

Ecological restoration can reverse biodiversity loss worldwide, yet restoration goals and outcomes vary widely, which limits this potential. Divergent restoration outcomes may stem from variation in conditions at the outset of restoration, but empirical evidence is lacking and typically confounded with site differences. Additionally, precipitation is usually cited as the source of this variation, although a wide range of conditions can vary annually. We tested for effects of planting year on seedling establishment by installing identical restorations in three different years. Within those years, we manipulated rainfall with rain‐out shelters to disentangle the effects of precipitation from other annually variable conditions. Additionally, we tested whether increasing seed mix richness buffers against adverse planting conditions. For the first growing season after planting, we followed emergence and survival of sown prairie species and nonsown weed species to determine how planting year conditions influence an establishing plant community, if at all. We found that seedling establishment differed across planting years and precipitation treatments, and that varying emergence patterns by species led to differences in the composition of the first‐year community. We also found significant variation in sown species establishment across years when precipitation was held constant, illustrating the previously overlooked role of nonprecipitation drivers on planting year effects. Higher seed mix richness did not consistently improve establishment of sown species under different planting conditions. This research provides important experimental evidence for effects of interannual variation in planting conditions on first‐year establishment. Future work will examine how these initial changes affect longer‐term assembly dynamics.

“…It may also be possible to foster diversity and resist invasion through the creation of within‐island temporal or spatial priority effects. Specifically, less competitive species can be planted earlier than, or spatially segregated from, more competitive species (Porensky et al ; Vaughn & Young ; Werner et al ), allowing the coexistence of ruderal and more slow‐growing native species. When plantings are temporally segregated, initial fast‐growing species could be a “first step” in a multitiered restoration process, reducing the competition from non‐native species, stabilizing soils, and perhaps ameliorating site conditions for future target species (Leger et al ; Uselman et al ). Structure islands for maximum longevity: Avoid very small islands, isolated islands, and islands with high edge‐to‐area ratios .…”

Section: Recommendations For Creating Successful Restoration Islands mentioning

confidence: 99%

Restoration islands: a tool for efficiently restoring dryland ecosystems?

Hulvey

Leger

Porensky

et al. 2017

Restoration islands are concentrated plantings in strategic locations, created to efficiently use resources to achieve restoration goals. These methods have been used effectively in mesic ecosystems, particularly tropical forests, where the goal of island plantings is often to “nucleate” across a degraded area, providing a seed source for spread outside the planted area. Here, we consider how an island strategy might be used to achieve restoration goals in dryland ecosystems, where limited resources and large areas of degraded land make restoration extremely challenging. In contrast to more productive areas, spread or “nucleation” from restoration islands in drylands may not occur or occur more slowly than required by most management time frames. Despite this, small‐scale, more intensive island plantings may still be useful for achieving short‐term goals, such as weed control, fire management, erosion control, and creation of wildlife habitat. Over the long term, island plantings could serve the same nucleation function as in other ecosystems and serve as repositories for genetic diversity within highly fragmented native systems. Here, we highlight the opportunities for using these high‐intensity, targeted planting methods in dryland ecosystems, provide the guidelines for establishing islands to achieve short‐ and long‐term restoration goals, and identify the areas where additional research is needed to understand the value of restoration islands in dryland ecosystems.