Burning reveals cryptic plant diversity and promotes coexistence in a California prairie restoration experiment

Abstract

Abstract. Grassland and prairie restoration projects in California often result in long-term establishment of only a few native plant species, even when they begin with a diverse seed palette. One explanation for the disappearance of certain native species over time is that they are excluded through competition. If so, management that reduces interspecific competition may favor ''subordinate'' natives and promote greater native species diversity in restored communities. Potential management approaches to accomplish this goal include intraspecific spatial aggregation during seeding and prescribed fire. However, no studies have experimentally evaluated the effects of fire on a controlled (restoration) species pool or the interaction between fire and spatial aggregation. In a previous California prairie restoration experiment, we demonstrated that aggregated plantings protected competitively subordinate species from exclusion and increased community diversity for three years. However, native species richness declined throughout the study, and the benefits of aggregated seeding had begun to disappear by the third year. For the present study, we resurveyed the experimental plots five years after seeding and in the following year carried out controlled burns on half of the plots. The four subordinate species and one of the previously dominant species continued to decline and essentially disappeared aboveground during years four and five. However, burning in year five decreased the cover of dominant natives, triggered the reappearance of the three subordinate species that had disappeared or nearly disappeared in previous years, and increased diversity of the restored community. Seeding treatments (aggregated or interspersed) did not significantly affect community-level responses to the burning treatment. These results confirm that although initial intraspecific aggregation may promote species coexistence in the short term, re-establishing disturbance regimes can allow coexistence over a longer time scale by revealing and potentially renewing seed bank diversity.

Using priority effects to manipulate competitive relationships in restoration

“…In this same system, priority effects were weaker when no rainfall occurred in the interval between sowing of early‐ and late‐arriving guilds (Vaughn & Young ). These results, and a watering experiment done in this system (Young et al ), suggest that, in our study, water availability limited the ability of guilds sown early to preemptively utilize niche space and establish priority.…”

“…In contrast, two of the four publications in Table S2 that monitored priority experiments for more than one season suggested that the priority effects were short-lived. One long-term study of spatial aggregation as a priority technique also showed only temporary benefits (Porensky et al 2012;Young et al 2015aYoung et al , 2015b. It is noteworthy, however, that one of the multi-year studies actually showed an increase in priority effect through time (Vaughn & Young 2015).…”

Persistent asymmetrical priority effects in a California grassland restoration experiment

“…, Young et al. ). Practitioners should also be mindful that the advantages of priority may result in lower cover of late‐arriving dominant species (e.g., S. pulchra , L. formosus ).…”

“…Additional management strategies may be required to increase presence and abundance of these more subordinate species: e.g., grazing, mowing, prescribed fire, summer irrigation, and interspecific aggregation (Hayes and Holl 2003, Wainwright et al 2012, Funk et al 2015, Young et al 2015a. Practitioners should also be mindful that the advantages of priority may result in lower cover of late-arriving dominant species (e.g., S. pulchra, L. formosus).…”

Disturbance differentially affects alpha and beta diversity of ants in tallgrass prairies

“…Disturbance can influence these processes to ultimately affect a and b diversities by affecting environmental heterogeneity both within and among sites (Clough et al 2007). For example, disturbances such as fire and grazing can create patchiness in environmental conditions within sites which can have positive effects on a diversity by creating refuges and suppressing the dominant species (Sousa 1984, van Klink et al 2015, Young et al 2015. The positive effect of environmental heterogeneity on a diversity has been observed in many different systems for taxonomic groups including plants (Adler et al 2001, Anderson et al 2004, insects (Hendrickx et al 2007), fish (Lepori et al 2005), and birds (Fuhlendorf et al 2006, Hovick et al 2015.…”