Long-term, large-scale experiment reveals the effects of seed limitation, climate, and anthropogenic disturbance on restoration of plant communities in a biodiversity hotspot

Abstract

Ecological restoration is essential for maintaining biodiversity in the face of dynamic, global changes in climate, human land use, and disturbance regimes. Effective restoration requires understanding bottlenecks in plant community recovery that exist today, while recognizing that these bottlenecks may relate to complex histories of environmental change. Such understanding has been a challenge because few long-term, well-replicated experiments exist to decipher the demographic processes influencing recovery for numerous species against the backdrop of multiyear variation in climate and management. We address this challenge through a long-term and geographically expansive experiment in longleaf pine savannas, an imperiled ecosystem and biodiversity hotspot in the southeastern United States. Using 48 sites at three locations spanning 480 km, the 8-y experiment manipulated initial seed arrival for 24 herbaceous plant species and presence of competitors to evaluate the impacts of climate variability and management actions (e.g., prescribed burning) on plant establishment and persistence. Adding seeds increased plant establishment of many species. Cool and wet climatic conditions, low tree density, and reduced litter depth also promoted establishment. Once established, most species persisted for the duration of the 8-y experiment. Plant traits were most predictive when tightly coupled to the process of establishment. Our results illustrate how seed additions can restore plant diversity and how interannual climatic variation affects the dynamics of plant communities across a large region. The significant effects of temperature and precipitation inform how future climate may affect restoration and conservation via large-scale changes in the fundamental processes of establishment and persistence.

Sandy seeds: Armour or invisibility cloak? Mucilage‐bound sand physically protects seeds from rodents and invertebrates

“…In addition to studies that explore these novel hypotheses, our work suggests that mucilage could be incorporated into conservation and restoration strategies that rely upon seed additions to promote biodiversity (e.g. Orrock et al, in press). In our study, we easily coated thousands of seeds with sand, and these seeds were much less likely to be consumed by granivores.…”

The past as a lens for biodiversity conservation on a dynamically changing planet

“…Orrock et al. ( 25 ) report findings from a near-decade-long regional experiment to identify taxa, ecosystems, and their characteristics that benefit most from connected landscapes. They conducted a long-term and large-scale replicated experiment across the southeastern United States, manipulating seed arrival and neighboring competitors to evaluate joint impacts of timber densities, prescribed fire strategies, soil conditions, and climate on establishment and persistence.…”

“…Orrock et al. ( 25 ) identify specific plant traits and environmental conditions that promote resilience under changing climates, maximizing conservation and restoration potential. Notably, they find that the strongest factor to influence plant establishment is seeding, or the presence of seeds in an area, while warming temperatures inhibit establishment.…”

“…Orrock et al. ( 25 ) identify how to best promote climate tracking in plants, whereas Wang et al. ( 33 ) evaluate the extent to which different taxa have geographic ranges that will be strictly dictated by climate.…”

Fit by design: Developing substrate-specific seed mixtures for functional dike grasslands

“…Restoration is seen as a key factor to sustain biodiversity and ecosystem services ( Convention on Biological Diversity ( CBD ), 2014; United Nations, 2019), and sowing is a well-established approach to establish species-rich grasslands (Kiehl et al, 2010). Sowing high-diversity mixtures of local provenance produced by specialized companies is a promising way to scale up restoration efforts (Freitag et al, 2021), and to overcome dispersal filters (Myers & Harms, 2009; Orrock et al, 2023). However, there are still open questions about adjusting seed mixtures to specific site conditions and future climate conditions (Török et al, 2021).…”