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Understanding patterns of seed predation in tallgrass prairie restorations is vital because seed additions are often used by managers to increase diversity and promote native species. However, the success of seed additions depends on the extent of seed predation. It is not clear how seed predation varies through time and to what extent it is affected by various commonly used management techniques in grasslands (e.g. spring or fall prescribed burns, mowing). We examined how predation ofSorghastrum nutansseeds changed during eight trials between June 2018 and April 2019 in plots that received one of four different plant litter removal treatments (fall mow, fall burn, spring burn, and unaltered control). Granivory varied throughout the year, reaching its peak in the late fall and early winter. However, we found that seed predators consumed significantly fewer seeds when litter was removed following fall burn and fall mow treatment applications. These treatments occurred during times when granivory was otherwise high in areas where litter remained intact (control and spring burn plots). Our findings highlight the importance of management decisions and how they interact with granivory in grassland restorations. Both time of year and litter cover determine seed predation rates; seed predators consume more seeds when seeds are abundant but rely on intact litter cover while foraging. This suggests that if seeds are added during the fall, litter should be removed to minimize the loss of seeds to granivory. Alternatively, seed additions during the spring are likely to experience lower rates of seed predation.
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Interactions between large‐scale and local factors influence seed predation rates and seed loss
Abstract Herbivores often have highly variable impacts on plant fecundity. The relative contribution of different environmental factors operating at varying spatial scales in affecting this variability is often unclear. We examined how density‐dependent seed predation at local scales and regional differences in primary productivity are associated with variation in the magnitude of pre‐dispersal seed predation onMonarda fistulosa(Lamiaceae). WithinM. fistulosapopulations growing in a low‐productivity region (LPR), Montana, USA, and a high‐productivity region (HPR), Wisconsin, USA, we quantified the magnitude of pre‐dispersal seed predation among individual plants differing in seed head densities. Out of a total of 303M. fistulosaplants that were surveyed, we found half as many herbivores in seed heads in the LPR (n = 133 herbivores) compared to the HPR (n = 316). In the LPR, 30% of the seed heads were damaged in plants with low seed head density, while 61% of seed heads were damaged in plants with high seed head density. Seed head damage was consistently high in the HPR (about 49% across the range of seed head density) compared to the LPR (45% across a range of seed head density). However, the proportion of seeds per seed head that were destroyed by herbivores was nearly two times higher (~38% loss) in the LPR compared to HPR (22% loss). Considering the combined effects of probability of damage and seed loss per seed head, the proportion seed loss per plant was consistently higher in the HPR regardless of seed head density. Nevertheless, because of greater seed head production, the total number of viable seeds produced per plant was higher in HPR and high‐density plants, despite being exposed to greater herbivore pressure. These findings show how large‐scale factors can interact with local‐scale factors to influence how strongly herbivores suppress plant fecundity.
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- Award ID(s):
- 1901552
- PAR ID:
- 10427150
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Ecology and Evolution
- Volume:
- 13
- Issue:
- 6
- ISSN:
- 2045-7758
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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