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Periodic fire enhances seedling recruitment for many plant species in historically fire-dependent ecosystems. Fire is expected to promote recruitment by generating environmental conditions that promote seedling emergence and survival. However, fire may also increase flowering and seed production. This makes it difficult to distinguish the effects of microsite conditions from seed availability in observational studies of seedling recruitment. Experiments that manipulate seed inputs across a representative range of conditions are needed to elucidate how seed availability versus microsite conditions influence post-fire seedling recruitment and plant demography. We experimentally manipulated time since fire across 36 patches of remnant tallgrass prairie distributed across 6400 ha in western Minnesota (USA). Over two years, we sowed 11,057Echinacea angustifolia(Asteraceae) seeds across 84 randomly placed transects and tracked 974 experimentally sown seedlings to evaluate how time since fire influenced seedling emergence and survival after experimentally controlling for variation in seed inputs. We also quantified six environmental variables and evaluated whether these covariates were associated with seedling emergence and survival. Fire influenced both seedling emergence and seedling survival. Seedlings emerged from approximately 1 percent of all seeds sown prior to experimental burns. Seeds sown one year after experimental burns emerged at 15 times the rate of seeds sown in the fall before burns, but emergence then declined as time since fire increased. Sowing seeds at high densities reduced rates of seedling emergence but increased overall recruitment. Increases in litter depth were associated with reduced emergence. Meanwhile, the probability that seedlings survived to late summer was greatest when they emerged 0-1 years after fire. The probability of seedling survival decreased with litter depth and increased with the local density of conspecific seedlings. Our findings experimentally support widespread predictions that fire enhances seedling recruitment by generating microsite conditions favorable for seedling emergence and survival – especially by increasing the light available to newly emerged seedlings. Nevertheless, recruitment also increased with seed inputs indicating that both seed availability and microsite conditions influence post-fire recruitment. Explicitly discriminating between seed-limitation and microsite-limitation is critical for understanding the demographic processes that influence plant population dynamics in historically fire-dependent ecosystems.
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Is a non-representative convenience sample of adults good enough? Insights from an economic experiment
Recruitment of representative and generalizable adult samples is a major challenge for researchers conducting economic field experiments. Limited access to representative samples or the high cost of obtaining them often leads to the recruitment of non-representative convenience samples. This research compares the findings from two field experiments involving 860 adults: one from a non-representative in-person convenience sample and one from a representative online counterpart. We find no meaningful differences in the key behaviors of interest between the two samples. These findings contribute to a growing body of literature demonstrating that nonrepresentative convenience samples can be sufficient in certain contexts.
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- Award ID(s):
- 1757353
- PAR ID:
- 10513844
- Publisher / Repository:
- Springer
- Date Published:
- Journal Name:
- Journal of the Economic Science Association
- Volume:
- 9
- Issue:
- 2
- ISSN:
- 2199-6784
- Page Range / eLocation ID:
- 293 to 307
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1007/s40881-023-00135-5
