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In Jeffrey pine (Pinus jeffreyi) forests, which once supported a frequent, mostly low severity fire regime, fire suppression has led to notable changes in forest structure and fuel loads. In parts of California, prescribed fire has been used to decrease fuel loads and reduce the risk of high intensity fire in these forests. Previous work has shown that circular litter-free clearings form around Jeffrey pine trees following prescribed burns and that they can reduce tree damage and potentially increase the chance of survival in a subsequent wildfire. In this study we aim to determine the factors responsible for maintaining clearings around trees after a fire occurs. Using a set of field experiments and observational studies, we show that a combination of natural processes, including reduced litter deposition near trees, and the movement of needles away from trees by ants (Formica sibylla) and wind, reduce the amount of litter near trees and likely contribute to the long-term maintenance of clearings. Stem flow resulting from rare heavy rain events also appears to play a role in clearing maintenance. All of the abiotic factors investigated interact with the physical structure of the tree to remove pine needles from the bases of trees, but ants move needles independently to facilitate clearing maintenance and indirectly enhance tree fitness when fires occur. Given how generally common F. sibylla is in Jeffrey pine habitat and the relative stability of the abiotic processes that also contribute to maintaining clearings (wind, precipitation, and needle fall), we may expect to see clearings form in other Jeffrey pine forests after prescribed fires are introduced.

The increased demand of food produced through sustainable agriculture has resulted in localised amelioration of intensive management imposed by agroecosystems. However, these newly available niches are often isolated and plant species may not be able to recolonise fragmented agroecosystems from where they have been extirpated. Plant reintroduction can overcome dispersal limitation in agroecosystems but may also generate conflicts that jeopardise conservation efforts. Conflicts arise when reintroductions are perceived to place constraints on the management and productivity of agroecosystems: the translocated plants may require space sharing with crops, may have negative effects on crop yields, and come with the expectation that farmers must modify their farming practices and accommodate legal obligations deriving from protected species status. Benefits include economic incentives that pay farmers through CAP, the conservation of nature, ecosystem services, an effective marketing strategy and increased aesthetic value that might generate ecotourism.\ud \ud We discuss the practical implications of the abovementioned issues by reference to two cases of European species in which different approaches to reintroduction resulted in opposite outcomes (i.e., consensus vs. opposition). Coexistence of threatened plants and crops is possible if farmers and local stakeholders are involved in a conservation project from an early stage and if farmers conservation efforts turn into benefits for their income. Based on these considerations, we propose a strategic framework to promote reintroduction of threatened plants in agroecosystems (land sharing) and policy advancement aimed at recognising the role of farmers in maintaining biodiversity on their lands.

Frugivory and seed dispersal contribute to the maintenance and regeneration of plant communities through transportation of seeds and enhancing germination through seed processing mechanisms. The effects of mammalian frugivore seed processing mechanisms on seed germination are generally well studied and the potential benefits include disinhibition (pulp removal), scarification (gut passage) and fertilisation (from faecal matrix). Nevertheless, our review found that there is bias in the comparative treatments included in seed dispersal studies through exclusion of entire fruit control groups and the fertiliser effect. In this study, we aimed to address such bias by using ecologically relevant experiments to investigate the influence of seed processing mechanisms on germination probability and latency of selected locally abundant fleshy-fruiting plant species, common in the diet of samango monkeys (Cercopithecus albogularis schwarzi), and who are seed-spitters (disinhibition) and seed-swallowers (gut-passage and fertiliser effects). We designed experiments to isolate the cumulative effects of seed processing mechanisms and tested the effects of five treatments and one control treatment (entire fruit). We further assessed if exclusion of ecologically relevant seed treatments or relevant controls would affect our interpretation of the impact of the disperser on seed germination. Comparing gut passage and disinhibition indicated negative effects, whereas comparing gut passage and entire fruit controls indicated neutral effects in one species. Compared with gut passage alone, the fertiliser effects indicated positive or neutral benefits on germination probability. Our study demonstrated that the impacts of mammalian frugivores on germination may be under- or over-estimated in ecological literature where relevant treatments and meaningful controls are excluded.

Seed persistence is a trait that is difficult to observe or measure and, consequently has remained conceptually obscure for 40 years since Grubb’s influential description of the regeneration niche. Seed persistence is the ability of seeds to persist in a viable state post-dispersal and is relevant to current research in plant community dynamics and conservation. However, categorisations of seed persistence as transient, short-term or long-term persistent do not acknowledge the variation in persistence times as a result of deterministic processes and are difficult to apply in a predictive capacity. Consequently, a more robust understanding of seed persistence is needed in niche descriptions that are temporally explicit and in predicting the distributional changes of species in the current and future climate. We surmise an alternative to the categorizations of seed persistence on the basis of seed bank type and argue that it is best expressed as a continuous variable. We review the methods available for estimating seed persistence in situ and provide a number of testable hypotheses to contribute to the development of this important research topic. We maintain that seed persistence has not been incorporated adequately into niche theory and highlight that it can make several contributions including properly defining metapopulation niche, population growth definition. This holistic approach by integrating seed persistence into niche theory would allow us to better predict the survival of plants in a changing environment.

In the western United States, trees in pine-dominated forests historically characterized by frequent, low severity wildfires often support deep litter and duff accumulations due to the fire exclusion policies of the last century. These accumulations at the bases of trees can smolder for long periods of time after the passage of fire, which can result in high temperatures, cambial injury, and subsequent tree mortality. As a result, prescribed fire prescriptions often call for the manual removal of litter and duff from the bases of large trees by raking or other means before fire is applied. Here we report on the presence of naturally formed, circular clearings in the soil surface litter layer that occur around the bases of tree boles in seasonally dry forests dominated by Pinus jeffreyi (Jeffrey pine) in eastern California and Baja California (along the eastern edge of the North American Mediterranean-climate zone). We show that such clearings significantly reduce fire severity and tree mortality in surface fires. In the Lake Tahoe Basin (LTB) study area, Jeffrey pine individuals surrounded by clearings experienced much lower bole char heights, and were 1/3 as likely to support crown torching as individuals lacking the clearings; mortality of Jeffrey pine lacking clearings was more than five times higher than individuals surrounded by clearings. Clearings also reduced mortality in incense cedar and white fir. Data from both the LTB and Inyo National Forest (INF) study areas show that clearings are larger and much more common in forests that have recently burned at low severity. In both locations, natural clearings around trees were about four times more common, and existing clearings about three times wider, in recently burned versus long unburned (>60 years) sites. Logistic regression models show that clearing size, specifically the percentage of tree bole surrounded by a clearing, is an important predictor of Jeffrey pine survivorship in low to moderate severity fires, but clearing measures have never been included in previously published assessments of tree survival. We suggest that these previously unreported clearings are important features of Jeffrey pine and related semiarid forests and we recommend that more in-depth studies be made of their occurrence, formation, and ecological relationships.

We developed an ‘assured fitness returns’ model for the evolution of sociality independent of high relatedness within colonies. We first developed this model based on parameters from the northern social spider Anelosimus studiosus, which shows a higher incidence of multiple-female colonies caring for a common brood at higher latitudes and colder conditions within latitudes. The mathematical model developed predicts that multiple females will cooperatively care for a brood in those environments in which a single female has a high probability of dying before her offspring are able to care for themselves. The frequency of multiple-female nests observed in variable temperature sites in eastern Tennessee, U.S.A., is consistent with that found in our latitudinal censuses: a higher frequency of multiple-female colonies was present at cold-water sites than at warm-water sites. A test of a critical model assumption found a positive correlation of temperature and juvenile development rate in both the field and the laboratory. Colony success in field studies was also consistent with model predictions.