Shrubs indirectly increase desert seedbanks through facilitation of the plant community

The mechanisms supporting positive ecological interactions are important. Foundation species can structure desert biodiversity by facilitating seedbanks of annual plants, but the direct and indirect mechanisms of shrub effects on seedbank have not been experimentally decoupled. We conducted the first test of shrubs increasing seedbank densities through direct effects on the seedbank (i.e. shrub seed-trapping, animal-mediated dispersal) and indirect effects by facilitating the annual plant community (i.e. seed deposition, annual seed-trapping). Two distinct desert ecosystems were used to contrast transient seedbank densities in shrub and open microsites by manipulating annual plant density and the presence of the persistent seedbank. We measured transient seedbank densities at the end of the growing season by collecting soil samples and extracting seeds from each respective treatment. Transient seedbank densities were greatest in shrub canopies and with relatively higher annual plant densities. The persistent seedbank contributed to transient seedbank densities only in one desert and in the open microsite. Shrubs indirectly increased seedbank densities by facilitation the seed production of the annual plants. Therefore, shrubs are increasing seedbank independently of the annual plant community, likely through trapping effects, and dependently by facilitating seed production of the annuals. These findings provide evidence for a previously undescribed mechanism that supports annual seedbanks and thus desert biodiversity. We also identify shrubs as being significant drivers of desert plant communities and emphasize the need to consider multiple mechanisms to improve our ability to predict the response of ecosystems to change.York University Librarie

A checklist for choosing between R packages in ecology and evolution

The open source and free programming language R is a phenomenal mechanism to address a multiplicity of challenges in ecology and evolution. It is also a complex ecosystem because of the diversity of solutions available to the analyst. Packages for R enhance and specialize the capacity to explore both niche data/experiments and more common needs. However, the paradox of choice or how we select between many seemingly similar options can be overwhelming and lead to different potential outcomes. There is extensive choice in ecology and evolution between packages for both fundamental statistics and for more specialized domain‐level analyses. Here, we provide a checklist to inform these decisions based on the principles of resilience, need, and integration with scientific workflows for evidence. It is important to explore choices in any analytical coding environment—not just R—for solutions to challenges in ecology and evolution, and document this process because it advances reproducible science, promotes a deeper understand of the scientific evidence, and ensures that the outcomes are correct, representative, and robust.York University Librarie

Examining Mechanisms of Positive Plant Interactions in Deserts

Deserts are ecologically important ecosystems that contain high levels of endemism and that are sensitive to global change. Positive interactions among plants have been cited as factors that support desert biodiversity by buffering against climate variability. However, there is limited understanding on the underlying mechanisms that determine positive plant interactions. Herein, we proposed a conceptual framework that describes multiple mechanisms of facilitation among plants. We then empirically tested in multiple deserts of California the different facilitation mechanisms in the context of extreme climate events, multiple stressors, and spatial gradients. We also conducted species distribution modelling to assess the role of positive interactions in expanding the niche and geographic range of beneficiary species. We expanded upon the previous literature by describing six mechanisms of facilitation and two meta-mechanisms. We found in experimentation that shrubs can buffer against extreme drought using the described mechanisms, but that facilitation effects are strongest at intermediate or low levels of abiotic stress. The shrub species used was found to deter herbivory and ameliorate abiotic stress, but not increase soil moisture. We also found shrub facilitation to be species specific and typically increased the biomass of plant species with more competitive traits. Consequently, non-native species were found to be frequently facilitated and shrubs were observed to have lower species richness. Positive interactions were determined to increase the geographic range of annual plant species that have been previously reported as facilitated in the literature. We challenged previous research that suggests positive interactions increase linearly with abiotic stress and that facilitation can buffer against climate variability. Shrubs were determined to be significant foundation species in these desert ecosystems supporting annual productivity and the unique occurrence of annual species. However, these interactions are more sensitive to global change than previously thought and could collapse at environmental extremes. The proposed framework and experiments provides better understanding into the predictability of positive plant interactions and an opportunity for future applied research into the restoration and conservation of desert ecosystems

Dataset for A systematic review and conceptual framework for the mechanistic pathways of nurse plants

<p>Aim To conceptualize the mechanistic pathways of the nurse-plant syndrome by life-form and to identify the implications of positive plant–plant interactions for landscape and evolutionary ecology.</p> <p>Location Global.</p> <p>Methods We conducted a quantitative review examining 298 articles to catego- rize the literature on nurse-plant interactions based on geographic region, mecha- nism of facilitation, ecological hypothesis and nurse life-form.</p> <p>Results A total of nine different nurse mechanisms were identified and two were classified as meta-mechanisms. We found that shrubs were the dominant nurse life-form (46% of total studies) and that studies of positive plant interactions were most frequent in areas of high abiotic stress. Nurse-plant studies were also distrib- uted unevenly around the globe with nearly a quarter in the South American Andes and Spain. Studies testing the direct nurse–protégé interactions were the most frequently performed, including the ecophysiological responses of protégé species (32.2%). Research gaps identified in the nurse-plant literature included indirect interactions and seed trapping as well as the large-scale implications for landscape ecology and evolution.</p> <p>Main conclusions Nurse plants are often considered keystone species because they commonly structure plant communities. This is an important confirmatory finding in many respects, but it is also novel in that it challenges traditional plant ecology theory and has important implications for landscape-level dynamics over time. The categorization of mechanisms proposed provides a conceptual frame- work useful for organizing the research to date and can accelerate linkages with theory and application by identifying important connections. It is becoming increasingly apparent that future studies of the nurse-plant syndrome must decouple and consider multiple mechanisms of interaction to explain the processes that influence community structure, particularly in high-stress conditions, given a changing climate and potential shifts in biodiversity.</p

York NSTP Conference 2014 - Filazzola NSTP analyses

<p>R script for analyses of data collected at Pink Mountains, British Columbia for the Northern Studies Training Program (Canada). </p

A conceptual framework of nurse-plant mechanisms

<p>A conceptual framework for the abiotic and biotic mechanisms of nurse-plant effects studied in the ecological literature. Nurse mechanisms are ordered based on effect of protégé life-stage and the clockwise motion around figure represents the progression of a plant through its life history (i.e. Seed, seedling, plant/growth, reproduction). Listed to the right are possible nurse-protégé responses.</p

Contrasting the differences in the micro-environment of green and conventional roofs in Toronto, Canada.

<p>Purpose: To see how temperature, soil moisture, and light availability differ between green and conventional rooftops at York University, Toronto.</p> <p>Hypothesis: Green roofs ameliorated the microclimate of a building by absorbing solar radiation, resulting in cooler temperatures and less evapotranspiration.</p> <p>To compare how green roofs may alter the temperature, evapotranspiration or solar radiation, we placed four sets of three Parrot Flower Power sensors in 6” pots filled with soil. Each set of pots and Flower Power sensors were be placed on two green roofs and two non-green roofs at York University. These four roofs were surveyed from September 16th to November 9th and data collected periodically. Soil moisture changes within the pots was used as a proxy for the evapotranspiration rate on top of the roofs. Data points were extracted for each day using the software Web Plot Digitizer. One set of loggers on a tradional roof did not record for the duration of the season. </p> <p> </p

Basal plant facilitation extends to insect community structure and diversity in the Mojave Desert, California

<p>Hypothesis: Larrea tridentata positively influences the abundance and diversity of the insects within its canopy</p> <p>Predictions:</p> <p>1.Insect community composition differs between microsites under the L. tridentata canopy and in the open</p> <p>2.Insect abundance differs between microsites under the L. tridentata canopy and in the open</p> <p>3.Dominant insect species such as pollinators benefit more strongly from L. tridentata facilitation</p> <p>Significance:</p> <p>Shrubs positively influenced insect community structure, but there was no evidence for differences in relative abundance between functional groups of insects (bees and non-bees) suggesting that trophic and non-trophic effects are driven primarily by the shrubs.</p> <p>Management of these desert shrubs can enhance insect biodiversity and can also increase potential pollination rates of desert annual plant species.</p> <p>The mechanistic pathways used by L. tridentata to enhance the insect community need to be examined in order to decouple the direct and indirect effects.</p> <p> </p

Winter and summer storms modify chlorophyll relationships with nutrients in seasonally ice‐covered lakes

Abstract At broad spatial scales, primary productivity in lakes is known to increase in concert with nutrients, and variables that may disrupt or modify the tight coupling of nutrients and algae are of increasing interest, particularly for those shifting with climate change. Storms may disrupt algae–nutrient relationships, but the expected effects differ between winter and summer seasons, particularly for seasonally ice‐covered lakes. In winter, storms can dramatically change the under‐ice light environment, creating light limitation that disrupts algae–nutrient relationships. Further, storms can bring both snow that blocks light and also wind that blows snow off of ice. In open water conditions, storms may promote turbulence and external nutrient loading. Here, we test the hypotheses that winter and summer storms differentially affect algae–nutrient relationships across 84 seasonally ice‐covered lakes included in the Ecology Under Lake Ice dataset. While nutrients explained most of the variation in chlorophyll across these lakes, we found that secondary drivers differed between seasons. Under‐ice chlorophyll was higher under a variety of precipitation and wind conditions that tend to promote snow‐free clear ice, highlighting the importance of light as a limiting factor for algal growth during winter. In summer, higher water temperatures and storms corresponded with higher chlorophyll. Our study suggests that examining ice‐covered lakes in a gradient from the perennial ice cover of the poles to the intermittent ice cover of lower latitudes would yield key information on the shifts in light and nutrient limitation that control algal biomass

Species occurrence list for SDM of positive plant-interactions

Species distribution models we developed examining shrub-annual associations in the Mojave desert. Species within this study were separated into three classes. 1) facilitated - previously reported to be a beneficiary species, 2) unreported - unknown to have been a beneficiary species, 3) shrub - a previously reported benefactor species. These details were obtained from the scientific literature. The dataset contains the list of occurrences for the facilitated species, unreported species and  shrub-benefactor species. The occurrences were downloaded using GBIF