Ecosphere

Overstory forest structure responds to terrain‐related abiotic factors and to biotic interactions among overstory and understory plants. Unlike species abundance, tree height, biomass, and leaf area in many regions have been poorly quantified in relation to terrain‐driven environmental gradients. In addition, the magnitude of understory influences on overstory structure has been poorly characterized for many forest systems. Our primary goal was to identify relationships between terrain (elevation, convexity, exposure), evergreen understory, and overstory structure (height, aboveground biomass, leaf area) in mature deciduous forests of the southern Appalachian Mountains. We used a combination of field point and plot measurements, LiDAR, and satellite image data to sample little‐disturbed deciduous forest stands. Height, biomass, and gap frequency were significantly related to changes in elevation, exposure (aspect), and convexity (cove to ridge). Higher evergreen understory density was strongly correlated with decreases in forest height and biomass, with an impact observed across moisture, elevation, and exposure gradients. Canopies on ridges averaged half as tall at the highest evergreen understory densities when compared to those without evergreen shrubs (10 vs. 19 m), and overstory canopy height averaged 6 m shorter on sideslopes with high evergreen understory density compared to those with low evergreen understory density. Canopy height declined from low to high elevations, with larger relative decreases on ridges, but biomass increased from low to high elevations, due primarily to high biomass in coves at mid‐ to upper elevations. Biomass and canopy height declined from cove to ridge and north‐ to south‐facing slopes. Responses in canopy height and aboveground biomass associated with changes in understory evergreen density were similar to impacts due to terrain. Gaps were more frequent on south‐facing slopes. Previous studies at this site and others identify soil moisture and soil N competition as the most plausible mechanisms by which understory shrubs might influence overstory canopy structure, with low light limiting seedling recruitment as an additional mechanism. Our work suggests evergreen understory density, particularly on sideslope and ridge locations, substantially affects overstory canopy height and biomass.

Southern Appalachian riparian forests have undergone changes in composition and function from invasive pathogens and pests.Castanea dentatamortality in the 1930s from chestnut blight (Cryphonectria parasitica) andTsuga canadensismortality in the 2000s from the hemlock woolly adelgid (Adelges tsugae) have led to the expansion and increased growth ofRhododendron maximum, an evergreen subcanopy shrub. A better understanding of seed bank characteristics and the various abiotic and biotic factors that affect the seed bank may be useful in determining the restoration potential of forest communities following invasion‐related disturbances. We compared the seed bank of two deciduous forest types: hardwood forests with a denseR. maximumsubcanopy (hereafter,RR) and hardwood forests withoutR. maximum(hereafter,HWD). We evaluated numerous microenvironmental variables through principal component analysis (PCA) and correlated the derivedPCAaxes scores to seed bank density and richness across forest types. We found that seed bank density was comparable between the forests types; however, seed bank richness was much lower inRRthanHWDand the species composition was dissimilar between forest types. Twenty‐eight of 64 (44%) species in the seed bank ofHWDwere not found in the seed bank ofRR. Species that were represented in both forest types were often found in contrasting densities. Most notably, seed bank densities of several woody species were considerably higher inRR(85%) thanHWD(45%), while herbaceous seed bank density was lower inRR(11%) thanHWD(50%). Mineral soilpH, soil nutrient availability, and soil moisture were lower, and organic soil (Oi + Oe + Oa) depth and mass were greater in theRRthanHWDforest type.PCAcorrelations revealed thatPCA4 (represented by understory density and Oe + Oa phosphorus and carbon/nitrogen ratio) was negatively correlated with total seed bank density.PCA1 (represented by Oe + Oa cations and phosphorus, understory richness, ground‐layer cover, and mineral soilpH) andPCA4 were positively correlated with total seed bank richness. These results suggest that the soil seed bank will not be the primary mode of recruitment to establish a diverse and herbaceous‐rich community if a RR is present.

Altered disturbance regimes and shifting climates have increased the need for large‐scale restoration treatments across the western United States. Seed‐sourcing remains a considerable challenge for revegetation efforts, particularly on public lands where policy favors the use of native, locally sourced plant material to avoid maladaptation. An important area of emphasis for public agencies has been the development of spatial tools to guide selection of genetically appropriate seed. When genetic information is not available, current seed transfer guidelines stipulate use of climate‐based or provisional seed transfer zones, which serve as a proxy for local adaptation by representing climate gradients to which plants are commonly adapted. Despite this guidance, little emphasis has been placed on identifying best practices for deriving provisional seed zones or on incorporating predictions from future climate. We describe a flexible, multivariate procedure for deriving such zones that incorporates a broad range of climatic characteristics while accounting for covariation among climate variables. With this approach, we derive provisional seed zones for four regions in the Desert Southwest (the Mojave Desert, Sonoran Desert, Colorado Plateau, and Southern Great Basin). To facilitate future‐resilient restoration designs, we project each zone into its relative position in the future climate based on near‐term, RCP4.5 and RCP8.5 emissions scenarios. Although provisional seed zones are useful in a variety of contexts, there are also situations in which site‐specific guidance is preferable. To meet this need, we implement Climate Distance Mapper, an interactive decision‐support tool designed to help practitioners match seed sources with restoration sites through an accessible online interface. The application allows users to rank the suitability of seed sources anywhere on the landscape based on multivariate climate distances. Users can perform calculations for either the current or future climates. Additionally, tools are available to guide sample effort in regional‐scale seed collections or to partition the landscape into climate clusters representing suitable planting sites for different seed sources. Our tools and analytic procedures represent a flexible and reproducible framework for advancing native plant development programs in the Desert Southwest and beyond.

Transferring plant material during ecological restoration has inherent risk. The use of seed transfer guidelines minimizes the possibility of introducing maladapted genotypes. We delineated biogeographic regions relevant to the distribution of Cercocarpus montanus for the purpose of creating provisional seed transfer zones for ecological restoration. We also modeled seed transfer guidelines using quantitative estimates of environmental tolerance and thresholds. Analyses identified broadscale environmental patterns relevant for seed transfer success. First, a species distribution model was used to identify the distribution of C. montanus. Next, we used non‐metric multidimensional scaling to investigate the structure of environmental data, and hierarchical cluster analysis to delineate biogeographic regions (i.e., environmental discontinuities) using species distribution data. Finally, we calculated measures of environmental tolerance and thresholds for C. montanus to model the probability of seed transfer success with multiple logistic regression. Biogeographic regionalization of C. montanus resulted in four major clusters, which agreed with ordination methods. Logistic regression was implemented using estimates of environmental tolerance and threshold data to model seed transfer success. We compared our species‐specific seed transfer zones and guidelines with other provisional seed transfer zone methods and found that our species‐specific methods performed better at explaining phenotypic variation of C. montanus in four out of six cases. Seed transfer zones are useful for restoration planning; however, zonal models fail to reflect much of the environmental heterogeneity present across the range of C. montanus. Continuous models for seed transfer success using environmental tolerance and thresholds enhance the development and use of seed transfer guidelines because they reflect landscape heterogeneity at a fine scale, and the results are relative to restoration sites of interest. Herein, we describe a methodology to construct provisional seed transfer zones and continuous seed transfer guidelines using species‐specific distribution models and multivariate analyses.

Some of the most impressive adaptations of organisms are in response to periodic environmental variability. To capture these temporal dynamics, statistical models that estimate the spatiotemporal distribution of a species typically include categorical seasonal covariates, temporally varying parameters, or smoothing splines. While these techniques provide a useful starting point, they may require many parameters to estimate and are not well suited for making predictions. Here, we present a technique that uses Fourier series to estimate periodic signals in dynamic occupancy models, and parameterize these models with data from a large‐scale long‐term camera trapping study of medium to large mammals in Chicago, Illinois,USA. Our periodic models captured up to 75% of the temporal variability in species colonization rates and performed similar to dynamic occupancy models with temporally varying parameters. Overall, this method can partition variability between periodic and non‐periodic sources and estimate the proportion of temporal variability that is attributable to a periodic source in a model‐based framework. Further, practitioners can use this method to incorporate prior knowledge on a species' natural history (e.g., natal dispersal and migration). This will, in turn, create more biologically reasonable models for conservation and management applications.

Many plants interact with scatterhoarding animals as mutualists (seed dispersers) and antagonists (seed predators) simultaneously, but the net effects of scatterhoarding animals are rarely measured. In seed‐dispersal mutualisms, plant benefits (recruitment) received from dispersal agents should outweigh the costs, resulting in a relative fitness gain. Otherwise, plant populations cannot be sustained and would go extinct. Here we present a framework to quantify costs and benefits of scatterhoarding for animal‐dispersed plants and propose three models with the three separate scales (seed, tree and population) to quantify the costs and benefits for plants from scatterhoarding rodents. Since scatterhoarding is an adaptive dispersal strategy for many large‐seeded plants, tree‐ and population‐based models are needed to determine the costs and benefits for the plants. In the models presented here, all relevant parameters can be measured by regular surveys. Our tree‐ and population‐based models can be extended to seed plants that have dispersal agents other than scatter hoarding rodents.

Century‐old forests in the U.S. upper Midwest and Northeast power much of North America's terrestrial carbon (C) sink, but these forests' production and C sequestration capacity are expected to soon decline as fast‐growing early successional species die and are replaced by slower growing late successional species. But will this really happen? Here we marshal empirical data and ecological theory to argue that substantial declines in net ecosystem production (NEP) owing to reduced forest growth, or net primary production (NPP), are not imminent in regrown temperate deciduous forests over the next several decades. Forest age and production data for temperate deciduous forests, synthesized from published literature, suggest slight declines in NEP and increasing or stable NPP during middle successional stages. We revisit long‐held hypotheses by EP Odum and others that suggest low‐severity, high‐frequency disturbances occurring in the region's aging forests will, against intuition, maintain NEP at higher‐than‐expected rates by increasing ecosystem complexity, sustaining or enhancing NPP to a level that largely offsets rising C losses as heterotrophic respiration increases. This theoretical model is also supported by biological evidence and observations from the Forest Accelerated Succession Experiment in Michigan, USA. Ecosystems that experience high‐severity disturbances that simplify ecosystem complexity can exhibit substantial declines in production during middle stages of succession. However, observations from these ecosystems have exerted a disproportionate influence on assumptions regarding the trajectory and magnitude of age‐related declines in forest production. We conclude that there is a wide ecological space for forests to maintain NPP and, in doing so, lessens the declines in NEP, with significant implications for the future of the North American carbon sink. Our intellectual frameworks for understanding forest C cycle dynamics and resilience need to catch up to our more complex and nuanced understanding of ecological succession.

Vanilla, an expensive but popular spice used in many industries, faces problems related to its supply. Some of these problems are due to the fact that vanilla cultivation is based on clonal material of a single species (Vanilla planifolia) and is dominated by just a few countries located outside the native growing areas of aromatic vanilla species, which is the neotropics. Despite the economic importance of this crop, relatively little attention has been paid to its wild relatives, in particular with respect to their biology, ecology, and potential use. We hypothesized that species distribution models (SDMs) can identify suitable areas for both the conservation and cultivation of vanilla crop wild relatives (CWRs), following a joint land sparing/land sharing (SPASHA) approach, thus offering alternative sourcing areas and production methods. This is the first study that explored the use of ensemble SDMs to provide applicable land use maps related to the conservation and sustainable cultivation of wild vanilla species in Costa Rica, contributing to a solution for the problems related to current vanilla production systems. We focused on four aromatic vanilla CWRs, native to Costa Rica, to make land use policy recommendations for this country, and more specifically for the biological corridor Osa and its surroundings within our study region Área de Conservación Osa (ACOSA). The resulting distribution maps, with a mean AUC of 0.89, reflected their current potential distribution (ranging from unsuitable to suitable) in Costa Rica. Combining them with recent land use and conservation area maps of our study region, we defined (1) areas for vanilla conservation and (2) areas for sustainable vanilla cultivation within agroforestry systems. These land use recommendations can now be integrated within the National Bio‐Corridor Program (PNCB) that aims at making biological corridors more productive by proposing alternative income generation for local communities living within these areas. Our approach can be applied to identify priority areas for implementing the SPASHA approach on other vanilla CWRs and in more regions across its native growing ranges, given the availability of land use maps and enough occurrence records to build accurate SDMs.

Humans use the coastal ocean and its resources as a source of food and energy, as well as for a variety of other purposes, including transportation and recreation. Over the past several decades, uses of the coastal ocean have been increasingly accompanied by the installation of artificial structures. These artificial structures come in different shapes and sizes, ranging from energy and aquaculture infrastructure that incidentally form habitat for marine organisms to artificial reefs that are often deployed intentionally to become habitat. Marine spatial planning has offered a robust framework for siting artificial structures to minimize conflicts with other uses and maximize societal and economic benefits with other intended uses of the seascape, but ecological criteria are seldom considered in the planning process. In contrast, artificial reefs are intentionally sunk to form structured habitat and provide a variety of ecological functions, yet ecological principles are not often incorporated into the siting and planning process. Instead, artificial reefs are sited largely to advance societal and economic benefits and minimize conflicts with other uses, such as shipping traffic, military use, or impacts to sensitive areas. We outline a framework to further incorporate ecological principles into artificial reef siting, design and construction, and evaluation that features place‐based and adaptive management coupled with tenets from experimental field ecology. This framework accounts for complexities of and interactions among ecological, societal, and economic criteria associated with artificial reefs to ensure they meet defined goals.

In fire‐prone regions, wildfire influences spatial and temporal patterns of landscape heterogeneity. The likely impacts of climate change on the frequency and intensity of wildfire highlights the importance of understanding how fire‐induced heterogeneity may affect different components of the biota. Here, we examine the influence of wildfire, as an agent of landscape heterogeneity, on the distribution of arboreal mammals in fire‐prone forests in south‐eastern Australia. First, we used a stratified design to examine the role of topography, and the relative influence of fire severity and fire history, on the occurrence of arboreal mammals 2–3 years after wildfire. Second, we investigated the influence of landscape context on the occurrence of arboreal mammals at severely burnt sites. Forested gullies supported a higher abundance of arboreal mammals than slopes. Fire severity was the strongest influence, with abundance lower at severely burnt than unburnt sites. The occurrence of mammals at severely burned sites was influenced by landscape context: abundance increased with increasing amount of unburnt and understorey‐only burnt forest within a 1 km radius. These results support the hypothesis that unburnt forest and moist gullies can serve as refuges for fauna in the post‐fire environment and assist recolonization of severely burned forest. They highlight the importance of spatial heterogeneity created by wildfire and the need to incorporate spatial aspects of fire regimes (e.g., creation and protection of refuges) for fire management in fire‐prone landscapes.