Abiotic Heterogeneity Research Articles

An elevational cline in leaf variegation: Testing anti-herbivory and abiotic heterogeneity hypotheses in maintaining a polymorphism.

While some studies have found leaf variegation to reduce photosynthetic capacity, others showed that it can increase photosynthesis. Thus, what maintains variegation remains an open question. Two primary hypotheses-the anti-herbivory and abiotic heterogeneity hypotheses-have been posited, yet little empirical research explicitly investigates the maintenance of naturally occurring variegation. We used field surveys, image analysis, and climatic associations to explore the anti-herbivory and abiotic heterogeneity hypotheses in 21 populations of Hexastylis heterophylla and H. shuttleworthii, both polymorphic for leaf variegation. We measured the frequency of variegated individuals, variegation intensity, and herbivory for each morph, assessed abiotic correlates with variegation, and measured photosynthetic efficiency. We found a strong elevational cline in leaf variegation strongly linked with abiotic heterogeneity; variegation was more common in lower-elevation populations characterized by higher temperatures, UV-B exposure, seasonal light change, and drier, more basic soils. Variegated and nonvariegated individuals experienced similar levels of herbivory. Morphs had similar photosynthetic quantum yields. However, nonvariegated leaves experienced more nonphotochemical quenching, an indication of photoinhibition, and had higher surface temperatures under high light. Our results suggest that variegation may serve as an adaptation to high temperatures and light conditions and can reduce photoinhibition in certain environmental contexts. Thus, abiotic factors can maintain variegation in wild populations and shape geographic clines in variegation.

Contrasting mechanisms of non‐vascular and vascular plants on spatial turnover in multifunctionality in the Antarctic continent

Abstract Dominant plants play crucial roles in supporting the functioning of terrestrial ecosystems. Plants can influence the spatial heterogeneity of environmental factors, as well as the spatial turnover in the composition of soil communities (i.e. β‐diversity of soil communities). However, we still poorly understand how dominant plants drive the spatial turnover in multiple ecosystem functions (β‐multifunctionality hereafter), and to which extent the effects of dominant plants are mediated by changes in environmental heterogeneity and the β‐diversity of soil communities. Antarctica supports one of the most challenging environments on the planet including low temperature and water availability. Here, we collected soil samples under three dominant plants (lichen, moss and vascular plants) and bare ground. We measured carbon storage, nutrient availability, nutrient decomposition, microbial biomass and pathogen control to calculate β‐multifunctionality. Both non‐vascular and vascular plants were associated with increased β‐multifunctionality compared to bare ground. We further showed that lichen mainly affected β‐multifunctionality through soil temperature heterogeneity and β‐bacterial diversity. Similarly, moss mainly affected β‐multifunctionality through the spatial heterogeneity of soil water content and β‐bacterial diversity. However, vascular plants did not significantly affect environmental heterogeneity. Instead, the responses of β‐multifunctionality to vascular plants were mainly driven by the β‐diversity of soil communities. These results indicate that environmental heterogeneity is important for turnover in multiple ecosystem functions in early successional stages (dominated by non‐vascular plants), while the importance of soil communities' heterogeneity becomes more significant in late successional stages (dominated by vascular plants). Synthesis. Our findings highlight the fundamental role of dominant plants in controlling the spatial turnover in ecosystem functions, and suggest that accelerated succession under current climate warming may increase bacterial β‐diversity but decrease abiotic heterogeneity, thereby leading to both increases (e.g. regarding functions related to microbial biomass) and decreases (e.g. regarding functions related to nutrient availability) in β‐multifunctionality and hence the spatial turnover in levels of ecosystem functioning.

The forgotten forests: Incorporating temperate peat‐forming wet woodlands as nature‐based solutions into policy and practice

Abstract Peat‐forming wet woodlands (forested wetlands) are naturally occurring carbon‐dense ecosystems that have considerable potential to form an important part of net zero woodland establishment and peatland strategies, as well as provide crucial co‐benefits to restore biodiversity and regulate hydrological systems. Despite their potential, temperate peat‐forming wet woodlands have been widely lost, are critically understudied and are being overlooked in land‐use strategies. Unlike temperate ‘dry’ woodlands, some wet woodlands are peat forming and can store large amounts of carbon below‐ground in peat in addition to the carbon in the tree biomass. The complex structure of these peat‐forming wet woodlands creates high abiotic heterogeneity, resulting in a wide variety of microhabitats to support high levels of biodiversity, and this structural complexity can also increase water storage in the landscape and slow flood flows, providing natural flood protection. Co‐written by experts in academia and UK Government, we highlight critical knowledge gaps in our understanding of peat‐forming wet woodlands that, once addressed, could form the basis for radical changes to their inclusion in net zero and land‐use policies. Policy and practice implications: The significant role that peatland restoration has to play in reaching net zero presents an immediate policy opportunity to consider the full range of ecosystems to achieve net zero targets, while protecting and enhancing socio‐ecological sustainability. In co‐writing this paper, our aim is to stimulate discussion and sharing of knowledge between those involved in research, policy and practice in order to strengthen the evidence base for peat‐forming wet woodland re‐establishment and future management. We call on researchers, policymakers and land managers to take temperate wet woodlands from understudied and overlooked, to integrated ecosystems that hold great promise in the contributions they can make as nature‐based solutions.

Microgeographic variation in demography and thermal regimes stabilize regional abundance of a widespread freshwater fish.

Predicting the persistence of species under climate change is an increasingly important objective in ecological research and management. However, biotic and abiotic heterogeneity can drive asynchrony in population responses at small spatial scales, complicating species-level assessments. For widely distributed species consisting of many fragmented populations, such as brook trout (Salvelinus fontinalis), understanding the drivers of asynchrony in population dynamics can improve the predictions of range-wide climate impacts. We analyzed the demographic time series from mark-recapture surveys of 11 natural brook trout populations in eastern Canada over 13 years to examine the extent, drivers, and consequences of fine-scale population variation. The focal populations were genetically differentiated, occupied a small area (~25 km2 ) with few human impacts, and experienced similar climate conditions. Recruitment was highly asynchronous, weakly related to climate variables and showed population-specific relationships with other demographic processes, generating diverse population dynamics. In contrast, individual growth was mostly synchronized among populations and driven by a shared positive relationship with stream temperature. Outputs from population-specific models were unrelated to four of the five hypothesized drivers (recruitment, growth, reproductive success, phylogenetic distance), but variation in groundwater inputs strongly influenced stream temperature regimes and stock-recruitment relationships. Finally, population asynchrony generated a portfolio effect that stabilized regional species abundance. Our results demonstrated that population demographics and habitat diversity at microgeographic scales can play a significant role in moderating species responses to climate change. Moreover, we suggest that the absence of human activities within study streams preserved natural habitat variation and contributed to asynchrony in brook trout abundance, while the small study area eased monitoring and increased the likelihood of detecting asynchrony. Therefore, anthropogenic habitat degradation, landscape context, and spatial scale must be considered when developing management strategies to monitor and maintain populations that are diverse, stable, and resilient to climate change.

Topographic Heterogeneity and Aspect Moderate Exposure to Climate Change Across an Alpine Tundra Hillslope

AbstractAlpine tundra ecosystems are highly vulnerable to climate warming but are governed by local‐scale abiotic heterogeneity, which makes it difficult to predict tundra responses to environmental change. Although land models are typically implemented at global scales, they can be applied at local scales to address process‐based ecological questions. In this study, we ran ecosystem‐scale Community Land Model (CLM) simulations with a novel hillslope hydrology configuration to represent topographically heterogeneous alpine tundra vegetation across a moisture gradient at Niwot Ridge, Colorado, USA. We used local observations to evaluate our simulations and investigated the role of topography and aspect in mediating patterns of snow, productivity, soil moisture, and soil temperature, as well as the potential exposure to climate change across an alpine tundra hillslope. Overall, our simulations captured observed gradients in abiotic conditions and productivity among heterogeneous, hydrologically connected vegetation communities (moist, wet, and dry). We found that south facing aspects were characterized by reduced snowpack and drier and warmer soils in all communities. When we extended our simulations to the year 2100, we found that earlier snowmelt altered the timing of runoff, with cascading effects on soil moisture, productivity, and growing season length. However, these effects were not distributed equally across the tundra, highlighting potential vulnerabilities of alpine vegetation in dry, wind‐scoured, and south facing areas. Overall, our results demonstrate how land model outputs can be applied to advance process‐based understanding of climate change impacts on ecosystem function.

Interactions between diurnal winds and floodplain mosaics control the insect boundary layer in a river corridor

Insect flight along river corridors is a fundamental process that facilitates sustainable succession and diversity of aquatic and terrestrial insect communities in highly dynamic fluvial environments. This study examines variations in the thickness of the insect boundary layer (i.e., the pre-surface atmosphere layer in which air velocity does not exceed the sustained speed of flying insects) caused by interactions between diurnal winds and the heterogenous habitat mosaics in the floodplain of a braided river. Based on advective–diffusive theory, we develop and test a semi-empirical model that relates vertical flux of flying insects to vertical profiles of diurnal winds. Our model suggests that, in the logarithmic layer of wind, the density of insect fluxes decreases exponentially with the altitude due to the strong physical forcing. Inside the insect boundary layer, the insect fluxes can increase with the altitude while the winds speed remains nearly constant. We suggest a hypothesis that there is a close correspondence between the height of discontinuity points in the insect profiles (e.g. points with abrupt changes of the insect flux) and the displacement heights of the wind profiles (e.g. points above which the wind profile is logarithmic). Vertical profiles were sampled during three time-intervals at three different habitat locations in the river corridor: a bare gravel bar, a gravel bar with shrubs, and an island with trees and shrubs. Insects and wind speed were sampled and measured simultaneously over each location at 1.5-m intervals up to approximately 17 m elevation. The results support our working hypothesis on close correspondence between discontinuity and displacement points. The thickness of the insect boundary layer matches the height of the discontinuity points and was about 5 m above the bare gravel bar and the gravel bar with shrubs. Above the island, the structure of the insect boundary layer was more complex and consisted of two discontinuity points, one at the mean height of the trees’ crowns (ca. 15 m), and a second, internal boundary layer at the top of the shrubs (ca. 5 m). Our findings improve the understanding of how vegetation can influence longitudinal and lateral dispersal patterns of flying insects in river corridors and floodplain systems. It also highlights the importance of preserving terrestrial habitat diversity in river floodplains as an important driver of both biotic and abiotic (i.e., morphology and airscape) heterogeneity.

Processes underlying the assembly of plant communities: The role of environmental filtering heterogeneity in a competition–dispersal experiment

AbstractQuestionInterspecific competition and seed dispersal are key mechanisms that may influence plant community assembly, but their relative importance remains difficult to disentangle as they can be affected by abiotic conditions (environmental filtering). We experimentally studied the balance between these processes in a Molinia wet meadow plant community in which abiotic constraints are mostly represented by flooding, while agricultural practices such as mowing prevent the dominance of a few competitive species. We hypothesized that (H1) mowing, by decreasing competitive exclusion and (H2) seed addition, by increasing immigration, both enhance plant species diversity, and that (H3) small variations in flooding intensity become secondary to these processes in determining species assembly.LocationFrench National Nature Reserve “Etang de Cousseau”, Nouvelle Aquitaine, France.MethodsIn a three‐year experiment, we added seeds of 17 species characteristic of Molinia wet meadows and managed above‐ground competition through mowing. We measured spatial variations in soil moisture as an indicator of the flooding regime. We recorded species relative cover, species richness and evenness annually, and measured light availability, linked with canopy openness, twice.ResultsFrom the beginning of the experiment, small‐scale variations in soil moisture mainly affected species richness, composition and evenness, and canopy openness. Mowing significantly increased light availability and evenness, and affected the relative cover of several species, but not species richness. The addition of seeds did not influence any of the variables monitored during the experiment.ConclusionOur study helps to disentangle processes underlying community assembly in wet meadows. It demonstrates significant and rapid effects of mowing on canopy opening and on community assembly, while seed addition had only a slight effect, possibly explained by an insufficient decrease in competitive interactions through mowing or unmeasured processes. It also shows that abiotic heterogeneity remains a primary driver of community assembly, even on a small scale. Finally, our results suggest that the respective weight of the different filters (dispersion, environment, competition) is subject to interannual variability or environmental stochasticity.

Effects of abiotic heterogeneity on species densities and interaction strengths lead to different spatial biodiversity patterns

During community assembly, abiotic factors can influence species at multiple stages during their life history, for example by affecting early settlement or establishment probabilities and thus initial densities (route 1: abiotic effects on density), or later by affecting the strength of biotic interactions during subsequent life stages (route 2: abiotic effects on interaction strengths). Since real abiotic landscapes are multivariate and complex, how these two distinct routes of abiotic influence affect community patterns has not been quantified. Using an individual-based spatially explicit simulation model, we compared scenarios where abiotic conditions shaped initial densities, interaction strengths, or both, of plant species with unique abiotic niches. We then partitioned the effect of the abiotic landscape on community patterns into components arising from variable density, variable interaction strengths, and their interaction. Even when plants responded to identical landscapes, variable density and variable interaction strengths led to different community patterns, and their combined effects were non-additive. Variable density promoted more spatial structure, while variable interaction strengths promoted higher local species richness. We highlight important implications these findings have in applied plant community ecology.

Contrasting short‐ and long‐term outcomes of pairwise interactions between caddisflies at a hydrologically heterogeneous range margin

Abstract Climate change is leading many species to shift their geographical ranges. Species undergoing these range shifts often are moving into areas with heterogeneous abiotic conditions. Additionally, these range‐shifting species will encounter resident species with whom they will compete for space and/or resources. However, the ways that these abiotic and biotic factors interact to influence the establishment and persistence of range‐shifting species has received little attention. Here, we conduct an in situ cage experiment examining how a local wetland hydroperiod gradient (i.e., temporary and semi‐permanent ponds) and competition with a resident caddisfly species, Asynarchus nigriculus, influences the survival of the range‐shifting species Limnephilus picturatus. We then use long‐term survey data of population densities of these two species to determine whether pairwise interactions observed in the cage experiment translated into long‐term dynamics. The cage experiment revealed that A. nigriculus had a strong, negative effect on the survival of the range‐shifting species L. picturatus, regardless of hydroperiod. However, we observed no relationship between the densities or occurrence of L. picturatus and A. nigriculus in long‐term data for either temporary or semi‐permanent ponds. Our results suggest that landscape‐level abiotic heterogeneity at range margins may not always be important for mediating antagonistic interactions between resident and range‐shifting species. However, although an interaction appears ecologically significant in short‐term field studies, broader context is needed to understand whether those types of interactions mediate species' distributions and abundance through time. At face‐value, our results from the field experiment and long‐term data analysis did not align. This suggests that other factors such as additional competitive or trophic interactions may be more important drivers behind the population dynamics of this range‐shifting species at its new upper‐elevational limit.

Floristic mosaics of the threatened Brazilian campo rupestre

The increase in rates of habitat loss requires an understanding of how biodiversity is distributed. Campo rupestre is an old, climatically buffered, and infertile landscape located in Brazil. Considered a biodiversity hotspot, the campo rupestre is mainly threatened by mining activity that requires a large operating area. Campo rupestre is known for its restricted distribution area and high abiotic heterogeneity, which modulates species coexistence and richness. To recognise the association between habitat type and plant communities, we propose to describe the floristic composition of herbaceous and shrub components in four habitats of the campo rupestre comprising quartzite and ferruginous substrate. We classified habitat types by the main surface soil features. In each habitat, we sampled ten 100-m2 plots to access information on the shrub and ten 1-m2 plots for the herbaceous component. Altogether we sampled 153 species, belonging to 38 families. The cluster analysis ordered by Sorensen metric indicates a clear distinction of species composition in the shrub component in the four habitats. However, the floristic composition of the herbaceous component was similar between the four habitats but showed a distinction when contrasting with the substrate type. Our results highlight the local taxonomic distinction between habitat types and substrates, indicating that the ecological distinction among substrate types of the campo rupestre cannot be overlooked in conservation and restoration actions.

Small herbivores and abiotic heterogeneity promote trait variation of a saltmarsh plant in local communities.

Intraspecific trait variation (ITV) enables plants to respond to global changes. However, causes for ITV, especially from biotic components such as herbivory, are not well understood. We explored whether small vertebrate herbivores (hares and geese) impact ITV of a dominant clonal plant (Elytrigia atherica) in local communities. Moreover, we looked at the relative importance of their direct (e.g., selective grazing) and indirect effects (altering genotypic richness/diversity and abiotic environment) on ITV. We used exclosures at two successional stages in a Dutch saltmarsh, where grazing pressure at the early successional stage was ca. 1.5 times higher than that of the intermediate successional stage. We measured key functional traits of E. atherica including height, aboveground biomass, flowering (flower or not), specific leaf area, and leaf dry matter content in local communities (1 m × 1 m plots) inside and outside the exclosures. We determined genotypic richness and diversity of each plant using molecular markers. We further measured abiotic variations in topography and clay thickness (a proxy for soil total nitrogen). Structural equation models revealed that small herbivores significantly promoted ITV in height and flowering at the early successional stage, while they marginally promoted ITV in height at the intermediate successional stage. Moreover, the direct effects of herbivores played a major role in promoting ITV. Small herbivores decreased genotypic diversity at the intermediate successional stage, but genotypic richness and diversity did not impact ITV. Small herbivores did not alter topographic variation and variation in clay thickness, but these variations increased ITV in all traits at the early successional stage. Small herbivores may not only impact trait means in plants as studies have shown but also their ITV.

Towards the evaluation of regional ecosystem integrity using NDVI, brightness temperature and surface heterogeneity

Maintaining ecological integrity is globally acknowledged as a strategic goal, yet there is no consensus on a practical and widely usable methodology to assess it. This study proposes a comprehensive approach to quantify regional ecosystem integrity based on FAIR data, obtained using satellite remote sensing and image analysis. Three variables are central to this approach: normalized difference vegetation index (NDVI), at-satellite brightness temperature (BT) and vegetation surface heterogeneity (HG), corresponding to ecosystem integrity indicators exergy capture, biotic water flows and abiotic heterogeneity. The indicators are assessed across the vegetation period and a representative Regional Index of Ecological Integrity (RIEI) is proposed to express the integrity of two case study areas and representative land use types. The proposed approach proved powerful in representing the anthropogenic and autopoietic gradient within study regions in high detail. Arable lands and urban areas ranked lowest, while dense forests and wetlands highest, agriculture being the most significant factor reducing regional integrity. Areas with conservation significance ranked either having the highest integrity, when dense vegetation was present, and mediocre or even low in case of e.g., sand dunes, marches and rock formations. Limitations of the method comprise: insufficient representation of biodiversity, sensitivity to cloud cover and demanding in-situ validation. The approach can be scaled from global to local level, adapted to various remote sensing techniques and complemented by a diversity of data (e.g., ecosystem services, geomorphological, climatic) to provide deeper understanding of landscape ecosystem integrity.

Determinants of zooplankton functional dissimilarity during years of El Niño and La Niña in floodplain shallow lakes

In floodplain lakes, precipitation events shape the environmental heterogeneity and the occurrence of species and functional traits. However, the importance of each biotic and abiotic factor on structuring communities might depend on the local environmental conditions and the identity of such communities. We investigated through Permutational analyses of variance and functional β-diversity components, the effects of neutral and extreme events of precipitation on environmental heterogeneity and distribution of zooplankton functional traits in floodplain lakes. We also examined through distance-based redundancy analysis and fourth-corner analysis, how different variables (physical–chemical, food availability, predation, and temporal dynamics) structure the distribution of zooplankton functional traits and which traits were related to these variables. We used data from six lakes of the Upper Parana River floodplain over 19 years. Environmental heterogeneity and β-diversity were higher during El Nino and lower during La Nina (extreme rainy and extremely dry season, respectively). Physical–chemical were the variables that most explained zooplankton β-diversity during all seasons and predation during both extreme seasons (La Nina and El Nino). We observed a set of multiple biotic and abiotic factors causing complex effects on zooplankton functional diversity. The homogenization of traits—observed during extreme dry seasons—can lead to losses in ecosystem functions and services if these events continue to be more frequent and intense. We reaffirm the importance of natural flood caused by the rainy seasons to maintain high biotic and abiotic heterogeneity and ecosystem processes.

Effect of rhizome exposure to contrasting abiotic conditions on the performance of the invasive macrophyte Hedychium coronarium J. Koenig (Zingiberaceae)

Although invasive species are often better competitors than native species, broad environmental tolerance may also drive invasion success. Tolerance to abiotic heterogeneity in riparian ecosystems tends to favour the establishment of alien clonal species, as well as their dispersion by vegetative fragments. Hedychium coronarium J. Koenig is a rhizomatous emergent macrophyte native to Asia and has invaded Neotropical riparian ecosystems. We assessed the effect of H. coronarium rhizome exposure to distinct abiotic conditions on ramet growth. We exposed rhizomes to different desiccation periods (1–90 days), temperatures (15, 25 and 35 °C), and light regimes (0, 12, 16 h) and then assessed the effect of each of these variables on subsequent clonal growth (aboveground biomass production per plant and per ramet, and number and height of ramets) under ambient conditions. While no rhizome survived desiccation periods longer than 30 days, ramet growth among surviving rhizomes was not affected by the period of desiccation. Biomass production per rhizome, ramet biomass, and ramet height were significantly lower at 35 °C than at 25 °C. Constant darkness increased rhizome survival, but decreased ramet growth. Although rhizome exposure to extremes of each abiotic variable may hinder the invasion success of H. coronarium, the subsequent aboveground biomass production of surviving rhizomes did not decrease strongly in response to any treatment. This resilience may contribute to successful establishment of H. coronarium after dispersal through rhizome fragments and to varying abiotic conditions.

Multiscale drivers of carabid beetle (Coleoptera: Carabidae) assemblages in small European woodlands

AbstractAimThe spatio‐temporal connectivity of forest patches in lowland agricultural landscapes and their age matter to explain current biodiversity patterns across regional as well as biogeographical extents, to the point that their effect exceeds the one of macroclimate for plant diversity in the understorey of temperate forests. Whether this remains true for other taxonomic groups is still largely unknown. Yet, this relative influence has important consequences for ecosystem functioning and the delivery of ecosystem services. Focusing on carabid beetle assemblages, we assessed the relative importance of macroclimatic, landscape and patch attributes in driving local species richness (α‐diversity) and species dissimilarity between patches (β‐diversity).LocationDeciduous forest patches in seven regions along a 2,100‐km‐long latitudinal gradient across the European temperate forest biome, from southern France to central Sweden.MethodsWe sampled 221 forest patches in two 5‐km × 5‐km landscape windows with contrasting management intensities. Carabid beetles were classified into four habitat‐preference guilds: forest‐specialist, forest‐generalist, eurytopic and open‐habitat species. We quantified the multi‐level environmental influence using mixed‐effects models and variation partitioning analysis.ResultsWe found that both α‐ and β‐diversity were primarily determined by macroclimate, acting as a large‐scale ecological filter on carabid assemblages among regions. Forest‐patch conditions, including biotic and abiotic heterogeneity as well as patch age (but not patch size), increased α‐diversity of forest species. Landscape management intensity weakly influenced α‐diversity of forest species, but increased the number of non‐forest species in forest patches. Beta diversity of non‐forest species increased with patch heterogeneity and decreased with landscape management intensity.Main conclusionsOur results highlight the leading role of broad macroclimatic gradients over local and landscape factors in determining the composition of local carabid communities, thereby shedding light on macroecological patterns of arthropod assemblages. This study emphasizes the urgent need for preserving ancient forest patches embedded in agricultural landscapes, even the small and weakly connected ones.

Influences of environmental heterogeneity on amphibian composition at breeding sites in a semiarid region of Mexico

Identification of factors that determine the behavior and diversity of species is crucial to our understanding of the ecology of species and communities. Satellite remote sensing (SRS) provides information relevant to the study of biodiversity and associated environmental traits at multiple spatial and temporal resolutions. Pond-breeding amphibians allow for comparative ecological analysis regarding the influence of environmental heterogeneity derived from SRS. Here, we characterize the influence of heterogeneity in abiotic (TWI, LST) and habitat-related (NDVI, NDWI) factors derived at fine spatial resolution on reproductive activity in the anuran community of the South Altiplano semiarid biogeographic province in Mexico. We used anuran reproductive data from seasonal and permanent water bodies and tested for the influence of abiotic and habitat heterogeneity with a spatiotemporal perspective using multivariate analysis, linear mixed-effects models (LMMs) and ecological niche models (ENMs). The results suggest that habitat heterogeneity best explains reproductive activity, whereas abiotic heterogeneity was second in importance. Implementation of ENMs using these abiotic and habitat heterogeneity variables allowed the detection of areas highly suitable for breeding across the study region. This research underlines the importance of environmental heterogeneity for predicting anuran breeding areas and their species compositions in the semiarid South Altiplano region of Mexico.

Mismatch managed? Phenological phase extension as a strategy to manage phenological asynchrony in plant–animal mutualisms

Species‐specific shifts in phenology (timing of periodic life cycle events) are occurring with climate change and are already disrupting interactions within and among trophic levels. Phenological phase duration (e.g. beginning to end of flowering) and complementarity (patterns of nonoverlap), and their responses to changing conditions, will be important determinants of species' adaptive capacity to these shifts. Evidence indicates that extension of phenological duration of mutualistic partners could buffer negative impacts that occur with phenological shifts. Therefore, we suggest that techniques to extend the length of phenological duration will contribute to management of systems experiencing phenological asynchrony. Techniques of phenological phase extension discussed include the role of abiotic heterogeneity, genetic and species diversity, and alteration of population timing. We explore these approaches with the goal of creating a framework to build adaptive capacity and address phenological asynchrony in plant–animal mutualisms under climate change.

Novel insights into how the mean and heterogeneity of abiotic conditions together shape forb species richness patterns in the Allegheny plateau ecoregion.

While plant community theory tends to emphasize the importance of abiotic heterogeneity along niche axes, much empirical work seeks to characterize the influence of the absolute magnitude of key abiotic variables on diversity. Both magnitude (as reflected, e.g., by a mean) and heterogeneity (variance) in abiotic conditions likely contribute to biodiversity patterns in plant communities, but given the large number of putative abiotic drivers and the fact that each may vary at different spatiotemporal scales, the challenge of linking observed biotic patterns with the underlying environment remains acute. Using monitoring data from a natural resource agency, we compared how well statistical models of the mean, heterogeneity, and both the mean and heterogeneity combined of 17 abiotic factor variables explained patterns of forb species richness in Northeast Ohio, USA. We performed our analyses at two spatial scales, repeated in spring and summer across four forest types. Although all models explained a great deal of the variance in species richness, models including both the mean and heterogeneity of different abiotic factors together outperformed models including either the mean or the heterogeneity of abiotic factors alone. Variability in forb species richness was mostly due to changes in mean calcium levels regardless of forest type. After accounting for forest type, we were able to attribute variation in forb species richness to changes in the heterogeneity of different abiotic factors as well. Our results suggest that multiple mechanisms act simultaneously according to different aspects of the abiotic environment to structure forb communities, and this underscores the importance of considering both the magnitude of and heterogeneity in multiple abiotic factors when looking for links between the abiotic environment and plant community patterns. Finally, we identify novel patterns across spatial scales, forest types, and seasons that can guide future research in this vein.OPEN RESEARCH BADGES This article has earned an Open Data Badge for making publicly available the digitally‐shareable data necessary to reproduce the reported results. The data is available at https://doi.org/10.5061/dryad.kp3cb17.

Growth and mortality patterns of the Neotropical bracken (Pteridium arachnoideum) and their response to shading in a savanna–riparian forest transition

Although certain clonal species are often overdominant in disturbed tropical ecosystems, it is often unclear how this success is related to their patterns of clonal growth and how they respond to abiotic heterogeneity. Here we describe ramet growth and survival in an overdominant Neotropical bracken fern (Pteridium arachnoideum) and assess how these patterns resemble congeneric species and are affected by canopy closure in a savanna–riparian forest transition in southeastern Brazil. We measured frond length from early emergence to senescence during two consecutive years in three clonal patches dominated by P. arachnoideum and associated the resulting growth pattern with the local canopy closure. Pteridium arachnoideum exhibited average frond length and growth rate higher than previously reported for this species and for congeneric species. Frond mortality was generally high shortly after emergence from the ground, but was also much higher in one study site due to ant herbivory. Fronds of P. arachnoideum were higher, showed petiole elongation and higher mortality rate under high canopy closure, suggesting shading avoidance, in contrast to the shade tolerance reported for Pteridium aquilinum. Although our findings indicate that this species is unlikely to represent a threat to the biodiversity of undisturbed Brazilian savanna–riparian forest transitions with continuous canopy, they also suggest that introduction of fast growing tree species with dense canopy may accelerate the restoration of more disturbed and degraded sites.

Abiotic heterogeneity underlies trait‐based competition and assembly

Abstract The fitness of individual species depends on their ability to persist and establish at low densities, just as the diversity of ecological communities depends on the establishment and persistence of low‐density, “invader” species. Theory predicts that abiotic conditions and the competitive make‐up of resident communities jointly shape invader fitness, limiting the phenotypic identity of successful invaders. We use an invasion experiment to ask how competitive traits of 20 introduced plant species alter their absolute fitness in fragments that differ in size, abiotic conditions, and traits of the resident community. We show that abiotic conditions interact with both invader traits and resident functional diversity to determine invader survival. Optimal invader traits depended on the soil characteristics, while greater resident trait diversity lowered invader fitness and had especially strong effects in low‐resource environments. Unlike other abiotic conditions, fragment size had consistent effects irrespective of invader identity, decreasing survival in larger fragments. Synthesis. Our results illustrate how the abiotic environment mediates the effects of resident and invader traits on establishment, creating fitness landscapes that structure local diversity and the functional identities of successful species.