Fire sparks upslope range shifts of North Cascades plant species

As ongoing climate change drives suitable habitats to higher elevations, species ranges are predicted to follow. However, observed range shifts have been surprisingly variable, with most species differing in rates of upward shift and others failing to shift at all. Disturbances such as fires could play an important role in accelerating range shifts by facilitating recruitment in newly suitable habitats (leading edges) and removing adults from areas no longer suited for regeneration (trailing edges). To date, empirical evidence that fires interact with climate change to mediate elevational range shifts is scarce. Resurveying historical plots in areas that experienced climate change and fire disturbance between surveys provides an exciting opportunity to fill this gap. To investigate whether species have tended to shift upslope and if shifts depend on fires, we resurveyed historical vegetation plots in North Cascades National Park, Washington, USA, an area that has experienced warming, drying, and multiple fires since the original surveys in 1983. We quantified range shifts by synthesizing across two lines of evidence: (1) displacement at range edges and the median elevation of species occurrences, and (2) support for the inclusion of interactions among time, fire and elevation in models of species presence with elevation. Among species that experienced fire since the original survey, a plurality expanded into new habitats at their upper edge. In contrast, a plurality of species not experiencing fire showed no evidence of shifts, with the remainder exhibiting responses that were variable in magnitude and direction. Our results suggest that fires can facilitate recruitment at leading edges, while species in areas free of disturbance are more likely to experience stasis.

No species loss, but pronounced species turnover in grasslands in the Northern Alps over 25 years

The abandonment of marginally productive habitats and the intensification of land use on productive sites have caused transformative changes in vegetation composition in Central Europe. In this study, after 25 years we resurveyed a total of 145 grassland relevés from the mid-1990s in a grassland-dominated valley of the Northern Alps of Upper Austria. We studied changes in richness and composition, and related these to underlying drivers. We found that the average species number in plots increased from 46 in the first survey period to 49 in the second one. Median species richness across sites significantly increased from 1995 to 2020 for Festuco-Brometea (55-61 species) and Galio-Urticetea (24-32 species), but did not show any significant change for the other classes. Further, we recorded substantial species turnover, with winners consisting mostly of species that prefer nutrient-rich sites, while losers were predominantly species of nutrient-poor sites. In particular, using Ellenberg Indicator Values for calculating community indices, we found an indication for ongoing eutrophication in vegetation types of nutrient-poor vegetation classes (Festuco-Brometea and Calluno-Ulicetea), and in wet habitats (Scheuchzerio-Caricetea fuscae). Community indices of wet habitats also showed clear signs of becoming more mesic. Thermophilization of community indices was evident across several vegetation classes. Further, alien species that were very rare in the mid-1990s became more abundant in the resurveyed plots, although the level of invasion is still low. Finally, community values for nutrients of plots that are located in a protected area that has been established in 2014 did not increase significantly, while this was the case in plots outside the protected area, indicating that the management of the protected area has positive effects in halting eutrophication. We conclude that despite overall species richness changing only moderately between both surveys, substantial changes in community composition toward more nitrophilic and thermophilic conditions occurred.

Different temporal trends in vascular plant and bryophyte communities along elevational gradients over four decades

Despite many studies showing biodiversity responses to warming, the generality of such responses across taxonomic groups remains unclear. Very few studies have tested for evidence of bryophyte community responses to warming, even though bryophytes are major contributors to diversity and functioning in many ecosystems. Here, we report an empirical study comparing long‐term change in bryophyte and vascular plant communities in two sites with contrasting long‐term warming trends, using “legacy” botanical records as a baseline for comparison with contemporary resurveys. We hypothesized that ecological changes would be greater in sites with a stronger warming trend and that vascular plant communities, with narrower climatic niches, would be more sensitive than bryophyte communities to climate warming. For each taxonomic group in each site, we quantified the magnitude of changes in species' distributions along the elevation gradient, species richness, and community composition. We found contrasted temporal changes in bryophyte vs. vascular plant communities, which only partially supported the warming hypothesis. In the area with a stronger warming trend, we found a significant increase in local diversity and dissimilarity (β‐diversity) for vascular plants, but not for bryophytes. Presence–absence data did not provide sufficient power to detect elevational shifts in species distributions. The patterns observed for bryophytes are in accordance with recent literature showing that local diversity can remain unchanged despite strong changes in composition. Regardless of whether one taxon is systematically more or less sensitive to environmental change than another, our results suggest that vascular plants cannot be used as a surrogate for bryophytes in terms of predicting the nature and magnitude of responses to warming. Thus, to assess overall biodiversity responses to global change, abundance data from different taxonomic groups and different community properties need to be synthesized.

Directional turnover towards larger-ranged plants over time and across habitats

Species turnover is ubiquitous. However, it remains unknown whether certain types of species are consistently gained or lost across different habitats. Here, we analysed the trajectories of 1827 plant species over time intervals of up to 78 years at 141 sites across mountain summits, forests, and lowland grasslands in Europe. We found, albeit with relatively small effect sizes, displacements of smaller- by larger-ranged species across habitats. Communities shifted in parallel towards more nutrient-demanding species, with species from nutrient-rich habitats having larger ranges. Because these species are typically strong competitors, declines of smaller-ranged species could reflect not only abiotic drivers of global change, but also biotic pressure from increased competition. The ubiquitous component of turnover based on species range size we found here may partially reconcile findings of no net loss in local diversity with global species loss, and link community-scale turnover to macroecological processes such as biotic homogenisation.

Climate-driven habitat change causes evolution in Threespine Stickleback

Climate change can shape evolution directly by altering abiotic conditions or indirectly by modifying habitats, yet few studies have investigated the effects of climate-driven habitat change on contemporary evolution. We resampled populations of Threespine Stickleback (Gasterosteus aculeatus) along a latitudinal gradient in California bar-built estuaries to examine their evolution in response to changing climate and habitat. We took advantage of the strong association between stickleback lateral plate phenotypes and Ectodysplasin A (Eda) genotypes to infer changes in allele frequencies over time. Our results show that over time the frequency of low-plated alleles has generally increased and heterozygosity has decreased. Latitudinal patterns in stickleback plate phenotypes suggest that evolution at Eda is a response to climate-driven habitat transformation rather than a direct consequence of climate. As climate change has reduced precipitation and increased temperature and drought, bar-built estuaries have transitioned from lotic (flowing-water) to lentic (still-water) habitats, where the low-plated allele is favoured. The low-plated allele has achieved fixation at the driest, hottest southernmost sites, a trend that is progressing northward with climate change. Climate-driven habitat change is therefore causing a reduction in genetic variation that may hinder future adaptation for populations facing multiple threats.

Four decades of plant community change along a continental gradient of warming

Many studies of individual sites have revealed biotic changes consistent with climate warming (e.g., upward elevational distribution shifts), but our understanding of the tremendous variation among studies in the magnitude of such biotic changes is minimal. In this study, we resurveyed forest vegetation plots 40 years after the initial surveys in three protected areas along a west-to-east gradient of increasingly steep recent warming trends in eastern Canada (Québec). Consistent with the hypothesis that climate warming has been an important driver of vegetation change, we found an increasing magnitude of changes in species richness and composition from west to east among the three parks. For the two mountainous parks, we found no significant changes in elevational species' distributions in the easternmost park (raw mean = +11.4 m at Forillon Park) where warming has been minimal, and significant upward distribution shifts in the centrally located park (+38.9 m at Mont-Mégantic), where the recent warming trend has been marked. Community Temperature Indices (CTI), reflecting the average affinities of locally co-occurring species to temperature conditions across their geographic ranges ("Species Temperature Indices"), did not change over time as predicted. However, close examination of the underpinnings of CTI values suggested a high sensitivity to uncertainty in individual species' temperature indices, and so a potentially limited responsiveness to warming. Overall, by testing a priori predictions concerning variation among parks in the direction and magnitude of vegetation changes, we have provided stronger evidence for a link between climate warming and biotic responses than otherwise possible and provided a potential explanation for large variation among studies in warming-related biotic changes.

A century of climate and land-use change cause species turnover without loss of beta diversity in California's Central Valley

Climate and land-use changes are thought to be the greatest threats to biodiversity, but few studies have directly measured their simultaneous impacts on species distributions. We used a unique historic resource-early 20th-century bird surveys conducted by Joseph Grinnell and colleagues-paired with contemporary resurveys a century later to examine changes in bird distributions in California's Central Valley, one of the most intensively modified agricultural zones in the world and a region of heterogeneous climate change. We analyzed species- and community-level occupancy using multispecies occupancy models that explicitly accounted for imperfect detection probability, and developed a novel, simulation-based method to compare the relative influences of climate and land-use covariates on site-level species richness and beta diversity (measured by Jaccard similarity). Surprisingly, we show that mean occupancy, species richness and between-site similarity have remained remarkably stable over the past century. Stability in community-level metrics masked substantial changes in species composition; occupancy declines of some species were equally matched by increases in others, predominantly species with generalist or human-associated habitat preferences. Bird occupancy, richness and diversity within each era were driven most strongly by water availability (precipitation and percent water cover), indicating that both climate and land-use are important drivers of species distributions. Water availability had much stronger effects than temperature, urbanization and agricultural cover, which are typically thought to drive biodiversity decline.

Multiple environmental changes drive forest floor vegetation in a temperate mountain forest

Human-induced changes of the environment and their possible impacts on temperate forest understory plant communities have been examined in many studies. However, the relative contribution of individual environmental factors to these changes in the herb layer is still unclear. In this study, we used vegetation survey data covering a time period of 21 years and collected from 143 permanent plots in the Northern Limestone Alps, Austria. Data on soil chemistry (49 plots), light condition (51 plots), soil temperature and moisture (four and six plots), disturbance (all plots), climate (one station in a clearing area), and airborne sulfur (S) and nitrogen (N) deposition (two forest stands) were available for analyses. We used these data together with plot mean Ellenberg indicator values in a path analysis to attribute their relative contributions to observed vegetation changes. Our analysis reveals a strong directional shift of the forest understory plant community. We found strong evidence for a recovery of the ground-layer vegetation from acidification as response to decreased S deposition. We did not observe a community response to atmospheric N deposition, but we found a response to altered climatic conditions (thermophilization and drying). The path analysis revealed that changes in the light regime, which were related to small-scale disturbances, had most influence on herb layer community shifts. Thermophilization and drying were identified as drivers of understory community changes independent of disturbance events.

Resurvey of symptomatics of the Jaipur district population and suggestion for alternative diagnostic criteria of asthma for epidemiological surveys

INTRODUCTION

The prevalence of asthma in Jaipur district of Rajasthan was reported as 0.96% in an earlier survey. It was far below the national average of 2.38%. It was reasoned then that this could be due to under diagnosis of asthma in the Jaipur population.

MATERIAL AND METHODS

A resurvey of the symptomatics, not diagnosed as asthma at time of the original survey was, therefore, undertaken. The resurvey data were analysed and those who now fulfilled the twin criteria for diagnosis of asthma, as used in the original survey, were diagnosed as having asthma. The original data of these newly diagnosed asthma patients were reanalyzed in search for an alternative diagnostic criterion.

RESULTS

Of the 382 symptomatics, 344 (90%) could be resurveyed and of them, 85 now fulfilled the twin diagnostic criteria for asthma. The reanalysis of the original survey data of these patients revealed that presence of shortness of breath (SOB) had the highest sensitivity, the presence of allergic symptoms in self or the family had the highest specificity and the presence of wheezing had the highest odds ratio (OR) for diagnosing asthma. Further, the OR for diagnosing asthma increased further and was highest with the presence of SOB and 2 additional symptoms. With the use of the "symptom criteria" for diagnosis of asthma i.e. the presence of SOB with 2 additional symptoms, it would have been possible to diagnose majority of the missed cases at the time of the original survey itself.

CONCLUSIONS

Based on this study data it can be concluded that (a) the twin criteria for diagnosing asthma as used in earlier surveys led to under diagnosis of asthma and (b) the use of symptom criteria alone effectively checks the problem of under diagnosis of asthma. The symptom criteria are being suggested as an alternative method for use in future epidemiological surveys on asthma.

Elevational differences in developmental plasticity determine phenological responses of grasshoppers to recent climate warming

Annual species may increase reproduction by increasing adult body size through extended development, but risk being unable to complete development in seasonally limited environments. Synthetic reviews indicate that most, but not all, species have responded to recent climate warming by advancing the seasonal timing of adult emergence or reproduction. Here, we show that 50 years of climate change have delayed development in high-elevation, season-limited grasshopper populations, but advanced development in populations at lower elevations. Developmental delays are most pronounced for early-season species, which might benefit most from delaying development when released from seasonal time constraints. Rearing experiments confirm that population, elevation and temperature interact to determine development time. Population differences in developmental plasticity may account for variability in phenological shifts among adults. An integrated consideration of the full life cycle that considers local adaptation and plasticity may be essential for understanding and predicting responses to climate change.

Non-random extinctions dominate plant community changes in abandoned coppices

1. The plant community structure of European lowland forests has changed dramatically in the 20th century, leading to biodiversity decline at various spatial scales. However, due to methodological difficulties associated with simultaneous changes in species diversity and composition, ecological processes behind the changes are still poorly understood. 2. We analysed temporal changes in forest plant community after the mid-20th century abandonment of coppicing in a typical Central European forest, which had been managed as coppice for centuries. We used 122 semi-permanent plots first surveyed in the 1950s shortly after the last coppicing and again in the 2000s after half a century of natural succession. We used a novel Temporal Nestedness Analysis to disentangle the immigration and extinction processes underlying temporal changes in community structure and tested whether species gains and losses were ecologically random. 3. The studied vegetation has shifted from the species-rich assemblages of a relatively open and low-nutrient forest towards the impoverished flora of a closed-canopy forest dominated by a few shade-adapted species. The significant reduction of beta diversity, i.e. compositional heterogeneity among plots, indicated taxonomic homogenization of the forest understorey. Temporal species turnover was only a minor component of the community change and recent assemblages are nested subsets of the former ones. Ecologically non-random extinctions dominated these changes. Light-demanding species with a persistent seed-bank were the most prone to extinction, while species with high specific leaf area substantially increased in frequency. 4. Synthesis and applications. The dominant process after the abandonment of coppicing was the ecologically non-random extinction of light-demanding species leading to an impoverished, temporally nested plant community structure. This development is typical for many abandoned lowland coppice forests and poses a significant threat to forest biodiversity in Europe. If forestry and conservation policies continue to prefer closed-canopy stands, many endangered species are likely to pay their extinction debts. To restore declining or even locally extinct species, canopy opening in abandoned coppices is urgently needed.