Shifts In Plant Species Research Articles

Plant Species' Capacity for Range Shifts at the Habitat and Geographic Scales: A Trade-Off-Based Framework.

Climate change is causing rapid shifts in the abiotic and biotic environmental conditions experienced by plant populations, but we lack generalizable frameworks for predicting the consequences for species. These changes may cause individuals to become poorly matched to their environments, potentially inducing shifts in the distributions of populations and altering species' habitat and geographic ranges. We present a trade-off-based framework for understanding and predicting whether plant species may undergo range shifts, based on ecological strategies defined by functional trait variation. We define a species' capacity for undergoing range shifts as the product of its colonization ability and the ability to express a phenotype well-suited to the environment across life stages (phenotype-environment matching), which are both strongly influenced by a species' ecological strategy and unavoidable trade-offs in function. While numerous strategies may be successful in an environment, severe phenotype-environment mismatches result in habitat filtering: propagules reach a site but cannot establish there. Operating within individuals and populations, these processes will affect species' habitat ranges at small scales, and aggregated across populations, will determine whether species track climatic changes and undergo geographic range shifts. This trade-off-based framework can provide a conceptual basis for species distribution models that are generalizable across plant species, aiding in the prediction of shifts in plant species' ranges in response to climate change.

Species shifts induce soil organic matter priming and changes in microbial communities

Invasion of plant species with functional traits that influences the rhizosphere can have significant effects on soil organic matter (SOM) dynamics if the invasive species stimulates soil microbial communities with, for example, an enhanced supply of labile carbon and oxygen. We evaluated these effects along a Phragmites invasion chronosequence spanning over 40 years. Using a δ13C and δ15N enriched substrate, we separated SOM-derived and substrate-derived carbon (C) and nitrogen (N) mineralization in surface (top 15 cm), shallow (30–45 cm), and deep (65–80 cm) soils collected from established, newly invaded, and native plant communities. We found all soils were susceptible to SOM priming, but priming profiles differed between vegetation communities, being highest at the surface in native assemblage soils, whereas highest at depth under invasive plants. Changes in functional microbial community composition at depth in Phragmites soils, evidenced by an increase in relative fungal laccase abundance, explained the SOM priming in these deep invaded soils. Our results show that invasive Phragmites maintains a microbial community at depth able to degrade SOM faster than that under native vegetation, evidencing that plant species shifts can fundamentally change soil biogeochemistry, altering element cycling and decreasing SOM residence time. Furthermore, our experimental design allowed to quantify real-time SOM-C and SOM-N gross mineralization, resulting in a new model relating C and N mineralization in these wetland soils and providing new insights on how SOM decomposition impacts N availability and cycling across wetland N pools.

Nitrogen Deposition Shifts Grassland Communities Through Directly Increasing Dominance of Graminoids: A 3-Year Case Study From the Qinghai-Tibetan Plateau.

Nitrogen (N) deposition has been increasing for decades and has profoundly influenced the structure and function of grassland ecosystems in many regions of the world. However, the impact of N deposition on alpine grasslands is less well documented. We conducted a 3-year field experiment to determine the effects of N deposition on plant species richness, composition, and community productivity in an alpine meadow of the Qinghai-Tibetan Plateau of China. We found that 3 years of N deposition had a profound effect on these plant community parameters. Increasing N rates increased the dominance of graminoids and reduced the presence of non-graminoids. Species richness was inversely associated with aboveground biomass. The shift in plant species and functional group composition was largely responsible for the increase in productivity associated with N deposition. Climatic factors also interacted with N addition to influence productivity. Our findings suggest that short-term N deposition could increase the productivity of alpine meadows through shifts in composition toward a graminoid-dominated community. Longer-term studies are needed to determine if shifts in composition and increased productivity will be maintained. Future work must also evaluate whether decreasing plant diversity will impair the long-term stability and function of sensitive alpine grasslands.

An empirical method to account for climatic adaptation in plant phenology models.

Phenological shifts in plant species are one of the most conspicuous signs of climate change impact on the biosphere. Modeling phenological variations of plant species over broad regions is challenging because of the varied climatic requirements of geographic populations due to local adaptation. In this study, we developed an empirical method to calibrate phenological models of temperate trees using latitude as a predictor to account for local adaptation of populations to a N-S temperature gradient. Fourteen widely distributed tree species in the eastern U.S.A. were investigated using data from the USA-National Phenology Network. We implemented the method in a basic thermal time bud break model to introduce the algorithm of the method and test its effectiveness. For each species, dates of breaking leaf buds were first predicted using a traditional non-spatial model and then with a spatial model that has the critical thermal forcing requirements calibrated for different populations at varied latitudes. As anticipated, non-spatial model predictions that assumed a uniform forcing requirement across latitudes showed consistent and systematic biases at both higher (overestimation-predictions being later) and lower (underestimation-predictions being earlier) latitudes. Spatial models that have been calibrated using our method removed the geographic biases and yielded latitudinal gradients that more closely matched those of the observations. The spatial models also reduced the overall prediction errors from an average root mean square error (RMSE) of 32.2 days to 20.4 days for the training dataset and an average root mean square error for prediction (RMSEP) of 32.2 days to 19.9 days for the testing dataset. This paper is focused on introducing the new calibration method as a preparatory step toward developing operational models that may potentially predict large-scale and range-wide phenological responses of various plant species to climatic changes with improved local accuracy.

Drought in maternal environment boosts offspring performance in a subordinate annual grass

Drought can induce shifts in plant species or functional group abundances, which may favor coexisting subordinate species at the expense of previous dominants. Within-generation and transgenerational phenotypic plasticity can be important mechanisms to shape species responses to drought. Although a handful of studies have already investigated transgenerational plasticity in the context of drought, they provided variable results, and usually focused on species that currently dominate communities.We performed pot experiments with Secale sylvestre, a typical subordinate species in semiarid grasslands of Central Hungary. We tested if this annual grass shows reduced growth or reproduction in response to drought, and whether drought in the maternal environment affects offspring performance.For both maternal and offspring generations, plant height, shoot biomass, flowering onset, and seed number showed no within-generation plasticity in response to drought, and drought only decreased the seed mass of mother plants. In contrast, we found strong transgenerational effects on the overall performance of progenies, which changed with offspring age. At an early life stage, shoots were shorter for the offspring of drought-treated mothers than for the progenies of control mothers. This difference turned in the opposite direction later, and tiller number was also greater for the offspring of drought-treated mothers. Furthermore, the offspring of drought-treated mothers had over two-times higher adult shoot biomass and seed production compared to the offspring of control mothers. These beneficial transgenerational effects may help S. sylvestre to gain dominance in sand grasslands following dry years that decrease the abundance of perennial grasses, a vegetation change often observed in these grasslands after droughts.Our study provides the first evidence for positive transgenerational plasticity in response to drought for a subordinate species, which may be adaptive when the suppression of dominant species in the offspring environment is predictable from drought in the maternal environment.

Bioclimatic modeling of potential vegetation types as an alternative to species distribution models for projecting plant species shifts under changing climates

Land managers need new tools for planning novel futures due to climate change. Species distribution modeling (SDM) has been used extensively to predict future distributions of species under different climates, but their map products are often too coarse for fine-scale operational use. In this study we developed a flexible, efficient, and robust method for mapping current and future distributions and abundances of vegetation species and communities at the fine spatial resolutions that are germane to land management. First, we mapped Potential Vegetation Types (PVTs) using conventional statistical modeling techniques (Random Forests) that used bioclimatic ecosystem process and climate variables as predictors. We obtained over 50% accuracy across 13 mapped PVTs for our study area. We then applied future climate projections as climate input to the Random Forest model to generate future PVT maps, and used field data describing the occurrence of tree and non-tree species in each PVT category to model and map species distribution for current and future climate. These maps were then compared to two previous SDM mapping efforts with over 80% agreement and equivalent accuracy. Because PVTs represent the biophysical potential of the landscape to support vegetation communities as opposed to the vegetation that currently exists, they can be readily linked to climate forecasts and correlated with other, climate-sensitive ecological processes significant in land management, such as fire regimes and site productivity.

Postglacial change of the floristic diversity gradient in Europe

Climate warming is expected to cause a poleward spread of species, resulting in increased richness at mid to high latitudes and weakening the latitudinal diversity gradient. We used pollen data to test if such a change in the latitudinal diversity gradient occurred during the last major poleward shift of plant species in Europe following the end of the last glacial period. In contrast to expectations, the slope of the gradient strengthened during the Holocene. The increase in temperatures around 10 ka ago reduced diversity at mid to high latitude sites due to the gradual closure of forests. Deforestation and the introduction of agriculture during the last 5 ky had a greater impact on richness in central Europe than the earlier climate warming. These results do not support the current view that global warming alone will lead to a loss in biodiversity, and demonstrate that non-climatic human impacts on the latitudinal diversity gradient is of a greater magnitude than climate change.

Potential Distribution Shifts of Plant Species under Climate Change in Changbai Mountains, China

Shifts in alpine tundra plant species have important consequences for biodiversity and ecosystem services. However, recent research on upward species shifts have focused mainly on polar and high-latitude regions and it therefore remains unclear whether such vegetation change trends also are applicable to the alpine tundra at the southern edges of alpine tundra species distribution. This study evaluated an alpine tundra region within the Changbai Mountains, China, that is part of the southernmost alpine tundra in eastern Eurasia. We investigated plant species shifts in alpine tundra within the Changbai Mountains over the last three decades (1984–2015) by comparing contemporary survey results with historical ones and evaluated potential changes in the distribution of dwarf shrub and herbaceous species over the next three decades (2016–2045) using a combination of observations and simulations. The results of this study revealed that the encroachment of herbaceous plants had altered tundra vegetation to a significant extent over the last three decades, especially within low and middle alpine tundra regions in Changbai Mountains, China. The herbaceous species would continue shifting upward and expanding while their dwarf shrub counterparts would continue shifting upward and shrinking over the next three decades under the RCP 4.5 and RCP 8.5 scenarios. The upward shifts of plant species would not keep up with the rate of climate warming under the RCP 8.5 scenarios. The dominant plant tundra species may transform from dwarf shrubs to herbaceous varieties. The results of this study provide a scientific basis for biodiversity protection under climate change and a reference data set for additional research on alpine vegetation dynamics.

Within-generation and transgenerational plasticity in growth and regeneration of a subordinate annual grass in a rainfall experiment.

Precipitation changes may induce shifts in plant species or life form dominance in ecosystems, making some previously subordinate species abundant. The plasticity of certain plant functional traits of these expanding subordinate species may be one possible mechanism behind their success. In this study, we tested if the subordinate winter annual grass Secale sylvestre shows plasticity in growth and reproduction in response to altered environment associated with field-scale rainfall manipulations (severe drought, moderate drought, and watering) in a semiarid grassland, and whether the maternal environment influences offspring germination or growth in a subsequent pot experiment. Compared to control plots, S. sylvestre plants grew 38% taller, and produced 32% more seeds in severe drought plots, while plants in watered plots were 17% shorter, and had 22% less seeds. Seed mass was greatest in severe drought plots. Plants growing in drought plots had offspring with enhanced juvenile shoot growth compared to the progeny whose mother plants grew in watered plots. These responses are most likely explained by the decreased cover of previously dominant perennial grasses in severe drought plots, which resulted in wetter soil compared to control and watered plots during the peak growth of S. sylvestre. We conclude that the plasticity of this subordinate annual species in response to changing environment may help to gain dominance with recurring droughts that suppress perennial grasses. Our results highlight that exploring both within-generation and transgenerational plasticity of subordinate species may lead to a better prediction of changes in plant species dominance under climate change.

Winter soil temperature dependence of alpine plant distribution: Implications for anticipating vegetation changes under a warming climate

The topographical heterogeneity of mountain landscapes and the associated species turnover over short distances should prompt us to examine the relationships between climate and mountain plant distribution at a much finer scale than is commonly done. Here, I focused on the root zone temperature experienced by low-stature perennial-dominated plant communities of temperate mountains, which are seasonally covered by snow. Based on the analysis of multi-annual recordings of ground temperatures across a broad spectrum of plant communities, I propose a habitat template using Growing Degree Days (GDD) and Freezing Degree Days (FDD). These two indices summarize soil thermal conditions experienced during the favorable and the unfavorable period for growth. This heuristic framework allows refining our working hypotheses on the range shifts of mountain plants in response to recent and future climate change. Regional trends in climate variables controlling GDD and FDD indicate that the combination of earlier snow melt-out and higher summer temperatures have led to an overall increase in GDD over the last decades. However the persistence of cold episodes in spring and in fall along with the shorter snow coverage suggest that the positive effect of an extended growing season might be counteracted by the detrimental effects of increasing FDD. I thus hypothesize (i) a local-scale, downward shift of plant species along mesotopographical gradients, with marked species infilling in sparsely vegetated, long-lasting snow patches that contain vacant niches and (ii) a watershed-scale upward shift of subalpine species inhabiting south-exposed grasslands and able to cope with moderate FDD. This perspective challenges the simplistic view of an overall range shift of mountain plants along elevational gradients and calls for the improvement of models of snow cover dynamics and root zone temperature to draw up realistic scenarios of mountain vegetation changes under a warmer climate.

Exploring linked ecological and cultural tipping points in Mongolia

Abstract We review evidence of Holocene climate, vegetation, and cultural changes in Mongolia and critically examine evidence that Mongolia’s steppes are at the brink of ecological and cultural tipping points in the Anthropocene. Until 5,000 YBP there is no evidence of lasting human influences on ecosystems, but after this time, changes in vegetation and soil physical properties signal domestic livestock grazing impacts on steppe ecosystems. Contemporary (1991–2015) literature and region by region analysis of climate, livestock, remote-sensing and human population data reveal two potential tipping points. Temperatures warmed across the 5 regions. Since 1991, livestock densities and forage use increased in most regions, the spatial distribution of grazing pressure is more heterogeneous, and variability increased in stocking densities, forage use and forage production in all or most regions. Substantial plant species shifts and losses occurred in the mountain and forest steppe regions. Although a large proportion of Mongolia’s rangelands are altered from their ecological potential, few have crossed an irreversible threshold of ecological change. Rangelands in Mongolia’s Khangai, northern and central regions may be approaching an ecological tipping point if grazing pressure is not reduced. After 1991, herder populations initially rose and then decreased significantly across most regions. If demographic and social trends contribute to loss of herding knowledge and identity, a cultural tipping point could occur. We describe four potential future scenarios that could unfold if these tipping points are reached, hypothesize feedbacks between ecological and cultural thresholds, and discuss implications for policy and management.

Snowbeds are more affected than other subalpine-alpine plant communities by climate change in the Swiss Alps.

While the upward shift of plant species has been observed on many alpine and nival summits, the reaction of the subalpine and lower alpine plant communities to the current warming and lower snow precipitation has been little investigated so far. To this aim, 63 old, exhaustive plant inventories, distributed along a subalpine–alpine elevation gradient of the Swiss Alps and covering different plant community types (acidic and calcareous grasslands; windy ridges; snowbeds), were revisited after 25–50 years. Old and recent inventories were compared in terms of species diversity with Simpson diversity and Bray–Curtis dissimilarity indices, and in terms of community composition with principal component analysis. Changes in ecological conditions were inferred from the ecological indicator values. The alpha‐diversity increased in every plant community, likely because of the arrival of new species. As observed on mountain summits, the new species led to a homogenization of community compositions. The grasslands were quite stable in terms of species composition, whatever the bedrock type. Indeed, the newly arrived species were part of the typical species pool of the colonized community. In contrast, snowbed communities showed pronounced vegetation changes and a clear shift toward dryer conditions and shorter snow cover, evidenced by their colonization by species from surrounding grasslands. Longer growing seasons allow alpine grassland species, which are taller and hence more competitive, to colonize the snowbeds. This study showed that subalpine–alpine plant communities reacted differently to the ongoing climate changes. Lower snow/rain ratio and longer growing seasons seem to have a higher impact than warming, at least on plant communities dependent on long snow cover. Consequently, they are the most vulnerable to climate change and their persistence in the near future is seriously threatened. Subalpine and alpine grasslands are more stable, and, until now, they do not seem to be affected by a warmer climate.

Effects of precipitation regime and soil nitrogen on leaf traits in seasonally dry tropical forests of the Yucatan Peninsula, Mexico.

Leaf traits are closely associated with nutrient use by plants and can be utilized as a proxy for nutrient cycling processes. However, open questions remain, in particular regarding the variability of leaf traits within and across seasonally dry tropical forests. To address this, we considered six leaf traits (specific area, thickness, dry matter content, N content, P content and natural abundance (15)N) of four co-occurring tree species (two that are not associated with N2-fixing bacteria and two that are associated with N2-fixing bacteria) and net N mineralization rates and inorganic N concentrations along a precipitation gradient (537-1036 mm per year) in the Yucatan Peninsula, Mexico. Specifically we sought to test the hypothesis that leaf traits of dominant plant species shift along a precipitation gradient, but are affected by soil N cycling. Although variation among different species within each site explains some leaf trait variation, there is also a high level of variability across sites, suggesting that factors other than precipitation regime more strongly influence leaf traits. Principal component analyses indicated that across sites and tree species, covariation in leaf traits is an indicator of soil N availability. Patterns of natural abundance (15)N in foliage and foliage minus soil suggest that variation in precipitation regime drives a shift in plant N acquisition and the openness of the N cycle. Overall, our study shows that both plant species and site are important determinants of leaf traits, and that the leaf trait spectrum is correlated with soil N cycling.

Recent shifts in plant species suggest opposing land-use changes in alpine pastures

Land abandonment and intensification of management have been suggested as major drivers of biodiversity change in subalpine and alpine grasslands, but the relative importance of these concomitant trends has not been extensively studied. Here, we use plant indicator values to infer patterns of change in the management intensity of summer pastures. Occurrence data of vascular plants from 192 plots surveyed in the Swiss Biodiversity Monitoring BDM programme were used to analyse changes in five species-based indicator values that express the management intensity of sites. Each plot was surveyed twice between 2002 and 2011 with a time span of 5 years between surveys. We looked for an overall trend in management intensity and examined whether a supposed change of management intensity depends on site conditions. In addition, we tested whether a change in indicator values for management intensity accompanies a change in species richness. Over the whole study area, there was no overall change in mean indicator values. However, we found weak but significant relations between changes in mean indicator values and accessibility of the sites. According to plant indicator values, intensification of management takes place at well-accessible and lower-elevation sites, whereas remote sites and sites at higher elevation tend to show a decrease in management intensity. Sites where indicators suggested intensified management showed a decrease of both total species richness and richness of target species relevant for conservation. On the other hand, a supposed decrease in land-use intensity led to an increase in species richness within the surveyed time period. This study confirms that moderate management intensity of summer pastures will best maintain the plant diversity of alpine summer pastures. Because the surveyed plots stem from a rigorously standardized regular-grid sampling, we attribute high reliability and generality to our findings.

Ground cover species selection to manage common ragweed (Ambrosia artemisiifolia L.) in roadside edge of highway

In southern Quebec, Canada, Trifolium species are commonly used as supplement ground cover along roadside of major roads to assist turf recruitment. They often fail to establish particularly near roadside edges. The noxious weed, Ambrosia artemisiifolia, exploits the empty niches. Based on an assumption that heavy metal stress mainly drives plant species shift, we conducted a field experiment to test the emergence of four species near roadside edges along a metal gradient. The test species included a clover ground cover (Trifolium arvense), two candidate ground covers (Lotus corniculatus and Coronilla varia), and the weed (A. artemisiifolia). Two hundred wet-cold stratified seeds of each species were sown in plots (20 × 30 cm), assigned separately for one of four species treatments, replicated three times. We measured final emergence percentage and soil metal contents and analyzed their correlations. T. arvense emergence was negatively correlated with Zn, Pb, and Cu. In contrast, A. artemisiifolia emergence was positively correlated with Zn, Pb, and Cu. The experiment supports the hypothesis that A. artemisiifolia colonization along roadside edges may be attributing to its greater tolerance for Zn, Pb, and Cu than T. arvense. In evaluating the two legume candidates, L. corniculatus was positively correlated with Zn, Pb, and Cu like A. artemisiifolia, while C. varia emergence did not have significant relationship with Pb and Cu. The current finding implies that L. corniculatus can be a good candidate because of its emergence performance and its tolerance to heavy metal, similarly to that of A. artemisiifolia.

Plant responses, climate pivot points, and trade‐offs in water‐limited ecosystems

Plant species in dryland ecosystems are limited by water availability and may be vulnerable to increases in aridity. Methods are needed to monitor and assess the rate of change in plant abundance and composition in relation to climate, understand the potential for degradation in dryland ecosystems, and forecast future changes in plant species assemblages. I employ nearly a century of vegetation monitoring data from three North American deserts to demonstrate an approach to determine plant species responses to climate and critical points over a range of climatic conditions at which plant species shift from increases to decreases in abundance (climate pivot points). I assess these metrics from a site to regional scale and highlight how these indicators of plant performance can be modified by the physical and biotic environment. For example, shrubs were more responsive to drought and high temperatures on shallow soils with limited capacity to store water and fine‐textured soils with slow percolation rates, whereas perennial grasses were more responsive to precipitation in sparse shrublands than in relatively dense grasslands and shrublands, where competition for water is likely more intense. The responses and associated climate pivot points of plant species aligned with their lifespan and structural characteristics, and the relationship between responses and climate pivot points provides evidence of the trade‐off between the capacity of a plant species to increase in abundance when water is available and its drought resistance.

Climate warming-induced upward shift of Moso bamboo population on Tianmu Mountain, China

Although increasing attention has been paid to upward shift of plant species in altitude as a response to global warming, research on this phenomenon at low altitudinal and low latitudinal zones did not receive enough attention. In this study, an investigation was carried out to test the relationship between the upward spread of Moso bamboo (Phyllostachys pubescens) along altitudinal gradient and the increasing air temperature over the past decade within the Tianmu Mountain region, situated in southeastern China. Results showed that the peak elevation of Moso bamboo population establishment rose by an average of 9.8 m (±2.7 m) during the past decade and significant correlation existed with mean annual temperature (P < 0.0001, n = 339) but not with annual precipitation (P = 0.7, n = 339), indicating that the upward shift of Moso bamboo along altitudinal gradients was driven primarily by warming temperatures. This upward shift could potentially reduce biodiversity by altering the species composition of the ecosystem. However, there is also the potential for increased carbon sequestration capacity of local forest systems, which would produce an additional carbon sink to combat rising atmospheric CO2 concentrations and future global warming.

Flowering phenology and reproductive fitness along a mountain slope: maladaptive responses to transplantation to a warmer climate in Campanula thyrsoides

In many biomes, global warming has resulted in advanced and longer growing seasons, which has often led to earlier flowering in plant taxa. Elevational gradients are ideal to study the effects of global warming as they allow transplantation of plants from their original cooler higher elevations down to elevations with a prospective climate. We transplanted plants from ten populations of the European alpine monocarpic herb species Campanula thyrsoides L. to three sites along a steep mountain slope (600, 1,235 and 1,850 m above sea level) in the Swiss Alps and asked whether reproductive phenology adjusts plastically to elevation and if these responses were adaptive, i.e. increased the fitness of plants. We further assessed current genetic differentiation in phenotypic traits and whether any such origin effects were due to adaptation to climatic conditions of origin. Our results showed that transplantation to lower elevations caused strong shifts in phenology, with plants starting growth and flowering earlier than plants placed at higher elevations. However, compared to flower production at high elevation, number of flowers per plant decreased 21 % at mid- and 61 % at low elevation. The shift in phenology thus came with a high cost in fitness, and we suggest that phenology is maladaptive when C. thyrsoides faces temperature conditions deviating from its natural amplitude. We conclude that the frequently reported phenological shift in plant species as a response to global warming may include heavy fitness costs that may hamper species survival.

Response to Comments on “Changes in Climatic Water Balance Drive Downhill Shifts in Plant Species’ Optimum Elevations”

Wolf and Anderegg, Hijmans, and Stephenson and Das suggest that our findings of changes in climatic water balance driving downhill shifts in plant species distributions are flawed. We demonstrate that the conclusions these authors make are subject to the selection of methods they apply and do not provide sufficient evidence to reject our original findings.

Comment on “Changes in Climatic Water Balance Drive Downhill Shifts in Plant Species’ Optimum Elevations”

Crimmins et al. (Reports, 21 January 2011, p. 324) presented a study that purports to show that plants in California are shifting downslope to maintain a constant water deficit. We argue that the results are limited in scope to just a handful of woody species in one part of the state and are confounded by methodological errors.