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1,523 results for “steppe”
STEPPS 2000 Year Forest Composition Estimates, Upper Midwest US, Level 2
Forest ecosystems in eastern North America have been in flux for the last several thousand years, well before Euro-American land clearance and the 20th-century onset of anthropogenic climate change. However, the magnitude and uncertainty of prehistoric vegetation change have been difficult to quantify because of the multiple ecological, dispersal, and sedimentary processes that govern the relationship between forest composition and fossil pollen assemblages. Here we extend STEPPS, a Bayesian hierarchical spatio-temporal pollen-vegetation model, to estimate changes in forest composition in the upper Midwestern United States from about 2,100 to 300 years ago. Using this approach, we find evidence for large changes in the relative abundance of some species, and significant changes in community composition. However, these changes took place against a regional background of changes that were small in magnitude or not statistically significant, suggesting complexity in the spatio-temporal patterns of forest dynamics. The single largest change is the infilling of Tsuga canadensis in northern Wisconsin over the past 2000 years. Despite range in-filling, the range limit of T. canadensis was largely stable, with modest expansion westward. The regional ecotone between temperate hardwood forests and northern mixed hardwood/conifer forests shifted southwestward by 15-20 km in Minnesota and northwestern Wisconsin. Fraxinus, Ulmus, and other mesic hardwoods expanded in the Big Woods region of southern Minnesota. The increasing density of paleoecological data networks and advances in statistical modeling approaches now enables the confident detection of subtle but significant changes in forest composition over the last 2,000 years.This material is based upon work supported by the National Science Foundation under grants #DEB-1241874, 1241868, 1241870, 1241851, 1241891, 1241846, 1241856, 1241930.
STEPPS 8000 Year Forest Composition Estimates, Northeastern US, Level 2
These reconstructions of forest composition in the northeastern US for the last 8,000 years help establish natural baselines, variability, and trajectories of forest dynamics before and during the emergence of intensive anthropogenic land use. These reconstructions are based on 1) the pollen–vegetation model (PVM) STEPPS, 2) a network of fossil and modern pollen data mostly drawn from the Neotoma Paleoecology Database (www.neotomadb.org), and 3) a vegetation calibration dataset based on a spatial statistical model of relative tree abundances from the Township Proprietor Survey (TPS) from the early EuroAmerican settlement period. STEPPS is a process-based Bayesian Hierarchical Model that is run in two stages: a parameterization stage based upon spatial data layers of forest composition and pollen assemblages, and a prediction stage based on fossil pollen assemblages. The statistical modeling of the TPS forest data and relative abundances is described by Paciorek et al. (2016, PLoS One, doi: 10.1371/journal.pone.0150087) and is available at EDI as PalEON Products msb.paleon.1 (doi: 10.6073/pasta/8544e091b64db26fdbbbafd0699fa4f9) and msb.paleon.4 (doi: 10.6073/pasta/3c4844cfe8beff6b173b62034d1cb5d8). The parameterization of STEPPS and comparison to REVEALS, a different widely used PVM, is described by Trachsel et al. (2020, Quaternary Research, doi:10.1017/qua.2019.81). Both PVMs predict the observed macroscale patterns of vegetation composition in the NEUS; however, reconstructions of minor taxa are less accurate and predictions for some taxa differ between PVMs. These differences can be attributed to intermodel differences in structure and parameter estimates. STEPPS parameter estimates are similar between the UMW and NEUS, suggesting that STEPPS parameter estimates are transferable between floristically similar regions and scales. The parameterized STEPPS model was then run for a network of fossil pollen records from the Neotoma Paleoecology Database to produce post
Decoupled responses of above- and below-ground beta-diversity to nitrogen enrichment in a typical steppe
<p>Increased atmospheric nitrogen (N) deposition affects biodiversity in terrestrial ecosystems. However, we do not know whether the effects of N on above-ground plant β-diversity are coupled with changes occurring in the soil seed bank. We conducted a long-term N-addition experiment in a typical steppe and found that above-ground β-diversity increased and then decreased with increasing N addition, whereas below-ground β-diversity decreased linearly. This suggests decoupled dynamics of plant communities and their soil seed bank under N enrichment. Species substitution determined above- and below-ground β-diversity change via an increasing role of deterministic processes with N addition. These effects were mostly driven by differential responses of the above-ground vegetation and the soil seed bank β-diversities to N-induced changes in environmental heterogeneity, increased soil inorganic N concentrations and soil acidification. Our findings highlight the importance of considering above- and below-ground processes simultaneously for effectively conserving grassland ecosystems under N enrichment.</p>
Pushing the limits of C3 intrinsic water use efficiency in Mediterranean semiarid steppes: responses of a drought-avoider perennial grass to climate aridification
<ol> <li>Intrinsic water use efficiency (WUEi) reflects the trade-off between photosynthetic carbon gain and water loss through stomatal conductance and is key for understanding dryland plant responses to climate change. <em>Stipa tenacissima</em> is a perennial tussock C<sub>3</sub> grass with an opportunistic, drought-avoiding water use strategy that dominates arid and semiarid steppes across the western Mediterranean region. However, its ecophysiological responses to aridification and woody shrub encroachment, a major land-use change in drylands worldwide, are not well understood.</li> <li>We investigated the variations in leaf stable isotopes (δ<sup>18</sup>O, δ<sup>13</sup>C, δ<sup>15</sup>N), nutrient concentrations (N, P, K), and culm water content and isotopic composition (δ<sup>18</sup>O, δ<sup>2</sup>H) of paired pure-grass and shrub-encroached <em>S. tenacissima</em> steppes along a 350 km aridity gradient in Spain (10 sites, 160 individuals). </li> <li>Culm water isotopes revealed that <em>S. tenacissima</em> is a shallow-rooted grass that depends heavily on recent rainwater for water uptake, which may render it vulnerable to increasingly irregular rainfall combined with faster topsoil drying under climate warming and aridification. With increasing aridity, <em>S. tenacissima</em> enhanced leaf-level WUEi through more stringent stomatal regulation of plant water flux and carbon assimilation (higher δ<sup>13</sup>C and δ<sup>18</sup>O), reaching exceptionally high δ<sup>13</sup>C values (-23 to -21‰) at the most arid steppes. Foliar N concentration was remarkably low across sites regardless of woody shrub encroachment, evidencing severe water and N co-limitation of photosynthesis and productivity. Shrub encroachment decreased leaf P and K but did not affect <em>S. tenacissima</em> water status. Perennial grass cover decreased markedly with both declining winter rainfall and shrub encroachment suggesting population- rather than individual-level responses of <em>S. tenacissima</em> to these changes.</li> <li>The fundamental physiological constraints of photosynthetic C<sub>3</sub> metabolism combined with low foliar N content may hamper the ability of <em>S. tenacissima</em> and other drought-avoider species with shallow roots to achieve further adaptive improvements in WUEi under increasing climatic stress. A drought-avoiding water use strategy based on early stomatal closure and photosynthesis suppression during prolonged rainless periods may thus compromise the capacity of <em>S. tenacissima</em> steppes to maintain perennial grass cover, sustain productivity and cope with ongoing climate aridification at the drier parts of their current distribution. </li> </ol>
The Highs and Lows of Grazing: Effects of Ungulates and Elevation on Grassland and Sagebrush Steppe Vegetation Composition in Yellowstone National Park
<p>Yellowstone National Park’s Northern Range is emblematic for the wolves, bison and elk that inhabit its grassland and sagebrush-steppe habitats. Their interactions and populations have been the focus of considerable conservation debate. Recent changes in ungulate populations provide an opportunity to examine their influence on the vegetation communities. We conducted expansive vegetation surveys along an elevation gradient and at exclosure sites where ungulates were unable to graze. We collected a large database (n = 620 quadrats), which we analyzed using classic community ecology approaches. We found that non-native species have higher abundances at low elevations, and that grazing by ungulates reduces beta diversity and native cover, while promoting non-native cover. The magnitude of these changes are greater in bison-dominated than elk-dominated areas of Yellowstone, suggesting that bison may be overgrazing. These results provide valuable insights into major factors shaping vegetation communities, while also contextualizing management practices in a world-renowned ecosystem.</p> <p> </p> <p>Please respect licensing, and contact the corresponding author for permission to use this dataset in any research or publications. </p>
Data from: Dominance and competition drive assemblage configuration in an Iberian steppe bird community
<p>Open scripts and data bases for Proceedings of the Royal Society B: Biological Sciences ( Barrero et al., Dominance and competition drive assemblage configuration in an Iberian steppe bird community).</p> <p>Four documents are provided: The two R Scripts needed to create and fix the models and two .xls files with the data described below.</p> <p>Scripts: a) HMSC_2022_FullModel_Run_GitHub.Rmd: script to run the full model. b) HMSC_2022_NullModel_Run_GitHub.Rmd: script to run the null model.</p> <p>Xlsx: a) Grid.xlsx: Coordinates of the species surveyed. b) Data2.xlsx: Habitat descriptor variables</p>
Fig. 4 in Interspecific Agression Of The Passerine Birds (Aves, Passeriformes) On Watering Places In Wood-And-Steppe Zone Of Ukraine
Fig. 4. Rating of success of attack and defense of birds in Kaniv Nature Reserve.
Fig. 5 in Interspecific Agression Of The Passerine Birds (Aves, Passeriformes) On Watering Places In Wood-And-Steppe Zone Of Ukraine
Fig. 5. Rating of success of attack and defense of birds State Arboretum "Alexandria".
Fig. 2 in A Pasture Of Big Ungulate Animals As Key Ecological Factor Influencing On The Fluctuation Of Natural Habitat Of Steppe Herbivorous Mammals
Fig. 2. The steppe marmot quantity dynamics in the 20–21th century (cattle vs the steppe marmot).
Dataset for: Intercontinental analysis of temperate steppe stream food webs reveals consistent autochthonous support of fishes
<p>Quantifying the trophic basis of production for freshwater metazoa at broad spatial scales is key to understanding ecosystem function and has been a research priority for decades. However, previous lotic food web studies have been limited by geographic coverage or methodological constraints. We used compound-specific stable carbon isotope analysis of amino acids to estimate basal resource contributions to fish consumers in streams spanning grassland, montane, and semi-arid ecoregions of the temperate steppe biome on two continents. Across a range of stream sizes and light regimes, we found consistent trophic importance of aquatic resources. Essential amino acids of heterotrophic microbial origin generally provided secondary support for fishes, while terrestrial carbon did not seem to provide any significant, direct support. These findings provide strong evidence for the dominant contribution of carbon to higher-order consumers by aquatic autochthonous resources (primarily) and heterotrophic microbial communities (secondarily) in temperate steppe streams.</p>
Fig. 1 in Megachilid bees (Hymenoptera: Megachilidae) of the forest-steppe and steppe zones of the West Siberian Plain to the eastward of Irtysh River
Fig. 1. Map of the study area and location of collecting sites.
Fig. 8 in Phenology And Population Structure Of Forest Herbaceous Species In Artificial And Natural Communities In The Steppe Zone Of Ukraine
Fig. 8. Dates of onset and duration of budding (1) and flowering (2).
Figure 2 in New materials on heteropterans from Kurai steppe (south-west of Russian Altai)
Figure 2. Collection points of heteropterans in the Kurai steppe and North-Chuya Mt. Range.
Do plant-soil feedbacks promote coexistence in a sagebrush steppe?
<p>Recent studies have shown the potential for negative plant-soil feedbacks (PSFs) to promote stable coexistence but have not quantified the stabilizing effect relative to other coexistence mechanisms. We conducted a field experiment to test the role of PSFs in stabilizing coexistence among four dominant sagebrush steppe species that appear to coexist stably, based on previous work with observational data and models. We then integrated the effects of PSF treatments on focal species across germination, survival, and first-year growth. To contribute to stable coexistence, soil microbes should have host-specific effects that result in negative feedbacks. Over two replicated growing seasons, our experiments consistently showed that soil microbes have negative effects on plant growth, but these effects were rarely host-specific. The uncommon host-specific effects were mostly positive at the germination stage and negative for growth. Integrated effects of PSF across early life-stage vital rates showed that PSF-mediated self-limitation occasionally had large effects on projected plant biomass but occurred inconsistently between years. Our results suggest that while microbially-mediated PSF may not be a common mechanism of coexistence in this community, it may still affect the relative abundance of dominant plant species via changes in host fitness. Our work also serves as a blueprint for future investigations that aim to identify underlying processes and test alternative mechanisms to explain important patterns in community ecology.</p>
Effects of long-term mowing on leaf- and root-associated bacterial community structures are linked to functional traits in 11 plant species from a temperate steppe
<ol> <li><span>Long-term mowing can cause morphological stuntedness of plants, thus reducing grassland productivity and exacerbating grassland degradation. Although plant microbiomes can enhance plant resistance against disturbance, considerable uncertainty exists regarding how mowing and mowing-induced plant trait plasticity affect plant microbiomes in natural grasslands. </span></li> <li><span>Here we examined the responses of leaf-/root-associated bacterial (LAB/RAB) communities of 11 dominant herbaceous perennials (6 replicates per species) to a 17-year mowing treatment in a temperate grassland. We also measured leaf/root physiological and morphological traits and analyzed the relationships among mowing practice, bacterial community structures, and leaf/root trait parameters. </span></li> <li><span>We found that both leaf and root functional traits showed interspecific variations (variations across different plant species), while only the leaf traits exhibited intraspecific variation (treatment-induced variations within plant species) between the treatments. Similarly, the LAB community structure was more sensitive to mowing but less influenced by host species identity, compared to the RAB community. The RAB community structure was primarily shaped by host species identity, while mowing was a secondary influencing factor. </span></li> <li> <span>The different patterns of LAB and RAB communities in response to mowing could be specifically explained by the inter-/intraspecific variations of the related leaf and root traits. The LAB community was strongly correlated with the leaf traits which exhibited mowing-induced plasticity (intraspecific variation), with the correlations with nitrogen resorption efficiency and aboveground dry weight being the greatest. The root traits were important indicators of bacterial community structure in the root compartment across the hosts, rather than between the treatments. Root tissue density</span> <span>showed the strongest interspecific variation, and was identified as an overwhelming driver of the RAB community. The shifts in LAB/RAB communities under mowing were largely attributed to the increased proportions of Actinobacteria. The high mowing sensitivity of the LAB community was associated with the enrichment of soil-derived Actinobacteria in leaves under mowing. Actinobacteria were also the main keystone taxa in the bacterial community networks under mowing.</span> </li> <li><span>Our results demonstrate that the magnitude of plant-associated microbial community response to long-term mowing is plant compartment- and trait-variation-dependent, and advance our understanding of the leaf/root microbiome-trait relationships in complex plant communities.</span></li> </ol>
Restoration temporarily supports the resilience of sagebrush-steppe ecosystems subjected to repeated fires
<p>Many ecosystems are experiencing increased fire frequencies and species invasions that can erode their resilience and cause a shift to alternative states. In the sagebrush-steppe, a semi-arid shrubland ecosystem in North America, restoration treatments are often implemented following wildfire to enhance their resilience to invasion. However, little is known about the long-term effectiveness of these treatments. We investigated whether repeated restoration efforts provide greater resilience in sagebrush-steppe communities initially dominated by species with different post-fire regeneration traits and subjected to compounding wildfires and invasion by <em>Bromus tectorum</em> over 25 years.</p> <p>We studied 37 permanent transects (Columbia Basin, Washington, USA) in which species abundance was recorded multiple times from 1992 to 2017. We quantified community change and its relationship with fire, restoration, and moisture availability. Resilience was evaluated by quantifying community resistance and stability indices.</p> <p>The greatest change occurred in communities where the obligate seeding shrub <em>Artemisia tridentata</em> was initially common. Repeated fires led to the extirpation of this shrub and eventual dominance of <em>B. tectorum</em>. Herbicide applications temporarily suppressed <em>B. tectorum</em> post-fire. Seeding treatments and above average precipitation initially increased native cover. Although communities where resprouting species were common showed the least change, repeated fires did lead to a gradual but substantial decline (86%) in resprouting shrubs.</p> <p><em>Synthesis and applications:</em> Our findings show that repeated restoration efforts, together with elevated precipitation, can support native species re-establishment in systems experiencing altered disturbance regimes and species invasions. Our unique long-term dataset demonstrates, however, that many such interventions have short-lived effects due to the strong "unhelpful resilience" of highly invaded systems. This implicitly suggests that many such systems have experienced fundamental shifts in ecosystem state. The likelihood of this occurring is strongly associated with the dominant species post-fire regeneration traits. We predict that community composition and resilience will continue to degrade in the sagebrush-steppe unless management prioritizes fire suppression and an adaptive restoration approach that considers resource availability.</p>
Ecosystem stability is determined by plant defense functional traits and population stability under mowing in a semi-arid temperate steppe
<ol> <li><span>As a common grassland management practice in many high-latitude regions worldwide, mowing has great impacts on grassland functioning and stability. Species richness, species asynchrony and species stability have been suggested as central in responses to environmental change. Mowing can evoke plant defense systems due to physical damages to plants. However, no studies have comprehensively evaluated the role of plant defense functional traits, species richness, species asynchrony and stability in ecosystem functioning under mowing regimes across time-scales. </span></li> <li> <span>In the present study, we set up short-term (4-years) and long-term (16-years) mowing experiments with three stubble heights (control, 10 cm, 2 cm) in a temperate steppe of Inner Mongolia. We investigated the effects of mowing-induced changes in distribution metrics associated with plant defense traits, i.e. mean, variance, skewness and kurtosis of trait distribution, on ecosystem stability of grassland communities using structural equation modeling.</span> </li> <li><span>We found that grassland ecosystem stability was enhanced by increasing mowing duration and decreasing stubble height. Mowing-induced increases in abundance and diversity of plant defense traits contributed to greater ecosystem stability by enhancing species asynchrony and population stability. Moreover, we found that mowing enhanced the abundance and diversity of plant defense traits of dominant species and contributed to population stability and species asynchrony, thus enhancing temporal stability of grassland ecosystems. </span></li> <li><span>These results demonstrate the important roles of plant defense traits in maintaining stability of grasslands under mowing, and highlight that, in addition to species richness, asynchrony and population stability, plant functional defense trait act in stabilizing ecosystem functions under human-induced environmental changes.</span></li> </ol>
Interannual variation in climate contributes to contingency in post-fire restoration outcomes in seeded sagebrush steppe
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Data from: Long-term mowing regulates the responses of above- and below-ground net primary productivity stability to water and nitrogen addition in a temperate steppe
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Data from: Nitrogen fertilization, not water addition, alters plant phylogenetic community structure in a semi-arid steppe
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