Herbaceous Understory Research Articles

Does white-tailed deer density affect tree stocking in forests of the Eastern United States?

BackgroundWhite-tailed deer (Odocoileus virginianus) have increased during the past century in the USA. Greater deer densities may reduce tree regeneration, leading to forests that are understocked, where growing space is not filled completely by trees. Despite deer pressure, a major transition in eastern forests has resulted in increased tree densities.MethodsTo reconcile conflicting trends, we applied generalized linear mixed models to compare deer densities during 1982 and then 1996 to tree stocking after about 30 years and 15 years of potential reductions of small trees by deer, for the entire eastern US and 11 ecological provinces. We also compiled deer browse preferences and compared preferred browse with trends in tree species composition from historical (1620–1900) and current tree surveys.ResultsThe forested area of the eastern US, including a prairie ecological province, was equally well-stocked (52%) and understocked (48%) during 2011–2017 tree surveys. For 1982 deer densities, 38% of area had deer densities > 5.8 deer/km2 and for 1996, 66% of area had deer densities > 5.8 deer/km2. Deer densities and tree stocking were not related significantly for the entire eastern US. Deer may reduce tree stocking in the Laurentian Mixed Forest; however, this province had both lower deer densities and greater tree stocking than other provinces. Furthermore, major tree species trends did not match tree browse preferences.ConclusionsRather than too few trees, too many trees is an ecological problem where historical open oak and pine forests had herbaceous understories, and currently, trees have captured growing space. We attribute other drivers than deer to explain this transition.

Understory plant composition and nitrogen transformations resistant to changes in seasonal precipitation

AbstractClimate change has increased global mean surface temperatures and altered hydrological processes, and projections suggest that these changes will accelerate. As seasonal precipitation patterns change, so will the soil resources available for plants. In the midwestern United States, winter temperatures and precipitation are expected to increase, while snowfall is expected to be reduced. Reduced snowpack could lead to greater frost damage and alter the timing and amount of plant available resources at the start of the growing season. In the summer, precipitation is expected to decrease, and variability is expected to increase, creating longer and more frequent dry periods. In temperate forests, herbaceous understory plants and woody plants in early developmental stages are expected to be highly sensitive to changes in abiotic conditions. Here, we study how seasonal changes in precipitation affect the timing and availability of resources in a temperate deciduous forest. Further, we examine how changes in abiotic conditions influence understory composition and woody plant recruitment. We established a fully factorial experiment that manipulated winter snowfall and summer precipitation to create wet, dry, and control (ambient) conditions in a temperate deciduous forest near West Lafayette, Indiana, USA. We found that large changes in winter and summer precipitation appeared to affect forest processes independently of one another, and changes in seasonal precipitation altered understory composition minimally and had little to no effect on mineralization rates. The recruitment of woody plant species may be more sensitive to altered precipitation, as snow removal lowered germination rates and wet summer conditions lowered relative growth of a woody plant species, Lindera benzoin. In general, though, ecological processes in this forest understory were relatively resistant to change, at least in the short timeframe of this experiment.

A structured decision making analysis to increase a Red-cockaded Woodpecker population and balance stakeholder objectives for a National Forest

Longleaf pine (Pinus palustris) savanna is a biodiverse ecosystem native to the southeastern United States. Due to fire suppression and timber harvest, longleaf pine has declined to 3% of its original range. The extant forest provides habitat for many threatened and endangered species, including the endangered Red-cockaded Woodpecker (Picoides borealis; RCW), a cavity-nesting bird that co-evolved with fire-maintained forest, resulting in savanna-like old-growth forest as the bird’s preferred habitat. Our study site, the Oakmulgee Ranger District of the Talladega National Forest, harbors the largest RCW population in Alabama and is managed with an emphasis on RCW conservation. The United States Forest Service (USFS) also manages the Oakmulgee for uses such as wildlife conservation, recreation, and timber harvest. Despite efforts to restore RCW habitat and install artificial cavities in the Oakmulgee, the number of RCW groups has not exceeded 123, although the Recovery Plan objective is 394 groups. Our project was motivated by the USFS expressing interest in determining why the RCW population has not exceeded 123 groups. We proposed using structured decision making (SDM) with the USFS and other stakeholders to address this problem. Our goals were to explicitly define management objectives, build a Bayesian belief network with a model of how decision alternatives are believed to affect management objectives, and use a sensitivity analysis to determine the part of the model to which RCW population growth was most sensitive. Therefore, results from the analysis were expected to give insights into 1) ecological factors limiting RCW population growth, 2) how management can overcome these limits, plus 3) the relative expected ability of different decision alternatives to satisfy multiple objectives in addition to increasing RCW group number. We held four SDM workshops with representatives from the USFS, the Animal and Plant Health Inspection Service, the Longleaf Alliance, the Birmingham Audubon Society, and local residents. Stakeholder objectives consisted of maximizing the following: RCW group number, forest health, recreational enjoyment, community economic health, and aesthetics. Cavity insert installation had the greatest probability of increasing the number of RCW groups. The number of RCW groups was most affected by cavity availability, adult survival, reproductive output, food availability, and herbaceous understory. Prescribed burning was most likely to meet the combination of stakeholder objectives, followed by midstory removal. Our findings suggest that cavity installation efforts may need to be increased in the Oakmulgee to increase RCW group number. Also it could be beneficial to investigate how RCWs select cavity tree locations with the goal of increasing the chance that RCWs use artificial cavities to form new groups. The Bayesian belief network provided insights into factors limiting RCW population growth and how management can overcome these limits. The Bayesian belief network also can be used to prioritize management methods in the Oakmulgee given stakeholder objectives and time constraints.

Site Factors Influence on Herbaceous Understory Diversity in East Texas Pinus palustris savannas

Longleaf pine (Pinus palustris) savannas were once dominant across the southeastern U.S., including East Texas and parts of western and central Louisiana. The diverse understory associated with these historical savannas may occasionally be seen today, but not often in longleaf pine ecosystems. This project aimed to define east Texas site characteristics that are necessary to support these ecosystems with a dense and diverse herbaceous understory with little to no midstory cover. Fifty-nine plots across three study sites were established to evaluate the influence of overstory cover, basal area, aspect, elevation, and slope on the number of plant genera present. Forest structure and site characteristics had significant effects on the number of plant genera found. The number of genera increased with higher elevation and slope; as elevation increased, there was a decline in basal area and overstory cover, leading to a more diverse, understory layer. In order to re-establish and maintain a diverse, herbaceous understory in longleaf pine savannas, sites with more open canopies and on slopes with the most solar exposure should be given priority, particularly when planting desired understory species.

Seed Sourcing for Longleaf Pine Herbaceous Understory Restoration: Little Bluestem (Schizachyrium scoparium) and Hairy Lespedeza (Lespedeza hirta) Restoration Genetics

Restoration of the herbaceous understory community of the longleaf pine ecosystem is limited by the availability of appropriate seeds. To understand the relationship of seed transfer zones and genetic composition of two co-occurring species of the herbaceous understory, seeds of little bluestem (Schizachyrium scoparium) and hairy lespedeza (Lespedeza hirta) were collected from five provisional seed transfer zones across the historical range of the longleaf pine ecosystem in the North American Coastal Plain as well as a commercially available seed source originating from outside this range. To determine the genetic structure and diversity of these plants within the seed transfer zones and the commercial source, microsatellite and inter-simple sequence repeats (ISSR) markers were used for little bluestem and hairy lespedeza, respectively. For both species, plants from within the five seed transfer zones were genetically distinct from the commercial source from Kentucky. Little bluestem and hairy lespedeza plants from two provisional seed transfer zones were more genetically similar to each other than they were to other seed zones, which could justify merging these two zones. The genetic relationships among the remaining seed zones, including the commercial source from Kentucky, roughly follow geographic proximity, with genetic similarity decreasing as a function of geographic distance. Most of the genetic variation was partitioned within and less among seed zones, despite documenting significant differences among seed zones. The results of this study support the sub–The Nature Conservancy ecoregion seed transfer zones while acknowledging species-specific differences among seed transfer zones for the longleaf pine ecosystem.

Responses of early-successional songbirds to a two-stage shelterwood harvest for oak forest regeneration

BackgroundThe early stage of forest succession following disturbance is characterized by a shift in songbird composition as well as increased avian richness due to increased herbaceous growth in the forest understory. However, regeneration of woody species eventually outcompetes the herbaceous understory, subsequently shifting vegetation communities and decreasing availability of vital foraging and nesting cover for disturbance-dependent birds, ultimately resulting in their displacement. These early stages following forest disturbance, which are declining throughout the eastern United States, are ephemeral in nature and birds depend on such disturbances for nesting and other purposes throughout their lives.MethodsWe investigated the use of a two-stage shelterwood method to manage long-term persistence of seven early successional songbirds over a 13-year period in an upland hardwood forest within the southern end of the mid-Cumberland Plateau in the eastern United States.ResultsCanopy and midstory gaps created after initial harvest were quickly exploited by tree growth and canopy cover returned to these areas, accelerating the displacement of early-successional species. Woody stem densities increased substantially following stage two harvest as advanced tree regeneration combined with the re-opening of the overstory layer increased resource competition for early-successional plants in the understory. Carolina Wren (Thryothorus ludovicianus), Eastern Towhee (Pipilo erythrophthalmus), Indigo Bunting (Passerina cyanea), and Yellow-breasted Chat (Icteria virens) were characterized by immediate increases following initial harvest in 2001; while the American Goldfinch (Spinus tristis), Prairie Warbler (Setophaga discolor), and White-eyed Vireo (Vireo griseus) did not show an immediate response. Stage two harvest in 2011 rejuvenated vegetation which benefitted focal species, with six of seven species showing increases in densities between 2010 and 2012.ConclusionThe two-stage shelterwood method created conditions advantageous to early-successional birds by helping to re-establish understory vegetation through periodic disturbance to the canopy layer. This method provides evidence that early-successional species can be managed long-term (> 15 years) while using relatively small spatial disturbance through the two-stage shelterwood method.

Plant community dynamics following hazardous fuel treatments and mega-wildfire in a warm-dry mixed-conifer forest of the USA

The greater than 200,000 ha Wallow Fire of May-July 2011 burned through mixed-conifer and ponderosa pine forests in Arizona and New Mexico in the southwestern U.S. This “mega-fire” set the stage for an opportunistic study to examine understory plant community responses to pre-fire fuel reduction treatments in areas dominated by dry mixed-conifer forests. In 2016, five years after the fire, we remeasured nine pairs of treated and untreated sites that were installed in 2012 and compared understory characteristics including species cover, richness and community composition. Native plant cover was significantly higher (20% total cover) in areas that were treated for fuel reduction before the fire compared with untreated areas (17% cover), despite the variability in fire severity and tree mortality. Non-native plant cover was not significantly different between treated and untreated units. Herbaceous understory cover was negatively correlated (p < 0.05) with total tree basal area and tree canopy cover in treated as well as untreated units, and positively correlated with tree mortality and basal area mortality in the untreated units. In the treated units, species richness and diversity were negatively (r = −0.62 to −0.63) correlated with insolation and elevation. Non-metric multidimensional scaling ordinations along with univariate results suggested that community composition was driven by increased insolation following loss of tree canopy. Cover of species that benefit from high light and warmer temperatures, such as some shrubs and perennial graminoids, increased from 2012 to 2016. Overall, fuel reduction treatments led to persistent increases in cover of native species, lending weight to the usefulness of hazardous fuel reduction treatments in promoting native plant cover.

Complex Rangeland Systems: Integrated Social-Ecological Approaches to Silvopastoralism

Crossing disciplinary boundaries, particularly between social and ecological sciences, challenges those seeking to contribute to solving complex and multidimensional environmental problems on rangelands. In this Special Issue we present a set of 13 papers that to varying degrees attempt to integrate, or bring together, diverse approaches across disciplines to understand silvopastoral systems. The papers are about rangelands in numerous countries and regions, including Spain, Estonia, Greece, Germany, Hungary, Italy, Portugal, Romania, the United States, Latin America, and Sweden. Silvopastoral systems provide ecosystem goods and services important to communities, cultures, and society. Management deliberately exploits the diversity fostered by rangeland systems that mix woody species with a well-developed herbaceous understory, offering a greater diversity of products, species, vegetation structural characteristics, and habitat components than either grassland or forest. Biodiversity often peaks at the intermediate levels of tree and shrub cover characteristic of silvopastoral systems. We introduce the papers grouped by four overarching topics: 1) typologies and scales, 2) social-ecological interactions, 3) integrated management, and 4) multiple knowledge systems. Unfortunately, silvopastoral systems often run afoul of ongoing intensification and simplification trends in agricultural production that reduce their economic and ecological resilience. Privately owned systems, the most common in this issue, are subject to the need for owner income. Finding ways to support the benefits of these systems for the public is difficult, as management traditions must be conserved as well as the land. We hope this issue illustrates the value of multifunctional systems and offers insights into how they work.

Revision of a state‐and‐transition model to include descriptions of state functional attributes

AbstractSuccessful conservation of ecosystems and ecosystem services requires understanding the structural–functional relationships underlying resilience to disturbance pressures. State‐and‐transition models (STMs) are box‐and‐arrow diagrams conceptualizing system resilience, but many STMs lack functional descriptions. For a cattle‐grazed sagebrush steppe ecosystem in northwestern Colorado, we aimed to update an existing STM by incorporating functional descriptions of the states to inform future hypotheses. In this STM, a diverse set of native perennial understory plants define a Diverse state, but long‐term exclusion of disturbances to sagebrush results in a shift to a Depauperate state with increased bare ground interspaces and sagebrush dominance. We hypothesized that herbaceous species were inferior competitors to sagebrush over the long term for soil nitrogen. To examine evidence for this hypothesis, develop functional descriptions of the Diverse and Depauperate states, and identify more specific hypotheses for future studies, we measured the following: the mass, C:N, and distribution of the litter layer; nitrogen mineralization rates; nitrate pools; and soil attributes on plots classified as Diverse (n = 5) or Depauperate (n = 5). Plots in the Depauperate state had ~20% higher soil bulk density, half the clay and soil moisture concentrations, and 30% lower percent soil nitrogen compared to Diverse state plots; litter layer patchiness was nearly three times greater on the Depauperate plots than on the Diverse plots, but there was no significant difference between states in mean litter layer mass or C:N. We detected no significant differences between states in nitrogen mineralization rates or nitrate pools. This may be due to our sampling design, which examined nitrogen transformation at the plot level rather than at microsites within the plots, or it may be that another resource such as soil moisture is more limiting than nitrogen. Differences in soil texture between plots in the Diverse and Depauperate states may indirectly influence the competitive interactions between sagebrush and native herbaceous understory by controlling available soil resources. These results suggest that the vulnerability of sagebrush steppe ecosystems to state changes may be dependent on soil texture, which is highly variable across this broadly distributed ecosystem. Based on these insights, we present a revised STM and propose future work.

Leaf area index in a forested mountain catchment

Leaf area index (LAI) belongs among the catchment characteristics widely used in hydrological models but still associated with great uncertainties. In a mountain forest catchment, the leaf area affects retention and evapotranspiration loss, and it could be significantly modified by forestry practices. In this study, LAI in mature stands of Norway spruce (Picea abies) and European beech (Fagus sylvatica) was analysed in headwater catchments of the Jizera Mountains (Czech Republic) between 2012 and 2016. A comparison evaluation of LAI in harvested site with dominant herbaceous vegetation was taken into account by applying direct ground investigation what was compared with hemispherical canopy photography (Gap light analyser GLA-V2) and satellite remote sensing (Sentinel-2 mission). While the direct ground measurement includes only the foliage (leaves or needles), the Gap light analysis is affected by trunks and branches, and the remote sensing techniques by herbaceous understory. The results of the Gap light analyser underestimated the ground based LAI values by 52–76 per cent, and satellite interpretations by 29–73 per cent. The remote sensing is capable to provide effective information on the distribution of LAI within the time and space. However, in a catchment scale, the satellite detection underestimated average LAI values approx. by 42–62 per cent. Changes in the observed rainfall interception reflected well the LAI variation.

Long-term pine regeneration, shrub layer dynamics, and understory community composition responses to repeated prescribed fire in Pinus resinosa forests

Prescribed fire is increasingly viewed as a valuable tool for reversing ecological consequences of fire suppression within fire-adapted forests. While the use of burning treatments in northern temperate conifer forests has received considerable attention, the long-term (&gt;10 year) effects on understory composition and dynamics have not been quantified. We describe the persistence of prescribed fire effects on the woody and herbaceous understory in a mature red pine (Pinus resinosa Ait.) forest in northern Minnesota, USA, over a ∼50-year period, as well as the relative roles of fire season and frequency in affecting vegetation responses. Burning treatments were applied from 1960 to 1970 on 0.4 ha experimental units and crossed fire season and frequency in a randomized block design. Burning altered shrub layer dynamics and composition in both the short and long terms and was influenced by both fire season and frequency, with frequent summer season burns having the largest impact, including greatest control of hazel (Corylus spp.). The application of fire facilitated regeneration of pine; however, recruitment into the overstory was limited. Additionally, community composition of the herbaceous understory diverged 40+ years following burning. This study highlights the importance of continued burning in affecting vegetation responses and the potential of fire as a long-lasting vegetation management tool in these forests.

Early accumulation of active fraction soil carbon in newly established cellulosic biofuel systems

We examined relative changes in soil C pools shortly after the establishment of six perennial and two annual bioenergy cropping systems that differed in diversity (monoculture vs. polyculture). Perennial systems included two monocultures (switchgrass, Panicum virgatum; and miscanthus, Miscanthus×giganteus) and four polycultures including hybrid poplar (Populus sp.)+herbaceous understory; mixed native grasses, successional vegetation, and restored prairie. Two annual systems included no-till continuous corn (Zea mays) and rotational corn (corn-soybean (Glycine max)-canola (Brassica napus)). Each crop was planted in a full factorial design at both a moderate fertility Alfisol and a high fertility Mollisol site. Relative differences in active, slow, and passive C pools in surface soils, where C changes are most likely to be detected early, were evaluated with 322-day laboratory incubations followed by acid hydrolysis to infer different pools from exponential decay curves. Five years post-establishment, active C pools under perennial polycultures at the Alfisol site were up to twice those under annual and perennial monocultures, and followed the order hybrid poplars (696±216μgCg−1 soil, n=5 replicate blocks)≈native grasses (656±155)≈restored prairie (638±44)>early successional (500±54)≫continuous corn (237±68)≈rotational corn (180±n.a.). Active C pools in perennial monocultures were similar to those in continuous corn: switchgrass (274±29)≈miscanthus (299±9). In contrast, differences in active C pools among crops at the more fertile Mollisol site were not detectable except for greater pools in the restored prairie and rotational corn systems. At both sites, slow and passive C pools differed little among systems except that slow pools were greater in the poplar system. That diversity rather than perenniality itself led to greater active C pools suggests that polycultures might be used to accelerate soil C accumulation in bioenergy and other perennial cropping systems.

Decline in herb species diversity over two decades in a temperate deciduous forest in Illinois

Abstract Over the past century, the abundance of many plant species has declined noticeably, including in the herbaceous understory of temperate deciduous forests. Two separate censuses of Trelease Woods in Illinois, USA, one in 1994–95 that was repeated in 2015, and a second made annually from 1994–2015, indicated major losses for herb species. Quadrat frequency, flowering quadrat frequency, number of species, number of species in flower, number of individuals, and species diversity (H′) all declined greatly over the census period. Most species saw a marked decline in frequency and density, with the number of individuals declining by two-thirds and some species disappearing entirely. Gains from new colonization were minor in comparison. Among persisting species, almost all became shorter and stopped flowering. Number of individuals per species in 1994 and percentage of individuals lost by 2015 were not related. Spring ephemeral species had less loss in frequency and percentage of individuals lost per spe...

Natural history of Ixodes affinis in Virginia

The ixodid tick species Ixodes affinis is expanding its range northward, changing the tick community population dynamics in the Mid-Atlantic United States. We present five years of surveillance on newly established populations of I. affinis throughout southeastern Virginia and discuss the habitat and host associations of I. affinis in this northernmost extent of its range. We found that I. affinis populations tend to persist once they are established, and populations tend to increase as ecological succession progresses, provided a vegetated understory persists. Populations of I. affinis were never found in the smallest habitat fragments or in xeric dune habitats, and the highest densities of I. affinis were found in mixed pine-hardwood forests with an herbaceous understory. We also document several new mammalian hosts for I. affinis, including house mice (Mus musculus) and coyotes (Canis latrans) and discuss how these hosts may facilitate the continued dispersal of I. affinis and the maintenance of these newly established populations.

Sagebrush treatments influence annual population change for greater sage‐grouse

Vegetation management practices have been applied worldwide to enhance habitats for a variety of wildlife species. Big sagebrush (Artemisia tridentata spp.) communities, iconic to western North America, have been treated to restore herbaceous understories through chemical, mechanical, and prescribed burning practices thought to improve habitat conditions for greater sage‐grouse (Centrocercus urophasianus) and other species. Although the response of structural attributes of sagebrush communities to treatments is well understood, there is a need to identify how treatments influence wildlife population dynamics. We investigated the influence of vegetation treatments occurring in Wyoming, United States, from 1994 to 2012 on annual sage‐grouse population change using yearly male sage‐grouse lek counts. We investigated this response across 1, 3, 5, and 10‐year post‐treatment lags to evaluate how the amount of treated sagebrush communities and time since treatment influenced population change, while accounting for climate, wildfire, and anthropogenic factors. With the exception of chemical treatments exhibiting a positive association with sage‐grouse population change 11 years after implementation, population response to treatments was either neutral or negative for at least 11 years following treatments. Our work supports a growing body of research advocating against treating big sagebrush habitats for sage‐grouse, particularly in Wyoming big sagebrush (A. t. wyomingensis). Loss and fragmentation of sagebrush habitats has been identified as a significant threat for remaining sage‐grouse populations. Because sagebrush may take decades to recover following treatments, we recommend practitioners use caution when designing projects to alter remaining habitats, especially when focused on habitat requirements for one life stage and a single species.

Clay minerals, δ13C values, pollen and non-pollen palynomorphs as palaeoenviromental and palaeoclimatic indicators in Pliocene sediments of central Anatolia, Turkey

AbstractThe Çankırı Basin is one of the largest Cenozoic basins in Central Anatolia, Turkey and contains possible economic hydrocarbon and evaporite reserves. Gypsum is the dominant mineral in the evaporite-bearing Pliocene deposits of the Çankırı Basin. In claystones, the abundance of smectite, dolomite, illite/mica and chlorite in association with minor amounts of mixed-layer chlorite-smectite, mica-vermiculite, amphibole, serpentine, quartz and feldspar together indicate an alkaline environment. Minor kaolinite is also present in some clay samples. Smectite is both detrital and authigenic. Palynological analysis revealed the existence of a mixed forest (Pinus, Cathaya, Tsuga, Cedrus, Abies, Quercus, Ulmus, Juglans, Pterocarya, Acer, Carya, Carpinus, Fagus) dominated byPinuswith a widespread herbaceous understory (Poaceae) interspersed sparsely with open areas occupied by Asteraceae. This flora reflects warm-temperate and humid climatic condition. δ13C analyses have shown that the vegetation was dominated by C3 plants.

Long-term influence of stand thinning and repeated fertilization on forage production in young lodgepole pine forests

Integration of trees with forage and livestock production as silvopastoralism is another potential component of intensive forest management. Stand thinning and fertilization may enhance growth of crop trees and understory forage for livestock. We tested the hypothesis that large-scale precommercial thinning (PCT) (particularly heavy thinning to ≤1000 stems·ha−1) and repeated fertilization, up to 20 years after the onset of treatments, would enhance production of graminoids, forbs, and shrubs as cattle (Bos taurus L.) forage. Results are from two long-term studies: (1) PCT (1988–2013) and (2) PCT with fertilization (PCT–FERT) (1993–2013) of lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) stands in south-central British Columbia, Canada. Mean biomass estimates of graminoids, forbs, total herbs, and shrubs were not affected by stand density. However, fertilization enhanced mean biomass estimates of graminoids, forbs, and total herbs, but not shrubs. Thus, the density part of our hypothesis was not supported, but the nutrient addition part was supported at least for the herbaceous components. Biomass of the herbaceous understory was maintained as a silvopasture component for up to 20 years (stand age 13 to 33 years) in fertilized heavily thinned stands prior to canopy closure.

Wetland management strategies lead to tradeoffs in ecological structure and function

Anthropogenic legacy effects often occur as a consequence of land use change or land management and can leave behind long-lasting changes to ecosystem structure and function. This legacy is described as a memory in the form of ecological structure or ecological interactions that remains at a location from a previous condition. We examined how forested floodplain restoration strategy, based on planting intensity, influenced wetland community structure and soil chemical and physical factors after 15 years. The site was divided into 15 strips, and strips were assigned to one of five restoration treatments: plantings of acorns, 2-year-old seedlings, 5-ft bareroot trees, balled and burlapped trees, and natural seed bank regeneration. Our community composition survey revealed that plots planted with bareroot or balled and burlapped trees developed closed tree canopies with little herbaceous understory, while acorn plantings and natural colonization plots developed into dense stands of the invasive species reed canary grass (RCG; Phalaris arundinacea). Restoration strategy influenced bacterial community composition but to a lesser degree compared to the plant community response, and riverine hydrology and restoration strategy influenced wetland soil conditions. Soil ammonium concentrations and pH were similar across all wetland restoration treatments, while total organic carbon was highest in forest and RCG-dominated plots compared to mixed patches of trees and open areas. The differences in restoration strategy and associated economic investment resulted in ecological tradeoffs. The upfront investment in larger, more mature trees (i.e., bareroot, balled and burlapped) led to floodplain forested communities, while cheaper, more passive planting strategies (i.e., seedlings, seedbank, or acorns) resulted in dense stands of invasive RCG, despite the similar floodplain hydrology across all sites. Therefore, recovery of multiple ecosystem services that encompass plant and microbial-derived functions will need to include additional strategies for the recovery of plants, microbes, environment, and functions.

Ecosystem resilience is evident 17 years after fire in Wyoming big sagebrush ecosystems

AbstractRecent policy has focused on prevention of wildfire in the sagebrush steppe in an effort to protect habitat for the greater sage grouse (Centrocercus urophasianus). Historically, fire return intervals in Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis) ecosystems were 50–100 yr or more, but invasive species, climate change, and a legacy of intensive grazing practices have led to degraded rangeland condition, altered fire regimes and fire effects, and declines in sagebrush cover. Little is known about the long‐term impacts of fire in this ecosystem in areas where grazing pressure has been removed, few invasive species exist, and fire return intervals are maintained. In this study, we quantified vegetation composition prior to prescribed burning, 1 year following fire, and 17 years after fire in a native‐dominated Wyoming big sagebrush ecosystem at Hart Mountain National Antelope Refuge, Oregon, United States. Seventeen years following fire, the ecosystem was dominated by native herbaceous vegetation, with 8.3% cover of broad‐leaved forbs and bunchgrasses in the understory, compared to just 3.8% cover of native herbaceous vegetation in unburned controls. Invasive annual grass cover ranged from 0.2% to 8.4% across all treatments and years (P = 0.56). One year following fire, the distance from a randomly located point and the nearest mature sagebrush was 16.6 m, but by 17 years after the fire, that distance had decreased to 2.5 m. Seventeen years after fires, shrub cover was 0.4–4% in burned plots compared to 13–24% in unburned controls. Collectively, these data demonstrate that good condition ungrazed Wyoming big sagebrush plant communities exhibited resilience following fire and maintained a native‐dominated mosaic of shrubs, bunchgrasses, and forbs. Further, unburned control plots were dominated by woody vegetation and exhibited losses in herbaceous understory, possibly indicating that they are outside of their natural fire return interval. Our results illustrate that management of all habitat components, including natural disturbance and a mosaic of successional stages, is important for persistent resilience and that suppression of all fires in the sagebrush steppe may create long‐term losses of heterogeneity in good condition Wyoming big sagebrush ecosystems.

Pollen, ostracod and stable isotope records of palaeoenvironment and climate: Upper Miocene and Pliocene of the Çankırı Basin (Central Anatolia, Turkey)

An integrated stratigraphic study of Neogene lacustrine succession in the Çankırı Basin (Central Anatolia), combining pollen analysis, biostratigraphy and isotope analysis records variations in vegetation and depositional environment. The palynological analysis of the upper Miocene interval of the studied section reveals the existence of a coniferous forest. This flora reflects warm-temperate, humid climatic conditions. The pollen changes observed at the onset of the Pliocene are related to climatic changes. In the early Pliocene the vegetation changed to a mixed coniferous forest dominated by meso-microthermic trees (Cedrus and Cathaya) with a widespread herbaceous understory (Poaceae) sparcely interspersed with open areas occupied by Asteraceae whereas Abies and deciduous trees (Quercus, Carya, Juglans, Ulmus, Carpinus, Acer, etc.) are represented by lower percentages. This flora reflects a warm-temperate, relatively arid climate, reflecting the global warm climate of the Early Pliocene. The fluctuations in abundance of Tsuga may represent fluctuations in temperature. Climate analysis using the Coexistence Approach (CA) shows the presence of precipitation oscillations within the Pliocene. The identified ostracod assemblage indicates a dominance of fresh water conditions during the early late Miocene and of brackish water conditions during the late late Miocene while minor salinity oscillation is present throughout the section. The δ18Osulfate and 87Sr/86Sr isotopic ratios of non-marine gypsum are indistinguishable from the marine evaporites. This suggests recycling of older marine evaporites which is also supported by intense replacement of ostracods by gypsum.