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At least 127 records · Page 7Linked to original sources
USGS2002

Peak fire temperatures and effects on annual plants in the Mojave Desert

Very little is known about the behavior and effects of fire in the Mojave Desert, because fire was historically uncommon. However, fire has become more frequent since the 1970s with increased dominance of the invasive annual grasses Bromus rubens and Schismus spp., and land managers are concerned about its ecological effect. In this paper, I describe patterns of peak fire temperature and their effect on annual plants in creosote bush scrub vegetation of the Mojave Desert. Temperatures were monitored among microhabitats and distances from the soil surface, and between spring and summer. Microhabitats ranged from high amounts of fuel beneath creosote bush ( Larrea tridentata ) canopies, to intermediate amounts at the canopy drip line, to low amounts in the interspaces between them. Distances from the soil surface were within the vertical range where most annual plant seeds occur (−2, 0, 5, and 10 cm). I also compare temperature patterns with postfire changes in soil properties and annual plant biomass and species richness to infer potential mechanisms by which fires affect annual plants. Peak fire temperatures were most affected by the microhabitat fuel gradient, and the effects of fire on annual plants varied among microhabitats. Beneath creosote bushes, lethal fire temperatures for annual plant seeds occurred above- and belowground, resulting in four postfire years of reduced annual plant biomass and species richness due most likely to seed mortality, especially of Bromus rubens and native forbs. At the canopy drip line, lethal fire temperatures occurred only aboveground, reducing annual plant biomass for 1 yr and species richness for 2 yr, and increasing biomass of Schismus sp., the alien forb Erodium cicutarium , and native annuals after 3 yr. Negligible changes were caused by fire in interspaces or between spring and summer. Fire effects models for creosote bush scrub vegetation must account for patterns of peak fire temperature along the shrub–intershrub gradient. The responses of annual plants to this gradient vary depending on the species composition of the seedling cohort, their microhabitat affinities, and their respective phenologic stages at the time of burning. Fire can temporarily reduce seed densities of Bromus rubens , but dominance of Schismus sp. may quickly increase above prefire levels.

Ecological Applications↗
USGS2013

Regional signatures of plant response to drought and elevated temperature across a desert ecosystem

The performance of many desert plant species in North America may decline with the warmer and drier conditions predicted by climate change models, thereby accelerating land degradation and reducing ecosystem productivity. We paired repeat measurements of plant canopy cover with climate at multiple sites across the Chihuahuan Desert over the last century to determine which plant species and functional types may be the most sensitive to climate change. We found that the dominant perennial grass, Bouteloua eriopoda, and species richness had nonlinear responses to summer precipitation, decreasing more in dry summers than increasing with wet summers. Dominant shrub species responded differently to the seasonality of precipitation and drought, but winter precipitation best explained changes in the cover of woody vegetation in upland grasslands and may contribute to woody-plant encroachment that is widespread throughout the southwestern United States and northern Mexico. Temperature explained additional variability of changes in cover of dominant and subdominant plant species. Using a novel empirically based approach we identified ‘‘climate pivot points’’ that were indicative of shifts from increasing to decreasing plant cover over a range of climatic conditions. Reductions in cover of annual and several perennial plant species, in addition to declines in species richness below the long-term summer precipitation mean across plant communities, indicate a decrease in the productivity for all but the most drought-tolerant perennial grasses and shrubs in the Chihuahuan Desert. Overall, our regional synthesis of long-term data provides a robust foundation for forecasting future shifts in the composition and structure of plant assemblages in the largest North American warm desert.

Ecology↗
USGS2011

On the brink of change: Plant responses to climate on the Colorado Plateau

The intensification of aridity due to anthropogenic climate change in the southwestern U.S. is likely to have a large impact on the growth and survival of plant species that may already be vulnerable to water stress. To make accurate predictions of plant responses to climate change, it is essential to determine the long‐term dynamics of plant species associated with past climate conditions. Here we show how the plant species and functional types across a wide range of environmental conditions in Colorado Plateau national parks have changed with climate variability over the last twenty years. During this time, regional mean annual temperature increased by 0.18°C per year from 1989–1995, 0.06°C per year from 1995–2003, declined by 0.14°C from 2003–2008, and there was high interannual variability in precipitation. Non‐metric multidimensional scaling of plant species at long‐term monitoring sites indicated five distinct plant communities. In many of the communities, canopy cover of perennial plants was sensitive to mean annual temperature occurring in the previous year, whereas canopy cover of annual plants responded to cool season precipitation. In the perennial grasslands, there was an overall decline of C 3 perennial grasses, no change of C 4 perennial grasses, and an increase of shrubs with increasing temperature. In the shrublands, shrubs generally showed no change or slightly increased with increasing temperature. However, certain shrub species declined where soil and physical characteristics of a site limited water availability. In the higher elevation woodlands, Juniperus osteosperma and shrub canopy cover increased with increasing temperature, while Pinus edulis at the highest elevation sites was unresponsive to interannual temperature variability. These results from well‐protected national parks highlight the importance of temperature to plant responses in a water‐limited region and suggest that projected increases in aridity are likely to promote grass loss and shrub expansion on the Colorado Plateau.

Utah↗
USGS2006

Vascular Plant and Vertebrate Inventory of Saguaro National Park, Rincon Mountain District

Executive Summary This report summarizes the results of the first comprehensive inventory of plants and vertebrates at the Rincon Mountain District (RMD) of Saguaro National Park, Arizona. From 2001 to 2003 we surveyed for vascular plants and vertebrates (amphibians, reptiles, birds, and mammals) at the district to document the presence of species within its boundaries. Park staff also surveyed for medium and large mammals using infrared-triggered cameras from 1999 to 2005. This report summarizes the methods and results of these two efforts. Our spatial sampling design was ambitious and was one of the first of its kind in the region to colocate study sites for vegetation and vertebrates using a stratified random design. We also chose the location of some study sites non-randomly in areas that we thought would have the highest species richness. Because we used repeatable study designs and standardized field methods, these inventories can serve as the first step in a biological monitoring program for the district. We also provide an important overview of most previous survey efforts in the district. We use data from our inventory and other surveys to compile species lists and to assess inventory completeness. With the exception of plants, our survey effort was the most comprehensive ever undertaken in the district. We recorded a total of 801 plant and vertebrate species, including 50 species not previously found in the district (Table 1) of which five (all plants) are non-native species. Based on a review of our inventory and past research at the district, there have been a total of 1,479 species of plants and vertebrates found there. We believe inventories for all taxonomic groups are nearly complete. In particular, the plant, amphibian and reptile, and mammal species lists are the most complete of any comparably large natural area of the 'sky island' region of southern Arizona and adjacent Mexico. For each taxon-specific chapter we discuss patterns of species richness and environmental determinants of these patterns. For all groups except medium and large mammals, the low elevation stratum (<4,000 feet) contained the highest species richness, after accounting for differences in survey effort among strata. This is consistent with known patterns of species richness in the sky island mountain ranges. Using data on relative abundance for plants and birds, we were able to identify a number of distinct ecological communities, which were consistent with known patterns in the sky islands. Our review of species lists and park records reveals that the district has lost species, particularly plants and mammals, in the past few decades. Because of the district's close proximity to the rapidly growing city of Tucson, there are a number of development-related threats that could cause additional species loss or decline in abundance of some species. In particular, the increasing groundwater pumping near Rincon Creek, the most species-rich area in the park, is likely to impact the unique riparian vegetation and animals of that area. We discuss this and other demands on the ecological integrity of the district. We also recommend additional inventory, monitoring, and research studies.

Open-File Report↗
USGS2006

Salt marsh dieback in coastal Louisiana: Survey of plant and soil conditions in Barataria and Terrebonne basins, June 2000-September 2001

Sudden and extensive dieback of the perennial marsh grass, Spartina alterniflora Loisel (smooth cordgrass), which dominates regularly flooded salt marshes along the Gulf of Mexico and Atlantic coastlines, occurred in the coastal zone of Louisiana. The objectives of this study were to assess soil and plant conditions in dieback areas of the Barataria-Terrebonne estuarine system as well as vegetative recovery during and after this dieback event. Multiple dieback sites were examined along 100 km of shoreline from the Atchafalaya River to the Mississippi River during the period from June 2000 through September 2001. The species primarily affected was S. alterniflora; sympatric species such as Avicennia germinans (L.) Stearn (black mangrove) and Juncus roemerianus Scheele (needlegrass rush) showed no visible signs of stress. The pattern of marsh dieback was distinctive with greatest mortality in the marsh interior, suggesting a correlation with local patterns of soil chemistry and/or hydrology. Little or no expansion of dieback occurred subsequent to the initial event, and areas with 50 percent or less mortality in the fall of 2000 had completely recovered by April 2001. Recovery was slower in interior marshes with 90 percent or greater mortality initially. However, regenerating plants in dieback areas showing some recovery were robust, and reproductive output was high, indicating that the causative agent was no longer present and that post-dieback soil conditions were actually promoting plant growth. Stands of other species within or near some dieback sites remained largely unchanged or expanded (A. germinans) into the dead salt marsh. The cause of the dieback is currently unknown. Biotic agents and excessive soil waterlogging/high sulfide were ruled out as primary causes of this acute event, although they could have contributed to overall plant stress and/or interacted with the primary agent to cause plant mortality. Our observations over the 15 month study specifically do not support the contention that dieback was caused by excessive grazing by Littoraria irrorata (marsh periwinkle). Instead, the data show that snails were responding to plant mortality and played an important role in rapid degradation of dead material in some areas. The dieback event was coincident with an extreme drought, low river discharge, and low sea level. These conditions could have caused plant mortality by directly decreasing water availability, increasing salinity, and/or causing oxidation and acidification of soils. The latter scenario was supported by findings of higher pyrite and acid-extractable aluminum and iron, higher acidification potential of dieback soils, and higher concentrations of aluminum and iron in dieback plant tissues (indicating uptake of potentially toxic metals) when compared to reference marshes showing no dieback. The implication of these findings is that periodic weather extremes may play a greater role in shaping coastal plant communities than has previously been recognized. Although such events may not be controlled directly, the resilience and recovery of the system may be altered by management. Such considerations will become increasingly important as global climate changes and human pressures in the coastal zone grow.

Louisiana↗
USGS2006

Field-based evaluation of two herbaceous plant community composition sampling methods for long-term monitoring in Northern Great Plains National Parks

The Northern Great Plains Inventory & Monitoring (I&M) Network (Network) of the National Park Service (NPS) consists of 13 NPS units in North Dakota, South Dakota, Nebraska, and eastern Wyoming. The Network is in the planning phase of a long-term program to monitor the health of park ecosystems. Plant community composition is one of the 'Vital Signs,' or indicators, that will be monitored as part of this program for three main reasons. First, plant community composition is information-rich; a single sampling protocol can provide information on the diversity of native and non-native species, the abundance of individual dominant species, and the abundance of groups of plants. Second, plant community composition is of specific management concern. The abundance and diversity of exotic plants, both absolute and relative to native species, is one of the greatest management concerns in almost all Network parks (Symstad 2004). Finally, plant community composition reflects the effects of a variety of current or anticipated stressors on ecosystem health in the Network parks including invasive exotic plants, large ungulate grazing, lack of fire in a fire-adapted system, chemical exotic plant control, nitrogen deposition, increased atmospheric carbon dioxide concentrations, and climate change. Before the Network begins its Vital Signs monitoring, a detailed plan describing specific protocols used for each of the Vital Signs must go through rigorous development and review. The pilot study on which we report here is one of the components of this protocol development. The goal of the work we report on here was to determine a specific method to use for monitoring plant community composition of the herb layer (< 2 m tall).

Open-File Report↗
USGS2009

Vascular Plant and Vertebrate Inventory of Chiricahua National Monument

This report summarizes the results of the first comprehensive inventory of vascular plants and vertebrates at Chiricahua National Monument (NM) in Arizona. This project was part of a larger effort to inventory vascular plants and vertebrates in eight National Park Service units in the Sonoran Desert Network of parks in Arizona and New Mexico. In 2002, 2003, and 2004 we surveyed for plants and vertebrates (amphibians, reptiles, birds, and mammals) at Chiricahua NM to document the presence of species within the boundaries of the monument. Because we used repeatable study designs and standardized field methods, these inventories can serve as the first step in a biological monitoring program for the monument. This report is also the first summary of previous research from the monument and therefore it provides an important overview of survey efforts to date. We used data from our inventory and previous research to compile complete species lists for the monument and to assess inventory completeness. We recorded a total of 424 species, including 37 not previously found at the monument (Table 1). We found 10 species of non-native plants and one non-native mammal. Most non-native plants were found along the western boundary of the monument. Based on a review of our inventory and past research at the monument, there have been a total of 1,137 species of plants and vertebrates found at the monument. We believe the inventories of vascular plants and vertebrates are nearly complete and that the monument has one of the most complete inventories of any unit in the Sonoran Desert Network. The mammal community at the monument had the highest species richness (69 species) and the amphibian and reptile community was among the lowest species richness (33 species) of any park in the Sonoran Desert Network. Species richness of the plant and bird communities was intermediate. Among the important determinants of species richness for all groups is the geographic location of the monument at the intergrades between the Chihuahuan and Sonoran deserts with influences from the Great Plains and Madrean ecological provinces. The diversity of plants results from a wide variety of soil types and aspects (from cool, moist canyons to semi-desert grasslands to pine forests). In turn, the vertebrate communities respond to this diversity of vegetation, topography, and microsites. For example, for each taxonomic group we found that some species were only associated with a single community type, most often the riparian areas or semi-desert grasslands. The area of highest species richness for most groups was the western-most portion of Bonita Canyon. The low species richness observed in the amphibian and reptile community was likely because the monument is at the elevational edge of the more species-rich semi-desert grasslands. This report includes management implications from our work and suggestions for how the monument staff might better maintain or enhance the unique biological resources of the monument. We suggest additional inventory, monitoring, and research studies and we identify components of our effort that could be improved upon, either through the application of new techniques (e.g., establishment of vegetation monitoring plots) or by extending the temporal and/or spatial scope of our work.

Open-File Report↗
USGS2003

Avian use of natural versus planted woodlands in eastern South Dakota, USA

We compared avian use of naturally occurring and planted woodlands in eastern South Dakota, USA, to evaluate whether planted woodlands support the same avian communities as natural woodlands. A stratified cluster sample was used to randomly select 307 public areas in which to survey planted (n = 425) and natural (n = 99) woodland patches. Eighty-five species of birds were detected in eastern South Dakota woodlands, 36 of which occurred in ??? 5 of 524 patches surveyed. The probability of occurrence for 8 of 13 woodland-obligate species was significantly greater in natural woodland habitats than in planted woodland habitats. Four of these species breed in relatively high numbers in eastern South Dakota. Only one woodland-obligate occurred less frequently in natural woodlands. Probability of occurrence for 6 edge and generalist species, including the brown-headed cowbird (Molothrus ater [Boddaert]), was significantly higher in planted woodlands. The avian community of planted woodlands was dominated by edge and generalist species. The homogeneous vegetation structure typical of planted woodlands does not appear to provide the habitat characteristics needed by woodland-obligate birds. We conclude that planted woodlands do not support significant numbers of woodland-obligate species and may negatively impact grassland-nesting birds by attracting edge and generalist bird species and predators into previously treeless habitats. Planted woodlands cannot be considered equal replacement habitats for natural woodland patches when managing for nongame woodland bird species. However, the preservation and maintenance of natural woodlands is critical for woodland-obligate species diversity in the northern Great Plains.

South Dakota↗
USGS2021

Evaluation of a “trace” plant density score in LTRM vegetation monitoring

The Long Term Resource Monitoring (LTRM) element of the Upper Mississippi River Restoration program employs a harvest method for sampling submersed aquatic vegetation (SAV) whereby a rake is dragged ~1.5 m over the substrate and plant materials are retrieved. “Plant density” (PD) scores indicate SAV abundance and are based on the amount of plant material collected on the teeth of the rake. Standard PD scores are ordered, whole numbers from 0 (no SAV on the rake) to 5 (80-100% of rake teeth full) and are assigned at each subsite for all species combined and for each individual species. In LTRM monitoring between 1998 and 2018, ~73% of non-zero, all-species-combined PD scores were 1s, and ~89% of individual SAV species were 1s. The preponderance of PD = 1 scores along with the wide range of fresh mass represented by PD = 1 (quantified in Drake and Lund 2020) limits inference about SAV abundance from LTRM monitoring data. Field personnel noted that small plant fragments comprised a substantial fraction of PD = 1 observations and proposed a modification of the existing LTRM methods where PD = 1 was subdivided to include “trace” scores to represent such small fragments. Trace was defined as PD = 0.08, indicating a maximum of 1 of 13 gaps in the sampling rake filled to the level of an original PD = 1. Amounts of plant material greater than PD = 0.08 and up to the original score of 1 were defined PD = +1. This study used field data collected in 2018 (scoring and fresh weights of scored plant materials) from 136 vegetated sites in Pools 4, 8 and 13 to evaluate the proposed subdivision and to examine among-pool differences in PD data. In the study data, 33% of all-species-combined observations and 69% of species (grouped by morphology) that would previously have received a score of 1 were classified as PD = 0.08. PD scores of 0.08, +1, and 2-3 represented statistically distinct amounts of fresh mass in rake samples. There were systematic differences in the mass of SAV reflected by PD score based on plant morphology and species composition. The mean fresh mass of plant materials assigned a given PD score varied among the three pools, suggesting bias attributable to personnel. To reduce this bias in future data collection efforts, the field crews incorporated a calibration of plant density scores in annual field training. The results presented here describe how including a trace PD score in LTRM data collection improves the description of SAV abundance and consequently estimates of biomass from those PD scores. LTRM vegetation crews have recorded trace scores in annual sampling since 2019 as extra information (i.e. which does not change the LTRM data stream as 0.08 and +1 scores can still be combined for PD=1). Trace data are not currently available to outside users through the LTRM data browser but are available from vegetation component personnel upon request.

Long Term Resource Monitoring Technical Report↗
USGS1970

Common marsh plants of the United States and Canada

This is the fourth of a series of publications on field identification of North American marsh and water plants. It describes the emergent and semiemergent plants most likely to be found in inland and coastal marshes. It omits hundreds of uncommon marsh plants and plants less characteristic of marshes than of marsh edges, lake and stream shores, or wet meadows. The first of the series, "Pondweeds and Pondweedlike Plants of Eastern North America," Circular 187, was broadened in scope as Resource Publication 44, "Underwater and Floating-leaved Plants of the United States and Canada," and is superseded by it. The present publication, widens the scope of "Bulrushes and Bulrushlike Plants of Eastern North America," Circular 221, and contains most of the species listed therein. This guide is designed for identification of marsh plants without recourse to technical botanical keys. To use it, read pages 1 to 4 and then look at the drawings. To identify a plant, find the group in which it fits, then find a drawing and description that match it.

Resource Publication↗
USGS2024

Hotspots of biogeochemical activity linked to aridity and plant traits across global drylands

Perennial plants create productive and biodiverse hotspots, known as fertile islands, beneath their canopies. These hotspots largely determine the structure and functioning of drylands worldwide. Despite their ubiquity, the factors controlling fertile islands under conditions of contrasting grazing by livestock, the most prevalent land use in drylands, remain virtually unknown. Here we evaluated the relative importance of grazing pressure and herbivore type, climate and plant functional traits on 24 soil physical and chemical attributes that represent proxies of key ecosystem services related to decomposition, soil fertility, and soil and water conservation. To do this, we conducted a standardized global survey of 288 plots at 88 sites in 25 countries worldwide. We show that aridity and plant traits are the major factors associated with the magnitude of plant effects on fertile islands in grazed drylands worldwide. Grazing pressure had little influence on the capacity of plants to support fertile islands. Taller and wider shrubs and grasses supported stronger island effects. Stable and functional soils tended to be linked to species-rich sites with taller plants. Together, our findings dispel the notion that grazing pressure or herbivore type are linked to the formation or intensification of fertile islands in drylands. Rather, our study suggests that changes in aridity, and processes that alter island identity and therefore plant traits, will have marked effects on how perennial plants support and maintain the functioning of drylands in a more arid and grazed world.

Nature Plants↗
USGS2006

Commissioned Review. Carbon: freshwater plants

δ13C values for freshwater aquatic plant matter varies from −11 to −50‰ and is not a clear indicator of photosynthetic pathway as in terrestrial plants. Several factors affect δ13C of aquatic plant matter. These include: (1) The δ13C signature of the source carbon has been observed to range from +1‰ for HCO3− derived from limestone to −30‰ for CO2 derived from respiration. (2) Some plants assimilate HCO3−, which is –7 to –11‰ less negative than CO2. (3) C3, C4, and CAM photosynthetic pathways are present in aquatic plants. (4) Diffusional resistances are orders of magnitude greater in the aquatic environment than in the aerial environment. The greater viscosity of water acts to reduce mixing of the carbon pool in the boundary layer with that of the bulk solution. In effect, many aquatic plants draw from a finite carbon pool, and as in terrestrial plants growing in a closed system, biochemical discrimination is reduced. In standing water, this factor results in most aquatic plants having a δ13C value similar to the source carbon. Using Farquhar's equation and other physiological data, it is possible to use δ13C values to evaluate various parameters affecting photosynthesis, such as limitations imposed by CO2 diffusion and carbon source.

Plant, Cell & Environment↗
USGS2017

Riparian plant composition along hydrologic gradients in a dryland river basin and implications for a warming climate

Droughts in dryland regions on all continents are expected to increase in severity and duration under future climate projections. In dryland regions, it is likely that minimum streamflow will decrease with some perennial streams shifting to intermittent flow under climate-driven changes in precipitation and runoff and increases in temperature. Decreasing base flow and shifting flow regimes from perennial to intermittent could have significant implications for stream-dependent biota, including riparian vegetation. In this study, we asked, how do riparian plant communities vary along wet-to-dry hydrologic gradients on small (first–third order) streams? We collected data on geomorphic, hydrologic, and plant community characteristics on 54 stream sites ranging in hydrology from intermittent to perennial flow across the Upper Colorado River Basin (284,898 km 2 ). We found that plant communities varied along hydrologic gradients from high to low elevation between streams, and perennial to intermittent flow. We identified indicator species associated with different hydrologic conditions and suggest how plant communities may shift under warmer, drier conditions. Our results indicate that species richness and cover of total, perennial, wetland, and native plant groups will decrease while annual plants will increase under drying conditions. Understanding how plant communities respond to regional drivers such as hydroclimate requires broad-scale approaches such as sampling across whole river basins. With increasingly arid conditions in many regions of the globe, understanding plant community shifts is key to understanding the future of riparian ecosystems.

Upper Colorado River Basin↗
USGS2017

Topographic, edaphic, and vegetative controls on plant-available water

Soil moisture varies within landscapes in response to vegetative, physiographic, and climatic drivers, which makes quantifying soil moisture over time and space difficult. Nevertheless, understanding soil moisture dynamics for different ecosystems is critical, as the amount of water in a soil determines a myriad ecosystem services and processes such as net primary productivity, runoff, microbial decomposition, and soil fertility. We investigated the patterns and variability in in situ soil moisture measurements converted to plant-available water across time and space under different vegetative cover types and topographic positions at the Marcell Experimental Forest (Minnesota, USA). From 0 – 228.6 cm soil depth, plant-available water was significantly higher under the hardwoods (12%), followed by the aspen (8%) and red pine (5%) cover types. Across the same soil depth, toeslopes were wetter (mean plant-available water = 10%) than ridges and backslopes (mean plant-available water was 8%), although these differences were not statistically significant ( p < 0.05). Using a mixed model of fixed and random effects, we found that cover type, soil texture, and time were related to plant-available water and that topography was not significantly related to plant-available water within this low-relief landscape. Additionally, during the three-year monitoring period, red pine and quaking aspen sites experienced plant-available water levels that may be considered limiting to plant growth and function. Given that increasing temperatures and more erratic precipitation patterns associated with climate change may result in decreased soil moisture in this region, these species may be sensitive and vulnerable to future shifts in climate.

Ecohydrology↗
USGS2021

Seasonal impoundment alters patterns of tidal wetland plant diversity across spatial scales

Understanding patterns of biodiversity is a key goal of ecology and is especially pressing in the current human‐caused biodiversity crisis. In wetland ecosystems, human impacts are centered around hydrologic manipulation including the common practice of wetland diking and impoundment. Constraining how wetland management influences plant biodiversity patterns across spatial scales will provide information on how best to modify actions to preserve biodiversity and ecosystem function in managed wetlands. Here, we compare patterns of plant diversity and species presence, abundance, and community composition at several spatial scales among tidal wetlands along an estuarine salinity gradient and managed wetlands that were formerly tidal. Managed impounded wetlands had decreased alpha and gamma diversity of rare species, with less than 60% of the species richness found in tidal brackish wetlands at several spatial scales. There was little change in the overall pattern of alpha, beta, and gamma diversity for common species in impounded wetlands; however, dominant tidal brackish species, primarily perennial rhizomatous graminoids, were replaced with management target plants and non‐native annual grasses in impounded wetlands. This species replacement led to over 60% of impounded sites being classified as containing novel plant assemblages. An additional 25% of impounded sites were classified as containing tidal saline plant assemblages, suggesting potential soil salinization. Along the estuarine gradient, patchiness and codominance of common plant species drove high diversity and turnover in tidal brackish wetlands, while it remains unclear whether tidal fresh or brackish wetlands maximize rare plant diversity. With reduced species richness, altered functional dominants, and novel or saline assemblages, impounded brackish wetlands may require careful water management to balance native plant biodiversity, associated ecosystem processes, and waterfowl requirements.

California↗
USGS2023

Decoupling of species and plant communities of the U.S. Southwest: A CCSM4 climate scenario example

Climate change is predicted to alter the current climate suitability under which plant species and communities occur. Predictions of change have focused on individual species or entire communities, but theory indicates plants will not respond uniformly to climate change within or between communities. We developed models of the current climate suitability (the baseline) of 66 plant species characteristic of 29 plant communities of the arid Southwest, made predictions of climate suitability for the species under two climate change scenarios for the years 2041–2060 (Community Climate System Model version 1.4 [CCSM4] global climate model [GCM], Representative Concentration Pathway [RCP] 4.5 and 8.5 scenarios), and calculated changes in suitability between the future scenarios and baseline for each species. Climate change exposure for the entire community was then evaluated as the composite change of the predicted future climate suitability of the communities' characteristic species. Loss of 25% or more of favorable climate suitability was predicted for 39 (RCP4.5) and 51 (RCP8.5) species within their communities. The proportion of the study area with all species in a community having unfavorable suitability was 17.9% (RCP4.5) and 21.3% (RCP8.5) compared to 6.2% for baseline. We show that suitable climates for species within a plant community are not expected to be a single community-wide trajectory, but rather changes in climate suitability will be unique to the species and not experienced uniformly across the extant communities. This decoupling of plant species within their traditional plant communities may lead to a cascade of unanticipated ecological responses and unprecedented challenges to resource management. Our study results can inform hypotheses of the future successional track of plant communities, characteristic species, and the decisions resource managers must make for management.

Ecosphere↗
USGS2019

Soil texture and precipitation seasonality influence plant community structure in North American temperate shrub steppe

In drylands, the coexistence of grasses and woody plants has been attributed to soil‐water resource partitioning. Soil texture and precipitation seasonality can influence the amount and distribution of water in the soil, and their interaction may play an important role in determining the relative importance of grasses and woody plants. We investigated the influence of this interaction on plant functional types across a broad range of precipitation regimes and soil textures in western North America by analyzing plant‐cover data collected at 2,084 plots that included the widespread shrub big sagebrush ( Artemisia tridentata Nutt.). We characterized how the significance of the inverse‐texture effect varies across soil conditions by quantifying relationships between precipitation and foliar cover on finer‐ vs. coarser‐textured soils across a range of potential texture divisions represented by sand content. We found evidence of the inverse‐texture effect for every plant functional type (except for cheatgrass) that we examined with at least one component of precipitation (annual, warm, or cold season), and provide the first evidence for this effect in locations with cold‐season‐dominated precipitation regimes. The texture and precipitation combinations that exhibited the inverse‐texture effect varied with plant functional type, presumably because of effects of soil texture on water availability at different soil depths with season. Furthermore, we found an inverse‐texture effect that was remarkably similar for shrub cover with cold‐season precipitation and grass cover with warm‐season precipitation. These results provide new insight into how the inverse‐texture effect interacts with precipitation seasonality to influence plant functional type composition in drylands, and further suggest that quantifying the soil‐texture division at which the inverse‐texture effect is relevant under a given set of environmental conditions may provide support for the effect across dryland plant communities.

Arizona, California, Colorado, Idaho, Montana, New↗
USGS1990

Homestead tree planting in two rural Swazi communities

Tree planting practices were investigated on a total of 95 homesteads in two communities in rural Swaziland. Information was also collected on socioeconomic characteristics of the homesteads. In both the study areas, Sigombeni and Bhekinkosi, there was considerable variation amongst individual homesteads in size, relative wealth (as indicated by cattle and motor vehicle ownership), and amount and types of trees planted. Eighty-five percent of all homesteads in Sigombeni and 73% in Bhekinkosi had planted at least one tree. Common forms of planting included small woodlots, fruit trees, and ornamentals. Virtually all the woodlots consisted of two introduced wattle species (Acacia mearnsii and A. decurrens). The most commonly planted fruit trees were avocados, bananas, and peaches. No complex or labor-intensive agroforestry practices (such as maize/leucaena intercropping) were observed. There was some evidence that the poorest and newest homesteads were the least likely to have planted any trees and that the richest homesteads were the most likely to have planted woodlots. The results indicate that forestry research and extension efforts should take into account homestead characteristics, and strive to offer a range of tree planting options that vary in input requirements, labor needs, and complexity.

Agroforestry Systems↗