Rangeland Plant Communities Research Articles

Growing Season Fires and Herbicide May not Be the Silver Bullet to Lespedeza cuneata Management

Invasive species are generally managed across rangelands to achieve livestock productivity and biodiversity maintenance objectives. The invasive legume Lespedeza cuneata (Dum. Cours.) G. Don. is managed across much of the Great Plains with aerially applied herbicides that target broadleaf forbs and dormant season (late March−early April) fire. It is hypothesized that altering fire timing to the growing season or integrating late-season herbicide into fire management may lead to more successful reduction of L. cuneata without negatively affecting rangeland plant communities. However, most of the literature outlining the effects of L. cuneata and its management is limited to small scale (< 100 m2), highly controlled studies that are not transferrable to large working rangelands. We manipulated eight large (333−766 ha) pastures managed with fire and grazing (i.e., pyric herbivory) to assess whether growing and dormant season fires, herbicide application, or the interactive effect of fire timing and herbicide reduced L. cuneata without negatively affecting broad rangeland plant composition (i.e., functional group cover) from 2019 to 2021. Our study was performed at two scales relevant to rangeland management: the pasture and burn patch scales. None of our treatments (i.e., fire timing, herbicide application, or the interaction of fire timing and herbicide) had a significant effect on L. cuneata canopy cover at either the pasture or patch scale. Our treatments also did not affect forb or shrub cover at the pasture or patch scales. Grass and sedge cover was significantly increased post herbicide at the patch scale, but not at the pasture scale. Grass and sedge cover was unaffected by any other treatment at both scales considered in this study. Our results add to nearly two decades of research, conducted elsewhere, that pyric herbivory alone may be sufficient to manage L. cuneata and promote rangeland biodiversity in the tallgrass prairie.

Reproductive compensatory photosynthesis in a semi-arid rangeland bunchgrass

While increased foliar photosynthesis is well documented across many plant species in response to diverse modes of herbivory, the compensatory ability of photosynthetically active reproductive structures is unknown. To address this, we partially defoliated basal florets in seed heads of crested wheatgrass (Agropyron cristatum (L.) Gaertn.), an exotic Eurasian perennial bunchgrass widely distributed across North American sagebrush steppe. We followed direct and indirect responses by tracking post-clipping photosynthesis in clipped basal and unclipped distal florets, respectively, and comparing these to similar florets on unclipped seed heads. Compensatory photosynthesis was apparent 24 h after clipping; over the pre-anthesis period, clipped basal floret photosynthesis was + 62%, stomatal conductance was + 82%, and PSII photochemical yield was − 39% of unclipped controls. After anthesis, intact florets distal to clipped florets had modestly higher photosynthetic rates compared to controls, while basal floret rates did not differ between treatments. Compensatory photosynthesis reduced intrinsic water use efficiency (iWUE; photosynthesis/stomatal conductance) 68–40% below controls over pre- and post-anthesis periods, respectively. Specific mass (dry mass/area) of clipped florets was − 15% of controls, while florets distal to these had specific mass 11% greater than distal or basal florets on unclipped seed heads. These results suggest damaged basal florets provided carbon to unaffected distal florets. This could explain crested wheatgrass’s ability to produce viable seeds under conditions limiting to native bunchgrasses, and presents a novel mechanism germane to the development of convergent drought- and grazing-tolerance traits important to arid and semi-arid rangeland plant community resilience to climate variability.

A 6-yr evaluation of prescribed-fire timing on yearling cattle growth performance and plant community dynamics on native tallgrass prairie in the Kansas Flint Hills

Abstract A 6-yr experiment was conducted to determine the effects of prescribed-fire season on stocker cattle growth performance and rangeland plant community characteristics in the Kansas Flint Hills. Eighteen pastures were grouped by watershed and each watershed was randomly assigned to 1 of 3 prescribed-fire treatments: spring (11 April ± 5.7 d), summer (25 August ± 6.2 d), or autumn (2 October ± 9.0 d). All burns were applied prior to grazing in years 1, 2, 3, and 5; however, no burns were applied in year 4 because of unfavorable burn conditions. Over 5 consecutive grazing seasons, 1,939 yearling stocker calves (initial BW = 281 ± 58.9 kg) were grazed from May to August at a targeted stocking density of 280 kg live-weight + ha−1. Beginning in June of 2018 (pretreatment), a permanent 100-m transect was established in each pasture and was used to determine plant-species composition using a modified step-point method. Forage biomass accumulation and root carbohydrate concentrations of 4 native tallgrass plant species were also measured. All data were analyzed as a completely randomized design using a mixed model. Average daily gain (ADG) was 0.05 to 0.07 kg greater (P = 0.02) for calves grazing spring-burned pastures compared with calves grazing summer- or autumn-burned pastures; however, ADG did not differ (P ≥ 0.55) between calves assigned to the summer or autumn prescribed-fire treatments. Basal cover of all graminoids and all forbs did not differ (P ≥ 0.30) among prescribed-fire treatments; however, basal cover of C3 grasses tended (P = 0.06) to be greater while basal cover of C4 grasses tended (P = 0.08) to be less in autumn-burned pastures compared with spring-burned pastures. Forage biomass accumulation did not differ (P = 0.58) among treatments. In addition, root starch or root water-soluble carbohydrate concentrations in big bluestem (Andropogon gerardii), little bluestem (Schizachyrium scoparium), Indiangrass (Sorghastrum nutans), or purple prairieclover (Dalea purpurea) did not differ (P ≥ 0.26) among prescribed-fire treatments. Overall, we interpreted these data to suggest that prescribed-fire timing had small influences on yearling stocker cattle growth performance and rangeland plant composition but did not influence forage biomass accumulation or root carbohydrate concentrations of key native tallgrass plant species in the Kansas Flint Hills.

Composition, distribution and environmental drivers of Mongolian rangeland plant communities

AbstractIn Mongolia, overgrazing and the resulting degradation of rangelands are recognized as serious issues. To address rangeland degradation, we sought to develop a broad-scale vegetation classification of Mongolian rangeland communities focusing on regional characteristics. Moreover, we sought to clarify the spatial distributions of communities and the environmental drivers of the distributions. Between 2012 and 2016, we surveyed vegetation in 278 plots (each 10 m × 10 m) in different regions of Mongolia (43–50° N, 87–119° E) in plots where grazing pressure is low relative to adjacent areas. The data were grouped into vegetation units using a modified two-way indicator species analysis (TWINSPAN). We then explored the regional characteristics of species compositions and community distributions, as well as relationships between distributions and climatic variables. The modified TWINSPAN classified the vegetation data into three cluster groups, each of which corresponds to a particular type of zonal vegetation (i.e. forest steppe, steppe and desert steppe). The aridity index was identified as an important driver of the distributions of all cluster groups, whereas longitude and elevation were important determinants of the distribution of clusters within cluster groups. Western regions, which are characterized by higher elevation and continentality compared with eastern regions, have lower mean temperature and precipitation during the wettest quarter, leading to differences in species composition within cluster groups. Regional differences in species composition reflect differences in phytogeographic origin. Thus, the framework of species composition and distributional patterns in Mongolian rangeland communities was demonstrated in relation to climatic and geographical factors.

Suppression of Potentilla recta by targeted goat grazing and aminopyralid on northern intermountain rangelands

AbstractSulphur cinquefoil (Potentilla recta L.) is an invasive perennial forb threatening rangelands in western North America. To identify best management strategies to control P. recta, we examined targeted goat (Capra hircus L.) grazing conducted once (pre-flowering) versus twice (pre-flowering and flowering and seed set), aminopyralid application, and integrated targeted grazing and aminopyralid as management strategies. We also examined the interaction between treatments and seasonality (spring and summer) and explored the possibility of off-target effects to non-target species. Two intermountain rangelands in British Columbia, Canada, were treated, one with targeted grazing treatments only and one with targeted grazing and herbicide treatments. Targeted grazing treatments were implemented in 2019 and 2020, and aminopyralid was applied once in 2019 at a rate of 56 g ai ha−1. Potentilla recta aboveground biomass and number of seed heads declined following targeted grazing treatments at both field sites in 2019 and 2020 when compared with the control, with no differences between targeted grazing treatments. In May 2020, before the implementation of targeted grazing for the second year, a decrease in P. recta biomass was not measured in the targeted grazing treatments, but biomass was 87% to 99% less in the herbicide-only and targeted grazing plus herbicide treatments. In July 2020, declines in biomass and seed heads in the herbicide-only and targeted grazing plus herbicide treatments did not differ from grazing twice, and aminopyralid effects did not differ among the three herbicide treatments. Further research is required to examine legacy effects of targeted goat grazing and aminopyralid on P. recta, establish reapplication frequency of treatments, and determine whether integrating targeted goat grazing and aminopyralid is needed in the long term to manage P. recta. A long-term study is also needed to examine off-target effects from targeted goat grazing and aminopyralid and ways to mitigate these effects to promote healthy native rangeland plant communities.

Rotational grazing increases purple prairie clover frequency in the rangeland plant communities under semi-arid environment

Purple prairie clover (PPC, Dalea purpurea Vent.) is a grazing tolerant perennial legume with good nutritional quality and is widely distributed across North America. Deferred rotational grazing (DR) and continuous grazing (CG) are the most widespread grazing systems on North American grasslands. We conducted a 10 yr grazing study to assess the effects of environmental factors and grazing on the frequency of PPC in plant communities. The results showed that the frequency of PPC decreased and then increased with increasing precipitation under CG (P &lt; 0.05), while there was no significant change under DR (P &gt; 0.05). Meanwhile, PPC frequency increased with temperature under DR (P &lt; 0.05), but did not change under CG (P &gt; 0.05). Both grazing systems and the number of grazing years had a significant effect on PPC frequency (P &lt; 0.05), and there is no interaction between those two factors (P &gt; 0.05). We found that from 2011 to 2020, the growth rate of PPC population is 18.24% and 11.69% per year under DR and CG grazing, respectively. Moreover, after 10 yr of grazing, the PPC increase in DR was 22.86% higher than that of CG. Thus, selecting the DR grazing system can increase PPC and is an effective practice for coping with environmental changes.

Changes in Rangeland Condition and Health of Palandoken Mountain Rangelands Over two Decades

Rangeland plant communities respond to environmental changes depending on management practices, climate, topography, and time. The objective of the study was to determine the changes in abundancy of functional plant groups, range condition score, class, and health with different topographical characteristics between 1993 and 2013. Trends in the investigated characteristics changed depending on aspect and topography. While the abundancy of decreaser and increaser plants decreased, invader plant abundancy increased over two decades. Similarly, range condition score, class, and health also declined in this period. The changes in investigated properties showed uneven distribution among the sites due to uncontrolled grazing practices and site characteristics. The results indicated that range degradation has been continued under current grazing practices. Therefore sustainable range management strategies should be put urgently into practice for the conservation of natural resources in the highland hilly rangelands of Turkey.

Environmental drivers of taxonomic and phylogenetic diversity patterns of plant communities in semi-arid steppe rangelands of North Africa

Since phytoecological and biodiversity studies deepen our understanding on ecosystem functioning and habitat health status of rangelands, this study analyzed the composition and plant taxonomic and phylogenetic diversity of semi-arid steppe vegetation communities in rangelands of northeastern Algeria. Based on 80 floristic samples, vegetation was analyzed using various species diversity parameters (incidence- and abundance-based diversity and similarity indices, rarefaction and extrapolation estimations). Sampling totaled 75,197 plant individuals that were classified into 63 species, 55 genera and 21 families, with predominance of Asteraceae (33.3%) and Fabaceae (14.3%) species. Rarefaction and extrapolation curves applied for the whole steppe vegetation showed that the expected species richness was stable and no rare species could be found when increasing the sample size. Generalized linear models showed that the variation of plant diversity parameters (alpha-biodiversity) was significant among the phytoecological groups individualized. The multiple factor analysis demonstrated that inter-relationships between the phytoecological groups result from characteristics of soil surface, vegetation indicators, and dominant plant species that influenced plant diversity indices. The qualitative and quantitative analysis of similarity (beta-biodiversity) revealed high resemblances (>50%) between these groups, indicating a spatial homogenization of plant communities, which are dominated by annual species. The variation of phylogenetic diversity, estimated using taxonomic structures (i.e. genus/species and family/species ratios) was related to local environmental conditions. Phylogenetic diversity increased with the increase in total vegetation cover and the average height of Halfa grass (Stipa tenacissima), but it was negatively correlated with land degradation indicators such as sand deposit sheets, bedrock outcrop, coarse-grained materials, and plant necromass or vegetation litter). This study demonstrated that despite the recorded plant diversity, the quality of rangelands in the study area was of a therophytic character (substantial level of annuals), indicating a state of land and vegetation degradation in rangelands of northeastern Algeria.

Livestock grazing‐induced large‐scale biotic homogenization in arid Mediterranean steppe rangelands

AbstractDespite many studies that have explored the effect of livestock grazing on plant communities, the response of species composition and diversity to livestock grazing in arid rangelands remains ambiguous. This study examined the effects of livestock grazing on plant communities in arid steppe rangelands of North Africa. Plant diversity of annual species, perennial species, and all species combined were measured and compared between grazed and grazing‐excluded areas. We also examined the relative importance of species turnover and community nestedness. Moreover, the effects of livestock grazing on beta diversity at local among transects and landscape among sites scales were examined using the multiplicative diversity partitioning. Results revealed that livestock grazing significantly decreased the alpha diversity of all species combined and the diversity of annual plants. Livestock grazing induced a shift in plant community composition where most species composition variation (~74%) was due to infrequent species replacement 'turnover' between the two management types rather than nestedness (~26%). Results revealed also that among transects, beta diversity was higher in grazed steppes than in grazing‐excluded steppes. Whereas, among sites, beta diversity was lower in grazed steppes compared to grazing‐excluded steppes. These findings suggest that livestock grazing in arid steppe rangelands increases the variation in plant species composition at a local spatial scale and engenders vegetation homogeneity at a landscape spatial scale. Therefore, the implementation of appropriate management practices such as short‐term grazing exclusion is mandatory to prevent these ecosystems from large‐scale biotic homogenization.

Evaluation of APEX modifications to simulate forage production for grazing management decision-support in the Western US Great Plains

ContextUnderstanding how grazing management decisions influence the productivity and composition of rangeland plant communities is essential for the development of effective strategies to sustainably produce multiple ecosystem goods and services. Informed with experimental measurements, simulation models can advance our understanding and stewardship of rangeland ecosystems. ObjectiveOur main objective was to evaluate the APEX (Agricultural Policy/Environmental eXtender) plant growth modules and grazing animal selectivity in simulating forage production using experimental data collected from both traditional season-long grazing and adaptive rotational grazing management on western rangelands. Specifically, we evaluated APEX's capability to simulate forage productivity and its response to soil types and climate conditions under grazing management options. MethodsCapitalizing on a comparative field study with 20 large pastures (> 123 ha each), APEX modifications were evaluated by comparing simulated forage production with experimental data. The field study evaluated traditional grazing (season long grazing on a single pasture) and an alternative grazing system that utilized collaborative adaptive rangeland management with stakeholders engaged in decision making (such as when and where to rotate a single herd). APEX was modified to include rotational grazing based on a user-defined sequence and automatic rotational grazing based on user-defined forage grazing limits and minimum/maximum grazing durations. Results and conclusionsThe APEX model was able to simulate the relative differences in forage production between grazing treatments, across years, and among soil types; however, APEX underestimated forage production in 2015 and 2017 due to overestimating drought stress for the warm season perennial grass functional group. Simulation of grazing management scenarios showed that the collaborative adaptive management decision criteria resulted in grazing durations that produced more forage than consistent 7- or 14-day rotation intervals. SignificanceThese modifications were needed to capture the complexity of semiarid environments and thus enhance APEX to better assess grazing management decisions on forage production in regions such as the Western US Great Plains.

Soil functional indicators in a mountain forest-rangeland mosaic of northern Iran

Soil plays an essential role in providing ecosystem services, especially in mountain ecosystems which are often considered as fragile and sensitive systems and commonly consist of a mosaic of forest and rangeland plant communities. The relationship between above-ground plant cover and the properties of soil organic and mineral layers in mountain areas are rarely studied. This research aimed to assess the effect of different land covers (i.e. forest, forest-rangeland ecotone, and rangeland) on soil functional indicators, i.e. fertility and biological activities, in the Hyrcanian region of northern Iran. We hypothesized that (i) the presence of tree cover enhances soil fertility and biological activities and creates hot spots (islands) of soil functional indicators especially in the topsoil, (ii) litter quality and organic matter fractions are the drivers for activities of soil organisms, nutrient cycles and transformation processes in mountain ecosystems. Litter (O-horizon including L, F and H layers) and mineral soil samples (in two separate depths of 0–10 cm and 10–20 cm) were taken using iron frames (30 × 30 cm). In total, 45 litter and 90 soil samples were transferred to the laboratory. Soil characteristic especially in the 0–10 cm depth, litter carbon (C), nitrogen (N) and C/N ratio were significantly affected by different land covers showing the maximum of soil organic C and microbial activity under forest. Our findings showed that the studied land covers, as well as litter and soil properties can be separated by PCA output. The first and second axes, accounted more than 50% of the explained variance in each of the studied soil depths. Soils with a better quality of litter (i.e. lower C/N ratio), higher values for organic matter fractions, soil fertility indicators and soil biological activities can be attributed to the forest. In contrast, positions of low soil fertility indicator values and biota abundance were imposed by forest-rangeland ecotone and rangeland. Although each land cover plays a prominent ecological role and takes its place in the evolutionary process, forests are essential because of their capacity to store and transform carbon and nutrients and to create hotspots identified by functional soil indicators. Based on our findings, soil functions decreased ranked in the order forest > forest-rangeland ecotone > rangeland, which can be assigned to the lower density of trees, and the amount of litter mass and litter quality. It can be concluded that tree covers have a prominent role in increasing soil functions, which should be given special consideration in the restoration of degraded mountain ecosystems.

Bunchgrass Root Abundances and Their Relationship to Resistance and Resilience of Burned Shrub-Steppe Landscape

Invasion of exotic annual grasses (EAG) and increased wildfire have led to an emphasis on managing rangeland plant communities for resistance to invasion and resilience to disturbances. In sagebrush steppe and similar rangelands, perennial bunchgrasses and particularly their roots are hypothesized to be primary contributors to resistance and resilience. We asked how bunchgrass root abundance relates to annual grass invasion and aboveground indicators of bunchgrass vigor that are more readily measured, such as plant height. We used a standardized US Department of Agriculture protocol for root measurement in 445 excavations made in 2016−2018 across a topographically and ecologically varied region of sagebrush steppe burned in the 2015 Soda fire in the Northern Great Basin, United States. Nearly all (99%) bunchgrasses, including seedlings, had deeper roots than the surrounding annual grasses (mean depth of annuals = 6.8 ± 3.3 cm), and 88% of seedlings remained rooted in response to the “tug test” (uprooting resistance to ~1 kg of upward pull on shoot), with smaller plants (mean height and basal diameters < 20 cm and < 2 cm, respectively) more likely to fail the test regardless of their root abundance. Lateral roots of bunchgrasses were scarcer in larger basal gaps (interspace between perennials) but were surprisingly not directly related to cover of surrounding EAG. However, EAG cover increased with the size of basal gaps and decreased with greater basal diameter of bunchgrass (in addition to prefire EAG abundance), albeit with a low r2. These results provide some support for 1) the importance of basal gaps and bunchgrass diameters as indicators of both vulnerability to annual grass invasion and bunchgrass root abundance and 2) the need for more detailed methods for root measurement than used here in order to substantiate their usefulness in understanding rangeland resistance and resilience.

Ventenata and Other Coexisting Exotic Annual Grass Control and Plant Community Response to Increasing Imazapic Application Rates

Ventenata (Ventenata dubia [Leers] Coss.) is an exotic annual grass that can invade intermountain rangeland plant communities, where it can form monotypic stands, degrade wildlife habitat, and reduce livestock forage. There is limited information on ventenata control in rangelands as it has only recently been identified as a substantial problem. Imazapic is a pre-emergent herbicide commonly used to control other exotic annual grasses and, therefore, is likely to control ventenata in rangelands. We evaluated five application rates of imazapic (0−175 g ae∙ha−1) on ventenata and other exotic annual grass control and plant community response at two rangeland sites in 2 yr (2014 and 2015). Imazapic reduced exotic annual grass (largely ventenata) cover and density, with greater control with increasing imazapic rates. Exotic annual grass density at the highest levels of control (82%−94%) was 184−299 plants∙m−2 the first yr after imazapic application. Exotic annual grasses fully recovered in the second or third yr after imazapic application. Bare ground generally increased with imazapic application. However, density of perennial vegetation (grasses and forbs) did not vary among treatments. Perennial vegetation cover generally did not increase with imazapic control of ventenata and other exotic annual grasses. Imazapic can control ventenata; however, even at the highest rates, control was not enough to shift the dominance from exotic annual species to perennial species. Integrating other treatments with imazapic application may be a strategy to improve ventenata control and increase perennial vegetation and will require further investigation. The difficulty and likely expense of achieving substantial and lasting control of ventenata suggest, similar to other exotic annual grasses, that preventing ventenata invasion and dominance should be a high management priority.

Effects of Feral Horse Herds on Rangeland Plant Communities across a Precipitation Gradient

Feral horses are widespread in the western United States, with the majority of feral horse herds found in the Great Basin. There is a federal mandate to manage these herds in order to maintain “ecological balance”; however, understanding of the specific effects of feral horse grazing on rangeland plant communities in this region is incomplete. To address this research gap, we utilized long-term grazing exclosures and fenceline contrasts to evaluate the impacts of feral horses on several plant community variables (diversity, richness, dominance, and biomass) and species composition. Because the effects of grazing can vary with site precipitation and productivity, we selected 5 sites from 4 different rangeland types (Great Basin Desert, Colorado Plateau, Rocky Mountain grassland, and mixed grass prairie) that spanned a mean annual precipitation gradient of 229 to 413 mm. Our results did not reveal a significant effect of feral horse grazing on plant community composition, species richness, diversity, evenness, or dominance. In contrast, total aboveground herbaceous biomass and grass biomass were significantly reduced with feral horse grazing, but these effects did not vary with mean annual precipitation. Our results suggest that, at least at the sites we studied, feral horses have affected the plant community by reducing herbaceous biomass but have not caused plant community shifts. Additional multisite studies, preferably with standardized exclosures and larger sample sizes, would increase our understanding of feral horse grazing effects and inform management of feral horse herds in the western United States.

Tuning the physicochemical properties of biochar derived from Ashe juniper by vacuum pressure and temperature

Ashe juniper is a problematic plant in central Texas due to rapid expansion causing the alteration of rangeland plant communities and hydrological landscapes. The thermochemical conversion of Ashe juniper into biochar with specific properties is a promising option for valorization of Ashe juniper. This study presents the effects of temperature (350, 450 and 520°C) and vacuum pressure (0.09, 0.7 and 3kPa) on physical and chemical properties of biochar produced by vacuum pyrolysis from Ashe juniper. We found that temperature had a major effect on the degree of carbonization and surface functionality, as well as the O/C and H/C ratios regardless of vacuum pressure. It was determined that the effect of vacuum pressure severity on product properties depends on pyrolysis temperature. In addition, the vacuum pressure was a crucial factor for controlling the surface area and porosity at each constant pyrolysis temperature. This work also demonstrated that the biochar from Ashe juniper under vacuum pyrolysis showed improved aromaticity and surface area compared to the biochar derived from other biomass. Biochar produced at 450 and 520°C showed potential application as an adsorbent, a catalyst support and a carbon sequestration agent. Methylene blue (MB) adsorption test confirmed that biochar produced at 450°C and 0.7kPa showed potential as an adsorbent.

Effectiveness of Burning, Herbicide, and Seeding Toward Restoring Rangelands in Southeastern North Dakota

Many rangelands in southeastern North Dakota are invaded by Kentucky bluegrass (Poa pratensis L.) and/or smooth brome (Bromus inermis Leyss.). It may be especially difficult for native species to reestablish in rangelands dominated by Kentucky bluegrass and/or smooth brome due to these species’ competitive advantages. Relatively few studies have specifically compared the effectiveness of methods intended to reduce competition from Kentucky bluegrass and/or smooth brome before seeding with native species in southeastern North Dakota. In our current study, we evaluated the effects of five restoration treatments: 1) control (no seeding or competition-reduction treatments), 2) interseed (native seeds drilled into the existing plant community), 3) spring burn before drill seeding native species, 4) glyphosate application before drill seeding native species, and 5) spring burn plus glyphosate application before drill seeding native species on a degraded rangeland plant community. We installed the five treatments in fifteen 40 × 100 m plots in 2010. In 2015, we sampled the vegetation within each plot to determine whether the restoration methods increased total and/or native warm-season grass biomass, reduced Kentucky bluegrass and/or smooth brome biomass, or increased grass species richness. Although none of our restoration treatments impacted Kentucky bluegrass biomass, each of our restoration treatments increased grass species richness over the control. Including a glyphosate application before seeding with natives also increased total biomass, reduced smooth brome biomass, and increased native warm-season grass species richness. Thus, we suggest that the glyphosate application was a worthwhile addition at this location because it resulted in additional improvements to the invasive-dominated plant community.

Herbivore effects on productivity vary by guild: cattle increase mean productivity while wildlife reduce variability.

Wild herbivores and livestock share the majority of rangelands worldwide, yet few controlled experiments have addressed their individual, additive, and interactive impacts on ecosystem function. While ungulate herbivores generally reduce standing biomass, their effects on aboveground net primary production (ANPP) can vary by spatial and temporal context, intensity of herbivory, and herbivore identity and species richness. Some evidence indicates that moderate levels of herbivory can stimulate aboveground productivity, but few studies have explicitly tested the relationships among herbivore identity, grazing intensity, and ANPP. We used a long-term exclosure experiment to examine the effects of three groups of wild and domestic ungulate herbivores (megaherbivores, mesoherbivore wildlife, and cattle) on herbaceous productivity in an African savanna. Using both field measurements (productivity cages) and satellite imagery, we measured the effects of different herbivore guilds, separately and in different combinations, on herbaceous productivity across both space and time. Results from both productivity cage measurements and satellite normalized difference vegetation index (NDVI) demonstrated a positive relationship between mean productivity and total ungulate herbivore pressure, driven in particular by the presence of cattle. In contrast, we found that variation in herbaceous productivity across space and time was driven by the presence of wild herbivores (primarily mesoherbivore wildlife), which significantly reduced heterogeneity in ANPP and NDVI across both space and time. Our results indicate that replacing wildlife with cattle (at moderate densities) could lead to similarly productive but more heterogeneous herbaceous plant communities in rangelands.

Downy Brome Control and Impacts on Perennial Grass Abundance: A Systematic Review Spanning 64 Years

Given the high cost of restoration and the underlying assumption that reducing annual grass abundance is a necessary precursor to rangeland restoration in the Intermountain West, United States, we sought to identify limitations and strengths of annual grass control methods and refine future management strategies. We systematically reviewed all published journal articles spanning a 64-yr period (1948−2012; n = 119) reporting data on research efforts to either directly or indirectly reduce the abundance of the most common invasive annual grass, downy brome (Bromus tectorum L.). The seven most common control methods studied were herbicide, burning, revegetation, woody removal, defoliation or grazing, soil disturbance, and soil amendment. In addition, the majority of control methods were 1) applied at scales of 10−100 m2, 2) sampled within small plots (i.e., 0.1−1.0 m2), 3) implemented only once, and 4) monitored at time scales that rarely exceeded 5 yr. We also performed summary analyses to assess how these control methods affect downy brome and perennial grass abundance (i.e., cover, density, biomass). We found conflicting evidence regarding the assumption that reducing downy brome abundance is necessary to enhance the growth and establishment of perennial grasses. All methods, with the exception of woody plant removal, significantly reduced downy brome in the short term, but downy brome abundance generally increased over time and only herbicide and revegetation remained reduced in the long term. Only burning, herbicide, and soil disturbance led to long-term increases in perennial grass abundance. We suggest that future research should prioritize a broader array of ecological processes to improve control efficacy and promote the reestablishment of desirable rangeland plant communities.

Performance of the Rangeland Hydrology and Erosion Model for runoff and erosion assessment on a semiarid reclaimed construction site

The ability to assess the impact of management actions on soil and water resources is crucial to sustainable land management. The Rangeland Hydrology and Erosion Model (RHEM) was developed as an assessment and decision support tool for resource management agencies and has been used to estimate soil erosion at national, regional, and local scales for both disturbed and undisturbed rangeland soil and vegetation conditions. In this paper, runoff, sediment, and microtopography data were collected during a series of rainfall simulation experiments aimed at evaluating the effectiveness of revegetation on a shrub-dominated post-construction hillslope where the soil has had time to reconsolidate. RHEM9s input parameters are simple to collect and consist of soil texture, slope configuration, and canopy and ground cover. Experimental results showed that a mix of the shrub species rabbitbrush (<i>Chrysothamnus nauseosus</i>) and the invasive annual grass cheatgrass (<i>Bromus tectorum</i>) were more effective at reducing runoff and soil loss than rabbitbrush alone. Plots with more than 45% of residue cover produced as much as 2.1 times less runoff and 16 times less sediments than those with less than 15% of litter. Microtopographic changes information allowed partitioning the erosion process into diffuse and concentrated flow processes. Analysis of this 3D data highlighted the central role of concentrated flow erosion in sediment delivery on rangeland hillslopes. RHEM9s performance as expressed by the coefficient of determination, <i>R</i>², and the Nash-Stucliffe Efficiency (NSE) was <i>R</i>² = 0.84 and NSE = 0.27 for runoff and <i>R</i>² = 0.81 and NSE = 0.26 for sediments. This study demonstrates that RHEM can be effectively used by land managers and project managers to estimate soil erosion as a function of precipitation event on construction sites that have been revegetated to rangeland plant communities.

Soil Characteristics Influence the Selection of Dominant Plant Genotypes Inhabiting Wadi Sudr, Egypt

Rangeland plant community and species composition are known to be related to specific soil properties. The current study investigated the ecological influence (soil characteristics) on the selection and distribution of ecological-related genotypes of dominant xerophyte species in WadiSudr of Egypt. AFLP analysis reflected the genetic profile of the samples species from two altitudinal ranges (up and midstream) and was compared statistically with the differences of their inhabiting soil characteristics on two depth levels (20 and 40 cm) using Mantel test. Correlation values (r) ranged from 0.585 - 0.778 when treating the physical and chemical properties of soil samples regardless its altitudinal area. The correlation confirms that the soil chemical and physical properties influence the selection of a certain genotypes of the dominant xerophytes plants collected from Wadi Sudr of Egypt to certain altitude, while depths at 20 and 40 cm play a key role in the early growth and then the colonization of the selected genotypes, respectively. More studies are needed to exactly test the role and the importance of each of the correlated property to the plant growth and colonization.