Abundance Of Grasses Research Articles

Active restoration after three decades: Seed addition increases native dominance compared to landscape‐scale secondary succession

Abstract Active restoration often aims to accelerate ecosystem recovery. However, active restoration may not be worthwhile if its effects are overwhelmed by changes that occur passively. Moreover, it can be challenging to separate the effects of passive processes, such as dispersal and natural succession, from active restoration efforts. We assess the 24‐year impact of actively restoring a Minnesota old‐field grassland via seed addition of native tallgrass prairie species. We compared the abundance of four functional plant groups in actively restored plots against abundances in three reference classes: (1) unrestored plots undergoing passive recovery within the same old field, (2) passively recovering plots in two nearby old fields of similar age and (3) a chronosequence of 21 old fields within the same landscape. Active restoration led to a higher abundance of native grasses and forbs in the 36 m2 treatment plots. Seed addition was more effective if the original vegetation was first removed using herbicide, burning and tilling. However, long‐term conclusions about the efficacy of active restoration varied widely depending on the choice of reference class. In our small‐scale restoration experiment, native abundance was similarly high in both the actively restored and reference plots after 24 years, suggesting either (1) passive recovery or (2) local dispersal of native species from nearby treatment plots (i.e. cross‐contamination). In contrast, a comparison with two nearby reference fields suggested active restoration resulted in much higher native abundance relative to passive recovery. A smaller, positive effect was detected when we compared actively restored plots to the chronosequence of old fields. In the chronosequence, many passively recovering old fields had transitioned to native grass dominance naturally, although active restoration appeared to increase native forb abundance. Synthesis and applications: Our findings highlight the importance of using scale‐appropriate references for assessing the efficacy and need for active restoration. Comparing actively restored plots with the surrounding landscape, we found that active restoration and passive recovery led to similar plant communities after 24 years. Because local dispersal from actively restored sites can nearby references, caution should be exercised when evaluating long‐term restoration projects using only small‐scale experiments.

Long‐term and landscape impacts of buffel grass on arid plant communities: Ecosystem shifts and acceleration by fire

AbstractPlant invasions drive biodiversity loss, transform ecosystems, and promote positive‐feedback cycles between invasion and fire. However, the long‐term impacts of invasive grasses across landscapes with diverse plant communities and interactions with fire are poorly known. Our objectives were to examine whether buffel grass (Cenchrus ciliaris), a globally significant plant invader, altered the abundance of understory and overstory plants, homogenized plant composition, and shifted ecosystems from woodlands to grassland and to explore interrelationships between invasion and fire. We combined two methodological approaches to assess invasion spread and impacts of buffel grass in the Aṉangu Pitjantjatjara Yankunytjatjara (APY) Lands of arid central Australia: a before‐after‐control‐impact (BACI) experiment over 25 years at 15 sites and a paired‐plot (randomized‐block) experiment at 18 sites. Both experiments spanned two geographic regions and multiple vegetation communities situated on flat plains and rocky hills. We used generalized linear mixed models to analyze predictions about plant abundance and permutational multivariate ANOVA (PERMANOVA) and permutational multivariate analysis of dispersion (PERMDISP) to examine changes in community composition. Fire and invasion interactions were explored using fire history or the relative fire tolerance of plant species as covariates, predictors, or responses. Fire interacted with the invasion process in multiple ways. Invaded sites had burnt more frequently and recently than native sites in one region, and where propagules were present in 1995, buffel grass abundance increased most when fires ensued. Abundance of understory plant functional groups (native grasses, ferns, and vines) decreased with invasion, and understory shrubs decreased due to frequent fires in invaded sites. Overstory composition shifted from fire‐sensitive species toward fire‐tolerant species, but this was not directly attributable to invasion. Partial evidence for ecosystem regime shifts included homogenization of understory communities in invaded rocky hills, and an increase in woody shrub cover at native but not invaded sites over 25 years, resulting in a 5% cover difference by 2019. Impacts were detected across heterogeneous ecological communities at a scale not previously tested amongst high background community variability. Although invasion is not dependent on fire, the acceleration of invasion spread and impacts with fire is a critical consideration for future research and management of grass invaders.

Structure of Ground Vegetation and Natural Regeneration of Tree Species in 12- to 15-Year-Old Bilberry Pine Forest-Clear-cut Complex of Middle Taiga Subzone.

Logging in mature stands where part of the forest is harvested in one or several cuts and part is retained (clearcutting and alternate strip cutting) results in the formation of an ecotone complex (EC), which includes a forest (F) zone, a forest edge (FE) as a transition from the forest to the clear-cut under the canopy, a clear-cut edge (CE) as a transition from the forest to the clear-cut outside of the canopy, and the clear-cut proper (C). The composition and structure of ground vegetation and natural regeneration of woody species (Pinus sylvestris L., Picea abies (L.) H. Karst., Betula sp., Populus tremula L., Sorbus aucuparia L., and Juniperus communis L.) were studied in a bilberry pine forest-clear-cut ecotone complex 12-15 years after stand removal. Specific structural features of ground vegetation and undergrowth (including tree regeneration) were observed in each of the four zones of the ecotone complex formed after logging of the mature forest. Atypical forest habitat (zone F) showed a minimum number of young regeneration of Pinus sylvestris, Picea abies, Betula sp., Populus tremula, and Sorbus aucuparia and the highest abundance of the lingonberry V. vitis-idaea L. and bilberry Vaccinium myrtillus L. with a maximum height and a maximum yield of bilberry plants. The amount of tree regeneration in the FE zone was much the same as in the F zone. The projective cover, maximum shoot height, and yield of bilberry and the maximum shoot height of lingonberry in the FE zone were significantly lower than in the F zone. The transitional zone on the clear-cut side (CE) and the clear-cut proper (C) strikingly differed from the forest (F and FE) zones of the ecotone complex by a greater number of deciduous and pine regeneration and a low abundance of dwarf shrubs. The clear-cut proper (C) differed from the CE zone by a higher abundance of grasses and forbs and an established tree regeneration layer composed of pine, birch, and aspen.

Spatial variability in the contribution of termites to the decay of plant detritus

AbstractDrylands are characterized by high spatial variability in resource availability due to sporadic rainfall, topography of the landscape and important effects of animals. Resource availability gradients may trigger patterns in decomposer population abundances and activity, which could affect ecosystem functions such as decomposition. Here, we examined the influence of resource availability gradients on the importance of termites in the decomposition of wood and grass litter. We placed wood blocks and grass litter baits in bags accessible and inaccessible to termites across wood and grass resource gradients as determined by the presence or absence of a top mammalian predator and across topographic gradients during a 9‐month period in arid Australia. We hypothesized that grass‐eating termite activity would track grass abundance and wood‐eating termite activity would track wood abundance. Termites were the predominant decomposition agent at these sites. Termites contributed to 99.5% of wood decomposition and 83.9% of grass decomposition during our study period. For wood, the termite effect was spatially variable and increased with habitat wood availability, which was greatest on dunes and where top predators were absent. However, the contribution of termites to grass litter decomposition did not track grass availability or termite abundance. The highest effects of termites on grass decomposition rates were found in habitats where the absence of top predators led to low grass availability. Our findings highlight how spatial variability in resources in addition to other factors that we do not document but are known to be influenced by the presence of top predators, such as insectivore predation rates, across the landscape could affect ecosystem functions such as decomposition.

Cross-scale analysis reveals interacting predictors of annual and perennial cover in Northern Great Basin rangelands.

Exotic annual grass invasion is a widespread threat to the integrity of sagebrush ecosystems in Western North America. Although many predictors of annual grass prevalence and native perennial vegetation have been identified, there remains substantial uncertainty about how regional-scale and local-scale predictors interact to determine vegetation heterogeneity, and how associations between vegetation and cattle grazing vary with environmental context. Here, we conducted a regionally extensive, one-season field survey across burned and unburned, grazed, public lands in Oregon and Idaho, with plots stratified by aspect and distance to water within pastures to capture variation in environmental context and grazing intensity. We analyzed regional-scale and local-scale patterns of annual grass, perennial grass, and shrub cover, and examined to what extent plot-level variation was contingent on pasture-level predictions of site favorability. Annual grasses were widespread at burned and unburned sites alike, contrary to assumptions of annual grasses depending on fire, and more common at lower elevations and higher temperatures regionally, as well as on warmer slopes locally. Pasture-level grazing pressure interacted with temperature such that annual grass cover was associated positively with grazing pressure at higher temperatures but associated negatively with grazing pressure at lower temperatures. This suggests that pasture-level temperature and grazing relationships with annual grass abundance are complex and context dependent, although the causality of this relationship deserves further examination. At the plot-level within pastures, annual grass cover did not vary with grazing metrics, but perennial cover did; perennial grasses, for example, had lower cover closer to water sources, but higher cover at higher dung counts within a pasture, suggesting contrasting interpretations of these two grazing proxies. Importantly for predictions of ecosystem response to temperature change, we found that pasture-level and plot-level favorability interacted: perennial grasses had a higher plot-level cover on cooler slopes, and this difference across topography was starkest in pastures that were less favorable for perennial grasses regionally. Understanding the mechanisms behind cross-scale interactions and contingent responses of vegetation to grazing in these increasingly invaded ecosystems will be critical to land management in a changing world.

A new MIS 5 to MIS 2 speleothem record from Sandkraal Cave on the South African Cape south coast

AbstractWe present new stable oxygen and carbon isotope composite records (δ18O, δ13C) of speleothems from Sandkraal Cave 1 (SK1) on the South African south coast for the time interval between 104 and 18 ka (with a hiatus between 48 and 41 ka). Statistical comparisons using kernel-based correlation analyses and semblance analyses based on continuous wavelet transforms inform the relationships of the new speleothem records to other proxies and their changes through time. Between 105 and ~70 ka, changes of speleothem δ18O values at SK1 are likely related to rainfall seasonality. Variations of δ13C values are associated with changes of vegetation density, prior carbonate precipitation (PCP), CO2 degassing in the cave, and possibly variations of the abundance of C3 and C4 grasses in the vegetation. The relationships of δ18O with other proxies shift between ~70 and 48 ka (Marine Isotope Stages 4–3) so that both stable isotope records now reflect CO2 degassing, evaporation, and PCP. Similar relationships also continue after the hiatus for the deposition phase between 42 and 18 ka. Our findings support modeling results suggesting drier conditions in the study area when the Southern Hemisphere westerlies are shifted north and the paleo–Agulhas Plain is exposed.

Extreme precipitation promotes invasion in managed grasslands.

Climate change is increasing the frequency and intensity of extreme events like drought and flooding, which threaten to amplify other global change drivers such as species invasion. We investigate the effect of wet and dry extreme precipitation regimes on invasive species' abundances in northern tallgrass prairies. Because soil moisture is a key determinant of prairie composition, theory and evidence suggest drought conditions will hinder invasion, whereas wetter conditions will enhance invasion. To test this hypothesis, we explored the effect of precipitation on invasive plant species abundance from 2010 to 2019 in 25 managed prairies using observations from 267 transects comprising 6675 plots throughout western Minnesota, USA. We estimated how increases in the number of extremely wet or dry months in a year altered overall invasive species abundance and the abundance of the highly invasive grasses Poa pratensis and Bromus inermis. We found that a greater occurrence of abnormally wet months increased invasive species abundance but found mixed evidence that abnormally dry conditions hindered invasion. Further, more moderately wet and dry months reduced native grass abundance. Together, these results suggest that more frequent extremely wet months may intensify invasive dominance and that dry months may not counterbalance these trends. Given the considerable uncertainty still surrounding the interactive effects of climate change and invasion on native plant communities, this research represents an important step toward quantifying the complex influence of precipitation extremes on invasion dynamics in managed ecosystems of critical conservation concern.

Habitat selection by Grevy's zebra (Equus grevyi): Conservation implications

AbstractUnderstanding the spatial dynamics of landscape use by free‐ranging herbivores is essential for species management and conservation in its natural environment. We used Ivelv’s selection index, binary logistic regression analyses and stepwise regression to understand how environmental factors shape habitat selection by the Grevy’s zebra (Equus greyvi). We measured biotic, abiotic and human factors that may influence presence or absence of Grevy’s zebra in Samburu‐Laikipia landscape and showed: (1) during wet periods, percentage perennial grasses, livestock density and grass quality had the greatest effect on Grevy’s zebra presence; but (2) during dry weather periods a different suite of factors determined their landscape distribution, namely, the percentage of tree and bush density, distance to water and overall grass abundance. In addition, different Grevy’s zebra demographic and reproductive classes varied in their response to environmental selective forces, thus demonstrating flexibility in their patterns of habitat selection. While we recommend more detailed studies on how abiotic and biotic interact to shape habitat selection patterns, our findings underscored the need of maintaining both dry and wet season habitats to ensure essential grazing area refugia. Our findings show that ‘soft’ development with controlled livestock stocking rates within the landscape will enhance Grevy’s zebra conservation.

Diet flexibility in three harvester ants (Pogonomyrmex spp.): effects of grazing and natural variations in the availability of seeds

The study of diet and its relationship with available resources allows us to evaluate how species that differ in their degree of ecological flexibility respond to natural and anthropogenic variations that affect food availability. In the central Monte desert, extensive cattle ranching reduces the abundance of grass seeds, the most consumed and preferred food by the harvester ants Pogonomyrmex inermis Forel, 1914, Pogonomyrmex mendozanus (Cuezzo & Claver, 2009), and Pogonomyrmex propinqua (Johnson, 2021). We studied the diet of these species in grazed and ungrazed habitats over 4 years, including a period during which the abundance of grass seeds naturally decreased. We expected that ants would modify their diet in grazed sites and that the response would be different among species depending on their ecological flexibility. The three species presented a mainly granivorous diet in both grazing conditions and during the 4 years, but showed differences in the breadth of their diet. Pogonomyrmex inermis and Pogonomyrmex propinqua always had a narrow diet that consisted mainly of grass seeds, while Pogonomyrmex mendozanus modified its diet to include higher proportions of shrub seeds and other items when the abundance of grass seed decreased. In a scenario of scarce resources, this flexibility could represent an advantage over a more strict graminivorous diet.

Paleobiology of Pleistocene large land mammals from the Brazilian Pampa

The southern Brazilian Pleistocene fauna exhibited a rich diversity of large mammalian herbivores, which are now extinct or locally extinct. In this study, we employed stable isotope analysis to investigate the past ecology of these animals. Specifically, we examined the carbonate fraction of bones and teeth and utilized compiled carbon and oxygen isotopic ratios from previous research publications. The δ13C values indicated that most specimens inhabited grassland environments, which aligns with environmental reconstructions based on pollen records of the “Campos” region. The dominant food resource for these herbivores consisted of C3 photosynthesizers, mainly cool-season grasses. This preference can be attributed to the higher abundance and nutritional quality of cool-season grasses compared with warm-season grasses employing C4 photosynthesis. The variability in δ18O values within and between taxa may suggest a seasonal climate. Based on these findings, we conclude that the environmental changes during the Pleistocene-Holocene transition were detrimental to the survival of these large herbivores.

Microhabitat Conditions Influencing Ground Vegetation Dominants in an Ecotone between a Spruce (Picea abies (L.) H.Karst.) Forest and Clear-Cut Site during Ten Post-Logging Years

The logging of mature tree stands, where part of the forest is clear-cut, results in the formation of an ecotone complex (EC) consisting of the forest (F), a transition from forest to a clear-cut site under canopy cover (forest edge—FE), a transition from forest to a clear-cut site outside of canopy cover (clear-cutting edge—CE), and the clear-cut site per se (C). Ground vegetation descriptions (percentage cover of dominants and height of subshrubs) were carried out on the sampling subplots along the transects running from spruce forest into the clear-cut site. We studied the effects of the time since logging and some microhabitat factors (aspect, coniferous and deciduous regeneration, downed deadwood, microrelief, and the abundance of subshrubs, grasses, and forbs) on the abundance of the main ground vegetation dominants of the bilberry-type spruce stands and the clear-cut sites: Vaccinium myrtillus, V. vitis-idaea, Deschampsia flexuosa, and Epilobium angustifolium, in different EC zones. The factor found to have the greatest modifying effect on the abundance of all the species in the CE and C zones was the time since clear-cutting. The clear-cutting pioneer species Deschampsia flexuosa and Epilobium angustifolium preferred open areas in the clear-cut site, whereas the abundance of V. myrtillus and V. vitis-idaea positively correlated with the amount of coniferous and deciduous regeneration. Some factors (downed deadwood, microrelief, coniferous regeneration) were found to act similarly on subshrubs both under the tree canopy (F and FE) and in clear-cut microhabitats (CE and C). The shoot height of subshrubs as well as its percentage cover varied depending on the time since clear-cutting and the microhabitat conditions.

Testing the hierarchy of predictability in grassland restoration across a gradient of environmental severity.

Ecological restoration is critical for recovering degraded ecosystems but is challenged by variable success and low predictability. Understanding which outcomes are more predictable and less variable following restoration can improve restoration effectiveness. Recent theory asserts that the predictability of outcomes would follow an order from most to least predictable from coarse to fine community properties (physical structure > taxonomic diversity > functional composition > taxonomic composition) and that predictability would increase with more severe environmental conditions constraining species establishment. We tested this "hierarchy of predictability" hypothesis by synthesizing outcomes along an aridity gradient with 11 grassland restoration projects across the United States. We used 1829 vegetation monitoring plots from 227 restoration treatments, spread across 52 sites. We fit generalized linear mixed-effects models to predict six indicators of restoration outcomes as a function of restoration characteristics (i.e., seed mixes, disturbance, management actions, time since restoration) and used variance explained by models and model residuals as proxies for restoration predictability. We did not find consistent support for our hypotheses. Physical structure was among the most predictable outcomes when the response variable was relative abundance of grasses, but unpredictable for total canopy cover. Similarly, one dimension of taxonomic composition related to species identities was unpredictable, but another dimension of taxonomic composition indicating whether exotic or native species dominated the community was highly predictable. Taxonomic diversity (i.e., species richness) and functional composition (i.e., mean trait values) were intermittently predictable. Predictability also did not increase consistently with aridity. The dimension of taxonomic composition related to the identity of species in restored communities was more predictable (i.e., smaller residuals) in more arid sites, but functional composition was less predictable (i.e., larger residuals), and other outcomes showed no significant trend. Restoration outcomes were most predictable when they related to variation in dominant species, while those responding to rare species were harder to predict, indicating a potential role of scale in restoration predictability. Overall, our results highlight additional factors that might influence restoration predictability and add support to the importance of continuous monitoring and active management beyond one-time seed addition for successful grassland restoration in the United States.

Long-Term Effects of Revegetation Efforts in Annual Grass−Invaded Rangeland

Invasive annual grasses, such as medusahead (Taeniatherum caput-medusae [L.] Nevski), have invaded tens of millions of hectares of the sagebrush ecosystem. These invasions severely reduce ecosystem goods and services provided, as well as increase the probability of frequent, large wildfires. Revegetation of invasive annual grass−invaded rangeland with perennial bunchgrasses is critical to reversing these negative consequences. Short-term evaluations of revegetation efforts have shown promising results. However, long-term evaluations of revegetation efforts in medusahead-invaded rangelands are lacking, so it remains unknown if revegetation attempts in these invaded rangelands have persistent effects. We evaluated the effects of controlling medusahead with prescribed burning and imazapic application followed 1 yr later with drill-seeding large perennial bunchgrasses at two seeding rates (medium and high) for more than a decade post seeding. Large perennial bunchgrass cover and density was > 16- and > 4-fold greater in revegetation treatments compared with the untreated control 11 yr after seeding, respectively. Invasive annual grass abundance was ∼twofold greater in the untreated control compared with the revegetation treatments. These results suggest that revegetation efforts in medusahead-invaded rangelands can have persistent ecological benefits (increased perennials and decreased invasive annuals). The high seeding rate resulted in more perennial bunchgrass and less invasive annual grass compared with the medium seeding rate over the duration of the study, suggesting that high seeding rates may be needed to maximize benefits. Revegetation of medusahead-invaded rangelands can have long-lasting effects, though high establishment of perennial bunchgrasses is likely necessary for success.

Oryctolagus Cuniculus Algorithm and Its Application in the Inversion Method of Asteroid Spectra Reflectance Template

To improve the global optimization ability and convergence speed of the swarm intelligence algorithm, we proposed a new swarm intelligence optimization algorithm, namely the Oryctolagus cuniculus algorithm. This includes five mechanisms: the determination of safety zones, the cave escape, the agglomeration of Oryctolagus cuniculi, the maintenance of the Oryctolagus cuniculus king, and the zone competition. Each solution is represented by each Oryctolagus cuniculus’s position (including zone number and specific location number). The grass density and safety index at the location of the Oryctolagus cuniculus represents its fitness value. The determination of safety zones implies that predators such as eagles hunt Oryctolagus cuniculi in dangerous zones, and the zone without predators is considered a safety zone. The cave escape refers to the act of Oryctolagus cuniculi using a connected cave system to flee from a dangerous zone and reach a secure zone, thereby evading potential predators. We select the Oryctolagus cuniculus with higher fitness values as the king of each zone, and the Oryctolagus cuniculi gather towards the Oryctolagus cuniculus king. This mechanism ensures that Oryctolagus cuniculus mainly searches in zones with abundant grass and quickly finds the optimal solution. In the maintenance of the Oryctolagus cuniculus king, we choose the one with higher fitness values as the Oryctolagus cuniculus king. Zone competition is induced by an increase in the number of Oryctolagus cuniculi in zones with abundant grass by ordering the fitness values of each zone, and vice versa. We apply the Oryctolagus cuniculus algorithm to the inversion method of the asteroid spectra reflectance template. The experimental results show that compared with artificial rabbit optimization, this algorithm has a faster rate of convergence and better solution, effectively screens the reflectance template, and improves the Doppler difference velocimetry accuracy. In addition, the application of the Oryctolagus cuniculus algorithm to the knapsack problem also performs effectively.

Elevation, canopy cover and grass cover structure patterns of seedling establishment in a subtropical post‐fire restoration

Abstract Ecological restoration is beneficial to ecological communities in this era of large‐scale landscape change and ecological disruption. However, restoration outcomes are notoriously variable, which makes fine‐scale decision‐making challenging. This is true for restoration efforts that follow large fires, which are increasingly common as the climate changes. Post‐fire restoration efforts, like tree planting and seeding have shown mixed success, though the causes of the variation in restoration outcomes remain unclear. Abiotic factors such as elevation and fire severity, as well as biotic factors, such as residual canopy cover and abundance of competitive understorey grasses, can vary across a burned area and may all influence the success of restoration efforts to re‐establish trees following forest fires. We examined the effect of these factors on the early seedling establishment of a tree species—māmane (Sophora chrysophylla)—in a subtropical montane woodland in Hawaiʻi. Following a human‐caused wildfire, we sowed seeds of māmane as part of a restoration effort. We co‐designed a project to examine māmane seedling establishment. We found that elevation was of overriding importance, structuring total levels of plant establishment, with fewer seedlings establishing at higher elevations. Residual canopy cover was positively correlated with seedling establishment, while cover by invasive, competitive understorey grasses very weakly positively correlated with increased seedling establishment. Our results point to specific factors structuring plant establishment following a large fire and suggest additional targeted restoration actions within this subtropical system. For example, if greater native woody recruitment is a management goal, then actions could include targeted seed placement at lower elevations where establishment is more likely, increased seeding densities at high elevation where recruitment rates are lower, and/or invasive grass removal prior to seeding. Such actions may result in faster native ecosystem recovery, which is a goal of local land managers.

Response of herbaceous functional types and woody vegetation to selective shrub control on wildlife and cattle ranches in a semi‐arid savanna

AbstractAimsShrub encroachment is a major challenge for livestock and wildlife management in semi‐arid savannas. Shrub removal by land managers is widespread, but the long‐term effects on vegetation structure and composition, which determine carrying capacity for herbivores, are poorly documented. This study aims to examine the effects of selective shrub removal to guide vegetation management in key land uses of semi‐arid African savannas.QuestionsVegetation responses were assessed across land uses and treatments to answer the following questions: (1) does shrub removal increase the frequency of palatable plants and therefore herbivore‐carrying capacity; (2) does selective shrub removal decrease woody vegetation structure 15 years after application; and (3) how do these effects differ between cattle and wildlife ranching?LocationMolopo region of the North West Province, South Africa.MethodsHerbaceous and woody vegetations were sampled within six transects each of three wildlife ranches and three cattle ranches in areas that had either been selectively shrub‐controlled with herbicides 10–15 years previously or left untreated. To quantify effects of woody shrub control on herbaceous functional‐group abundances and assemblages, tree equivalents, regrowth rate, and shrub abundance, we compared these variables across two treatments (treated and untreated) and land uses. Data were analysed using GLMMs, NMDS ordinations, PERMANOVA, and SIMPER.ResultsSelective shrub control effectively improved palatable herbaceous vegetation, especially on cattle ranches. Especially abundance of perennial grass was higher on wildlife ranches compared to cattle ranches. Tree equivalent was higher in untreated compared to treated plots, and these differences were more pronounced on wildlife ranches than on cattle ranches.ConclusionssSelective shrub removal improved the palatable herbaceous layer for both wildlife and cattle ranching and can be considered an effective management strategy in semi‐arid rangelands.

Assessment of the diet of the critically endangered northern hairy-nosed wombat (Lasiorhinus krefftii) using DNA metabarcoding.

Invasive buffel grass (Cenchrus ciliaris) is considered a threat to the critically endangered northern hairy-nosed wombat (Lasiorhinus krefftii; NHW). Buffel grass outcompetes native grasses, reducing availability of native food items for NHW, and causes more intense fires due to the large volumes of dead matter it produces. Previous studies suggested buffel grass was increasing in the diet; however, the diet of the NHW has not been reassessed for over two decades and was limited to Epping Forest National Park, with the population at Richard Underwood Nature Refuge having never been assessed. The recently released 2022 Recovery Action Plan for the species outlined objectives to assist its conservation and recommended the impact of buffel grass on the species' diet be investigated. This study aimed to determine: (1) which plant species are being consumed by the NHW; (2) the differences in the diet between sites; (3) differences between seasons; and (4) the abundance of buffel grass in the diet. The diet was assessed using DNA metabarcoding of scat samples collected from both sites from winter 2020 to spring 2021. Site and season significantly affected the diet of the NHW. Buffel grass dominated the diet and has increased in the diet since past assessments. The findings of this study will support population and habitat management of the critically endangered NHW. Enhanced knowledge of dietary items consumed at both sites will also assist efforts to locate additional sites suitable for translocation.

Predicting Exotic Annual Grass Abundance in Rangelands of the Western United States Using Various Precipitation Scenarios

Expansion of exotic annual grass (EAG), such as cheatgrass (Bromus tectorum L.) and medusahead (Taeniatherum caput-medusae [L.] Nevski), could cause irreversible changes to arid and semiarid rangeland ecosystems in the western United States. The distribution and abundance of EAG species are highly affected by weather variables such as temperature and precipitation. The study's goal is to understand how different precipitation scenarios affect EAG abundance estimates and dynamics, and we develop a machine learning modeling approach to predict how changes in annual and immediate past precipitation patterns could affect the abundance of EAG. The machine learning predictive model used seed source from previous years, weather variables, and soil profiles to drive its predictions. We achieved excellent training accuracy (r = 0.95 and median absolute error [MdAE] = 2.36% cover) and strong test accuracy (r = 0.79 and MdAE = 4.54% cover). We developed five versions of EAG abundance maps for 2022 with different precipitation scenarios: 9 yr of average precipitation, half of the average, three-fourths of the average, one and one-half times the average, and two times the average. The approach presented can be replicated to new study domains and easily modified for use with other precipitation scenarios. Developing multiple versions of a year's EAG spatially explicit abundance dataset predictions from multiple weather-based scenarios can provide important information to land managers as they prepare for variable EAG dynamics each year. Informed annual predictions based on weather scenario−driven models have the potential to improve fire preparation decisions.

Belowground soil and vegetation components change across the aridity threshold in grasslands

Grassland ecosystem functions are affected by global climate change and increasing aridity. Belowground components of soil and vegetation, such as specific root length, belowground biomass and soil organic carbon are important for maintaining these functions. However, aridity affects these components in different ways. This research evaluates changes in soil properties and plant attributes with aridity along a 2600 km aridity gradient in the arid and semiarid grasslands of Inner Mongolia. The aridity index was used considering the ratio of precipitation to potential evapotranspiration, where a higher value indicates greater aridity. Results showed an overall aridity threshold for grassland ecosystems of 0.67, where abrupt changes in belowground components were observed. The effect of aridity on specific root length changed from negative (−0.18) below the threshold to positive (0.24) above the threshold, with the emergence of coordination between aboveground and belowground plant characteristics. Aridity exhibited a negative effect on belowground biomass, increasing from −0.24 below the threshold to −0.55 above the threshold as the positive effect of relative grass abundance disappeared. The total effect of aridity on soil organic carbon showed a subtle change, but the driving pathways through which aridity affects changed from soil loss to aridity itself and vegetation cover at plot scale. These findings highlight how aridity affects belowground components in grassland ecosystems above and below the aridity threshold. They provide a basis for better understanding aridity-driven interactions in grassland ecosystems, and can be used to inform actions to protect grasslands under future climate change.

Choose Local: Dung Addition from Native Herbivores Can Produce Substantial Positive Effects on the Growth of Native Grasses Compared to Livestock Dung

Livestock grazing and dung deposition can increase soil nutrients, contributing to the dominance of exotic species. Recent research suggests that native herbivore grazing has positive effects on native vegetation and soil health. However, little is known about the effects of native herbivore dung on plant growth and its potential implications for the restoration of degraded grasslands. This study examined the effects of dung addition from a native herbivore, kangaroo (Macropus giganteus), and ruminant livestock, sheep (Ovis aries), on biomass production and nutrient uptake of the native perennial wallaby grass (Rytidosperma auriculatum) and the annual exotic wild oat (Avena barbata), two of the most abundant grasses from the temperate grasslands of southern Australia. We conducted a glasshouse experiment, adding each type of dung to each plant species grown without competition in pots containing soil with a nutrient composition similar to that of old fields. Kangaroo dung produced higher wallaby grass aboveground biomass than other treatments and less wild oat aboveground biomass than the control. Kangaroo dung affected nutrient uptake but not nutrient concentration. Sheep dung had no effect. We demonstrated that native herbivores and livestock dung can have different effects on the biomass of native and invasive grasses. The higher nutrient uptake in wallaby grass appeared to be a consequence of the higher biomass production, suggesting that the effects produced by kangaroo dung could be related to its chemical and biological characteristics rather than its nutrient composition. Incorporating native herbivores’ dung or facilitating their presence can improve restoration outcomes in degraded grasslands.