Indian Ricegrass Research Articles

PSVI-27 Evaluation of Coated and Non-Coated Seed Species Pertinent to the Great Basin in Response to in Vitro Ruminal Incubation

Abstract Target grazing has exhibited itself as an effective method of invasive weed mitigation across degraded rangelands in the Great Basin. Additionally, if the seeds of target species are supplemented into the diets of ruminants, they can serve as vectors for the dispersal of native seed species through fecal pats, which may prove to be a useful tactic for rangeland rehabilitation. However, a challenge associated with seed supplementation, is that the seeds of many target species are sufficiently degraded in the rumen. Therefore, the aim of this study was to evaluate the effects of seed coating technologies on germination rates post ruminal in vitro incubation. In vitro incubations were performed on seven species of seeds pertinent to the Great Basin: Achnatherum hymenoides (ACHY), Achillea millefolium (ACMI), Agropyron cristatum (AGCR), Atriplex canascens (ATCA), Elymus elymoides (ELEL), Pseudoregneria spicata (PSSP), and Sphaeralcea grossulariifolia (SPRT) uncoated (control) or coated with either Polyvinylpyrrolidone (PVP) or PVP+ ethocel, as well as uncoated Bromus tectorum (BRTE) seeds. A Daisy II incubator (Ankom Technology, Macedon, NY) was used for the in vitro analysis with rumen inoculum from two rumen-cannulated crossbred Angus steers (body weight = 910.5 ± 34.5 kg) and a buffer ratio of 1:4. Two F57 filter bags containing 1 g of seeds per treatment (control, PVP or PVP+ethocel) were then placed inside of the Daisy II incubator and kept at 39°C for 12 and 24 h for the control treatments, and for 12, 24, and 48 h for the PVP and PVP+ethocel coating treatments. For uncoated seeds, ACHY germination by 24 h was greater when compared with 0 h (P < 0.05), whereas ATCA germination rate decreased linearly by 12 h (P < 0.05). No differences were observed over time on germination rates of BRTE, as well as all of the other uncoated seeds (P > 0.05). When seeds were coated with PVP, ATCA germination rates started to linearly decrease by 12 h (P < 0.05), whereas PVP coated ACMI germination rates only started to decrease by 24 h (P < 0.05). The germination rates of PVP coated ELEL and PSSP seeds only started to significantly decrease by 48 h (P < 0.05). When coated with PVP+ethocel, the observed germination rates were similar to those observed for PVP coated seeds. However, when compared with uncoated seeds, coating with PVP+ethocel seem to decrease germination rates of ACMI and ATCA by 0 h (P < 0.05). No changes on germination rates were observed over time for coated and uncoated AGCR and SPRT (P > 0.05). In conclusion, seed germination rates after in vitro incubation were not increased by coating the seeds with PVP or PVP+ethocel.

353 Evaluation of Native and Invasive Seed Germination Ability After in Situ Incubation in the Rumen for Rangeland Restoration Through Targeted Seed Supplementation

Abstract Changes to native plant compositions of drylands are often associated to loss of wildlife, increased frequency, and severity of wildfires; further, it complicates the grazing permits and allocation during periods of restoration. The goals herein investigate the germination rates of native seed species after in situ incubation to evaluate their potential dispersal as supplements for grazing cattle. Native: Indian ricegrass (Achnatherum hymenoides; ACHY), white yarrow (Achillea millefolium; ACMI), crested wheatgrass (Agropyron cristatum; AGCR), sagebrush (Artemisia tridentata; ARTR), fourwing saltbrush (Atriplex canascens; ATCA), bottlebrush squirreltail (Elymus elimoides; ELEL), bluebunch wheatgrass (Pseudoregneria spicata; PSSP), and gooseberryleaf globemallow (Sphaeralcea grossulariifolia; SPRT) and nonnative: cheatgrass (Bromus tecorum, BRTE; fall BRTEf and spring seeds BRTEs) seeds were examined. Four ruminally canulated Angus x Hereford steers adapted to a forage kochia-alfalfa diet were utilized for seed incubations. Seeds were weighed into 84 bags at a rate of 5 g per bag (duplicated within and in different animals). Seeds were incubated sequentially (0, 6, 12, 24, 36, 48, and 96 h) and removed at the 96-h point when seeds were thoroughly washed and immediately counted (50) on square 80 mm 80 mm commercial sterile petri dishes with moisture pads and 5 mL of water. Seeds were incubated at 20 °C with 12 h of light/no-light intervals. Germination plates were incubated for 50 d and counted every 10 d for germinations. Generalized linear models assuming a Poisson distribution with separation of means through Dunnett’s multiple comparisons test. Statistical significance was declared at P < 0.05. All statistical analyses were performed on R (R Core Team 2022). Incubation times inside of the rumen linearly decreased germination rates across most seed species. For BRTEs, germination completely stopped at 48 h with a steep decrease observed after 24 h incubation. The BRTEf were also incubated but showed low germination both before and after rumen exposure (winter dormancy). Though ARTR is very important in rangeland restoration in the intermountain west, its germination declined more than 85% within just a 6 h incubation in situ (P < 0.001). A significant germination decrease was observed for AGCR at 36 h; however, germination was full at 48 h and 50% of the original at 96 h (P < 0.05). For ACMI, germination rates significantly declined after 36 h incubation, and for PSSP after 24 h. Low germinations were observed for ACHY, SPRT, and ATCA even with high reported in-bag tetrazolium chloride viabilities. Our results highlight that cattle grazing of cheatgrass does not spread seeds through fecal pats. Additional tests are required to determine seed viability of the dormant (low germination) BRTEf. Seed toleration to ruminal degradation highlights the potential targeted seed supplementation during grazing for rangeland restoration.

Leveraging Historic Cattle Exclosures to Detect Evidence of State Change in an Arid Rangeland

Grazing, a defining use of rangelands, can have immediate and legacy impacts in ecosystems with short evolutionary histories of grazing and where climatic conditions are marginal and variable. In arid rangelands of the Colorado Plateau, domesticated ungulates were introduced in the 1800s at high densities and grazing has been maintained in the region at variable stocking rates for approximately the past 150 yr. Historic grazing practices, combined with a marginal climate, may have caused an irreversible shift in the vegetation community leading to limited recovery with cessation of grazing. Using three exclosures ranging from 12 to 50 yr of age, we evaluated vegetation composition, diversity, and cover inside the exclosures and compared them with directly adjacent, actively grazed areas outside of the exclosures in the fall and spring of 2018 and 2019. We then asked 1) How do exclosures and their adjacent unexclosed sites differ in vegetation diversity, composition, and cover? and 2) Are there significant differences in cover of key forage species in exclosed versus unexclosed areas? Overall, there were significant differences in vegetation communities inside and outside of exclosures in both seasons. Composition, alpha, and beta diversity differed between grazed and exclosed sites, with higher alpha and beta diversity in the 50-yr exclosure in the fall. Composition was significantly different between exclosures and unexclosed sites at all sites and in all seasons. Cover of several important forage grasses (Achnatherum hymenoides, Hilaria jamesii, Elymus elymoides) was higher in exclosed areas, while cover of Scleropogon brevifolius and Bouteloua gracilis was higher in unexclosed areas. Taken together, these results indicate limited recovery of vegetation in the absence of grazing, with exclosures exhibiting higher plant diversity, as well as cover of some desirable forage species, suggesting this area has not undergone irreversible state change but recovery may require > 50 yr of grazing cessation.

Drought resistance and resilience: The role of soil moisture–plant interactions and legacies in a dryland ecosystem

Abstract In many regions of the world, climate change is projected to reduce water availability through changes in the hydrological cycle, including more frequent and intense droughts, as well as seasonal shifts in precipitation. In water‐limited ecosystems, such as drylands, lower soil water availability may exceed the adaptive capacity of many organisms, leading to cascading ecological effects during (concurrent effects) and after drought (legacy effects). The magnitude and duration of concurrent and legacy effects depends on drought intensity, duration and timing as well as the resistance and resilience of the ecosystem. Here, we investigated the effects of drought seasonality and plant community composition on two dominant perennial grasses, Achnatherum hymenoides (C3 photosynthesis) and Pleuraphis jamesii (C4 photosynthesis), in a dryland ecosystem. The experiment consisted of three precipitation treatments: control (ambient precipitation), cool‐season drought (−66% ambient precipitation November–April) and warm‐season drought (−66% ambient precipitation May–October), applied in two plant communities (perennial grasses with or without a large shrub, Ephedra viridis) over a 3‐year period. We examined the concurrent and legacy effects of seasonal drought on soil moisture, phenology and biomass. Drought treatments had strong concurrent and legacy effects on soil moisture, which impacted the phenology and biomass of the two grasses. Drought reduced growing season length by delaying green‐up (cool‐season drought) or advancing senescence (warm‐season drought) and reduced biomass for both species. Biomass and phenology legacy effects from drought emerged in the second and third years of the experiment. While we observed differential sensitivity to drought legacies between the two grasses, we found limited evidence that shrub presence had interactive effects with the drought treatment. Synthesis. The results from this study highlight how abiotic and biotic legacies can develop and influence a community's resistance and resilience to subsequent droughts. When the frequency of repeated extreme events, such as recurring seasonal droughts, exceeds the capacity of organisms or ecosystems to recover (i.e. resilience), persistent drought legacies can reduce the resistance to subsequent drought events. Overall, these results highlight how drought legacies are a product of ecological resistance and resilience to past drought and can influence ecosystem vulnerability to future droughts.

Harvester ant seed removal in an invaded sagebrush ecosystem: Implications for restoration.

A better understanding of seed movement in plant community dynamics is needed, especially in light of disturbance‐driven changes and investments into restoring degraded plant communities. A primary agent of change within the sagebrush‐steppe is wildfire and invasion by non‐native forbs and grasses, primarily cheatgrass (Bromus tectorum). Our objectives were to quantify seed removal and evaluate ecological factors influencing seed removal within degraded sagebrush‐steppe by granivorous Owyhee harvester ants (Pogonomyrmex salinus Olsen). In 2014, we sampled 76 harvester ant nests across 11 plots spanning a gradient of cheatgrass invasion (40%–91% cover) in southwestern Idaho, United States. We presented seeds from four plant species commonly used in postfire restoration at 1.5 and 3.0 m from each nest to quantify seed removal. We evaluated seed selection for presented species, monthly removal, and whether biotic and abiotic factors (e.g., distance to nearest nest, temperature) influenced seed removal. Our top model indicated seed removal was positively correlated with nest height, an indicator of colony size. Distance to seeds and cheatgrass canopy cover reduced seed removal, likely due to increased search and handling time. Harvester ants were selective, removing Indian ricegrass (Achnatherum hymenoides) more than any other species presented. We suspect this was due to ease of seed handling and low weight variability. Nest density influenced monthly seed removal, as we estimated monthly removal of 1,890 seeds for 0.25 ha plots with 1 nest and 29,850 seeds for plots with 15 nests. Applying monthly seed removal to historical restoration treatments across the western United States showed harvester ants can greatly reduce seed availability at degraded sagebrush sites; for instance, fourwing saltbush (Atriplex canescens) seeds could be removed in <2 months. Collectively, these results shed light on seed removal by harvester ants and emphasize their potential influence on postfire restoration within invaded sagebrush communities.

Caching Propensities and Effectiveness of Five Coexisting Heteromyid Rodent Species as Dispersers of Indian Ricegrass (Achnatherum hymenoides) Seeds

Recruitment of Indian ricegrass (Achnatherum hymenoides) seedlings occurs primarily from surface seed caches made by scatter-hoarding desert rodents of the family Heteromyidae. We used radiolabeled Indian ricegrass seeds in field seed-caching experiments with 5 coexisting heteromyid species (Dipodomys deserti, D. merriami, D. microps, Microdipodops pallidus, and Perognathus longimembris) to compare their potential effectiveness as dispersers. Dipodomys microps individuals deposited seeds almost exclusively in larders rather than in scatter hoards, implying that this species is unlikely to be an important seed disperser. Among the other species, individual caches made by larger species had more seeds than those made by smaller species, but smaller species made more caches. At the level of individual animals, M. pallidus was the most effective disperser in a quantitative sense; they made more caches than other species tested and placed fewer excess seeds in caches relative to optimal cache sizes for Indian ricegrass seedling establishment. However, because D. merriami individuals were considerably more abundant at the study site than other species and were also avid scatter hoarders, D. merriami is likely to be the most quantitatively effective disperser of Indian ricegrass seeds at the species level. Ranking species according to qualitative effectiveness (e.g., by considering effects such as the caching microsite on seedling establishment) was more ambiguous. For example, P. longimembris made relatively shallow caches that most closely match optimal planting depths for Indian ricegrass seedling emergence, but such shallow caches are probably more likely than deeper caches to be discovered by foraging rodents before they can germinate. With the possible exception of D. microps, any of the species we tested may be effective dispersers of Indian ricegrass seeds.

From rediscovered “niche” to “mainstream” – Glyceria fluitans as a candidate grain for manufacturing premium food products

From rediscovered “niche” to “mainstream” – <i>Glyceria fluitans</i> as a candidate grain for manufacturing premium food products

Earlier plant growth helps compensate for reduced carbon fixation after 13 years of warming

Abstract Drylands play a dominant role in global carbon cycling and are particularly vulnerable to increasing temperatures, but our understanding of how dryland ecosystems will respond to climatic change remains notably poor. Considering that the area of drylands is projected to increase by 11%–23% by 2,100, understanding the impacts of warming on the functions and services furnished by these arid and semi‐arid ecosystems has numerous implications. In a unique 13‐year ecosystem warming experiment in a south‐western U.S. dryland, we investigated the consequences of rising temperature on Achnatherum hymenoides, a widespread, keystone grass species on the Colorado Plateau. We tracked individual‐ and population‐level responses to identify optimal strategies that may have been masked if considering only one level of plant response. We found several factors combined to affect the timing and magnitude of plant responses during the 13th year of warming. These included large warming‐induced biomass increases for individual plants, an 8.5‐day advancement in the growing season and strong reductions in photosynthetic rates and population cover. Importantly, we observed a lack of photosynthetic acclimation and, thus, a warming‐induced downregulation of photosynthetic rates. However, these physiological responses were concurrent with warmed‐plant increases in growing season length and investment in photosynthetic surfaces, demonstrating the species’ ability to balance carbon fixation limitations with warming. These results, which bring together ecophysiological, phenological, reproductive and morphological assessments of plant responses to warming, suggest that the extent of change in A. hymenoides populations will be based upon numerous adaptive responses that vary in their direction and magnitude. Plant population responses to climatic warming remain poorly resolved, particularly for Earth's drylands, and our in situ experiment assessing multiple strategies offers a novel look into a warmer world. A free Plain Language Summary can be found within the Supporting Information of this article.

Shrub persistence and increased grass mortality in response to drought in dryland systems.

Droughts in the southwest United States have led to major forest and grassland die-off events in recent decades, suggesting plant community and ecosystem shifts are imminent as native perennial grass populations are replaced by shrub- and invasive plant-dominated systems. These patterns are similar to those observed in arid and semiarid systems around the globe, but our ability to predict which species will experience increased drought-induced mortality in response to climate change remains limited. We investigated meteorological drought-induced mortality of nine dominant plant species in the Colorado Plateau Desert by experimentally imposing a year-round 35% precipitation reduction for eight continuous years. We distributed experimental plots across numerous plant, soil, and parent material types, resulting in 40 distinct sites across a 4,500km2 region of the Colorado Plateau Desert. For all 8 years, we tracked c. 400 individual plants and evaluated mortality responses to treatments within and across species, and through time. We also examined the influence of abiotic and biotic site factors in driving mortality responses. Overall, high mortality trends were driven by dominant grass species, including Achnatherum hymenoides, Pleuraphis jamesii, and Sporobolus cryptandrus. Responses varied widely from year to year and dominant shrub species were generally resistant to meteorological drought, likely due to their ability to access deeper soil water. Importantly, mortality increased in the presence of invasive species regardless of treatment, and native plant die-off occurred even under ambient conditions, suggesting that recent climate changes are already negatively impacting dominant species in these systems. Results from this long-term drought experiment suggest major shifts in community composition and, as a result, ecosystem function. Patterns also show that, across multiple soil and plant community types, native perennial grass species may be replaced by shrubs and invasive annuals in the Colorado Plateau Desert.

Interaction between Seed Detectability and Seed Preference Affects Harvest Rates of Granivorous Rodents

Granivorous rodents commonly exhibit preferences for seeds of particular plant species. However, among buried seeds that are available, rodents may find that alternate, less desirable seeds are more easily located by olfaction than preferred seeds. Seeds of Indian ricegrass (Achnatherum hymenoides) are a highly preferred food resource for seed-caching desert heteromyid rodents. We tested relative abilities of heteromyids to locate buried caches of Indian ricegrass seeds versus seeds of another plant species (cheatgrass, Bromus tectorum) that are common in heteromyid diets at a western Nevada field site. Rodents located more cheatgrass than Indian ricegrass seed caches in the field when seeds were unaltered. When ground, however, detectability of preferred Indian ricegrass seeds increased, presumably due to release of volatile compounds inside seeds, and more ground Indian ricegrass seed caches were found and removed compared with ground cheatgrass caches. Grinding cheatgrass seeds did not affect harvest rates of cheatgrass caches. Results of a laboratory cache removal experiment using 2 heteromyid species, Merriam's kangaroo rats (Dipodomys merriami) and long-tailed pocket mice (Chaetodipus formosus), mirrored field cache removal results. Dispersal of Indian ricegrass seeds and establishment of new seedlings occurs largely through emergence of seedlings from heteromyid scatterhoard caches. Our results suggest that Indian ricegrass seeds may have been selected for reduced olfactory detectability to minimize the probability that they are recovered by rodents for later consumption once they have been cached.

Fungal loop transfer of nitrogen depends on biocrust constituents and nitrogen form

Abstract. Besides performing multiple ecosystem services individually and collectively, biocrust constituents may also create biological networks connecting spatially and temporally distinct processes. In the fungal loop hypothesis rainfall variability allows fungi to act as conduits and reservoirs, translocating resources between soils and host plants. To evaluate the extent to which biocrust species composition and nitrogen (N) form influence loops, we created a minor, localized rainfall event containing 15NH4+ and 15NO3-. We then measured the resulting δ15N in the surrounding dry cyanobacteria- and lichen-dominated crusts and grass, Achnatherum hymenoides, after 24 h. We also estimated the biomass of fungal constituents using quantitative PCR and characterized fungal communities by sequencing the 18S rRNA gene. We found evidence for the initiation of fungal loops in cyanobacteria-dominated crusts where 15N, from 15NH4+, moved 40 mm h−1 in biocrust soils with the δ15N of crusts decreasing as the radial distance from the water addition increased (linear mixed effects model (LMEM)): R2=0.67, F2,12=11, P=0.002). In cyanobacteria crusts, δ15N, from 15NH4+, was diluted as Ascomycota biomass increased (LMEM: R2=0.63, F2,8=6.8, P=0.02), Ascomycota accounted for 82 % (±2.8) of all fungal sequences, and one order, Pleosporales, comprised 66 % (±6.9) of Ascomycota. The seeming lack of loops in moss-dominated crusts may stem from the relatively large moss biomass effectively absorbing and holding N from our minor wet deposition event. The substantial movement of 15NH4+ may indicate a fungal preference for the reduced N form during amino acid transformation and translocation. We found a marginally significant enrichment of δ15N in A. hymenoides leaves but only in cyanobacteria biocrusts translocating 15N, offering evidence of links between biocrust constituents and higher plants. Our results suggest that minor rainfall events may initiate fungal loops potentially allowing constituents, like dark septate Pleosporales, to rapidly translocate N from NH4+ over NO3- through biocrust networks.

Spatially explicit patterns in a dryland's soil respiration and relationships with climate, whole plant photosynthesis and soil fertility

Arid and semiarid ecosystems play a significant role in regulating global carbon cycling, yet our understanding of the controls over the dominant pathways of dryland CO2 exchange remains poor. Substantial amounts of dryland soil are not covered by vascular plants and this patchiness in cover has important implications for spatial patterns and controls of carbon cycling. Spatial variation in soil respiration has been attributed to variation in soil moisture, temperature, nutrients and rhizodeposition, while seasonal patterns have been attributed to changes in moisture, temperature and photosynthetic inputs belowground. To characterize how controls over respiration vary spatially and temporally in a dryland ecosystem and to concurrently explore multiple potential controls, we estimated whole plant net photosynthesis (Anet) and soil respiration at four distances from the plant base, as well as corresponding fine root biomass and soil carbon and nitrogen pools, four times during a growing season. To determine if the controls vary between different plant functional types for Colorado Plateau species, measurements were made on the C4 shrub, Atriplex confertifolia, and C3 grass, Achnatherum hymenoides. Soil respiration declined throughout the growing season and diminished with distance from the plant base, though variations in both were much smaller than expected. The strongest relationship was between soil respiration and soil moisture. Soil respiration was correlated with whole plant Anet, although the relationship varied between species and distance from plant base. In the especially dry year of this study we did not observe any consistent correlations between soil respiration and soil carbon or nitrogen pools. Our findings suggest that abiotic factors, especially soil moisture, strongly regulate the response of soil respiration to biotic factors and soil carbon and nitrogen pools in dryland communities and, at least in dry years, may override expected spatial and seasonal patterns.

A spring rainfall pulse causes greater in situ photosynthetic upregulation for Bromus tectorum compared to co-occurring native herbaceous species

The invasive grass Bromus tectorum fuels fires, displaces native species, and reduces wildlife habitat on sagebrush steppe throughout the western United States. Recently, it has spread from the Great Basin Desert into higher elevations of the eastern Sierra Nevada, where it coexists with natives but has not yet altered fire regimes. We evaluated effects of a springtime water pulse (+10mm) in a drought year on photosynthesis for B. tectorum and co-occurring shallow-rooted native perennials Achnatherum hymenoides, Elymus elymoides, and Lupinus argenteus near the range limit of B. tectorum at ∼2175m in California. Watered B. tectorum had the largest increase in stomatal conductance (27%) of the four species. Watering increased CO2 assimilation for B. tectorum by 78% over controls, compared to 17% for A. hymenoides, 2% for E. elymoides, and 29% for L. argenteus. Electron transport rate within Photosystem II increased for watered B. tectorum and A. hymenoides, but not for E. elymoides and L. argenteus. Instantaneous electron transport rate and carbon assimilation were more responsive for B. tectorum than natives following a spring water pulse during drought. Rapid upregulation of carbon uptake in spring in response to soil re-wetting during drought could facilitate B. tectorum spread at high elevation.

Can seed caching enhance seedling survival of Indian ricegrass (Achnatherum hymenoides) through intraspecific facilitation?

Positive interactions among individual plants (facilitation) may often enhance seedling survival in stressful environments. Many granivorous small mammal species cache groups of seeds for future consumption in shallowly buried scatterhoards, and seeds of many plant species germinate and establish aggregated clusters of seedlings from such caches. Scatterhoards made by desert heteromyid rodents provide a major source of seedling recruitment for Indian ricegrass (Achnatherum hymenoides), a perennial bunchgrass species occurring widely across arid southwestern deserts of North America. However, effects of the resulting clumping of seedlings on subsequent survival have not been quantified under field conditions, which include extended periods of excessive summer heat and little precipitation. We monitored Indian ricegrass seedlings transplanted into field exclosures at two western Nevada study sites as either single seedlings or clumps of 25 or 35 seedlings and compared their survival. Survival was positively correlated with the number of seedlings growing together, and survival of whole clumps of 25 or 35 seedlings was significantly greater than that of seedlings growing singly. Moreover, individual seedlings within clumps of 35 seedlings had significantly higher survival than seedlings growing singly. No single seedlings survived through the hot and very dry summer following their planting, but a small proportion (1.8–2.8 %) of individual seedlings within clumps survived. Results of this field experiment suggest that facilitative benefits accruing to Indian ricegrass due to seed-caching desert rodents can extend past seedling establishment and into the long-term survival of the plant.

Experimental warming in a dryland community reduced plant photosynthesis and soil CO2 efflux although the relationship between the fluxes remained unchanged

Summary Drylands represent our planet's largest terrestrial biome and, due to their extensive area, maintain large stocks of carbon (C). Accordingly, understanding how dryland C cycling will respond to climate change is imperative for accurately forecasting global C cycling and future climate. However, it remains difficult to predict how increased temperature will affect dryland C cycling, as substantial uncertainties surround the potential responses of the two main C fluxes: plant photosynthesis and soil CO2 efflux. In addition to a need for an improved understanding of climate effects on individual dryland C fluxes, there is also notable uncertainty regarding how climate change may influence the relationship between these fluxes. To address this important knowledge gap, we measured a growing season's in situ photosynthesis, plant biomass accumulation and soil CO2 efflux of mature Achnatherum hymenoides (a common and ecologically important C3 bunchgrass growing throughout western North America) exposed to ambient or elevated temperature (+2 °C above ambient, warmed via infrared lamps) for 3 years. The 2 °C increase in temperature caused a significant reduction in photosynthesis, plant growth and soil CO2 efflux. Of important note, photosynthesis and soil respiration appeared tightly coupled and the relationship between these fluxes was not altered by the elevated temperature treatment, suggesting C fixation's strong control of both above‐ground and below‐ground dryland C cycling. Leaf water use efficiency was substantially increased in the elevated temperature treatment compared to the control treatment. Taken together, our results suggest notable declines in photosynthesis with relatively subtle warming, reveal strong coupling between above‐ and below‐ground C fluxes in this dryland and highlight temperature's strong effect on fundamental components of dryland C and water cycles.

Forage Kochia and Russian Wildrye Potential for Rehabilitating Gardner’s Saltbush Ecosystems Degraded by Halogeton

Gardner’s saltbush ecosystems are increasingly being invaded by halogeton (Halogeton glomeratus [M. Bieb.] C.A. Mey.), an annual halophyte that increases soil surface salinity and reduces plant biodiversity. Thus, a study was established in the Flaming Gorge National Recreation Area within the lower Green River Basin of Wyoming to evaluate the potential for rehabilitating halogeton-dominated Gardner’s saltbush ecosystems with forage kochia (Bassia prostrata [L.] A.J. Scott), Russian wildrye (Psathyrostachys juncea [Fisch.] Nevski), tall wheatgrass (Thinopyrum ponticum [Podp.] Z.-W. Liu & R.-C. Wang), Indian ricegrass (Achnatherum hymenoides [Roem. & Schult.] Barkworth), and Gardner’s saltbush (Atriplex garneri [Moq.] D. Dietr.). A seeding evaluation, with and without prior disking, was conducted to determine ability of these species to establish. A transplant evaluation determined the effect of established plants on halogeton frequency at four 10-cm intervals (10–20, 20–30, 30–40, and 40–50 cm) distal from transplants. Gardner’s saltbush, tall wheatgrass, and Indian ricegrass did not establish in the seeded study or persist beyond the first year in transplant study. In contrast, Russian wildrye and forage kochia established and persisted, with Russian wildrye establishment higher (P = 0.05) in the disked treatment compared with no-till (4.5 and 1.7 plants m−2, respectively) and no-till favoring (P = 0.05) forage kochia establishment (2.3 and 0.8 plants m−2, respectively). Transplants of these two species reduced halogeton frequency by 52% relative to the control. Moreover, this interference of halogeton establishment by Russian wildrye and forage kochia had extended to 50 cm distal from transplant by the second year of the study. By the third year (2014), transplant survival and halogeton frequency were highly correlated (r = −0.61, P = 0.0001), indicating the importance of plant persistence. Results indicate that Russian wildrye and forage kochia can establish and reduce halogeton frequency, thereby providing an opportunity for rehabilitation of halogeton-invaded areas.

Seed Selection by Desert Rodents: Implications for Enhancing Seedling Establishment of Indian Ricegrass (Achnatherum hymenoides)

Abstract. Seeds of many plant species are dispersed by seed-caching rodents that place groups of seeds in superficially buried scatterhoard caches. A case in point is Indian ricegrass (Achnatherum hymenoides), an important forage plant on arid western rangelands for which seedling recruitment comes largely from scatterhoards made by desert heteromyid rodents. A “diversionary seeding” strategy has been attempted for enhancing Indian ricegrass seedling recruitment by deploying commercially available seeds on the soil surface to divert rodents from recovering scatterhoards of Indian ricegrass seeds. The probability of such a passive restoration approach succeeding is likely affected by the relative desirability to rodents of Indian ricegrass seeds versus diversionary seeds. We conducted laboratory experiments to test preferences of Merriam's kangaroo rat (Dipodomys merriami), a primary dispersal agent of Indian ricegrass seeds, for Indian ricegrass seeds versus seeds of 5 diversionary seed candidates. Indian...

Cheatgrass invasion alters the abundance and composition of dark septate fungal communities in sagebrush steppe

Invasive, non-native plant species can alter soil microbial communities in ways that contribute to their persistence. While most studies emphasize mycorrhizal fungi, invasive plants also may influence communities of dark septate fungi (DSF), which are common root endophytes that can function like mycorrhizas. We tested the hypothesis that a widespread invasive plant in the western United States, cheatgrass (Bromus tectorum L.), influenced the abundance and community composition of DSF by examining the roots and rhizosphere soils of cheatgrass and two native plant species in cheatgrass-invaded and noninvaded areas of sagebrush steppe. We focused on cheatgrass because it is negatively affected by mycorrhizal fungi and colonized by DSF. We found that DSF root colonization and operational taxonomic unit (OTU) richness were significantly higher in sagebrush (Artemisia tridentata Nutt.) and rice grass (Achnatherum hymenoides (Roem. &amp; Schult.) Barkworth) from invaded areas than noninvaded areas. Cheatgrass roots had similar levels of DSF colonization and OTU richness as native plants. The community composition of DSF varied with invasion in the roots and soils of native species and among the roots of the three plant species in the invaded areas. The substantial changes in DSF we observed following cheatgrass invasion argue for comparative studies of DSF function in native and non-native plant species.

A mast-seeding desert shrub regulates population dynamics and behavior of its heteromyid dispersers.

Granivorous rodent populations in deserts are primarily regulated through precipitation‐driven resource pulses rather than pulses associated with mast‐seeding, a pattern more common in mesic habitats. We studied heteromyid responses to mast‐seeding in the desert shrub blackbrush (Coleogyne ramosissima), a regionally dominant species in the Mojave–Great Basin Desert transition zone. In a 5‐year study at Arches National Park, Utah, USA, we quantified spatiotemporal variation in seed resources in mast and intermast years in blackbrush‐dominated and mixed desert vegetation and measured responses of Dipodomys ordii (Ord's kangaroo rat) and Perognathus flavescens (plains pocket mouse). In blackbrush‐dominated vegetation, blackbrush seeds comprised >79% of seed production in a mast year, but 0% in the first postmast year. Kangaroo rat abundance in blackbrush‐dominated vegetation was highest in the mast year, declined sharply at the end of the first postmast summer, and then remained at low levels for 3 years. Pocket mouse abundance was not as strongly associated with blackbrush seed production. In mixed desert vegetation, kangaroo rat abundance was higher and more uniform through time. Kangaroo rats excluded the smaller pocket mice from resource‐rich patches including a pipeline disturbance and also moved their home range centers closer to this disturbance in a year of low blackbrush seed production. Home range size for kangaroo rats was unrelated to seed resource density in the mast year, but resource‐poor home ranges were larger (P < 0.001) in the first postmast year, when resources were limiting. Blackbrush seeds are higher in protein and fat but lower in carbohydrates than the more highly preferred seeds of Indian ricegrass (Achnatherum hymenoides) and have similar energy value per unit of handling time. Kangaroo rats cached seeds of these two species in similar spatial configurations, implying that they were equally valued as stored food resources. Blackbrush mast is a key resource regulating populations of kangaroo rats in this ecosystem.

Rangeland Monitoring Reveals Long-term Plant Responses to Precipitation and Grazing at the Landscape Scale

Managers of rangeland ecosystems require methods to track the condition of natural resources over large areas and long periods of time as they confront climate change and land use intensification. We demonstrate how rangeland monitoring results can be synthesized using ecological site concepts to understand how climate, site factors, and management actions affect long-term vegetation dynamics at the landscape-scale. Forty-six years of rangeland monitoring conducted by the Bureau of Land Management (BLM) on the Colorado Plateau reveals variable responses of plant species cover to cool-season precipitation, land type (ecological site groups), and grazing intensity. Dominant C3 perennial grasses (Achnatherum hymenoides, Hesperostipa comata), which are essential to support wildlife and livestock on the Colorado Plateau, had responses to cool-season precipitation that were at least twice as large as the dominant C4 perennial grass (Pleuraphis jamesii) and woody vegetation. However, these C3 perennial grass responses to precipitation were reduced by nearly one-third on grassland ecological sites with fine- rather than coarse-textured soils, and there were no detectable C3 perennial grass responses to precipitation on ecological sites dominated by a dense-growing shrub, Coleogyne ramosissima. Heavy grazing intensity further reduced the responses of C3 perennial grasses to cool-season precipitation on ecological sites with coarse-textured soils and surprisingly reduced the responses of shrubs as well. By using ecological site groups to assess rangeland condition, we were able to improve our understanding of the long-term relationships between vegetation change and climate, land use, and site characteristics, which has important implications for developing landscape-scale monitoring strategies.