The productivity and stability of cattle production on rangelands depends on the maintenance of a dense and productive perennial grass-dominated resource base, which is contingent on appropriate grazing and recovery periods. We investigated the effect of simulated trampling, dung inputs, frequency of defoliation in the previous growing season (grazing history), and timing of recovery periods on various grassland functional responses in two experiments in western and northwestern Botswana. A field-based clipping experiment at the individual tuft scale demonstrated that perennial grasses are most productive when rested for a full growing season, but that productivity of the highly palatable soft leaved Brachiaria nigropedata Ficalho & Hiern. decreases exponentially with increasing clipping frequency in the previous season (a lagged effect of grazing history). This species was also more productive in the next season when rested during the early than late growing season. The less palatable needle-leaved Stipagrostis uniplumis Licht. ex Roem. & Schult. was less resistant to defoliation than B. nigropedata and decreased equally at each clipping frequency regardless of season. A second field-based experiment at the plot scale demonstrated that a full-season recovery period increased tuft densities while its combination with dung increased cover. The effects of hoof trampling on sandy nutrient-poor grasslands appear to be less significant compared with grasslands on fertile soils. Thus, optimal livestock management strategies should aim to promote season-long grazing of both palatable and unpalatable species to disadvantage the less grazing-tolerant unpalatable species and full growing season recovery periods to ensure optimal recovery and future productivity.

Buffelgrass savanna is becoming widespread in aridland ecosystems around the world following invasion or deliberate land conversion for cattle forage. There is still a gap of information regarding functional and ecohydrological aspects such as carbon, water, and greenhouse gas exchanges in these highly productive novel ecosystems where buffelgrass is an exotic species. We measured net ecosystem CO₂ exchange (NEE), ecosystem respiration (R_eco), gross primary production (GPP), and evapotranspiration (ET) with eddy covariance techniques over a buffelgrass savanna established for cattle grazing, approximately 30 yr ago within the Sonoran Desert. The savanna was a net carbon sink (NEE -230 g C/m²/yr) during both a year with above average and one with below-average precipitation (NEE -84 g C/m²/yr). Water loss through evapotranspiration (ET) was similar to total annual rainfall input. Up to 62% of the annual fixed carbon and 75% of ET occurred during the summer monsoon season, when 72–86% of annual rainfall occurred and buffelgrass was active. ET from summer months explained 73% of variation in NEE, with an average ET of 50 mm H₂O/month needed to turn the ecosystem into a net carbon sink during this season. Other seasons in the year, when buffelgrass was dormant, contributed with up to 48% of annual fixed carbon but with higher water use efficiency (-NEE/ET). Wediscuss the importance of the seasonal variability in R_eco, GPP, and ET processes and the phenology of native plant species for the net carbon uptake through the year for this managed novel ecosystem.

Understanding the influence of grazing management and environmental drivers on net ecosystem exchange of CO₂ (NEE) is essential for optimizing carbon (C) uptake in rangelands. Herein, using 15 treatment-years (two 3-yr experiments, one with three grazing treatments, the other two) and Bowen ratio flux towers, we evaluated the influence of grazing intensity, soil water content (SWC), and plant cover (Normalized Difference Vegetation Index, or NDVI) on NEE in Colorado shortgrass steppe. Among several soil water and plant cover traits evaluated over 6-yr, early season (April, DOY 91–120) SWC and early season (DOY 130) NDVI weremost highly correlated with NEE (-0.96 and-0.98, respectively) during the second quarter (April to June) of the year and also over the entire growing season (April to September;-0.97 and-0.96). Due to the strong effect of early-season SWC, an average of 166 gm^-2 CO₂ were lost in 2 yr with dry spring weather, compared with an average annual uptake of 218 g m^-2 CO₂ in 4 yr with more abundant early-season precipitation and plant cover. Grazing effects on NEE were also apparent. In one experiment, moderate grazing resulted in annual CO₂ uptake of 267 g m^-2 CO₂ over 3 yr compared with essentially zero NEE in heavily grazed pasture. However, that treatment difference in annual NEEwas only half that experienced between dry and wet years. Similar trends were observed in a second experiment, although results were insignificant. Results suggest that the recommended moderate grazing intensity for the Colorado shortgrass steppe is near optimal for CO₂ uptake under season-long continuous grazing, with annual climatic variability sometimes being more influential. To enhance C sequestration in the western Great Plains of North America, grazing management strategies should emphasize flexible and adaptive practices that consider early-season SWC and promote vegetation cover during the key early spring growth period.

Pinyon-juniper (Pinus spp.-Juniperus spp.) encroachment and decliningmule deer (Odocoileus hemionus) populations in western Colorado have necessitated management for increased forage. Pinyon-juniper removal is one such technique; however, it is unclear which method of tree removal most effectively promotes forage species. We conducted an experiment to quantify understory responses to mechanical pinyon-juniper removal and seed additions in a blocked design using three different methods: anchor-chaining, rollerchopping, and mastication. Blocks contained each mechanical and seeding treatment along with an untreated control. Seven blocks across two sites, North Magnolia (NM, 4 blocks) and South Magnolia (SM, 3 blocks), were treated during the fall of 2011. Half of each plot was seeded before or during mechanical treatment with a mix of grasses, shrubs, and forbs. After two growing seasons, biomass of perennial grasses was 90–160 kg · ha^-1 in mechanically treated plots compared with 10 kg · ha^-1 in untreated controls. There were no differences, however, between mechanical treatments for any perennial plant species. Response of annual plant species depended on mechanical treatment type and site. Rollerchopping had higher exotic annual grass cover than mastication or control at NM and higher exotic annual forb cover than chaining or control at SM. Rollerchopping was the only treatment to have higher native annual forb cover than control in the absence of seeding. Seeding increased native annual forb biomass in mastication compared with control. Seeding also increased shrub density at SM, which had fewer shrubs pretreatment relative to NM. Results suggest any type of mechanical removal of pinyon-juniper can increase understory plant biomass and cover. Seeding in conjunction with mechanical treatments, particularly mastication, can initially increase annual forb biomass and shrub density. Finally, different understory responses between sites suggests that pretreatment conditions are important for determining outcomes of pinyon-juniper removal treatments.

Many Wyoming big sagebrush (Artemisia tridentata Nutt. ssp. wyomingensis) communities are invaded by exotic annuals, especially cheatgrass (Bromus tectorum L.), promoting larger and more frequent wildfires. Mowing sagebrush can reduce fire risk. To identify community features favoring regeneration of native perennials over exotic annuals, we compared paired, adjacent unmowed and mowed areas treated between 2001 and 2010 at 76 sites across northern and central Nevada. We quantified soil surface and foliar cover in 12 cover groups, as well as slope, aspect, elevation, and time since mowing (0–10 years). We identified unmowed cover characteristics and site covariates that best predicted herbaceous cover in mowed areas and differences in herbaceous cover between adjacent mowed and unmowed areas. Mowed areas had significantly (P < 0.01) more absolute cover (%) of litter (14.6), perennial grasses (4.9), cheatgrass (2.0), and exotic forbs (1.1) and less sagebrush (-13.5), bare soil (-11.4), moss (-3.3), and rock (-0.8) than adjacent unmowed areas. Except for sagebrush, all cover group values were correlated between unmowed and mowed areas. The “perennial balance” (perennial minus annual herbaceous cover) was positive at 75% (57) of mowed areas and increased from unmowed to mowed areas at 51 sites. A positive perennial balance in mowed areas was more likely where paired unmowed areas lacked cheatgrass, had greater cover of perennial grass, and less of exotic forbs. Likewise, sites whose unmowed areas had > 30% sagebrush cover consisting of smaller plants had larger gains in perennial balance from unmowed to mowed areas. An increase in perennial balance from unmowed to mowed areas was more likely in central and northeastern Nevada and at sites mowed more recently. To encourage perennial grasses over annual herbaceous species in Wyoming big sagebrush communities, mowing is better suited to locales lacking exotic annuals and retaining ample cover of perennial grasses and sagebrush of smaller size.

Objectives of postfire seeding in the Great Basin include reestablishment of perennial cover, suppression of exotic annual weeds, and restoration of diverse plant communities. Nonconventional seeding techniques may be required when seeding mixes of grasses, forbs, and shrubs containing seeds of different sizes. We conducted an operational-scale experiment to test the effectiveness of two rangeland drills (conventional and minimum-till) for seeding native plant mixes following wildfire in Wyoming big sagebrush (Artemisia tridentata Nutt. ssp. wyomingensis Beetle & Young) communities. Both drills were configured to place small and large seeds in alternate rows. We hypothesized that the minimum-till drill's advanced featureswould improve establishment compared with the conventional drill. We also hypothesized that theminimum-till drill would cause less damage to residual perennials, whereas the conventional drill would have a greater impact on annual weeds. The experiment was replicated at three burned sites and monitored for 2 yr at each site. Seeded plant establishment was lowest at a low-precipitation site that became dominated by exotic annuals. Another site had high perennial grass establishment, which effectively suppressed exotic annuals, while a third site attained high diversity of seeded species and life forms but became invaded by exotic annuals in plant interspaces. Small-seeded species generally established better with the minimum-till drill equipped with imprinter wheels than the conventional drill with drag-chains. However, large-seeded species frequently established better with the conventional drill despite its lack of depth bands and press wheels. Soil disturbance associated with the conventional drill had a negative effect on residual perennials and exotic annuals at some sites. Results indicate that different drill features are advantageous in different ways, but that either of the tested drills, if properly used, can be effective for seeding native plant mixes provided site conditions are otherwise favorable for seedling establishment.

We determined the feasibility of using unmanned aerial vehicle (UAV) video monitoring to predict intake of discrete food items of rangeland-raised Raramuri Criollo non-nursing beef cows. Thirty-five cows were released into a 405-m² rectangular dry lot, either in pairs (pilot tests) or individually (experiment tests), that contained 12 food bowls arranged in an open semicircle and placed approximately 1 m apart. Four bowls containing either long alfalfa hay (AH, 200 g), long Sudangrass hay (SH, 200 g), or cottonseed cake (CC, 50 g) were alternated (CC, AH, SH) using the same sequence in all tests. Video footage of all arena tests was acquired with a three dimensional Robotics Y6 Multi-copter fitted with a two-axis brushless gimbal and a GoPro Hero 3 Silver Digital Camera. Video files were processed to extract a total of 4 893 two-second-interval still images that were viewed to determine cow feeding activity. Cows that were naïve to the sound of the UAV fed as frequently (P > 0.05) as their adapted counterparts during 12-min pilot tests. Significant positive correlations (r=0.68-0.91; P < 0.05) between video-derived feeding frequency estimates and amount of AH, SH, and CC consumed per bowl were observed during the individual 4-min experiment tests. Our results suggest that UAV video monitoring could be a useful tool to monitor feeding behavior of rangeland cows.

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 plantsm^-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.

The impact on palatable shrubs when herbivores have access to high-quality food is unclear. We determined if providing high-quality food and increasing white-tailed deer (Odocoileus virginianus) density reduced growth and altered nutritional quality of two palatable shrub species. We maintained target densities of 13, 31, or 50 deer km^-2 in six 81-ha^-1 enclosures on each of two ranches. We provided nutritious, dry feed ad libitum in one of each pair of enclosures with similar densities on each ranch. We measured height and width of Texas kidneywood (Eysenhardtia texana Scheele) and spiny hackberry (Celtis ehrenbergiana [Klotzsch] Liebm), measured hackberry thorns, and estimated crude protein. Plants were protected from browsing with wire exclosures in 2005; a similar-sized unprotected plant was paired with each protected plant. We estimated density of shrub species using twenty 3 × 50mbelt transects/enclosure June 2005, 2007-2012. Growth of protected and unprotected kidneywood was similar (P ≥ 0.88) at 13 deer km^-2, but growth was reduced (P ≤ 0.05) by higher deer densities. Protection from browsing and increasing deer density did not influence (P ≥ 0.25) size of spiny hackberry. Browsed kidneywood plants had a 34% lower crude protein (P ≤ 0.01) compared with protected plants when deer did not have access to feed. Spiny hackberry protein was greater (P ≤ 0.05) in unprotected plants compared with protected plants at 50 deer km^-2. Response of Texas kidneywood density at > 1.5-mtall to deer density depended on year (P=0.04), with no effect of deer density (P ≥ 0.10) on spiny hackberry density. Density of both shrubs was similar (P > 0.14)with and without supplement. Access to feed does not alter effects of browsing on these sympatric shrubs; however, responses to increasing herbivore density contrast. Texas kidneywood is less tolerant of herbivory than spiny hackberry.

Tragelaphus strepsiceros (greater kudu) has adapted to the harsh conditions of southern Africa's mopani woodland. However, there is still limited information on the diet composition and selection of browse by greater kudu, particularly during the wet season. This poses a challenge to manage these ungulates effectively within their habitat. The study used rumen content to quantify the diet composition of greater kudu during thewet season. The study was conducted at the Sandown Game Farm, Limpopo Province, South Africa. Rumen samples were collected fromfour adult female and four adult male greater kudu culled inMarch 2015 and statistically analyzed using the t-test: paired two sample for means and Pearson's correlation coefficient analysis. Findings show that Combretum apiculatum contributed most (43%) to the diet of greater kudu during the wet season. Other browse plant species were Sclerocarya birrea (24%), Colophospermum mopane (12%), and Acacia nigrescens (8%), with the contribution of the remaining species to the diet being insignificant. Leaves were the plant parts browsed most often and contributed 81% to the diet during this season. The remaining 19% of the diet consisted mainly of S. birrea fruit. Gender differences in diet selection were observed. The diet of female greater kudu consisted mainly of C. apiculatum (44%) and C. mopane (20%), while the diet of male greater kudu mostly contained S. birrea (38%) and C. apiculatum (34%). Implications for the management and conservation of greater kudu in mopani veld are discussed.