Ratio Of Grass Research Articles

Successful pollinator seed mixes include low grass density and high forb richness across a range of total seeding densities

Pollinator habitat restorations and enhancements are an important approach to mitigate pollinator declines due to habitat loss and other stressors. Foraging resources can be provided by wildflower plantings grown from seed mixes composed of pollinator‐friendly plant species. Despite clear evidence on the benefits of such plantings for bees and other pollinators, there is limited knowledge on how variation in multiple seed mix design parameters affects floral resources over time. Such information is crucial to improve the effectiveness of different habitat applications and to potentially lower seed costs, which remain an impediment to adoption. We conducted an incomplete factorial field experiment to test the impacts of density, diversity, and forb:grass ratio of seed mixes on floral resource availability and phenological coverage of the resulting plantings. We quantified floral area and phenological coverage over the whole blooming season for three consecutive years in replicated plots of wildflower mixes in two regions of the U.S.A, Northern California's Central Valley and Midwestern Tallgrass Prairie. When different seed densities were fully replicated (e.g. within high forb:grass seed ratios in Minnesota, or forb‐only seedings in California), seeding density had no further impact on floral area and floral phenological coverage.

Production of biosurfactant sodium lignosulfonate (NaLS) using elephant grass based lignin (Pennisetum purpureum) and NaHSO3

Elephant grass (Pennisetum purpureum) is an animal feed ingredient, especially ruminants with a lignocellulose content of 40.85% and lignin of 21.5% and can be used as a raw material for making biosurfactant sodium lignosulfonate. Biosurfactant is an amphiphilic molecule and has biodegradability. This study aims to obtain data on the effect of NaHSO3 concentration, reaction time, and the ratio of elephant grass: NaHSO3 on the sodium lignosulfonate content, yield, degree of sulfonation, and physico-chemical properties of sodium lignosulfonate obtained. This study consists of 3 treatment factors, namely NaHSO3 concentration, reaction time, and mass ratio of elephant grass : NaHSO3. The results showed that sodium lignosulfonate can be produced from elephant grass using direct sulfonation process. The best treatment combination was 80% concentration and 155 minutes reaction time which produced sodium lignosulfonate content of 20.619 mg/L and 65.83% yield. The physicochemical properties are: density 1.4061 g/mL, degree of sulfonation 57.73%, completely soluble in water, smells a little sulfur, has a brownish yellow color, pH 5, and the results of functional group analysis showed a change in functional groups.

Anaerobic digestion of distillery wastewater and napier grass: Characterization and process performance parameters

The BOD/COD ratio of napier grass (NG) + distillery wastewater (DWW) was found to be 0.4982, which reflected that the biodegradability of organic material is high and can be degraded and treated efficiently via biological processes. Moreover, further reductions in total solids (TS) and volatile solids (VS) were observed after thermal pretreatment at temperatures of 60°C and 100°C. VS/TS ratio also increased from 0.8767 to 0.9508 indicating a more significant proportion of organic matter are favorable for biogas production. This was evidenced by the resulting removal efficiencies ranging from 15% to 32% and 23% to 42%, for TS and VS, respectively. Overall, the study reported relevant effects of the application of thermochemical pretreatment in the process performance parameters in anaerobic digestion.

Qualitative evaluation of total mixed ration silage containing forage cactus and guinea grass as a nutritional alternative for feedlot-finished sheep

ABSTRACT This study aimed to evaluate the fermentation characteristics, microbial populations, losses, aerobic stability and chemical composition of total mixed ration based on forage cactus and different ratios of Guinea grass at four storage times (7, 15, 60 and 100 days). Five diets were formulated with forage cactus as the main ingredient, with varying Guinea grass inclusion ratios: 0, 10, 20, 25 and 30% on a dry matter basis. The experimental design used was a completely randomised design with a factorial arrangement and three replicates. The silages had pH values of approximately 4.0. Lactic acid bacteria were predominant in all silages, and this predominance increased after 7 days of ensiling in all diets, ranging from 8.0–10.1 log10 cfu g−1 of silage. Silages with 10% and 20% guinea grass showed aerobic deterioration, while the others remained stable throughout the aerobic stability test. Guinea grass in combination with forage cactus can be added in total mixed ration silages up to a level of 30%, without compromising the chemical composition, silage losses or fermentative profile. However, considering aerobic stability, the addition of 10% and 20% guinea grass resulted in greater deterioration after 48 h of exposure to air.

Weed flora composition in a young olive orchard as affected by fertilizer types

Manure is a useful source of nutrients in olive orchards, but its effect on weed growth in such an ecosystem has not been studied. A field experiment was conducted in a six-year old olive orchard (cv. Chondrelia Chalkidikis) in northern Greece to study the effects of two forms of fertilization (inorganic fertilizer and composted cow manure) on weeds abundance and weed flora composition (species diversity and dominance). A randomized complete block design with three treatments (inorganic fertilizer, 150 kg N ha−1 plus 205 kg P2O5 ha−1 plus 205 kg K2O; composted cow manure, 20 Mg dry weight ha−1; and control) replicated three times was used. Inorganic fertilizer and composted cow manure had no significant effect on the number of weed species (F = 0.288, P > 0.05), but improved olive fruit yield by 61.6% and 57.1%, respectively, compared with the non-fertilized control. Both inorganic fertilizer and composted cow manure increased the weeds dry biomass by 133.4% and 80.8%, respectively, compared with the non-fertilized control. There was a decrease in the biomass proportion (percentage of the total weed biomass) of annual species with composted cow manure (x2 = 6.72, P < 0.05), while no significant change in the biomass ratio of grasses and broadleaf weeds was observed. Fertilization increased the growth of Chenopodium album, mainly with the addition of inorganic fertilization; and Sonchus oleraceus, slightly more with the addition of composted cow manure. Centaurea solstitialis and Daucus carota had a high proportion only in the non-fertilized control plots. Composted cow manure can be used as an alternative fertilizer in olive orchards, without enriching weed flora in terms of species number. Long-term experiments would be useful to confirm the influence of composted cow manure on weed flora of olive orchards.

Selective grazing behavior of Coopworth sheep in New Zealand

This study focused on confirming the grazing selectivity of sheep, more and less selective, in pasture in New Zealand, under two different phenological stages of forage. Two experiments were conducted: 1) Comparison of selective and non-selective sheep in pasture irrigated with perennial ryegrass and white clover. 2) A comparison was performed with selective and non-selective sheep in pasture with a high rate of senescence composed of perennial ryegrass, barley and barnyard grass. The botanical composition of the forage was studied using the point analysis method. The forage canopy height and forage mass were measured using a disk meter. There was no significant difference between treatments in the variables analyzed. In the first experiment there was a lower clover ratio and increased litter ratio for the botanical composition and point analysis. With regards to height, there was a decrease in grazed clover pasture and grazed ryegrass pasture, as well as the forage mass. In the second experiment the grass ratio, clover height and forage mass decreased and the proportion of litter and grazed grass increased. Despite the differences in the botanical and morphological aspects of the pasture, the selective and non-selective sheep showed similar grazing behavior.

Quantifying the effect of chemical bush control of Senegalia mellifera on vegetation production in the Eastern Kalahari Bushveld, South Africa

Bush encroachment is the invasion of whole landscapes by indigenous and alien woody species. An imbalance in the ratio of grasses to bushes is a consequence of bush encroachment due to competition for moisture, nutrients and sunlight. This imbalance results in a decrease in grass cover, plant biodiversity and grazing capacity, leading to severe economic losses. Several methods exist to reduce high woody plant densities, including mechanical, manual, biological or chemical control. In this study, we assessed the structural and compositional attributes of the grass layer and compared these to the woody vegetation structure for herbicide-controlled rangelands and the no chemical control. The main objective was to evaluate the potential of chemical control to restore an open savanna system dominated by perennial grasses. Woody-dominated vegetation resulting from long-term overgrazing was assessed and compared to chemically controlled sites. Results revealed that chemical control treatment increased forage production and maintained woody-patch conservation. After the treatment, the sites were characterised by more productive and desirable woody species. The re-encroachment of woody species at all bush-controlled sites is possible. A follow-up control programme to manage and mitigate encroachment needs to be implemented when mitigating bush encroachment.

Water causes divergent responses of specific carbon sink to long-term grazing in a desert grassland

Heavy grazing generally reduces grassland biomass, further decreasing its carbon sink. Grassland carbon sink is determined by both plant biomass and carbon sink per unit biomass (specific carbon sink). This specific carbon sink could reflect grassland adaptative response, because plants generally tend to adaptively enhance the functioning of their remaining biomass after grazing (i.e. higher leaf nitrogen content). Though we know well about the regulation of grassland biomass on carbon sink, little attention is paid to the role of specific carbon sink. Thus, we conducted a 14-year grazing experiment in a desert grassland. Ecosystem carbon fluxes, including net ecosystem CO2 exchange (NEE), gross ecosystem productivity (GEP) and ecosystem respiration (ER), were measured frequently during five consecutive growing seasons with contrasting precipitation events. We found that heavy grazing reduced NEE more in drier (−94.0 %) than wetter (−33.9 %) years. However, grazing did not reduce community biomass much more in drier (−70.4 %) than wetter years (−66.0 %). These meant a positive response of specific NEE (NEE per unit biomass) to grazing in wetter years. This positive response of specific NEE was mainly caused by a higher biomass ratio of other species versus perennial grasses with greater leaf nitrogen content and specific leaf area in wetter years. In addition, we also detected a shift of grazing effects on specific NEE from positive in wetter years to negative in drier years. Overall, this study is among the first to reveal the adaptive response of grassland specific carbon sink to experimental grazing in plant trait view. The stimulation response of specific carbon sink can partially compensate for the loss of grassland carbon storage under grazing. These new findings highlight the role of grassland adaptive response in decelerating climate warming.

ANALISIS PERBANDINGAN PAKAN RUMPUT DENGAN PAKAN PELEPAH DAN DAUN SAWIT PADA PETERNAKAN KAMBING DI KABUPATEN NAGAN RAYA

Goat farming in Indonesia is currently growing rapidly through the adoption of science and technology. However, this development is not evenly distributed throughout Indonesia, this is because some regions still apply livestock systems with limited existing knowledge. Based on the results of observations made, some goat breeders have started to use fronds and palm fronds from maintenance plants and do not have economic value in Nagan Raya District, Aceh Province. The use of palm fronds as ruminant feed ingredients requires beneficial treatment to reduce the lignin content found in palm fronds, one of the technologies used is fermentation, this is to improve feed quality. The purpose of this study was to determine the ratio of grass feed to fronds and palm leaf feed for goats in Nagan Raya District. This research was conducted in Nagan Regency by calculating the ratio of Total Cost, Total Revenue and Profit Analysis on farms using grass goat feed with fronds and palm leaf goat feed. Based on the results of this study, it was found that farmers who used fronds and palm leaves forage earned a greater profit of 69.97% compared to farmers who used regular grass feed. This significant difference was found in the cost of providing grass feed which is more expensive than oil palm feed. Meanwhile, based on the farmer's information, there is no difference between the two types of feed in terms of the cost of vitamins, drugs and care provided.

PRODUKSI, KOMPOSISI BOTANI DAN KAPASITAS TAMPUNG PADANG PENGGEMBALAAN ALAM DESA MAUBOKUL KECAMATAN PANDAWAI KABUPATEN SUMBA TIMUR PADA MUSIM HUJAN (Production, botanical composition and carrying capacity of pasture in Maubokul Village, Pandawai.....

This experiment aims to analyze the production, botanical composition, and carrying capacity of pasture in the Maubokul Village, Pandawai District, East Sumba Regency. The experiment was conducted on March 1th to April 30th 2022. The experiment used survey method, measurement, and direct observations in the field. Forage production measured by actual weight estimate method with 1 m x 1 m of the frame as tool utilization. Botanical composition measured using the summed dominance ratio method, as well as the carrying capacity measured using the viosin formula. The data obtained were tabulated and calculated to obtain the total forage production, botanical composition, and carrying capacity. The results showed that the pasture in Maubokul Village, Pandawai District, had a fresh production of 5.182 kg/ha, dry matter production of 1.505 kg/ha, Summed Dominance Ratio (SDR) of grass 65,21%, legumes 18,04%, and weeds 16,75%. The pasture also has a carrying capacity of 1,12 AU/ha/year. In conclusion, pasture in Maubokul Village, Pandawai District were dominated by natural grass with high capacity during the rainy season.

Precipitation increase counteracts warming effects on plant and soil C:N:P stoichiometry in an alpine meadow

Temperature and precipitation are expected to increase in the forthcoming decades in the northeastern Qinghai-Tibetan Plateau, with uncertain effects of their interaction on plant and soil carbon:nitrogen:phosphorus (C:N:P) stoichiometry in alpine ecosystems. A two-year field experiment was conducted to examine the effects of warming, precipitation increase, and their interaction on soil and plant C:N:P stoichiometry at functional groups and community level in an alpine meadow. Warming increased aboveground biomass of legumes and N:P ratios of grasses and community, but did not affect soil C:N:P stoichiometry. The piecewise structural equation model (SEM) indicated that the positive effect of warming on community N:P ratio was mainly resulted from its positive influence on the aboveground biomass of functional groups. Precipitation increase reduced C:N ratios of soil, grasses, and community, indicating the alleviation in soil N-limitation and the reduction in N use efficiency of plant. SEM also demonstrated the decisive role of grasses C:N:P stoichiometry on the response of community C:N:P stoichiometry to precipitation increase. The interaction of warming and precipitation increase did not alter plant community and soil, N:P and C:P ratios, which was resulting from their antagonistic effects. The stable soil and plant community C:N:P stoichiometry raised important implications that the effect of warming was offset by precipitation increase. Our study highlights the importance of considering the interaction between warming and precipitation increase when predicting the impacts of climate change on biogeochemical cycles in alpine meadow ecosystems.

Efficacy of Grass and Concentrate Ratio on Milk Urea Nitrogen, Progesterone, and Pregnancy Status in Friesian Holstein

This study was conducted to know the influence of grass to concentrate ratio to milk urea nitrogen (MUN) level, progesterone level and pregnancy status in Friesian Holstein. A total of 18 dairy cows were randomly selected from the population. The cows were grouped based on feed and MUN and pregnancy. Milk sample collection was carried out once on the seventh day after estrus (D7) and tested with the Barthelot method for measuring urea nitrogen levels. Blood samples were taken three times, on the day of estrus (D0), seven days after estrus (D7), and twenty-two days after estrus (D22), and were tested using Immuno-Sorbent Assay (ELISA). Pregnancy examination was carried out at D90 after artificial insemination through rectal palpation. Based on the analysis, grass to concentrate ratio, progesterone level and MUN level showed no significant difference (p&gt;0.05) but it showed significantly different on milk yield (p&lt;0,05). Based on pregnancy status, progesterone level at D22 showed significantly different whereas at D0 and D7 showed insignificantly different. MUN level and grass to concentrate level also showed significantly different. It can be concluded that the ratio of grass and concentrate did not increase MUN level, progesterone level and pregnancy rate.

Produksi, Komposisi Botani dan Kapasitas Tampung Padang Penggembalaan Alam Desa Lai Ndeha Kecamatan Pandawai Kabupaten Sumba Timur

This experiment was conducted to analyze the production, botanical composition, and carrying capacity of pasture in the Lai Ndeha Village, Pandawai District, East Sumba Regency. The experiment was conducted on April 1-30, 2022. The experiment used survey method, measurement, and direct observations in the field. Forage production measured by actual weight estimate method with 1 m x 1 m of the frame as tool utilization. Botanical composition measured using the summed dominance ratio method, as well as the carrying capacity measured using the viosin formula. The data obtained were tabulated and calculated to obtain the total forage production, botanical composition, and carrying capacity. The results showed that the pasture in Lai Ndeha Village, Pandawai District, had a fresh production of 1.462.91 kg/ha, dry matter production of 702.89 kg/ha, Summed Dominance Ratio (SDR) of grass 69,60%, legumes 14,29%, and weeds 16,11%. The pasture also has a carrying capacity of 2,7 AU/ha/year. In conclusion, pasture in Lai Ndeha Village, Pandawai District were dominated by natural grasses with high capacity during the rainy season.

The Use of Whey Powder Additions for Grass Silage: Effects on Nutrient Content, Fermentation Properties and Aerobic Stability

The aim of this study was to determine the nutrient content, fermentation properties, and aerobic stability of grass ensiled with the addition of different doses of whey powder. Freshly cut grasses (Festuca arundinacea, Festuca rubra, Poa pratensis, and Lolium perenne) were ensiled with the addition of whey powder at a rate of 0, 2, 4, and 6% in the laboratory in 1.5-liter plastic jars with 4 replications. At the end of the 60-day ensiling period, the nutrient content, fermentation properties, and aerobic stability values of silages were investigated. The pH measurements revealed that the silages were of high quality. Although dry matter (DM), crude protein (CP), and ether extract (EE) values increased depending on the increase in whey powder rate in the silages, crude ash (CA), ADF, and NDF values decreased. The lowest pH and the highest Fleig Score (FS) were obtained in silage with a 6% whey powder addition. Except in the control group, no mold formation was detected in silage groups after the seven-day aerobic stability test. As a result, different mixing ratios of grass and whey powder did not cause negative results in silages and increased the quality. According to Fleig scores and aerobic stability results, the best quality silages were obtained from silages with 4 and 6% whey powder additions. It was concluded that the ensiling of grass with whey powder was effective in improving the nutritional and fermentation quality of silages and provided a partial solution to environmental pollution.

Effects of Legume–Grass Ratio on C and Nutrients of Root and Soil in Common Vetch–Oat Mixture under Fertilization

Legume–grass mixture can greatly improve soil fertility to support the sustainable productivity. Root litter is an important source of soil organic matter, but its link with soil nutritional status in forage mixtures is not clear. This study was aimed to uncover whether the relationship of carbon (C) and nutrients between root and soil would change with mixing ratio. Changes in organic C, nitrogen (N), and phosphorus (P) of root and soil were studied in a 2-year experiment with sole common vetch (Vicia sativa), sole oat (Avena sativa), and their mixtures of different mixing ratios under N, P, and N + P fertilization. Root C, N, and P concentrations decreased with decreasing proportion of common vetch in the grasslands. Nitrogen fertilization significantly improved root N concentration (by 4.5–10.1%), while P fertilization decreased root N concentration (by 10.1–18.4%). The effect of mixing ratio on soil C and nutrients was stimulated by fertilization, although soil C, N, and P contents barely changed with mixing ratio. Mixing and fertilization significantly affected C, N, and P stoichiometric ratios of root and soil (besides soil C:N). Soil C, N, and P contents were strongly positively correlated with root C concentration. The results indicated that increasing legume proportion in the mixture may improve root C and nutrients, which can be stimulated by fertilization. Root quality is closely correlated to soil nutritional status in the mixture. This study further reveals the mechanism how the root is potentially involved in affecting soil fertility and provides a scientific basis on the extensive use of common vetch-oat mixture in the Loess Plateau of China.

Intercrops of grass with legumes as green manure for agroecological systems

The stud article aimed to assess the accumulation and rates of nutrients in the biomass of the consortium of millet and leguminous plants for green fertilisation. The treatments were consortia of millet with four different leguminous plants: Cajanus cajan, Canavalia ensiformis, Mucuna aterrima, and Dolichos lablab. The treatments were distributed in a completely randomised design with four replications. The species of each consortium were planted in a line, at a distance of one metre apart. The aerial part of the plants was harvested after 90 days to determine the botanical composition, intercropping biomass, and the amount and accumulation of macronutrients in the biomass. The Millet mass did not differ among the consortia. However, among the legumes, M. aterrima has the highest mass (2806.31 kg/ha DM), which is reflected in the lower ratio of leguminous grasses in the millet consortium with M. aterrima (4.61). The consortia affected the rate and accumulation of P, B, and Fe. The biomass of the millet consortium with C. cajan presented the lowest rate. In addition, the accumulation of K, Mg, and Zn was low in this consortium. The biomass of millet intercrops with M. aterrima, D. lablab and C. ensiformis showed higher accumulations of K, Ca, and Mg. The highest accumulation of N was observed in the biomass of the consortium with M. aterrima (50.71 kg/ha). The rates and accumulations of Cu and Zn were higher in the consortium with M. aterrima. The consortium of millet with the leguminous plants is a sustainable alternative for fertilisation. The consortia with M. aterrima and D. lablab are the most promising ones, due to the higher proportion of plants.

Effect of Seeding Ratios of Alfalfa (Medicago sativa) and Rhodes Grass (Chloris gayana) Mixtures on Dry Matter Yield and Nutritive Quality of the Fodder

The study was conducted at Adami Tulu on-station and Shashemene (FTC) sites for two (2019-2020) consecutive years with the objective to determine the appropriate proportions of seeding ratio that could optimize the dry matter yield and quality of Alfalfa and Rhodes grass mixture. The treatment was laid out in a randomized complete block design (RCBD) with three replications. Different seeding ratios of Alfalfa and Rhodes grass were arranged according to the following treatments: T1; 100% Alfalfa +0 % Rhodes, T2; 0% Alfalfa +100% Rhodes, T3; 50% Alfalfa +50% Rhodes, T4; 75% Alfalfa +25% Rhodes and T5; 25% Alfalfa +75% Rhodes. The results showed that number of tillers per plant of Rhodes grass and leaf to stem ratio of alfalfa, CP% content, NDF% and ADF% were showed a significance (p&lt;0.05) difference among the seeding ratios. The result indicated that seeding ratio has significant (p&lt;0.05) effect on the total dry matter yield of the mixture of alfalfa and Rhodes at both sites. The highest dry matter yield (8.47 t ha-1 ) was obtained from seeding ratio of 25:75, followed by seeding ratio of 50:50 (7.84 tha-1 ). The land equivalent ratios for the mixture were more than one showing that mixture of alfalfa with Rhodes is more advantageous than pure stand of forage. The highest CP% content (21.2%) was recorded from pure stand of alfalfa followed by seeding ratio 75:25 (18.5%), 50:50 (16.8%) and 25:75 (14.6%) while pure stand of Rhodes grass produced the least (11.1%) CP% value. The highest values of NDF% (34.48%) and ADF% (21.25%) were obtained from pure stands of Rhodes grass while the least values were recorded from pure Alfalfa. Thus, it can be concluded that seeding ratio combination of 50:50 could be recommended for use in the study areas and similar agro-ecologies due to its high dry matter yield, good quality and more balanced mixture of forage.

Increased plant growth may offset soil carbon loss caused by warming in an alpine Sibiraea angustata shrub ecosystem on the eastern Qinghai-Tibet Plateau

The alpine shrub ecosystem on the Qinghai-Tibet Plateau, which reserves large amounts of carbon (C) and functions as an important potential C sink, is experiencing significant warming. However, we still lack a thorough understanding of the effects of warming on ecosystem C storage and allocation in above- and belowground components of plants and soils in these alpine shrub ecosystems. In this study, we employed a four-year field warming experiment in an alpine shrubland dominated by Sibiraea angustata on the eastern Qinghai-Tibetan Plateau. We investigated the effects of warming on C storage and allocation among the above- (i.e., leaf and stem) and belowground parts (i.e., coarse and fine roots) of shrubs and the above- and belowground parts of grasses and soils. Our results showed that warming significantly increased shrub leaf C storage by 18.8%, but shrub stem C storage did not respond to warming. Warming significantly increased the C storage of shrub coarse and fine roots by 7.7% and 139.4%, respectively. Warming significantly increased the C storage of the above- and belowground parts of grasses by 60.4% and 130.5%, respectively. As a result, warming significantly increased the C storage of both the above- and belowground parts of total plants by 8.8% and 49.1%, respectively. Moreover, warming significantly increased the C root:shoot ratios of alpine shrubs and grasses. Taken together, warming significantly increased the C storage of total plants by 1.23 kg C m−2, which primarily resulted from the belowground parts of plants (1.07 kg C m−2), and warming-induced increases in C storage of alpine shrub fine roots (0.86 kg C m−2) could approximately offset soil C losses (0.99 kg C m−2), as indicated by decreasing soil C storage under warming. Therefore, warming increased the ecosystem C sink by 0.24 kg C m−2. Our results highlight that alpine shrub fine roots play a dominant role in regulating the dynamics of ecosystem C balance and cycling in response to warming. Future climate warming will stimulate ecosystem C sequestration, largely because of increasing the growth of alpine shrub fine roots in these alpine shrublands on the Qinghai-Tibet Plateau.

Identifying Structural Thresholds in Annual Grass–Invaded Rangelands

Invasive plants have an increasing impact on the ecological and economic functions of natural systems. Cheatgrass (Bromus tectorum L.) is an invasive annual grass that is widely impactful throughout most of the western United States. Describing ecological and management thresholds in cheatgrass-invaded rangelands may help managers conserve native plant communities. The objective of this research was to determine if direct, predictable relationships exist between pretreatment vegetation conditions and post-treatment changes in perennial grass biomass following cheatgrass control. We sampled locations representing a gradient of cheatgrass-to–perennial grass ratios before and following application of two imazapic formulations—liquid imazapic with a water carrier and dry imazapic with sand/granular carrier—at field sites near Saratoga and Pinedale, Wyoming. We monitored vegetation responses 1 yr before treatment and 2 yr following treatment. We observed a general pattern that posttreatment increases in perennial grass biomass were greater where pretreatment relative cheatgrass canopy cover was higher, and magnitudes of increase varied according to site conditions. We tentatively suggest thresholds at ratios of pretreatment cheatgrass-to–perennial grass cover at 4:1, where perennial grass biomass increased following herbicide treatment and > 10:1, beyond which increases in perennial grasses were no longer observed. Such ratios provide a starting point for threshold identification in cheatgrass-invaded rangelands that may be transferrable across plant communities but need to be explored at a broader scale to adequately make management recommendations.

Satellite-observed shifts in C3/C4 abundance in Australian grasslands are associated with rainfall patterns

Species composition is a key determinant of grassland ecosystem function and resilience. Climate change is predicted to alter the distribution of cool season (C3) and warm season (C4) grasses, however, the lack of spatial distributions and temporal variations of grass functional type information severely limits our understanding of climate impacts on grasslands. This study classified C3 and C4 grasses per pixel according to the peak of growing season generated from Enhanced Vegetation Index time series. From 2003 to 2017, the C3-C4 composition of Australian rain-fed grasslands and pastures was mapped at 500 m resolution on an annual basis across a wide geographical range (10°S – 45°S), and revealed extreme inter-annual fluctuations. Over the 15-year period, the satellite-derived ratio of C4 to C3 grasses significantly increased (p < 0.05), indicating a long-term shift in community composition that was confirmed with 182,911 Atlas of Living Australia ground observations. The most pronounced changes occurred in mid-latitude transitional areas where C3 and C4 grasses co-dominate. Our climate analysis indicated the inter-annual fluctuations of C4/C3 grass ratios were significantly associated (p < 0.05) with warm/cool season rainfall ratios, and not with temperature or annual rainfall. This suggests that an increase in the warm/cool season rainfall ratio favors C4 grasses and a decrease in the warm/cool season rainfall ratio favors C3 grasses. Our findings reveal spatially-detailed dynamics of grasslands and demonstrate large-scale grassland compositional changes over 15 years. The grass composition maps should help improve ecological forecasting of grass distributions and enable researches on grassland ecosystem responses to climate change that are relevant to both adaptation of rangeland agricultural and fire management practices. Our study should also help predict grass distribution under future climate conditions, and assist in the accurate modelling of global water, carbon, and energy exchanges between the land surface and atmosphere.