Biomass Of Perennial Grasses Research Articles

Nutrients addition decreases soil fungal diversity and alters fungal guilds and co-occurrence networks in a semi-arid grassland in northern China

Anthropogenic eutrophication is known to impair the diversity and stability of aboveground community, but its effects on the diversity, composition and stability of belowground ecosystems are not yet fully understood. In this study, we conducted a 9-year nitrogen (N) and phosphorus (P) addition experiment in a semi-arid grassland of Northern China to elucidate the impacts of nutrients addition on soil fungal diversity, functional guilds, and co-occurrence networks. The results showed that N addition significantly decreased soil fungal diversity and altered fungal community composition, whereas P addition had no impact on them. The relative abundance of arbuscular mycorrhizal fungi and leaf_saprotroph were reduced by N and P addition, but P addition enhanced the abundance of saprotrophic fungi. Co-occurrence network analysis revealed that N addition destabilized fungal network complexity and stability, while P addition slightly increased the network complexity. Additionally, the network analysis of N × P interaction revealed that P addition mitigated negative effects of N addition on network complexity and stability. Structural equation modeling (SEM) results suggested that nutrients addition directly or indirectly influenced the fungal community structure through the loss of plant richness and the increase of perennial grass biomass. These findings indicate that in comparison to P addition, N addition exhibits a pronounced negative effect on soil fungal communities. Our findings also suggest that changes in plant functional groups under nutrients deposition are pivotal in shaping soil fungal community structure in semi-arid grassland and highlight the need for a better understanding of the belowground ecosystem dynamics.

Wildfire probability estimated from recent climate and fine fuels across the big sagebrush region

BackgroundWildfire is a major proximate cause of historical and ongoing losses of intact big sagebrush (Artemisia tridentata Nutt.) plant communities and declines in sagebrush obligate wildlife species. In recent decades, fire return intervals have shortened and area burned has increased in some areas, and habitat degradation is occurring where post-fire re-establishment of sagebrush is hindered by invasive annual grasses. In coming decades, the changing climate may accelerate these wildfire and invasive feedbacks, although projecting future wildfire dynamics requires a better understanding of long-term wildfire drivers across the big sagebrush region. Here, we integrated wildfire observations with climate and vegetation data to derive a statistical model for the entire big sagebrush region that represents how annual wildfire probability is influenced by climate and fine fuel characteristics.ResultsWildfire frequency varied significantly across the sagebrush region, and our statistical model represented much of that variation. Biomass of annual and perennial grasses and forbs, which we used as proxies for fine fuels, influenced wildfire probability. Wildfire probability was highest in areas with high annual forb and grass biomass, which is consistent with the well-documented phenomenon of increased wildfire following annual grass invasion. The effects of annuals on wildfire probability were strongest in places with dry summers. Wildfire probability varied with the biomass of perennial grasses and forbs and was highest at intermediate biomass levels. Climate, which varies substantially across the sagebrush region, was also predictive of wildfire probability, and predictions were highest in areas with a low proportion of precipitation received in summer, intermediate precipitation, and high temperature. ConclusionsWe developed a carefully validated model that contains relatively simple and biologically plausible relationships, with the goal of adequate performance under novel conditions so that useful projections of average annual wildfire probability can be made given general changes in conditions. Previous studies on the impacts of vegetation and climate on wildfire probability in sagebrush ecosystems have generally used more complex machine learning approaches and have usually been applicable to only portions of the sagebrush region. Therefore, our model complements existing work and forms an additional tool for understanding future wildfire and ecological dynamics across the sagebrush region.

Overcompensation of ecosystem productivity following sustained extreme drought in a semiarid grassland.

Drought events are projected to be more extreme and frequent in the future and have profound influences on the structure and functions of terrestrial ecosystems. Thus, better understanding the mechanisms of recovery is critical for predicting the future dynamics of terrestrial ecosystems. We performed a 7-year field precipitation experiment to examine recovery of a grassland ecosystem from different magnitudes of sustained drought, from slight to extreme. The ecosystem was exposed to precipitation treatments in the first 3 years (2010-2012) and recovered during the last 4 years (2013-2016) without precipitation treatments. Overall, large reductions of aboveground net primary productivity (ANPP, -43.3%) and perennial forb biomass (-83.1%) were observed in the third year (2012) of extreme drought only. Nevertheless, ANPP fully recovered within 1 year after the drought treatments were terminated, and the rapid recovery was mainly due to increased soil total nitrogen and root biomass allocation after drought. Surprisingly, large increases of ANPP under the extreme drought treatment occurred during the recovery periods from 2013 to 2015 (+74.1, +88.5, and +119.8 g m-2 year-1 ) compared to the control. The overcompensation offset the extreme drought-induced reduction of ANPP in the treatment years and was primarily ascribed to the enhanced biomass of perennial grasses (PG). Higher resistance to drought and fast resource acquisition strategy might drive the rapid recovery and expansion of PG. Our findings revealed the rapid recovery of grasslands and the critical role of community overcompensation in maintaining grassland ecosystem function and stability under future climate change scenarios.

Long-term growing season aridity and grazing seasonality effects on perennial grass biomass in a Chihuahuan Desert rangeland

Growing season aridity and livestock grazing seasonality can influence primary productivity of perennial grasses in dryland systems. For this study, we used a long-term dataset (1967–2004) to investigate the independent and joint effects of growing season aridity and season of grazing (yearlong continuous, fall, winter/spring, or summer season grazing) on the mean annual primary productivity of the perennial grasses Bouteloua eriopoda (black grama), Aristida spp. (threeawn), and Sporobolus spp. (dropseed) in a southwestern United States Chihuahuan Desert rangeland system. Over the 37-year study period, total perennial grass biomass decreased as aridity increased, but the extent of this relationship depended upon season of grazing and specific grass taxon. Aridity-related decreases in total perennial grass biomass were most severe in the summer grazing treatment. Our findings indicate that over time, summer and fall grazing can potentially exacerbate the negative effects of increasing aridity on perennial grass biomass. As arid and semi-arid rangelands globally face increasing aridity associated with a changing climate, land managers can modulate the season of grazing, dependent on dominant taxa present, to minimize these effects. Our study and those from other arid land locations indicate continuous grazing at light to conservative intensities can better sustain key perennial grasses than strategies involving concentrated seasons of grazing. However, growing season aridity levels must also be taken into consideration.

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.

Phytoremediation and high rainfall combine to improve soil and plant health in a North America Northern Great Plains saline sodic soil

Saline/sodic soils are often remediated by applying gypsum, improving drainage, and irrigating with high quality water. However, these management approaches may not be effective or feasible in dryland soils supersaturated with gypsum. A field study, conducted between 2017 and 2021, investigated the effect of phytoremediation on soil and plant health in a landscape containing productive, transition, and saline/sodic soils. Phytoremediation treatments–corn (<i>Zea mays</i>) and two perennial grass mixes (mix 1 slender wheatgrass [<i>Elymus trachycaulus</i>] and beardless wildrye [<i>Leymus triticoides</i>], and mix 2 slender wheatgrass, creeping meadow foxtail [<i>Alopecurus arundinaceus</i>], western wheatgrass [<i>Agropyron smithii</i>], and green wheatgrass [<i>Elymus Hoffmannii</i>])-were planted and compared with a no-plant control treatment across three soil zones. Perennial grasses were dormant seeded in the winter of 2017 and 2018, and corn was grown in 2018, 2019, and 2020. Soil samples (0 to 15 cm) were collected on July 24, 2018, July 23, 2019, July 24, 2020, and April 15, 2021. Across soil zones, corn production was 5,990 (grain + stover), 3,900 (stover only), and 6,150 (grain + stover) kg ha^-1 in 2018, 2019, and 2020, respectively, whereas perennial grass biomass yields averaged 1,220, 9,065, and 7,375 kg ha^-1 in 2018, 2019, and 2020, respectively. Due to high rainfall that occurred from the fall of 2018 through the summer of 2019, the depth to the water table decreased and the soil electrical conductivity (EC_1:1) (-0.83 ± 0.149 dS m^-1) and exchangeable sodium (Na⁺) (-656 ± 220) decreased in all treatments. In addition, from 2018 to 2019, the risk of soil dispersion (lower Na⁺/EC_1:1 ratio) was less in treatments with growing plants <i>(p</i> = 0.02) than plots without plants. With drier conditions from the fall of 2019 through the spring of 2021, the depth to groundwater increased, the EC_1:1 decreased in the transition soil but increased in the saline/sodic soil (<i>p</i> = 0.001), and the Na⁺/EC_1:1 ratio increased in the productive and transition soils and was static or decreased in the saline/sodic soil (<i>p</i> = 0.001). In conclusion, this and related work showed that phytoremediation when combined with high natural rainfall reduced soil EC_1:1 and the exchangeable Na⁺ in all soils; however, these benefits may be short lived, and as the water tables dropped in 2020, EC_1:1 increased in the saline/sodic zones. Laboratory and linked research from the study site also showed that fertilizing saline sodic soils can result in very high nitrous oxide (N₂O) emissions, and reseeding degraded soil to perennial plants provides soil cover that reduces the risk of erosion and provides habitat for wildlife.

BAKING QUALITY OF SPRING SOFT WHEAT AND TRITICALE DEPENDING ON THE FORECROP AND BACKGROUND OF CULTIVATION

The article presents data on the assessment of the baking quality of the varieties of spring soft wheat - Shortandinskaya 95 improved and spring triticale – Rosinka. The purpose of the work: a comparative assessment of bread quality made from spring wheat flour and spring triticale, depending on the forecrop and background of cultivation in Northern Kazakhstan. The sowing was carried out in the period 2018-2019 on the experimental areas of the “SPC GF named after A. I. Barayev” LLP. The influence of organic and traditional farming systems on the quality of the resulting products was studied. The organic farming system included the use of aboveground biomass of perennial grasses and legumes as organic fertilizer. Traditional - the use of mineral fertilizers: ammophos in a dose of P40, ammonium nitrate in a dose of N20, N40, N60 and N80. The test baking was carried out by the non-paired method with intensive kneading of the dough using dry yeast and 100 g of flour. The evaluation of the baking advantages of flour was carried out according to the method of the state variety testing with the determination of external &nbsp;and internal signs of bread quality. Based on all the indicators, the overall baking score was obtained. It was found that the baking score of triticale bread is lower than that of wheat by 1- 1.5 points. In the years of research, the dependence of the quality of bread on the predecessor and the background of cultivation was noted. The advantage for the studied crops was the organic background, the best precursor for spring triticale was melilot, for spring soft wheat – granary.

Dormant Season Grazing: Effect of Supplementation Strategies on Heifer Resource Utilization and Vegetation Use

Grazing dormant forage under low-input heifer development strategies typically exposes cattle to low-quality forage. Protein supplementation while grazing dormant range can enhance heifer growth and reproductive performance. We examined resource utilization of heifers and the effects of dormant season grazing on residual vegetation characteristics under two supplementation management strategies. Approximately 100 weaned composite heifer calves were randomly selected and placed into one of two supplementation treatments in each of 2 yr, one receiving a free access 62% crude protein self-fed concentrate and the other receiving a daily hand-fed 20% crude protein cake. Grazing occurred from December (2015 and 2016) through March (2016 and 2017). Thirty transects were randomly located within each pasture for measuring vegetation quality and structure before and after grazing. Daily space use and behavior was evaluated for 21 individuals within each treatment using global positioning system (GPS) collars and resource utilization functions. Heifers supplemented with concentrated protein spent more time grazing per day than heifers supplemented with cake (6.92 ± 0.18, 6.24 ± 0.17 h). Relative use by heifers in the cake treatment was negatively related to horizontal distance from the supplement delivery site early to midwinter (β¯ˆ = −0.41 ± 0.16, −0.53 ± 0.17). Both treatments selected grazing locations relative to standing biomass of perennial grasses (β¯ˆ = 0.0005 ± 0.00004) and crude protein (β¯ˆ = 0.12 ± 0.007). However, resource selection was highly variable among individuals for both supplementation treatments. We found no treatment effects on pre-post grazing differences in residual cover of litter, grass, forbs and shrubs (P > 0.24). However, the time period when grazing occurred had an effect on residual vegetation conditions (P < 0.01). Our results indicate high levels of variability in grazing site selection by heifers, suggesting future research should incorporate individual animal measurements in an attempt to account for individual animal variability.

НОВЫЕ ИСТОЧНИКИ ПОВЫШЕННОГО КАЧЕСТВА ЗЕЛЕНОЙ МАССЫ МНОГОЛЕТНИХ ТРАВ В УСЛОВИЯХ ЮЖНОЙ ЛЕСОСТЕПИ ЗАПАДНОЙ СИБИРИ

Background. Perennial grasses are essential in the development of field forage production in West Siberia. Very pronounced continental climate of the cropping areas in Siberia leads to increased demands on the cultivars. The objects of the study were cultivated varieties of perennial grasses (awnless bromegrass and variegated alfalfa). The aim of the work was to identify the sources of high-quality green matter in variegated alfalfa and awnless bromegrass. Materials and methods. The experimental part of the work was carried out over the period of 2011–2016 on the experimental fields of Omsk Agrarian Scientific Center, located in the southern forest steppe near Omsk. Agricultural practice was conventional for West Siberia. Analysis of variance was used in mathematical data processing; stability and plasticity parameters were calculated. Results. The content of protein and cellulose fiber in the green biomass of perennial grasses was mainly influenced by the weather conditions of the year: 84.1 and 76.5% in alfalfa, 93.9 and 91.2% in bromegrass, respectively. A reduction of cellulose fiber content in the studied crops contributed to an increase in raw protein content (r = –0.348 and –0.335) and in feed value units (r = 0.544 and 0.352 for alfalfa and bromegrass, respectively). Higher yields had a negative impact on feed value units (r = –0.402 and –0.713). Besides, the yield of awnless bromegrass demonstrated a significant negative correlation with protein content (r = –0.617) and a positive one with cellulose fiber (r = 0.744). The yield of variegated alfalfa showed a weak degree of interdependence with protein and cellulose fiber contents (r = 0.239 and 0.306).). Conclusion. High responsiveness to improved environmental conditions and high stability (bi > 1, σ2 d < 1) were observed in the alfalfa cultivars ‘Omsky 7’, ‘Elbrus’ (protein content); ‘Flora 5’ and ‘Flora 6’ (protein content, feed value units, and green matter yield), and the bromegrass cultivars ‘SibNIISKhoz 99’ (protein content, feed value units, and green matter yield) and ‘Titan’ (feed values units). During the period from 2011 through 2016, the best examples in yield and in a set of green matter quality characteristics were selected: the intensive-type alfalfa lines SP-2-99/91-267 and SP-2-99/01-282, extensive-type alfalfa line SP-2-99/01-132, and the line of bromegrass SP-2-06/08-28, which was intensive-type in protein content and feed value units, and extensive-type in cellulose fiber content and green matter yield.

Abiotic factors affect the recruitment and biomass of perennial grass and evergreen shrub seedlings in denuded areas of Patagonian Monte rangelands

Assessing the ability of key species to cope with environmental stresses in disturbed areas is an important issue for recovery of degraded arid ecosystem. Our objective was to evaluate the effect of soil moisture, exposure to UV radiation, and presence/absence of litter with different chemistry on soil N, recruitment and biomass of seedlings of perennial grass (Poa ligularis and Nassella tenuis) and evergreen shrub species (Atriplex lampa and Larrea divaricata) in denuded areas. We carried out a microcosm experiment with soil blocks (28 cm depth) sowed with seeds of the target species, subjected to different levels of litter type (perennial grass-evergreen shrub mixture, evergreen shrub mixture, and no litter), UV radiation (near ambient and reduced UV), and soil water (high: 15–25% and low 5–15%). Periodically, during 6 months, we assessed soil-N (total and inorganic) at two depths and species seedling recruitment at microcosms. Additionally, emerged seedlings of each species were transplanted to individual pots containing soil and subjected to the same previous factors during 12 months. Then, all plants were harvested and biomass assessed. Only inorganic soil-N at the upper soil varied among treatments increasing with the presence of evergreen shrub litter, exposure to ambient UV, and high soil water. Inorganic soil-N, promoted by near ambient UV and high soil water, had a positive effect on recruitment of perennial grasses and A. lampa. Both litter types promoted the recruitment of perennial grasses. Evergreen shrub litter and high soil water promoted the recruitment of L. divaricata. Seedling biomass of perennial grasses increased with high soil water and reduced UV. Ambient UV had positive or null effects on biomass of evergreen shrub seedlings. High soil water increased biomass of L. divaricata seedlings. We concluded that soil water appeared as the most limiting factor for seedling recruitment of all species whereas inorganic soil N limited the recruitment of the small-seeded perennial grasses and A. lampa. Ambient UV had negative effects on seedling biomass of perennial grasses. These complex relationships among abiotic factors and seed and plant traits should be taken into account when planning management actions after disturbances.

Root and soil total carbon and nitrogen under bioenergy perennial grasses with various nitrogen rates

As aboveground biomass of perennial grasses is harvested for feedstock or bioenergy production, root biomass C and N become primary C and N inputs for enhancing soil C and N sequestration. Information is scanty about root biomass C and N and subsequent soil C and N stocks under bioenergy perennial grasses applied with various N fertilization rates in semiarid regions. We evaluated the effect of perennial grass species and N rates on root biomass C and N and soil total C (STC) and total N (STN) stocks at the 0–120 cm depth from 2011 to 2013, 2–4 yr after grass establishment, in the northern Great Plains, USA. Perennial grasses were intermediate wheatgrass (Thinopyrum intermedium [Host] Barkworth and Dewey), smooth bromegrass (Bromus inermis L.), and switchgrass (Panicum virgatum L.), and N fertilization rates were 0, 28, 56, and 84 kg N ha−1. Root biomass C and N at 0–15 and 0–120 cm were greater with intermediate wheatgrass and switchgrass than smooth bromegrass in 2011, but the trend reversed for root biomass C at 0–15 cm in 2012. Root biomass C at both depths among N rates and years. The STC at 0–15, 30–60, and 0–120 cm also varied among grass species and years. At 30–60 cm, STC increased with increased N rates under intermediate wheatgrass and switchgrass, but decreased under smooth bromegrass. At 60–90 cm, the trend for STC reversed. The STN at 15–30 cm was greater under intermediate wheatgrass than smooth bromegrass and switchgrass and at most depths was greater in 2012 than 2013. Overall root biomass C and N at 0–120 cm were 12–16 times greater and STC and STN 8–9% greater under perennial grasses than adjacent annual spring wheat. Although intermediate wheatgrass returned more root C and N to the soil than other grasses, both STC and STN varied among grass species and N rates. Increased root C and N inputs, however, increased STC and STN under perennial grasses compared with annual spring wheat.

Trajectories of floristic change in grassland: landscape, land use legacy and seasonal conditions overshadow restoration actions

AbstractQuestionsHow does ground‐layer plant composition respond to the imposition of woodland habitat restoration treatments following the removal of long‐term pastoral management? Do different vegetation types have different trajectories of change?LocationA long‐term ecological research site comprising temperate eucalypt grassy woodland and forest in south‐eastern Australia, converted from pastoral use to conservation management. This has involved the implementation of habitat restoration treatments in addition to the cessation of livestock grazing and fertilizer inputs.MethodsWe surveyed ground‐layer floristic composition over a 4‐yr interval, in 96 1‐ha sites that had been subjected to combinations of restoration treatments aimed at improving the condition of the woodland habitat for fauna: (1) Reduced kangaroo grazing intensity; (2) Addition of coarse woody debris; and (3) Burning. We used nonmetric multidimensional scaling (NMDS) to plot the sites, and to analyse the average trajectories of floristic change for each of six initially identified vegetation types, and the restoration treatments. We partitioned Bray–Curtis dissimilarity measures to rank individual species’ contributions to floristic change in each vegetation type between 2007 and 2011.ResultsThe identities of the six vegetation types identified at time zero was strongly retained over the 4‐yr observation period. There was generally a uniform change across the vegetation types, which was the result of increases in biomass of the characteristic dominant perennial grasses, and increases in some native forbs. The two vegetation types with evidence of past fertilization showed some convergence with native vegetation types due to the decrease in some exotic species. The restoration treatments had no significant influence on species composition.ConclusionsThe native herbaceous vegetation in the woodland was largely resistant to compositional change, although seasonal conditions increased the biomass of the perennial grasses defining the different vegetation types. However, sites with an evident history of past fertilization and notable amounts of exotic pasture species changed slightly but significantly, with some pasture species declining and floristic convergence with native vegetation over 4 yr. These rates of change need to be considered in the application of vegetation offsetting policy.

Seed Bank Depletion: The Key to Long-Term Downy Brome (Bromus tectorum L.) Management

Invasive winter annual grasses such as downy brome (Bromus tectorum L.) are a threat to native ecosystems throughout the United States. Downy brome is able to exploit moisture and nutrients throughout the fall and early spring before native plants break dormancy. This results in decreased native species abundance and development of monotypic downy brome stands. Short-term downy brome management has been shown to be effective; however, the soil seed reserve has often been overlooked, although it’s the mechanism responsible for rapid reestablishment. This field study was conducted at two sites in Colorado to evaluate the longevity of the downy brome soil seed reserve and its implications on long-term downy brome control. Glyphosate plus adjuvant applications were made for 0, 1, 2, 3, 4, or 5 consecutive years. Downy brome and perennial grass biomass harvests were conducted yearly to determine changes in species composition. In addition, soil cores were collected to evaluate the yearly variation and depletion of the downy brome soil seed bank in response to consecutive glyphosate applications. We found that 1−3 yr of consecutive glyphosate treatments were insufficient to deplete the downy brome soil seed bank. Downy brome biomass and the soil seed bank recovered within 1−2 yr after glyphosate treatments were terminated; however, 4 and 5 consecutive yr of glyphosate applications were sufficient to control downy brome through depletion of the soil seed bank. Managing downy brome for 4−5 consecutive yr resulted in a 4- to 9-fold increase in perennial grass biomass. These data suggest that long-term management of downy brome is dependent on eliminating the soil seed bank using a multiyear approach.

Understory Responses to Mechanical Treatment of Pinyon-Juniper in Northwestern Colorado

Pinyon-juniper (Pinus spp.–Juniperus spp.) encroachment and declining mule 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.

Effect of surface roughness and mulch on semi-arid revegetation success, soil chemistry and soil movement

For the successful reclamation of disturbed land, the reduction of initial erosion risk must be balanced with later vegetation establishment. A combination of erosion control and revegetation practices was researched using commercial (full-sized) equipment on a semi-desert grassland site in southern Arizona, USA. Two soils with different parent materials were used to add a 30cm cap on sites at two elevations: 1646 and 1403masl. There were two surface roughness treatments: smooth and rough. Three straw mulch treatments were applied: no mulch, mulch incorporated into the surface soil, and mulch tackified onto the surface. Plots were planted with a 10-species native mix dominated by perennial grasses. After two growing seasons, the incorporated mulch treatment resulted in significantly more seeded grass aboveground biomass than the no mulch treatment while the no mulch treatment had more forb and volunteer biomass than the surface mulch treatment. There was significantly higher erosion on the rough surface treatment compared to the smooth surface. Increasing perennial grass biomass was correlated with reduced erosion while forb and volunteer biomass showed no relationship with erosion. The smooth surface with surface mulch best established perennial grasses, minimized weeds, and reduced erosion. This combination of practices both minimized erosion as well as maximized vegetation establishment.

Functional Responses of Woody Prosopis caldenia Seedlings to Drought and Livestock Grazing in Semiarid Rangelands of Argentina

In the semiarid rangelands of Central Argentina overgrazing and drought alter the competitive balance between woody and herbaceous vegetation, favoring an increase in Prosopis caldenia. The objective of this study was to evaluate the effect of competition in perennial grasses and water stress on the relative growth rate (RGR) and related functional attributes of P. caldenia seedlings in sites with different grazing histories: a site exposed to long term (40 or more years) continuous grazing by cattle (grazed experimental site), and a long-term (around 30 years) exclosure (ungrazed experimental site). The total average RGR of the seedlings that grew in the grazed site was significantly higher, whereas the additional water supply favored those seedlings that grew in the ungrazed site. Significant relationships existed between the RGR and all the attributes measured, except in the ungrazed site where only those attributes related to leaf traits were correlated with the RGR. The above- and below-ground biomass of perennial grasses negatively affected the RGR of the P. caldenia seedlings in both experimental sites and soil moisture favored the RGR of the seedlings in the ungrazed site. Our work reveals the ability of seedlings of P. caldenia to take advantage of changes in environmental conditions, such as the release of resources due to overgrazing and to increase its RGR, which ensures its establishment.

Response of the annual biomass production of a typical steppe plant community to precipitation fluctuations

Understanding the relationship between the aboveground net primary production (ANPP) and annual precipitation in arid and semiarid grasslands is crucial for assessing the effects of climate change on grassland ecosystems. The temporal pattern of ANPP, based on long-term data on a semiarid ecosystem in Inner Mongolia, was investigated. The biomass of perennial grasses, perennial forbs and Stipa grandis P. Smirn., showed a positive relationship with annual precipitation. The amount of annual precipitation also changed the annual biomass of 13 other dominant species and consequently the ANPP. The coefficient of variation of the ANPP of the plant community was lower than the coefficient of variation of annual precipitation. Irrespective of the strong inter-annual variation in annual precipitation, the positive relationship found between ANPP and annual precipitation suggests the dependence of ANPP upon hydrological variations in typical steppe. Our findings highlight the importance of dominant perennial species and functional groups in mediating the responses of ANPP to annual precipitation in the typical steppe in northern China.

Grazing Exclusion Effect on Soil and Vegetation Properties in Imam Kandi Rangelands, Iran

Most of the rangeland of Urmia in Iran is degraded and will require considerable reclamation to achieve a desirable state. The aim of this study was to evaluate the effects of 14 years of grazing exclusion on vegetation and soil properties in Imam Kandi rangelands. Sampling in both grazing exclosure and grazed areas were conducted using a systematic randomized sampling method. Six 100-m long transects were randomly located in each area and ten 1 × 1 m sampling plots were located along each transect. Within each plot, species presence, canopy cover, species yield, and plant densities were measured. Soil cores were taken in the center of each vegetation sampling plot at 0–30 cm and 30–60 cm depths. Organic matter, nitrogen content, the amounts of phosphorus and potassium, electrical conductivity (ECe), pH, the percentage of CaCO3, and soil texture were determined for each sample. Results indicate differences in plant canopy cover, species composition, and yield between the grazing exclosure and the control site. All plant growth forms at the exclusion site differed from those at the grazed site. Biomass of perennial grasses, perennial forbs and annual forbs was greater at the exclusion site than at the grazed site, and biomass of annual grasses and shrubs at the control site was greater than at the exclusion site. Overall grazing exclosure site improved the vegetation composition and soil quality parameters ECe, pH, organic matter, nitrogen, phosphorus, and potassium content relative to the grazed site.

The Effect of Heavy Metal Contaminated Soil on Growth and Development of Perennial Grasses

Contamination of agricultural land in Poland by heavy metals is not a general problem but is limited to industrial areas. In regions of long history of industrial emission, of elevated levels of lead, cadmium, zinc and other ions during coal and ore mining and processing, as for example in Silesia, about 10 % of agricultural land may be characterized by exceeded maximum residue limits for Cd, Pb, Cu, Ni and Zn ions. Since the maintenance of agricultural areas in those regions is important from an ecological standpoint, the alternative farming activities are needed. Perennial grass biomass production for energy purposes is currently the best solution for majority of agricultural areas not suitable for food production in Poland. Along with increasing knowledge on separation and utilization of heavy metals (HM) during and after biomass processing, phytoremediation of polluted soils will become important and valuable. To detect the effect of soil HM ions concentration on growth and development of selected, tall growing and high biomass yielding perennial grass cultivars, the chlorophyll fluorescence parameters were registered. The elevated content of Pb, Cd and Zn ions in soil influenced on decrease of: minimal (Fo), maximal (Fm) and variable (Fv) fluorescence level as well as on total complementary area on a diagram of chlorophyll a fluorescence induction curve (Area). Based on detected parameters it was concluded, that the high level of HM ions in soils negatively affected the efficiency of photosynthesis. Therefore, plant growth, as well as development of generative shoots and finally the biomass yield were reduced in some cultivars. Among tested cultivars different reaction for HM ions in polluted soil were noted: from only slightly modified parameters of photosynthesis and unreduced yield (Elytrigia elongata cv. Bamar and Arrhenatherum elatius cv. Wiwena) to significantly reduced Fo, Fv, Fm and biomass yield (Bromus carinathus cv. Broma and Bromus inermis cv. Brudzynska).

Changes in plant functional groups and species diversity under three grassland using modes in typical grassland area of Inner Mongolia, China

Aims Our objectives were to reveal changes in plant functional groups and species diversity under three grass-land using modes in typical steppe of Inner Mongolia, China. Methods Three plots in similar habitats were selected from the Hulunbeier steppe area of the Hui River National Nature Reserve: an meadow plot (controlled utilization), pasture plot (moderate utilization) and public pasture plot (severe utilization). Plots were 250 m × 250 m and consisted of three sample belts separated by 20 m. Each sample belt had eight 1 m × 1 m sample plots. Important findings There were differences in species composition and community characteristics of the func-tional groups. Shrubs and sub-shrubs combined were significantly different (p 0.05) among the plots, with the highest value in meadow. Perennial grasses were significantly different (p 0.05). Annual and biennial herbs combined had significant differences (p 0.05), with the highest value in the public pasture. The public pasture also had the highest percentage of the xerophyte functional group (50%) and the lowest mesoxerophyte and meso-phyte (19%), and differences were significant (p 0.05) among the plots. The biomass of shrubs and sub-shrubs were lower in all plots. The combined biomass of perennial grasses and forbs decreased with the increase in grassland use intensity among meadow, pasture and public pasture, while the combined biomass of annual and biennial herbs increased. With the increase in use intensity, the community structure and composition tended to become simplified and susceptible to change. Richness and diversity were lowest in the pasture and highest in meadow. Differences in evenness were not significant. The use of meadow contributed to improving the health of the grassland, but pasture and public pasture exhibited over-grazing phenomena. The public pasture had degraded significantly because of the uncertainty about property responsibility and ineffective management.