Perennial Grass Density Research Articles

Spatial distribution of shrubs and perennial plants under grazing disturbance in the desert steppe of Inner Mongolia

The desert steppe is unique as a transition zone from the steppe to the desert of the Eurasian Steppe. The spatial distribution of shrubs and perennial plants has changed due to long-term disturbance caused by overgrazing in the ecosystem. This study aimed to determine the degree of patchiness of shrubs and perennial plants under grazing disturbance, which is of great significance to better understand the succession mechanism of plant community in the desert steppe. This study investigated the spatial distribution of shrubs and perennial plants under four stocking rates (no grazing, CK, 0 sheep·hm−2·half year−1; light grazing, LG, 0.93 sheep·hm−2·half year−1; moderate grazing, MG, 1.82 sheep·hm−2·half year−1; heavy grazing, HG, 2.71 sheep·hm−2·half year−1) in the desert steppe of Inner Mongolia, primarily using geostatistical methods. The density of perennial grasses increased with increasing stocking rate, while its height decreased (except for HG). The density and height of the shrubs and the perennial forbs showed an exponential or gradual decline. The spatial distribution of shrubs and perennial plants is mainly affected by structural factors such as topography, soil parent material, and climate, and the density of shrubs and perennial plants is most sensitive to changes in stocking rate. An appropriate stocking rate increases the spatial heterogeneity of shrubs and perennial plants, but heavy grazing reduces the spatial heterogeneity of shrubs and perennial plants.

Effects of different grassland utilization methods on the germinable soil seed bank of the Hulunbuir meadow steppe.

Seed banks are crucial regenerative resources for aboveground vegetation. The pattern of their changes holds immense significance in understanding alterations in the belowground seed bank. This understanding is pivotal for uncovering both short-term and long-term shifts in plant communities. Additionally, it contributes to the restoration of grassland ecosystems. To better protect grassland biodiversity and provide a theoretical basis for the restoration of degraded grasslands, in this study, the germination characteristics of soil seed banks in free-grazed, enclosed and mown areas were compared, and the results were combined with those of previous studies for a comprehensive analysis. The density of soil seed bank and perennial forage soil seed bank were significantly affected by different grassland utilization and soil depths. Grazing and enclosure grassland utilization methods increased the content of the soil seed bank, and mowing reduced the content of the seed bank. The soil seed bank density of perennial grasses accounted for the highest proportion under grazing, followed by mowing, and its lowest proportion was observed in the enclosures. Grazing not only facilitated the germination of the perennial grass seed bank but also substantially augmented its content. Mowing inhibited the germination of the upper growth grasses seed bank, which was particularly significant in the 0-2cm soil layer under grazing. The content of the upper growth grasses seed bank affected the total seed bank to a certain extent, mainly in the 5-10cm layer. The general correlations among the perennial grasses, upper growth grasses and soil germination seed bank resulted in 84.58% information extraction, and this information has practical significance for grassland ecological restoration.

Both fencing duration and shrub cover facilitate the restoration of shrub-encroached grasslands

Fully understanding community assembly mechanisms is crucial to better predict grassland community dynamic under restoration. The community assembly over time is more complicated in shrub-encroached than in non-encroached degraded grasslands because the presence and size of shrub could regulate community processes and diminish effects of restoration time. However, how shrub size influences community assembly under restoration in shrub-encroached communities remains poorly understood. Therefore, in Caragana microphylla shrub-encroached grasslands in the Inner Mongolia typical steppe region, three plots with different shrub cover (low, medium and high) were set up in each of three sites with different fencing duration (15-, 35- and 39-year fencing). We assessed the assembly mechanisms of shrub-interspace herbaceous communities by estimating standardized effect size (SES) of functional dispersion (FDis) based on the first two principal components (PC1 and PC2) of traits characterizing resource acquisition strategies. According to the SES of FDisPC1, the assembly mechanisms shifted from stochastic processes to competitive exclusion over time of fencing in the plots of low and medium shrub cover and across a shrub cover gradient in the sites of 15-year and 35-year fencing, with the increase of soil moisture, species richness, Shannon-Wiener diversity and relative density of perennial grasses. Competitive exclusion dominated the communities in the site of 39-year fencing and in the plots of high shrub cover. According to the SES of FDisPC2, the competitive exclusion dominated all of the 9 communities investigated in this study. By variance component analysis, shrub cover showed the highest contribution in explaining the variance in community-weighted mean (CWM), and shrub cover and fencing duration showed the first two highest contributions in explaining the variance in SES of FDis. The present findings highlight the significance of shrub cover in influencing the community assembly in shrub-encroached grasslands under restoration in the European-Asian typical steppe region.

Influence of presowing seed treatment on the yield of variegated alfalfa and eastern galega

The article deals with the insufficiently studied problem of variegated alfalfa and eastern galega presowing seed treatment, which can serve as an excellent reserve for increasing their forage productivity. The quality of the seeds determines the stand density of perennial grasses and their yield. The studies have been performed on sod-podzolic medium loamy soil. The authors studied the effect of molybdenum-acid ammonium (300 gm/t), Rhizotorphine bacterial preparation (for variegated alfalfa – 0.5 l/t, for eastern galega – 1.0 l/t), HB-101 plant growth regulator (1 ml/t), and Agree's Forsage complex fertilizer (1.2 l/t) upon cultivating the studied crops. The consumption rate of the working solution (water + preparation) was 10 litres per ton of seeds. The accounting plot area was 33 m2. Perennial legumes were sown after spring rapeseed; the seeding rate for variegated alfalfa was 14 kg/ha, for eastern galega – 26 kg/ha. It has been found that introducing seed treatment with the Agree's Forsage complex fertilizer increases productivity by 23–47% due to increasing the field germination of variegated alfalfa by 10–15% and eastern galega by 4–10%, and due to increasing the number of nodule bacteria by 6–13 per plant and 8–16 per plant respectively.

Native perennial and non-native annual grasses shape pathogen community composition and disease severity in a California grassland.

The densities of highly competent plant hosts (i.e. those that are susceptible to and successfully transmit a pathogen) may shape pathogen community composition and disease severity, altering disease risk and impacts. Life history and evolutionary history can influence host competence; longer lived species tend to be better defended than shorter lived species and pathogens adapt to infect species with which they have longer evolutionary histories. It is unclear, however, how the densities of species that differ in competence due to life and evolutionary histories affect plant pathogen community composition and disease severity.We examined foliar fungal pathogens of two host groups in a California grassland: native perennial and non-native annual grasses. We first characterized pathogen community composition and disease severity of the two host groups to approximate differences in competence. We then used observational and manipulated gradients of native perennial and non-native annual grass densities to assess the effects of each host group on pathogen community composition and disease severity in 1-m2 plots.Native perennial and non-native annual grasses hosted distinct pathogen communities but shared generalist pathogens. Native perennial grasses experienced 26% higher disease severity than non-native annuals. Only the observational gradient of native perennial grass density affected disease severity; there were no other significant relationships between host group density and either disease severity or pathogen community composition.Synthesis. The life and evolutionary histories of grasses likely influence their competence for different pathogen species, exemplified by distinct pathogen communities and differences in disease severity. However, there was limited evidence that the density of either host group affected pathogen community composition or disease severity. Therefore, competence for different pathogens likely shapes pathogen community composition and disease severity but may not interact with host density to alter disease risk and impacts at small scales.

Grazing and aridity have contrasting effects on the functional and taxonomic diversity of ants

Ants are one of the most abundant and ubiquitous organisms on Earth and play critical roles in multiple ecosystem services such as seed dispersal and nutrient cycling. Despite this, the effects of climatic and land use stressors on particular species or groups of ants are poorly known. We conducted a regional field survey across 108 locations in south-eastern Australia, using correlation network analysis and structural equation modelling to identify how ants respond to environmental stressors. We found contrasting relationships amongst ants, and aridity, and vertebrate grazing intensity and history. Increasing aridity was associated with reduced ant richness, whereas increasing grazing intensity was associated with greater ant richness directly, and indirectly, via reductions in litter depth and perennial grass density. However, these taxonomically diverse groups of ant species still shared contrasting responses to increasing aridity and grazing intensity. We found strong associations between grazing, aridity and the abundance of Seed Harvesters, weak indirect relationships with Generalist Foragers, but no relationships for Predators or Sugar Feeders. Taken together, our work identifies contrasting relationships amongst grazing, aridity and ants (ant ‘winners’ or ‘losers’) across contrasting ecological contexts. Given that increasing aridity is generally associated with lower grazing intensity, our results suggest that locations with more arid sites will have lower ant richness with fewer Seed Harvesters, whereas more mesic sites with high grazing intensity might increase ant richness, and the abundance of specific ant species. Such knowledge is important if we are to maintain critical ant-mediated functions as Earth becomes drier and grazing intensity increases.

Characteristics of growth and development of perennial grasses on the basis of meadow tetraploid clover

Perennial grasses are less dependent on weather and soil conditions than other crops due to their plasticity, low demand for growing conditions, and a large variety of species. In 2013-2017 in the conditions of the Udmurt Republic the biological properties of meadow tetraploid clover (Trifolium pratense L.), alfalfa changeable (Medicago x varia Martyn), birds-foot trefoil (Lotus corniculatus L.), eastern galega (Galéga orientális Lam.) and timothy grass (Phleum pratense L.) in double and triple agrocenoses were studied according to the age of the grass stand and the term of mowing. Plant density of perennial grasses in agrocenoses depended on the biological characteristics of the species, the age of grass stand and the term of mowing. In the first year of use of agrophytocenoses the density of stalk stand was at the level of 374-542 pcs /m2, in the second year of use it was a little higher (348-688 pcs /m2), in the third year of use – 240-594 pcs /m2. High density of meadow tetraploid clover in the grass stand was noted in the second year of use – 266-520 pcs/m2. The number of timothy grass stems (122-194 pcs/m2) in the grass mixture was high even in the first year of grass stand use, in the following years there was a further increase of this indicator to 196-412 pcs/m2. By the third year of use there was an increase in the number of stems of alfalfa changeable to 86-148 pcs/m2 and birds-foot trefoil – up to 108-200 pcs/m2. The plant density of the eastern galega in agrocenoses was low. The agrometeorological conditions of the year and the term of mowing affected the height and leafiness of perennial grass plants in agrocenoses. The leafiness of meadow tetraploid clover reached 64%, of the eastern galega – 74%. Timothy grass plants were less leafy – 23-38%. The height of meadow clover plants was at the level of 51 cm, of timothy grass – 75-78 cm. Birds-foot trefoil was the shortest component of grass mixtures. High yield of dry mass of single-species sowing of meadow tetraploid clover was obtained in the first two years of use – 7.8 and 6.5 t/ha, respectively. By the third year of use, the productivity of clover decreased to 2.9 t/ha. The highest yields for the years of research were formed by the following agrocenoses: clover + alfalfa, clover + timothy, and clover + alfalfa + timothy – 5.9-6.3 t/ha.

Propagule pressure and priority seeding effects on the demography of invasive annual and native perennial grass species

ABSTRACTBackground: Annual grass invasion and dominance creates a self-sustaining cycle that promotes wildfires and reduces forage abundance. Restoring native plant species to annual grass-invaded ecosystems is fundamental to fostering self-sustaining native plant communities.Aims: We sought to clarify varying restoration strategies on invasive annual and native perennial grass assembly, including strategically modified seeding times, seeding rates, and added water.Methods: We tested the effects of seeding perennial grasses in autumn, spring, or seeding half in autumn and the remaining half in spring, adding water, and varying annual and perennial grass seeding rates on annual and perennial grass life history.Results: While varying perennial grass seeding times did not affect perennial grass germination rates, annual grass germination rates were highest when perennial grasses were seeded in autumn. Seeding perennial grasses in spring produced the highest adult perennial grass density in the first-growing season, but adult perennial grass density in the second-growing season was greatest when seeding occurred in autumn. Second-growing season perennial grass density was highest where annual grass seeding rates were lowest and perennial grass seeding rates were highest. Adding water in the first-growing season produced almost two-times more second-year adult perennial grasses compared to where water was not added.Conclusions: High water availability during the seeding year appears to be the most important factor for retaining perennial grasses in annual grass-invaded ecosystems.

Role of Dispersal Timing and Frequency in Annual Grass—Invaded Great Basin Ecosystems: How Modifying Seeding Strategies Increases Restoration Success

Abstract. Seed dispersal dynamics strongly affect plant community assembly in restored annual grass—infested ecosystems. Modifying perennial grass seeding rates and frequency may increase perennial grass establishment, yet these impacts have not yet been quantified. To assess these effects, we established a field experiment consisting of 288 plots (1 m2) in an eastern Oregon annual grass—dominated shrubsteppe ecosystem. In this study, the amount, timing, and frequency of perennial grass seeding events, soil moisture availability, and annual grass seed bank density were manipulated. We found that more frequent perennial grass seeding events combined with high perennial grass seeding rates produced the highest perennial grass density and biomass 2 years following seeding. However, we also found that if annual grass seed density was 1500 seeds · m-2 or higher, perennial grass density and biomass decreased, regardless of seeding strategy. Because of this finding, it appears that a threshold is crossed between...

Production and persistence of subtropical grasses in environments with Mediterranean climates

The agricultural region of south-west Western Australia (WA) has a Mediterranean climate, characterised by a winter-dominant rainfall pattern. Perennial subtropical grasses are increasingly being grown to increase productivity and reduce erosion on infertile sandy soils in the northern agricultural region (NAR) of WA, an area with mild winters and dry, hot summers. However, little information exists on the persistence of different species or their expected seasonal production and feed quality. On the south coast of WA, an area with dry, warm summers and a maritime influence, kikuyu (Pennisetum clandestinum) has been widely sown, but there is little information on the potential of other subtropical grasses. To address these issues, five trials were established across the agricultural area of south-west WA to measure the seasonal production, feed quality and persistence of the main, commercially available subtropical grasses over 3–4 years. This study demonstrates that subtropical grasses have a long-term role in the NAR in areas with mild winters and/or where the rainfall is >400 mm. The best performing subtropical grasses across a range of sites were panic grass (Megathyrsus maximus) and Rhodes grass (Chloris gayana). These species can be expected to have a water-use efficiency of ~10 kg ha–1 mm–1 over a 12-month period, provided there is a good perennial grass density. On the south coast, panic grass, Rhodes grass and setaria (Setaria sphacelata) persisted well and produced significantly more biomass than kikuyu. These grasses could complement kikuyu by increasing out-of-season production. At Kojonup, a more inland site, most of the subtropical grasses died over winter from a combination of occasional frosts and cold, wet soils. However, kikuyu re-grew from rhizomes in spring and maintained >90% ground cover 4 years after sowing. The results from these experiments are likely to be applicable to other regions across the globe with Mediterranean climates and similar soil types.

Are Early Summer Wildfires an Opportunity to Revegetate Exotic Annual Grass–Invaded Plant Communities?

Medusahead (Taeniatherum caput-medusae [L.] Nevski) is an exotic annual grass invading western rangelands. Successful revegetation of invaded-plant communities can be prohibitively expensive because it often requires iterative applications of integrated control and revegetation treatments. Prescribed burning has been used to control medusahead and prepare seedbeds for revegetation, but burning has been constrained by liability concerns and has produced widely varying results. Capitalizing on naturally occurring wildfires could reduce revegetation costs and alleviate liability concerns. Thus, our objective was to determine if early summer wildfires and fall drill seeding could be used as a treatment combination to decrease medusahead and increase perennial and native vegetation. Treatments were evaluated pretreatment and for 3yr postfire at six sites and included 1) an early summer wildfire combined with a seeding treatment (burn and seed) and 2) a nontreated (no burn, no seed) control. Perennial grass density was 4.6- to 10.0-fold greater in the burn-and-seed treatment compared to the control in the first 3yr posttreatment (P < 0.05). Exotic annual grass density and cover in the third year posttreatment were lower in the burn-and-seed treatment than in the control (P < 0.05). However, exotic annual grass density was still > 130 individuals · m‒2 in the burn-and-seed treatment. The density of exotic annual grass is of concern because over time medusahead may displace perennial grasses and annual forbs that increased with the burn-and-seed treatment. Though not directly tested in this study, we suggest that, based on other research, the burn-and-seed treatment may need to incorporate a preemergent herbicide application to further suppress medusahead and increase the establishment of seeded vegetation. However, it appears that early summer wildfires may provide an opportunity to reduce the cost of integrated programs to revegetate medusahead-invaded plant communities.

Impact of deferred grazing and fertilizer on plant population density, ground cover and soil moisture of native pastures in steep hill country of southern Australia

AbstractThe impact of deferred grazing (no defoliation of pastures for a period generally from spring to autumn) and fertilizer application on plant population density, ground cover and soil moisture in a hill pasture (annual grass dominated, with Australian native grasses being the major perennial species) were studied in a large‐scale field experiment from 2002 to 2006 in southern Australia. Three deferred grazing strategies were used: short‐term deferred grazing (no defoliation between October and January each year), long‐term deferred grazing (no defoliation from October to the autumn break, that is the first significant rainfall event of the winter growing season) and optimized deferred grazing (withholding time from grazing depends on morphological development of the plants). These treatments were applied with two fertilizer levels (nil fertilizer and 50 kg P ha−1 plus lime) and two additional treatments [continuous grazing (control) and no grazing for year 1]. Deferred grazing increased (P &lt; 0·05) perennial grass tiller density compared with the control. On average, the tiller density of the three deferred grazing treatments was 27–88% higher than the control. There was a negative (P &lt; 0·01) relationship between perennial and annual grass tiller density. Fertilizer application increased (P &lt; 0·05) legume plant density. The densities of annual grasses, legumes, onion grass (Romulea rosea) and broadleaf weeds varied between years, but perennial grass density and moss cover did not. The ground cover of the deferred grazing treatments in autumn was on average 27% higher than the control. Soil moisture differed between treatments at 15–30 cm depth, but not at 0–15 depth over autumn and winter. The results imply that deferred grazing can be an effective tool for rejuvenating degraded native pastures through increases in native grass tiller density and population and through improving farm productivity and sustainability.

Herbaceous Succession After Burning of Cut Western Juniper Trees

The expansion of western juniper (Juniperus occidentals spp. occidentalis Hook.) in the northern Great Basin has resulted in the wide-scale conversion of sagebrush-steppe communities to juniper woodlands. Prescribed fire and mechanical cutting are the 2 main methods used to remove juniper and restore sagebrush steppe. Mechanical treatments commonly leave cut juniper on site. Disadvantages of leaving cut juniper are the increased fuel hazard and the potential for increased establishment and growth of invasive species. This study evaluated the response of herbaceous plants to winter burning of cut western juniper. Vegetation response was compared among 2 burning treatments (burning trees the first winter after cutting and burning the second winter after cutting), a control (cut-unburned juniper), and the interspace between cut trees. To minimize fire impacts to herbaceous perennials, cut trees were burned in the winter when soils and ground litter were frozen and/or soils were at field capacity. Only felled trees were burned, as fire did not carry into interspaces or litter mats around western juniper stumps. We hypothesized that winter season burning would increase herbaceous perennials and would reduce cheatgrass establishment when compared to the cut-unburned control. After 10 years, total herbaceous and perennial grass cover was 1.5- to 2-fold greater, respectively, in burned treatments compared to cut-unburned controls. Perennial grass density was 60% greater in the burned treatments than in the cut-unburned treatment and the interspace. Cheatgrass cover was twice as great in the control than in the 2 burn treatments and the interspace. We concluded that burning cut western juniper when soils were wet and frozen in winter enhanced community recovery of native perennials compared to leaving cut juniper unburned.

Native Perennial Grasses in Highway Medians: Pre- and Postplant Techniques for Establishment in a Mediterranean Climate

AbstractWithin highway rights-of-way, native perennial grasses provide desirable services to support natural and human constructed ecosystems. However, native perennial grass establishment in annual grass dominated roadsides of semiarid and Mediterranean climates of the western United States requires specific cultural and chemical management treatments to control weeds. In 2004, field studies were conducted in Sacramento Valley, California to determine the effect of herbicide, disc cultivation, and species selection on native perennial grass establishment and annual weed persistence. Perennial grass species mixes common to drier and wetter upland areas in northern California were drill seeded at two sites (I-5 North and I-5 South) that had been burned in 2003 and received weed control (i.e., herbicide, cultivation, mowing) in spring 2004. Herbicides were the most important treatments for native perennial grass establishment and weed reduction. Native perennial grass species persistence was largely unaffected by cultivation or native plant accessions at these sites. Native perennial grass density increased at I-5 North in the second year of growth (2006) resulting in a plant density totaled across all herbicide regimes of 3.9 plants m−1 compared to 2.5 plants m−1 at I-5 South. Vigorous native perennial grass growth in the more fertile and less droughty soils of I-5 North helped to limit annual weeds through competition, which is anticipated to reduce the need for chemical and mechanical control in years following early establishment.

Medusahead Dispersal and Establishment in Sagebrush Steppe Plant Communities

Medusahead (Taeniatherum caput-medusae [L.] Nevski) is an invasive annual grass that reduces biodiversity and production of rangelands. To prevent medusahead invasion land managers need to know more about its invasion process. Specifically, they must know about 1) the timing and spatial extent of medusahead seed dispersal and 2) the establishment rates and interactions with plant communities being invaded. The timing and distance medusahead seeds dispersed from invasion fronts were measured using seed traps along 23 35-m transects. Medusahead establishment was evaluated by introducing medusahead at 1, 10, 100, 1 000, and 10 000 seeds · m−2 at 12 sites. Most medusahead seeds dispersed less than 0.5 m from the invasion front (P < 0.01) and none were captured beyond 2 m. Medusahead seeds dispersed from the parent plants from early July to the end of October. More seeds were trapped in August than in the other months (P < 0.01). Medusahead establishment increased with higher seed introduction rates (P < 0.01). Medusahead density was negatively correlated to tall tussock perennial grass density and positively correlated to annual grass density of the preexisting plant communities (P = 0.02). Medusahead cover was also negatively correlated with tall tussock perennial grass density (P = 0.03). The results suggest that containment barriers around medusahead infestations would only have to be a few meters wide to be effective. This study also suggests that promoting or maintaining tall tussock perennial grass in areas at risk of invasion can reduce the establishment success of medusahead. Tall tussock perennial grass and annual grass density, in combination with soil data, may be useful in predicting susceptibility to medusahead invasion. “Medusahead” (Taeniatherum caput-medusae [L.] Nevski) es un zacate anual invasor que reduce la biodiversidad y productividad del pastizal. Para prevenir la invasión de esta especie, los manejadores del pastizal deben saber más acerca de su proceso de invasión, específicamente: 1) la época y distancia de dispersión de la semilla del “Medusahead” y 2) las tasas de establecimiento y las interacciones con las comunidades vegetales que esta invadiendo. La época y la distancia a partir de los frentes de invasión, a la que las semillas de “Medusahead” son dispersadas se midieron usando trampas a lo largo de 23 transectos de 35 m. El establecimiento de “Medusahead” se evaluó introduciendo 1, 10, 100, 1 000, y 10 000 semillas · m−2 en 12 sitios. La mayoría de las semillas de “Medusahead” se dispersaron a menos de 0.5 m del frente de invasión (P < 0.01) y ninguna fue capturada más allá de 2 m. Las semillas de “Medusahead” fueron dispersadas de las plantas madre de inicios de julio a fines de octubre, se capturaron más semillas en agosto que en los otros meses (P < 0.01). El establecimiento de “Medusahead” se incrementó al aumentar el número de semillas introducidas (P < 0.01). La densidad de “Medusahead” se correlacionó negativamente con la densidad de zacates amacollados perennes y positivamente con la densidad de zacates anuales de las comunidades vegetales preexistentes (P = 0.02). La cobertura de “Medusahead” también se correlacionó negativamente con la densidad de los zacates amacollados altos perennes (P = 0.03). Estos resultados sugieren que las barreras de contención alrededor de las infestaciones de “Medusahead” solo deberían ser de unos pocos metros de ancho para ser efectivas. Este estudio también sugiere que promover o mantener zacates amacollados altos perennes en áreas con riesgo de invasión puede reducir el éxito de establecimiento del “Medusahead”. La densidad de zacates amacollados altos perennes y zacates anuales, en combinación con datos de suelo, pueden ser útiles para predecir la susceptibilidad a la invasión de “Medusahead”.

Herbaceous Response to Cattle Grazing Following Juniper Cutting in Oregon

The rapid expansion of western juniper (Juniperus occidentalis spp. occidentalis Hook.) across the northern Great Basin has diminished shrub and understory plant composition and reduced forage production. Juniper removal has accelerated during the past decade in Oregon and California to restore shrub–steppe plant communities. Livestock grazing can affect posttreatment successional dynamics, but these impacts have not received adequate study. This study evaluated herbaceous plant recovery in a cut western juniper woodland subjected to grazed and ungrazed prescriptions over 4 growing seasons. The study consisted of 4 treatments: ungrazed cut, grazed cut, ungrazed woodland, and grazed woodland. Stocking rates were 0.78 cow–calf pairs per ha for 5 days in the first year following treatment and 0.94 cow–calf pairs per ha for 4 days in the second year after treatment. The grazing portion of the study lacked true replication because grazed plots were not independent of each other (cattle had access to all plots simultaneously). This limits the strength and interpretation of the grazing results. Juniper cutting removed overstory interference and resulted in significant increases in herbaceous cover, biomass, and seed production when compared to adjacent woodlands. Herbaceous cover, standing crop, perennial grass density, and seed production all increased in the ungrazed cut treatment compared to ungrazed woodland. A similar level of response was measured in the grazed pasture where herbaceous responses were greater in the grazed cut vs. the grazed woodland. Grazing in the cut treatment did not limit herbaceous recovery except that perennial grass seed production was lower in the grazed cut than in the ungrazed cut. Rest or deferment is required the first several growing seasons after juniper cutting to provide plants the opportunity to maximize seed crops. These results imply that juniper cutting had a greater effect on herbaceous dynamics than did the grazing application.

Vegetation Responses to Roller Chopping and Buffelgrass Seeding in Argentina

T-4464 Buffelgrass (Cenchrus ciliaris L.) is an introduced grass used extensively for restoring forage capacity of denuded shrublands in the arid Chaco region in central western Argentina. Currently, the technique of roller chopping and simultaneous buffelgrass seeding is widespread, but information is lacking about its effects on forage production and other vegetation attributes at the regional scale. The purpose of our study was to compare grass yield; vegetation cover and density; and species richness, diversity, and evenness, between roller chopping and simultaneous buffelgrass seeding with nontreated native degraded shrublands. Eight sites, including matched pairs of treated and nontreated areas, were studied. Grass yield, total perennial grass cover, and total perennial grass density were higher (P 0.05). Nonsignificant differences (P > 0.05) between treated and nontreated areas were detected in tree cover and density, species number, diversity index, and evenness. The results of this study indicate that, in the short term, roller chopping and simultaneous buffelgrass seeding produces rapid increases in grass cover and grass yield, and a drastic reduction in shrub cover without affecting species diversity on degraded shrublands of the arid Chaco region of Argentina.

Herbaceous Response to Cattle Grazing Following Juniper Cutting in Oregon

The rapid expansion of western juniper (Juniperus occidentalis spp. occidentalis Hook.) across the northern Great Basin has diminished shrub and understory plant composition and reduced forage production. Juniper removal has accelerated during the past decade in Oregon and California to restore shrub-steppe plant communities. Livestock grazing can affect posttreatment successional dynamics, but these impacts have not received adequate study. This study evaluated herbaceous plant recovery in a cut western juniper woodland subjected to grazed and ungrazed prescriptions over 4 growing seasons. The study consisted of 4 treatments: ungrazed cut, grazed cut, ungrazed woodland, and grazed woodland. Stocking rates were 0.78 cow-calf pairs per ha for 5 days in the first year following treatment and 0.94 cow-calf pairs per ha for 4 days in the second year after treatment. The grazing portion of the study lacked true replication because grazed plots were not independent of each other (cattle had access to all plots simultaneously). This limits the strength and interpretation of the grazing results. Juniper cutting removed overstory interference and resulted in significant increases in herbaceous cover, biomass, and seed production when compared to adjacent woodlands. Herbaceous cover, standing crop, perennial grass density, and seed production all increased in the ungrazed cut treatment compared to ungrazed woodland. A similar level of response was measured in the grazed pasture where herbaceous responses were greater in the grazed cut vs. the grazed woodland. Grazing in the cut treatment did not limit herbaceous recovery except that perennial grass seed production was lower in the grazed cut than in the ungrazed cut. Rest or deferment is required the first several growing seasons after juniper cutting to provide plants the opportunity to maximize seed crops. These results imply that juniper cutting had a greater effect on herbaceous dynamics than did the grazing application.

Vegetation Responses to Roller Chopping and Buffelgrass Seeding in Argentina

T-4464 Buffelgrass (Cenchrus ciliaris L.) is an introduced grass used extensively for restoring forage capacity of denuded shrublands in the arid Chaco region in central western Argentina. Currently, the technique of roller chopping and simultaneous buffelgrass seeding is widespread, but information is lacking about its effects on forage production and other vegetation attributes at the regional scale. The purpose of our study was to compare grass yield; vegetation cover and density; and species richness, diversity, and evenness, between roller chopping and simultaneous buffelgrass seeding with nontreated native degraded shrublands. Eight sites, including matched pairs of treated and nontreated areas, were studied. Grass yield, total perennial grass cover, and total perennial grass density were higher (P &lt; 0.05) on treated areas. Increase in grass yield on treated areas compared with nontreated areas was related to the increase in total perennial grass cover due to added buffelgrass cover (r2 = 0.79). Shrub cover was lower (P &lt; 0.05) on treated areas, but shrub density was not different between treatments (P &gt; 0.05). Nonsignificant differences (P &gt; 0.05) between treated and nontreated areas were detected in tree cover and density, species number, diversity index, and evenness. The results of this study indicate that, in the short term, roller chopping and simultaneous buffelgrass seeding produces rapid increases in grass cover and grass yield, and a drastic reduction in shrub cover without affecting species diversity on degraded shrublands of the arid Chaco region of Argentina.

Seedling recruitment of perennial grasses in degraded areas of the Patagonian Monte

Abstract The recruitment of perennial grass seedlings in degraded areas of the Patagonian Monte was analyzed. Recolonization of large bare-soil areas by dwarf shrubs or perennial grasses was hypothesized to create favorable microsites for grass seedling recruitment. Under natural field conditions, soil moisture (0–20 cm), root biomass (0–20 cm), the soil seed bank of perennial grasses, and density of perennial grass seedlings in the center of large bare soil areas and in microsites neighboring isolated plants of perennial grasses and dwarf shrubs were assessed. A manipulative experiment was conducted to evaluate seedling recruitment at the 3 microsites with identical density of seed addition of perennial grasses, under situations of root exclusion, and water addition. Under natural field conditions, root biomass did not differ among microsites. Soil moisture, seed density, and seedling density of perennial grasses were higher near perennial grasses than in bare soil or next to dwarf shrubs. Recruitment of...