Total Grass Cover Research Articles

Small effects of livestock grazing intensification on diversity, abundance, and composition in a dryland plant community.

Livestock grazing is a globally important land use and has the potential to significantly influence plant community structure and ecosystem function, yet several critical knowledge gaps remain on the direction and magnitude of grazing impacts. Furthermore, much of our understanding of the long-term effects on plant community composition and structure are based on grazer exclusion experiments, which explicitly avoid characterizing effects along grazing intensity gradients. We sampled big sagebrush plant communities using 68 plots located along grazing intensity gradients to determine how grazing intensity influences multiple aspects of plant community structure over time. This was accomplished by sampling plant communities at different distances from 17 artificial watering sources, using distance from water and cow dung density as proxies for grazing intensity at individual plots. Total vegetation cover and total grass cover were negatively related to grazing intensity, and cover of annual forbs, exotic cover, and exotic richness were positively related to grazing intensity. In contrast, species richness and composition, bunchgrass biomass, shrub density and size, percentage cover of bare ground, litter, and biological soil crusts did not vary along our grazing intensity gradients, in spite of our expectations to the contrary. Our results suggest that the effects of livestock grazing over multiple decades (mean=46 years) in our sites are relatively small, especially for native perennial species, and that the big sagebrush plant communities we sampled are somewhat resistant to livestock grazing. Collectively, our findings are consistent with existing evidence that indicates the stability of the big sagebrush plant functional type composition under current grazing management regimes.

Fire frequency effects in a grassy woodland: Trees and grasses

AbstractOur study investigated the effects of fire frequency on the tree and grass components of Cumberland Plain Woodland, an endangered grassy eucalypt woodland in eastern Australia. We located three sites within each of three fire frequency classes (high, moderate, low) based on fire history and a similar time since last fire. For trees, we asked whether fire frequency affected density, eucalypt population structure, basal area and spatial patterning. For grasses, we tested for fire frequency effects on total abundance and the abundance of two common species. Density of trees was not significantly affected by fire frequency for juveniles, saplings or adult trees and neither was basal area per hectare. Features of a recruitment bottleneck model were present for eucalypts. There was a large pool of suppressed juveniles making up more than half the population at each fire frequency. Saplings were the smallest group and were susceptible to fire‐induced stem mortality, with particularly low numbers relative to juveniles and small trees where fire was frequent or intense. Despite this difference in sapling mortality, numbers of small trees did not differ with fire frequency. Saplings could transition to small trees in equal numbers if they did so more quickly at high than at lower fire frequencies, and if recruitment of saplings into the tree layer was controlled independently of fire frequency. The size hierarchy of small to medium eucalypt trees was homogeneous over eight of the nine sites, spatial patterning of adult trees was random tending to regular, and mean tree size decreased with density at all sites. These features of eucalypt population structure are indicative of possible resource competition which could regulate tree recruitment. Total grass cover index was high across all fire frequencies, with Themeda triandra dominating at high and moderate fire frequencies and Microlaena stipoides at low fire frequency.

Plant invasions alter settlement patterns of breeding grassland birds

AbstractAnimals have evolved strategies to identify areas that provide the resources and environmental conditions they need to survive and reproduce. To explore how invasions by nonnative plants might disrupt this fundamental process, we evaluated settlement patterns of migratory birds that breed in grasslands being invaded by two structurally different congeneric grasses. We established 40, 2.25‐ha plots across an area where the composition of each nonnative grass ranged from 0% to nearly 100% of total grass cover, which provided individuals with the full range of alternatives in species composition. We then used the temporal sequence by which birds established territories to infer their habitat preferences. We evaluated responses of the most common species that settled the area, two confamilial sparrows that differed markedly in habitat breadth. The species with narrower habitat breadth, the grasshopper sparrow (Ammodramus savannarum ammolegus), first established territories in areas dominated by native grasses, where grass height and cover were substantially lower than in areas dominated by the nonnative grasses. As the settlement period progressed, they increasingly established territories in areas dominated by the smaller nonnative grass (Eragrostis lehmanniana), but never established territories in areas dominated by the larger grass (E. curvula). In contrast, the species with broader habitat breadth, the Botteri's sparrow (Peucaea botterii arizonae), established territories without regard to grass composition, likely because both nonnative grasses were within the structural range of native grasses used by this grassland generalist. Our results demonstrate that in areas invaded by nonnative plants, changes in habitat use by animals can reflect the interaction between their habitat breadth and the amount of structural contrast between invading plants and the native plant species that are displaced. This interaction provides a mechanism to explain the variation in responses among species to invasions by nonnative plants, which has consequences for broad‐scale changes in the geographic distribution of many species.

Success of organic and biodynamic system experiment to produce high quality wines

Reducing input use and in particular pesticide use is very important in OIV 2018 new resolutions. Also Europe and France promote research and co-design with winegrowers in more sustainable viticulture according to a combination of climate change. It is also very important to take into account soil diversity and Protected Designation Areas constraints to make sure that new wines will ensure the sustainability of the wineries. This study explores design, experiment and assess of new realistic viticulture production systems located in Protected Designation of Origin (PDO) areas and with already organic or biodynamic certification for six consecutive years, in winery production conditions. It also discusses the chosen assessment indicators and the adoption of such new production systems by winegrowers. Eleven cases were studied in a system experiment network in Alsace (France) and in six consecutive production years. Contrasted production years, PDO areas combined to organic or biodynamic certification allow testing the resilience of experimented systems over time. Combination of new practices are tested to drastically reduce input and in particular pesticide. Assessed performances of the systems deal with 14 main indicators: social acceptability (1) and economic viability (1), agronomy (yield (1), harvested berries quality (2), fungi damage (3), soil quality (1), and wine sensorial analysis (1) and environment (Frequency Treatment Index (1), Cupper rate (1), INDIGO® method (2)). Several innovations were selected by co-design with winegrowers: adding essential oil and Propolis to copper spraying; total grass cover of the vine site; new decision rules for rate and time pesticide spraying; decision aid tool; resistant grape varieties planted. The assessment results support that the performance of the 14 indicators is very good for most of the eleven systems during the six assessed years. Combinations of tested innovations are neither dangerous nor difficult to enforce in the field by the vineworkers. Innovations do not increase the cost of grape production. The yield ratios were satisfactory the 6-yeared of observation because calculated yield match with targeted yield. Harvested berries quality support that the 7 vine sites succeed in targeted total acidity and sugar rate according to the different PDO conditions every years. Wines were Alsace or Grand Cru PDO labelled and successful marketed. At least, the Treatment Frequency Index is reduced by an average of 40% for all vine sites and assessed years. TFI can be reduced at a maximum of 89% and TFI median is 38%. Cupper rate can be reduced at a maximum of 97% and Cupper rate median is 54%. I-pest from INDIGO® method indicate a minimal risk taking for groundwater, surface water, air and beneficial organisms contamination. And finally, flora richness indicator is stable or steadily increases during the 6 study years. In this study, we demonstrated that drastically monitoring reduction of pesticide and other inputs is possible. Chosen indicators allow a exhaustive assessment, but could also been aggregated all together to give a synthetic information to winegrowers and make them easier to adopt the innovative systems. Introduction of innovation combinations in highly sustainable organic and biodymanic systems are validated to produce high quality wines. Now, it is possible to serenely promote and disseminate these highly sustainable innovative systems, taking into account of course vineyard diversity.

A warmer and drier climate in the northern sagebrush biome does not promote cheatgrass invasion or change its response to fire

Dryland shrub communities have been degraded by a range of disturbances and now face additional stress from global climate change. The spring/summer growing season of the North American sagebrush biome is projected to become warmer and drier, which is expected to facilitate the expansion of the invasive annual grass Bromus tectorum (cheatgrass) and alter its response to fire in the northern extent of the biome. We tested these predictions with a factorial experiment with two levels of burning (spring burn and none) and three climate treatments (warming, warming + drying, and control) that was repeated over 3 years in a Montana sagebrush steppe. We expected the climate treatments to make B. tectorum more competitive with the native perennial grass community, especially Pseudoroegneria spicata, and alter its response to fire. Experimental warming and warming + drying reduced B. tectorum cover, biomass, and fecundity, but there was no response to fire except for fecundity, which increased; the native grass community was the most significant factor that affected B. tectorum metrics. The experimental climate treatments also negatively affected P. spicata, total native grass cover, and community biodiversity, while fire negatively affected total native grass cover, particularly when climate conditions were warmer and drier. Our short-term results indicate that without sufficient antecedent moisture and a significant disruption to the native perennial grass community, a change in climate to a warmer and drier spring/summer growing season in the northern sagebrush biome will not facilitate B. tectorum invasion or alter its response to fire.

Enduring a decade of drought: Patterns and drivers of vegetation change in a semi-arid grassland

This study evaluated patterns and drivers of vegetation change in a semi-arid grassland in southern Arizona across eleven years of extended drought and high temperatures, 2004–2014. Changes included declines in C4 perennial grass basal cover with patchy grass mortality, leaf litter increases, shrub declines, and increases in non-native grass Eragrostis lehmanniana. Linear mixed-effects models identified precipitation during January–June “extended spring” as the best predictor of grass basal cover, especially when plots were grouped by soil and topographic features. Models showed that a decrease in extended spring precipitation from 150 to 50 mm was associated with loss of one-quarter to one-half of plots' total grass cover. Association of grass declines with this novel season of drought is especially relevant because global circulation models predict steep declines in spring rainfall. Increasing E. lehmanniana dominance was also associated with native grass declines. There was little support over this time for predicted effects of livestock grazing or shrub encroachment. This study demonstrated how monitoring data from working landscapes can improve ecological understanding of drought. Findings also suggest managers could improve chances for sustaining resilience by responding to rainfall in multiple seasons, monitoring for mortality events, and establishing contingency plans for various types of drought.

Observations On The Ecology Of Earthworms And Its Effect On The Population Dynamics Of Cellulolytic Bacteria In Soils Across Selected Habitats In Imo State University Main Campus Owerri, Nigeria

This study was aimed at investigating the relationship between the population dynamics of earthworms and the populations of total and cellulolytic bacteria in the soil across selected sites within the Imo State University main Campus Owerri, Nigeria. Four habitats, namely, land with trees and grass cover, lawn with total grass cover, lawn with scanty grass cover and abandoned farmland where selected and composite soil samples were collected from them. After analyzing some physico-chemical properties of soil samples, the total number of bacteria in nutrient-agar and aerobic cellulolytic bacteria in cellulose-agar were counted. Assessment of bacterial cellulolytic activity was performed via measurement of clear zone around of colony. Also, earthworms were collected from the study sites and their population density, biomass, length, proportion of adults and juveniles and taxonomic features were compared among the four habitats. Result showed that the land with trees and grass cover recorded the highest total bacteria, aerobic cellulolytic bacteria, proportion of cellulolytic bacteria, worm density, worm biomass, and worm length (241.4x10 4 cfu/g, 123.8x10 4 cfu/g, 51.28%, 37.5+10.8m -2 , 5.2+2.1gm -2 and 20.4+8.1cm), followed by the lawn with total grass cover (203.6x10 4 cfu/g, 96.8x10 4 cfu/g, 47.54%, 23.5+6.4m -2 , 3.3+1.8gm -2 and 13.4+6.2cm), the lawn with scanty grass cover (127.3x10 4 cfu/g, 34.7x10 4 cfu/g, 27.26%, 16.7+5.3m -2 , 2.3+0.5gm -2 and 11.9+2.3cm) and the abandoned farmland (106x10 4 cfu/g, 23.8x10 4 cfu/g, 22.37%, 11.8+4.4m -2 , 1.6+0.3gm -2 and 12.8+3.1cm). Mean ratio of clear zone diameter to colony were 1.60+0.42, 1.3+0.36, 0.8+0.22 and 1.93+0.25 for the land with trees and grass cover, the lawn with total grass cover, the lawn with scanty grass cover and the abandoned farmland, respectively. Higher ability of the cellulolytic bacteria in the abandoned farmland and the land with trees and grass cover may be due to species diversity. All four habitats had a higher proportion of adult earthworms than juvenile earthworms in an approximate ratio of 3:1, adult: juvenile. Finally, the taxonomic status of the earthworms in all four habitats suggested that they may belong to the same species. However, species identification was not attempted.

Vegetation and Avian Response to Oak Savanna Restoration in the Mid-South USA

Abstract Oak (Quercus spp.) savannas are among the most imperiled ecosystems in the United States. Consequently, associated vegetation and avian communities are also in decline. Furthermore, restoration of savanna communities may be an important strategy for conserving avian species that require early successional habitat, a type underrepresented on regional landscapes. Therefore, we evaluated savanna restoration on twelve sites in the Mid-South USA. Specifically, we examined grass, forb, legume, and woody understory cover, regeneration and sapling density, and breeding bird use of the sites following mechanical overstory thinning and dormant-season fire using a hierarchical linear model. Total grass cover was negatively related to canopy cover (P < 0.01) and total forb cover was negatively related to total basal area (P = 0.04). Oak regeneration density was positively related to canopy cover (P < 0.01), while oak competitor regeneration density was positively related to percent slope (P = 0.01) and s...

Effectiveness of the GAEC standard of cross compliance Management of set aside on soil erosion control

The GAEC standard Management of set aside is applied to arable lands subjected to set aside and kept non-cultivated throughout the year. The standard is also applied to other set aside areas eligible for direct payments. For the implementation of this Standard, the farmer must assure the presence of natural or artificial green cover on the surface throughout the year and adopt consistent agronomic practices as mowing, or other equivalent, in order to maintain the normal state of soil fertility, protect wildlife, prevent the formation of a potential inoculum of fires, especially during drought and prevent the spread of weeds. Up to the CAP Health Check the legislation on the set aside required the farmer to plough the soil by mid-May. Therefore, the natural vegetation cover could neither establish nor express its value against erosion throughout the year. Since mid 2004, cross compliance has banned ploughing of set aside surfaces. This novelty is very important in relation to the effectiveness of the standard in erosion control. In Italy there are only few studies carried out in the field that have measured the effect of set aside on soil erosion. The few existing experiments regarded the effect of set aside managed in accordance with the CAP dictates prior to the CAP Health Check. The results of case studies show very contrasting results regarding soil erosion on set aside plots managed through the annual ploughing in the period in which this rule remained in force. This finding can be explained by considering that most of soil erosion in the Mediterranean environment is determined by extreme events; so, set aside resulted ineffective in protecting the soil, when very erosive events occurred on bare soil (soil in seed bed condition after ploughing and harrowing) or when the plant cover of soil was still scarce. In these conditions soil erosion rate resulted similar to that observed in the intensive cropping systems. On the contrary, for events occurred when the natural vegetation was sufficiently developed, the beneficial effect of set aside in limiting erosion was similar to that exerted by total grass cover. In general, it can be argued that on plough set aside, an average period of 2 months is needed for the establishment of natural cover sufficient enough to ensure a significant protection of soil from erosion. The results show that in Italy set aside before the CAP Health Check might have determined a decrease of soil erosion by 50% (on average). Since 2005, set aside under cross compliance regime appears to have had a greater beneficial effect than before in reducing erosion, as total grass cover was able to decrease soil loss by 98% compared to intensive farming systems.

Selective logging and fire as drivers of alien grass invasion in a Bolivian tropical dry forest

Logging is an integral component of most conceptual models that relate human land-use and climate change to tropical deforestation via positive-feedbacks involving fire. Given that grass invasions can substantially alter fire regimes, we studied grass distributions in a tropical dry forest 1–5 yr after selective logging, and experimentally tested the effect of forest fire on populations of invasive grasses. In unlogged forests and in microhabitats created by selective logging we found a total of four alien and 16 native grass species. Grasses covered 2% of unlogged and 4% of logged forest, with grass cover in logged forest concentrated in areas directly disturbed by logging; log landings and roads had relatively greater grass cover (37% and 17%, respectively) than did skid trails (10%) and felling gaps (8%). Total grass cover and grass species richness increased with canopy openness and were greatest in sites most severely disturbed by logging. The grass flora of these disturbed areas was composed mostly of native ruderal species (e.g., Digitaria insularis, Leptochloa virgata), a native bamboo ( Guadua paniculata), and Urochloa ( Panicum) maxima, a caespitose C 4 pasture grass introduced from Africa. Urochloa maxima formed monodominant stands (up to 91% cover and 2–3 m tall) and grew on 69% of log landings and 38% of roads. To better understand the potentially synergistic effects of logging and fire on the early stages of grass invasion, we tested the effect of a 12-ha experimental fire on U. maxima populations in a selectively logged forest. Three years after the fire, the area covered by alien grass in burned forest increased fourfold from 400 m 2 (pre-fire) to 1660 m 2; over the same period in a logged but unburned (control) area, U. maxima cover decreased from 398 m 2 to 276 m 2. Increased canopy openness due to fire-induced tree mortality corresponded with the greater magnitude of grass invasion following fire. Selective logging of this dry forest on the southern edge of the Amazon Basin promotes alien grass invasion; when coupled with fire, the rate of invasion substantially increased. Recognition of the grass-promoting potential of selective logging is important for understanding the possible fates of tropical forests in fire-prone regions.

Survival of Greater Sage‐Grouse Chicks and Broods in the Northern Great Basin

ABSTRACT Reduced annual recruitment because of poor habitat quality has been implicated as one of the causative factors in the range‐wide decline of sage‐grouse (Centrocercus urophasianus) populations since the 1950s. Because chick and brood survival are directly linked to annual recruitment and may be the primary factors that limit sage‐grouse population growth, we estimated 28‐day survival rates of radiomarked chicks and broods from 2000 to 2003. We examined relationships between survival and several habitat variables measured at brood sites, including food availability (insects and forbs); horizontal cover of sagebrush, grasses, and forbs; and vertical cover of sagebrush and grass. We monitored 506 radiomarked chicks from 94 broods; chick survival was 0.392 (SE = 0.024). We found evidence that both food and cover variables were positively associated with chick survival, including Lepidoptera availability, slender phlox (Phlox gracilis) frequency, total forb cover, and grass cover. The effect of total grass cover on chick survival was dependent on the proportion of short grass. The hazard of an individual chick's death decreased 8.6% (95% CI = −1.0 to 18.3) for each percentage point increase in total grass cover when the proportion of short grass was &gt;70%. Survival of 83 radiomarked broods was 0.673 (SE = 0.055). Lepidoptera availability and slender phlox frequency were the only habitat variables related to brood survival. Risk of total brood loss decreased by 11.8% (95% CI = 1.2–22.5) for each additional Lepidoptera individual and 2.7% (95% CI = −0.4 to 5.8) for each percentage point increase in the frequency of slender phlox found at brood sites. Model selection results revealed that temporal differences in brood survival were associated with variation in the availability of Lepidoptera and slender phlox. Years with high brood survival corresponded with years of high Lepidoptera availability and high slender phlox frequency. These foods likely provided high‐quality nutrition for chicks during early growth and development and enhanced survival. Habitat management that promotes Lepidoptera and slender phlox abundance during May and June (i.e., early brood rearing) should have a positive effect on chick and brood survival in the short term and potentially increase annual recruitment.

Impacts of Buffelgrass (Pennisetum ciliare) on a Forb Community in South Texas

AbstractSince the 1950s, many south Texas rangelands have been seeded with buffelgrass, a perennial C4 bunchgrass native to Africa that is believed to contribute to reductions in biodiversity. Forb species represent a critical habitat component throughout the breeding period for many wildlife species as seed (summer to fall), as green vegetative material (spring to summer), and as habitat for arthropods (spring to summer). Reductions in richness and diversity of crucial ecosystem components such as forbs and arthropods have large implications for grassland birds and other wildlife. We sampled annual and perennial forbs within 1-m2 quadrats on 15 study plots (1 ha; n = 20 quadrats/plot) at Chaparral Wildlife Management Area, in LaSalle and Dimmit counties, Texas, during 2005 and 2006. Study plots were divided into five light-buffelgrass plots (0 to 5% buffelgrass canopy coverage), five moderate-buffelgrass plots (5 to 25% buffelgrass canopy coverage), and five heavy-buffelgrass plots (&gt; 25% buffelgrass canopy coverage). Buffelgrass in study plots was composed of naturalized plants, and was not deliberately planted. During 2005 we observed that plots with &gt; 25% buffelgrass had a 73% reduction in forb canopy of native species, a 64% reduction in native forb species richness, and a 77% reduction in native forb stem density compared to plots with 0 to 5% buffelgrass. These trends in native forb reduction (−79% native forb canopy, −65% forb species richness, −80% forb stem density) were nearly identical in 2006, even with greatly reduced rainfall. Simple linear regression revealed negative relationships between buffelgrass cover, total exotic grass cover (buffelgrass and Lehmann lovegrass), and total grass cover and the richness, coverage, and density of forbs/m2. Reductions in diversity may have larger implications regarding ecosystem function and available useable space and densities of desired bird species such as northern bobwhite.

Relationships Between Western Juniper (Juniperus occidentalis) and Understory Vegetation

AbstractWestern juniper has been actively invading sagebrush plant communities for about 130 yr. Western juniper canopy cover generally increases as western juniper invades sagebrush steppe communities and succession progresses toward a western juniper woodland. Our goal was to estimate the impact of juniper invasion and canopy increase on understory vegetation structure and productivity on 101 sites in northeastern California. The primary objectives of this study were to: (1) examine the influence of increasing western juniper canopy cover on the composition and productivity of understory vegetation; and (2) assess the effects of western juniper removal on understory vegetation. Sites in early, mid-, and late successional stages and sites on the same soils that had not been invaded were selected. Sites where western juniper had been removed by prescribed fire, mechanical, or chemical methods were compared to adjacent untreated sites. Western juniper canopy cover, understory cover and species composition, productivity, and bare ground were determined at each site during May through July 2005 and 2006. Regression analysis was used to evaluate the relationship between western juniper canopy cover and understory vegetation parameters. Logistic regression was used to detect understory differences between treated (juniper removed) and untreated (juniper not removed) sites. A significant relationship was found between western juniper canopy cover and understory species richness, shrub cover, forb cover, total grass cover, cheatgrass cover, herbaceous productivity, and bare ground. Removal of western juniper increased total grass cover, cheatgrass cover, and productivity, and reduced bare ground. The results of this study support findings by researchers in other states that western juniper influences plant community structure and productivity, and removal of western juniper might reverse these changes in structure, but also might increase opportunities for invasion of cheatgrass.

Patch Configuration Non-linearly Affects Sediment Loss across Scales in a Grazed Catchment in North-east Australia

A principle of the cross-scale interaction (CSI) framework is that disturbance-induced landscape changes resulting in coarser-grained spatial structure may non-linearly amplify transfer processes across scales. We studied suspended sediment losses at two spatial scales (0.24 m2 plots and ca. 0.25 ha hillslopes of about 140 m in length) in a semiarid savanna landscape to determine whether the spatial structure of grassy and bare soil areas introduced a non-linear amplification of sediment loss. Sediment loss rates from 0.24 m2 bare plots averaged 1.527 t ha−1 y−1, which was 23 times the loss rate from nearby grassy plots (0.066 t ha−1 y−1). These rates were then extrapolated linearly to two hillslopes separated by only 200 m and having similar total grass cover, slope and soil type but differing in the spatial structure of bare soil patches. The coarse-grained hillslope had a large bare patch on its lower slope, whereas the fine-grained hillslope had no bare soil patches when quantified at a 4 m grid-cell resolution. Measured sediment loss from the fine-grained hillslope averaged 0.050 t ha−1 y−1, whereas the average sediment loss from the coarse-grained hillslope was 2.133 t ha−1 y−1. By linearly extrapolating from the plot scale, the expected sediment loss for the fine-grained hillslope was 0.066 t ha−1 y−1, which is similar to that observed. The expected sediment loss for the coarse-grained hillslope was 0.855 t ha−1 y−1, where linear extrapolation assumed a 46:54 ratio of bare to grassy plots and that the spatial arrangement of plots does not affect sediment loss processes. For the coarse-grained hillslope observed sediment loss is 2.5 times greater than that expected by linear extrapolation from the plot scale. This result indicates a cross-scale interaction related to spatial configuration of patches. We suggest that there were non-linearities in hillslope ecohydrological transfer processes (runoff, erosion) across scales due to a specific patch configuration that greatly amplified sediment loss because the pattern failed to slow runoff and retain sediment before it entered a creek. This example supports the CSI framework and indicates the importance of considering the effect of spatial structure when predicting system dynamics at different scales.

Herbaceous Restoration of Juniper Dominated Grasslands With Chaining and Fire

Juniper (Juniperus spp.) encroachment in grasslands usually progresses toward a stable woody state of mature trees that requires a significant disturbance to shift succession in another direction. Fire alone is often inadequate to shift succession in dense stands of mature juniper and must be preceded by a mechanical treatment such as chaining to reduce juniper competition and increase herbaceous growth that fuels a subsequent fire. However, little long-term data are available that measure combined effects of mechanical and fire treatments on restoration of juniper-dominated grasslands. Here, on a degraded (40% bare ground) north Texas site dominated by redberry juniper (Juniperus pinchotii Sudw), we quantify long-term herbaceous responses to mechanical chaining followed by fire. Two types of chaining, ground-level and elevated, were evaluated and all chained plots were burned 4 years after chaining. Herbaceous and woody responses were measured for several years after both chaining and fire treatments and compared to untreated controls. At study termination, both of the chaining + fire treatments reduced juniper cover from 32% to < 6%, but mortality was < 10%, because most plants basal-sprouted. Total grass production did not increase in chained treatments over the untreated until 3 growing seasons after chaining. Grass production declined the first growing season following the fire treatment, but increased in treated plots to 3 times the untreated the second and third year postfire. Total grass cover in treated plots did not increase over the untreated until the second year after the fire treatment. There was no difference in juniper or herbaceous responses between the 2 chain types. Results suggest increases in herbaceous production from chaining alone were due to increased growth of existing vegetation patches whereas the fire treatment appeared to stimulate herbaceous recruitment into bare soil areas.

Herbaceous Restoration of Juniper Dominated Grasslands With Chaining and Fire

Juniper (Juniperus spp.) encroachment in grasslands usually progresses toward a stable woody state of mature trees that requires a significant disturbance to shift succession in another direction. Fire alone is often inadequate to shift succession in dense stands of mature juniper and must be preceded by a mechanical treatment such as chaining to reduce juniper competition and increase herbaceous growth that fuels a subsequent fire. However, little long-term data are available that measure combined effects of mechanical and fire treatments on restoration of juniper-dominated grasslands. Here, on a degraded (40% bare ground) north Texas site dominated by redberry juniper (Juniperus pinchotii Sudw), we quantify long-term herbaceous responses to mechanical chaining followed by fire. Two types of chaining, ground-level and elevated, were evaluated and all chained plots were burned 4 years after chaining. Herbaceous and woody responses were measured for several years after both chaining and fire treatments and compared to untreated controls. At study termination, both of the chaining + fire treatments reduced juniper cover from 32% to &lt; 6%, but mortality was &lt; 10%, because most plants basal-sprouted. Total grass production did not increase in chained treatments over the untreated until 3 growing seasons after chaining. Grass production declined the first growing season following the fire treatment, but increased in treated plots to 3 times the untreated the second and third year postfire. Total grass cover in treated plots did not increase over the untreated until the second year after the fire treatment. There was no difference in juniper or herbaceous responses between the 2 chain types. Results suggest increases in herbaceous production from chaining alone were due to increased growth of existing vegetation patches whereas the fire treatment appeared to stimulate herbaceous recruitment into bare soil areas.

Competition and compensation among cattle, zebras, and elephants in a semi-arid savanna in Laikipia, Kenya

Competition and compatibility between livestock and wildlife in Africa has been a point of considerable speculation, with implications for conservation. However, controlled replicated experiments are lacking. Here we report on the results of a long-term exclosure experiment in Laikipia, Kenya, in which different guilds of large mammalian herbivores have been independently manipulated since 1995. In plots from which cattle were excluded, the density of zebra dung in 2000 was on average 46% greater than in control plots. This was due to differential zebra use, and not to differential rates of dung removal (by dung beetles or other factors). Vegetation data indicate that cattle fully compensate for the absence of wildlife; all plots accessible to cattle had similarly low grass cover. However, wildlife do not fully compensate for the absence of cattle; plots with only wildlife had more grass cover than plots accessible to cattle. Zebra dung density was strongly correlated with total grass cover, suggesting that zebras are effectively tracking resource abundance. There is also evidence of pair-wise competition between cattle and elephants, and between elephants and zebras. The strong competition between cattle and zebras appears to be mitigated by the presence of elephants. A significant cattle x elephant interaction on the abundance of zebra dung indicates that elephants reduce the negative effects of cattle on zebras. In the presence of cattle, elephants facilitate the abundance of zebra, apparently by suppressing resource extraction (bite rates) by cattle. The precise mechanism for this indirect facilitation is not clear, but it may be related to the demonstrated reduction in forb cover associated with elephant presence.

Revegetation Methods for High‐Elevation Roadsides at Bryce Canyon National Park, Utah

Abstract Establishment of native plant populations on disturbed roadsides was investigated at Bryce Canyon National Park (BCNP) in relation to several revegetation and seedbed preparation techniques. In 1994, the BCNP Rim Road (2,683–2,770 m elevation) was reconstructed resulting in a 23.8‐ha roadside disturbance. Revegetation comparisons included the influence of fertilizer on plant establishment and development, the success of indigenous versus commercial seed, seedling response to microsites, methods of erosion control, and shrub transplant growth and survival. Plant density, cover, and biomass were measured 1, 2, and 4 years after revegetation implementation (1995–1998). Seeded native grass cover and density were the highest on plots fertilized with nitrogen and phosphorus, but by the fourth growing season, differences between fertilized and unfertilized plots were minimal. Fertilizers may facilitate more rapid establishment of seeded grasses following disturbance, increasing soil cover and soil stability on steep and unstable slopes. However the benefit of increased soil nutrients favored few of the desired species resulting in lower species richness over time compared to unfertilized sites. Elymus trachycaulus (slender wheatgrass) plants raised from indigenous seed had higher density and cover than those from a commercial seed source 2 and 4 years after sowing. Indigenous materials may exhibit slow establishment immediately following seeding, but they will likely persist during extreme climatic conditions such as cold temperatures and relatively short growing seasons. Seeded grasses established better near stones and logs than on adjacent open microsites, suggesting that a roughened seedbed created before seeding can significantly enhance plant establishment. After two growing seasons, total grass cover between various erosion‐control treatments was similar indicating that a variety of erosion reduction techniques can be utilized to reduce erosion. Finally shrub transplants showed minimal differential response to fertilizers, water‐absorbing gels, and soil type. Simply planting and watering transplants was sufficient for the greatest plant survival and growth.

Planted green ash ( Fraxinus pennsylvanica Marsh.) and herbaceous vegetation responses to initial competition control during the first 3 years of afforestation

Formerly row-cropped bottomland sites that have been planted with hardwoods through afforestation programs are typically associated with low tree stocking, slow tree growth, and an enduring influence of agricultural weeds in the herbaceous stratum. Consequently, many of the intended benefits of a forestry land use are delayed or forfeited. This study evaluates the growth of planted green ash and the development of volunteer herbaceous communities on a bottomland site in southern Illinois, USA in response to two different operational herbicide (pre-emergence sulfometuron and post-emergence glyphosate) and tillage treatments, applied individually and in combination. Both herbicide treatments increased green ash height and diameter growth while tillage produced no response. At the end of three growing seasons, the post-emergence glyphosate treatment increased forb cover. Total grass cover was not impacted by herbicide treatments after the second growing season. During the second and third growing seasons, the pre-emergence sulfometuron treatment increased broomsedge ( Andropogon virginicus L.) cover and decreased goldenrod ( Solidago nemoralis Ait.) cover relative to post-emergence glyphosate and no herbicide treatments. Johnsongrass ( Sorghum halepense L.) cover decreased dramatically following the first growing season in all treatments. Horseweed ( Conyza canadensis L.) exhibited a complex response to silvicultural treatments through the course of the study. Commonly used silvicultural treatments that yielded similar and positive tree growth responses differed in their impact on herbaceous community composition through the first 3 years of stand development. These results suggest that treatment choice may have long-term implications for overstory canopy development on these and similar afforested bottomland sites characterized by presence of agricultural weeds and low tree stocking.

The conservation management of Imperata cylindrica grassland in Nepal with fire and cutting: an experimental approach

1. Imperata cylindrica dominated grassland in the Nepal Terai supports a number of threatened species including swamp deer Cervus duvauceli, hispid hare Caprolagus hispidus and Bengal florican Eupodotis bengalensis. It is also the main source of thatch material for local communities. Current widespread cutting and burning of the grasslands is deleterious to cover‐dependent vertebrates which would benefit from patches of grassland remaining unmanaged. 2. In Royal Bardia National Park, a randomized block experiment with four treatments (cutting, burning, cutting and burning, and no management) was established to examine the effects of these treatments on plant species abundance, species richness and grassland structure. The grassland was dominated by Imperata cylindrica, with Saccharum spontaneum, Vetiveria zizanioides, Desmostachya bipinnata and Schizachyrium brevifolium the other abundant species. 3. In year 3, 2 years after the first treatment, Imperata cylindrica remained the dominant grass species under all treatments. It increased in abundance in unmanaged plots and declined in abundance in managed plots. Desmostachya bipinnata showed the opposite response. Plant species richness was significantly higher in managed plots, which were structurally more heterogeneous. 4. The effects of cutting alone, burning alone, and cutting and burning combined on the structure and composition of the grassland were similar, despite additive effects on total grass cover, total forb cover and forb species richness in cut and burned plots. This allows the effects of cutting and burning to be reduced to a single treatment (cutting and burning) in future experiments to investigate the impacts of patch harvesting on community dynamics. Simpler factorial experiments can be designed than if cutting and burning had to be considered as separate treatments. 5. There was no difference in the establishment of tall grass species or woody species between managed and unmanaged plots. 6. Results suggest that patches of grassland could be left unmanaged on a 2‐year rotation without significantly altering the composition of the plant community, thereby providing refugia for cover‐dependent faunal species.