Increase In Grass Cover Research Articles

Diversification of Pinus halepensis forests by sowing Quercus ilex and Quercus pubescens acorns: testing the effects of different vegetation and soil treatments

The goal of this study was to develop management strategies favouring establishment and survival of holm oak (Quercus ilex L.) and downy oak (Quercus pubescens Willd.)—two species co-occurring in Southern France—in mature Allepo pine forests (Pinus halepensis Mill subsp. halepensis). An experimental design was assessed in a partially cut mature stand of Aleppo pine in which five soil and vegetation treatments—chopping, chopping followed by scarification in one or two directions, prescribed burning, control—and two slash treatments (presence/absence) were applied. A total of 1,600 sowing points, each composed of 3 Q. ilex or Q. pubescens acorns, were installed in the different treatments in November of two consecutive years at 6 and 18 months, after the end of treatments. Survival was monitored 3 and 2 years after sowing, soil surface at the sowing points was characterized at different dates, and predawn leaf water potentials were measured during the dry season. High mortality occurred after the first summer, but survival after 1 year was 2.3–5.2 higher in Q. ilex than in Q. pubescens, confirming that Q. ilex was better adapted to the drier parts of the Mediterranean area. Survival was significantly influenced by the treatments, but there was a variable response between the two sowing years under most of the treatments. Only intense fire proved the most beneficial treatment for seedling survival in both years. The micro-local soil cover conditions induced by the treatments played a major role in explaining oak survival. In particular, grass cover (mainly Brachypodium retusum) proved to be largely unfavourable to seedling survival and growth, and this detrimental effect was also confirmed by lower predawn leaf water potential values with increasing grass cover. Acorn introduction designed to diversify mature Aleppo pine forest after soil and vegetation treatments therefore has to be considered for treatments that most efficiently impair the pre-existing competing grass cover such as prescribed high-intensity fire treatment.

Impacts of management and enclosure age on recovery of the herbaceous rangeland vegetation in semi-arid Kenya

Establishment of seasonal grazing enclosures has become an important rangeland rehabilitation strategy in semi-arid regions. This study assessed the impact of enclosure age and enclosure management on the vegetation composition in the Njemps Flats range unit, Lake Baringo Basin (Kenya). Six communal enclosures (13e23 years since establishment) and six private enclosures (3e17 years since establishment) were selected. Point-line transect and quadrat-based measurements were made of herbaceous cover, functional group relative abundance and standing crop inside the enclosures and in the adjacent open rangeland. Unpalatable forbs and sedges dominated the herbaceous vegetation of the degraded open rangeland. Informal semi-private land ownership reduced open rangeland degradation as shown by a higher cover of surviving annual grasses. Rangeland enclosure fostered regeneration of annual and perennial grasses, and significantly increased grass cover and standing crop. Private and communal enclosure management were equally successful in rehabilitating grass cover. Standing crop in the communal enclosures was fully recovered, but it was sub-optimal in all private enclosures reflecting recent grazing or grass cutting activities. The variability in rehabilitation success highlights the high potential of individual herders’ incentives to promote rangeland rehabilitation but also stresses the importance of more detailed characterisation and monitoring of the enclosure management decisions.

Efficacy of Grass for Mitigating Runoff and Erosion from an Artificial Loessial Earthen Road

Runoff and soil losses from earthen hillside roads are a serious problem on the Loess Plateau in China. We constructed artificial road sections (2.0 m long, 0.55 m wide, 0.35 m deep, 15° slope) with loessial soil packed to give a representative bulk density of 1.5 g cm-3 and planted with different degrees of grass cover (0%, 30%, 40%, 50%, 60%, or 70%). Simulated rainfall (120 mm h-1 for 1 h) was applied to the road sections, and we examined the hydraulic characteristics of the overland flow that was generated and the amount of runoff and sediment yield produced over time. Increasing grass cover inhibited overland flow (as indicated by lower Froude and Reynolds numbers), increased friction and surface roughness (as indicated by Manning and Darcy-Weisbach coefficients), and reduced mean flow velocities. Lower impact energies of raindrops intercepted by the grass led to reduced surface seal formation and detachment of soil particles. This in turn resulted in amounts of runoff and sediment from the grassed roads that were 12.4% to 27.9% and 39% to 76% smaller, respectively, than those from the bare roads. Reductions in sediment yields, which were exponentially related to the degree of cover, were also attributable to reduced carrying capacity of the runoff. Therefore, grass growing on loessial earthen roads can mitigate soil losses effectively and, to a lesser degree, runoff amounts.

Long-term effects of a wildfire on a lizard assemblage in the Arid Chaco forest

The long-term (14 years) effects of a high-intensity wildfire on a lizard assemblage were studied in Chancaní Provincial Natural Park and Forest Natural Reserve (Córdoba, Argentina), by comparing a burned area with an unburned one within the protected area. Lizard diversity and abundance were measured using 25 drift-fence pitfall traps in the burned area and in a portion of the unburned forest during two summers (2006–2007 and 2007–2008). A total of 426 lizards belonging to eight species were captured. Total captures were 40% higher in the unburned area than in the burned one. From the eight species recorded, five ( Homonota fasciata, Leiosaurus paronae, Stenocercus doellojuradoi, Liolaemus chacoensis, and Teius teyou) were more abundant in the unburned area, whereas the remaining species ( Tropidurus etheridgei, Mabuya dorsivittata and Vanzosaura rubricauda) did not differ between areas. The differences observed in lizard numbers between sites may be related to fire-driven changes. A marked increase in grass cover determining the reduced availability of bare and litter-covered ground, fallen logs and dead wood, favorite microhabitats for most lizard species, is of particular significance.

Does herbicide weed control increase livestock production on non-equilibrium rangeland?

Herbicides have been applied extensively on rangelands to reduce forbs that were considered undesirable, which has been assumed to lead to an increase in grass production and ultimately to an improvement in livestock performance. While scores of research studies support the premise that forb suppression can increase desirable forage on plot-level studies, only a few studies have attempted to quantify the effect on livestock production within experimental units equivalent in area to production-scale pastures. We therefore tested the effect of herbicide on mixed prairie vegetation and on livestock gain on pastures typical in area, stocking rate, and composition to working ranches in the region. Picloram and 2,4-d at 0.15 and 0.56kg/ha, respectively, were applied aerially in spring of 2001 and again in spring of 2004 to two pastures. Two untreated control pastures were managed identically, including grazing management, but were not treated with herbicide. Canopy cover by species and cover of bare ground and litter were estimated in permanently located plots, and stocker cattle performance (average daily gain per head; ADG) and total cattle gain (kgha−1) were measured from 2000 to 2005. Forb cover was less (P<0.05) in herbicide treated pastures than in control pastures in the year of herbicide application (2001 and 2004) and for second growing season following the treatment (2 YAT) in the 2004 application. Grass cover varied more with annual precipitation than with treatment. Livestock ADG and gain ha−1 did not differ between treatments in any year or across years. Livestock production varied among years, reflecting variation in growing-season precipitation that is characteristic of non-equilibrium rangelands. Herbicide altered the plant community by reducing forb cover and increasing grass cover, but livestock production was not altered either on an individual basis (gain/head) or on an area basis (gain/ha). Livestock production per area (gain/ha) might be increased if grass production after herbicide treatment could be predicted reliably. However, predicting grass production is notoriously difficult in rangeland ecosystems that have high inter-annual variation in precipitation. Reliable adjustments in stocking rate to harvest grass released from forb competition is unlikely and therefore fraught with risk.

The effects of deer browsing on woodland structure and songbirds in lowland Britain

The effects of deer in woodlands are known to result in habitat changes which can be detrimental to songbirds. In the first part of the paper we review the effects that deer may have on critical resources for woodland birds. The principal mechanism by which deer may affect habitat quality is through the reduction of low woody vegetation, which forms a key element of the preferred habitat of several species – this may be associated with loss of nest‐sites, increased exposure to predators and reduction of food. The second part of the paper presents new evidence for the impacts of deer on vegetation structure, and how they may be contributing to the declines of some woodland songbirds in Britain. Results from extensive studies of deer at 13 woodland sites in England and Wales reveal that understorey foliage density decreases significantly with increasing deer density. Reduction of foliage was greatest at below 1.5 m above ground. We also report preliminary results of an experimental comparison of songbird densities between deer‐fenced and unfenced areas of young coppice woodland in eastern England. In this study, deer browsing caused extensive impacts on vegetation structure in young coppice, though there was considerable variation between plots. Deer browsing resulted in reduction of canopy cover, reduction in density and cover of understorey vegetation, and an increase in grass cover. Abundance of bird species using the understorey, including all migrants, was significantly higher in coppice where deer were excluded. These results lend support to the hypothesis that deer are at least partly responsible for causing declines in some British bird populations, but they do not eliminate the possibility that increased shading is also responsible for changes in woodland structure. At present there is much spatial variation in deer densities in Britain so that impacts on low vegetation and habitat quality for birds are not expected to be the same in all regions. However, with continuing increases in deer numbers it is to be expected that such impacts will become more widespread.

Runoff hydraulic characteristics and sediment generation in sloped grassplots under simulated rainfall conditions

Evaluation of grass influence on soil erosion process can provide important information in soil and water conservation. The laboratory experiment was conducted to study runoff and sediment producing processes and runoff hydraulics in the grassplots with different covers (35%, 45%, 65% and 90%) and bare soil plot (control) at a slope of 15. The results showed that grass significantly reduced runoff and sediment. Compared with bare soil plot, the grassplots had a 14-25% less runoff and an 81-95% less sediment, and played a more important role in reducing sediment at the final stage of rainfall. There was a significantly negative logarithmic relationship between sediment yield rate (SDR) and cover (C): SDR = 1.077-2.911 ln(C) (R-2 = 0.999'). Sediment yield rate of grassplots decreased with rainfall duration, and decreased linearly as runoff rate increased. Overland flow velocities deceased with increase in grass cover, and the cover had greater effect on lower slope velocity than upper one. Froude numbers decreased with increase in cover, and flow regimes of all treatments were laminar and tranquil. Darcy-Weisbach and Manning friction coefficients of grassplots increased as ground cover increased. Therefore, increase in grass coverage can efficiently reduce soil loss and improve ecological environments. (c) 2006 Elsevier B.V. All rights reserved.

Effect of nose ringing and stocking rate of pregnant and lactating outdoor sows on exploratory behaviour, grass cover and nutrient loss potential

Nose ringing of outdoor sows is practiced to reduce grass sward damage for environmental reasons but conflicts with natural behaviour considerations. We investigated effects of ringing pregnant and lactating outdoor sows on foraging and explorative behaviour, grass cover and nutrient deposition. The experiment included both ringed and unringed sows. For unringed sows the paddocks were either used continuously throughout the experiment or divided into two and sows were moved half way through the experimental period leaving the first used paddock for regrowth. Ringing did not prevent the sow’s rooting, but rooting was less pronounced, when sows were ringed. On average, ringing increased grass cover from 14% to 38% and from 64% to 81% in paddocks with pregnant and lactating sows, respectively. In paddocks with unringed sows kept at a double density and followed by a resting period, the grass cover in autumn was restored to a high degree in paddocks with pregnant sows. In lactating sow paddocks the level of inorganic N was high but with no significant relation to extent of grass cover. In pregnant sow paddocks the soil inorganic N content was significantly reduced by increased grass cover and at 60% grass cover soil inorganic N content was at a low level. From the experiment it was evident that although ringing did have a positive environmental effect, it was not the main factor influencing potential losses. Management choices in terms of feeding, animal density and nutrient distribution are considered to be at least as important. D 2006 Elsevier B.V. All rights reserved.

Long-term Trends in Vegetation Dynamics and Forest Fires in Brandenburg (Germany) Under a Changing Climate

The human influence on environmental processes has been described for many types of land use. One of the oldest tools to modify people’s environment is fire, which has dominated fire regimes in many regions over long time scales. This paper focuses on a German case study region, where 80–90% of the fires are human-caused. The objectives of this study are the application of the Regional Fire Model (Reg-FIRM), a process-based fire model that is incorporated into the LPJ Dynamic Global Vegetation Model, to temperate forests under historic climate conditions and to explore ranges of potential impacts of future climate change on fire and vegetation dynamics. Simulation experiments are designed to simulate historic fire pattern and to explore influences of vegetation on fire. Simulated fire pattern reproduced the observed average fire conditions reasonably well although with a smaller amplitude. This leads to underestimation of extreme fire years as well as an overestimation of low fire years. Vegetation composition influenced fire spread conditions in the temperate forest and had little impact on fire ignition potentials, except when only broad-leaved deciduous forests were assumed. Fire is likely to change under climate change conditions. Simulated experiments were conducted to explore the effects of climate change and rising CO2 concentration given the potential natural vegetation as the best-case for Brandenburg. Three GCM scenarios predicting different future climatic changes were applied, and resulted in quantitatively different future fire patterns. Depending on future precipitation pattern and the influence of the CO2 effect on canopy conductance and thus litter moisture, fire was predicted to either decrease or slightly increase in Brandenburg forests, but the burnt area would not exceed current, extreme fire years. Generally, fire changes had no implication for vegetation composition in Brandenburg, but reduced vegetation carbon gain after 2050. In the HadCM3 application, simulated increase in grass cover due to a large burnt area after 2075 accelerated fire spread conditions, thus still increasing the burnt area, while climatic fire danger and number of fires already began to decline. These interactions underline the importance to consider the full range of fire processes and interactions with vegetation dynamics in a simulation model.

Effects of livestock removal and perennial grass recovery on the lizards of a desertified arid grassland

We sampled lizards inside and outside of a 9.3 ha livestock exclosure in a desertified arid grassland in southeastern Arizona with pitfall traps and mark-recapture. Lizard community composition was significantly different inside versus outside of the exclosure. Analysis of tail-break frequencies suggests that higher predation rates outside the exclosure may contribute to increased abundance of Sceloporus undulatus and Uta stansburiana following livestock removal and associated changes in grass cover and vegetation complexity. In contrast, Phrynosoma modestum was significantly less abundant inside the exclosure. These results indicate that lizard abundance can increase and community composition can change in desertified arid grasslands following livestock removal that results in increased grass cover and vegetation complexity.

Vegetation response of a mesquite-mixed brush community to aeration

Responses of plant communities to mechanical treatments such as aeration on semiarid rangelands are not clearly understood. Our objective was to compare woody and herbaceous plant cover, density, and diversity on aerated and nontreated rangelands. Five rangeland sites that were aerated with a double/tandem drum aerator during summer 1998 and 5 sites of nontreated rangeland were selected for study on the Chaparral Wildlife Management Area, La Salle County, Tex. Woody plant cover was estimated using the line-intercept method, and stem density was estimated in 30 × 1.5 m plots in 1999 and 2000. Forb and grass cover and density were estimated in 20 × 50 cm quadrats during spring and fall 1999. Woody and herbaceous plant diversity did not differ between treatments. On aerated sites percent woody plant cover was 4-fold less 1-year after aeration and increased 89% from the first to the second growing-season post treatment. Canopy cover of honey mesquite (Prosopis glandulosa Torr.), twisted acacia (Acacia schaffneri S. Wats.), and Texas pricklypear (Opuntia lindheimeri Engelm.) was greater on non-treated sites. By the second growing season after aeration, density of honey mesquite was greater on aerated sites, whereas Texas pricklypear had declined on aerated sites. Density of spiny hackberry (Celtis pallida Torr.) and Texas persimmon (Diospyros texana Scheele) was greater on aerated sites during the first growing-season post treatment. Cover and stem density of hog-plum (Colubrina texana T. G.), coma (Bumelia celastrina Kunth), and whitebrush [Aloysia gratissima (Gill. Hook.) Tron.] did not differ among aerated and nontreated sites by the first growing season after aeration. Forb cover was greater on aerated sites in spring 1999. Fringed signalgrass [Brachiaria ciliatissima (Buckl.) Chase], fall witchgrass [Digitaria cognata (Schult.) Pilger], and bristlegrass (Setaria spp. Beauv.) cover was greater on aerated sites in spring and fall 1999, whereas purple threeawn (Aristida purpurea Nutt.) was greater on nontreated sites. It is unclear to what degree environmental factors such as pre- and post-treatment climatic conditions and herbivory may have influenced vegetation response to aeration. The rapid regrowth of many woody plants following aeration may require the application of maintenance treatments within a relatively short time period to maintain treatment benefits. Aeration reduced total woody plant cover, increased the density of desirable woody plants, maintained woody plant diversity, increased grass cover, and may be a useful tool in managing South Texas rangelands for white-tailed deer (Odocoileus virginianus Boddaert) and cattle.

Timescale of Perennial Grass Recovery in Desertified Arid Grasslands Following Livestock Removal

Abstract: Over the past two centuries, perennial grass cover has declined and shrub density has increased in many arid grasslands. These changes in vegetation, characteristic of desertification, are thought to have occurred often following prolonged periods of intense grazing by domestic livestock. At many such sites, however, the subsequent removal of livestock grazing for up to 20 years has not resulted in increased grass cover. The apparent stability of vegetation following the cessation of livestock grazing has led to the hypothesis that desertified arid grasslands exist in alternate stable states of either grassland or shrubland over timescales relevant to management. To better understand the timescale of grass recovery in historic arid grasslands dominated by shrubs, we examined the vegetation at two nearby desertified sites that differed in the length of time since livestock removal. There was little difference between the site ungrazed for 20 years and the shrub‐dominated vegetation on the other side of the exclusion fence. At a site ungrazed for 39 years there was significantly higher perennial grass cover inside the exclusion fence than outside, and nearly all the increase had occurred over the past 20 years. These data suggest that there may be time lags of 20 years or more in the response of perennial grasses to removal of livestock in historic grassland ecosystems dominated by shrubs.

Restoring Degraded Riparian Meadows: Biomass and Species Responses

Riparian meadows in central Nevada are highly productive and have been extensively utilized for livestock grazing. Consequently, many have been severely degraded resulting in changes in species composition and decreases in productivity. During a 3 year study, we examined the responses of mesic meadow systems to yearly nitrogen addition (100 kg ha(-1)) and clipping (8-10 cm stubble height) to increase our understanding of grazing effects. We also examined the effects of a one-time, fall aeration (10 cm deep by 2 cm wide holes spaced 20 cm apart) and revegetation (removal of existing vegetation and reseeding) to evaluate the restoration potential of these sites. Changes in total biomass, species aerial cover and frequency, and surface basal cover were used to evaluate treatment responses. Clipping had no effect on total biomass, possibly because it was conducted late in the growing season. In contrast, nitrogen addition plus clipping increased biomass in all 3 years when treatments were compared across sites and for 1 out of 3 years when treatments were compared across a single site. Aeration had no effect on above ground biomass, but has been shown to increase rooting activity in these same meadows. Due to a dry, hot spring, early seral and weedy species had higher establishment than the seeded natives in the revegetation plots, and biomass was low the first year after treatment. Individual species varied in their treatment responses. The cover of low-growing forb species (western aster (Aster occidentalis [Nutt.] Torrey and A. Gray), long-stalk starwort (Stellania Longipes Goldie), and common dandelion (Taraxacum officinale Wigg.) declined through time for all treatments, presumably due to increased grass cover and shading following release from grazing and above average precipitation and water table levels in 1998. Examination of the key graminoids showed that Kentucky bluegrass (Poa pratensis ssp. pratensis L.), an increaser species, did not increase in response to release from grazing, but increased in response to clipping and nitrogen addition. Nebraska sedge (Carex nebrascensis Dewey), a desirable native, increased in response to both release from grazing and nitrogen addition. The results were influenced by high spatial and temporal variability in water table elevations within these systems. DOI:10.2458/azu_jrm_v54i3_martin

Restoring degraded riparian meadows: Biomass and species responses

Riparian meadows in central Nevada are highly productive and have been extensively utilized for livestock grazing. Consequently, many have been severely degraded resulting in changes in species composition and decreases in productivity. During a 3 year study, we examined the responses of mesic meadow systems to yearly nitrogen addition (100 kg ha(-1)) and clipping (8-10 cm stubble height) to increase our understanding of grazing effects. We also examined the effects of a one-time, fall aeration (10 cm deep by 2 cm wide holes spaced 20 cm apart) and revegetation (removal of existing vegetation and reseeding) to evaluate the restoration potential of these sites. Changes in total biomass, species aerial cover and frequency, and surface basal cover were used to evaluate treatment responses. Clipping had no effect on total biomass, possibly because it was conducted late in the growing season. In contrast, nitrogen addition plus clipping increased biomass in all 3 years when treatments were compared across sites and for 1 out of 3 years when treatments were compared across a single site. Aeration had no effect on above ground biomass, but has been shown to increase rooting activity in these same meadows. Due to a dry, hot spring, early seral and weedy species had higher establishment than the seeded natives in the revegetation plots, and biomass was low the first year after treatment. Individual species varied in their treatment responses. The cover of low-growing forb species (western aster (Aster occidentalis [Nutt.] Torrey and A. Gray), long-stalk starwort (Stellania Longipes Goldie), and common dandelion (Taraxacum officinale Wigg.) declined through time for all treatments, presumably due to increased grass cover and shading following release from grazing and above average precipitation and water table levels in 1998. Examination of the key graminoids showed that Kentucky bluegrass (Poa pratensis ssp. pratensis L.), an increaser species, did not increase in response to release from grazing, but increased in response to clipping and nitrogen addition. Nebraska sedge (Carex nebrascensis Dewey), a desirable native, increased in response to both release from grazing and nitrogen addition. The results were influenced by high spatial and temporal variability in water table elevations within these systems.

Regeneration patterns in a Central European dry heathland: effects of burning, sod-cutting and cutting

Vegetation development in dry heathlands was studied during a six-year period following experimental burning, sod-cutting and cutting in a continental area in the southern part of the Czech Republic (Podyji National Park). Calluna vulgaris-dominated heathlands in the area were composed of uneven-aged stands and had been unmanaged for several decades. The aim of the study was testing the applicability of Western European management systems to nature conservation in a continental area. Species composition was recorded in 8 permanent plots using 25 x 25 cm grids, and vegetation recovery following different treatments was analysed. Calluna recovered successfully after burning. Burning dense heathlands, which contained a large amount of woody fuel, resulted in a medium-intensity fire that destroyed moss mats and litter and exposed patches of bare ground to facilitate Calluna regeneration by seed, in addition to vegetative regrowth. On the contrary, in open heathlands with patches of herbaceous vegetation, low-intensity fires which failed to expose mineral soil were more typical. Almost all Calluna regeneration was vegetative in this case, and regrowth was slower. Heathland recovery after sod-cutting to mineral soil depended on whether or not Calluna seed germination occurred in the plot. With germination, the community developed towards heathland; without towards grassland. Cutting promoted a striking increase in grass cover, which was followed by the slow recovery of Calluna. The experiments suggest that of these management systems, burning is perhaps the most appropriate in the study area. A nature conservation management system is proposed, based on sheep grazing combined with rotational burning of restricted patches.

Desertification of the eastern Karoo, South Africa: Conflicting paleoecological, historical, and soil isotopic evidence

The desertification debate in South Africa has benefitted greatly in recent years from the contributions of a wide range of disciplines. In this paper we review the conflicting and supporting evidence for degradation in the eastern Karoo as reported in recent archaeological, historical, and stable carbon isotope studies as it relates to three key aspects of the debate: the precolonial environment, the rate and nature of change, and the relative contributions of humans and climate to the process. First, all studies suggest a greater grassiness at some time in the past, but researchers disagree on the timing of the switch to more shrubby conditions in the eastern Karoo. Second, regional rainfall records for the past 2 decades reveal an above-average rainfall period, and numerous long-term surveys show an increase in grass cover over the same period. These findings question the expanding Karoo hypothesis as well as the argument that the Karoo's carrying capacity has decreased in recent years. Finally, the relative responsibilities of humans and climate in the degradation process remain poorly understood and generally have not formed the focus of investigation.

Effects of kangaroo rat exclusion on vegetation structure and plant species diversity in the Chihuahuan Desert.

Long-term (1977-90) experimental exclusion of three species of kangaroo rats from study plots in the Chihuahuan Desert resulted in significant increases in abundance of a tall annual grass (Aristida adscensionis) and a perennial bunch grass (Eragrostis lehmanniana). This change in the vegetative cover affected use of these plots by several other rodent species and by foraging birds. The mechanism producing this change probably involves a combination of decreased soil disturbance and reduced predation on large-sized seeds when kangaroo rats are absent. Species diversity of summer annual dicots was greater on plots where kangaroo rats were present, as predicted by keystone predator models. However, it is not clear whether this was caused directly by activities of the kangaroo rats or indirectly as a consequence of the increase in grass cover. No experimental effect on species diversity of winter annual dicots was detected. Our study site was located in a natural transition between desert scrub and grassland, where abiotic conditions and the effects of organisms may be particularly influential in determining the structure and composition of vegetation. Under these conditions kangaroo rats have a dramatic effect on plant cover and species composition.

Response of Yankeeweed (Eupatorium compositifolium) and Associated Pasture Plants to Herbicides

Eleven herbicides applied in May, were evaluated for yankeeweed control in East-Central Texas. Yankeeweed cover 1 yr later was reduced to 5% or less by 0.28 kg ha-1 of picloram; 0.56 kg ha-1 of clopyralid, glyphosate, or dicamba; 0.28 + 0.84 kg ha-1 of dicamba + 2,4-D, and 1.1 kg ha-1 triclopyr compared with 30% cover in the untreated area. Chlorsulfuron and metsulfuron at 0.07 kg ha-1 reduced yankeeweed cover to 12 and 7%, respectively. Dalapon, 2,4-D, and tebuthiuron were relatively ineffective. Most herbicides, reduced woolly croton cover within 1 mo after treatment compared to the untreated areas, but 2,4-D at 0.28 kg ha-1 and chlorsulfuron at 0.02 kg ha-1 and 0.07 kg ha-1 were most effective after 4 mo. All herbicides, except dalapon at 1.1 kg ha-1 or less and most rates of 2,4-D and tebuthiuron, reduced partridgepea cover during the year of application. Total grass cover was increased 4 and 12 mo following treatment with clopyralid, picloram, dicamba, and triclopyr. On separate sites, bahiagrass and coastal bermudagrass accounted for most of the increased grass cover.

Comparative foraging adaptations of small raptors in a dense African savanna

Our aim was to investigate how ecologically similar species with different evolutionary adaptations may coexist in a moist Guinean savanna, which is the optimal habitat of the Lizard Buzzard Kaupifalco monogrammicus whereas the Grey Kestrel Falco ardosiaceus and the Grasshopper Buzzard Butastur rufipennis are of more Sudanian origin. Activity budgets, foraging behaviour and success were assessed by focal sampling and were related to habitat parameters and prey availability. Each species had its own daily foraging pattern which seemed to be related to the activity patterns of their main prey, grasshoppers or lizards. Interspecific habitat segregation reflected their morphological and behavioural adaptations and their respective tolerance to grass height, the most important factor in habitat selection. The resident Lizard Buzzard selected the densest woodlands, whereas the Grey Kestrel was restricted to the most open areas and the dry season migrant Grasshopper Buzzard to intermediate, recently burnt, savanna types. The main foraging variables (perch height, inter‐perch distance and frequency of moves) differed significantly between species. Maximum detection distances increased with perch height but decreased with increasing grass cover. Perch height was lower when the grass became too high. When attack rates increased, birds tended to move more often, but for shorter distances, and stayed longer within restricted patches. The highly insectivorous Grasshopper Buzzard had the highest and least variable attack rates, negatively correlated with grass height. It exhibited a behaviour typical of a migrant—superficial and opportunistic exploitation of superabundant, easily accessible, and seasonal food sources. Conversely, the residents were associated with denser, more stable habitats and larger, less abundant, but more predictable prey.

The effects of fertilization on part of the Keen of Hamar Serpentine, Shetland

Summary Winter feeding of stock has caused eutrophication of the lower part of the Keen of Hamar. A nutrient addition experiment is reported which shows that grass cover of the serpentine debris increased greatly following phosphorus fertilization. Long-term observations have shown a substantial increase in grass cover over c. 35% of the lower part of the Keen and in one limited area the complete elimination of a rare species. It is suggested that the effects of eutrophication are likely to persist indefinitely and that it poses a major threat to this habitat and its rare plant species, although it seems that the site could be restored by removal of newly accumulated soil.