Ha Of Grassland Research Articles

The Location and Extent of Systematic Drainage in Relation to Land Use in the Past and at Present and in Relation to Soil Vulnerability to Accelerater Infiltration in the Protected Landscape Area Železné Hory

This study searched for associations between the extent of hydromelioration systems and the land use (in the past and at present), degree of nature conservation, and infiltration of water through soil profile in the Protected Landscape Area (PLA) Železné hory. According to the available evidence, 34.6% of arable land and 32.1% of permanent grasslands in this area are drained by the drainage systems. Analysis of the original design documentations of drainage structures indicate, that the extent of drained areas can actually be even higher. The hydromelioration systems were built namely in the second half of the 20th century. The drainage also affected alluvial meadows, wetlands, and ecologically valuable stations. After establishment of PLA Železné hory in 1991, the protected area was divided into four zones according to their significance and protection regime. This study has revealed the presence of areas drained by systematic drainage systems (101 ha of grasslands) even in the zones of highest landscape protection degree (1st and 2nd protection zones). The inadequately executed drainage systems should be eliminated and the character of the land should be brought closer to its natural conditions. On the model part of the PLA we also performed a study of historical changes in the landscape in three time horizons (1839, 1950, 2014) to show differences in land use before building of drainage, at the time of building, and at present.

An Integrated Strategy for Grassland Easement Acquisition in the Prairie Pothole Region, USA

Abstract Acquisition of perpetual grassland easements is a principal tactic used by the United States Fish and Wildlife Service (USFWS) and its partners to protect nesting habitat for migratory birds in the Prairie Pothole Region of North and South Dakota, USA. This public–private partnership resulted in the conservation of >344,000 ha of grassland during 1998–2012. Past easement acquisition has been targeted to landscapes with greatest expected accessibility to breeding duck pairs without active consideration of probability of conversion or cost of protection. The rising cost of easement acquisition in recent years indicates that re-evaluation and refinement of the easement acquisition strategy could help to improve programmatic outcomes. We assessed regional patterns of easement acquisition during 1998–2012, evaluated the current targeting strategy, and used a combination of publicly available and proprietary geospatial data to develop an easement-targeting Geographic Information System that integrated information about conversion probability and protection cost with current targeting criteria. Our assessment indicated that grassland protection was negatively affected by rising land prices during 1998–2012. In the 5 y between 2008 and 2012, about 100,000 ha of grassland were protected at a cost of $83 million (U.S. dollars). The 2008–2012 acquisitions represented 30% of total protection during 1998–2012 but composed 47% of the total expenditure. We observed strong evidence that easements were targeted to priority landscapes both before and after formalization of the USFWS conservation strategy in 2004. We also found evidence of an opportunity to increase efficiency of future acquisitions. We identified 0.9 million ha of currently unprotected priority grassland in the region with greater than expected conversion risk and smaller than expected protection cost. We suggest that future grassland easement acquisition be refocused on this refined priority area and that an adaptive approach to future easement acquisition (including targeted acquisitions, directed monitoring, and data-based decisions) provides a logical framework for implementation of this new strategy and will facilitate continued conservation success.

Which is the preferable biogas utilisation technology for anaerobic digestion of agricultural crops in Ireland: Biogas to CHP or biomethane as a transport fuel?

The utilisation of anaerobic digestion to produce biogas as an energy source is a mature technology in many European countries but is yet to be developed in Ireland. In 2009, the EU issued the Renewable Energy Source Directive 2009/28/EC which requires a 20% share of renewable energy sources (heat and electricity) in final energy consumption for all member states, respectively, including a 10% share of biofuels in the transport sector by 2020. The introduction of biogas to produce power and electricity in the form of CHP technology and biomethane as a transport fuel can help Ireland achieve the mandatory targets set by the directive. The key focus of the paper is to determine the optimum small to medium scale biogas technology and the impact the introduction of that technology infrastructure will have on renewable energy targets for Ireland. In terms of feedstock, agricultural sources such as energy crops and slurry offer a sustainable input to the anaerobic digestion process. The crop rotations under consideration consist of different arrangements of grass silage, maize silage and barley. Grass silage is found to be the most suitable crop for biogas energy production while biogas upgrading to biomethane as a transport fuel has the optimum technology potential in Ireland. To fuel a car operating on biomethane, 0.22 ha of grass land is required annually. Full scale national development of 5% of the area under grass in Ireland will contribute 11.4% of renewable energy to the total final transport energy demand by 2020, surpassing the target set by the Renewable Energy Source Directive 2009/28/EC.

Competing use of organic resources, village-level interactions between farm types and climate variability in a communal area of NE Zimbabwe

In communal areas of NE Zimbabwe, feed resources are collectively managed, with herds grazing on grasslands during the rainy season and mainly on crop residues during the dry season, which creates interactions between farmers and competition for organic resources. Addition of crop residues or animal manure is needed to sustain agricultural production on inherently poor soils. Objectives of this study were to assess the effect of village-level interactions on carbon and nutrient flows, and to explore their impact on the long-term productivity of different farm types under climate variability. Crop and cattle management data collected in Murewa Communal area, NE Zimbabwe was used together with a dynamic farm-scale simulation model (NUANCES-FARMSIM) to simulate village-level interactions. Simulations showed that grasslands support most cattle feed intake (c. 75%), and that crop residues produced by non-cattle farmers sustain about 30% of the dry season feed intake. Removal of crop residues (0.3–0.4 t C ha −1 yr −1) from fields of non-cattle farmers resulted in a long-term decrease in crop yields. No-access to crop residues of non-cattle farmers increased soil C modestly and improved yields in the long-term, but not enough to meet household energy requirements. Harvest of grain and removal of most crop residues by grazing cattle caused a long-term decline in soil C stocks for all farm types. The smallest decrease (−0.5 t C ha −1) was observed for most fertile fields of cattle farmers, who manure their fields. Cattle farmers needed to access 4–10 ha of grassland to apply 3 t of manure ha −1 yr −1. Rainfall variability intensifies crop–livestock interactions increasing competition for biomass to feed livestock (short-term effect) or to rehabilitate soils (long-term effect). Prolonged dry seasons and low availability of crop residues may lead to cattle losses, with negative impact in turn on availability of draught power, affecting area under cultivation in consecutive seasons until farmers re-stock. Increasing mineral fertiliser use concurrently with keeping crop residues in fertile fields and allocating manure to poor fields appears to be a promising strategy to boost crop and cattle productivity at village level. The likelihood of this scenario being implemented depends on availability of fertilisers and decision of farmers to invest in rehabilitating soils to obtain benefits in the long-term. Adaptation options cannot be blind to what occurs beyond field and farm level, because otherwise recommendations from research and development do not fit the local conditions and farmers tend to ignore them.

Quantifying nitrous oxide emissions from Chinese grasslands with a process-based model

Abstract. As one of the largest land cover types, grassland can potentially play an important role in the ecosystem services of natural resources in China. Nitrous oxide (N2O) is a major greenhouse gas emitted from grasslands. Current N2O inventory at a regional or national level in China relies on the emission factor method, which is based on limited measurements. To improve the accuracy of the inventory by capturing the spatial variability of N2O emissions under the diverse climate, soil and management conditions across China, we adopted an approach by utilizing a process-based biogeochemical model, DeNitrification-DeComposition (DNDC), to quantify N2O emissions from Chinese grasslands. In the present study, DNDC was tested against datasets of N2O fluxes measured at eight grassland sites in China with encouraging results. The validated DNDC was then linked to a GIS database holding spatially differentiated information of climate, soil, vegetation and management at county-level for all the grasslands in the country. Daily weather data for 2000–2007 from 670 meteorological stations across the entire domain were employed to serve the simulations. The modelled results on a national scale showed a clear geographic pattern of N2O emissions. A high-emission strip showed up stretching from northeast to central China, which is consistent with the eastern boundary between the temperate grassland region and the major agricultural regions of China. The grasslands in the western mountain regions, however, emitted much less N2O. The regionally averaged rates of N2O emissions were 0.26, 0.14 and 0.38 kg nitrogen (N) ha−1 y−1 for the temperate, montane and tropical/subtropical grasslands, respectively. The annual mean N2O emission from the total 337 million ha of grasslands in China was 76.5 ± 12.8 Gg N for the simulated years.

Mapping oil and gas development potential in the US Intermountain West and estimating impacts to species.

BackgroundMany studies have quantified the indirect effect of hydrocarbon-based economies on climate change and biodiversity, concluding that a significant proportion of species will be threatened with extinction. However, few studies have measured the direct effect of new energy production infrastructure on species persistence.Methodology/Principal FindingsWe propose a systematic way to forecast patterns of future energy development and calculate impacts to species using spatially-explicit predictive modeling techniques to estimate oil and gas potential and create development build-out scenarios by seeding the landscape with oil and gas wells based on underlying potential. We illustrate our approach for the greater sage-grouse (Centrocercus urophasianus) in the western US and translate the build-out scenarios into estimated impacts on sage-grouse. We project that future oil and gas development will cause a 7–19 percent decline from 2007 sage-grouse lek population counts and impact 3.7 million ha of sagebrush shrublands and 1.1 million ha of grasslands in the study area.Conclusions/SignificanceMaps of where oil and gas development is anticipated in the US Intermountain West can be used by decision-makers intent on minimizing impacts to sage-grouse. This analysis also provides a general framework for using predictive models and build-out scenarios to anticipate impacts to species. These predictive models and build-out scenarios allow tradeoffs to be considered between species conservation and energy development prior to implementation.

Field trials of Metarhizium anisopliae var. acridum (Ascomycota: Hypocreales) against oriental migratory locusts, Locusta migratoria manilensis (Meyen) in Northern China

During 2002–2006, nymph bands of Locusta migratoria manilensis (Meyen) were treated by ground and aerial applications in 6000 ha of grasslands and the nearby beach of Yellow river using a soybean oil miscible suspension ULV formulation of Metarhizium anisopliae var. acridum isolate CQMa102. The formulation was also applied in Tianjin, Henan, Hebei, Shandong and Shanxi provinces of Northern China by ground and aerial applications. During field studies, cage tests were carried out in corresponding field plots in order to estimate the mortality accurately. Doses of 3.3×10 12 and 5.0×10 12 conidia ha −1 were equally effective and caused 90% mortality 9–13 days after treatment. In the ground spray trial, 3.3×10 12 conidia ha −1 killed >90% of L. migratoria manilensis 11–15 days after treatment in a wide variety of vegetation and weather conditions. The decline of locust populations was slower where vegetation was taller and denser. In the aerial spray treatment, the final percent survival of locusts was lowered to 10% at 11 and 14 days in the field cage and open field locusts, respectively. Furthermore, the M. anisopliae oil miscible suspension formulation did not appear to harm natural enemies of locusts in the field.

Evidence for a Recent Henslow's Sparrow Population Increase in Illinois

Abstract: The Henslow's sparrow (Ammodramus henslowii) is a species of high conservation concern due to long‐term population declines and a small global population. Habitat loss is considered to be the most likely cause of Henslow's sparrow declines and the recent establishment of large acreages of undisturbed grasslands through the Conservation Reserve Program is considered to have the potential to benefit populations. I used data from Illinois' Spring Bird Count to estimate recent population trends and examine the association that changes in land‐use, especially the establishment of Conservation Reserve Program lands, have had on local Henslow's sparrow population trends. My analysis shows that Henslow's sparrow populations have increased substantially within Illinois, USA over the last 10 years and that this population increase strongly coincides with the establishment of >400,000 ha of grasslands within the state by the Conservation Reserve Program. New rules allowing for managed haying and grazing on Conservation Reserve Program grasslands have the potential to reduce the suitability of program fields for this species and, thus, Henslow's sparrow use of program fields should be monitored as the new rules are implemented.

EFFECTS OF MOWING AND BURNING ON SHRUBLAND AND GRASSLAND BIRDS ON NANTUCKET ISLAND, MASSACHUSETTS

Abstract Throughout the United States, declines in breeding populations of grassland and shrubland birds have prompted conservation agencies and organizations to manage and restore early-successional habitats. These habitats support a variety of birds, some of which have been classified as generalists; thus, often these birds are thought to be less affected by habitat manipulation. More information, however, is needed on the response of early-successional generalists to habitat management, because conservation agencies are increasing their focus on the regional preservation and management of common species. On Nantucket Island, Massachusetts, the goal of the Partnership for Harrier Habitat Preservation (PHHP) has been to restore more than 373 ha of grassland for the island's population of Northern Harriers (Circus cyaneus). This management program has entailed methods such as prescribed burning and mowing (e.g., brushcutting) to restore and maintain grassland habitat. Over a 3-year period, we found that s...

Mapping the Habitat Quality of Patch Networks for the Marsh Fritillary Euphydryas aurinia (Rottemburg, 1775) (Lepidoptera, Nymphalidae) in Wales

The marsh fritillary is widely distributed in Wales, with over 200 populations identified in the past 15 years. However, agricultural improvement, habitat fragmentation and changes in agricultural practices continue to impact on status and a decline in range of 23.5% was recorded over a 10-year period. Solutions must be applied at the landscape scale to improve metapopulation viability and, since 2000, surveys of habitat extent and quality have been carried out on 116,373 ha of grassland surrounding 111 populations. Analysis of the results for standard ‘core landscapes’ (based on circles of 1 km radius around known populations) shows that overall cover of suitable breeding habitat is 3.44%. However, only 11.85% of the grassland that was suitable for marsh fritillaries was classified as being in Good Condition. The remainder was regarded as having sub-optimal vegetation structure and/or the foodplant was at low density; 33% of the habitat resource that was not in Good Condition was regarded as inappropriately or excessively managed and 67% was suffering from neglect. An Index of Landscape Quality is used to rank landscapes for evaluation. Thirty-five ‘core landscapes’ (incorporating 98 marsh fritillary populations) were assessed and just four exceeded a threshold value deemed to represent viable landscape configurations. The results have demonstrated that most marsh fritillary populations in Wales exist within depauperate patch networks that lack sufficient breeding habitat of the right quality for long-term persistence. Without targeted conservation action the marsh fritillary will continue to decline in Wales. This paper reports on efforts to collect information on the quality of breeding habitat for marsh fritillaries across Wales in order to identify priorities for conservation action.

Private-land habitat opportunities for prairie grouse through federal conservation programs

Habitat alterations have resulted in significant declines in the populations of prairie grouse (Centrocercus minimus, C. urophasianus, Tympanuchus cupido, T. pallidicinctus, T. phasianellus) throughout the last century. Landscape-level habitat restoration through federal conservation programs may be the only option available to prevent several of these species from declining to dangerously low levels. I examined 7 federal conservation programs available through the United States Department of Agriculture (USDA) and 5 programs through the United States Fish and Wildlife Service (USFWS) to determine how they might be used to restore and protect habitat for prairie grouse on private land. The USDA's Conservation Reserve Program (CRP) has restored ≥15 million ha of grassland with cost-share agreements and 10-year contracts. The Environmental Quality Incentives Program (EQIP) has the potential to restore habitat for prairie grouse because it is well funded and primarily focused on improving livestock operations on grasslands, much of which occurs on native prairies. Other USDA conservation programs provide the necessary funding and incentives to landowners to protect and restore prairie grouse habitat, but competition among states for available funds and authorized practices may reduce their effectiveness at restoring habitat over large landscapes. The USFWS Grassland Easement Program, Partners for Fish and Wildlife Program, and Private Stewardship Grants Program collectively have restored and protected ≥300,000 ha of grassland and native prairie with perpetual easements, cost-share agreements, technical assistance, and term contracts. Much of the vegetation provided by these programs should be of significant value for prairie grouse habitat. The USFWS State and Tribal Wildlife Grants Program and the Landowner Incentive Program should enable the states to develop their own programs to restore and protect prairie grouse habitat on private land.

Landscape-level dynamics of grassland-forest transitions in British Columbia

Grasslands in the interior British Columbia of Canada are adjacent to forests and are susceptible to tree encroachment. Grazing, fire suppression, and climate variability are among factors affecting vegetation dynamics in the ecotone between grassland and forest, but topographic factors such as slope aspect, slope degree and elevation may interact with these factors and result in uneven changes in vegetation among landscape elements. Nine sites with a total of approximately 50,000 ha of grasslands and forests in the Cariboo/Chilcotin forest region of British Columbia were selected to study the effect of slope aspect, slope degree and elevation on vegetation distribution, dynamics and forest expansion from the 1960's to 1990's. Vegetation maps of the 1960's and 1990's were generated using aerial photos and overlaid with GIS layers including aspect, slope and elevation. The classification of open grassland, treed grassland, open forest and closed forest was based on the percent coverage of coniferous species, ranging from 0-5%, 5-15%, 15-35%, and ≥ 35%, respectively. A probability index (P-value) was developed to test the effect of aspect, slope, and elevation on vegetation distribution, dynamics, and forest expansion based on the distribution and changed areas. Results show that open grasslands occurred on southerly aspects and the shift to treed grassland occurred mostly on these aspects. The probability of vegetation shift from open to treed grasslands decreased with increasing slope degree, probably due to the less favorable moisture regime on steep slopes. Treed grassland also shifted to open forest on south facing slopes and more level sites. In contrast, closed forest most often occurred on northerly facing slopes and the shift from open to closed forests was most likely to occur there. The greatest changes in vegetation cover types occurred at mid-elevations between 700 and 1,000 m. Management plans aimed at the control of tree encroachment and forest ingrowth should take these topographic factors into consideration.

Landscape-level dynamics of grassland-forest transitions in British Columbia

Grasslands in the interior British Columbia of Canada are adjacent to forests and are susceptible to tree encroachment. Grazing, fire suppression, and climate variability are among factors affecting vegetation dynamics in the ecotone between grassland and forest, but topographic factors such as slope aspect, slope degree and elevation may interact with these factors and result in uneven changes in vegetation among landscape elements. Nine sites with a total of approximately 50,000 ha of grasslands and forests in the Cariboo/Chilcotin forest region of British Columbia were selected to study the effect of slope aspect, slope degree and elevation on vegetation distribution, dynamics and forest expansion from the 1960's to 1990's. Vegetation maps of the 1960's and 1990's were generated using aerial photos and overlaid with GIS layers including aspect, slope and elevation. The classification of open grassland, treed grassland, open forest and closed forest was based on the percent coverage of coniferous species, ranging from 0–5%, 5–15%, 15–35%, and ≥ 35%, respectively. A probability index (P-value) was developed to test the effect of aspect, slope, and elevation on vegetation distribution, dynamics, and forest expansion based on the distribution and changed areas. Results show that open grasslands occurred on southerly aspects and the shift to treed grassland occurred mostly on these aspects. The probability of vegetation shift from open to treed grasslands decreased with increasing slope degree, probably due to the less favorable moisture regime on steep slopes. Treed grassland also shifted to open forest on south facing slopes and more level sites. In contrast, closed forest most often occurred on northerly facing slopes and the shift from open to closed forests was most likely to occur there. The greatest changes in vegetation cover types occurred at mid-elevations between 700 and 1,000 m. Management plans aimed at the control of tree encroachment and forest ingrowth should take these topographic factors into consideration.

1986 survey of upland grassland in England and Wales: changes in age structure and botanical composition since 1970–72 in relation to grassland management and physical features

AbstractA sample of 10000 ha of grassland in seven upland districts originally surveyed in 1970–72 was re‐surveyed in 1986. Forty percent of the area was above 240 m elevation, 38% had gradients above 81/2°, 29% had poor or bad drainage and 54% was classified as having difficult or severe limitations to management. Twelve percent had been reseeded within the previous 5 years and 39% within 20 years; 6% was classified as arable grassland (in rotation with crops). Thirty‐four percent was usually mown, two‐thirds of it for silage. In most years 72% of grassland received fertilizer N (average application 123 kg N ha−1) and 35% received organic manure; nearly 20% received neither. Older swards tended to receive lower rates of fertilizer N than reseeds, hay fields and grazed fields less than silage fields, and fields on beef/sheep farms less than those on dairy farms. The proportion of sown species in swards averaged 35%, of which Lolium perenne accounted for 23%. A good contribution of Trifolium repens was recorded in 15% of the grassland. Herb species were recorded in 30% of the grassland, mostly in situations with low fertilizer N under hay or grazing. Agrostis spp., Poa spp., Holcus lanatus and Festuca rubra were the main unsown grasses. The average contribution of L. perenne had increased since 1970–72; it was also present in two‐thirds of the area from which it was absent in 1970–72, whilst the contribution of T. repens had decreased. The incidence of Cirsium arvense and Ranunculus spp. had also decreased, whilst that of Pteridium aquilinum had increased.

A review of the impact and control of creeping thistle ( Cirsium arvense L.) in grassland

Creeping thistle infests about 1 million ha of grassland in England and Wales, impairing grass growth and animal grazing. Its complex rooting system makes cultural control difficult to achieve. Even with chemicals like MCPA and dicamba, the extensive root system makes repeat spraying essential. Improved chemical control has been obtained using mixtures of bentazone, clopyralid and triclopyr. Progress has been made in smearing translocated herbicides on to tall-growing thistles. Interest is now centering on alternative and integrated control techniques: preliminary results indicate that combining a rust pathogen with low-dose 2,4-D may achieve successful control.

Burning in a Bunchgrass/Sagebrush Community: The Southern Interior of B.C. and Northwestern U.S. Compared

Burning in a Bunchgrass/Sagebrush Community: The Southern Interior of B.C. and Northwestern U.S. Compared

The annual leatheijacket survey in Northern Ireland, 1965–82, and some factors affecting populations

An annual leatherjacket survey was made each winter in Northern Ireland from 1965 to 1982. Over this period the mean population was 520,130/ha and showed less annual variation than in some parts of Britain. This appears to be due to the regulation of populations by rainfall in July, August and November rather than in September and October as has been shown elsewhere.It is concluded that in Northern Ireland 18,096 ha of grassland would benefit from an insecticide treatment each year. Grassland with leatheijacket populations of 1 × 106/ha or more may suffer damage and up to 100,000 ha are at risk each year. Leatherjackets are therefore considered to be serious pests of grassland in Northern Ireland.

Growth and Phenological Development of Rough Fescue in Interior British Columbia

Growth and phenological development of rough fescue (Festuca scabrella) in interior British Columbia have been documented for a 3-year period. The plants began growing around mid-April and normally ceased growing in late June. Culm growth began in late May and ceased at approximately the time leaf growth ceased. However, leaf and culm elongation ceased before the plants reached their full weight. Rough fescue headed out between May 14 and June 10 and seed shattering occurred between July 13 and July 24. Seed head production per plant was variable from year to year. Fall regrowth occurred in September one year, in October another year, and not at all the other year. Rough fescue (Festuca scabrella) is an important forage species on 1,275,OOO ha of grasslands in interior British Columbia, providing up to 10% of the dry matter yield of the Agropyron-Poa or middle grasslands zone and up to 50% of the dry matter yield of the Agropyron-Festuca or upper grasslands zone (Tisdale 1947). Rough fescue requires a mesic environment and is therefore most abundant on north and east facing slopes. As rough fescue is a palatable forage and has an extensive fibrous root system for holding soil, it may be advisable to manage it as the key species when it makes up more than 15% of the total plant composition (Hodgkinson and Young 1973). Traditionally the middle and upper grasslands of interior British Columbia have been utilized for spring and fall grazing. To help resource managers make the best use of these rough fescue ranges, we have conducted experiments to document the growth characteristics and the resistance to herbage removal of rough fescue. In this paper we describe the pattern of vegetative and reproductive growth of rough fescue at two sites of interior British Columbia. Possible relationships between growth and environmental parameters are also considered.

WINTER FEEDING ECOLOGY OF WIGEON ANAS PENELOPE AT THE OUSE WASHES, ENGLAND

SummaryInvestigations on the feeding ecology of Wigeon were carried out in winter 1978–79 at the species' most important inland wintering habitat in Britain. The study area included 287 ha of grassland, about one‐sixth of the Washes, which is grazed by cattle and sheep until late autumn. In winter the area is partly or fully flooded. The number of Wigeon increased to 11 200 in January but cold weather in February, with snow and frozen flood water, forced the birds to leave, only 600 staying in the reserve. In March up to 4000 birds were again present.The distribution of the population within the refuge depends on whether the habitat is dry pasture with only a few ponds, partly flooded, fully flooded or covered with snow and frozen flood water. Under dry or slightly wet conditions 98% of the Wigeon were grazing (October to January), while under partly flooded conditions (February and March) 42%, fed on water. With increasing water depth, upending was used by 13%, while 45% of the population moved to the barrier banks, grazing there in March. The feeding method can change within a few hours with increasing water depth.The diurnal activity pattern varies during the wintering period. A lower percentage of morning feeding occurred after flights back from feeding outside the refuge and under frozen conditions. The feeding activity was higher at mid‐day with a slight decrease towards dusk. The average diurnal feeding activity was 71% (October to April), with a maximum of 90% in November.Wigeon feed diurnally and nocturnally. During a 24 h period in March they were foraging for 15 h 40 min; by day 81% of the time was spent feeding, while at night only 48%.Standing crop measurements showed that the biomass of green vegetation declined significantly outside enclosures due to Wigeon usage. Pasture land should be grazed at different intensities by cattle and sheep before the arrival of the ducks. Inland reserves should include such pasture together with some standing water where the birds are undisturbed. The use of inland pastures can compensate for the loss of coastal habitats.

Bird Population Responses to Converting Chaparral to Grassland and Riparian Habitats

Twenty-one years after chaparral was converted to grassland and riparian habitat in central Arizona, bird population density ranged from a high of 321 pairs per 40 ha in the riparian stringer to a low of 24 pairs per 40 ha on the grassland, compared to 103 pairs per 40 ha in the chaparral. However, the conversion of 40 ha of chaparral resulted in 38 ha of grassland and 2 ha of riparian habitat. Bird density on both areas together was 37 pairs per 40 ha. Thus although popula- tion density, species richness, and diversity were higher in the riparian area when contrasted with the chaparral, there was an overall net difference of 66 fewer pairs per 40 ha in the converted area. Birds and other vertebrates are attracted to riparian habitats throughout the Southwest (Anderson and Ohmart, 1977; Carothers et al., 1974; Stevens et al., 1977; Szaro, 1980). Because of their dense vertebrate populations, increasing importance has been placed on preserving and managing riparian habitat for wildlife (Johnson and Jones, 1977). Unfortunately, the amount and quality of these habitats has been decreasing (Davis, 1977; Ohmart et al., 1977; Engel- Wilson and Ohmart, 1978). A study was initiated in the arid Southwest to determine the effects of chaparral conversion on water yield in central Ariz- ona. After a wildfire, shrub regeneration was suppressed and a watershed con- verted to grass. As a result of this conversion in 1959, a small riparian stand has developed below the stream gauging station at the base of the converted grass area. This study was designed to assess the impact of grass conversion and riparian generation on the breeding birds of Arizona chaparral.