Unimproved Pasture Research Articles

Does grassland vegetation drive soil microbial diversity?

Does plant diversity drive soil microbial diversity in temperate, upland grasslands? Plants influence microbial activity around their roots by release of carbon and pot studies have shown an impact of different grass species on soil microbial community structure. Therefore it is tempting to answer yes. However, evidence from field studies is more complex. This evidence is reviewed at three different scales. First, studies from the plant community scale are considered that have compared soil microbial community structure in pastures of different vegetation composition, as a consequence of pasture improvement. These show fungi dominating the biomass in unimproved pastures and bacteria when lime and fertilizers have been applied. Secondly, evidence for interactions between individual grass species and soil microbes is discussed at the level of the rhizosphere, by considering both pot experiments and field studies. These have produced contrasting and inconclusive results, often due to spatial heterogeneity of soil properties and microbial communities. In particular, increased soil pH and fertility in urine patches and other nutrient cycling processes interact to increase the spatially complexity of soil microbial communities. Finally three studies which have measured microbial community structure in the rhizoplane are considered. These show that bacterial diversity is not directly related to plant diversity, although fungal diversity is. In addition, the soil fungal community has been demonstrated to have an effect upon the composition of the bacterial community. We suggest that while current vegetation influences fungal communities (particularly mycorrhizae) and litter inputs fungal saprotrophs, bacterial community structure is influenced more by the quality or composition of soil organic matter, thereby reflecting carbon inputs to the soil over decades.

Land use influences soil fungal community composition across central Victoria, south-eastern Australia

Current theory expects that fungi, on the one hand, are spatially ubiquitous but, on the other, are more susceptible than bacteria to disturbance such as land use change due to dispersal limitations. This study examined the relative importance of location and land use effects in determining soil fungal community composition in south-eastern Australia. We use terminal restriction fragment length polymorphism (T-RFLP; primer pair ITS1-F–ITS4) and multivariate statistical methods (NMDS ordinations, ANOSIM tests) to compare relative similarities of soil fungal communities from nine sites encompassing three locations (ca 50–200 km apart) and four land uses (native eucalypt forest, Pinus radiata plantation, Eucalyptus globulus plantation, and unimproved pasture). Location effects were generally weak (e.g. ANOSIM test statistic R ≤ 0.49) and were, in part, attributed to minor differences in soil texture. By contrast, we found clear and consistent evidence of land use effects on soil fungal community composition ( R ≤ 0.95). That is, soils from sites of the same land use grouped together in NMDS ordinations of fungal composition despite geographic separations of up to ca 175 km (native eucalypt forests) and 215 km ( P. radiata plantations). In addition, different land uses from the same location were clearly separate in NMDS ordinations, despite, in one case, being just 180 m apart and having similar land use histories (i.e. P. radiata versus E. globulus plantation both established on pasture in the previous decade). Given negligible management of all sites beyond the early establishment phase, we attribute much of the land use effects to changes in dominant plant species based on consistent evidence elsewhere of strong specificity in pine and eucalypt mycorrhizal associations. In addition, weak to moderate correlations between soil fungal community composition and soil chemical variables (e.g. Spearman rank correlation coefficients for individual variables of 0.08–0.32), indicated a minor contributing role of vegetation-mediated changes in litter and soil chemistry. Our data provide evidence of considerable plasticity in soil fungal community composition over time spans as short as 6–11 years. This suggests that – at least within geographic zones characterised by more-or-less contiguous forest cover – soil fungal community composition depends most on availability of suitable habitat because dispersal propagules are readily available for colonisation after land use change.

Observed and modelled soil carbon and nitrogen changes after planting a Pinus radiata stand onto former pasture

After reforesting pasture land, it is often observed that soil carbon stocks decrease. The present work reports findings from a site near Canberra, Australia, where a pine forest ( Pinus radiata) was planted onto a former unimproved pasture site. We report a number of detailed observations seeking to understand the basis of the decline in soil C stocks. This is supported by simulations using the whole-ecosystem carbon and nitrogen cycling model CenW 3.1. The model indicated that over the first 18 years after forest establishment, the site lost about 5.5 t C ha −1 and 588 kgN ha −1 from the soil. The C:N ratio of soil organic matter did not change in a systematic manner over the observational period. Carbon and nitrogen stocks contained in the biomass of the 18-year old pine stand exceeded that of the pasture by 88 t C ha −1 and 393 kgN ha −1. An additional 6.1 t C ha −1 and 110 kgN ha −1 accumulated in above-ground litter. These changes, together with the vertical distribution of carbon and nitrogen in the soil, agreed well with the observation at the site. It was assumed that over 18 years, there was also a loss of 86 kgN ha −1 from the ecosystem because of normal gaseous losses during nitrogen turn-over and a small amount of nitrogen leaching. Those losses could not be replenished in the pine system without symbiotic biological nitrogen fixation, and there were no fertiliser additions. A simple mass balance approach indicated that the amount of nitrogen accumulating in plant biomass and the litter layer plus the assumed nitrogen loss from the site matched the amount of nitrogen lost from the soil organic nitrogen pool. This reduction in soil nitrogen, together with an unchanged C:N ratio, provided a simple and internally consistent explanation for the observed reduction of soil carbon after reforestation. It supports the general notion that trends in soil carbon upon land-use change can often be controlled by the possible fates of available soil nitrogen.

Captures of Boll Weevils (Coleoptera: Curculionidae) in Traps Associated with Different Habitats

Programs to eradicate the boll weevil, Anthonomus grandis grandis Boheman, from cotton, Gossypium hirsutum L., in the United States rely heavily on pheromone traps for monitoring weevil populations in both active and posteradication maintenance programs. Modifications to trapping protocols that increase trap effectiveness should contribute to this eradication effort. Between October 1996 and May 1997 and between September 1997 and April 1998, we compared trap effectiveness, indicated by the numbers of captured weevils, in relation to selected habitat types. Each study period was divided into fall, winter, and spring seasons. Traps were closely associated with seven habitat types, including four types with prominent erect vegetation (brush-lined irrigation canal, brush, sugarcane, and resaca or ox-bow lake) and three types with only low-growing or sparse erect vegetation (irrigation drainage canal, unimproved pasture, and fallow fields). Captures of male and female weevils were statistically similar regardless of season or trapping habitat. Although captures differed significantly among habitats, these differences varied among seasons. Trapping habitats with prominent vegetational features generally produced higher weekly captures of weevils than habitats lacking these features. Also, captures in traps associated with prominent vegetation indicated seasonal differences in weevil activity, with highest captures occurring during the fall. Traps associated with habitats lacking prominent vegetation did not statistically demonstrate seasonal differences. Our results indicate that immediate trap surroundings strongly influence the effectiveness of the boll weevil pheromone trap. These results also suggest that effectiveness of current trapping programs may be improved through purposeful association of traps with selected vegetational features.

The effect of pasture improvement and burning on Orthoptera populations of Culm grasslands in northwest Devon, UK

Very little research has been conducted into the impact of grassland management on insect populations of Culm grasslands located in northwest Devon, UK. This paper presents the effects of agricultural improvement and burning on Orthoptera populations of these wet, heathy pastures at Dunsdon National Nature Reserve. The results from this 2-year study should aid conservation management of this important UK habitat. Orthoptera populations and habitat variables of improved (drained and cropped from 1840-1875) and unimproved pastures, were monitored in 2002 and 2003. There was no significant difference in Orthoptera abundance between pasture cropped from 1840-1875 and unimproved grassland, suggesting that mobile grasshopper species such as the meadow grasshopper Chorthippus parallelus, recolonised the improved swards from surrounding pastures, after a lengthy period of arable cropping in the 1800s. Winter burning led to higher numbers of Orthoptera in the post-burn year, perhaps due to the reduced sward height and biomass on the burnt swards, making them more favorable for postdiapause development.

Beetle species (Coleoptera) in hayfields and pastures in northern Iceland

Abstract The aim of the present study was to investigate the composition and activity of surface-living invertebrates in hayfields and unimproved pastures on three soil types in northern Iceland. Surface-living beetles were collected in pitfall traps over a 1-year period in three unimproved pastures and three managed hayfields, located on sandy, silty and peat soils. Annual management of hayfields included fertilization and hay cutting, whereas pastures were only grazed occasionally by cattle. During the summer season 42 beetle species were collected, dominated by 23 Staphylinidae species, which comprised 77% of all the coleopterans collected. The dominating coleopterans, both in hayfields and pastures, were Oxypoda islandica, Atheta atramentaria and Atomaria analis. A significantly higher number of specimens of all the most common species, and a slightly higher number of beetle species, were detected on pastures than on hayfields. All the most commonly detected beetle species were more abundant on peat soil than on silty or sandy soil, except Tachinus corticinus, which was not detected on peat soil. The activity of beetle species culminated at different times throughout the summer, A. analis in spring, A. atramentaria in summer and O. islandica in autumn. During the winter season 24 beetle species were detected, of which two were not trapped during the summer season. No difference in the number of species or specimens between pastures and hayfields or between the three soil types was observed during the winter season.

A Comparative Study of the Constituents of Cattle, Sheep and Goat milk in a Hot – Humid Environment

The milk constituents of fifteen lactating ruminant livestock, comprising each of white Fulani cows, West African Dwarf(WAD) does and WAD ewes, were evaluated and compared in a 12-week study. The animals were selected from theUniversity herd and grouped according to stage of lactation (early, mid, late,) They grazed on unimproved pasture,comprising mainly of Panicum maximum, in addition to receiving a concentrate supplement (16.5%CP) compounded frombrewers dry grain, wheat offals and palm kernel cake. Milk samples were obtained weekly from each animal and analyzedfor Total solids (TS), Butterfat (BF), Crude protein (CP), Solids-not-fat (SNF), Lactose, Total ash (TA) and Gross energy(GE).The result showed that early and late lactation stages had no effect on the milk constituents of the three species. Totalsolids and total ash, however, differed significantly (p

Spider (Araneae) populations in hayfields and pastures in northern Iceland

Abstract: Surface‐living spiders were collected in pitfall traps over a 1‐year period in three unimproved pastures and three managed hayfields in northern Iceland, located on sandy, silty and peaty soil. On each of the six fields, six pitfall traps were placed and emptied approximately once a week during summer season, but two traps at longer intervals during winter season. During the summer season, the number of spider specimens was significantly higher in sand than in silt, with peat soil in an intermediate position. Annual management of hayfields includes fertilization, hay cutting and occasional grazing. A total of 22 spider species were collected in the pastures and only 17 in the hayfields. However, the total number of specimens was not significantly different between the two. All spider species were more abundant in pastures than hayfields, with the exception of Erigone atra Blackwall, 1883 and Erigone arctica (White, 1852). These two species dominated the hayfields, together composing 79% of the spider population there, followed by Allomengea scopigera (Grube, 1859) with 7%. The dominance of E. atra in hayfields is related to fertile soils and high‐yielding grass species, which might lead to an increase in certain Collembola species which serve as an important feed for this spider species. However, Tenuiphantes mengei (Kulczyński, 1887) dominated the pastures, representing 22% of the spider population, followed by A. scopigera, Pardosa sphagnicola (Dahl, 1908) and E. atra composing 17, 13 and 12% of the spider population, respectively. E. atra had two abundance peaks, a large peak in early spring (3.7 specimens/day in hayfields), and a smaller peak in early summer, while abundance was much lower the rest of the year. Tenuiphantes mengei had two distinct abundance peaks, one in early summer (0.7 specimens/day in pastures) and another in the autumn, while A. scopigera was almost entirely found in the autumn (1.0 specimens/day in pastures). In general, winter abundance was low, 0.2 specimens/day, compared with 4.4 specimens/day in summer season. In early winter, T. mengei dominated (43% of the spider population), while E. atra dominated in mid‐ and late winter composing 47 and 80% of the spider population respectively.

Intake of improved and unimproved pastures in two seasons by grazing weanling horses

Intake was estimated using the n-alkane technique in 2 groups of 16 grazing weanling horses at Rutherglen during November 1998 (fillies; mean liveweight = 355 kg) and May 1999 (colts; mean liveweight = 266 kg). Weanlings grazed either improved (phalaris, annual ryegrass and subterranean clover; limed and 150 kg/ha superphosphate) or unimproved (annual ryegrass, silver grass, barley grass and subterranean clover; no lime and 125 kg/ha superphosphate) pastures at both high (1.33 horse/ha) and low (0.8 horse/ha) stocking rates. Weanlings were dosed with 500 mg of C32 alkane (via a 300 mL liquid suspension) daily for 7 days prior to, and during, the 4 days of faecal collection. The concentrations of individual alkanes were measured in samples of faeces and herbage. Intake (g OM/kg LW) was then calculated for each horse. A good relationship (r2 = 0.99) was observed between the proportions of herbage and faecal odd-chain alkanes in May 1999. However, in November 1998, the relationship was lower (r2 = 0.86). Assuming the recovery of odd-chain alkanes does not vary with chain length, this suggests pasture samples collected in November may have been less representative of what the horses were selecting, particularly for horses grazing unimproved pastures at the high stocking rate (r2 = 0.79). Intake estimates were similar when C33 or C31 concentrations were used along with the dosed C32, except at the November 1998 sampling for horses grazing unimproved pastures at the high stocking rate. The only significant effect (P<0.05) was the interaction between pasture type and stocking rate at the November 1998 sampling when intake was estimated using the C31/C32 alkane pair.

Roles of land use resolution and unit-area load rates in assessment of diffuse nutrient emissions

In contrast to its counterparts in Europe and North America, the Australian National Pollutant Inventory (NPI) includes estimates of aggregated emissions of nutrients (total nitrogen and total phosphorus) from catchments and facilities. Sparse or inadequate data limit the extent to which nutrient exports may be estimated from direct observations. The paucity of data for calibration and simulation limits the use of sophisticated models in most Australian catchments. Therefore, a simple unit-area load model—Catchment Management Support System (CMSS)—was selected to estimate aggregated catchment emissions for the NPI. Estimates from models like CMSS are sensitive to spatial and categorical resolution of land uses identified within the catchment and to nutrient generation rates selected for each land use category. Using three Hawkesbury–Nepean subcatchments, we show that while high spatial resolution of land use mapping is useful, only four or five major land use categories with carefully selected generation rates were required to estimate potential nutrient exports sufficiently well and to determine subcatchments contributing most. Nutrient emission estimates proved to be highly dependent on selection of generation rates so a bootstrap technique was adopted to reduce subjectivity and to improve estimates of confidence limits. This led to a specification of new generation rates for Natural, Unimproved pasture, Rural and Urban land uses and to establishment of uncertainty limits.

Diversity of arbuscular mycorrhizal fungi colonising roots of the grass species Agrostis capillaris and Lolium perenne in a field experiment.

Analysis of arbuscular mycorrhizal (AM) fungal diversity through morphological characters of spores and intraradicular hyphae has suggested previously that preferential associations occur between plants and AM fungi. A field experiment was established to investigate whether AM fungal diversity is affected by different host plants in upland grasslands. Indigenous vegetation from plots in an unimproved pasture was replaced with monocultures of either Agrostis capillaris or Lolium perenne. Modification of the diversity of AM fungi in these plots was evaluated by analysis of partial sequences in the large subunit (LSU) ribosomal RNA (rDNA) genes. General primers for AM fungi were designed for the PCR amplification of partial sequences using DNA extracted from root tissues of A. capillaris and L. perenne. PCR products were used to construct LSU rDNA libraries. Sequencing of randomly selected clones indicated that plant roots were colonised by AM fungi belonging to the genera Glomus, Acaulospora and Scutellospora. There was a difference in the diversity of AM fungi colonising roots of A. capillaris and L. perenne that was confirmed by PCR using primers specific for each sequence group. These molecular data suggest the existence of a selection pressure of plants on AM fungal communities.

Effects of Plant Cover Improvements for Nesting Ducks on Grassland Songbirds

Several islands located along the St. Lawrence River in southern Quebec have been used as natural pastureland by cattle for decades. Recently, a rest-rotation grazing system and dense nesting cover were established on four islands near Varennes to improve duck nesting conditions. The effects of these two plant cover improvements on the abundance of grassland songbirds were assessed through four treatments: (1) idle fields with no vegetation improvement but exclusion of cattle (IDLE), (2) improved pastures with seeding of forage plants for cattle (IMPP), (3) dense seeded nesting cover fields improved for ducks and where cattle were excluded (DNC), and (4) natural or unimproved pastures grazed by cattle after the duck nesting season (UIPP). The overall abundance of birds was similar among treatments before cover improvements as well as two years after. The abundance of Bobolinks (Dolichonyx oryzivorus) was significantly greater in DNC and UIPP two years after treatments while Red-winged Blackbirds (Agelaius phoeniceus) were more abundant in DNC and IDLE. Plant cover improvements had little impact on Savannah Sparrow (Passerculus sandwichensis) abundance. Furthermore, few annual or treatment-related changes were observed for less abundant species. On the short-term, duck nesting cover improvements in natural pastures did not have any major effect on grassland songbirds on Varennes islands.

Selection, intake and excretion of nutrients by Scottish Highland suckler beef cows and calves, and Brown Swiss dairy cows in contrasting Alpine grazing systems

Nutrient intake, digestibility and live-weight changes were compared for groups of grazing cattle on two Swiss Alpine pastures in different regions (R1 and R2; both &gt;1500 m above sea level) during 2 years (1997 and 1998). The R1 site was an improved pasture, while R2 was an unimproved pasture of poor nutritional quality. Replicated over 2 years, R1 groups comprised four Scottish Highland suckler cows together with their calves and four Brown Swiss dairy cows (17·8 kg/day milk) kept at high stocking rates (approx. 7 cows/ha) in short rotations (intensive management system). R2 groups comprised four Highland cows with calves managed at low density (approx. 0·4 cows/ha) and set-stocked (extensive management system). Grazing seasons lasted 77 days at R1 and 127 days at R2. Intake, digestibility and faecal excretion were estimated by the slow-release alkane indicator method. Average dry matter intakes in kg/day and g/kg W0·75/day (in parentheses) were 17·4 (151) for dairy cows at R1 and, significantly lower, 12·7 (133) and 11·1 (111) for beef cows at R1 and R2, respectively. Herbage dry-matter intake of calves was 1·2 kg/day at both locations. Calf weight gains measured over 77 days (0·69 kg/day) were similar at the two sites and thereafter declined only slightly at R2. The N content of the herbage selected was similar in the two regions, but in other respects the herbage at R2 was of significantly poorer nutritive quality as indicated by the lower digestibility of organic matter and neutral detergent fibre at R2 compared with R1. Through feed selection, nutrient intake by beef cows was sufficient to gain weight. In contrast, dairy cows at R1 lost on average more than 50 kg of weight. Calculations were made and discussed regarding N utilization and urinary N loss, and measured faecal N and mineral excretion to allow a quantitative assessment of nutrient returns to the sward. We conclude that Highland beef cattle make poorer use of improved Alpine pasture than dairy cows though they utilize pastures of poor nutritive quality under extensive management without loss of productivity.

Territory distribution and foraging patterns of cirl buntings ( Emberiza cirlus) breeding in the UK

A recent recovery in cirl bunting ( Emberiza cirlus) numbers in the UK has been aided by deployment of prescriptions for environmentally friendly management of farmland under the Countryside Stewardship Scheme. However, the species' range has not expanded and the population is increasingly under threat from habitat loss due to built development. The UK Biodiversity Action Plan calls for re-establishment of populations outside the current range in order to ensure a wider geographical spread of this species. This study examined territory distribution and foraging patterns of cirl buntings in relation to habitat variables in order to inform the process of site protection and site selection for a possible translocation programme. Cirl bunting territories were positively associated with rough grassland, non-linear scrub and habitat richness, and intensive permanent pasture was avoided. Resampling methods showed that rough grassland was used significantly more than improved pasture as a foraging habitat and that both rough grass and cereals were used more than other arable crops. The results emphasise the importance of protection of unimproved pastures in ‘green field’ sites and will help quantify the potential carrying capacity of candidate ‘receptor’ sites.

Dietary Habits ofSolenopsis invicta(Hymenoptera: Formicidae) in Four Oklahoma Habitats

Dietary habits of the red imported fire ant, Solenopsis invicta Buren, were investigated in four southern Oklahoma habitats: lakeshore, mixed grassland, wooded roadside, and unimproved pasture. Vegetation characteristics of each site were recorded for spring and late summer, in conjunction with estimates of forager success (the percentage of foragers returning to colonies with solid particles or liquid loads). Foragers collected a wide variety of solid particles, with different arthropod prey dominating samples within different sites. At the lakeshore site (no vegetation), dipteran adults, larvae, and pupae comprised >58% of foraged particles. Isoptera comprised >21% of foraged particles at the wooded roadsite site. At grassland and pasture sites, seeds (17.2 and 15.7%, respectively) were important foraged items. Forager success rates were highest for solids at the lakeshore site (&ap;30% and 16% in spring and late summer, respectively), and highest for liquids at the pasture site (&ap;30% and 22% for spring and late summer, respectively). Possible influence of vegetation on success rates, and implications for estimates of foraging energetics, are discussed.

Correlates of Common Buzzard Buteo buteo density and breeding success in the West Midlands

Buzzard density and breeding success in relation to habitat and Rabbit Oryctolagus cuniculus abundance was studied in the West Midlands from 1994 to 1996. We found densities of 81 and 22 territorial pairs per 100 km2 in two areas 40 km apart; the former is the highest density yet recorded in Europe. High Buzzard breeding densities were associated with high proportions of unimproved pasture and mature woodland within estimated territories. Buzzards laid earlier clutches at lower altitudes and with high proportions of unimproved pasture close to nests. Large clutches and high numbers of fledged young were associated with high Rabbit abundance close to nests. Most nest failures occurred during incubation and were probably mainly due to corvid predation. Brood reduction was associated with low proportions of deciduous woodland close to nests and small clutch sizes, although the causes of chick mortality were uncertain. Rabbits were the main prey item found at nests with passerines, especially young corvids, also appearing frequently.

Nonpoint‐Source Pollutant Load Reductions Associated with Livestock Exclusion

AbstractCattle (Bos taurus) grazing on unimproved pastures can be a significant, yet often overlooked, source of pollutants to surface waters, especially when the cattle have unlimited access to streams in the pastures. Livestock exclusion from streams has been demonstrated to reduce sediment and possibly nutrient yield from streams draining pastures. The purpose of this study was to evaluate the effects of excluding dairy cows from, and planting trees in, a 335‐m‐long and 10‐ to 16‐m‐ wide riparian corridor along a small North Carolina stream. Analysis of 81 wk of pre‐exclusion and 137 wk of post‐exclusion fencing data documented 33, 78, 76, and 82% reductions in weekly nitrate + nitrite, total Kjeldahl nitrogen (TKN), total phosphorus (TP), and sediment loads, respectively, from the 14.9‐ha pasture area adjacent to the fenced section of stream. Statistical analyses by t‐tests and analysis of variance suggested that the reductions in mean weekly loads post‐fencing were significant (P &lt; 0.05) for all pollutants except nitrate + nitrite. Thus, the results indicated that livestock exclusion and subsequent riparian vegetation establishment was effective at reducing pollutant export from an intensively grazed pasture.

LAND USE IMPACTS ON THE ISOTOPIC SIGNATURE (13C, 14C, 15N) OF WATER-SOLUBLE FULVIC ACIDS IN A GERMAN FEN AREA

Little is known regarding the impact of land use on the isotopic signature of dissolved organic matter (DOM), although such impacts should occur first in this most mobile part of soil organic matter. The aim of the present study was to investigate the effects of both land use and change on the isotopic composition of DOM. We extracted water-soluble fulvic acids (FA) as the main fraction of DOM from the topsoil, groundwater, and surface water of six sites differing in land use in a natural fen area, and we analyzed 13C, 14C, and 15N. Long-term intensive land use (of at least 50 years) resulted in the enrichment of water-soluble FAs with 13C. Enhanced peat decomposition caused by conventional crop farming resulted in the highest 14C age of water-soluble FAs. The radiocarbon age of the water-soluble FAs in the topsoil and surface water was as much as 1700 years, much older than previously assumed. Long-term agricultural land use with high fertilizer input resulted in 14N enrichment of water-soluble FAs, probably because of the incorporation of light N isotopes derived from mineral fertilizers. 14C and 15N isotopes indicated a distinct change of C and N turnover after changing from conventional crop farming to unimproved pasture. The N and C isotopes of water-soluble FAs are a useful tool to indicate changing C and N cycles caused by long-term (50 to 200 years) differences in land use. Short-term changes in land use (<5 years) are reflected only in the 14C and 15N signature of water-soluble FAs.

Benefits of rotational grazing and dense nesting cover for island-nesting waterfowl in southern Quebec

Intensification of agricultural practices is an important factor responsible for the decline of duck populations throughout North America. More than 200 islands covering a total of 5000 ha are found in the St. Lawrence river between Montreal and Trois-Rivieres in southern Quebec. The value of these islands as duck nesting habitat, however, is often limited by cattle grazing. The effects of two types of habitat improvements, rotational grazing and establishment of dense nesting cover (DNC), on island-nesting waterfowl was studied from 1992 to 1994. Four treatments were compared: idle fields with no vegetation improvement but exclusion of cattle, improved pastures with seeding of forage plants for cattle, DNC fields with improved cover for ducks and exclusion of cattle and unimproved pastures used after the duck nesting season. Before habitat improvements, grazing by cattle reduced dry mass of green vegetation by 53% relative to ungrazed plots. No difference was found in the biomass of live (green) and dead (residual) vegetation among the islands’ sections before treatments. Nest density and the number of expected nests based on the area covered by each habitat were also similar among sections before treatment. Gadwall ( Anas strepera L.), mallard ( Anas platyrhynchos L.), and pintail ( Anas acuta L.) were the most abundant species nesting on the islands and this was not affected by treatments. Two years after habitat improvements, the number of duck nests increased. Idle fields and 2-year old DNC had greater visual obstruction, more residual vegetation and more litter. Densities of 2.8 and 7.0 nests ha −1 with 69 and 82% Mayfield nest success were recorded in the idle and DNC fields, respectively. Nest success was low in improved pasture where a large proportion of nests were trampled (33%) or depredated (28%). Fencing permitted growth of emergent vegetation which enabled over-water nesting by ducks. These results indicate that with appropriate management, coexistence of cattle and nesting waterfowl is possible on islands of the St. Lawrence river.

Fluxes of radiocaesium in selected rural study sites in Russia and Ukraine

Food production and food harvesting systems common in the areas contaminated by the Chernobyl accident in Russia and Ukraine can be grouped into three major categories: collective farm produce, private farming produce and foods collected from natural ecosystems. The contribution of each of these sources to radiocaesium intake by people living in rural settlements in the mid 1990s has been estimated at two major study sites, one in each country. The collective farm system provided the smallest contribution (7–14%) to the intake of radiocaesium at both sites. Natural food was the major contributor to intake at the Russian site (83%). Whereas private farm produce was the major contributor (68%) at the Ukrainian study site. The difference between the two sites was mainly because private milk production was stopped at the Russian site due to the contamination in 1986. A retrospective assessment of the situation 1 year after the accident shows that collective farming could have been a minor contributor to radiocaesium intake (8%), whilst private farming would have been the major contributor wherever private milk production and consumption continued. The extent to which inhabitants consume natural foods from forests has a considerable effect on their radiocaesium intake. The comparative importance of food products from natural ecosystems increases with time due to the long effective ecological half-lives of radiocaesium in unimproved pastures and forests. Estimation of the fluxes of radiocaesium from the different production and harvesting systems showed that the contribution from private farming and food harvesting from natural ecosystems may be significant, contributing 14–30% to the total fluxes of radiocaesium from an area even if the quantity of food produced in these systems is small. However, the major contributor to the flux exported from an area was the collective farming system, accounting for about 70–86% of the total.