Mesic Areas Research Articles

Identifying and Prioritizing Greater Sage-Grouse Nesting and Brood-Rearing Habitat for Conservation in Human-Modified Landscapes

BackgroundBalancing animal conservation and human use of the landscape is an ongoing scientific and practical challenge throughout the world. We investigated reproductive success in female greater sage-grouse (Centrocercus urophasianus) relative to seasonal patterns of resource selection, with the larger goal of developing a spatially-explicit framework for managing human activity and sage-grouse conservation at the landscape level.Methodology/Principal FindingsWe integrated field-observation, Global Positioning Systems telemetry, and statistical modeling to quantify the spatial pattern of occurrence and risk during nesting and brood-rearing. We linked occurrence and risk models to provide spatially-explicit indices of habitat-performance relationships. As part of the analysis, we offer novel biological information on resource selection during egg-laying, incubation, and night. The spatial pattern of occurrence during all reproductive phases was driven largely by selection or avoidance of terrain features and vegetation, with little variation explained by anthropogenic features. Specifically, sage-grouse consistently avoided rough terrain, selected for moderate shrub cover at the patch level (within 90 m2), and selected for mesic habitat in mid and late brood-rearing phases. In contrast, risk of nest and brood failure was structured by proximity to anthropogenic features including natural gas wells and human-created mesic areas, as well as vegetation features such as shrub cover.Conclusions/SignificanceRisk in this and perhaps other human-modified landscapes is a top-down (i.e., human-mediated) process that would most effectively be minimized by developing a better understanding of specific mechanisms (e.g., predator subsidization) driving observed patterns, and using habitat-performance indices such as those developed herein for spatially-explicit guidance of conservation intervention. Working under the hypothesis that industrial activity structures risk by enhancing predator abundance or effectiveness, we offer specific recommendations for maintaining high-performance habitat and reducing low-performance habitat, particularly relative to the nesting phase, by managing key high-risk anthropogenic features such as industrial infrastructure and water developments.

Status of the Harvester Ant (Pogonomyrmex spp.; Hymenoptera: Formicidae) Fauna of Arkansas

Pogonomyrmex Mayr (Hymenoptera: Formicidae) species are collectively termed harvester ants due to their well-described habit of collecting seeds for food (Cole, 1968). North of Mexico, the genus is most speciose in western and southwestern portions of the United States (Johnson, 2000b). Harvester ants are generally associated with xeric, open natural community types such as deserts, grasslands, and woodlands (Taber, 1998). Nests are constructed in soil and characterized by craters or small to large mounds of soil. Some harvester ant species actively clear vegetation from a roughly circular area surrounding nest mounds (Cole, 1968) making these sites conspicuous landscape elements. Once established, a harvester ant colony can persist for decades (MacMahon et al., 2000). Warren and Rouse (1969) list three Pogonomyrmex species as occurring in Arkansas, P. badius (Latreille), P. barbatus (Smith), and P. comanche Wheeler. Their records were gleaned from, what is today, the University of Arkansas Arthropod Museum (UAAM). In an attempt to reassess the status of the genus in Arkansas, I visited the UAAM to examine their Pogonomyrmex holdings and also conducted field surveys for harvester ant colonies in remnant natural communities across the state from 2007–2009. Survey methodology consisted of visually searching sites for foraging workers and nest mounds or craters. A total of 32 sites, in or near counties with occurrence records of harvester ants, were surveyed across Arkansas. Sites surveyed comprised a number of different natural community types including blackland prairie, saline barrens, sandhill woodlands, and tallgrass prairie. The record of P. badius in Arkansas is interesting as this the only Pogonomyrmex species known to occur primarily east of the Mississippi River (Cole, 1968). Its distribution is centered on the Coastal Plain of the southeastern United States and is generally described as ranging from North Carolina, south to Florida, and west to Louisiana (Johnson, 2000b). Warren and Rouse’s (1969) records for P. badius are from Logan and Scott Counties in west-central Arkansas far from the species main range. The authors hypothesized the species potential occurrence ‘‘in the grassland extension of the Oklahoma prairie into western Arkansas.’’ However, neither county cited as hosting P. badius contains the soil types that would support the species colonies. Pogonomyrmex badius colonies are associated with open, xeric natural communities (sand barrens, sandy ridges along streams) on deep, well-drained sandy soils (Cole, 1968; MacGown et al., 2008). Most of Logan County, and a portion of Scott County, are situated in the Arkansas Valley Plains and Scattered High Ridges and Mountains of the Arkansas Valley (Woods et al., 2004). Prior to European settlement, these areas were typified by oak-hickory-pine forests, savannas, and tallgrass prairies. The remainder of Scott County lies in the Fourche Mountains dominated by extensive oak-hickory-pine forests. Both counties are devoid of the deep sand habitats preferred by P. badius. Given these facts, the occurrence of P. badius in Arkansas seemed questionable. My visit to the UAAM supported the notion that Warren and Rouse’s (1969) records for Arkansas were dubious as the specimens once attributed to P. badius have since been re-determined to be workers of P. barbatus. Until contradictory evidence is presented, the presence of P. badius in Arkansas should be considered as tentative. Pogonomyrmex barbatus is a harvester ant that would be expected in Arkansas given its habitat affinities (McCook, 1880; Taber, 1998) and presence in Oklahoma and Texas (Johnson, 2000b). Warren and Rouse (1969) list the species as occurring in Bradley, Crawford, Scott, and Washington Counties. Logan County can now be added to that list given information presented herein. The UAAM also contained specimen records of P. barbatus from Van Buren County not previously noted by Warren and Rouse (1969). Crawford, Logan, Scott, Van Buren and Washington Counties are all along or very near Arkansas’s western border. Bradley County is located in south-central Arkansas. Unlike P. badius, P. barbatus colonies are associated with more mesic areas, especially those sites with higher clay content in their soils (Taber, 1998; Johnson, 2000a).

Distribution and Basic Biology of Black Cherry-Infesting Rhagoletis (Diptera: Tephritidae) in México

Abstract To better understand the phylogeography of Rhagoletis flies in the cingulata species group, we conducted a seven year host plant survey in México, behavioral observations, and studies on the basic biology of these tephritids. The survey revealed the existence of two geographically isolated Rhagoletis cingulata (Loew) populations in México. The first population was found to be restricted to Prunus serotina ssp. capuli (Cav.) McVaugh in an area within the central dry Altiplano spanning from Tlaxcala to México City and neighboring parts of the States of México, Puebla, and Hidalgo. The second population was found to infest Prunus serotina ssp. virens (Wooton & Standl.) McVaugh in high elevation areas of northeastern México between San Luis Potosí and Coahuila along the Sierra Madre Oriental. Both populations were hosts to the parasitoid Diachasmimorpha mellea (Gahan) (Hymenoptera: Braconidae), with percentage parasitism varying across sites. Collections of P. s. ssp. capuli and Prunus serotina Ehrh. ssp. serotina across the Eje Volcanico Trans Mexicano, the Sierra Madre del Sur, the Sierra de los Altos de Chiapas and mesic areas of the Sierra Madre Oriental between Veracruz and Queretaro failed to yield any pupae. Sites where pupae were recovered were significantly dryer than sites where R. cingulata was not found. Recovered flies were found to be univoltine and to overwinter as pupae. Adults in the field in Tlaxcala (Central Altiplano) were mainly sighted guarding, mating, and ovipositing in green fruit. Larval yield of fruit collected outside the natural area of distribution, and exposed to flies in the laboratory, was significantly lower than that of fruit collected within the natural range of R. cingulata. We compare distribution patterns with those of other species in the genus and discuss hypotheses to explain the outcome.

Rotational Grazing Systems and Livestock Grazing Behavior in Shrub-Dominated Semi-Arid and Arid Rangelands

Rotational grazing systems (RGS) are often implemented to alleviate undesirable selective grazing by livestock. At both fine and coarse scales, livestock selectively graze individual plants, patches, communities, and landscapes. Smaller pastures, increased stocking density, and rotation allow managers to constrain livestock movement and determine season and frequency of grazing, potentially limiting selectivity and preventing repeated grazing of preferred plants. However, in arid and semi-arid rangelands, forage growth is limited primarily by precipitation rather than defoliation frequency. When soil moisture is adequate, forage is abundant and defoliation levels are typically low, and repeated, intensive defoliation of preferred plants is less likely than in more mesic areas where more consistent precipitation and soil moisture storage allows animals to establish and maintain spatial hierarchies of grazing patterns. Many southwestern rangelands contain diverse vegetation, which provides quality forage during different times of the year. These spatial and temporal patterns of forage distribution may not be amenable to manipulation with RGS. Tracking data show that livestock often alternate among locations within pasture boundaries and can opportunistically exploit areas with higher quality forage when they are available. Higher stock densities combined with higher stocking rates can increase livestock use of less preferred areas, but overall distribution patterns of intensive-rotational and extensive grazing systems are often comparable at similar stocking rates and distances from water. Management that ensures that grazing of riparian areas does not occur during the critical late summer period may be more beneficial than RGS that periodically defers livestock use throughout the grazing season. In arid and semi-arid shrublands, timely adjustments to animal numbers and practices that improve grazing distribution at regional and landscape scales are more likely to be effective in maintaining or improving rangeland health than fencing and RGS. Los sistemas de pastoreo rotativos (SPR) son utilizados frecuentemente para contrarrestar los efectos no-deseados del pastoreo selectivo del ganado. Tanto a escalas finas como gruesas el ganado pastorea selectivamente plantas individuales, parches, comunidades y paisajes. Potreros más pequeños, mayor densidad animal, y la rotación permiten poner límites al movimiento de los animales y determinar la estación y la frecuencia de pastoreo, limitando potencialmente la selectividad y previniendo el pastoreo reiterado de plantas preferidas. Sin embargo, en pastizales áridos y semiáridos, el crecimiento del forraje está limitado principalmente por precipitación y no por la frecuencia de defoliación. Cuando la humedad edáfica es adecuada, el forraje es abundante y los niveles de defoliación son típicamente bajos, y la defoliación repetida e intensa de plantas preferidas es menos probable que en áreas más mésicas donde la precipitación consistente y el almacenaje del agua en el suelo permiten que los animales establezcan y mantengan jerarquías espaciales de patrones de pastoreo. Muchos de los pastizales naturales del sudoeste de los Estados Unidos contienen vegetación diversa que provee forraje de calidad en distintos momentos del año. Estos patrones espaciales y temporales de distribución de forraje podrían no ser susceptibles a ser manipulados a través de SPR. Datos de monitoreo con GPS demuestran que los vacunos alternan entre lugares dentro de los limites de un potrero y que pueden utilizar áreas de mayor calidad de forraje de modo oportunista cuando las mismas están disponibles. Densidades animales más elevadas combinadas con cargas animales más altas podrían incrementar el uso de áreas menos preferidas pero los patrones globales de distribución del pastoreo de sistemas rotativos intensivos y sistemas de pastoreo extensivos son frecuentemente comparables bajo condiciones similares de carga animal y distancia al agua. Un manejo que asegure la exclusión del pastoreo de aéreas ribereñas (vegas/mallines/humedales) en el período crítico de fines del verano podría ser más beneficial que SPR que periódicamente difieren el uso del ganado durante la estación de pastoreo. En estepas arbustivas áridas y semiáridas ajustes oportunos del número de animales y prácticas que mejoren la distribución del pastoreo a escalas regionales y del paisaje podrían ser más efectivos que la construcción de alambrados y el uso de SPR en mantener o mejorar la salud del pastizal.

Drought-induced growth decline of Aleppo and maritime pine forests in south-eastern Spain.

Climate warming may enhance the negative effects of droughts on radial growth in areas with severe water deficit, such as Mediterranean mountains under semi-arid conditions. The impacts of drought on growth decline of Mediterranean pines have not been evaluated considering species with different vulnerability and areas with contrasting climates. Dendrochronological methods were used to assess the responses of basal area increment to drought in Pinus pinaster and P. halepensis plantations. We compared growth trends of trees with different defoliation degree in two sites in south-eastern Spain (Sierra de los Filabres and Sierra de Baza) with contrasting climatic conditions. In the more xeric area (Filabres) both pine species showed a sharp growth reduction in response to extreme droughts such as those observed in 1994-1995, 1999 and 2005. The radial growth of both species was enhanced by May and June precipitation of the year of tree-ring formation. P. pinaster showed higher defoliation in the xeric area (Filabres) than in the more mesic area (Baza) but needle loss was not linked to an abrupt growth reduction. Contrastingly, divergent radial growth patterns between trees showing high and low defoliation degrees were found for P. halepensis in the more xeric area, where a negative relationship between recent basal area increment and defoliation was found. Pine plantations in Mediterranean mountains under semi-arid conditions are highly vulnerable to warming-induced droughts. Such marginal stands constitute valuable monitoring systems to assess the negative impacts of drought on tree growth, and to test if management strategies as thinning can mitigate the negative impacts of climate warming on similar drought-stressed forests.

Is the lack of leguminous savanna trees in grasslands of South Africa related to nutritional constraints?

As with many grasslands globally, the Highveld grasslands of South Africa are tree-less, despite having a climate that can support tree growth. Models predict that fire maintains these grasslands. The question arises as to why fire-tolerant savanna trees do not survive in these ecosystems? Savanna tree survival in mesic areas is restricted by demographic bottlenecks, specifically limitations to sapling-escape from fire. It was hypothesised that ancient highly leached soils from grassland areas would prevent saplings from growing fast enough to escape the fire-trap. Growth rates of savanna tree seedlings (Acacia karroo Hayne and Acacia sieberiana Burtt Davy) were measured in a common garden experiment using soils from ten sites collected along a savanna-grassland continuum. Soils from grassland sites were relatively nutrient-poor compared to those from savannas with lower pH, and associated cations. A. sieberiana growth rates responded to pH and these nutrients, whereas A. karroo growth was less strongly linked to specific nutrients. Even so, both species accumulated more biomass when grown in soils from savanna sites compared to grassland sites. An exception was a low elevation low nutrient savanna site that resulted in poor growth, yet sustains high tree biomass in situ. Differences between growth in grassland and savanna soils were small. They may contribute to, but are unlikely to explain, the treeless nature of these grasslands.

Sunlit mesocosms designed for pollen confinement and risk assessment of transgenic crops

To minimize concerns about the ecological consequences of wind and insect dispersal of pollen and the potential of gene flow from experimental genetically modified (GM) crops to compatible relatives, we have modified outdoor sunlit open top chambers (OTCs) for use with GM plants. We have redesigned 21 cylindrical OTCs, commonly used to study the effects of atmospheric pollutants, by adding (1) a pollen filter at the top of each unit to minimize the possibility of the escape of GM pollen; with pollen filters in place, the OTCs are referred to as mesocosms, (2) an evaporative cooler to help mitigate elevated temperatures during the summer months, and (3) an automated watering system that eliminates the need to enter a mesocosm for irrigation during pollination, thereby minimizing potential pollen escape and entry of insect pollinators. Each sunlit mesocosm contains three large plastic pots (each with 1.2-m2 surface area) that simulate field plots and that contain a constructed plant community. For example, the community may consist of a GM and a non-GM cultivar of canola (Brassica napus), compatible weedy relatives, and non-compatible species that may be found in mesic disturbed areas such as roadsides or ditches beyond crop fields. The sunlit mesocosms provide a well-replicated outdoor testing system that confines pollen and that can be used to precede or supplement field tests that evaluate the potential ecological consequences of transgenic crops. The mesocosms are proposed as test systems in which transgenic crops and other plants (e.g., biofuel crops) that have been proposed to be grown in new geographies, or plants that produce novel compounds, may be studied to evaluate their potential effects on plant communities. The pollen confinement and insect exclusion features of our mesocosms may also minimize exposure of sensitive humans and insect pollinators to pollen and cellular debris from other plant parts.

Effects of season and social status on gonadal function in social Natal mole-rats

The reproductive cycle of mammals can be inhibited by 2 factors, seasonal breeding and dominance control, both potentially important in mole-rats. The gonads and gonadal steroids of dominant (reproductive) and subordinate (nonreproductive) Natal mole-rats (Cryptomys hottentotus natalensis) were investigated to determine the effects of season and social status on reproduction within natal colonies. We found no seasonal differences in concentrations of gonadal steroids of male or female mole-rats. Similarly, the gonadal histology and volume showed no seasonal differences. These results, together with the presence of fetuses, confirm the potential for breeding throughout the year. Reproductive and nonreproductive mole-rats display comparable testosterone and estrogen concentrations in males and females, respectively. Follicular development and the presence and number of sperm in nonreproductive animals suggest that the reproductive quiescence in nonreproductive animals is likely to result from behavioral interference of dominant animals or incest avoidance (or both). Urinary progesterone concentrations of reproductive females were significantly higher than those of nonreproductive females. Although follicular development in nonreproductive females proceeds to the level of Graafian follicles, the number of these follicles present in nonreproductive females was significantly less than that in reproductive females. The reproductive physiology of the Natal mole-rat compares with other loosely social mole-rat species inhabiting mesic areas.

The biogeographical influence of the Tankwa Karoo Basin on reptile distribution in south-western South Africa

Point distribution data were used to evaluate the biogeographical influence of the arid Tankwa Karoo Basin on the distribution of reptiles in the south-western districts of South Africa. Under-representation of the Tankwa Karoo in the dataset required an additional field survey of this region. Prior to the survey, available records from the Tankwa Karoo Basin represented only 13 reptile species. A total of 36 species (24 lizards, nine snakes, three chelonians) was recorded during our survey of this area. Turnover across the Basin is high, species richness is lower than in surrounding mountainous areas and there are no species endemic to the area. The Tankwa Karoo Basin acts as a dispersal barrier for many reptile species occurring in the surrounding more mesic areas. At the same time, the ranges of a number of typical northern, arid-adapted species extend southward along the Tankwa plains. A number of species range extensions in the region are reported.

Revision of the new Australian wolf spider genus Kangarosa (Araneae: Lycosidae: Artoriinae)

The new Australian wolf spider genus Kangarosa is revised to include ten species: Kangarosa alboguttulata (L. Koch, 1878) comb. nov., K. focarius sp. nov., K. ludwigi sp. nov., K. nothofagus sp. nov., K. ossea sp. nov., K. pandura sp. nov., K. properipes (Simon, 1909) comb. nov. (= Trochosa tristicula phegeia (Simon, 1909) new synonymy) (type species), K. tasmaniensis sp. nov., K. tristicula (L. Koch, 1877) comb. nov., and K. yannicki sp. nov. The presence of a basoembolic apophysis and the apicad orientation of the tegular apophysis in the male pedipalp identify Kangarosa as member of the subfamily Artoriinae Framenau, 2007. Kangarosa differs from all other artoriine genera by the distinct shape of the tegular apophysis, which forms an elongated hook. The female epigyne has a simple, shallow atrium that extends into a posterior lip. Kangarosa is a typical representative of the Bassian fauna as its representatives occur in the southeastern Australian mainland states, Tasmania and in southwest Western Australia. Here, members of the genus are commonly found in mesic areas, for example along watercourses and in swampy areas, although some species appear to prefer forested habitats. Male pedipalp morphology suggests close affinities of Kangarosa to Tetralycosa Roewer, 1960 in a clade that also includes Diahogna Roewer, 1960 and potentially a further undescribed Australian artoriine genus. Kangarosa is of Gondwanan origin and all but one species are restricted to eastern Australia suggesting the genus diversifi ed after an aridifi cation of Australia in the late Tertiary provided a barrier for dispersal between the eastern and western temperate regions.

The ecology of Eurotestudo h. hermanni in a mesic area of southern Italy: first evidence of sperm storage

The daily and annual cycle, the activity pattern, and the spatial behaviour of a population of Eurotestudo h. hermanni were investigated in a mesophilous wooded biotope of southern Italy. A total of eight animals, four males and four females, were fitted with transmitters and monitored for an entire season of activity. Daily activity patterns varied in relation to the season and the daily cycle. Basking activity was dominant in May–June and September, while feeding behaviour peaked in June and October. Mating behaviour was only observed in late summer, while evidence of egg laying was found from late spring, suggesting sperm storage by females. Size of home ranges varied between 1.0 and 3.3 ha for females and from 0.5 and 2.8 ha for males. A wider overlap was observed between home ranges of males and females, suggesting a higher tolerance toward the other sex. Tortoises monitored for the entire activity period showed homing behaviour towards their hibernation sites, confirming the excellent orientation skills of the species.

Geographic variation in the response to thermal acclimation in rufous‐collared sparrows: are physiological flexibility and environmental heterogeneity correlated?

1 It has been proposed that habitats with low productivity, and hence low resource availability, may favour individuals with lower rates of resource use and energy expenditure. In birds, some studies have shown that basal metabolic rate (BMR) and total evaporative water loss (TEWL) are reduced in desert bird species compared to those that live in more mesic areas. However, the contribution of the phenotypic plasticity of birds to this pattern has been poorly studied. 2 We evaluated the phenotypic flexibility of BMR, TEWL and organ size in sparrows (Zonotrichia capensis) from three populations along an aridity gradient that differ in environmental temperature, rainfall and seasonality. We also tested the hypothesis that populations from variable environments exhibit more physiological flexibility than populations from stable environments. 3 BMR and TEWL in Z. capensis exhibited a positive association with latitude. Additionally, the population from the more stable environment was unaffected by thermal acclimation, but birds from seasonal environments were affected. 4 Our results support the hypothesis of the existence of a correspondence between environmental variability and phenotypic flexibility; that is, birds from localities with a drastic climatic seasonality have a greater response in BMR to thermal acclimation than birds from a more stable environment.

Frequency and precision of aerial surveys for kangaroo management

The appropriate frequency and precision for surveys of wildlife populations represent a trade-off between survey cost and the risk of making suboptimal management decisions because of poor survey data. The commercial harvest of kangaroos is primarily regulated through annual quotas set as proportions of absolute estimates of population size. Stochastic models were used to explore the effects of varying precision, survey frequency and harvest rate on the risk of quasiextinction for an arid-zone and a more mesic-zone kangaroo population. Quasiextinction probability increases in a sigmoidal fashion as survey frequency is reduced. The risk is greater in more arid regions and is highly sensitive to harvest rate. An appropriate management regime involves regular surveys in the major harvest areas where harvest rate can be set close to the maximum sustained yield. Outside these areas, survey frequency can be reduced in relatively mesic areas and reduced in arid regions when combined with lowered harvest rates. Relative to other factors, quasiextinction risk is only affected by survey precision (standard error/mean × 100) when it is >50%, partly reflecting the safety of the strategy of harvesting a proportion of a population estimate.

Litho-refugia: the importance of rock landscapes for the long-term persistence of Australian rainforest fauna

Rainforest was formerly widespread on the Australian continent but underwent large-scale contraction to pockets on the east coast through the Miocene and Quaternary. This contraction was due to increasingly dry and seasonal climatic conditions across the continent, which reached greatest severity during the glacial cycles of the Pleistocene. Extensive areas of exposed, layered rock in the mesic areas of Australia provide similar microclimatic conditions to rainforest, in being cool, moist and largely sheltered from fire. These rock habitats are stable and relatively buffered from short- and long-term climatic changes. Therefore, rock habitats can act as refugia (litho-refugia) for the persistence of rainforest lineages in areas where rainforest is currently, or was historically, marginal or absent. Here we outline a number of examples of rainforest faunal groups, primarily from mid-eastern and northeastern Queensland, that exemplify the importance of rock landscapes in the persistence of rainforest lineages.

Ecological Engineering by a Mega-Grazer: White Rhino Impacts on a South African Savanna

Herbivory can change the structure and spatial heterogeneity of vegetation. We ask whether all species of grazers in a savanna ecosystem can have this effect or whether megaherbivores (>1000 kg) have a ‘special‘ role that cannot be replicated by other species of grazers. We performed a replicated landscape scale experiment that examined the effects of White Rhino on the grass sward, on other species of grazing mammals and on the movement of fire through the landscape. White Rhino maintained short grass (‘lawn‘) patches in mesic areas (750 mm pa) with increases in grass sward height when they were removed. Other species of grazers were unable to maintain short grass communities when White Rhino were removed. In semi-arid areas (600 mm pa) other, smaller grazers were able to maintain short grass communities in the absence of White Rhino and sward height did not increase. White Rhino removals affected fire by increasing fuel loads and fuel continuity. This resulted in larger, less patchy fires. We propose that the White Rhino acts as an influential ecosystem engineer, creating and maintaining short grass swards, which alter habitat for other grazers and change the fire regime. These results indicate the existence of context-dependent facilitation between White Rhino and other grazers in mesic, but not in semi-arid, savannas. Such top down effects on the ecosystem may have been much more widespread before the extinction of large grazers in the Pleistocene.

Variability in surface‐subsurface hydrologic interactions and implications for nutrient retention in an arid‐land stream

Hydrologic interactions among biogeochemically active stream subsystems affect material export downstream. We combined a conservative tracer addition with measurements of water table elevation and nutrient concentrations of surface and subsurface water to examine hydrologic interactions among surface and subsurface subsystems and their implications for stream biogeochemistry. We injected bromide (Br−) into a 400‐m reach of Sycamore Creek, a losing stream in central Arizona, for 15 d and monitored changes in concentration in three subsystems: surface, parafluvial, and riparian zones. Additionally, we collected water samples from these subsystems for nutrient analyses. Water flowed from surface to subsurface zones as expected in this losing stream, but a significant amount of subsurface water (17% of surface discharge in the reach) returned to the surface. Within the parafluvial subsystem, median transport time (Tmed) in two gravel bars differed substantially (from 2 to 30 h and from 6 to >300 h, respectively, for upper and lower bars), and varied significantly with depth in the lower bar (mean (±se) Tmed = 190 ± 20 h at 30 cm compared to 101 ± 18 h at 110 cm). Flow paths from the surface to parafluvial and riparian zones, and subsequently back to the surface stream, differ from patterns in mesic areas, where water moves laterally and vertically towards the surface stream. Estimates of nutrient retention for the stream reach varied four fold in response to simulated changes in lateral subsurface connections and the configuration of subsystems. Thus at this scale, accurate nutrient budgets require an understanding of surface‐subsurface connections and hydrologic parameters.

Effect of breed, season and pasture moisture gradient on foraging behaviour in cattle on semi-natural grasslands

The objectives of this study were to determine the effects of breed, season and pasture moisture gradient on the extent and location of grazing and ruminating behaviour in cattle kept on heterogeneous semi-natural grasslands. Two groups of heifers, 12 of the traditional Swedish breed Väneko and 12 of the commercial Continental breed Charolais, were allocated into three enclosures per breed. Each enclosure consisted of heterogeneous semi-natural grasslands dominated by Deschampsia cespitosa (tufted hairgrass) and each contained dry, mesic and wet areas. In spring, summer and autumn, behaviour was recorded using automatic behaviour recorders, and positioning and activity were recorded using GPS receivers for 24 h for every heifer. The Väneko heifers had a higher activity than the Charolais heifers ( P = 0.006), which supports the theories of resource allocation and contrafreeloading, but there were no differences between breeds in location of grazing, ruminating or idling. The heifers spent more time grazing in autumn (42.5% of the day) than in spring (38.5%; P = 0.006) and summer (38.9%; P = 0.014) and the efficiency of grazing ( i.e. proportion of eating during grazing bouts) increased over the grazing period ( P < 0.001). The results indicate the heifers avoided grazing in darkness which is consistent with the theory that predation risk affects foraging. Herbage in wet areas had a lower concentration of crude protein ( P = 0.036) and a higher concentration of neutral detergent fibre ( P = 0.011) than herbage in dry areas. At the same time, on average over seasons, 28% of the herbage mass was found in the wet areas, whereas only 8% of the grazing occurred there. Furthermore, the proportion of eating during grazing bouts was lower (73.9%; P < 0.001) in wet areas than in dry (80.1%) and mesic (79.6%) areas. The results indicate the heifers avoided grazing in wet areas where forage had a low nutritional value, supporting the theory of optimal foraging. In conclusion, both breed and season affects foraging behaviour of cattle on semi-natural grasslands, as the heifers of the traditional breed had a higher activity than the commercial breed and the grazing time was longer and more effective in late than in early grazing period. The cattle avoided foraging in wet areas, which may impact on the management of these areas.

Demography of Eurotestudo hermanni in a mesic area of Central Italy

Abstract Hermann's tortoise (Eurotestudo hermanni) from a mesic area of Central Italy (Isernia, Molise) was investigated during a two-year period (2003-2004). The population is characterized by a fairly high density when compared to other Italian and European populations, with density ranging from 16.16 individuals/ha in 2003 to 25.08 individuals/ha in 2004 (average density 20.84/ha). The sex ratio was 1:1 both in 2003 and 2004. Females were captured in higher percentages from May to July in both years, while males were most abundant from August to October. These differences can be related to the different needs and behaviour of males and females in the two periods, and to the environmental constraints of the study area. All the marked tortoises were found aged between 10 and 21 years. Adult males and females from the study area were small-sized when compared to those from other Italian and European populations.

Population Structure and Density of Leopard Tortoises (Geochelone Pardalis) on Farmland in the Nama-karoo

The Leopard Tortoise (Geochelone pardalis) is the largest of the southern African species and has a wide distribution encompassing a variety of habitats. There is a paucity of ecological information about Leopard Tortoises in these habitats. The goal of this study was to determine the population density, biomass, sex and age distributions, and morphometrics of Leopard Tortoises on farmland in the semi-arid Nama-Karoo. Because previous studies have found that body size distributions vary between mesic and xeric habitats, we expected that these Leopard Tortoises would show an increased body size compared to those from more mesic areas. In addition, we expected lower densities of Leopard Tortoises compared to more mesic areas. In total, 92 tortoises were caught with a male to female sex ratio of 1:1.3 that was not significantly different from unity. Adult females were significantly larger than males with respect to all morphometric measurements. Leopard Tortoises (excluding juveniles) were larger than those from more mesic areas. A population estimate of 57.6 ± 4.0 tortoises in a 5500 ha area was obtained using a mark-recapture sampling method and radio-telemetry. Density of tortoises was extremely low at 0.017 tortoises ha−1, with a biomass of 0.002 kg ha−1. Population density and biomass were lower compared with Leopard Tortoise populations in more mesic areas. This has implications for the understanding of fitness parameters and conservation of this species in semiarid areas.

Effect of Herbicides for Leafy Spurge Control on the Western Prairie Fringed Orchid

Abstract Leafy spurge has invaded the habitat of the western prairie fringed orchid, a federally listed threatened species. Imazapic ([±]-2-[4,5-dihydro-4-methyl-4-{1-methylethyl}-5-oxo-1 H -imidazol-2-yl]-5-methyl-3-pyridinecarboxylic acid) and quinclorac (3,7-dichloroquinoline-8-carboxylic acid) are relatively new herbicides that control leafy spurge and can be used in the mesic areas where the orchid is found. Research was initiated to evaluate the effects of imazapic and quinclorac on the survival and fecundity of the western prairie fringed orchid. Herbicides were applied at the commonly used and maximum labeled rates in mid-September. This timing is optimum for leafy spurge control with quinclorac and imazapic and the orchid generally has senesced by mid-September, making injury less likely. Quinclorac applied at 840 and 1 120 g·ha −1 did not affect regrowth or fecundity of the western prairie fringed orchid 1 or 2 years after treatment. Orchids treated with quinclorac at 840 or 1 120 g·ha −1 generally were as tall, had racemes as long as, and produced as many flowers and seed capsules as untreated orchids. In contrast, orchids treated with imazapic at 140 or 210 g·ha −1 tended to regrow as vegetative plants and were shorter, had shorter racemes, and produced fewer flowers and seed capsules than untreated orchids. Orchids treated with imazapic averaged 21 cm in height and produced an average of 1 flower per plant 10 months after treatment, whereas untreated orchids and orchids treated with quinclorac were approximately 36 cm in height and produced 5 flowers per plant. Quinclorac could be a valuable tool to control leafy spurge in the habitat of the orchid because orchids treated with quinclorac regrew as vigorously and were as fecund as untreated orchids. However, the current quinclorac label prohibits grazing or haying for 309 days after application.