Squirrel poxvirus: Landscape scale strategies for managing disease threat

Squirrel poxvirus (SQPV) is a well-documented example of pathogen-mediated competition between an invasive species, the grey squirrel (Sciurus carolinensis), and a native species, the Eurasian red squirrel (Sciurus vulgaris). SQPV causes disease with high mortality in red squirrels but appears non-pathogenic in grey squirrels. Not all populations of introduced grey squirrels carry the virus, notably those in Scotland and Italy, and the rate of red squirrel replacement by grey squirrels is some twenty times faster in those areas where grey squirrels carry the virus. Here we develop strategies to manage the SQPV disease threat to red squirrels by reference to the largest, designated red squirrel refuge site in England, Kielder Forest (50 000 ha). Using modelling techniques, we identify four main corridors within the buffer zone by which grey squirrels will reach Kielder, initially within two years and in large numbers within 10 years. Assuming that greys will not settle within Kielder because of the unfavourable nature of the spruce habitat, we predict that SQPV disease will burn out at the edges of the forest, although many red squirrels will die. This burn-out is unlikely to be the scenario in other refuge areas where the habitat is more favourable to greys. We conclude that the conservation of red squirrels will depend on minimising contact between red and grey squirrel populations, and we advocate monitoring grey squirrels in corridors within buffer zones around refuge areas, and removing them when detected.     

Predicting the spread of the American grey squirrel (Sciurus carolinensis) in Europe: A call for a co-ordinated European approach

The introduction of the American eastern grey squirrel (Sciurus carolinensis) in Europe is causing a dramatic decline of the native European red squirrel (Sciurus vulgaris), due to competition. We used spatially explicit population dynamics models to illustrate the potential expansion of the grey squirrel from Italy, the only continental country with the species, into neighbouring countries. Simulations started with the known grey squirrel distributions in 1996 and modelled the spread for the next 100 years in two different scenarios. One “best case” in which a random seed crop pattern of poor, good and mast seed crops was simulated with concomitant effects on squirrel fecundity and mortality and one “worst case” scenario in which poor years were not included. In the best case scenario, it will take 30-40 years for grey squirrels to start invading the Alps and about 70-75 years to cross the border between Italy and France. First populations in Switzerland are predicted in 2051-2066. In the worst case scenario, the spread will be significantly faster: the species is predicted to reach France in 2026-2031 and Switzerland in 2031-2041. Removing two of the three populations of grey squirrel will likely postpone the invasion of Switzerland but not of France. Large areas of Europe contain potentially good habitat for grey squirrels, and expansion from Italy, to France, Switzerland and belong to most of Eurasia is simply a matter of time. This will represent a serious risk for the conservation of the native red squirrel and will have implications for national forest operations. However, a European policy towards introduced species is still lacking. There is therefore a need for a co-ordinated European approach to the management of the grey squirrel and other introduced species.     

Integrated diurnal soil respiration model during growing season of a typical temperate steppe: Effects of temperature, soil water content and biomass production

Soil respiration was measured with the enclosed chamber method in an ungrazed Leymus chinensis steppe during the growing seasons of 2001 and 2002. Soil respiration rate (R_S) was significantly influenced by air temperature (T) at the diurnal scale, and could be described by Van't Hoff's equation (R_S = R₁₀ exp(β(T − 10))). At the seasonal scale, the normalized soil respiration rate at 10 °C (R₁₀) was mainly controlled by soil water content (R² = 0.717, P < 0.001), while the sensitivity of soil respiration to temperature (Q₁₀) was partially affected by absolute growth rate (R² = 0.482, P = 0.004). Thus, soil respiration could be described as R_S = (20.015W − 84.085) (0.103AGR + 1.786)^(T−10)/10 during the growing seasons, integrating soil water content (W) and absolute growth rate (AGR) into the temperature-dependent soil respiration equation. It was validated by the observed soil respiration rates in this study (R² = 0.890, P < 0.001) and observations from near-field experiment (R² = 0.687, P = 0.011). It implied that accurately evaluating annual soil respiration should include the effects of plant biomass production and other abiotic factors besides air temperature.     

Unexpected high levels of genetic variability and the population structure of an island endemic rodent (Oryzomys couesi cozumelae)

Oryzomys couesi cozumelae is an endemic, threatened rodent from Cozumel Island, Mexico. We estimated its genetic diversity and structure by analyzing microsatellite loci in 228 samples from 12 sampling sites widely distributed throughout the island. Unexpected high levels of genetic and allelic diversity were found: a total of 54 alleles, an average of 10.8 alleles per locus, and high heterozygosity values (mean H_O = 0.624, H_E = 0.690 and H_Nei = 0.689). These values are higher than those reported for small sized insular mammals, higher than that found in 37 individuals of the mainland O. couesi from southern Mexico (H_O = 0.578) that we analyzed for comparative purposes, and similar to those of other mainland small mammal populations. Despite factors that affect Cozumel’s biota, such as exotic predators and competitors, hurricanes, seasonal population fluctuations and anthropogenic activities, no evidence of genetic bottlenecks was found. A significant population structure was observed and a model of isolation-by-distance was supported. Our findings render O. c. cozumelae a high conservation value, not only for its high genetic diversity and structure, but because available data suggests that its population has declined significantly in recent years. Further habitat fragmentation and population isolation could result in a higher genetic structure and loss of genetic diversity. The protection of habitat, the maintenance of habitat connectivity and the removal of introduced competitors and predators are a conservation priority. Acknowledging that the genetic structure of populations has crucial conservation implications, the present genetic information should be taken into account in management plans for the conservation of O. c. cozumelae.     

Genetic diversity of core and peripheral Sitka spruce (Picea sitchensis (Bong.) Carr) populations: implications for conservation of widespread species

This study investigated levels of genetic diversity and population differentiation among Sitka spruce (Picea sitchensis) populations classified as core or peripheral based on ecological niche, and continuous or disjunct based on species distribution. Large numbers of trees (N = 200) were sampled from each of eight populations to evaluate the distribution of rare as well as common alleles across the species range. Codominant alleles for eight sequence-tagged site loci were classified based on frequency and geographic distribution in order to develop appropriate sampling strategies to target specific classes of alleles. An important finding of this study is the similarity in genetic diversity as measured by expected heterozygosity between core populations (mean H_E = 0.58) and peripheral populations (mean H_E = 0.56). However, there was significant inbreeding in peripheral (F_IS = 0.17) but not in core (F_IS = 0.03) populations. Large differences in gene flow estimates were observed between core (Nm = 9.0) and peripheral populations (Nm = 3.5). Irrespective of population classification, over 75% of the alleles were common and widespread. Only one allele was classified as rare and localized, and this allele was limited to one core, disjunct and two peripheral, disjunct populations. There was stronger evidence of past bottlenecks in peripheral, disjunct populations than in core, continuous populations. Results are used to suggest sampling strategies for capture of maximum level of genetic diversity and conservation of rare alleles. The conservation of peripheral, particularly disjunct, populations as well as populations in putative glacial refugia may present the best opportunity for conserving rare alleles.     

Degradation of tropical forest in Hainan, China, 1991-2008: Conservation implications for Hainan Gibbon (Nomascus hainanus)

The Hainan gibbon (Nomascus hainanus) is one of the most endangered primates in the world, confined to mature natural forest in Hainan Island, China. We assessed changes in habitat condition on the island between 1991 and 2008, using vegetation maps generated by remote-sensing images. We defined forest suitable for gibbons based on composition, tree size and canopy cover. During the 17-year period, the area of suitable gibbon forest decreased by 540 km² (35%) across the whole island, and by 6.3 km² (7%) in the locality of the sole remaining gibbon population at Bawangling National Nature Reserve. The forest patches large enough (>1 km²) to support a gibbon group decreased from 754 km² to 316 km² in total area, and from 92 to 64 in number. Suitable natural forest was mainly replaced by plantations below 760 m, or degraded by logging, grazing and planting of pines above 760 m. Meanwhile, forests in former confirmed gibbon areas became more fragmented: mean area of patches decreased by 53%. We mapped the patches of natural forest in good condition which could potentially support gibbons. We recommend a freeze on further expansion of plantations between core patches at Bawangling, Jiaxi-Houmiling and Yinggeling Nature Reserves in accordance with forest protection regulations; establishment of nature reserves in currently unprotected natural forest patches elsewhere in line with the local government’s nature reserve expansion policy; and active natural-forest restoration between remaining fragments at Bawangling.     

Post-dispersal fate of hazel (Corylus avellana) nuts and consequences for the management and conservation of scrub-grassland mosaics

Granivorous rodents and birds are both predators and dispersers of the nuts produced by many woody plants. This study examines the role of granivores as predators and dispersers of Corylus avellana L. and the consequences of this interaction for Corylus regeneration and scrub encroachment into grassland. In the Cressbrook Dale nature reserve (Derbyshire, UK), Corylus nuts were buried in the grassland at two distances (<15 and >70 m) from scrub vegetation (the main source of nuts, and habitat of the granivores) to estimate the rate of seed removal over 3 years, assessing also the success of dispersal and seedling establishment in the grassland. The rate of nut removal at close sites (<15 m from scrub) was consistently higher than at far sites (>70 m) over the 3 years. All sown nuts were removed over 2 years at close sites, while at the far sites around 20% of the sown nuts were still present the following spring. Grassland close to the scrub had the highest intensity of nut predation but also had the highest density of Corylus seedlings. Sciurus carolinensis was the most important disperser of hazelnuts into the grassland. This squirrel scatter-hoarded 10-12 thousand hazelnuts in 1.5 ha of grassland adjacent to scrub. In this reserve, two vertebrates - both non-native - are largely responsible for maintaining the dynamic balance between the scrub and grassland habitats. American grey squirrels disperse hazelnuts into the grassland and sheep slow the encroachment of scrub by repeated browsing.     

Effect of forest fragmentation on fruit and seed predation of the tropical dry forest tree Ceiba aesculifolia

Forests fragmentation reduces the density of natural plant populations forming patches of the remaining individuals. One of the biotic interactions that can be affected by forest fragmentation and is poorly studied is seed predation. We determined the effects of forest fragmentation on seed and fruit predation in Ceiba aesculifolia by comparing trees in continuous forest with trees in fragmented forest. We compared the following variables: (a) frequency of fruit predation by Collie’s squirrel (Sciurus colliaei) in each habitat; (b) frequency of the cotton-staining bug seed predator (Dysdercus, Orden Hemiptera) in each habitat; (c) the effect of seed predation on germination frequency and time; and (d) the effect of different life stages of Dysdercus on seed viability. In continuous habitat, 100% of the trees presented fruits with squirrel predation while only 34% of trees in fragmented habitats presented fruit predation. In continuous forest 27% of the trees contained fruits with the seed predator Dysdercus, while only 2% of the trees in fragmented forest presented Dysdercus. The initial weight of damaged seeds was greater than seeds that were not damaged indicating that seed predators select heavier seeds to feed upon. Frequency of seed germination was affected by different life stages; pre-adults decreased germination significantly more than nymphs and adults. Seed predation significantly increased the time it took for germination to occur. Our study shows that forest fragmentation significantly affects predation patterns of squirrels and cotton-staining bugs. Reduction of natural seed predators in forest fragments may have long-term consequences on forest structure and diversity.     

Regional and local factors affecting diversity, abundance and activity of free-living, N2-fixing bacteria in Australian agricultural soils

N₂-fixation by free-living (diazotrophic) microorganism is a key process affecting ecosystem functioning in soils. Understanding drivers affecting diazotrophic community assemblages and activities may lead to management practices to increase primary production and/or environmental sustainability. We used PCR-DGGE to determine the fundamental relationships between diazotrophic community structure and in a wide range of soils across southern Australia. In addition qPCR, RT-qPCR and N₂-fixation (acetylene reduction) were used to investigate factors influencing gene abundance, expression and processes in similar soils with different agricultural inputs. Across 22 soils, the structural composition of the nifH community was significantly influenced by site (ANOSIM R = 0.876; P = 0.001). The effects of management practices were evident, and often larger than between-soil differences, but were only present at some sites. Differences in nifH communities between sites correlated to particulate organic carbon (POC; measured by mid-infrared spectroscopy) content of the soils (BIO-ENV test; ρ = 0.502; P = 0.001), but not other factors including total soil C. In 3 soils from the Murrumbidgee irrigation region of NSW, intensification of the farming systems was associated with increasing N₂-fixation (P < 0.05), except where rice was cultivated. N₂-fixation correlated either with nifH abundance or gene expression in soils, but not both. Our data shows that soil C is closely linked to diazotrophic ecology. Principally, the amount of C entering the soil system is directly related to the abundance and N₂-fixation activity of free-living bacteria. However, we also show that C in the POC pool has associative links to the genetic diversity of the soil diazotroph community. Given the importance of diversity and abundance of functional organisms in supporting ecosystem processes, we suggest that soil C inputs should be considered for both qualitative and quantitative properties when considering impacts on diazotrophic bacterial ecology.     

Uneven regional distribution of protected areas in Finland: Consequences for boreal forest bird populations

The significance of reserves in maintaining forest bird species of conservation concern (N = 36) was studied by large-scale quantitative line transect bird censuses in Finland, which stretches 1100 km through the boreal zone from the hemiboreal to the subarctic. Altogether 12 245 km of line transect was carried out in 1981-2004 in reserves covering 28 910 km². Bird census data in protected areas were combined into 100 km × 100 km squares. As a group the studied bird species were rather evenly distributed throughout the reserve network. The present reserve network is particularly significant for species having their highest densities in northern Finland, because large proportions of the populations of these species occurred in protected areas. However, over half of the studied species were concentrated in protected areas of southern and central Finland, and only small proportions of their populations were included in the present reserve network. In contrast to the whole species pool of conservation concern, the studied individual forest bird species were not distributed evenly throughout the whole reserve network. This suggests that for most individual species a regionally concentrated network is a preferred option, but for the whole species group the reserve network should clearly be regionally complementary and representative even in the boreal zone, where species have rather wide ranges. Thus, only some species and their habitats can be preserved in a spatially uneven reserve network in boreal forests.     

Seasonal changes in the spatial structures of N2O, CO2, and CH4 fluxes from Acacia mangium plantation soils in Indonesia

We evaluated the spatial structures of nitrous oxide (N₂O), carbon dioxide (CO₂), and methane (CH₄) fluxes in an Acacia mangium plantation stand in Sumatra, Indonesia, in drier (August) and wetter (March) seasons. A 60 × 100-m plot was established in an A. mangium plantation that included different topographical elements of the upper plateau, lower plateau, upper slope and foot slope. The plot was divided into 10 × 10-m grids and gas fluxes and soil properties were measured at 77 grid points at 10-m intervals within the plot. Spatial structures of the gas fluxes and soil properties were identified using geostatistical analyses. Averaged N₂O and CO₂ fluxes in the wetter season (1.85 mg N m⁻² d⁻¹ and 4.29 g C m⁻² d⁻¹, respectively) were significantly higher than those in the drier season (0.55 mg N m⁻² d⁻¹ and 2.73 g C m⁻² d⁻¹, respectively) and averaged CH₄ uptake rates in the drier season (−0.62 mg C m⁻² d⁻¹) were higher than those in the wetter season (−0.24 mg C m⁻² d⁻¹). These values of N₂O fluxes in A. mangium soils were higher than those reported for natural forest soils in Sumatra, while CO₂ and CH₄ fluxes were in the range of fluxes reported for natural forest soils. Seasonal differences in these gas fluxes appears to be controlled by soil water content and substrate availability due to differing precipitation and mineralization of litter between seasons. N₂O fluxes had strong spatial dependence with a range of about 18 m in both the drier and wetter seasons. Topography was associated with the N₂O fluxes in the wetter season with higher and lower fluxes on the foot slope and on the upper plateau, respectively, via controlling the anaerobic-aerobic conditions in the soils. In the drier season, however, we could not find obvious topographic influences on the spatial patterns of N₂O fluxes and they may have depended on litter amount distribution. CO₂ fluxes had no spatial dependence in both seasons, but the topographic influence was significant in the drier season with lowest fluxes on the foot slope, while there was no significant difference between topographic positions in the wetter season. The distributions of litter amount and soil organic matter were possibly associated with CO₂ fluxes through their effects on microbial activities and fine root distribution in this A. mangium plantation.     

Responses of soil organic matter and greenhouse gas fluxes to soil management and land use changes in a humid temperate region of southern Europe

We studied the effects of soil management and changes of land use on soils of three adjacent plots of cropland, pasture and oak (Quercus robur) forest. The pasture and the forest were established in part of the cropland, respectively, 20 and 40 yr before the study began. Soil organic matter (SOM) dynamics, water-filled pore space (WFPS), soil temperature, inorganic N and microbial C, as well as fluxes of CO₂, CH₄ and N₂O were measured in the plots over 25 months. The transformation of the cropland to mowed pasture slightly increased the soil organic and microbial C contents, whereas afforestation significantly increased these variables. The cropland and pasture soils showed low CH₄ uptake rates (<1 kg C ha⁻¹ yr⁻¹) and, coinciding with WFPS values >70%, episodes of CH₄ emission, which could be favoured by soil compaction. In the forest site, possibly because of the changes in soil structure and microbial activity, the soil always acted as a sink for CH₄ (4.7 kg C ha⁻¹ yr⁻¹). The N₂O releases at the cropland and pasture sites (2.7 and 4.8 kg N₂O-N ha⁻¹ yr⁻¹) were, respectively, 3 and 6 times higher than at the forest site (0.8 kg N₂O-N ha⁻¹ yr⁻¹). The highest N₂O emissions in the cultivated soils were related to fertilisation and slurry application, and always occurred when the WFPS >60%. These results show that the changes in soil properties as a consequence of the transformation of cropfield to intensive grassland do not imply substantial changes in SOM or in the dynamics of CH₄ and N₂O. On the contrary, afforestation resulted in increases in SOM content and CH₄ uptake, as well as decreases in N₂O emissions.     

Nitrous oxide emissions from boreal organic soil under different land-use

Nitrous oxide emissions were studied with a static chamber technique during 2 years from a drained organic soil in eastern Finland. After drainage, the soil was forested with birch (Betula pendula Roth) and 22 years later, part of the forest was felled and then used for cultivation of barley (Hordeum vulgare L.) and grass. The annual N₂O emissions from the cultivated soil (from 8.3 to 11.0 kg N₂O-N ha⁻¹ year⁻¹) were ca. twice the annual emission from the adjacent forest site (4.2 kg N₂O-N ha⁻¹ year⁻¹). The N₂O emissions from the soils without plants (kept bare by regular cutting or tilling) were also lower (from 6.5 to 7.1 kg N₂O-N ha⁻¹ year⁻¹) than those from the cultivated soil. There was a high seasonal variation in the fluxes with a maximum in spring and early summer. The N₂O fluxes during the winter period accounted for 15-60% of the total annual emissions. N₂O fluxes during the snow-free periods were related to the water table (WT) level, water-filled pore space, carbon mineralisation and the soil temperature. A linear regression model with CO₂ production, WT and soil temperature at the depth of 5 cm as independent variables explained 54% of the variation in the weekly mean N₂O fluxes during the snow-free periods. N₂O fluxes were associated with in situ net nitrification, which alone explained 58% of the variation in the mean N₂O fluxes during the snow-free period. The N₂O-N emissions were from 1.5 to 5% of net nitrification. The acetylene blockage technique indicated that most of the N₂O emitted in the snow-free period originated from denitrification.     

Characteristics of occupied habitats and identification of sites for restoration and translocation of New England cottontail populations

Since 1960 the range occupied by New England cottontails (NEC, Sylvilagus transitionalis) in the northeastern United States has declined dramatically. Populations in some regions are known to be vulnerable to extirpation, but little was known about the status of populations in most areas. A recently conducted (2000-2004) range-wide survey identified five disjunct populations within approximately 14% of the historic range of NEC. We incorporated the results of this survey into a geographic information system to examine habitat features associated with remnant populations of NEC at two spatial scales. The regional scale characterized habitats within our survey sample units, 7.5 min topographic quadrangles (quads, ∼40 × 10 km) that were occupied by NEC or vacant. The landscape scale described habitats within a 1-km radius of occupied patches and an equivalent sample of vacant patches. At the regional scale, northeastern and southeastern populations were associated with human-dominated habitats with a greater abundance of developed and disturbed lands, less forest coverage, more edge habitats, and less snow fall than unoccupied quads. Landscapes occupied by NEC in these regions were characterized by a greater abundance of potential dispersal corridors than unoccupied landscapes. In contrast, quads occupied by NEC in the southwestern portion of the historic range were in rural areas that were dominated by forests and agricultural fields. At the landscape scale, southwestern populations were affiliated patches of habitat surrounded by more agricultural lands than patches that were not occupied by NEC. Logistic regression models were then developed to identify habitats suitable for restoration or translocation within each region. We suggest that initial restoration efforts be directed toward expanding existing populations of NEC. Next, habitat connections should be developed among these populations. Finally, new populations should then be established via translocation in portions of the historic range that are vacant. In addition to promoting New England cottontails, management of early-successional and shrub-dominated habitats in the northeastern United States will benefit other taxa of conservation concern that are dependent on these habitats.     

Woodpeckers as reliable indicators of bird richness, forest health and harvest

Woodpeckers (family Picidae) show promise as indicators of avian diversity in forests because their populations can be reliably monitored, and their foraging and nesting activities can positively influence the abundance and richness of other forest birds. A correlation between woodpecker richness and richness of forest birds is known to exist at the landscape scale, but uncertainty remains whether this correlation occurs at the smaller stand-level spatial scales where forest management activities take place. We used data collected under a diverse range of forest types, harvest treatments, and forest health conditions during a long-term study of bird communities in interior British Columbia, Canada, to examine two basic questions: (1) at the level of individual forest stands, is woodpecker richness correlated with bird richness (measured as richness of all other bird species)? and (2) do woodpecker richness and bird richness have similar habitat correlates? Bird richness was positively correlated with woodpecker richness (β = 0.59, SE = 0.22, 95% CI = [0.14 1.03]). Richness of both woodpeckers and all other birds were positively correlated with tree species richness and negatively correlated with density of pines, and the effect for forest harvest type was similar for both measures of avian richness (uncut < partial harvest < clearcut with reserves). The effect of density of lodgepole pines killed by mountain pine beetles differed between the two richness measures, being positive for woodpecker richness and negative for forest bird richness. We conclude that the richness of woodpeckers is indeed correlated with the richness of other birds at the stand-level, and can serve as a reliable indicator of overall bird richness in most forest stands and conditions, except during insect outbreaks when differential responses by woodpeckers and the rest of the avian community may decouple the relationship between bird richness and woodpecker richness.     

Biodegradation of estrone and 17 β-estradiol in grassland soils amended with animal wastes

The release of endocrine disrupting chemicals into the environment is of increasing concern due to the formation of an intersex state in freshwater organisms and potential risks to human health. The aim of this study was to investigate the persistence of the naturally occurring hormones, estrone and 17 β-estradiol in three agricultural grassland soils in the presence and absence of cattle and sheep wastes (urine and manure). Biodegradation was investigated using ¹⁴C-labelled hormones which were applied to soil in three different solvents (water, artificial urine and natural sheep urine). When applied directly to soil the two hormones degraded at a similar rate, however, the speed of mineralization was soil type and solvent dependant. The half-life (t_1/2) of the hormones in soils ranged from 5 to 25 d. The hormones were also applied to the soils in sheep and cattle manure of different ages (7 d to 2 yr). Generally, the rate of degradation in the animal manure amended soils was more rapid than in the unamended soils (t_1/2=1-9 d), with mineralization being largely independent of manure age and type. We conclude that in comparison to many xenobiotics, estrogens are not persistent in agricultural soils. However, our calculations suggest that if they are lost to freshwater via runoff or leaching then they may have an appreciable effect on freshwater organisms. Assuming normal landspreading rates our results suggest that the risk of estrogen contamination of freshwater associated with manure spreading is very low.     

Relative fitness of wild and captive-reared piping plovers: Does egg salvage contribute to recovery of the endangered Great Lakes population?

Since 1992, efforts to recover the US federally endangered Great Lakes piping plover (Charadrius melodus) have included population supplementation with captive-reared young raised from abandoned eggs. Using banding data collected 1993-2008 and Cormack-Jolly-Seber models in program MARK we estimated resighting rates (ρ) and apparent survival (Φ) of first-year (1) and after-first-year (2+) plovers. Reproductive success was measured by estimating mean number of eggs laid, chicks hatched and chicks fledged per wild-reared or captive-reared parent, and these values were compared with a permutation test. The best-supported mark-resighting model indicated wild-reared plovers had higher Φ₁ and Φ₂₊ than captive-reared plovers. Breeding propensity influenced detection of wild plovers, whereas unique band combinations facilitated detection of yearling captive-reared plovers. Captive-reared (n = 10) and wild-reared (n = 57) plovers laid similar numbers of eggs, but wild-reared plovers hatched 36% more chicks and fledged 56% more young. Reproductive values derived from matrix models suggest captive-reared piping plovers are less fit than similarly aged wild-reared birds upon release and demonstrate reduced fitness in subsequent years. The Great Lakes captive-rearing effort has successfully produced a minimum of 10 breeding adults from 192 eggs that otherwise would have had no reproductive value; these captive-reared individuals now constitute up to 3% of the total population. Small scale salvage and captive-rearing of abandoned eggs should be considered as a technique to supplement existing recovery efforts in highly imperiled populations.     

The use of camera traps for estimating tiger and leopard populations in the high altitude mountains of Bhutan

We used camera traps in combination with capture-recapture data analysis to provide the first reliable density estimates for tigers and leopards from the high altitude and rugged terrain in Bhutan’s Jigme Singye Wangchuck National Park. Fifty days of camera trapping in each of five study zones collapsed into two trapping blocks, resulted in a sampling effort of 4050 trap days. Camera trapping yielded 17 tiger photos (14 left flanked and 3 right flanked) and 48 leopard photos (25 left flanked and 23 right flanked). Using photos of these left flank, the closed heterogeneous Jackknife Model M_h was the best fit for the capture history data. A capture probability () of 0.04 was obtained for both tigers and leopards, thus generating population size (N) of 8 tigers (SE = 2.12) and 16 leopards (SE = 2.91) with densities of 0.52 tiger 100 km⁻² and 1.04 leopard 100 km⁻². Photographic evidence indicated that tigers and leopards did not overlap in their spatial use of space. Tigers preferred less disturbed areas located further away from settlements, while leopards appeared to be more resilient to disturbances in so far as they were found nearer to human settlements. Camera trapping using a capture-recapture framework was an effective tool for assessing population sizes for tiger and leopard in low density areas such as Bhutan.     

The temperature dependence of dicyandiamide (DCD) degradation in soils: A data synthesis

Dicyandiamide (DCD, C₂H₄N₄) is a nitrification inhibitor that has been studied for more than 80 years. However, there are few papers that have examined the use of DCD on dairy farms where cattle graze pasture and where urine is the primary form of nitrogen (N) deposited onto soils. After DCD was applied (10 kg DCD ha^?1) with bovine urine (700–1200 kg N ha^?1) to five soils throughout New Zealand, the reduction in direct nitrous oxide (N₂O) emissions was significant and remarkably consistent (71 ± 8%, average ± standard error). The application of DCD to these soils occurred in autumn and winter; daily average soil temperature (T) was reported but these data were not further analysed. Perusal of the literature suggested no consensus on the temperature dependence of DCD degradation in soils. Based on published data from controlled-environment studies of soils sampled in four countries, we quantified the relation between T and the time for DCD concentration in soils to decline to half its application value (t_½) as t_½ (T) = 168e^?0.084T with parameter standard errors of ±16 d and ±0.011 d^?1, respectively (n = 16). For example, at 5 °C a 1 °C increase in T reduced t_½ from 110 to 101 d whereas at 25 °C the reduction was 20–19 d. Analysing T data from the New Zealand trials using our t_½ (T) function, over 43–89 d when direct N₂O emissions from treated plots became indistinguishable from the controls, the estimated percentage of applied DCD remaining in the soil averaged 43 ± 10%. These calculations suggested the apparently remaining DCD was ineffective with respect to direct N₂O emissions. In the absence of measurements, explanations for this interpretation included vertical displacement of the DCD and sorption onto organic matter in soils. The consistent DCD efficacy from these trials corresponded with T generally <10 °C, so it is suggested as an application criteria for the reduction of direct N₂O emissions from pastoral soils subjected to urine excretion by grazing cattle.