Decline in the distribution and abundance of flesh-footed shearwaters (Puffinus carneipes) on Lord Howe Island, Australia

The flesh-footed shearwater (Puffinus carneipes) is a migratory seabird that ranges widely across the Pacific and Indian Oceans. The principal breeding populations are in Australia and New Zealand. The only breeding site in eastern Australia is on Lord Howe Island. Despite it being afforded a high level of legislative protection, the population on Lord Howe Island has declined substantially during the last few decades. The total extent of nesting habitat in 2002 was 24.3 ha, a reduction of 13.4 ha (35.6%) since 1978. Loss of nesting habitat was associated with increased urbanisation, the adverse impact of which extended beyond the footprint of buildings and gardens. In 2002, overall burrow density was 0.123 per m² and the total number of burrows was estimated to be 29,853 ± 5867, a decline of about 19.0% since 1978. A substantial decline in burrow density was evident in the colony where loss of habitat to urbanisation had been greatest. In 2002, 58% of burrows were occupied by breeding birds, and the total population size was estimated to be 17,462 breeding pairs. Breeding success (the proportion of eggs that produced fledglings) was 50%, but was lowest in the most urbanised colony. To avert further declines in the population of flesh-footed shearwaters on Lord Howe Island major changes in land use practices, enforced through appropriate legislation, are needed, together with reductions in the level of seabird bycatch in fisheries operations and in the amount of plastics that litter the world’s oceans.     

Post-breeding season distribution of black-footed and Laysan albatrosses satellite-tagged in Alaska: Inter-specific differences in spatial overlap with North Pacific fisheries

We integrated satellite-tracking data from black-footed albatrosses (Phoebastria nigripes; n = 7) and Laysan albatrosses captured in Alaska (Phoebastria immutabilis; n = 18) with data on fishing effort and distribution from commercial fisheries in the North Pacific in order to assess potential risk from bycatch. Albatrosses were satellite-tagged at-sea in the Central Aleutian Islands, Alaska, and tracked during the post-breeding season, July-October 2005 and 2006. In Alaskan waters, fishing effort occurred almost exclusively within continental shelf and slope waters. Potential fishery interaction for black-footed albatrosses, which most often frequented shelf-slope waters, was greatest with sablefish (Anoplopoma fimbria) longline and pot fisheries and with the Pacific halibut (Hippoglossus stenolepsis) longline fishery. In contrast, Laysan albatrosses spent as much time over oceanic waters beyond the continental shelf and slope, thereby overlapping less with fisheries in Alaska than black-footed albatrosses. Regionally, Laysan albatrosses had the greatest potential fishery interaction with the Atka mackerel (Pleurogrammus monopterygius) trawl fishery in the Western Aleutian Islands and the sablefish pot fishery in the Central Aleutian Islands. Black-footed albatrosses ranged further beyond Alaskan waters than Laysan albatrosses, overlapping west coast Canada fisheries and pelagic longline fisheries in the subarctic transition domain; Laysan albatrosses remained north of these pelagic fisheries. Due to inter-specific differences in oceanic distribution and habitat use, the overlap of fisheries with the post-breeding distribution of black-footed albatrosses is greater than that for Laysan albatrosses, highlighting inter-specific differences in potential vulnerability to bycatch and risk of population-level impacts from fisheries.     

Risks of decline and extinction of the endangered Amsterdam albatross and the projected impact of long-line fisheries

The Amsterdam albatross (Diomedea amsterdamensis) is one of the rarest bird species of world avifauna, consisting of a single population in the upland plateau of Amsterdam Island (SE Indian Ocean). All breeding birds of the population are today banded and a monitoring program involving mark-recapture procedures has been carried out continuously over the past 16 years. We present the first estimate of risk of decline for the Amsterdam albatross using a stochastic matrix population model, and evaluate the extent to which the measurement errors in demographic estimates may affect the baseline conservation assessment. We also estimate the potential effect that resumption of long-line fisheries in the vicinity of Amsterdam Island (one the alleged causes for its low numbers in the recent past) may have on the persistence of this population. Our results indicate that, in the absence of any impact of long-line fisheries, the Amsterdam albatross is unlikely to experience a decline larger than 20% of the current population abundance over the next 50 years. Our results point out the difficulty to assess with certainty the extinction risk of small populations despite the availability of long term data on their demography. They suggest that a very cautious approach should be taken for the preservation of small populations of long-lived species that cannot sustain any level of incidental by-catch. Any new long-line fishery resuming in the foraging range of the Amsterdam albatross, but especially close to Amsterdam Island, may rapidly put this species at risk of extinction.     

The Prince Edward Islands: A sanctuary for seabirds in the Southern Ocean

This paper reviews the breeding distribution and numerical status of selected species of seabirds at 23 oceanic island groups in the Southern Ocean (between latitudes 35 and 70°S), based on census data and population estimates which have become available through increased scientific endeavour in the region during the last 15 years or so. The paper focuses on the avifauna of the Prince Edward islands, in the southern Indian Ocean, and points to the importance of these islands as a breeding station and sanctuary for seabirds. Only one oceanic island group, the Crozets, contains more species of breeding seabirds than the Prince Edward islands. Substantial segements (about 10% and greater) of the world breeding populations of the king and macaroni penguins, and the wandering, grey-headed, yellow-nosed and sooty albatrosses are based at the Prince Edward group. We recommend that Prince Edward Island (sensu stricto) should be a wilderness area, and that development at Marion Island should be kept to an absolute minimum.     

Population trends in a community of large Procellariiforms of Indian Ocean: Potential effects of environment and fisheries interactions

Despite the worrying conservation status of several albatross and petrel population, the long-term trends of many populations remain largely unknown and the causes of decline in many cases are known or very strongly suspected to be incidental mortality in fisheries. Here we combine long-term monitoring of population trends, breeding success and band recoveries to examine the past and current status of five species of albatrosses and giant petrels breeding at the same site: sooty albatross (Phoebetria fusca), light-mantled albatross (Phoebetria palpebrata), wandering albatross (Diomedea exulans), northern giant (Macronectes halli) and southern giant petrels (Macronectes giganteus) on Possession Island, Crozet archipelago. We identified three groups of trends over a 25-years period (1980-2005) suggesting common underlying causes for these species in relation to their bioclimatic foraging ranges. The Antarctic species - light-mantled albatross and southern giant petrel - appeared stable and increased recently, the Sub-Antarctic species - wandering albatross and northern giant petrel - declined with intermediate periods of increase, and finally the subtropical species - sooty albatross - declined all over the period. Breeding success, indicative of environmental conditions, showed two kinds of pattern (low and fluctuating versus high and/or increasing) which were consistent with oceanographic variations as found in a previous study. We present the analysis of fisheries-related recoveries, indicative of fisheries bycatch risks showing specific catch rates. No direct relationship between population trends and longline fishing effort was detected, probably because census data alone are not sufficient to capture the potentially complex response of demographic parameters of different life stages to environmental variation. This study highlights the contrasted changes of procellariiform species and the particularly worrying status of the subtropical sooty albatrosses, and in a lesser extent of Sub-Antarctic species.     

At-sea distribution of breeding Tristan albatrosses Diomedea dabbenena and potential interactions with pelagic longline fishing in the South Atlantic Ocean

The endangered Tristan albatross Diomedea dabbenena is restricted to Gough and Inaccessible Islands. The species is killed as bycatch by longline fisheries in the South Atlantic, but the impact of this mortality is unknown. We satellite tracked 38 breeding Tristan albatrosses and assessed the seasonal and annual at-sea distribution of these birds in relation to reported pelagic longline fishing effort. These birds ranged across the South Atlantic from 50°W to 15°E with most (97%) daytime satellite fixes between latitudes 30°S and 45°S. Considerable fishing effort occurred within the same latitudes. Although there was no correlation between their at-sea distributions, there was a broad overlap between birds and fishing effort. Estimated bycatch rates for Tristan albatross and other Diomedea species in the South Atlantic, and the spatio-temporal overlap between birds and hooks, yield a predicted annual mortality of 471-554 birds, sufficient to cause population decreases of 3.6-4.3% per year. An index of bird × hook interactions (proportional density of birds multiplied by number of hooks by decadal period for each 5° square of longitude and latitude) indicated that 47% of annual interactions occurred in areas around Gough Island, and 11% and 15% of interactions in areas of the west and east Atlantic, respectively. There were also within seasonal differences in the key areas of overlap. The fishing fleets of Taiwan and Japan are likely to be responsible for most interactions based upon the reported magnitude of effort expended in the South Atlantic by these fleets. Ensuring that licensed fishing vessels within the Tristan da Cunha Exclusive Economic Zone (EEZ) operate using best-practise mitigation measures and with fisheries observer programs, could reduce the potential bycatch mortality of breeding Tristan albatrosses in this region by nearly one third. Thorough implementation of international agreements is required in areas of the high seas where most remaining interactions are predicted to occur.     

Prey depletion caused by overfishing and the decline of marine megafauna in eastern Ionian Sea coastal waters (central Mediterranean)

Surveys primarily aimed at determining dolphin encounter rates were conducted from small inflatable craft in eastern Ionian Sea coastal waters between 1997 and 2004. During 633 surveys totalling 21,276 km of effort, observations of cetaceans and other marine species spotted in a study area of 480 km² were systematically recorded. Common dolphin encounter rates declined 25-fold across the study period, steadily decreasing from 2.18 encounters/100 km in 1997 to 0.09 encounters/100 km in 2004. Encounter rates of tuna also declined significantly. Swordfish encounter rates dropped from 1.03 encounters/100 km in 1997 to 0-0.12 in 1998-2004. Encounter rates of bottlenose dolphins did not show significant trends. The decline of high-order marine predators feeding on epipelagic prey was consistent with the hypothesis of prey depletion, likely resulting from intensive exploitation of local fish stocks, particularly anchovies and sardines. The catholic feeding habits and opportunistic behaviour of bottlenose dolphins may allow them to withstand the effects of overfishing at their present low density.     

Linking colonies to fisheries: Spatio-temporal overlap between common murres (Uria aalge) from Tatoosh Island and coastal gillnet fisheries in the Pacific Northwest, USA

The population-level impact of seabird bycatch is difficult to assess because colony-of-origin is often unknown. As an alternative and complementary approach to ship-derived observations, we assessed the relative potential for bycatch of a known seabird population by quantifying spatio-temporal overlap with local fisheries. Common murres (Uria aalge) have been reported as the most abundant seabird inadvertently caught in Washington and British Columbia coastal gillnet fisheries. In 1999-2001, we tracked 48 common murres from Tatoosh Island, the closest colony to the fisheries, during post-breeding. Using capture-mark-recapture models, we estimated weekly murre movement probabilities to/from three strata (offshore of, centered around, and inshore of Tatoosh Island). Based on movement probabilities and population size, we projected strata- and week-specific murre abundance. We created an index of overlap by calculating the product of murre abundance × gillnet fishing effort as a function of strata and time. The majority of murres (80%) moved inshore, where fishing effort was consistently the highest, suggesting that up to 4000 Tatoosh murres were vulnerable to bycatch. Index scores in the inshore stratum were 5-25 times higher relative to the offshore and Tatoosh strata, respectively. Overlap was sensitive to phenology, as index scores increased by 50% when dispersal was shifted four weeks earlier, while a two weeks delay decreased scores by 20%. Until the long-term impact of cumulative mortality in gillnet fisheries is determined, we believe a precautionary approach is warranted in the inshore stratum where the potential for bycatch was highest. We advocate the use of visible netting in inshore fisheries, a proven solution that reduces murre bycatch while maintaining fishing efficiency.     

Multi-trophic consequences of kelp harvest

Coastal kelp forest ecosystems provide important habitats for a diverse assemblage of invertebrates, fish and marine top-predators such as seabirds and sea mammals. Although kelp is harvested industrially on a worldwide scale little is known about the multi-trophic consequences of this habitat removal. We investigated how kelp fisheries, which remove feeding and nursery grounds of coastal fish, influence local food webs and the availability of food to a marine top predator, the great cormorant (Phalacrocorax carbo). We conducted experimental harvesting of the canopy-forming kelp (Laminaria hyperborea) during a 3 year period (2001-2003) in an area at the coast of Central Norway while synoptically monitoring fish occurrence and cormorant foraging parameters. Our results demonstrate that cormorants preferentially foraged within kelp-forested areas and performed significantly more dives when feeding in harvested versus un-harvested areas suggesting lower foraging yield in the former case. In kelp areas that were newly harvested the number of small (<15 cm) gadid fish was 92% lower than in un-harvested areas. This effect was persistent for at least 1 year following harvest. To our knowledge, this is the first time that the ecological consequences of kelp harvesting have been tested at a multi-trophic level. The results presented strongly suggest that kelp harvesting affects fish abundance and diminishes coastal seabird foraging efficiency. Kelp fisheries are currently managed in order to maximize the net harvest of kelp biomass, and the underlying effects on the ecosystems are partly ignored. This study calls for re-assessment of such management practices.     

Establishment of a new breeding colony of Gould’s petrel (Pterodroma leucoptera leucoptera) through the creation of artificial nesting habitat and the translocation of nestlings

Gould’s petrel (Pterodroma leucoptera leucoptera) was restricted, essentially, to a single breeding locality - Cabbage Tree Island, Australia. As a safeguard against extinction, an additional breeding colony was established on nearby Boondelbah Island, where artificial nesting habitat was created by installing 100 plastic nest boxes. Over two years, a total of 200 nestling Gould’s petrels were translocated from Cabbage Tree Island to these boxes. Colonies on both islands were then monitored for a further four years. Selection of nestlings for transfer was based on prior knowledge of growth, plumage development and emergence from the burrow, and aimed to select only birds that were 11-28 days from fledging (DBF) in 1999 and 11-22 DBF in 2000. Of the first 100 nestlings translocated to Boondelbah Island (in March 1999), 95 fledged successfully 8-27 days after transfer (mean = 17.3 days). Of the second 100 nestlings translocated (in March 2000) all successfully fledged 9-22 days after transfer (mean = 15.1 days). The removal of young had no discernible effect on the subsequent breeding productivity of the donor pairs. In all, 41 Gould’s petrels have been recorded at the new colony on Boondelbah Island, where at least 27 nest boxes have been visited. Ten translocated fledglings (nine male, one female) have returned to the translocation site, taking up nest boxes that were, on average, 5.5 m from the box from which they fledged. An additional 27 non-translocated birds, of unknown origin, have also nested in nest boxes on Boondelbah, along with four birds previously known from Cabbage Tree Island. Two nestlings transferred to Boondelbah Island have returned to Cabbage Tree Island. Within five years of the first translocation, the newly established colony on Boondelbah Island has produced a total of 24 eggs and 14 fledglings. The translocation technique developed for Gould’s petrel has broad applicability, being readily adaptable for other burrow-nesting seabirds.     

Predicting survival, reproduction and abundance of polar bears under climate change

Polar bear (Ursus maritimus) populations are predicted to be negatively affected by climate warming, but the timeframe and manner in which change to polar bear populations will occur remains unclear. Predictions incorporating climate change effects are necessary for proactive population management, the setting of optimal harvest quotas, and conservation status decisions. Such predictions are difficult to obtain from historic data directly because past and predicted environmental conditions differ substantially. Here, we explore how models can be used to predict polar bear population responses under climate change. We suggest the development of mechanistic models aimed at predicting reproduction and survival as a function of the environment. Such models can often be developed, parameterized, and tested under current environmental conditions. Model predictions for reproduction and survival under future conditions could then be input into demographic projection models to improve abundance predictions under climate change. We illustrate the approach using two examples. First, using an individual-based dynamic energy budget model, we estimate that 3-6% of adult males in Western Hudson Bay would die of starvation before the end of a 120 day summer fasting period but 28-48% would die if climate warming increases the fasting period to 180 days. Expected changes in survival are non-linear (sigmoid) as a function of fasting period length. Second, we use an encounter rate model to predict changes in female mating probability under sea ice area declines and declines in mate-searching efficiency due to habitat fragmentation. The model predicts that mating success will decline non-linearly if searching efficiency declines faster than habitat area, and increase non-linearly otherwise. Specifically for the Lancaster Sound population, we predict that female mating success would decline from 99% to 91% if searching efficiency declined twice as fast as sea ice area, and to 72% if searching efficiency declined four times as fast as area. Sea ice is a complex and dynamic habitat that is rapidly changing. Failure to incorporate climate change effects into population projections can result in flawed conservation assessments and management decisions.     

A global assessment of the impact of fisheries-related mortality on shy and white-capped albatrosses: Conservation implications

Hundreds of thousands of seabirds are killed each year as a result of interacting with longline and trawl fishing operations, and the severity of the impact varies regionally. Shy and white-capped albatrosses, Thalassarche cauta and Thalassarche steadi respectively, are phenotypically similar species known to be incidentally killed by fishing operations. The magnitude of this mortality has not previously been assessed across their range. Here we examine recent effort and bycatch rates in fisheries known to incidentally kill these species and qualitatively evaluate the level of impact of each fishery. Results indicate that over 8500 of these albatrosses may be killed annually, although the reliability of this estimate is low due to the paucity of comprehensive observer data in most fisheries. Of the estimated deaths of all seabird species in the fisheries assessed, trawl and longline fisheries killed birds in approximately equal proportions, but when the mortality levels of shy-type albatrosses were examined, trawl fisheries were responsible for 75% of all deaths. Data suggest most of these birds were killed in South African, Namibian and New Zealand demersal trawl fisheries and the South Africa pelagic longline fishery. Because most adult shy albatrosses are comparatively sedentary and rarely found outside Australian waters, it is primarily juvenile shy albatrosses that regularly encounter fishing fleets known to kill large numbers of albatrosses. In contrast, throughout most of their range juvenile and adult white-capped albatrosses are exposed to fisheries that collectively kill many thousands of these albatrosses each year. These data emphasise the urgent need for robust assessments of the impact of bycatch at a species and population level, and the urgent implementation of effective mitigation measures.     

Ingestion of fishing gear and entanglements of seabirds: Monitoring and implications for management

Fisheries are increasingly adopting ecosystem approaches to better manage impacts on non-target species. Although deliberate dumping of plastics at sea is banned, not all fisheries legislation prohibits discarding of gear (hooks and line) in offal, and compliance is often unknown. Analysis of a 16 year dataset collected at South Georgia indicated that the amount of gear found in association with wandering albatrosses was an order of magnitude greater than in any other species, reflecting their wider foraging range and larger gape. Unlike other taxa, most gear associated with grey-headed albatrosses was from squid and not longline fisheries, and mistaken for natural prey rather than the result of direct interaction. Observed rates of foul-hooking (entanglement during line-hauling) were much higher in giant petrels and wandering albatrosses than black-browed albatrosses, and no grey-headed albatross was affected. The index of wandering albatross gear abundance showed two peaks, the most recent corresponding with a substantial increase in the number of multifilament snoods (gangions), suggesting that the widespread adoption of a new longline system (Chilean mixed) may have been responsible. Although all identified gear was demersal, given the widespread use of similar hooks, little could be assigned to a specific fishery. Stomach content analysis suggested that 1300-2048 items of gear are currently consumed per annum by the wandering albatross population. Many hooks are completely digested by chicks, long-term effects of which are entirely unknown. We suggest a number of management approaches for addressing the problem of gear discarding, and guidelines for monitoring schemes elsewhere.     

Removal of introduced predators, but not artificial refuge supplementation, increases skink survival in coastal duneland

Exotic predators can have detrimental impacts on indigenous fauna. Lethal predator control is commonly used to reduce predator impacts, but is not always feasible, effective or ethical. A promising non-lethal alternative is refuge supplementation for prey. We conducted a Before-After Control-Impact (BACI) experiment over 3 years to determine the relative effects of predator removal (by exclosure fencing) and artificial refuge supplementation on survival of McCann’s skink (Oligosoma maccanni) in duneland on Kaitorete Spit (South Island, New Zealand). Skink populations on 0.0625 ha-grids were randomly assigned to four treatment groups, each replicated four times: (a) predator exclosure only; (b) artificial retreats only; (c) exclosure + artificial retreats, and (d) control (no exclosure or artificial retreats), and monitored annually by pitfall trapping. Capture-recapture analysis was used to estimate the difference in annual survival probability between pre- and post-treatment periods. On average, survival increased only at grids that received the exclosure-only treatment (effect size of 0.03 (0.017-0.043; unconditional 95% CI)). Reduction in predator abundance (by lethal predator control or predator exclusion), but not artificial refuge supplementation, is predicted to benefit McCann’s skink. Our findings add to other studies highlighting the detrimental impacts of exotic predators on indigenous prey and calls for improved means of reducing predator impacts.     

Conservation of the dark-rumped petrel Pterodroma phaeopygia in the Galapagos Islands,Ecuador

The effects of predation and habitat deterioration produced by rats, cats, dogs, pigs, goats, burros and cattle, which have been introduced over the last two centuries to the Galapagos archipelago, have reduced the dark-rumped petrel Pterodroma phaeopygia population so that it is now in danger of extinction. By controlling rat numbers through poisoning, and by protecting the nesting colony from other predator and pest species through hunting, petrel breeding success in the Cerro Pajas colony, Floreana Island, has been increased. Preliminary studies indicate that immediate conservation efforts are also needed and are being initiated for at least two other petrel populations. Continued predator control is essential to halt further petrel population declines and to allow their numbers to recuperate.     

From common to rare: The case of the Mediterranean common dolphin

Although overfishing has been recognized as responsible for the decline of major fish stocks, it has been less easy to demonstrate its indirect and detrimental effects on marine mammals, particularly dolphins. Competition with fisheries for the same food resources has been hypothesized to have led to the decline of several species of dolphins, including the endangered Mediterranean short-beaked common dolphin. Based on an ecosystem model for the Inner Ionian Sea Archipelago, a former hotspot for common dolphins in the Mediterranean Sea, we investigated the effect of increasing fishing effort on common dolphins, its prey and on marine biodiversity and we evaluated the outcomes of different fisheries closures (1 – closure of the purse seine fishery, 2 – closure of purse seine, trawl and beach seine fisheries, 3 – entire area closed to fisheries) ran between the years 2011 and 2030. Our results showed that local fisheries have negatively impacted the marine biodiversity of the ecosystem causing sharp declines of common dolphins and major fish stocks and weakening the robustness of the marine food web. The implementation of fisheries closures would gradually recover fish stocks, while common dolphins would increase more pronouncedly only if the study area was to be closed to all fisheries. As shown in this study, common dolphins have reflected ecosystem changes and degradation over time. Ensuring the survival of dolphin populations is thereby essential to enhance marine ecosystems and ensure sustainable fishing.     

Phosphorus fractionation in lowland tropical rainforest soils in central Panama

Phosphorus availability is commonly assumed to limit productivity in lowland tropical rainforests, yet there is relatively little information on the chemical forms of soil phosphorus in such ecosystems. We used the Hedley sequential fractionation scheme to assess phosphorus chemistry in five soils supporting tropical rainforest on Barro Colorado Island, Republic of Panama. The soils represented a range of orders (Inceptisols, Alfisols, and Oxisols) formed on contrasting geological substrates and topography, but under uniform climate and vegetation. Total phosphorus in surface horizons ranged between 315 and 1114 mg P kg^− 1, being lowest on a soil derived from marine sediments and highest on soils derived from andesite. The majority of the phosphorus occurred in recalcitrant forms, although between 14% and 39% occurred as organic phosphorus. Readily-available phosphate, as extracted by anion-exchange membranes, occurred in small concentrations (4–13 mg P kg^− 1), although labile phosphorus, defined as phosphate extracted by anion-exchange membrane plus inorganic and organic phosphorus extracted by 0.5 M NaHCO₃, accounted for between 4.7% and 11.4% of the total soil phosphorus. Our results indicate a strong control of geology and topography on soil phosphorus in tropical rainforests, which may have important implications for understanding the diversity and distribution of plant species in such ecosystems. Further, some of the most common soils on Barro Colorado Island, including those on the 50 ha forest dynamics plot, are rich in phosphorus despite their relatively advanced stage of pedogenesis.     

Long-term apparent survival of translocated gopher tortoises: A comparison of newly released and previously established animals

Most turtle species require high adult survivorship to maintain stable populations. Translocations are often implemented to conserve turtle populations but may cause demographic disturbance as a result of increased mortality or dispersal of released animals. The gopher tortoise (Gopherus polyphemus) is one of the most frequently translocated turtle species. Short-term monitoring indicates that dispersal by released tortoises is common, but few long-term data are available to determine if losses of translocated animals continue for multiple years. We used 12 years of mark-recapture data to investigate long-term apparent survival of two groups of gopher tortoises translocated during separate periods to St. Catherines Island, Georgia, USA. We analyzed capture histories in program MARK to compare apparent survival of newly released tortoises and previously established translocated tortoises and also to determine whether apparent survival varied with sex or maturity. Apparent annual survival did not vary between adult males and females (0.98 ± 0.01), but was lower in sexually immature tortoises (0.84 ± 0.05). We documented a temporary reduction in apparent survival of newly released adult (0.75 ± 0.06) and immature tortoises (0.45 ± 0.26) during the first year after release that may be attributed in part to permanent dispersal. However, for both maturity classes, apparent survival of newly released tortoises was consistently high and matched that of previously established animals during the remainder of the study. Additional long-term studies of both translocated and naturally-occurring populations are needed to improve management of remaining tortoise populations.     

Temperature sensitivity of soil respiration in different ecosystems in China

Understanding the sensitivity of soil respiration to temperature change and its impacting factors is an important base for accurately evaluating the response of terrestrial carbon balance to future climatic change, and thus has received much recent attention. In this study, we synthesized 161 field measurement data from 52 published papers to quantify temperature sensitivity of soil respiration in different Chinese ecosystems and its relationship with climate factors, such as temperature and precipitation. The results show that the observed Q₁₀ value (the factor by which respiration rates increase for a 10 °C increase in temperature) is strongly dependent on the soil temperature measurement depth. Generally, Q₁₀ significantly increased with the depth (0 cm, 5 cm, and 10 cm) of soil temperature measuring point. Different ecosystem types also exhibit different Q₁₀ values. In response to soil temperature at the depth of 5 cm, alpine meadow and tundra has the largest Q₁₀ value with magnitude of 3.05 ± 1.06, while the Q₁₀ value of evergreen broadleaf forests is approximately half that amount (Q₁₀ = 1.81 ± 0.43). Spatial correlation analysis also shows that the Q₁₀ value of forest ecosystems is significantly and negatively correlated with mean annual temperature (R = −0.51, P < 0.001) and mean annual precipitation (R = −0.5, P < 0.001). This result not only implies that the temperature sensitivity of soil respiration will decline under continued global warming, but also suggests that such acclimation of soil respiration to warming should be taken into account in forecasting future terrestrial carbon cycle and its feedback to climate system.