Entire Annual Cycle Research Articles

Horseflies, wolves and wells: biophysical and socio-economic factors influencing livestock distribution in Kazakhstan’s rangelands

There have been studies on how pastoralists assess and choose the resources required for their livestock, but little research analysing whether livestock are matched to the available resources in a seasonal migratory system by an entire pastoral community over a year. This paper reports a case study of pastoralists in Kazakhstan which shows how the inter-relation of biophysical, institutional and economic factors results in the imperfect matching of livestock numbers to the distribution of forage resources. The research is based on a three-year study using anthropological interviews, formal survey data, and remotely sensed data covering all livestock (25,000 smallstock and approximately 2300 cattle, horses and camels) in a study area of 60,000km2 for an entire annual cycle; a combination of methodologies and geographical coverage that provides a comprehensive estimation of the factors that influence the pastoral exploitation of this human-managed, complex ecosystem. The research finds that the pastoralists are subject to a number of limitations in using biophysical niches which might otherwise provide the best feed and water resources for their animals at a particular season and site. Different ecozones offer seasonally-shifting advantages and disadvantages for the livestock, but livestock owners are also economically differentiated. The interplay between economic and biophysical factors exemplifies the multi-faceted character of pastoralists’ decision-making about site selection within a relatively open rangeland tenure system. Only those with the largest livestock holdings distribute their livestock to take advantage of the best seasonal resources. Despite the wide availability of biophysically suitable sites, most livestock owners’ choices are compromised and therefore frequently suboptimal, prompting the conclusion that natural resource matching is constrained.

Future ocean hypercapnia driven by anthropogenic amplification of the natural CO2 cycle.

High carbon dioxide (CO2) concentrations in sea-water (ocean hypercapnia) can induce neurological, physiological and behavioural deficiencies in marine animals. Prediction of the onset and evolution of hypercapnia in the ocean requires a good understanding of annual variations in oceanic CO2 concentration, but there is a lack of relevant global observational data. Here we identify global ocean patterns of monthly variability in carbon concentration using observations that allow us to examine the evolution of surface-ocean CO2 levels over the entire annual cycle under increasing atmospheric CO2 concentrations. We predict that the present-day amplitude of the natural oscillations in oceanic CO2 concentration will be amplified by up to tenfold in some regions by 2100, if atmospheric CO2 concentrations continue to rise throughout this century (according to the RCP8.5 scenario of the Intergovernmental Panel on Climate Change). The findings from our data are broadly consistent with projections from Earth system climate models. Our predicted amplification of the annual CO2 cycle displays distinct global patterns that may expose major fisheries in the Southern, Pacific and North Atlantic oceans to hypercapnia many decades earlier than is expected from average atmospheric CO2 concentrations. We suggest that these ocean 'CO2 hotspots' evolve as a combination of the strong seasonal dynamics of CO2 concentration and the long-term effective storage of anthropogenic CO2 in the oceans that lowers the buffer capacity in these regions, causing a nonlinear amplification of CO2 concentration over the annual cycle. The onset of ocean hypercapnia (when the partial pressure of CO2 in sea-water exceeds 1,000 micro-atmospheres) is forecast for atmospheric CO2 concentrations that exceed 650 parts per million, with hypercapnia expected in up to half the surface ocean by 2100, assuming a high-emissions scenario (RCP8.5). Such extensive ocean hypercapnia has detrimental implications for fisheries during the twenty-first century.

Investigating the annual behaviour of submicron secondary inorganic and organic aerosols in London

Abstract. For the first time, the behaviour of non-refractory inorganic and organic submicron particulate through an entire annual cycle is investigated using measurements from an Aerodyne compact time-of-flight aerosol mass spectrometer (cToF-AMS) located at a UK urban background site in North Kensington, London. We show that secondary aerosols account for a significant fraction of the submicron aerosol burden and that high concentration events are governed by different factors depending on season. Furthermore, we demonstrate that on an annual basis there is no variability in the extent of secondary organic aerosol (SOA) oxidation, as defined by the oxygen content, irrespective of amount. This result is surprising given the changes in precursor emissions and contributions as well as photochemical activity throughout the year; however it may make the characterisation of SOA in urban environments more straightforward than previously supposed. Organic species, nitrate, sulphate, ammonium, and chloride were measured during 2012 with average concentrations (±1 standard deviation) of 4.32 (±4.42), 2.74 (±5.00), 1.39 (±1.34), 1.30 (±1.52), and 0.15 (±0.24) μg m−3, contributing 44, 28, 14, 13, and 2 % to the total non-refractory submicron mass (NR-PM1) respectively. Components of the organic aerosol fraction are determined using positive matrix factorisation (PMF), in which five factors are identified and attributed as hydrocarbon-like OA (HOA), cooking OA (COA), solid fuel OA (SFOA), type 1 oxygenated OA (OOA1), and type 2 oxygenated OA (OOA2). OOA1 and OOA2 represent more and less oxygenated OA with average concentrations of 1.27 (±1.49) and 0.14 (±0.29) μg m−3 respectively, where OOA1 dominates the SOA fraction (90%). Diurnal, monthly, and seasonal trends are observed in all organic and inorganic species due to meteorological conditions, specific nature of the aerosols, and availability of precursors. Regional and transboundary pollution as well as other individual pollution events influence London's total submicron aerosol burden. High concentrations of non-refractory submicron aerosols in London are governed by particulate emissions in winter, especially nitrate and SFOA, whereas SOA formation drives the high concentrations during the summer. The findings from this work could have significant implications for modelling of urban air pollution as well as for the effects of atmospheric aerosols on health and climate.

Prolonged stopover duration characterises migration strategy and constraints of a long-distance migrant songbird

AbstractStopover behaviour is a central element of migration strategies. But in recent geolocator studies, despite now being able to track individual songbirds during their entire migration, their stopover behaviour has received little attention. We used light-sensitive geolocators to identify the migratory routes and schedules of 12 northern wheatears (Oenanthe oenanthe) breeding in Sweden. Three geolocators collected temperature data complementing inferences from light data by providing additional information on behaviour during migration. The wheatears performed a slow migration with considerable stopover time (84%/76% of autumn/spring migration), with short stops while traveling through Europe, and a prolonged stopover period in both autumn and spring in the Mediterranean region. Spring migration was faster than autumn migration, mainly because of decreased stopover time. Migration routes and time schedules were similar to those from a German breeding population. Compared to wheatears breeding in Alaska with a three-fold migration distance, Swedish wheatears spent more time during stopovers during autumn and spring migration, suggesting less time constraints and potential flexibility in migration schedules. The finding of prolonged stopovers, similar to other recent geolocator studies, shows that temporary residency periods may be common. This changes our current view on stopover ecology to one where temporary residency periods are part of spatio-temporal strategies optimising resource use during the entire annual cycle.

Spatial ecotoxicology: migratory Arctic seabirds are exposed to mercury contamination while overwintering in the northwest Atlantic.

Arctic organisms are exposed to various levels of pollutants, among which mercury (Hg) has raised important environmental concerns. Previous studies examining Hg levels, trends, and effects on Arctic marine top predators have focused on the Arctic region. However, many of these top predators, such as seabirds, migrate to spend a large part of their life cycle far from the Arctic in areas where their exposure to contaminants is largely unknown. By combining biotelemetry and Hg and stable isotope analyses, we studied the seasonal Hg contamination of little auks (Alle alle, the most abundant Arctic seabird) in relation to their distribution and marine foraging habitat, as well as its potential impacts on bird reproduction. We show that little auks were ∼ 3.5 times more contaminated when outside the breeding season, and that Hg that accumulated during this nonbreeding non-Arctic period was related to egg size the following season, with females having more Hg laying smaller eggs. Our results highlight that ecotoxicological studies should be expanded to yield a comprehensive understanding of contamination risks and associated threats to top predators over their entire annual cycle. Furthermore, we show that an important nonbreeding area located in the northwest Atlantic was associated with greater Hg contamination and demonstrate the utility of bird-borne miniaturized technology for evaluating the contamination of marine systems on large spatial scales.

Seasonal phenotypic flexibility of body mass, organ masses, and tissue oxidative capacity and their relationship to resting metabolic rate in Chinese bulbuls.

Survival of small birds in fluctuating environments is facilitated by seasonal metabolic and morphological flexibility. Chinese bulbuls Pycnonotus sinensis show winter increases in resting metabolic rate (RMR), nutritional organ masses, and liver and muscle cellular aerobic capacity relative to summer. In this study, we build on these findings from previous studies by measuring seasonal adjustments in body mass (Mb), RMR, nutritional and exercise organ masses, and several physiological, biochemical, and hormonal markers over the entire annual cycle in wild-trapped Chinese bulbuls from Wenzhou, China. Furthermore, we analyzed the relationships between variation in organ masses and cellular aerobic capacity and variation in RMR in individual birds. Mb and RMR were higher in spring (March-May) and winter (December-February) than in summer (June-August). The dry masses of several nutritional organs and mitochondrial protein content, state 4 respiration, and cytochrome c oxidase (COX) activity in liver and muscle were all heightened in winter relative to other seasons. In addition, dry masses of heart and pectoral muscle, but not nutritional organs, and biochemical markers of cellular aerobic capacity in liver and muscle were positively correlated with RMR. Plasma triiodothyronine (T3) concentration was higher in winter and spring than in summer and autumn, and it was positively correlated with RMR, mitochondrial protein content, state 4 respiration, and COX activity in liver and muscle. These results suggest that seasonal changes in nutritional and exercise organ masses and liver and muscle cellular aerobic capacity interact to promote seasonal metabolic flexibility in Chinese bulbuls. T3 appears to promote these seasonal thermoregulatory adjustments.

Climate change and annual survival in a temperate passerine: partitioning seasonal effects and predicting future patterns

Predicting climate change impacts on population size requires detailed understanding of how climate influences key demographic rates, such as survival. This knowledge is frequently unavailable, even in well‐studied taxa such as birds. In temperate regions, most research into climatic effects on annual survival in resident passerines has focussed on winter temperature. Few studies have investigated potential precipitation effects and most assume little impact of breeding season weather. We use a 19‐year capture–mark–recapture study to provide a rare empirical analysis of how variation in temperature and precipitation throughout the entire year influences adult annual survival in a temperate passerine, the long‐tailed tit Aegithalos caudatus. We use model averaging to predict longer‐term historical survival rates, and future survival until the year 2100. Our model explains 73% of the interannual variation in survival rates. In contrast to current theory, we find a strong precipitation effect and no effect of variation in winter weather on adult annual survival, which is correlated most strongly to breeding season (spring) weather. Warm springs and autumns increase annual survival, but wet springs reduce survival and alter the form of the relationship between spring temperature and annual survival. There is little evidence for density dependence across the observed variation in population size. Using our model to estimate historical survival rates indicates that recent spring warming has led to an upward trend in survival rates, which has probably contributed to the observed long‐term increase in the UK long‐tailed tit population. Future climate change is predicted to further increase survival, under a broad range of carbon emissions scenarios and probabilistic climate change outcomes, even if precipitation increases substantially. We demonstrate the importance of considering weather over the entire annual cycle, and of considering precipitation and temperature in combination, in order to develop robust predictive models of demographic responses to climate change.SynthesisPrediction of climate change impacts demands understanding of how climate influences key demographic rates. In our 19‐year mark‐recapture study of long‐tailed tits Aegithalos caudatus, weather explained 73% of the inter‐annual variation in adult survival; warm springs and autumns increased survival, wet springs reduced survival, but winter weather had little effect. Robust predictions thus require consideration of the entire annual cycle and should not focus solely on temperature. Unexpectedly, survival appeared not to be strongly density‐dependent, so we use historical climate data to infer that recent climate change has enhanced survival over the four decades in which the UK long‐tailed tit population has more than doubled. Furthermore, survival rates in this species are predicted to further increase under a wide range of future climate scenarios.

Contrasting recruitment seasonality of sea urchin species in Gran Canaria, Canary Islands (eastern Atlantic)

Despite sea-urchins can play an important role affecting the community structure of subtidal bottoms, factors controlling the dynamics of sea-urchin populations are still poorly understood. We assessed the seasonal variation in recruitment of three sea-urchin species (Diadema africanum, Paracentrotus lividus and Arbacia lixula) at Gran Canaria Island (eastern Atlantic) via monthly deployment of artificial collectors throughout an entire annual cycle on each of four adjacent habitat patches (seagrasses, sandy patches, ‘urchin-grazed’ barrens and macroalgal-dominated beds) within a shallow coastal landscape. Paracentrotus lividus and A. lixula had exclusively one main recruitment peak in late winter-spring. Diadema africanum recruitment was also seasonal, but recruits appeared in late summer-autumn, particularly on ‘urchin-grazed’ barrens with large abundances of adult conspecifics. In conclusion, this study has demonstrated non-overlapping seasonal recruitment patterns of the less abundant species (P. lividus and A. lixula) with the most conspicuous species (D. africanum) in the study area.

Abundance and biomass of the parrotfish Sparisoma cretense in seagrass meadows: temporal and spatial differences between seagrass interiors and seagrass adjacent to reefs

Seagrass habitats are relevant for numerous nearshore fish species, particularly as nursery grounds. Seagrass meadows are often interspersed with other habitats, what can alter the distribution and abundance of seagrass ichthyofauna. This research aimed to determine whether there is a change in the abundance and biomass of the parrotfish, Sparisoma cretense, in seagrass meadows (Cymodocea nodosa) with varying proximity from rocky reefs, specifically seagrass interiors (>200 m away from reefs) vs. seagrass adjacent to reefs (<10 m away). Sampling was undertaken using a seine net and underwater visual census through an entire annual cycle. Adults were predominantly observed in seagrass adjacent to reefs, which seem to be restricted to incursions of large-sized parrotfish from adjacent reefs. Juvenile abundance did not significantly differ between seagrass interiors and seagrass adjacent to reefs; however, juvenile biomass was greater in seagrass meadows adjacent to reefs compared to those far away from reefs. This pattern was consistent through times for both sampling techniques. These results suggest a transition of juvenile parrotfish from seagrass interiors to seagrass near reefs, so juveniles are located in the vicinity of their adult habitat, i.e. rocky reefs.

Colonization of Prosobranch Gastropods onto Artificial Substrates: Seasonal Patterns between Habitat Patches

Abstract: We used artificial substrates to investigate the seasonal variation in colonization patterns of subtidal prosobranch gastropods in Gran Canaria (Canary Island, Spain, north-eastern Atlantic), via monthly deployment of artificial substrates throughout an entire annual cycle from February 2009 to January 2010, on each of four habitat patches (seagrasses, sandy patches, ‘urchin-grazed’ barrens and macroalgaldominated beds) within a coastal landscape. A total of 8,524 prosobranch gastropods, including 12 dominant taxa, were collected as postlarval, juvenile, and adult individuals. In general the amount of variability explained by the type of habitat slightly dominated over seasonal variation, which was outweighed by variation from month to month, to explain colonization patterns. Throughout the study, larger numbers of colonizers of Bittium spp. (Leach in Gray, 1847), Columbella adansoni (Menke, 1853), Gibberula caelata (Monterosato, 1877), Mitra spp. (Lamarck, 1798), Rissoa spp. (Freminville in Des...

Assessing algal biomass and bio-optical distributions in perennially ice-covered polar ocean ecosystems

Under-ice observations of algal biomass and seasonality are critical for understanding better how climate-driven changes affect polar ocean ecosystems. However, seasonal and interannual variability in algal biomass has been studied sparsely in perennially ice-covered polar ocean regions. To address this gap in polar ocean observing, bio-optical sensors for measuring chlorophyll fluorescence, optical scattering, dissolved organic matter fluorescence, and incident solar radiation were integrated into Ice-Tethered Profilers (ITPs). Eight such systems have been deployed in the Arctic Ocean, with five profilers completing their deployments to date including two that observed an entire annual cycle in the central Arctic Ocean and Beaufort Sea respectively. These time series revealed basic seasonal differences in the vertical distributions of algal biomass and related bio-optical properties in these two regions of the Arctic Ocean. Because they conduct profiles on daily or sub-daily scales, ITP bio-optical data allow more accurate assessments of the timing of changes in under-ice algal biomass such as the onset of the growing season in the water column, the subsequent export of particulate organic matter at the end, and the frequency of intermittent perturbations, which in the central Arctic Ocean were observed to have time scales of between one and two weeks.

Circannual body reserve dynamics and metabolic profile changes in Romane ewes grazing on rangelands

Throughout an entire year, 41 Romane ewes reared in an extensive rangeland were used to investigate temporal changes in body reserves (BRs) and profiles of related metabolites and metabolic hormones. Ewes were allocated to homogeneous groups according to BW and BCS and were distributed by parity (primiparous [PRIM], n = 21; multiparous [MULT], n = 20) and litter size (LSi; lambing singletons [SING], n = 21 or TWINS, n = 20). The feeding system was based on rotational grazing of rangeland paddocks and progressive supplementation with hay, silage, and barley at late pregnancy during the winter. Individual BW, BCS, plasma NEFA, β-hydroxybutyrate (β-OHB), glucose, insulin, leptin, and triiodothyronine (T3) were monitored at −56, −12, 8, 49, 76, 107, 156, 195, 216, 246, and 301 d relative to lambing. The BR mobilization was observed from late pregnancy to the end of suckling and varied as a function of the ewe energy balance but also because of transitions from fertilized to native rangeland paddocks and by supplementation. Contrarily, BR accretion occurred from weaning, during the dry-off, and until the start of the next pregnancy. Lipolysis was well reflected by NEFA, β-OHB, and T3 kinetics. Mean BW (but not mean BCS) was affected by parity (MULT > PRIM), whereas both BW and BCS were influenced by LSi (SING > TWINS) but only for MULT. The most drastic BW loss was observed during the mid-suckling period (49 d in milk [DIM]) in all ewes. The lack of effects of LSi in PRIM but not in MULT was also evident in the majority of blood plasma kinetics, which were affected (P < 0.0001) by physiological stage in all ewes. A tendency to ketosis (β-OHB) was found in ewes nursing TWINS around lambing, irrespective of parity. Glucose concentrations were greater during suckling and dry-off, and a peak (0.96 ± 0.05 g/L) was attained at 156 DIM in MULT nursing TWINS. The highest plasma leptin concentration was observed during the start and the middle of the next pregnancy in MULT (107–216 DIM; 9.6 ± 0.44 ng/mL). In all ewes the physiological stage affected T3, which was affected by LSi just in MULT (from late pregnancy, MULT by SING > MULT by TWINS; 99.91 vs 85.52 ng/dL) and during suckling (111.7 ± 4.18 ng/dL). Lamb BW was affected at birth and weaning by parity (MULT > PRIM) and LSi (SING > TWINS). Overall, temporal changes in BR were directly affected by the transition of physiological states and feeding levels, whereas individual responses were predetermined by parity. In MULT, the reactivity and magnitude of response was influenced by LSi. The whole set of parameters allowed us to detect sensitive and critical periods throughout the entire annual cycle. We thus identified opportunities for improved nutritional management, for example, during physiological states usually underestimated such as early and mid-pregnancy. This work indicates the applicability of long-term studies about BR dynamics in ruminants as a potential component contributing to farm economic resilience.

Evapotranspiration of a high-density poplar stand in comparison with a reference grass cover in the Czech–Moravian Highlands

This study reports on 3.5 years (2008–2011) of actual evapotranspiration (ET) measurements of two short-rotation poplar coppice (SRC) plantations in comparison with two reference grass covers (clipped turf grass and permanent grassland) in a rain-fed area of the Czech–Moravian Highlands in the Czech Republic. The Bowen ratio/energy balance method (BREB) was used to measure the ET of all the four investigated covers. Although the ET of the SRCs sometimes exceeded that of grass vegetation or the reference evapotranspiration (ET0) on an hourly, daily or monthly time scale, it was always lower over an entire annual cycle. The cumulative annual ET of the SRCs ranged from 344 to 549mmyear−1, whereas that of the turf grass ranged from 561 to 573mmyear−1, and the ET of the grassland reached up to 619mmyear−1. The wide range of the annual ET totals for the SRCs was determined mainly by the different rotation periods and ages of the stands, along with the leaf area index (LAI), the state of the canopy closure, and tree heights. The lowest annual ET (344mm) was observed during the 1st year of the 2nd rotation (following the winter harvest) in 2010. During that year, the SRC regrowth started only after mid-June, and the maximum LAI of the canopy, which was approximately 2m in height and was not completely closed, reached 3.7. In contrast, in the case of a mature stand approximately 12m in height in 2009, i.e., the 8th year of the 1st rotation, the maximum canopy LAI reached 7.5, and the annual ET reached its highest observed value (549mm). The leaf area duration of the SRCs was always lower than that of the grass covers, and this seemed to be the main reason for the significantly lower annual ET totals of the SRCs. The absolute maximum daily ET of 6.3mmday−1 was achieved by the SRC in July 2011 when the stand was in the 2nd year of the 2nd rotation cycle. The highest daily ET of the grass covers (5.9mmday−1) was reached by turf grass in June 2011. The maximum monthly ET occurred in July 2009 when the weather was wet and relatively warm; the ET was identical for the SRCs and the turf grass, reaching 107mmmonth−1, just slightly lower than the ET0 (109mmmonth−1). These results are in the middle range of ET values from 21 recent studies on poplar and willow cultures. The results of this study indicate that conversion of arable land into poplar SRCs instead of grasslands does not result in significant differences in ET of the agricultural landscape.

Horizontal water vapor transport in the lower stratosphere from subtropics to high latitudes during boreal summer

We compare global water vapor observations from Microwave Limb Sounder (MLS) and simulations with the Lagrangian chemical transport model CLaMS (Chemical Lagrangian Model of the Stratosphere) to investigate the pathways of water vapor into the lower stratosphere during Northern Hemisphere (NH) summer. We find good agreement between the simulation and observations, with an effect of the satellite averaging kernel especially at high latitudes. The Asian and American monsoons emerge as regions of particularly high water vapor mixing ratios in the lower stratosphere during boreal summer. In NH midlatitudes and high latitudes, a clear anticorrelation between water vapor and ozone daily tendencies reveals a large region influenced by frequent horizontal transport from low latitudes, extending up to about 450K during summer and fall. Analysis of the zonal mean tracer continuity equation shows that close to the subtropics, this horizontal transport is mainly caused by the residual circulation. In contrast, at higher latitudes, poleward of about 50°N, eddy mixing dominates the horizontal water vapor transport. Model simulations with transport barriers confirm that almost the entire annual cycle of water vapor in NH midlatitudes above about 360K, with maximum mixing ratios during summer and fall, is caused by horizontal transport from low latitudes. In the model, highest water vapor mixing ratios in this region are clearly linked to horizontal transport from the subtropics.

ANNUAL AND INTRA-ANNUAL WATER BALANCE COMPONENTS OF A SHORT ROTATION POPLAR COPPICE BASED ON SAP FLOW AND MICROMETEOROLOGICAL AND HYDROLOGICAL APPROACHES

Comparative measurements of canopy transpiration (T) and evapotranspiration (ET) of a high density poplar stand were conducted in a typical rain-fed area of the Czech Moravian Highlands, Czech Republic, during 2012. Higher mean annual temperature, lower precipitation and period with drought occurred in this year. Sap flow measured on four sample trees was scaled to T and successfully validated by ET measured by Bowen ratio energy balance method. Since the sap flow measurements were available from June to September, a stomatal conductance model and leaf area measurements were used to predict annual T. It was found that when stomatal conductance is scaled to the canopy, a non-linear relationship between LAI and canopy conductance has to be taken into account. An increase of LAI from 0 to 3 had the most important impact on canopy transpiration. Apart from T and ET, interception was assessed by measuring rainfall at open area, canopy throughfall and stemflow. The ET of the understory and soil evaporation was finally estimated as the residual of ET. Maximum daily T and ET was 4.5 and 5.7 mm day -1 , respectively, whereas maximum reference evapotranspiration (ETo) was 6.6 mm day -1 . Over the entire annual cycle cumulative ET totalled 572 mm, T was 347 mm, soil and understory ET was 176 mm, and interception was 49 mm. Rainfall totalled 568 mm while ETo was 681 mm. The results of this study provide promising material for further up-scaling of poplar short rotation coppice water use in other climatic regions or in future climate conditions.

Temperature response of soil respiration in a Chinese pine plantation: hysteresis and seasonal vs. diel Q10.

Although the temperature response of soil respiration (Rs) has been studied extensively, several issues remain unresolved, including hysteresis in the Rs–temperature relationship and differences in the long- vs. short-term Rs sensitivity to temperature. Progress on these issues will contribute to reduced uncertainties in carbon cycle modeling. We monitored soil CO2 efflux with an automated chamber system in a Pinus tabulaeformis plantation near Beijing throughout 2011. Soil temperature at 10-cm depth (Ts) exerted a strong control over Rs, with the annual temperature sensitivity (Q 10) and basal rate at 10°C (Rs 10) being 2.76 and 1.40 µmol m−2 s−1, respectively. Both Rs and short-term (i.e., daily) estimates of Rs 10 showed pronounced seasonal hysteresis with respect to Ts, with the efflux in the second half of the year being larger than that early in the season for a given temperature. The hysteresis may be associated with the confounding effects of microbial population dynamics and/or litter input. As a result, all of the applied regression models failed to yield unbiased estimates of Rs over the entire annual cycle. Lags between Rs and Ts were observed at the diel scale in the early and late growing season, but not in summer. The seasonality in these lags may be due to the use of a single Ts measurement depth, which failed to represent seasonal changes in the depth of CO2 production. Daily estimates of Q 10 averaged 2.04, smaller than the value obtained from the seasonal relationship. In addition, daily Q 10 decreased with increasing Ts, which may contribute feedback to the climate system under global warming scenarios. The use of a fixed, universal Q 10 is considered adequate when modeling annual carbon budgets across large spatial extents. In contrast, a seasonally-varying, environmentally-controlled Q 10 should be used when short-term accuracy is required.

Incisor growth rate in rodents and the record of the entire annual cycle in the incisors of Marmota baibacina centralis

The lower incisors of 80 specimens of Marmota baibacina of 1–10 years old killed in spring in the highland of the Tien Shan Mountains were investigated. On the surface of all the incisors, regular daily increments and “hibernation zones” were revealed. The mean width of increments was used as an indicator of the incisor growth rate before hibernation. We found that the mean width did not depend on the sex of animals, locality, and incisor length, but depended on animal age. The increment width significantly decreased, and the number of the increments formed before hibernation significantly increased with age. This means that the growth rate of the incisors and the intensity of their attrition decrease with the animals’ age. The decrease in the incisor growth rate with age is a manifestation of the well-known decrease with age in the intensity of all growth processes in mammals. As a result of this decrease, in the majority of old marmots under study, zones of hibernation were revealed in the basal as well as in the apical parts of the incisor. The zone in the basal part formed during the latest hibernation and the zone in the apical part corresponded to the previous one. Thus, the incisor preserved the record of the entire year of animal life.

Dramatic intraspecific differences in migratory routes, stopover sites and wintering areas, revealed using light-level geolocators

Migratory divides are contact zones between breeding populations that use divergent migratory routes and have been described in a variety of species. These divides are of major importance to evolution, ecology and conservation but have been identified using limited band recovery data and/or indirect methods. Data from band recoveries and mitochondrial haplotypes suggested that inland and coastal Swainson's thrushes (Catharus ustulatus) form a migratory divide in western North America. We attached light-level geolocators to birds at the edges of this contact zone to provide, to our knowledge, the first direct test of a putative divide using data from individual birds over the entire annual cycle. Coastal thrushes migrated along the west coast to Mexico, Guatemala and Honduras. Some of these birds used multiple wintering sites. Inland thrushes migrated across the Rocky Mountains, through central North America to Columbia and Venezuela. These birds migrated longer distances than coastal birds and performed a loop migration, navigating over the Gulf of Mexico in autumn and around this barrier in spring. These findings support the suggestion that divergent migratory behaviour could contribute to reproductive isolation between migrants, advance our understanding of their non-breeding ecology, and are integral to development of detailed conservation strategies for this group.

On the utility of land surface models for agricultural drought monitoring

Abstract. The lagged rank cross-correlation between model-derived root-zone soil moisture estimates and remotely sensed vegetation indices (VI) is examined between January 2000 and December 2010 to quantify the skill of various soil moisture models for agricultural drought monitoring. Examined modeling strategies range from a simple antecedent precipitation index to the application of modern land surface models (LSMs) based on complex water and energy balance formulations. A quasi-global evaluation of lagged VI/soil moisture cross-correlation suggests, when globally averaged across the entire annual cycle, soil moisture estimates obtained from complex LSMs provide little added skill (&lt; 5% in relative terms) in anticipating variations in vegetation condition relative to a simplified water accounting procedure based solely on observed precipitation. However, larger amounts of added skill (5–15% in relative terms) can be identified when focusing exclusively on the extra-tropical growing season and/or utilizing soil moisture values acquired by averaging across a multi-model ensemble.

Independence among physiological traits suggests flexibility in the face of ecological demands on phenotypes

Phenotypic flexibility allows animals to adjust their physiology to diverse environmental conditions encountered over the year. Examining how these varying traits covary gives insights into potential constraints or freedoms that may shape evolutionary trajectories. In this study, we examined relationships among haematocrit, baseline corticosterone concentration, constitutive immune function and basal metabolic rate in red knot Calidris canutus islandica individuals subjected to experimentally manipulated temperature treatments over an entire annual cycle. If covariation among traits is constrained, we predict consistent covariation within and among individuals. We further predict consistent correlations between physiological and metabolic traits if constraints underlie species-level patterns found along the slow-fast pace-of-life continuum. We found no consistent correlations among haematocrit, baseline corticosterone concentration, immune function and basal metabolic rate either within or among individuals. This provides no evidence for constraints limiting relationships among these measures of the cardiovascular, endocrine, immune and metabolic systems in individual red knots. Rather, our data suggest that knots are free to adjust individual parts of their physiology independently. This makes good sense if one places the animal within its ecological context where different aspects of the environment might put different pressures on different aspects of physiology.