Adapting conservation efforts to face climate change: Modifying nest-site provisioning for lesser kestrels

Adaptation to climate change has recently become a crucial element on the climate change policy agenda as it is now recognized that even the most stringent mitigation efforts may not arrest the effects of climate warming. The ecological impacts and costs of predicted weather-related extreme events, such as extreme temperatures, are not fully understood and may present unexpected challenges to conservationists that require solutions. In Portugal, provisioning of artificial nests has been the main driver of the spectacular increase in the endangered lesser kestrel population. Nevertheless, atypically high temperatures recorded during the 2009 breeding season coincided with a mortality of 22% of surveyed chicks in provided nests. Hot days did not affected prey delivery rates to the nestlings, suggesting that the die-off was due to chicks’ acute dehydration. Chick mortality was significantly higher amongst younger individuals. Within survivors, physiological costs of high temperatures significantly affected chick growth and body condition at fledging. Nest-site microclimate was influenced by nest-type and compass orientation: wooden nest-boxes attained the highest temperatures, exceeding 55 °C when facing south, so explaining the recorded higher mortality, lower growth rates and lower fledging body condition among broods in these nests. Simulated scenarios of global warming with increasing occupation rate of artificial nests due to reductions in alternatives predicted a reduction in population growth rate. In the worst scenario, with a 100% occupancy of nest-boxes, the population growth would decline on average 7% per year. The impact of high temperatures on lesser kestrel breeding success highlights a need for actions to modify and research to adapt conservation efforts and future planning to account for climate change.     

Habitat management of little terns in Japan’s highly developed landscape

The little tern (Sterna albifrons) is a species of shorebird that nests in colonies on sandy beaches and riverbanks with little vegetation cover. In Japan, the natural breeding habitats of the terns have decreased drastically, and the species is listed under the category “vulnerable” in the Red List of the Government of Japan. To reduce the effects of habitat loss on the terns, conservationists are attempting to create and manage artificial colony sites in highly developed landscapes, such as reclaimed lands located in Tokyo Bay, central Japan. We present the factors that contribute to breeding success for this species and the habitat characteristics related to nest-site selection in the artificial colony sites along Tokyo Bay. Our data show that around 3 ha of a building rooftop without vegetation cover could sustain more than 2000 little tern nests. We found a strong positive relationship between colony size and hatching success, observing that a colony size of more than 100 lowered predation rates of eggs. On sites built upon white crushed-concrete, nest densities were high and predation rates of eggs were low. We also found that feeding rates were affected by foraging habitats, of which the best types were the shoreline of sandy beaches and mud flats. The 40 km dispersal range of the breeding terns, inferred from distribution data, should be considered when establishing a network of the multiple colony sites.     

What do artificial nests tells us about nest predation?

Artificial nests are commonly used to evaluate predation, but the assumption that this method mimics predation on natural nests has seldom been tested. Natural and artificial nests of eastern yellow robins (Eopsaltria australis) were monitored in four, 55-ha plots over two breeding seasons. Overall, daily survival rates were higher (P<0.001) for natural (95%/day) than for artificial nests (88%/day). Among plots, daily survival rates for the two types of nests were not correlated with one another (P=0.72) indicating that the spatial pattern of predation on artificial nests did not mimic that for natural nests. Seasonal variation was evident for natural nests in one year, when they were more successful at the beginning and end of the breeding season. No seasonal patterns were observed for artificial nests in either year. Neither natural nor artificial nests showed annual variation in predation. Previous researchers concluded that large birds were important predators on robin nests. In this study, predation by large birds on artificial nests was positively correlated with the numbers of large birds counted on the plots (P=0.04). However, large birds depredated only 16% of artificial nests. Daily survival rates for artificial nests were recalculated using predation by large birds only. These rates were compared with natural nests, but there was still no correspondence in the spatial and temporal patterns of predation for the two types of nests. These results suggest that inferences about predation on natural nests based on artificial nest studies should be avoided.     

The distribution of volatile isoprenoids in the soil horizons around Pinus halepensis trees

We measured the terpene concentration in pentane and water extracts from soil horizons (litter, organic, top and low mineral) and from roots growing in top and low mineral horizons on a distance gradient from Pinus halepensis L. trees growing alone on a grassland. Terpene concentrations in pentane were higher than in water extracts, although β-caryophyllene showed relatively high solubility in water. The litter and roots were important sources of terpenes in soil. Alpha-pinene dominated in roots growing in both “top” (A1) and “low” (B) mineral horizons (123 ± 36 μg g⁻¹ or 14 ± 5 mg m⁻²) and roots in low mineral horizon (270 ± 91 μg g⁻¹ or 7 ± 2 mg m⁻²). Beta-caryophyllene dominated in litter (1469 ± 331 μg g⁻¹ or 2004 ± 481 mg m⁻²). Terpene concentration in soil decreased with increasing distance to the trunk. This is likely to be related to changes in litter and roots type on the distance gradient from pine to grass and herbs. The relative contributions of all compounds, except α-pinene, were similar in the mineral soils and litter. This suggests that litter of P. halepensis is probably the main source of major terpene compounds. However, long-term emissions of α-pinene from P. halepensis roots might also contribute to α-pinene concentrations in rhizosphere soils.     

Growth rates of Aporrectodea caliginosa (Oligochaetae: Lumbricidae) as influenced by soil temperature and moisture in disturbed and undisturbed soil columns

Earthworm growth is affected by fluctuations in soil temperature and moisture and hence, may be used as an indicator of earthworm activity under field conditions. There is no standard methodology for measuring earthworm growth and results obtained in the laboratory with a variety of food sources, soil quantities and container shapes cannot easily be compared or used to estimate earthworm growth in the field. The objective of this experiment was to determine growth rates of the endogeic earthworm Aporrectodea caliginosa (Savigny) over a range of temperatures (5–20 °C) and soil water potentials (−5 to−54 kPa) in disturbed and undisturbed soil columns in the laboratory. We used PVC cores (6 cm diameter, 15 cm height) containing undisturbed and disturbed soil, and 1 l cylindrical pots (11 cm diameter, 14 cm height) with disturbed soil. All containers contained about 500 g of moist soil. The growth rates of juvenile A. caliginosa were determined after 14–28 days. The instantaneous growth rate (IGR) was affected significantly by soil moisture, temperature, and the temperature×moisture interaction, ranging from −0.092 to 0.037 d⁻¹. Optimum growth conditions for A. caliginosa were at 20 °C and −5 kPa water potential, and they lost weight when the soil water potential was −54 kPa for all temperatures and also when the temperature was 5 °C for all water potentials. Growth rates were significantly greater in pots than in cores, but the growth rates of earthworms in cores with undisturbed or disturbed soil did not differ significantly. The feeding and burrowing habits of earthworms should be considered when choosing the container for growth experiments in order to improve our ability to extrapolate earthworm growth rates from the laboratory to the field.     

Ant-induced soil modification and its effect on plant below-ground biomass

Lasius flavus is a dominant mound-building ant species of temperate grasslands that significantly modifies soil parameters. These modifications are usually the result of workers’ activities such as food accumulation and nest construction. An alternative hypothesis that could explain changes in soil is colony founding in areas of higher soil fertility.In our study we investigated several soil parameters sampled in 10 ant nests and adjacent (control) plots in mountain grassland in Slovakia. The alternative hypothesis was tested by comparing occupied and abandoned mounds. While we found increased concentrations of available P and K in the nests, concentrations of total C, total N, Ca²⁺ and Mg²⁺ were lower there. We propose that differences found between the soil of nests and control plots are entirely a product of ant activity during mound occupancy and not due to initial soil differences during nest establishment. This was confirmed by the comparison of occupied and abandoned nests in which the soil fertility of abandoned nests was similar to conditions in the surrounding soil.Along with the modification of soil chemistry, we recorded changes in soil physical properties and the vertical distribution of nutrients. Ant nests were characterized by the dominance of 0.02–0.1 mm particles and lower bulk density. In the same habitat, nutrient concentrations did not change along the vertical gradient in contrast to control plots where soil nutrients decreased and bulk density increased with depth. Root biomass followed the vertical pattern observed with nutrients: in control plots, most roots were concentrated in the uppermost layer (0–3 cm), whereas they were evenly distributed along the vertical gradient in the nests. We also found that rhizome internodes of Agrostis capillaris were thinner and longer in plants from the mounds. Changes in soil physical properties, vertical distribution of nutrients and root biomass in the nests are most probably a consequence of mounding and soil mixing (bioturbation), which has been less reported on in ant-soil studies.     

Contribution of fine roots to ecosystem biomass and net primary production in black spruce, aspen, and jack pine forests in Saskatchewan

Fine root (<2 mm) processes contribute to and exhibit control over a large pool of labile carbon (C) in boreal forest ecosystems because of the high proportion of C allocated to fine root net primary production (NPP), and the rapid decomposition of fine roots relative to aboveground counterparts. The objective of this study was to determine the contribution of fine roots to ecosystem biomass and NPP in a mature black spruce (Picea mariana Mill.) (OBS), aspen (Populus tremuloides Michx.) (OA), and jack pine (Pinus banksiana Lamb.) (OJP) stand, and an 11-year-old harvested jack pine (HJP) stand in Saskatchewan. Estimates of fine root biomass and NPP were obtained from nine minirhizotron (MR) tubes at each of the four Boreal Ecosystem Research and Monitoring Sites (BERMS). Fine root data were collected once a month for May–September in 2003 and 2004. Additional C biomass and NPP data for various components of the forest stands were obtained from Gower et al. (1997) and Howard et al. (2004). Annual fine root biomass averaged 3.10 ± 0.89, 1.71 ± 0.49, 1.62 ± 0.32, and 2.96 ± 0.67 Mg C ha⁻¹ (means ± S.D.) at OBS, OA, OJP, and HJP, respectively, comprising between 1 and 6% of total stand biomass. Annual fine root NPP averaged 2.66 ± 0.97, 2.03 ± 0.43, 1.44 ± 0.43, and 2.16 ± 0.81 Mg C ha⁻¹ year⁻¹ (means ± S.D.) at OBS, OA, OJP, and HJP, respectively, constituting between 41 and 71% of total stand NPP. Results of this study indicate that fine roots produce a large amount of C in boreal forests. It is speculated that fine root NPP may control a large amount of labile C-cycling in boreal forests and that fine root responses to environmental and anthropogenic stress may be an early indicator of impaired ecosystem functioning.     

Vermicomposting of sewage sludge: Effect of bulking materials on the growth and reproduction of the earthworm Eisenia andrei

The effect of different residual bulking agents (paper, cardboard, grass clippings, pine needles, sawdust and food wastes) in mixtures with sewage sludge (1:1 dry weight) on the growth and reproduction of Eisenia andrei, Bouché 1972 was studied in smallscale laboratory experiments with batches of sixty earthworms. The maximum weight achieved and the highest growth rate were attained in the mixture with food waste (755±18 mg and 18.6±0.6 mg day⁻¹ respectively) whereas the smallest size and the lowest growth rate was achieved in the mixture of sewage sludge with sawdust (572±18 mg and 11±0.7 mg day⁻¹ respectively). The earthworms showed much higher reproductive rates in the paper and cardboard mixtures (2.82±0.39 and 3.19±0.30 cocoons earthworm⁻¹ week⁻¹ respectively) compared to the control with sewage sludge alone (0.05±0.01 cocoons earthworm⁻¹ week⁻¹).     

Use of time-activity budgets to measure early progress of a social attraction restoration project

Social attraction is a useful technique for re-establishing or relocating waterbird colonies and other species groups. However, little information exists regarding how newly attending individuals behave when the social environment is influenced predominantly by artificial stimuli. To help assess early progress of colony re-establishment, we compared time-activity budgets of common murres (Uria aalge) at a social attraction site (Devil’s Slide Rock; DSR) in central California with two nearby reference colonies during the first 3 years (1996–1998) of efforts. Murres at all colonies spent over 95% of their time engaged in resting, comfort, courtship, and alert activities during the pre-breeding period and over 88% of their time in similar activities during the breeding period. Although patterns were similar overall, comparisons of pooled and year-specific time budget data revealed significant differences between all three colonies, especially during pre-breeding. Murres at DSR typically engaged in comfort behaviors less frequently and in alert and courtship behaviors more frequently than reference colonies. Differences likely were due to recent re-establishment, including lower bird densities and higher proportions of non-breeders and first-time breeders at DSR, along with other factors such as disturbance. Results indicate that newly attracted birds at DSR behaved “normally” even though the social environment was influenced predominantly by artificial stimuli. Furthermore, re-established breeding in the first year of efforts, subsequent colony growth, and high productivity reflected successful restoration efforts. Thus, time-activity budgets can provide important measures of early progress of social attraction efforts and as such can be used to inform adaptive management decisions.     

Stemflow in three shrubs and its effect on soil water enhancement in semiarid loess region of China

Stemflow of three semiarid shrubs (Tamarix ramosissima, Caragana korshinskii and Reaumuria soongorica) and its effect on soil water enhancement were evaluated during the growing season of 2004 and 2005 in the semiarid loess region of China. The results indicated that stemflow averaged 2.2%, 3.7% and 7.2% of the bulk precipitation for T. ramosissima, R. soongorica and C. korshinskii, respectively. Individual stemflow increased in a linear function with increasing rainfall depth, while it tended to increase with rain intensity when rain intensity was less than 2 mm h⁻¹, but showed an opposite trend when rain intensity was greater than 2 mm h⁻¹.The relationship between funnelling ratios and rainfall suggested that there existed a rainfall depth threshold of 11 mm for C. korshinskii and 17 mm for both T. ramosissima and R. soongorica. Funnelling ratios positively increased with increasing rainfall depth before the rainfall depth threshold values had been reached but showed a decreasing trend after the rainfall depth threshold. Average funnelling ratios were 153.5 ± 66.2, 53.2 ± 25.7 and 24.8 ± 15.3 for C. korshinskii, R. soongorica and T. ramosissima, respectively, indicating canopy architecture of the three shrubs was an effective funnel to channel stemflow to the root area, and C. korshinskii showed greater potential to use stemflow water in the arid conditions. For individual rainfall events the wetting front depths in the rooting zone around the stems of the shrubs were 1.2–4.5, 1.4–3.8 and 1.4–2.8 times deeper than that in the bare area outside canopy for C. korshinskii, T. ramosissima and R. soongorica, respectively; correspondingly, soil water content was also significantly higher in the root area around the shrub stem than that in the area outside the shrub canopy. This confirms that shrub stemflow conserved in the deep soil layers may be an available moisture source for plant growth under arid conditions.     

Responses of small rodents to habitat restoration and management for the imperiled Florida Scrub-Jay

Debate about the relative merits of single-species management versus more comprehensive approaches has intensified in recent years. In east-central Florida, USA, land managers use prescribed burns and mechanical cutting to manage and restore scrub habitat to benefit the imperiled Florida Scrub-Jay (Aphelocoma coerulescens). However, these land-management techniques may affect non-target taxa, especially the threatened southeastern beach mouse (Peromyscus polionotus niveiventris). We evaluated the collateral effects of single-species land management by trapping P. p. niveiventris and other small rodents in eighteen land-management compartments at Cape Canaveral Air Force Station, Florida during 2004–2005. Compartments were managed using either prescribed burns (N = 5), mechanical cutting (N = 6), checkerboarding (cut and uncut lanes alternating and overlapping, followed by a prescribed burn, N = 4) or left unburned and uncut for >50 year (N = 3). P. p. niveiventris was significantly more abundant in compartments managed with prescribed burns (mean ± SE: 4.2 ± 0.7 individuals/transect) than those managed with cutting alone (1.0 ± 0.3) or not managed for >50 y (0.2 ± 0.1 individuals/transect). In contrast, the cotton mouse (Peromyscus gossypinus) tended to be more abundant in compartments managed with mechanical cutting alone (2.6 ± 0.4 individuals/transect) compared to the other three management strategies (prescribed burns; 1.5 ± 0.4; checkerboarding, 1.1 ± 0.3; not managed, 1.6 ± 0.4 individuals/transect) but these differences were not statistically significant. Abundances of P. p. niveiventris and Florida Scrub-Jay breeding groups were positively correlated (r = 0.655), suggesting that both listed species benefit from similar management techniques. Thus, the mosaic of burned and cut patches used to improve habitat for the Florida Scrub-Jay also benefits an endemic, non-target species. Single-species management may benefit multiple species when restoration improves their shared habitat, which in this case is an endangered, fire-dependent ecosystem: Florida scrub.     

Sorptive interaction between goethite and strongly reducing organic substances from anaerobic decomposition of green manures

Strongly reducing organic substances (SROS) and iron oxides exist widely in soils and sediments and have been implicated in many soil and sediment processes. In the present work, the sorptive interaction between goethite and SROS derived from anaerobic decomposition of green manures was investigated by differential pulse voltammetry (DPV). Both green manures, Astragalus sinicus (Astragalus) and Vicia varia (Vicia) were chosen to be anaerobically decomposed by the mixed microorganisms isolated from paddy soils for 30 d to prepare different SROS. Goethite used in experiments was synthesized in laboratory. The anaerobic incubation solutions from green manures at different incubation time were arranged to react with goethite, in which SROS concentration and Fe(II) species were analyzed. The anaerobic decomposition of Astragalus generally produced SROS more in amount but weaker in reducibility than that of Vicia in the same incubation time. The available SROS from Astragalus that could interact with goethite was 0.69 ± 0.04, 0.84 ± 0.04 and 1.09 ± 0.03 cmol kg⁻¹ as incubated for 10, 15 and 30 d, respectively, for Vicia, it was 0.12 ± 0.03, 0.46 ± 0.02 and 0.70 ± 0.02 cmol kg⁻¹. One of the fates of SROS as they interacted with goethite was oxidation. The amounts of oxidizable SROS from Astragalus decreased over increasing incubation time from 0.51 ± 0.05 cmol kg⁻¹ at day 10 to 0.39 ± 0.04 cmol kg⁻¹ at day 30, but for Vicia, it increased with the highest reaching to 0.58 ± 0.04 cmol kg⁻¹ at day 30. Another fate of these substances was sorption by goethite. The SROS from Astragalus were sorbed more readily than those from Vicia, and closely depended upon the incubation time, whereas for those from Vicia, the corresponding values were remarkably less and apparently unchangeable with incubation time. The extent of goethite dissolution induced by the anaerobic solution from Vicia was greater than that from Astragalus, showing its higher reactivity.     

Evaluation of NASA satellite- and assimilation model-derived long-term daily temperature data over the continental US

Agricultural research increasingly is expected to provide precise, quantitative information with an explicit geographic coverage. Limited availability of daily meteorological records often constrains efforts to provide such information through use of simulation models, spatial analysis, and related decision support tools. The Prediction Of Worldwide Energy Resources (NASA/POWER) project at the NASA Langley Research Center provides daily data globally for maximum and minimum temperatures and other weather variables on a 1° latitude–longitude grid. The data are assembled from a range of products derived from satellite imagery, ground observations, windsondes, modeling and data assimilation. Daily temperature data from NASA/POWER for 1983 to 2004 for the continental US were compared with data of 855 individual ground stations from the National Weather Service Cooperative Observer Program (COOP). Additionally, a wheat (Triticum aestivum L.) simulation model was used to compare predicted time to anthesis using the two data sources. Comparisons of daily maximum temperatures (T_max) gave an r²-value of 0.88 (P < 0.001) and root-mean-squared error (RMSE) of 4.1 °C. For minimum temperature (T_min), the r²-value was 0.88 (P < 0.001) and RMSE, 3.7 °C. Mean values of T_max, and T_min from NASA/POWER were, respectively, 2.4 °C cooler and 1.1 °C warmer than the COOP data. Differences in temperature were least during summer months. When data were aggregated over periods of 8 days or more, the RMSE values declined to below 2.7 °C for T_max and T_min. Simulations of time to anthesis with the two data sources were also strongly correlated (r² = 0.92, P < 0.001, RMSE = 14.5 d). Anthesis dates of winter wheat regions showed better agreement than southern, winter-grown spring wheat regions. The differences between the data sources were associated with differences in elevation, which in large part resulted from NASA/POWER data being based on mean elevations over a 1° grid cells vs. COOP data corresponding to the elevation of specific stations. Additional sources of variation might include proximity to coastlines and differences in observation time, although these factors were not quantified. Overall, if mountainous and coastal regions are excluded, the NASA/POWER data appeared promising as a source of continuous daily temperature data for the USA for research and management applications concerned with scales appropriate to the 1° coordinate grid. It further appeared that the POWER data could be improved by adjusting for elevation (lapse rate) effects, reducing seasonal bias, and refining estimation of actual maximum and minimum temperatures in diurnal cycles.     

Vulnerability of ground-nesting waterbirds to predation by invasive American mink in the Cape Horn Biosphere Reserve, Chile

Biological invasions constitute one of the most important threats to biodiversity. This is especially true for “naïve” birds that have evolved in the absence of terrestrial predators in island ecosystems. The American mink (Mustela vison) has recently established a feral population on Navarino Island (55°S), southern Chile, where it represents a new guild of terrestrial mammal predators. We investigated the impact of mink on ground-nesting coastal waterbirds with the aim of deriving a vulnerability profile for birds as a function of different breeding strategies, habitat, and nest characteristics. We compared rates of nest survival and mink predation on 102 nests of solitary nesting species (Chloephaga picta, Tachyeres pteneres), on 361 nests of colonial birds (Larus dominicanus, Larus scoresbii, Sterna hirundinacea), and on 558 artificial nests. We calculated relative mink and bird densities at all nest sites. Nests of colonial species showed the highest nest survival probabilities (67-84%) and no predation by mink. Nest survival rates for solitary nesting species were lower (5-20%) and mink predation rates higher (10-44%). Discriminant analyses revealed that mink preyed upon artificial nests mainly at shores with rocky outcroppings where mink were abundant. High nest concealment increased the probability for predation by mink. Conservation planning should consider that invasive mink might severely affect the reproduction success of bird species with the following characteristics: solitary nesting, nesting habitat at rocky outcrop shores, and concealed nests. We recommend that work starts immediately to control the mink population with a priority in the nesting habitats of vulnerable endemic waterbirds.     

The impact of perennial cormorant colonies on soil phosphorus status

During the last decades, the population of cormorants in Northern Europe has grown rapidly due to protection. Their impact on vegetation has been recognized, as many trees containing cormorant colonies have collapsed, but their influence on the soil phosphorus (P) status and related ecological impacts have not been studied in details.In this study, total and plant available P (P_Total, P_Olsen) together with phosphate adsorption capacity and saturation (PAC, P_Sat) were measured in the soil at a reference area (control) and below two cormorant sub-colonies that differed in age and bird dropping density (indicated by number of used nests). One colony with totally 831 nests was 24 years old (Cormorant₂₄), while the age of the other colony with totally 181 nests was 12 years (Cormorant₁₂). Analyses of soil samples collected in four layers down to 80 cm showed strong decreases in P_Total and P_Olsen in the order: Cormorant₂₄ >> Cormorant₁₂ >> control and severe leaching of P into the subsoil below 80 cm at Cormorant₂₄ but not at Cormorant₁₂. Accordingly, in all four Cormorant₂₄ soil layers and in the upper three Cormorant₁₂ layers, P_Sat exceeded 0.25, which is considered the limit between retaining and leaking soils; P_Sat = P_Ox/PAC and PAC = 0.5 × (Al_Ox + Fe_Ox), i.e. half the sum of oxalate-extractable aluminium and iron. The importance of P_Olsen and P_Sat as indicators for P leaching was demonstrated as well as the strong impact that cormorants can have on the soil P status. This, in turn, will not only affect the ecosystem balance below the colonies but probably also threaten the water quality in nearby open waters as cormorant colonies are normally located on small lake islands or close to shallow bays.     

Differences in the reproductive success and survival of the rufous treecreeper (Climacteris rufa) between a fragmented and unfragmented landscape

The rufous treecreeper (Climacteris rufa) has declined in abundance in the agricultural regions of southwestern Australia. The patterns of decline are well documented, but the processes that threaten population persistence are poorly understood. I compared the reproductive success and survival of the treecreeper between three sites in an unfragmented landscape and four remnant categories (large, small, grazed and ungrazed) in a fragmented, agricultural landscape. Nest success and annual productivity were significantly higher in the unfragmented landscape, but varied between sites and remnant categories within landscapes. Nest success was lowest in grazed remnants and annual productivity was positively associated with territory size in the fragmented landscape. Fledgling survival rates did not differ between landscapes, but there was a trend for juvenile survival rates to be higher in the unfragmented landscape. I used artificial nests to compare relative predation rates between landscapes, and provisioning rates and prey biomass brought to nestlings to assess differences in food availability. There were no landscape differences in predation rates, but provisioning rates to nestlings and total prey biomass were significantly lower in the fragmented landscape. Mean habitat quality was also lower in the fragmented landscape, although it differed between remnant categories. Reduced reproductive success, juvenile survival, food availability and habitat quality may threaten the viability of the rufous treecreeper population living in the fragmented landscape. Limiting the modification of remaining habitat (e.g. removing stock grazing) and improving habitat quality are required to assist in the conservation of this species.     

Assessing the protective effect of vertically heterogeneous canopies against radiative frost: The case of quinoa on the Andean Altiplano

Night radiative frost is a highly limiting factor for agriculture in Andean highlands. Nevertheless, a diversity of crop species have been domesticated there, commonly showing high heterogeneity in plant growth at the field level. The possible protective effect of crop canopy heterogeneity against nocturnal radiative frost is examined using a dual approach, combining a field experiment and a simplified energy balance model at the leaf level. Leaf and air temperatures were registered over an entire quinoa crop cycle in the Andean highlands of Bolivia, comparing two cultivars: Blanca de Yanamuyu, a traditional landrace with high plant height heterogeneity, and Surumi, a more homogeneous selected variety. In both cultivars, inverted air density profiles during calm and clear nights result in air temperature changes up to 3 °C over 0.5 m height, with minimum air temperature concentrated at the upper part of the canopy. In these conditions, leaf temperature gradients of up to 2.6 °C m⁻¹ develop within the canopy of the traditional landrace, with minimum leaf temperature significantly higher (P < 0.001) in shaded plants of the landrace than in the selected cultivar. A dynamic model of leaf temperature based on canopy parameters and climatic records at screen level adequately simulates leaf temperature differences in the case of a vertically heterogeneous quinoa canopy. A sensitivity analysis of the model reveals that canopy height, leaf area index, and sky cloudiness have the most important influences on the development of the sheltering effect, while air temperature and air humidity play a minor role under typical radiative frost conditions. As for wind speed, its actual influence remains unclear due to experimental and modelling limitations at low wind speeds. The significance of these results is discussed in terms of the trade-off between stress adaptation and biomass productivity.     

Phosphorus release during decomposition of crop residues under conventional and zero tillage

Field experiments were conducted at Fort Vermilion (58°23′N 116°02′W), Alberta, to determine phosphorus (P) release patterns from red clover (Trifolium pratense) green manure (GM), field pea (Pisum sativum), canola (Brassica rapa) and monoculture wheat (Triticum aestivum) residues in the 7th and 8th years of conventional and zero tillage. Phosphorus contained in crop residues ranged from 1.5 kg ha⁻¹ in pea to 9.2 kg ha⁻¹ in clover GM, both under zero tillage. The patterns of P release over a 52-week period sometimes varied with tillage, i.e., a greater percentage of GM residue P was released under conventional tillage than under zero tillage in the first 2–10 weeks of residue placement. Wheat residues resulted in net P immobilization under zero tillage, but the amounts immobilized were less than 1 kg ha⁻¹. When net P mineralization occurred, the percentage of P released ranged from 24% of wheat P under conventional tillage to 74% of GM P under conventional tillage. The amounts of P released were 0.4 kg ha⁻¹ from wheat, 0.8 kg ha⁻¹ from canola, 0.4 kg ha⁻¹ from pea and 5.1–5.6 kg ha⁻¹ from clover GM residues. Therefore, only GM residues recycled agronomically significant amounts of P for use by subsequent crops in rotation. Phosphorus release was positively correlated with residue P concentration and negatively correlated with C/P and lignin/P ratios.     

Phenological trends in winter wheat and spring cotton in response to climate changes in northwest China

Understanding of the effects of climatic change on phenological phases of a crop species may help optimize management schemes to increase productivity. This study determined the trend of climatic changes during the period of 1981–2004 in northwest China and assessed the impacts of climatic changes on phenological phases and productivity of winter wheat (Triticum aestivum L.) and spring cotton (Gossypium hirsutum L.) at two locations. There was a clear trend of climate warming during the study period, leading to the earliness of pseudo stem elongation, booting, anthesis, and ripening stages of winter wheat by 13.2, 9.8, 11.0, and 10.8 d during the 24-year period, respectively. The growth period from seedling emergence to stem elongation shortened 16.1 d, but the growth period from anthesis to milk prolonged 8.2 d during the 24-year period. In cotton, the dates of seedling emergence, budding, anthesis, and boll-opening stages became earlier by, respectively, 10.9, 9.0, 13.9, and 16.4 d during the period of 1983–2004. However, the growth periods from five-leaf stage to budding, budding to anthesis, and anthesis to boll-opening stages were prolonged by 2.4, 12.0, and 9.0 d, respectively, for every 1 °C of rise in minimum temperature during their respective growth period. Increasing minimum temperatures during the vegetative period positively affected winter wheat growth but increases in maximum temperatures during the reproductive period negatively affected kernel weight and grain yield. Consequently, the grain yield of winter wheat had decreased, but the yield of cotton had increased during the study period. The trend of climate warming appeared to be favourable for cotton production but unfavourable for winter wheat in northwest China.     

Corvid response to human settlements and campgrounds: Causes, consequences, and challenges for conservation

Human development often favors species adapted to human conditions with subsequent negative effects on sensitive species. This is occurring throughout the urbanizing world as increases by generalist omnivores, like some crows and ravens (corvids) threaten other birds with increased rates of nest predation. The process of corvid responses and their actual effects on other species is only vaguely understood, so we quantified the population response of radio-tagged American crows (Corvus brachyrhynchos), common ravens (Corvus corax), and Steller’s jays (Cyanocitta stelleri) to human settlements and campgrounds and examined their influence as nest predators on simulated marbled murrelet (Brachyramphus marmoratus) nests on Washington’s Olympic Peninsula from 1995 to 2000. The behavior and demography of crows, ravens, and jays was correlated to varying degrees with proximity to human development. Crows and ravens had smaller home ranges and higher reproduction near human settlements and recreation. Annual survival of crows was positively associated with proximity to human development. Home range and reproduction of Steller’s jays was independent of proximity to human settlements and campgrounds. Local density of crows increased because home ranges of neighboring breeding pairs overlapped extensively (6× more than ravens and 3× more than Steller’s jays) and breeders far from anthropogenic foods traveled 10s of kilometers to access them. Corvids accounted for 32.5% of the predation events (n = 837) we documented on artificial murrelet nests. Small corvids (jays) were common nest predators across our study area but their contribution as predators did not vary with proximity to settlements and campgrounds. In contrast, large corvids (crows and ravens) were rare nest predators across our study area but their contribution varied greatly with proximity to settlements and campgrounds. Managers seeking to reduce the risk of nest predation need to consider the varied impacts and variable behavioral and population responses of potential nest predators. In our situation, removing large corvids may do little to reduce overall rates of nest predation because of the diverse predator assemblage, but reducing anthropogenic food in the landscape may be effective.