关键词： Acari   Collembola   Forest ecosystem   Litter traits   Plant-soil interaction   Predator-prey interaction  

摘要： Plant litter decomposition is an essential process of ecosystem functioning, driven by a complex soil food web. The identity and density of the predators, as well as the quality and quantity of litter, could conjointly affect the strength of trophic interactions within a soil food web. Pine and oak are dominant tree species in temperate and Mediterranean forests and, although they exhibit distinct litter characteristics, no previous study attempted to decipher how these two litters can affect a litter-based multi-trophic system with varying predator density. Using a microcosm experiment, we aimed at understanding how different densities of a predatory Acari (Stratiolaelaps scimitus) and two Mediterranean litter species (Quercus pubescens and Pinus halepensis) may impact the demographic parameters of the predatory Acari, its Collembola prey (Folsomia candida) and the fungal biomass associated with litter. We did not observe any interactive effect of litter identity and predator density on both predator and prey demographic parameters. Survival and fecundity rates of the predator and its prey decreased at high predator density. However, demographic parameters of the predator and its prey were differentially affected by litter identity, with greater prey demographic parameters in Quercus litter and, in the opposite, greater predator demographic parameters in Pinus litter, probably due to differences in physical characteristics providing more or less refuge for the prey. We also observed a higher increase in fungal biomass in Pinus compared to Quercus litter, i.e. the litter with the fungivorous Collembola abundance reduced by the predatory Acari. Litter identity could thus strongly regulate these tri-trophic interactions (Fungi - fungivorous Collembola - predatory Acari) in forest ecosystems. Finally, the implications of our findings could be important as the distribution area of oak and pine forests may be altered in response to climate change with then potentially st

关键词： LenStar   Ultrasonography   Ocular axial dimensions   Refractive indices   Tree shrews  

摘要： We describe an analysis strategy to obtain ultrasonography-matched axial dimensions of small animal eyes using the LenStar biometer. The LenStar optical low-coherence reflectometer is an attractive device for animal research due to its high precision, non-invasiveness, and the ability to measure the axial dimensions of cornea, anterior chamber, lens, vitreous chamber, and axial length. However, this optical biometer was designed for clinical applications in human eyes and its internal analysis provides inaccurate values when used on small eyes due to species-dependent differences in refractive indices and relative axial dimensions. The LenStar uses a near infrared light source to measure optical path lengths (OPLs) that are converted by the LenStar's EyeSuite software into geometrical lengths (GLs) based on the refractive indices and axial dimensions of the human eye. We present a strategy that extracts the OPLs, determines refractive indices specific for the small animal eye of interest and then calculates corrected GLs. The refractive indices are obtained by matching the LenStar values to ultrasonography values in the same eyes. As compared to ultrasounography, we found that the internal calculations of the LenStar underestimate the axial dimensions of all ocular compartments of the tree shrew eye: anterior segment depth by 6.17 +/- 4.50%, lens thickness by 1.37 +/- 3.06%, vitreous chamber depth by 29.23 +/- 2.35%, and axial length by 10.62 +/- 1.75%. Using tree shrew-specific refractive indices, the axial dimensions closely matched those measured by ultrasonography for each compartment. Our analysis strategy can be easily translated to other species by obtaining a similar paired data set using ultrasonography and LenStar, and applying our step by step procedures.

关键词： culling   fire management   fire-grazing interaction   grazing   herbivore driven system   Kruger National Park   protected area   rewilding  

摘要： Fire and herbivory are competitive processes in grassy ecosystems as they both consume above-ground biomass. Despite this interaction between fire and grazing, herbivore and fire management plans in conservation areas are usually perceived, and hence managed, independently. This study aims to demonstrate the importance of acknowledging and integrating the interdependence between herbivore and fire management. We compare average proportional area burnt during years when large-scale culling kept herbivore biomass within a narrow range within the Kruger National Park, South Africa, against subsequent years of no culling when herbivore densities increased to effectively double the biomass. Furthermore, to improve our mechanistic understanding, we utilize natural gradients in rainfall (north to south) and grazing (distance from rivers) to test a conceptual model of how herbivory influences fire occurrence under different rainfall regimes. Fires were more prevalent during the culling period than thereafter, and the fire suppression effect of increasing grazing biomass was most pronounced in areas closer to rivers (50% reduction within 1 km of rivers). The "grazer effect" (i.e. difference between % area burnt between low and high grazer biomass years) seems to be more pronounced in arid landscapes than in semiarid landscapes, which in turn is more pronounced than in the mesic landscapes. Despite elephants being mixed feeders, elephant density influences fire occurrence more than the density of buffaloes or hippopotami. Synthesis and applications: Herbivore and fire management actions should be integrated, as events that influence herbivore densities go on to influence fire occurrence in subsequent years. In areas with 400-600 mm MAP it is particularly important because changes in herbivore numbers-due to drought, predation, disease, or human interventions-can result in switches between fire- and herbivore-dominated systems, with cascading consequences for biodiversity and

关键词： Alley cropping   Grass strip   Ground dwelling arthropods   Maize   Tree row   Winter cereals  

摘要： Ground dwelling arthropods present in agricultural systems regulate multiple ecosystem services (ES), such as nutrient and carbon cycling and biological pest control. The presence of semi-natural landscape features, such as the tree component of agroforestry systems (AFS), can contribute to functional agrobiodiversity and optimize the delivery of such ES in agricultural landscapes. In temperate AFS, however, potential patterns in abundance and diversity have scarcely been investigated for detritivorous soil dwelling arthropods and only to a limited extent for predatory arthropods. Therefore, we have assessed the abundance and diversity of woodlice (Isopoda), millipedes (Diplopoda), rove beetles (Coleoptera: Staphylinidae) and carabids (Coleoptera: Carabidae) as a function of the distance to the tree row in a set of temperate arable AFS. Abundance and diversity of woodlice and millipedes were significantly higher in the tree rows than in the arable zone. In the case of mature trees, a higher abundance of detritivores was also observed in the arable zone close to the trees. Tree presence did not consistently lead to higher abundance of predatory arthropods, but a limited increase in carabid diversity was observed in the arable zone close to the tree rows. These results indicate that in temperate AFS, the trees and the associated understory vegetation strip contribute to the preservation of arthropod biodiversity and the enhancement of associated ES in the tree rows and in the arable field zone.

关键词： 人诺如病毒   动物模型   树鼩  

摘要： 目的探索通过灌胃攻毒的方法建立树鼩诺如病毒(Human Noroviruses,Hu No Vs)感染动物模型的可行性。方法分别灌胃两组6月龄树鼩攻毒GII.4型Hu No Vs 2010和Sydney株粪便悬液,对照组灌同等体积的PBS(每组5只),攻毒后连续7 d观察体征和腹泻症状,每隔24 h采集粪便应用RT-PCR法检测Hu No Vs RNA,处死树鼩后采集小肠组织,HE染色观察病理变化并应用免疫组化法检测病毒抗原,并对树鼩唾液进行人类组织血型抗原(histoblood group antigen,HBGAs)鉴定分析。结果树鼩经Hu No Vs灌胃攻毒后未出现明显感染症状和腹泻,粪便标本中未检测到Hu No Vs RNA,小肠组织中未检测到Hu No Vs抗原,病理变化不明显,树鼩唾液中HBGAs抗原为阴性。结论树鼩对Hu No Vs不易感原因可能与其不分泌表达HBGAs和普通级饲养繁殖条件等有关,Hu No Vs感染树鼩小动物模型仍有待进一步探索。

关键词： aerial insectivore   antiparasite treatment   brood age   brood size hierarchy   harsh weather   plumage characteristics   Tachycineta bicolor   Tree Swallow  

摘要： Extreme weather events influence the population dynamics of wild animals. For organisms whose food source is affected by environmental conditions, such as aerial insectivorous birds, periods of inclement weather can have devastating effects. Here, we examine predictors of survival of individual nestlings and whole broods in Tree Swallows (Tachycineta bicolor (Vieillot, 1808)) during an extreme, 2-day harsh weather event in central British Columbia, Canada, which co-occurred with experimental reduction of nest ectoparasite loads using an antiparasite drug (ivermectin) or heat-treating nests. A curvilinear relationship existed between survival and brood age such that middle-aged broods were least likely to survive. Survival of broods and nestlings was higher when raised by males with bluer plumage, whereas nestling survival was lower when female parents had brighter and more UV-reflective plumage. Within broods, smaller nestlings had a lower chance of surviving than their larger siblings. Nestlings in broods where half of the offspring received ivermectin injections had significantly higher chances of surviving than nestlings from nonexperimental broods, suggesting that parasite loads can influence survival during inclement weather. Our results identify several factors influencing resiliency of nestlings to harsh weather and are particularly relevant in the context of declining aerial insectivorous bird populations and climate change.

关键词： Shading   Black globe temperature and humidity index   Radiant thermal load   Eucalyptus   Native trees  

摘要： This study aimed to assess solar radiation transmission and animal thermal comfort indexes in two silvopastoral systems established with different tree arrangements in a tropical region. This study was conducted between 2014 and 2017 in two silvopastoral systems, one composed by an established Urochloa (syn. Brachiaria) decumbens pasture with Brazilian native trees planted in triple rows spaced 17 m apart, and another by an established Urochloa (syn. Brachiaria) brizantha (Hochst ex A. Rich.) Stapf %RS Plata' pasture with Eucalyptus urograndis (clone GG100) trees arranged in single rows spaced 15 m apart. In these systems and in a full-sun pasture, photosynthetically active radiation transmission, air temperature, relative humidity, black globe temperature, and wind speed were measured. These variables were used to calculate black globe temperature and humidity index (BGHI) and radiant thermal load (RU). Higher animal thermal comfort was observed in the silvopastoral systems due to changes in the microclimate induced by the trees;notably, a decrease in solar radiation transmission. Fewer hours of potential animal thermal stress (BGHI > 79) were observed in the silvopastoral systems than under the full-sun conditions, with differences up to 3 h per day. The silvopastoral systems presented lower radiant thermal load than the full-sun pasture with differences up to 22% achieved. The assessed silvopastoral systems may help livestock adapt to climate change, since they achieved the limit of BGHI considered to cause stress to animals following an increase of 2.2 degrees C in air temperature, compared with full-sun pastures.

关键词： Acacia robusta   Acacia tortilis   competition   environmental gradients   herbaceous vegetation   plant-animal interactions   plant-available moisture   recruitment limitation  

摘要： 1. Savanna ecosystems span a diverse range of climates, edaphic conditions, and disturbance regimes, the complexity of which has stimulated long-standing interest in the mechanisms that maintain tree-grass coexistence. One hypothesis suggests that tree establishment is strongly limited by one or several demographic bottlenecks at early stages of the tree life cycle. A major impediment to testing this hypothesis is the lack of data on the relative strengths of different bottle-necks across key environmental gradients. 2. To identify demographic bottlenecks that limit early tree establishment (0-18 months), we conducted a series of transplant experiments with two savanna trees species (Acacia robusta and Acacia tortilis) across a natural rainfall and soil fertility gradient in the Serengeti ecosystem, Tanzania. We tested the interactive effects of precipitation, herbivory, seed scarification, grass competition, water limitation, and tree species identity on two key life stages: germination and early seedling survival (0-2 months), and juvenile seedling survival (2-18 months). 3. Germination and early seedling survival increased as a function of rainfall, in the absence of herbivores and when seeds were scarified. Juvenile seedling survival, in contrast, decreased with rainfall but increased in the absence of herbivores. Grass removal had the single strongest (positive) effect on juvenile seedling survival of any treatment. Soil moisture monitoring and grass-addition treatments revealed that grasses negatively affected seedlings in ways that were not necessarily linked to soil moisture. 4. A demographic model combining all effects across early life stages showed that the strength of grass competition on juvenile seedling survival was the key factor limiting early tree establishment. While rainfall had an unexpected opposing effect on the two life stages, the net effect of mean annual precipitation on early tree establishment was positive. 5. Synthesis. Successful tree

关键词： Polyphenolic compounds   Mangiferins   Chlorogenic acids   Flavonoids   Caffeine  

摘要： There are relatively few studies concerning the use of coffee leaves for medicinal purposes and the composition of secondary plant substances. Therefore, we identified and quantitated polyphenolic compounds along with caffeine present in methanol extracts of Coffea arabica leaves from three different regions of Brazil (Ceara, Minas Gerais and Sao Paulo) by HPLC-ESI-MS. In addition, correlations between polyphenolic content of the coffee leaves and antioxidant assays DPPH, FRAP and ORAC were evaluated. Fifteen compounds belonging to three classes of polyphenols (xanthones, chlorogenic acids and flavonoids) along with the alkaloid caffeine were detected. The mean concentration of total polyphenolic compounds in the leaves of C. arabica, harvested from three different regions of Brazil was quite variable. The highest values were detected in the coffee leaves harvested in Minas Gerais (n = 4) at 40.80(13.00) g/kg (SD), followed by coffee leaves harvested in Sao Paulo (n = 20) at 24.79(20.19) g/kg, and the lowest in coffee leaves harvested in Ceara (n = 11) in the Northeast of Brazil at 10.30(5.61) g/kg. The three classes of polyphenols, all showed excellent correlations in the antioxidant assays. Coffee leaf tea, appears to be an excellent functional beverage, with its high content of polyphenolic compounds, which may render positive biologic effects, when inbibed as part of the normal human diet.

关键词： aquatic-terrestrial linkages   stable isotopes   riparian   African clawless otter   Aonyx capensis  

摘要： Animal-mediated nutrient transfer facilitates nutrient cycling in marine, freshwater and terrestrial ecosystems via the deposition of aquatically-derived nutrients such as nitrogen (N) and carbon (C). This mode of nutrient transfer has not been studied in southern African river systems. We investigated nutrient deposition associated with defecation, urination, and scent-marking at latrine sites of a semi-aquatic predator species (African clawless otters Aonyx capensis) in a riparian zone of a Bankenveld savanna ecosystem. We provide a comparison of stable nitrogen isotopes (delta N-15) measured in soil, vegetation and faecal material, between latrine and paired control sites. Latrine sites displayed higher delta N-15 values than the paired non-latrine sites, but only at the area of direct deposition (soil surfaces). This effect dissipated as the distance from direct contact increased, while no significant difference in delta 15N values was detected for sub-surface soil samples. Plants displayed varying trends of enriched delta 15N values between the latrine and paired control sites. These results suggest that several factors and processes such as leaching, mineralization, ammonia volatilization, and nitrogen acquisition influence the nutrient availability within latrine-soil-vegetation systems in riparian zones of African savanna ecosystems.