Effects of aggregated classifications of forest composition on estimates of evapotranspiration in a northern Wisconsin forest

Forest management presents challenges to accurate prediction of water and carbon exchange between the land surface and atmosphere, due to its alteration of forest structure and composition. We examined how forest species types in northern Wisconsin affect landscape scale water fluxes predicted from models driven by remotely sensed forest classification. A site‐specific classification was developed for the study site. Using this information and a digital soils database produced for the site we identified four key forest stand types: red pine, northern hardwoods, aspen, and forested wetland. Within these stand types, 64 trees representing 7 species were continuously monitored with sap flux sensors. Scaled stand‐level transpiration from sap flux was combined with a two‐source soil evaporation model and then applied over a 2.5 km × 3.0 km area around the WLEF AmeriFlux tower (Park Falls, Wisconsin) to estimate evapotranspiration. Water flux data at the tower was used as a check against these estimates. Then, experiments were conducted to determine the effects of aggregating vegetation types to International Geosphere– Biosphere Program (IGBP) level on water flux predictions. Taxonomic aggregation resulting in loss of species level information significantly altered landscape water flux predictions. However, daily water fluxes were not significantly affected by spatial aggregation when forested wetland evaporation was included. The results demonstrate the importance of aspen, which has a higher transpiration rate per unit leaf area than other forest species. However, more significant uncertainty results from not including forested wetland with its high rates of evaporation during wet summers.     

濒危物种巴东木莲的等位酶遗传多样性及其保护策略

为了确定中国特有濒危植物巴东木莲(Manglietia patungensis)的就地保护优先单元和制定迁地保护的取样策略,采用超薄平板聚丙烯酰胺等电聚焦电泳技术对巴东木莲的7个野生居群的等位酶遗传多样性及遗传结构进行了分析。通过对8个酶系统19个酶位点的分析结果来看,巴东木莲具有较高的遗传多样性和一定程度的遗传分化。每位点平均等位基因数（A）为1.57,多态位点百分率（P）为48.1%,平均预期杂合度（H_e）为0.192。巴东木莲居群间的遗传分化系数（G_ST）为0.165,说明其16.5％的遗传变异存在于居群间;基于遗传分化系数计算的基因流（N_m）为1.27,说明居群间存在适度的基因流;固定指数(F)为-0.191,显示巴东木莲居群杂合体轻微过量,纯合体略显不足。本研究表明,目前巴东木莲仍具有较高的遗传多样性并且在其适宜生境中可以完成自然更新,因此应采取以就地保护为主的综合保育策略。     

Gene flow in the green mirid,Creontiades dilutus (Hemiptera: Miridae), across arid and agricultural environments with different host plant species

Creontiades dilutus (Stål), the green mirid, is a polyphagous herbivorous insect endemic to Australia. Although common in the arid interior of Australia and found on several native host plants that are spatially and temporally ephemeral, green mirids also reach pest levels on several crops in eastern Australia. These host‐associated dynamics, distributed across a large geographic area, raise questions as to whether (1) seasonal fluctuations in population size result in genetic bottlenecks and drift, (2) arid and agricultural populations are genetically isolated, and (3) the use of different host plants results in genetic differentiation. We sequenced a mitochondrial COI fragment from individuals collected over 24 years and screened microsatellite variation from 32 populations across two seasons. The predominance of a single COI haplotype and negative Tajima D in samples from 2006/2007 fit with a population expansion model. In the older collections (1983 and 1993), a different haplotype is most prevalent, consistent with successive population contractions and expansions. Microsatellite data indicates recent migration between inland sites and coastal crops and admixture in several populations. Altogether, the data suggest that long‐distance dispersal occurs between arid and agricultural regions, and this, together with fluctuations in population size, leads to temporally dynamic patterns of genetic differentiation. Host‐associated differentiation is evident between mirids sampled from plants in the genus Cullen (Fabaceae), the primary host, and alternative host plant species growing nearby in arid regions. Our results highlight the importance of jointly assessing natural and agricultural environments in understanding the ecology of pest insects.     

Combining surveys of river habitats and river birds to appraise riverine hydromorphology

1. Biological monitoring is vital to river conservation. Aside from providing census data, regular monitoring may detect population trends that reflect the degradation or remediation of riverine environments. Birds are major candidates for this purpose because of their connections to riverine food webs and river habitat features. However, much information on factors affecting river bird distributions is qualitative. 2. River bird populations have been surveyed annually in the U.K. since 1974. The value of this monitoring could be increased if links between population trends and changes in riverine landscapes or channel hydromorphology were better understood. We modelled the relationships between bird species’ distributions recorded by the British Trust for Ornithology's Waterways Breeding Bird Survey (WBBS) and hydromorphology recorded by the Environment Agency's River Habitat Survey (RHS). 3. Regression models were built for 20 bird species associated with the river channel and neighbouring floodplains. This provided one of the first illustrations in ecology of generalized estimating equations (GEEs) for extending generalized linear models to instances where individual observations are not statistically independent. GEEs could offer a range of benefits to freshwater biologists, as they are a simple approach to analysing hierarchical, correlated data while maintaining the ease of interpretation with a range of link functions and data types. 4. Upland, fast water species and reedbed specialists showed the closest links with RHS, followed by lowland, slow water species, where correlations to RHS varied widely in magnitude. The distributions of floodplain wading birds were poorly modelled by RHS, suggesting that floodplain land uses as quantified by RHS were poor predictors of distributions. Marked preferences between upland and lowland channels were evident for most species. Specific features were also important, including hydraulics, bank/channel vegetation, depositional features and anthropogenic structures. 5. Monitoring the abundance and distribution of a range of bird species, with a diversity of life histories, could be a valuable tool for assessing trends in riverine landscapes and whole river basins. RHS captures useful information about channel hydromorphology and vegetation, but needs supplementing with additional environmental information to describe (i) the wider riverine landscape (e.g. more detailed floodplain variables, proximity of other waterbodies) and (ii) water chemistry. Although further work is required, this study suggests that WBBS and RHS add mutual value in appraising the river environment. We advocate the further development of birds as indicators in riverine landscapes that could convey the importance of the ecological integrity, biological production and conservation value of river systems to a wider audience.     

Species-environment relationships and vegetation patterns: effects of spatial scale and tree life-stage

Plant Ecology - Do relationships between species and environmental gradients strengthen or weaken with tree life-stage (i.e., small seedlings, large seedlings, saplings, and mature trees)?...     

Historical and contemporary mating patterns in remnant populations of the forest tree Fraxinus excelsior L

Genetic variation at microsatellite markers was used to quantify genetic structure and mating behavior in a severely fragmented population of the wind-pollinated, wind-dispersed temperate tree Fraxinus excelsior in a deforested catchment in Scotland. Remnants maintain high levels of genetic diversity, comparable with those reported for continuous populations in southeastern Europe, and show low interpopulation differentiation (E = 0.080), indicating that historical gene exchange has not been limited (Nm = 3.48). We estimated from seeds collected from all trees producing fruits in three of five remnants that F. excelsior is predominantly outcrossing (t(m) = 0.971 +/- 0.028). Use of a neighborhood model approach to describe the relative contribution of local and long-distance pollen dispersal indicates that pollen gene flow into each of the three remnants is extensive (46-95%) and pollen dispersal has two components. The first is very localized and restricted to tens of meters around the mother trees. The second is a long-distance component with dispersal occurring over several kilometers. Effective dispersal distances, accounting for the distance and directionality to mother trees of sampled pollen donors, average 328 m and are greater than values reported for a continuous population. These results suggest that the opening of the landscape facilitates airborne pollen movement and may alleviate the expected detrimental genetic effects of fragmentation.     

Protein conformational transitions coupled to binding in molecular recognition of unstructured proteins: hierarchy of structural loss from all-atom Monte Carlo simulations of p27Kip1 unfolding-unbinding and structural determinants of the binding mechanism

Conformational transitions coupled to binding are studied for the p27(Kip1) protein which undergoes a functional disorder-to-order folding transition during tertiary complex formation with the phosphorylated cyclin A-cyclin-dependent kinase 2 (Cdk2) binary complex. Temperature-induced Monte Carlo simulations of p27(Kip1) unfolding-unbinding carried out from the crystal structure of the tertiary complex have revealed a systematic trend in the hierarchy of structural loss for p27(Kip1) and a considerable difference in mobility of p27(Kip1) secondary structure elements. The most persistent interactions of p27(Kip1) at the intermolecular interface during unfolding-unbinding simulations are formed by beta-hairpin and beta-strand that on average maintain their structural integrity considerably longer than other p27(Kip1) elements. We have found that the ensemble of unfolded p27(Kip1) conformations is characterized by transitions between mostly unbound, collapsed conformations and entropically favorable p27(Kip1) conformations, which are weakly bound to the cyclin A side of the binary complex. The results of this study are consistent with the experimental evidence pointing to this region of the intermolecular interface as a potential initiation docking site during binding reaction and may reconcile conflicting experimental hypotheses on the recognition of substrate recruitment motifs.     

An exotic woody weed in a pastoral landscape provides habitat for many native species,but has no apparent threatened species conservation significance

Exotic woody plants are often used by native organisms, but may also be targets of expensive control justified by nature conservation. We determine the use of a weed of national significance, Gorse (Ulex europaeus L.), by native mammals, birds, reptiles and vascular plants in pastoral areas in an Australian biodiversity hotspot. Large numbers of fauna species were observed using Gorse within our 43 × 1 ha sample sites in riparian, woodland and pasture vegetation. Gorse cover and/or height positively influenced: the detection of mammals as a whole in an interaction with visibility at 50–75 cm above ground, but not their species richness or individual species abundances; bird abundance, but not richness; and, reptile richness but not abundance. In terms of flora, Gorse cover and/or height positively affected: non‐native plant species richness and the height and fecundity, but not the richness, of native grasses and forbs—but Gorse cover negatively influenced the height of native herbs. The only species of conservation significance using Gorse were three mammals, only one of which, the Tasmanian Pademelon (Thylogale billardieri), was sufficiently common to analyse. Its abundance had no relationship with Gorse cover or height. Even in the wider context of complementary work, there is no strong threatened species conservation justification for retaining Gorse thickets in the Northern Midlands pastoral landscape. Equally, expending scarce conservation resources to remove Gorse, as is taking place, is unlikely to achieve any threatened species conservation outcome but may help reduce long‐term loss of native animal and plant species.