Bird communities in traditional wood-pastures with changing management in Eastern Europe

Wood-pastures are fragile ecosystems because they were formed by, and depend on specific, low-intensity multifunctional management. Although their ecological and cultural significance is high, wood-pastures are rapidly deteriorating all over Europe, mainly due to changing land use. We still lack a basic understanding of the ecological value of wood-pastures, and in which features they differ from other landscape elements. In this paper we investigated the ecological value of wood-pastures for passerine birds by (i) comparing bird assemblages of wood-pastures with those of closed forests and open pastures and (ii) exploring the relationships between variables describing wood-pastures and species traits of the bird assemblages. Our study region (Southern Transylvania, Romania) provides a unique opportunity to understand the importance of a traditional cultural and ecological environment for many different organisms. Wood-pastures had a higher overall number of bird species, and a higher spatial turnover in bird community composition than closed forests and open pastures. We found significant associations between bird species traits and habitat structural elements in wood-pastures such as large trees, oak- and pear trees and shrubs. Our findings suggest that traditional wood-pastures in Southern Transylvania have distinct and rich passerine bird communities. This richness is inextricably linked to the multifunctional, low-intensity land use traditionally applied in the wood-pastures that promotes high niche diversity. For effective conservation of the biodiversity of wood-pastures, a detailed understanding is needed of how different management regimes may influence the key structural elements of wood-pastures relevant for biodiversity and these should be protected.     

混交对亚热带针叶树根际土壤氮矿化和微生物特性的影响

混交阔叶树是退化红壤区针叶林改造的重要措施之一，土壤养分供应和转化是评价混交效应的重要参数，但混交后针叶树根际土壤氮矿化特征及其影响因素还不清楚。选取退化红壤区马尾松（Pinus massoniana Lamb.）纯林、湿地松（Pinus elliottii Engelmann）纯林及其补植木荷（Schima superba Gardn.et Champ.）形成的马-木混交林和湿-木混交林为研究对象，采集4种林分下针叶树根际土壤，测定速效养分含量、氮矿化速率、氮水解酶活性和微生物磷脂脂肪酸含量，探究混交对针叶树根际土壤氮供应及微生物特性的影响，分析土壤氮矿化和微生物特性间的相关性。结果表明：混交显著增加了针叶树根际土壤铵态氮，矿质氮和有效磷含量，而对硝态氮影响不显著。根际土壤氮矿化以硝化作用为主，混交后针叶树根际土壤氨化速率降低了27.0%，硝化速率增加了55.4%，而最终净氮矿化速率增加了24.1%。两个树种间，马尾松根际土壤矿质氮含量和净氮矿化速率显著高于湿地松。针叶树根际土壤真菌、丛枝菌根真菌，总微生物生物量及真菌/细菌比在混交后显著增加，且马尾松根际土壤总微生物和真菌生物量分别比湿地松高18.9%和27.0%。同时，针叶树根际土壤β-N-乙酰氨基葡萄糖苷酶活性在混交后显著增强，且根际土壤硝化速率和净氮矿化速率与微生物指标和酶活性正相关。总的来说，混交阔叶树显著提高了针叶树根际土壤氮供应，以此应对阔叶树混交后带来的养分竞争压力，而马尾松倾向于积极性的应对策略，通过增加土壤氮矿化以适应外界环境改变。     

Fine‐scale Population Genetic Structure of Two Dioecious Indian Keystone Species,Ficus hispida and Ficus exasperata (Moraceae)

Although Ficus (Moraceae) is a keystone plant genus in the tropics, providing resources to many frugivorous vertebrates, its population genetic structure, which is an important determinant of its long‐term survival, has rarely been investigated. We examined the population genetic structure of two dioecious fig species (Ficus hispida and Ficus exasperata) in the Indian Western Ghats using co‐dominant nuclear microsatellite markers. We found high levels of microsatellite genetic diversity in both species. The regression slopes between genetic relationship coefficients (f_ij) and spatial distances were significantly negative in both species indicating that, on average, individuals in close spatial proximity were more likely to be related than individuals further apart. Mean parent–offspring distance (σ) calculated using these slopes was about 200 m in both species. This should be contrasted with the very long pollen dispersal distances documented for monoecious Ficus species. Nevertheless, overall population genetic diversity remained large suggesting immigrant gene flow. Further studies will be required to analyze broader scale patterns.     

Ecophysiology of six selected shrub species in different plant communities at the periphery of the Atlantic Forest of SE-Brazil

The Atlantic rain forest of Brazil is one of the 25 biodiversity hotspots of the world. It is surrounded by distinct marginal plant communities which are floristically related to the rain forest. We performed an in situ ecophysiological study of six shrub and tree species which are abundant in one or more of these marginal ecosystems. They formed three pairs of taxonomically related species, which, however, differed in geographic distribution and/or habitat preference. We aimed to answer the following questions: (1) Do habitat generalists and specialists differ in ecophysiological behaviour? (2) Are there general trends responsive to site characteristics, irrespective of taxonomic affiliation? (3) In which variables between-site intraspecific variation is more often detected? Plants chosen were the Clusiaceae Calophyllum brasiliense Cambess (swamp forest specialist) and Rheedia brasiliensis (Mart.) Planch &; Triana (a generalist plant, occurring in swamp forests and dry, sandy coastal vegetation); the Myrsinaceae Myrsine parvifolia A.DC. (widespread in sandy plains) and Myrsine gardneriana A.DC. (widespread in high-altitude habitats); and the Euphorbiaceae Styllingia dichotoma Muell. Arg. (a coastal inselberg specialist) and Croton compressus Lam. (a generalist found in coastal inselbergs and dry forests). We compared measurements of photosynthesis (chlorophyll fluorescence parameters), stable isotope (δ¹³C, δ¹⁵N) and metabolic carbon and nitrogen compounds. Generalists and specialists did not always differ in ecophysiological behaviour: for instance, while widespread generalists such as M. parvifolia and C. compressus were ecophysiologically versatile, R. brasiliense appeared to perform below optimum in all sampled habitats. Light and water were abiotic factors which apparently explained most of the variation found. Overall, ecophysiological responses were often more clearly related to individual species rather than to taxonomic affinities in higher hierarchies (family, genus) or habitat. These results are discussed as a further indication of high biodiversity even in habitats marginal to the rain forest hotspot.     

城市行道树对交通环境的响应

以远离交通环境的公园作为相对清洁区,研究了位于广东佛山种植最普遍的8种城市行道树树黄葛榕(FicusvirensAit.var.sublanceolata(Miq.)Corner),大叶紫薇(Lagerstroemiaspeciosa(L.)Pers.),芒果(MangiferaindicaL.),细叶榕(FicusmicrocarpaL.),阴香(Cinnamomumburmanii(Nees)Bl.),垂叶榕(FicusbenjaminaL.),白兰(MicheliaalbaDC.),红花羊蹄甲(BauhiniablakeanaDunn)在交通密集区生长在不同方位的植物器官对交通环境的响应。结果表明,交通密集区的城市行道树的叶片和树皮器官吸收重金属铅和镉、硫含量、电导率和pH值等指标在不同的方位呈现显著的差别,即城市行道树位于快车道一侧生长的植物的器官(以下简称P1)、位于面向人行道一侧生长的植物的器官(以下简称P2)及相对清洁区采集的植物样品(以下简称P0)各指标测定值的分析结果为:其叶片和树皮硫、重金属铅和镉、电导率等特征值基本呈现P1>P2>P0的大小规律,在显著度为0.05时差异显著;而pH值基本呈现P1相似文献   

Synthesis of a 13C-Labeled Tracer for Stream DOC: Labeling Tulip Poplar Carbon with 13CO2

Ecosystem tracer-level additions would benefit from a stable isotope-labeled source of complex organic molecules. We tested a method to label tree C with ¹³C and create a stable isotope tracer for stream dissolved organic carbon (DOC) using tulip poplar (Liriodendron tulipifera L.) seedlings. In 2000, seedlings were grown with 0.82 moles of ¹³CO₂ to assess the distribution and level of ¹³C enrichment in the tree tissues. In 2001, seedlings were grown with 25 times more ¹³CO₂ to generate tissues with a ¹³C signal strong enough for a ¹³C-DOC stream tracer addition. ¹³C enrichment in the trees varied in each year and by tissue age and type. Tissues formed during labeling (new) were more enriched in ¹³C than tissues established prior to the ¹³CO₂ injection (old). Stems were most enriched in ¹³C in both new and old tissues. A higher percentage of ¹³CO₂ was incorporated into seedlings in 2000 (59% ±1) than 2001 (43% ±0). Percent ¹³C incorporation among tree tissue types paralleled biomass distributions. Although tree C and ¹³C were equally soluble in both years, a greater percentage of tree C went into solution in 2001 (30%) than 2000 (20%). The water-soluble tree C accounted for approximately 12% of the injected ¹³CO₂ and had both humic and polysaccharide components. Results from a whole-stream ¹³C-DOC tracer addition demonstrated that tree C could be sufficiently labeled with ¹³CO₂ to create a stream DOC isotope tracer with some polymeric constituents.     

Beringia as a glacial refugium for boreal trees and shrubs: new perspectives from mapped pollen data

Aim Beringia, far north‐eastern Siberia and north‐western North America, was largely unglaciated during the Pleistocene. Although this region has long been considered an ice‐age refugium for arctic herbs and shrubs, little is known about its role as a refugium for boreal trees and shrubs during the last glacial maximum (LGM, c. 28,000–15,000 calibrated years before present). We examine mapped patterns of pollen percentages to infer whether six boreal tree and shrub taxa (Populus, Larix, Picea, Pinus, Betula, Alnus/Duschekia) survived the harsh glacial conditions within Beringia. Methods Extensive networks of pollen records have the potential to reveal distinctive temporal–spatial patterns that discriminate between local‐ and long‐distance sources of pollen. We assembled pollen records for 149 lake, peat and alluvial sites from the Palaeoenvironmental Arctic Sciences database, plotting pollen percentages at 1000‐year time intervals from 21,000 to 6000 calibrated years before present. Pollen percentages are interpreted with an understanding of modern pollen representation and potential sources of long‐distance pollen during the glacial maximum. Inferences from pollen data are supplemented by published radiocarbon dates of identified macrofossils, where available. Results Pollen maps for individual taxa show unique temporal‐spatial patterns, but the data for each taxon argue more strongly for survival within Beringia than for immigration from outside regions. The first increase of Populus pollen percentages in the western Brooks Ranges is evidence that Populus trees survived the LGM in central Beringia. Both pollen and macrofossil evidence support Larix survival in western Beringia (WB), but data for Larix in eastern Beringia (EB) are unclear. Given the similar distances of WB and EB to glacial‐age boreal forests in temperate latitudes of Asia and North America, the widespread presence of Picea pollen in EB and Pinus pollen in WB indicates that Picea and Pinus survived within these respective regions. Betula pollen is broadly distributed but highly variable in glacial‐maximum samples, suggesting that Betula trees or shrubs survived in restricted populations throughout Beringia. Alnus/Duschekia percentages show complex patterns, but generally support a glacial refugium in WB. Main conclusions Our interpretations have several implications, including: (1) the rapid post‐glacial migration rate reported for Picea in western Canada may be over estimated, (2) the expansion of trees and shrubs within Beringia should have been nearly contemporaneous with climatic change, (3) boreal trees and shrubs are capable of surviving long periods in relatively small populations (at the lower limit of detection in pollen data) and (4) long‐distance migration may not have been the predominant mode of vegetation response to climatic change in Beringia.