共查询到20条相似文献，搜索用时 15 毫秒
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Jonathan S. Schurman Radek Bače Vojtěch Čada Shawn Fraver Pavel Janda Dominik Kulakowski Jana Labusova Martin Mikoláš Thomas A. Nagel Rupert Seidl Michal Synek Kristýna Svobodová Oleh Chaskovskyy Marius Teodosiu Miroslav Svoboda 《Global Change Biology》2018,24(5):2169-2181
Determining the drivers of shifting forest disturbance rates remains a pressing global change issue. Large‐scale forest dynamics are commonly assumed to be climate driven, but appropriately scaled disturbance histories are rarely available to assess how disturbance legacies alter subsequent disturbance rates and the climate sensitivity of disturbance. We compiled multiple tree ring‐based disturbance histories from primary Picea abies forest fragments distributed throughout five European landscapes spanning the Bohemian Forest and the Carpathian Mountains. The regional chronology includes 11,595 tree cores, with ring dates spanning the years 1750–2000, collected from 560 inventory plots in 37 stands distributed across a 1,000 km geographic gradient, amounting to the largest disturbance chronology yet constructed in Europe. Decadal disturbance rates varied significantly through time and declined after 1920, resulting in widespread increases in canopy tree age. Approximately 75% of current canopy area recruited prior to 1900. Long‐term disturbance patterns were compared to an historical drought reconstruction, and further linked to spatial variation in stand structure and contemporary disturbance patterns derived from LANDSAT imagery. Historically, decadal Palmer drought severity index minima corresponded to higher rates of canopy removal. The severity of contemporary disturbances increased with each stand's estimated time since last major disturbance, increased with mean diameter, and declined with increasing within‐stand structural variability. Reconstructed spatial patterns suggest that high small‐scale structural variability has historically acted to reduce large‐scale susceptibility and climate sensitivity of disturbance. Reduced disturbance rates since 1920, a potential legacy of high 19th century disturbance rates, have contributed to a recent region‐wide increase in disturbance susceptibility. Increasingly common high‐severity disturbances throughout primary Picea forests of Central Europe should be reinterpreted in light of both legacy effects (resulting in increased susceptibility) and climate change (resulting in increased exposure to extreme events). 相似文献
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Nonnative ungulates can alter the structure and function of forest ecosystems. Feral pigs in particular pose a substantial threat to native plant communities throughout their global range. Hawaiian forests are exceptionally vulnerable to feral pig activity because native vegetation evolved in the absence of large mammalian herbivores. A common approach for conserving and restoring forests in Hawaii is fencing and removal of feral pigs. The extent of native plant community recovery and nonnative plant invasion following pig removal, however, is largely unknown. Our objective was to quantify changes in native and nonnative understory vegetation over a 16 yr period in adjacent fenced (pig‐free) vs. unfenced (pig‐present) Hawaiian montane wet forest. Native and nonnative understory vegetation responded strongly to feral pig removal. Density of native woody plants rooted in mineral soil increased sixfold in pig‐free sites over 16 yr, whereas establishment was almost exclusively restricted to epiphytes in pig‐present sites. Stem density of young tree ferns increased significantly (51.2%) in pig‐free, but not pig‐present sites. Herbaceous cover decreased over time in pig‐present sites (67.9%). In both treatments, number of species remained constant and native woody plant establishment was limited to commonly occurring species. The nonnative invasive shrub, Psidium cattleianum, responded positively to release from pig disturbance with a fivefold increase in density in pig‐free sites. These results suggest that while common native understory plants recover within 16 yr of pig removal, control of nonnative plants and outplanting of rarer native species are necessary components of sustainable conservation and restoration efforts in these forests. 相似文献
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Epiphytes are conspicuous structural elements of tropical forest canopies. Individual tree crowns in lowland forests may support more than 30 ant species, yet we know little about the effects of epiphytes on ant diversity. We examined the composition of arboreal ant communities on Annona glabra trees and their interactions with the epiphytic orchid Caularthron bilamellatum in Panama. We surveyed the ants on 73 trees (45 with C. bilamellatum and 28 lacking epiphytes) and recorded their nest sites and behavioral dominance at baits. We found a total of 49 ant species (in 20 genera), ranging 1–9 species per tree. Trees with C. bilamellatum had higher average (±SD) ant species richness (4.2±2.28) than trees without epiphytes (2.7±1.21). Hollow pseudobulbs (PBs) of C. bilamellatum were used as nest sites by 32 ant species, but only 43 percent of suitable PBs were occupied. Ant species richness increased with PB abundance in trees, but nest sites did not appear to be a limiting resource on A. glabra. We detected no close association between ants and the orchid. We conclude that higher ant species richness in the presence of the orchid is due to bottom‐up effects, especially the year‐round supply of extrafloral nectar. The structure of ant communities on A. glabra partly reflects interference competition among behaviorally dominant species and stochastic factors, as observed in other forests. 相似文献
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E. Henry Lee Peter A. Beedlow Ronald S. Waschmann David T. Tingey Steven Cline Michael Bollman Charlotte Wickham Cailie Carlile 《Ecology and evolution》2017,7(24):11167-11196
The fungal pathogen, Phaeocryptopus gaeumannii, causing Swiss needle cast (SNC) occurs wherever Douglas‐fir is found but disease damage is believed to be limited in the U.S. Pacific Northwest (PNW) to the Coast Range of Oregon and Washington (Hansen et al., Plant Disease, 2000, 84, 773; Rosso & Hansen, Phytopathology, 2003, 93, 790; Shaw, et al., Journal of Forestry, 2011, 109, 109). However, knowledge remains limited on the history and spatial distribution of SNC impacts in the PNW. We reconstructed the history of SNC impacts on mature Douglas‐fir trees based on tree‐ring width chronologies from western Oregon. Our findings show that SNC impacts on growth occur wherever Douglas‐fir is found and is not limited to the coastal fog zone. The spatiotemporal patterns of growth impact from SNC disease were synchronous across the region, displayed periodicities of 12–40 years, and strongly correlated with winter and summer temperatures and summer precipitation. The primary climatic factor limiting pathogen dynamics varied spatially by location, topography, and elevation. SNC impacts were least severe in the first half of the 20th century when climatic conditions during the warm phase of the Pacific Decadal Oscillation (1924–1945) were less conducive to pathogen development. At low‐ to mid‐elevations, SNC impacts were most severe in 1984–1986 following several decades of warmer winters and cooler, wetter summers including a high summer precipitation anomaly in 1983. At high elevations on the west slope of the Cascade Range, SNC impacts peaked several years later and were the greatest in the 1990s, a period of warmer winter temperatures. Climate change is predicted to result in warmer winters and will likely continue to increase SNC severity at higher elevations, north along the coast from northern Oregon to British Columbia, and inland where low winter temperatures currently limit growth of the pathogen. Our findings indicate that SNC may become a significant forest health problem in areas of the PNW beyond the coastal fog zone. 相似文献
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Paulo C. Pulgarín‐R Juan P. Gómez Scott Robinson Robert E. Ricklefs Carlos Daniel Cadena 《Ecology and evolution》2018,8(8):3800-3814
Environmental factors strongly influence the ecology and evolution of vector‐borne infectious diseases. However, our understanding of the influence of climatic variation on host–parasite interactions in tropical systems is rudimentary. We studied five species of birds and their haemosporidian parasites (Plasmodium and Haemoproteus) at 16 sampling sites to understand how environmental heterogeneity influences patterns of parasite prevalence, distribution, and diversity across a marked gradient in water availability in northern South America. We used molecular methods to screen for parasite infections and to identify parasite lineages. To characterize spatial heterogeneity in water availability, we used weather‐station and remotely sensed climate data. We estimated parasite prevalence while accounting for spatial autocorrelation, and used a model selection approach to determine the effect of variables related to water availability and host species on prevalence. The prevalence, distribution, and lineage diversity of haemosporidian parasites varied among localities and host species, but we found no support for the hypothesis that the prevalence and diversity of parasites increase with increasing water availability. Host species and host × climate interactions had stronger effects on infection prevalence, and parasite lineages were strongly associated with particular host species. Because climatic variables had little effect on the overall prevalence and lineage diversity of haemosporidian parasites across study sites, our results suggest that independent host–parasite dynamics may influence patterns in parasitism in environmentally heterogeneous landscapes. 相似文献
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Angélica F. de Resende Bruce W. Nelson Bernardo M. Flores Danilo R. de Almeida 《Biotropica》2014,46(6):643-646
Neighboring upland and nutrient‐poor seasonally flooded Amazon forests were penetrated by a fire in 2009, providing a natural comparative experiment of fire damage for these widespread forest types. In upland, only 16 ± 10% (±2 SEM) of stems and 21 ± 8% of basal area were lost to fire, while seasonally flooded forest lost 59 ± 13% of stems and 57 ± 13% of basal area. Drier understory contributes to greater flammability. Much of the area occupied by seasonally flooded woody vegetation (>11.5 percent of the Amazon region) is vulnerable to fire due to high flammability and slow recovery. 相似文献
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Tropical forest loss and fragmentation can change bee community dynamics and potentially interrupt plant–pollinator relationships. While bee community responses to forest fragmentation have been investigated in a number of tropical regions, no studies have focused on this topic in Australia. In this study, we examine taxonomic and functional diversity of bees visiting flowers of three tree species across small and large rainforest fragments in Australian tropical landscapes. We found lower taxonomic diversity of bees visiting flowers of trees in small rainforest fragments compared with large forest fragments and show that bee species in small fragments were subsets of species in larger fragments. Bees visiting trees in small fragments also had higher mean body sizes than those in larger fragments, suggesting that small‐sized bees may be less likely to persist in small fragments. Lastly, we found reductions in the abundance of eusocial stingless bees visiting flowers in small fragments compared to large fragments. These results suggest that pollinator visits to native trees living in small tropical forest remnants may be reduced, which may in turn impact on a range of processes, potentially including forest regeneration and diversity maintenance in small forest remnants in Australian tropical countryside landscapes. 相似文献
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Gabriel Sangüesa‐Barreda Jan Esper Ulf Büntgen J. Julio Camarero Alfredo Di Filippo Michele Baliva Gianluca Piovesan 《Global Change Biology》2020,26(9):4988-4997
Long‐term tree recruitment dynamics of subalpine forests mainly depend on temperature changes, but little is known about the feedbacks between historical land use and climate. Here, we analyze a southern European, millennium‐long dataset of tree recruitment from three high‐elevation pine forests located in Mediterranean mountains (Pyrenees, northeastern Spain; Pollino, southern Italy; and Mt. Smolikas, northern Greece). We identify synchronized recruitment peaks in the late 15th and early 16th centuries, following prolonged periods of societal and climate instability. Major European population crises in the 14th and 15th centuries associated with recurrent famines, the Black Death pandemic, and political turmoil are likely to have reduced the deforestation of subalpine environments and caused widespread rewilding. We suggest that a distinct cold phase in the Little Ice Age around 1450 ce could also have accelerated the cessation of grazing pressure, particularly in the Pyrenees, where the demographic crisis was less severe. Most pronounced in the Pyrenees, the enhanced pine recruitment from around 1500–1550 ce coincides with temporarily warmer temperatures associated with a positive phase of the North Atlantic Oscillation. We diagnose that a mixture of human and climate factors has influenced past forest recruitment dynamics in Mediterranean subalpine ecosystems. Our results highlight how complex human–climate interactions shaped forest dynamics during pre‐industrial times and provide historical analogies to recent rewilding. 相似文献
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Euler Melo Nogueira Aurora M Yanai Frederico O R Fonseca Philip Martin Fearnside 《Global Change Biology》2015,21(3):1271-1292
The largest carbon stock in tropical vegetation is in Brazilian Amazonia. In this ~5 million km2 area, over 750 000 km2 of forest and ~240 000 km2 of nonforest vegetation types had been cleared through 2013. We estimate current carbon stocks and cumulative gross carbon loss from clearing of premodern vegetation in Brazil's ‘Legal Amazonia’ and ‘Amazonia biome’ regions. Biomass of ‘premodern’ vegetation (prior to major increases in disturbance beginning in the 1970s) was estimated by matching vegetation classes mapped at a scale of 1 : 250 000 and 29 biomass means from 41 published studies for vegetation types classified as forest (2317 1‐ha plots) and as either nonforest or contact zones (1830 plots and subplots of varied size). Total biomass (above and below‐ground, dry weight) underwent a gross reduction of 18.3% in Legal Amazonia (13.1 Pg C) and 16.7% in the Amazonia biome (11.2 Pg C) through 2013, excluding carbon loss from the effects of fragmentation, selective logging, fires, mortality induced by recent droughts and clearing of forest regrowth. In spite of the loss of carbon from clearing, large amounts of carbon were stored in stands of remaining vegetation in 2013, equivalent to 149 Mg C ha?1 when weighted by the total area covered by each vegetation type in Legal Amazonia. Native vegetation in Legal Amazonia in 2013 originally contained 58.6 Pg C, while that in the Amazonia biome contained 56 Pg C. Emissions per unit area from clearing could potentially be larger in the future because previously cleared areas were mainly covered by vegetation with lower mean biomass than the remaining vegetation. Estimates of original biomass are essential for estimating losses to forest degradation. This study offers estimates of cumulative biomass loss, as well as estimates of premodern carbon stocks that have not been represented in recent estimates of deforestation impacts. 相似文献
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Patrick A. Omeja Michael J. Lawes Amélie Corriveau Kim Valenta Dipto Sarkar Fernanda Pozzan Paim Colin A. Chapman 《Biotropica》2016,48(6):770-779
Tropical landscapes are changing rapidly as a result of human modifications; however, despite increasing deforestation, human population growth, and the need for more agricultural land, deforestation rates have exceeded the rate at which land is converted to cropland or pasture. For deforested lands to have conservation value requires an understanding of regeneration rates of vegetation, the rates at which animals colonize and grow in regenerating areas, and the nature of interactions between plants and animals in the specific region. Here, we present data on forest regeneration and animal abundance at four regenerating sites that had reached the stage of closed canopy forest where the average dbh of the trees was 17 cm. Overall, 20.3 percent of stems were wind‐dispersed species and 79.7 percent were animal‐dispersed species, while in the old‐growth forest 17.3 percent of the stems were wind‐dispersed species. The regenerating forest supported a substantial primate population and encounter rate (groups per km walked) in the regenerating sites was high compared to the neighboring old‐growth forests. By monitoring elephant tracks for 10 yr, we demonstrated that elephant numbers increased steadily over time, but they increased dramatically since 2004. In general, the richness of the mammal community detected by sight, tracks, feces, and/or camera traps, was high in regenerating forests compared to that documented for the national park. We conclude that in Africa, a continent that has seen dramatic declines in the area of old‐growth forest, there is ample opportunity to reclaim degraded areas and quickly restore substantial animal populations. 相似文献
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Improving our understanding of the potential of forest adaptation is an urgent task in the light of predicted climate change. Long‐term alternatives for susceptible yet economically important tree species such as Norway spruce (Picea abies) are required, if the frequency and intensity of summer droughts will continue to increase. Although Silver fir (Abies alba) and Douglas fir (Pseudotsuga menziesii) have both been described as drought‐tolerant species, our understanding of their growth responses to drought extremes is still limited. Here, we use a dendroecological approach to assess the resistance, resilience, and recovery of these important central Europe to conifer species the exceptional droughts in 1976 and 2003. A total of 270 trees per species were sampled in 18 managed mixed‐species stands along an altitudinal gradient (400–1200 m a.s.l.) at the western slopes of the southern and central Black Forest in southwest Germany. While radial growth in all species responded similarly to the 1976 drought, Norway spruce was least resistant and resilient to the 2003 summer drought. Silver fir showed the overall highest resistance to drought, similarly to Douglas fir, which exhibited the widest growth rings. Silver fir trees from lower elevations were more drought prone than trees at higher elevations. Douglas fir and Norway spruce, however, revealed lower drought resilience at higher altitudes. Although the 1976 and 2003 drought extremes were quite different, Douglas fir maintained consistently the highest radial growth. Although our study did not examine population‐level responses, it clearly indicates that Silver fir and Douglas fir are generally more resistant and resilient to previous drought extremes and are therefore suitable alternatives to Norway spruce; Silver fir more so at higher altitudes. Cultivating these species instead of Norway spruce will contribute to maintaining a high level of productivity across many Central European mountain forests under future climate change. 相似文献
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Large areas of tropical moist forests have been converted to cattle pastures, generating complex landscapes where different habitats are represented by small patches with an uneven spatial distribution. Here, we describe how bird communities respond to the different elements present in a livestock landscape that was originally dominated by tropical moist forest. We surveyed six habitats: open pastures, pastures with shrubs, early‐ and middle‐secondary forests, mature forest, and pastures invaded by bracken ferns (Pteridium aquilinum). Bird diversity was high in secondary and mature forests, and low in fern‐invaded sites and open pastures. Fern‐dominated sites had the lowest bird species richness, and trophic guild diversity of all habitats. Habitat structure affected both bird species richness and densities in similar ways. Tree species richness was the habitat attribute that had a bigger positive effect on bird species richness. Bird community structure varied among sampled habitats, separating habitats in two major groups (forests and pastures). Our data indicate that bracken fern‐invaded pastures were the worst habitat condition for avian communities. To increase bird diversity, we recommend to eliminate or manage bracken fern and to increase shrub and tree cover in open pastures to provide food resources and shelter for birds. Finally, we encourage the maintenance of secondary and mature forest remnants as a strategy to conserve resident birds within a landscape dominated by livestock activities. 相似文献
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C. P. S. Larsen 《Journal of Biogeography》1997,24(5):663-673
Abstract. Spatial and temporal variations in fire frequency in the boreal forest of Wood Buffalo National Park (WBNP) were assessed using forest stand age, fire scar and historical data. I test the hypotheses that (1) fire frequency is higher in jack pine forests and aspen forests than in black spruce forests and white spruce forests, (2) these variations in fire frequency can be related to the mean waterbreak distance (MWD) around a site and (3) fire frequency has changed over the past 300 years. The fire cycles (the time required to burn an area equal in size to the entire study area) in jack pine forests (39 years) and in aspen forests (39 years) were significantly shorter than those in black spruce forests (78 years) and in white spruce forests (96 years). The length of the fire cycle varies inversely with the MWD around a site, and the MWD was significantly higher in jack pine and aspen forests than in black or white spruce forests. It is suggested that covariations between soil type and the MWD influence, respectively, variations in forest dominant and fire frequency. A change in fire frequency at 1860 was apparent in the fire history for all of WBNP, the black spruce dominated stands, and the near and medium MWD classes. The fire cycle estimates for these classes were all significantly shorter during the period 1750 to 1859 (fire cycles = 25–49 years) than they were in the period 1860 to 1989 (fire cycles = 59–89 years). The possible roles of changes in climate and aboriginal burning practices in causing the temporal change in fire frequency are discussed. 相似文献
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Dick CW 《Molecular ecology》2008,17(8):1873-1874
Recent methodological advances permit refined inferences of evolutionary processes from the fine-scale spatial genetic structure of plant populations. In this issue of Molecular Ecology, Born et al. (2008) exploit the full power of these methods by examining effects of ancient and recent landscape histories in an African rainforest tree species. The authors first detected admixture of distinct gene pools that may have formed in Pleistocene forest refuges. Then, comparing across six study populations in Gabon, the authors found similar patterns of fine-scale spatial genetic structure despite natural and anthropogenic variation in population density. The latter results suggest that enhanced gene dispersal may compensate for low population densities in fragmented landscapes. 相似文献
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Ruth A. Gómez‐Rodríguez Gabriel Gutiérrez‐Granados Griselda Montiel‐Parra Ángel Rodríguez‐Moreno Víctor Sánchez‐Cordero 《Biotropica》2015,47(4):484-490
To understand the mechanisms driving species diversity is central to community ecology. Here, we explored if habitat partitioning is associated with a species‐rich ectoparasite community in small rodents from a tropical dry forest in western Mexico. We trapped 199 mice in three 0.5 ha‐plots from eight small rodent species for every two months, from July 2011 to April 2012, and collected their ectoparasites. We identified 17 species of mites, two sucking lice species, two phoretic species, and one commensal species. The most abundant ectoparasite species was Steptolaelaps liomydis, representing 42 percent of all ectoparasites collected; seven ectoparasite species had < 10 individuals. Eighteen ectoparasite species (of 22 species) were collected from the most abundant rodent Liomys pictus. C‐score and the number of checkerboard species pairs were significantly higher against a random expectation. Ectoparasite species in L. pictus mice showed host microhabitat partitioning; Fahrenholzia ehrlichi and Fahrenholzia texana were found only in the anterior dorsal area, Ornithonysus sp. occurred along the dorsal part, Ixodes species were restricted to the ears, and Steptolaelaps liomydis was found throughout the body. We also identified ectoparasite communities with distinct species composition in two rodent species that use contrasting macrohabitats (L. pictus, strictly terrestrial; Peromyscus perfulvus, mostly arboreal). The remaining and low abundant rodent species showed a species‐poor ectoparasite community composition. We conclude that habitat partitioning at both macro and microhabitat scales appeared to characterize the species‐rich ectoparasite community. Conversely, most rodent host species with low abundances showed a species‐poor ectoparasite community. 相似文献
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Yongle Du Alexander K. Abedi Ana Lisa Valenciano Maria L. Fernández‐Murga Maria B. Cassera Vincent E. Rasamison Wendy L. Applequist James S. Miller David G. I. Kingston 《化学与生物多样性》2017,14(12)
An extract of Malleastrum sp. (Meliaceae) collected in Madagascar by the Madagascar International Cooperative Biodiversity Group was found to have antimalarial activity, with an IC 50 value between 2.5 and 5 μg ml?1. After purification by liquid‐liquid partition, chromatography on a Diaion open column, C 18 SPE and C 18 reversed phase HPLC , the new butanolide, malleastrumolide A, was isolated. The structure of malleastrumolide A was determined by mass spectrometry, NMR , and ECD . The double bond position was determined by cross‐metathesis and mass spectrometry. The compound has antiproliferative activity against the A2780 ovarian cancer cell line with an IC 50 value of 17.4 μm and antiplasmodial activity against the drug‐resistant Dd2 strain of Plasmodium falciparum with an IC 50 value of 2.74 μm . 相似文献