Martinez-Lanfranco, Juan AndresVilella, Francisco J.Miller, Darren A.
14页
查看更多>>摘要：Establishing commercial tree plantations in native grassland ecosystems introduces a different structural and functional vegetation cover type, with expected implications for biodiversity. To better understand biodiversity responses to afforestation, we conducted a resource-use study with birds as a focal group, during the 2013-2014 breeding season in the Northern Campos grasslands of Uruguay. We sampled birds in native environments and plantations of loblolly pine (Pinus taeda) and flooded gum (Eucalyptus grandis) at different rotation stages. We recorded 103 species during 1,573 visits (10-min, 50-meter radius point counts) to 570 stratified sampling units. Native grasslands and forests exhibited greater diversity and had greater variability in species composition than structurally homogeneous plantations. Avian communities in plantations had distinct species combinations and relative abundances not found in native conditions. Avian communities in older plantations were more similar to native forests while those of newly-planted stands were more like grasslands. However, plantations were dominated by habitat generalists and some forest-dependent species, with negligible use by grassland specialist birds. Our results suggest the best conservation opportunities for grassland-dependent birds in afforested systems of the Campos of Uruguay may depend on diverse landscape-level measures rather than stand-level management practices. Albeit our research constituted a comprehensive assessment of bird taxonomic alpha and beta di-versity, research on complementary diversity facets and multi-scale resource selection and demographic studies are needed to better understand the fitness implications for conserving and managing grassland birds in affor-ested landscapes.
Bisbing, Sarah M.Buma, Brian J.Vander Naald, BrianBidlack, Allison L....
9页
查看更多>>摘要：Cost-benefit analyses of salvage logging have generally focused on large-scale, landscape disturbances salvaged at high intensity, and there is limited research on the ecological and economic outcomes of low-intensity salvage implemented for the benefit of forest-dependent communities. Here, we assess the potential impacts of smallscale, single-tree salvage logging of a foundation tree species (yellow-cedar, Callitropsis nootkatensis) on ecological integrity against the viability of salvaged wood as a source of timber for cultural and economic purposes. We designed a salvage logging demonstration project in southeast Alaska, USA, and leveraged adjacent salvaged and unsalvaged, reference stands to: 1) investigate the degree to which salvage alters ecological integrity, defined by the abundance of yellow-cedar and post-disturbance stand trajectories, 2) track the volume and kinds of timber products generated by salvage logging activity, and 3) analyze the costs and revenues associated with the harvest and manufacturing of these products. Our results suggest that small-scale, single tree salvage logging has limited impact on yellow-cedar abundance and its potential to serve its foundation species role in forest successional trajectories while providing small to modest economic returns, though with large heterogeneity in net revenue among mill operators. Our findings indicate that salvage at this scale and intensity maintains ecological integrity but with limited economic viability. This management tool is thus best suited for land managers addressing multiple resource objectives in communities dependent on small, continuous streams of forest products.
Lefoe, MatthewRendall, Anthony R.McKinnon, FreyaWhisson, Desley A....
8页
查看更多>>摘要：Habitat loss and degradation are two of the greatest threats to biodiversity conservation globally. In Australia, the incidence of wildfire and native forest logging contribute substantially to these processes and have been linked to reduced species diversity and abundance. Arboreal species such as the Yellow-bellied Glider (Petaurus australis), are thought to be susceptible to these disturbances due to their reliance on large patches of forest and hollow-bearing trees. We aimed to assess the impact of logging and wildfire on site occupancy by the Yellow-bellied Glider in Mountain Ash forests of the Central Highlands of Victoria. We deployed autonomous recording units for 14 nights at 70 sites and searched recordings for Yellow-bellied Glider vocalisations. Yellow-bellied Gliders were detected at 30% (N = 21) of sites. Site occupancy increased with an increasing proportion of the landscape (within 400 m of the recorder) that had not been logged within the last 100 years or burnt by wildfire within the last 10 years. Habitat disturbance caused by logging and fire therefore limit the site occu-pancy of Yellow-bellied Gliders and likely impact its conservation status. It is therefore critical that appropriate management of timber resources protects large patches of old-growth forest providing food resources and hol-lows, and the connectivity between large forest patches.
查看更多>>摘要：The Canadian province of Alberta is densely dissected by seismic lines - linear disturbances used for oil and gas exploration. Natural recovery of seismic lines to pre-disturbance treed conditions in boreal ecosystems is generally slow, and persistence of seismic lines is particularly notable in peatlands, including treed bogs. A functional trait approach can help understand the mechanisms that drive community composition and structure following a disturbance. We explored the role of environmental filters (soil moisture, soil temperature, light, and growing substrate) on vascular species composition and functional community structure on seismic lines in a treed bog near Peace River, NW Alberta. We investigated successional trajectories on seismic lines constructed between 1951 and 1986, and the impact of seismic line orientation (N-S and E-W). We also compared taxonomic and functional trait composition of plots on seismic lines, at the line edges, and in the adjacent treed bog, 75 m away from the edge. We found no differences in plant species and functional trait composition based on the seismic line age and line orientation, confirming that seismic lines are not following the expected successional trajectories frequently observed in boreal ecosystems after other disturbances such as logging or fire. Taxonomic and functional composition were different on seismic lines compared to the line edges and interior treed bog, further supporting that the lines are different from the pre-disturbance conditions. Seismic lines had a few trees, received more light, and were wetter, with an abundant deep layer of waterlogged Sphagnum, whereas the adjacent treed bog had a dense mature overstory and was drier with a higher cover of feathermoss. Seismic lines included primarily shorter species with extensive lateral expansion, which is consistent with a high abundance of low ericaceous shrubs on the lines. Dominance of ericaceous shrubs likely also played a role in low presence of herbaceous species on the lines, which is related to the low presence of hemicryptophytes, compared to the adjacent treed bog. It is unlikely that the historic seismic lines in treed bogs of Alberta will follow expected successional trajectories over the next decades without outside intervention. However, better understanding of the mechanisms that control ecosystem functioning based on taxonomic and functional community composition observed on seismic lines can inform restoration and mitigation measures needed for seismic line recovery.
Sanz-Benito, IgnacioMediavilla, OlayaCasas, AdrianaOria-de-Rueda, Juan Andres...
10页
查看更多>>摘要：Wildfire is a recurrent factor that shapes and influences Mediterranean ecosystems where mixed oak (Quercus) forests with a rockrose (Cistus) understory are broadly represented. These ecosystems are also associated with large and diverse fungal communities. These fungal communities play essential ecological roles for the survival of vascular plant, such as the mineral and water uptaking or resistance against pathogens carried out by mycorrhizal fungi, as the saprotrophic fungi are a key factor for the recycling of the dead matter. In addition, edible fungi, such as Boletus edulis, provide a source of income for the nearby rural population. Fuel reduction treatments are applied to reduce the risk of wildfire; however, their potential impact on fungal communities is unclear. Thus, the aim of this work was to investigate the effect of different fuel reduction treatments on fungi associated with Quercus and Cistus. This aim is accompanied by the management-driven objective to obtain data from fuel reduction treatments that will enable managers to find solutions with a balanced approach to maintaining productive areas of edible mushroom production while reducing fire risks across the landscape. Sporocarps were sampled over a five-year period in stands dominated by mature or coppiced Quercus pyrenaica and accompanied by Cistus ladanifer understory. These stands had been subjected to different fuel reduction treatment levels involving moderate-or high-intensity thinning, for Q. pyrenaica, or clearing, for C. ladanifer. The goal was to determine sporocarp production, species richness, and taxonomic composition. Sporocarp production and fungal richness were drastically affected by the fuel reduction treatments but only when C. ladanifer is included in the treatment. Taxa composition was strongly correlated with the treatments applied to the rockrose under story. This was probably due to the large range of associated ectomycorrhizal fungi of C. ladanifer and their high capacity to recolonize an area after disturbances. Based on our results, we conclude that the implementation of moderate-/high-intensity fuel reduction treatments is compatible with the conservation of the fungal community present in these systems. In addition, the creation of a multi-stage mosaic of stands through mechanical management could enable fire prevention to be managed in an effective way while maintaining fungal diversity and sporocarp production, favoring the use of non-wood resources in rural areas and conserving a healthier forest ecosystem.
查看更多>>摘要：The dynamics of the alpine forest boundary and the mechanisms behind have long been the ecological research hotspots. Growing season temperature (T-gs) decreases along with altitude gradients limiting alpine treeline has become the widely accepted mechanism among various theories. However, the physiological process amid T-gs limitation of the alpine treeline is still not well understood. Here, we measured leaf hydraulic conductance (K-l), stem hydraulic conductance (K-s), leaf and stem anatomic structures, and leaf saturated photosynthetic rate (A(sat)) of 11 tree and shrub species naturally distributed along the altitude gradients towards the typical alpine treeline in the north face of Qilian Mountains. We found, irrespective of interspecies or intraspecies, K-l and K-s both significantly decreased along the altitude gradients, and the species distributed in the high altitude with rather low K-l and K-s. The decrease of leaf midvein and stem xylem vessel diameter were the anatomical cause of the decreases of K-l and K-s. Further analysis proved that the decreased T-gs, not growing season precipitation (P-gs), was closely coordinated with the decrease of K-l and K-s along altitude gradients. The path analysis showed that the decreased T-gs, K-l, and K-s along the altitude gradients negatively influenced A(sat), and thereby limits the species survival in high altitudes. The findings proposed the physiological constraints of the alpine forest treeline and provided the physiological insights for alpine forest management and conservation.
Reed, Sharon E.Volk, DanielMartin, Danielle K. H.Hausman, Constance E....
11页
查看更多>>摘要：Over the past century, beech bark disease has dramatically altered the composition and structure of stands containing American beech (Fagus grandifolia). Management of beech bark disease has focused on reducing beech thickets and identifying resistant trees in aftermath forests. Beech leaf disease is a recently detected invasive disease, now also affecting beech forests. In 2019, a plot network was established in central North America to examine the extent of beech leaf disease spread and the severity of effects on trees and forests. Here, data from this plot network was used to determine the extent to which American beech is exposed to beech leaf disease, beech scale (Cryptococcus fagisuga), and beech bark disease (C. fagisuga and Neonectria spp. complex) in forests surrounding the Great Lakes in southwestern Ontario, northeastern Ohio, western Pennsylvania, and western New York. Beech leaf disease and scale were found to be well established, not only among sites but also in the different canopy layers. Beech bark disease was present, but occurrence was low. Pest accumulation differed between overstory and sapling layers. Beech leaf disease was the primary pest of saplings while both beech leaf disease and beech scale dominated in the overstory. Forest composition was similar throughout the study range; American beech, sugar maple, red maple, and white ash were abundant and common in the sapling and seedling layer. Few invasive plants were evident among saplings and seedlings. Sugar maple and red maple will likely fill small canopy gaps following beech decline or mortality. Intervention should be considered in stands with po-tential for increasing tree diversity or promoting beech leaf disease-resistant American beech trees to the overstory. New strategies are needed for beech conservation along with research to determine the extent of beech leaf disease resistance in American beech.
查看更多>>摘要：Since the industrial revolution, atmospheric nitrogen deposition has increased strongly and has been shown to alter nitrogen cycles, species composition and diversity in many ecosystems, including forests. At the same time, nitrogen removal from forests through biomass extraction via historical management techniques has decreased considerably. A proven tool to analyze the effects of long-term environmental changes are vegetation resurveys. In this study, we tested whether environmental changes resulting from atmospheric nitrogen deposition and altered forest management are reflected in the vegetation composition of temperate forest understories in six acidophilic and oligo-mesophilic forest types in south-western Germany. We compared historical surveys from 1950 to 1976 with surveys from 2017/18 and examined changes in the vegetation using NMDS ordinations and Ellenberg indicator values. While an increase in the number of nitrophilic species was detected in all forest types, only the acidophytic and oligotrophic Vaccinio-Abietetum and Luzulo-Quercetum forests (dominated by Abies alba (Mill.) and Quercus spec., respectively) exhibited a replacement of oligotrophic species by nitrophilic species, amounting to an overall trend of eutrophication. Despite the uncertainties resulting from different plot locations and the slow dynamics of forests, we demonstrate a significant trend in the understory vegetation composition, which is likely caused by atmospheric N deposition. Differences in the sensitivity of different forest types indicate an influence of geological and climatic site characteristics and historical land use on the effects of environmental changes.
查看更多>>摘要：Tree bark, as the outermost protective layer of tree stems, is an important indicator to evaluate the fire resistance properties of trees and to assess the tree mortality induced by fire. Despite its importance, many existing bark thickness models were not primarily developed for predicting bark thickness directly, i.e. with bark thickness as a response variable, and most past studies were focused on modeling bark thickness in conifers. Thus, the objective of this study was to compare the efficacy of various bark thickness models/methods for three common hardwood species in the southeastern US. A total number of 47,281 measurements from 2,070 trees were used in analysis. Results showed that bark thickness at breast height (1.37 m or 4.5 ft above ground) varies by tree size and species, which can be predicted by a species-specific linear regression model with DBH as a single predictor. To predict bark thickness profile, a combination of stem taper function and bark thickness model, a two-stage method, is suggested, which generally performs better than a single bark thickness function (one-stage method) in terms of bias and precision. For a given model form, the two-stage method produced more reliable prediction of bark thickness at upper and lower portions of tree stem than the one-stage method. With the three species examined, the segmented stem taper functions provided more accurate predictions than the variable exponent function. The results of this study can provide guidance for ecologists and forest managers when selecting appropriate approaches to predict bark thickness.
NSTL
Elsevier