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1.
Abstract: Ponderosa pine (Pinus ponderosa) forests with Gambel oak (Quercus gambelii) are associated with higher bird abundance and diversity than are ponderosa pine forests lacking Gambel oak. Little is known, however, about specific structural characteristics of Gambel oak trees, clumps, and stands that may be important to birds in ponderosa pine-Gambel oak (hereafter pine-oak) forests. We examined associations among breeding birds and structural characteristics of Gambel oak at a scale similar in size to individual bird territories in pine-oak forests in northern Arizona and western New Mexico, USA. Avian species richness and occurrence of some bird species were associated with specific growth forms of Gambel oak. Estimated probability of Virginia's warblers (Vermivora virginiae), black-headed grosbeaks (Pheucticus melanocephalus), and red-faced warblers (Cardellina rubrifrons) occurring at points increased with increasing density of pole-sized Gambel oak 7–15 cm in diameter at breast height. We also found evidence that large Gambel oak trees (≥23 cm dbh) were associated with increased occurrence of yellow-rumped warblers (Dendroica coronata) at points. Some avian associations with oak were influenced by characteristics of ponderosa pines. For example, bird species richness was positively associated with the abundance of large Gambel oak when density of large pine trees ≥23 cm in diameter at breast height was low. Because large oak trees are rare and their numbers are thought to be declining, efforts should be made to retain and promote growth of additional oaks in this size class. Forest management practices that maintain forest openings, such as prescribed burning, could promote growth of pole-sized Gambel oak, which appears important to some bird species in pine-oak forests.  相似文献   

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3.
The term “keystone species” is used to describe organisms that exert a disproportionately important influence on the ecosystems in which they live. Analogous concepts such as “keystone mutualism” and “mobile links” illustrate how, in many cases, the interactions of two or more species produce an effect greater than that of any one species individually. Because of their role in transporting nutrients from the ocean to river and riparian ecosystems, Pacific salmon (Oncorhynchus spp.) and brown bear (Ursus arctos) have been described as keystone species and mobile links, although few data are available to quantify the importance of this interaction relative to other nutrient vectors. Application of a mass balance model to data from a southwestern Alaskan stream suggests that nitrogen (N) influx to the riparian forest is significantly increased in the presence of both salmon and bear, but not by either species individually. The interactions of salmon and bear may provide up to 24% of riparian N budgets, but this percentage varies in time and space according to variations in salmon escapement, channel morphology and watershed vegetation characteristics, suggesting interdependence and functional redundancy among N sources. These findings illustrate the complexity of interspecific interactions, the importance of linkages across ecosystem boundaries and the necessity of examining the processes and interactions that shape ecological communities, rather than their specific component parts.  相似文献   

4.
 Isolates from two species of Morchella were tested for ability to form mycorrhizae in pure culture synthesis with Arbutus menziesii, Larix occidentalis, Pinus contorta, Pinus ponderosa, andPseudotsuga menziesii. Ectomycorrhizal structures (mantle and Hartig net) formed with the four species of the Pinaceae but not with A. menziesii. Results are compared to previous studies on morel mycorrhizae and discussed in an ecological context. Accepted: 23 October 1999  相似文献   

5.
Abstract: We studied breeding populations of 2 coexisting ground-nesting birds, the red-faced warbler (Cardellina rubrifrons) and yellow-eyed junco (Junco phaeonotus), in high-elevation (>2,000 m) forested drainages of the Santa Catalina Mountains, Arizona, USA. From 2004 to 2005, we 1) estimated density and nesting success of breeding populations of red-faced warblers and yellow-eyed juncos, 2) identified nest-site characteristics for each species (i.e., used sites vs. random plots), 3) compared nest-site characteristics between the 2 species, and 4) examined effects of a recent (2003) wildfire on distribution of nests of both species. In addition, we estimated the areal extent of montane riparian forest (the preferred breeding habitat of both species) within high-elevation forests of the Santa Catalina Mountains. We found that red-faced warblers and yellow-eyed juncos were the 2 most common ground-nesting birds within our study area with an average density of 2.4 and 1.4 singing males/ha, respectively, along drainage bottoms. Compared to random plots, most red-faced warbler and yellow-eyed junco nests were located close (≤30 m) to drainage bottoms within a strip of montane riparian forest characterized by abundant brush, small woody debris, ferns, and forbs (both species), high number and diversity of saplings and small trees (red-faced warblers), and abundant shrubs and downed logs and less canopy cover (yellow-eyed juncos). Although both species nested in close proximity within montane riparian forest, nest-site characteristics differed between the 2 species, especially at finer spatial scales. For example, most yellow-eyed juncos nested adjacent to grass (principally Muhlenbergia spp.), whereas red-faced warblers nested adjacent to a variety of plant species, including grass, bigtooth maple (Acer grandidentatum), white fir (Abies concolor), and Douglas-fir (Pseudotsuga menziesii). Both red-faced warblers and yellow-eyed juncos avoided nesting in areas burned during a recent wildfire. In addition, nesting success was low for red-faced warblers (13%) and yellow-eyed juncos (19%) following the wildfire, suggesting an indirect negative effect of fire on breeding populations in the short-term. Montane riparian forest appears to provide important breeding habitat for red-faced warblers and yellow-eyed juncos. However, little research or conservation planning has been directed toward montane riparian forest in the region, even though this forest type is limited in its areal extent (<11% of high-elevation forest in the Santa Catalina Mountains) and increasingly threatened by disturbance. Results from our study can be used to facilitate the management and conservation of breeding populations of red-faced warblers and yellow-eyed juncos in high-elevation forests of the southwestern United States.  相似文献   

6.
以江西武夷山国家级自然保护区河岸带阔叶林群落为研究对象,对其物种组成进行调查,并采用物种丰富度指数、多样性指数和均匀度指数分析物种多样性。结果表明,保护区河岸带物种极丰富,三条水系10个样方中共调查到维管束植物93科174属304种,群落建群种和灌木层优势种均以常绿阔叶树种为主,物种组成具有典型的亚热带植被特色,以壳斗科、樟科、山茶科物种最多。保护区不同海拔河岸带物种丰富度指数、多样性指数的变化规律基本一致。  相似文献   

7.
Aim Forest restoration in ponderosa pine and mixed ponderosa pine–Douglas fir forests in the US Rocky Mountains has been highly influenced by a historical model of frequent, low‐severity surface fires developed for the ponderosa pine forests of the Southwestern USA. A restoration model, based on this low‐severity fire model, focuses on thinning and prescribed burning to restore historical forest structure. However, in the US Rocky Mountains, research on fire history and forest structure, and early historical reports, suggest the low‐severity model may only apply in limited geographical areas. The aim of this article is to elaborate a new variable‐severity fire model and evaluate the applicability of this model, along with the low‐severity model, for the ponderosa pine–Douglas fir forests of the Rocky Mountains. Location Rocky Mountains, USA. Methods The geographical applicability of the two fire models is evaluated using historical records, fire histories and forest age‐structure analyses. Results Historical sources and tree‐ring reconstructions document that, near or before ad 1900, the low‐severity model may apply in dry, low‐elevation settings, but that fires naturally varied in severity in most of these forests. Low‐severity fires were common, but high‐severity fires also burned thousands of hectares. Tree regeneration increased after these high‐severity fires, and often attained densities much greater than those reconstructed for Southwestern ponderosa pine forests. Main conclusions Exclusion of fire has not clearly and uniformly increased fuels or shifted the fire type from low‐ to high‐severity fires. However, logging and livestock grazing have increased tree densities and risk of high‐severity fires in some areas. Restoration is likely to be most effective which seeks to (1) restore variability of fire, (2) reverse changes brought about by livestock grazing and logging, and (3) modify these land uses so that degradation is not repeated.  相似文献   

8.
Riparian vegetation along the Sacramento River—California's largest river—has been almost entirely lost, and several wildlife species have been extirpated or have declined as a result. Large-scale restoration efforts are focusing on revegetating the land with native plants. To evaluate restoration success, we conducted surveys of landbirds on revegetated and remnant riparian plots from 1993 to 2003. Our objectives were to estimate population trends of landbirds, compare abundance patterns over time between revegetated and remnant riparian forests, and evaluate abundance in relation to restoration age. Of the 20 species examined, 11 were increasing, 1 was decreasing (Lazuli Bunting [ Passerina amoena ]), and 8 showed no trend. The negative trend for Lazuli Bunting is consistent with information on poor reproductive success and with Breeding Bird Survey results. There was no apparent guild association common to species with increasing trends. Nine species were increasing on revegetated and remnant plots, four were increasing on revegetated plots only, three were increasing on remnant plots only, the Lazuli Bunting was decreasing on both, and three species were stable on both. Although many species were increasing at a faster rate on revegetated plots, their abundance did not reach that of the remnant plots. For revegetated plots, "year since planting" was a strong predictor of abundance trends for 13 species: positive for 12, negative for 1. Our study shows that restoration activities along the Sacramento River are successfully providing habitat for a diverse community of landbirds and that results from bird monitoring provide a meaningful way to evaluate restoration success.  相似文献   

9.
采用典型样地法,以金马河流域温江段河岸带草本植物为研究对象,经实地踏查,根据采沙运沙干扰程度及样地具体使用情况,将样地划分为河滩地(未受采沙行为干扰,但后期受人类其他活动影响较大)、砾石地(采沙后经河水水位变化形成)、芦苇地[经运沙的车辆碾压形成,后长满芦苇(Phragmites australis)]、斑茅地[采沙后不再受水位影响的高地部分,后长满斑茅(Saccharum arundinaceum)]、沙坑(采沙后直接形成)5个生境类型,以探究不同生境对河岸带草本植物物种多样性和构件生物量的影响。结果表明:(1)在5个生境类型样地中共记录草本植物113种,隶属32科80属,其中沙坑生境草本植物物种数最多,共计59种,隶属21科46属,物种丰富度高,菊科(Compositae)、禾本科(Gramineae)植物在各样地中均较多。(2)斑茅地、芦苇地物种多样性指数较小,优势度指数较大,均匀度指数较小,群落物种分布极不均匀,集中度与均匀度较差,群落存在极大的不稳定性。(3)河滩地植物构件生物总量最少,斑茅地最多且根、茎干重与其他生境存在显著差异。(4)与其它生境类型相比,沙坑物种多样性丰富,分布均匀,构件生物量较多,其环境有利于河岸带植物生长。  相似文献   

10.
The western distinct population segment of yellow-billed cuckoo (Coccyzus americanus; western cuckoo) has been extirpated from most of its former breeding range in the United States because of widespread loss and degradation of riparian cottonwood (Populus spp.)-willow (Salix spp.) forests. Restoration and management of breeding habitat is important to the recovery of this federally threatened species, and identification of high-quality breeding habitat can help improve the success of recovery. In 2005, the Lower Colorado River Multi-Species Conservation Program, a long-term, multi-agency effort, was initiated to maintain and create wildlife habitat within the historical floodplain of the lower Colorado River (LCR) for federally endangered and threatened species, including western cuckoos. We conducted an empirical, multi-scale field investigation from 2008–2012 to identify habitat characteristics selected by nesting western cuckoos along the LCR. Multiple logistic regression models revealed that western cuckoos selected nest sites characterized by increased densities of small, native, early successional trees measuring 8–23 cm diameter at breast height, and lower diurnal temperature compared to available habitat in restoration and natural forests. Nesting cuckoos selected sites with increased percent canopy closure, which was also important for nest success in restoration sites along the LCR. Our results show habitat components selected by nesting western cuckoos in restoration and natural riparian forests and can help guide the creation, enhancement, and management of riparian forests with habitat conditions necessary to promote nesting of western cuckoos. © 2021 The Wildlife Society.  相似文献   

11.
Spatial heterogeneity in the plant species composition of tropical forests is expected to influence animal species abundance and composition because vegetation constitutes the primary habitat feature for forest animals. Floristic variation is tied to variation in soils, so edaphic properties should ultimately influence animal species composition as well. The study of covariation in floristic and faunistic turnover has been hindered by the difficulty of completing coordinated surveys in hyperdiverse tropical communities, but this can be overcome with the use of a few plant taxa that function as surrogates for general floristic turnover. We used avian and plant transect surveys and soil sampling in a western Amazonian upland (terra firme) forest landscape to test whether spatial variation in bird community composition is associated with floristic turnover and corresponding edaphic gradients. Partial Mantel tests and Non‐metric Multidimensional Scaling showed floristic distinctiveness between two forest types closely associated with differences in soil cation concentrations, and differences in both floristic composition and cation concentrations were further linked to compositional differences in avian species, independent of geographic distances among sites. Ten percent of bird species included in Indicator Species Analyses showed significant associations with one of the two forest types. The upland forest types that we sampled, each corresponding to a different geological formation, are intermediate relative to edaphically extreme environments in the region. Models of avian diversification should take into account this environmental heterogeneity, as should conservation planning approaches that aim to represent faunal diversity. Abstract in Spanish is available in the online version of this article.  相似文献   

12.
Although hydraulic redistribution of soil water (HR) by roots is a widespread phenomenon, the processes governing spatial and temporal patterns of HR are not well understood. We incorporated soil/plant biophysical properties into a simple model based on Darcy's law to predict seasonal trajectories of HR. We investigated the spatial and temporal variability of HR across multiple years in two old-growth coniferous forest ecosystems with contrasting species and moisture regimes by measurement of soil water content (theta) and water potential (Psi) throughout the upper soil profile, root distribution and conductivity, and relevant climate variables. Large HR variability within sites (0-0.5 mm d(-1)) was attributed to spatial patterns of roots, soil moisture and depletion. HR accounted for 3-9% of estimated total site water depletion seasonally, peaking at 0.16 mm d(-1) (ponderosa pine; Pinus ponderosa) or 0.30 mm d(-1) (Douglas-fir; Pseudotsuga menziesii), then declining as modeled pathway conductance dropped with increasing root cavitation. While HR can vary tremendously within a site, among years and among ecosystems, this variability can be explained by natural variability in Psi gradients and seasonal courses of root conductivity.  相似文献   

13.
选择合适的物种多样性测度指标与多样性指数是进行群落多样性研究的基础工作。依据塔里木河上游荒漠河岸林样地调查资料,分别采用重要值、盖度和多度为测度指标比较了反映群落物种丰富度、多样性、均匀度和优势度12种多样性指数与异质生境群落多样性特征,并对多样性指数进行了相关分析与评价。结果表明,荒漠河岸林异质生境群落物种组成种类差异明显,轮南镇胡杨群落物种丰富度与多样性指数最高,水工三连灰胡杨群落多样性最低,土壤水盐的空间异质性是引起荒漠植被空间分布与群落多样性差异的主导因子。表征荒漠群落多样性以重要值和盖度为测度指标优于多度指标,其中以重要值为测度指标来反映群落多样性更为合理。相关与主成分分析表明,均匀度与多样性指数间的相关性高于丰富度与多样性指数,且多样性指数受均匀度、优势度指数受丰富度影响较大,反映出荒漠河岸林群落多样性主要决定于物种分布的均匀程度。12种多样性指数中Margalef丰富度指数(Ma)、Shannon-Weiner多样性指数(H)与Simpson多样性指数(D)能客观真实地反映异质生境荒漠植物群落多样性。同时,针对高度生境异质性的荒漠植物群落,还应综合考虑群落物种组成与生境特征,选择合适的多样性指数组合可更客观地反映荒漠河岸林群落多样性变化。  相似文献   

14.
于塔里木河中游地区选取30个样地,并采集相应地区30眼地下水位监测井的数据。根据监测井的地下水位检测数据,将地下水位按不同埋藏深度划分为0~2 m、2~4 m、4~6 m、6~8 m、8~10 m、>10 m共6个梯度,对不同地下水埋深下的样地群落盖度、物种多样性进行分析,以探讨主要植物分布频率与地下水埋深的关系,明确塔里木河中游地区荒漠河岸林植被的合理生态水位,为塔里木河中游地区乃至全流域的生态系统恢复提供依据。结果显示:(1)塔里木河中游地区共出现植物15种,其优势种植物为胡杨。(2)随着地下水位的降低,植被的盖度逐渐减小;当地下水位介于2~4 m时,植被的盖度平均为39.14%,当地下水埋深介于6~8 m时,植被的覆盖度小于20%;当地下水位低于10 m时,植被的平均覆盖度仅为7.65%。(3)随着地下水位的降低,研究区内的各类物种多样性指数均呈先增加后降低的趋势,一般在地下水埋深2~4 m时物种的多样性最高,其次为4~6 m和0~2 m;当地下水位在6 m以下时,物种的多样性锐减,地下水位低于10 m时,物种仅存柽柳和胡杨,多样性降至很小。(4) 塔里木河中游地区植物所要求的地下水平均深度为:胡杨4.58 m、柽柳3.53 m、芦苇2.34 m、骆驼刺4.10 m、花花柴3.18 m、黑刺2.98 m,只有芦苇适宜较浅的地下水埋深(≤2.5 m),其余的均宜在3~4 m左右。研究表明,在塔里木河中游地区,最适宜植物生长的地下水位为2~4 m,能够保证植物正常生长的合理地下水埋深区间为2~6 m。因此,要使塔里木河中游地区的植被得到恢复并确保其正常生长,区域内的地下水位应确保在6 m以上。  相似文献   

15.
Many natural processes in the riparian cottonwood (Populus deltoides) forest of the Middle Rio Grande (MRG) in the southwestern United States have been disrupted or altered, allowing non‐native plants such as saltcedar (Tamarix spp.) and Russian olive (Elaeagnus angustifolia) to establish. We investigated reptilian responses to restoration efforts by sampling communities of lizards at 12 study sites invaded by non‐native plants along the MRG in New Mexico for 7 years (2000–2006). Sites within three regions were randomly assigned to one of the three treatments to remove non‐native plants and woody debris, or as untreated controls. We used pitfall and funnel traps to capture, mark, and release lizards from June to September. Principal components analysis of 15 vegetation variables identified five factors that best explained variation among sites before and after removal of non‐native plants. Relative abundances for four of six common species of lizards were associated with vegetation characteristics that significantly changed after plant removal. Species were either positively associated with the more open, park‐like understory found in treated sites or negatively associated with debris heaps and thickets of non‐native plants found in untreated sites. Eastern fence lizards (Sceloporus consobrinus) and New Mexico whiptails (Aspidoscelis neomexicana) increased in relative abundance after non‐native plants were removed. Overall, removal of non‐native plants seems beneficial, or at least is non‐damaging, to lizard communities of the MRG forest. Providing information on habitat associations of lizard communities will help land managers balance management objectives with other considerations, such as providing important wildlife habitat.  相似文献   

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17.
Abstract: The greatest concentration of Chinese Galliformes occurs in the Trans-Himalayas. We selected 4 northwestern Yunnan counties (Lijiang, Shangri-la, Deqin, and Weixi) in the Trans-Himalayas to assess the conservation status of 9 gallinaceous forest birds. We developed maps depicting recent forest cover and modeled habitat availability of each gallinaceous forest bird based on 3 factors that restrict its distribution: geographic location, elevation range, and forest coverage. The conservation status of 4 species was inadequate, because <10% of their respective potential habitats were within existing nature reserves. To predict the historic habitats of the species we studied, we also delineated a forest map from the late 1950s. We calculated the loss and fragmentation of potential habitats within the past 40 years as degree of habitat degradation. Our results showed that all 9 species became reduced and fragmented of their potential habitats from the late 1950s to 2002. Assessing habitat degradation and conservation status of wild species could help identify the threatened species with poor protection and degraded habitats, thereby warranting more attention in future conservation strategies. To protect those threatened species, it is urgent that the government should design new nature reserves to fill the conservation gaps, and enlarge and strengthen the management of existing natural reserves to reduce effects of human activities on their habitats.  相似文献   

18.
山西文峪河上游河岸林群落稳定性评价   总被引:7,自引:0,他引:7       下载免费PDF全文
稳定性是植物群落结构与功能的综合特征。该文运用模糊综合评判理论评价了山西文峪河上游13种河岸林群落的稳定性。基于群落整体稳定性和结构稳定性的考虑, 选取乔木层优势树种更新潜力、物种多样性、Godron指数、立地质量和保护程度等5项特征指标, 通过计算各群落5项指标隶属度的平均值来评价群落稳定性。研究结果表明, 多数群落的稳定性隶属度介于0.40-0.60, 属于低山森林演替系列的青杨辽东栎(Populus cathayana + Quercus wutaishanica)混交林和油松白桦(Pinus tabulaeformis + Betula platyphylla)混交林的稳定性居中; 中高山森林演替系列中, 群落稳定性随着演替的进展而增加, 青杨(Populus cathayana)林结构简单, 稳定性最低, 青杄(Picea wilsonii)林接近演替顶极, 稳定性最高; 但并非只有近演替顶极的群落是稳定的, 客观存在的各种林冠干扰和河岸生境的高度异质性也使得白杄杨桦(Picea meyeri + Populus cathayana + Betula platyphylla)混交林、落叶松白杄(Larix principis-rupprechtii + Picea meyeri)混交林和落叶松青杄(Larix principis- rupprechtii + Picea wilsonii)混交林有较高的稳定性。  相似文献   

19.
Abstract: We compared the effects of 3 fuel reduction techniques and a control on breeding birds during 2001-2005 using 50-m point counts. Four experimental units, each >14 ha, were contained within each of 3 replicate blocks at the Green River Game Land, Polk County, North Carolina, USA. Treatments were 1) prescribed burn, 2) mechanical understory reduction (chainsaw-felling of shrubs and small trees), 3) mechanical + burn, and 4) controls. We conducted mechanical treatments in winter 2001-2002 and prescribed burns in spring 2003. Tall shrub cover was substantially reduced in all treatments compared to controls. Tree mortality and canopy openness was highest in the mechanical + burn treatment after burning, likely due to higher fuel loading and hotter burns; tree mortality increased with time. Many bird species did not detectably decrease or increase in response to treatments. Species richness, total bird density, and some species, including indigo buntings (Passerina cyanea) and eastern bluebirds (Sialia sialis), increased in the mechanical + burn treatment after a 1-year to 2-year delay; eastern woodpewees (Contopus virens) increased immediately after treatment. Hooded warblers (Wilsonia citrina), black-and-white warblers (Mniotilta varia), and worm-eating warblers (Helmitheros vermivorus) declined temporarily in some or all treatments, likely in response to understory and (or) leaf litter depth reductions. Densities of most species affected by treatments varied with shrub cover, tree or snag density, or leaf litter depth. High snag availability, open conditions, and a higher density of flying insects in the mechanical + burn treatment likely contributed to increased bird density and species richness. In our study, fuel reduction treatments that left the canopy intact, such as low-intensity prescribed fire or mechanical understory removal, had few detectable effects on breeding birds compared to the mechanical + burn treatment. High-intensity burning with heavy tree-kill, as occurred in our mechanical + burn treatment, can be used as a management tool to increase densities of birds associated with open habitat while retaining many forest and generalist species, but may have short-term adverse effects on some species that are associated with the ground- or shrub-strata for nesting and foraging.  相似文献   

20.
Understory birds are especially vulnerable to habitat fragmentation because of the reduction in habitat quality and bird movement. We study the separate effects of understory, overstory and landscape on four understory birds (tapaculos), in Central Chile, comprising a landscape mosaic of pine (Pinus radiata D. Don) plantations and native Maulino forest fragments. We also determined whether habitats with poor understory could be barrier to tapaculos movements. Abundance was measured using stationary playbacks and habitat barrier through playbacks. Understory structure was the main factor that predicted tapaculos presence and abundance. Two species, the Andean Tapaculo (Scytalopus magellanicus fuscus Gmelin) and the Ochre-flanked Tapaculo (Eugralla paradoxa Kittlitz), were positively associated with dead pine branches and negatively to forest fragment size. Tapaculos were less abundant in mature native forest, but appeared willing to cross between different habitat types. However, the Chestnut-throated Huet-huet (Pteroptochos castaneus Philippi and Landbeck), did not move from forest fragments to pine with poor understory. Overall, tapaculos species varied in their response to fragmentation depending on their habitat selection and movement capacities.  相似文献   

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