基于CiteSpace分析国内树洞研究文献及发展趋势

树洞是一种常见的树木腐朽现象,为了解树洞的研究现状和发展趋势,借助CiteSpace软件,对中国知网、万方、维普三大国内数据库截至2021年7月收录的期刊文献进行分析,并形成可视化图。结果发现:国内树洞研究在1957年进入起步阶段,21世纪后发展速度开始加快,发文量整体呈上升趋势,研究内容集中在树洞修补、树洞养护管理、树洞生物、巢箱设计、树洞周边愈伤木和森林空心树6个方面。同时,在此基础上依据关键词突现图分析发展趋势,结果显示:对树洞的研究在初期以森林生态系统为主,后期逐渐倾向于对树木的保护复壮和生态系统的维护,研究范围逐渐扩大。     

三种人工草地小型土壤节肢动物群落多样性动态及其差异

小型土壤节肢动物是草地生态系统的重要组成部分,不仅对物质循环具有重要的作用,还对草地土壤质量或健康状况起指示作用。为了查明青藏高原地区建植不同单播人工草地对小型土壤节肢动物群落多样性的影响,在川西北红原县境内选取建植期为3和5年的老芒麦、垂穗披碱草和苜蓿3种多年生单播人工草地作为研究样地,并以天然草地为对照样地。2018年7和10月,采集各样地0~15 cm的土样并利用Tullgren法分离小型土壤节肢动物。结果表明:1)小型土壤节肢动物群落结构在不同牧草样地间存在差异,影响群落结构的主要是盖头甲螨属、板蒲螨属和长角毛蚊科等;在建植期为3年时,各样地间的小型土壤节肢动物群落密度、类群数和Shannon多样性指数无显著差异(P>0.05);建植期为5年时,小型土壤节肢动物群落密度、类群数和Shannon多样性指数在天然草地和苜蓿样地中无显著差异(P>0.05),但两者显著高于老芒麦和垂穗披碱草样地(P<0.05);此外,小型土壤节肢动物群落的季节动态在不同样地间也存在差异;2)随着建植年限的增加,小型土壤节肢动物群落的密度、类群数和Shannon多样性指数在老芒麦和垂穗披碱草样地显著降低(P<0.05),在苜蓿样地呈缓慢增加趋势(P>0.05),但均低于天然草地;3)影响小型土壤节肢动物群落组成结构的主要环境因子是土壤速效磷含量以及C/N和N/P;此外,小型土壤节肢动物群落密度与土壤速效钾含量呈显著正相关(P<0.05),类群数及Shannon多样性指数与植物群落盖度呈显著正相关(P<0.05)。研究结果表明,在青藏高原上建植单播人工草地对小型土壤节肢动物群落的影响因牧草种类而异并随建植年限变化。建议对高寒地区建植期达到4年的垂穗披碱草、老芒麦和苜蓿单播人工草地进行改造,以提高小型土壤节肢动物多样性,促进草地生态功能正常发挥。     

The regional distribution of large gliding possums in southern Queensland, Australia. I. The yellow-bellied glider (Petaurus australis)

Generalised linear modelling (logistic regression) was used to predict habitat suitability for the yellow-bellied glider (Petaurus australis) from data collected from 620 sites throughout southern Queensland, Australia. Of 42 potential explanatory biotic and abiotic variables, 12 were selected in the final model including an index describing bark characteristics of the overstorey, five climatic variables, three topographic/lithological variables, two landscape metrics and one survey covariate. The predictive capacity of the final model was evaluated using Receiver Operating Characteristic curves and an independent validation dataset (ROC = 0.75; n = 180). Of the extant forest and woodlands of the southern Queensland study region, the interpolated model predicted that approximately 19% was yellow-bellied glider habitat. The majority of predicted habitat occurred within public-owned forests, which are managed under a set of prescribed standards in a Code of Practice for commercial forest management. An important issue for conservation management of the yellow-bellied glider will be management of habitat on privately owned land, which incorporates over 27% of potential glider habitat.     

A comparison of microarthropod assemblages with emphasis on oribatid mites in canopy suspended soils and forest floors associated with ancient western redcedar trees

Microarthropod abundance, oribatid mite species richness and community composition were assessed in the high canopy (ca. 35 m) of an ancient temperate rainforest and compared with microarthropod communities of the forest floor. Microarthropods were extracted from 72 core samples of suspended soils and 72 core samples from forest floors associated with six western redcedar trees in the Walbran Valley on the southwest coast of Vancouver Island, Canada. Total microarthropod abundances, mesostigmatid and astigmatid mites, Collembola and other microarthropod abundances were significantly greater in forest floors compared to canopy habitats. Oribatid and prostigmatid mite abundance were not significantly different between habitats. The relative abundances of all microarthropod groups considered in this study differed significantly between habitats. Eighty-eight species of oribatid mites were identified from the study area. Eighteen of the 53 species observed in suspended soils were unique to the canopy. Cluster analysis indicates that the arboreal oribatid mite community is distinct and not a taxonomic subset of the forest floor assemblage, however, canopy oribatid mite communities are more heterogeneous in species composition than in the forest floor.     

Are nest boxes a viable alternative source of cavities for hollow-dependent animals? Long-term monitoring of nest box occupancy, pest use and attrition

Nest box programs have often been established to conserve hollow-dependent fauna but their effectiveness is unknown in many jurisdictions. We examined nest box effectiveness in a 10-year experimental study in the Mountain Ash (Eucalyptus regnans) forests of Victoria (south-eastern Australia) where the paucity of hollow-bearing trees is a significant conservation issue. We quantified occupancy by arboreal marsupials, infestation by pest invertebrates, and nest box attrition. We found a large proportion of nest boxes (68.8%) were never used, including by the endangered target species, Leadbeater’s Possum (Gymnobelideus leadbeateri). Nest boxes were more often occupied in younger forests (58.3% cf 4.1% for old forest) but these sites were also where infestations by the introduced European Honeybee (Apis mellifera) were greatest and where the probability of nest boxes collapsing was highest. Our data suggest that it is important to carefully target the locations where nest boxes should be established, but these same places are also those where most effort is required to maintain them, either by removing pest invertebrates and/or by re-attaching them to trees after they have fallen down.We recorded reasonable levels of occupancy by arboreal marsupials in young forest ∼2-3 years after box establishment, but then high levels of nest box attrition (>51%) occurred after 8-10 years. This suggests an “effective occupancy time” for arboreal marsupials of only ∼5 years.A key consideration must be to weigh the ecological and economic effectiveness of nest boxes against other strategies such as implementing alternative silvicultural systems that result in the creation and retention of more hollow-bearing trees within logged areas.     

Time lags in provision of habitat resources through revegetation

Broadscale land use changes are occurring rapidly in rural landscapes worldwide, within which revegetation with native plant species to increase the area of suitable habitat is a key activity. Current models for planning revegetation are based solely on the spatial arrangement of new and remnant vegetation. Making wise decisions about revegetation requires projective models of ecological responses to revegetation, but there are few appropriate data. Substantial time lags are expected in the availability of many habitat resources because different resources are realised at different stages of vegetation maturation. Here we present results of surveys of 72 revegetation sites established over a range from 5 to more than 130 yr from the slopes and plains of central Victoria, Australia. We surveyed vegetation provision of habitat resources essential for many birds and arboreal and scansorial mammals (e.g. canopy, large boughs, tree hollows and fallen timber). Predictive models were developed for habitat resource provision as functions of time since planting, planting density and other covariates. Different habitat resources developed at different rates. While dense canopy and various forms of bark resources developed in about 10 yr, large boughs, tree hollows and fallen timber loads required at least 100 yr to develop. The development of these key habitat resources was delayed in revegetated sites with high stem densities. Habitat resources that are essential for many birds and arboreal and scansorial mammals have long time lags that models for planning offsets or landscape reconstruction should account for. Management has substantial effects: planting at high densities greatly reduces tree girth growth rates and delays the occurrence of large boughs, tree hollows and fallen timber by decades.     

Influence of contrasting urban edges on the abundance of arboreal mammals: A study of squirrel gliders (Petaurus norfolcensis) in southeast Queensland, Australia

The primary impacts of urban development on biodiversity are loss and fragmentation of habitat, and changes in the structure, composition and function of remnant native ecosystems. Forest dependent species, including arboreal mammals, are particularly sensitive to these changes due to their highly specific habitat requirements and inability or reluctance to cross the urban matrix. We addressed this problem using a case study of the squirrel glider (Petaurus norfolcensis) in fragmented urban landscapes of southeast Queensland, Australia. We applied a mixed effect modeling approach clustered by patch to quantify the importance of site-level habitat factors relative to edge contrast and habitat patch size on squirrel glider abundance. Analysis of variance was used to test for differences in glider age and sex in interior habitats compared to road and residential edges. We found that edge contrast had a strong negative effect on the abundance of squirrel gliders but is conditional on the presence of a low numbers of unreliable flowering overstorey trees and the availability of critical resources such as nest hollows at a site. We also found that older male gliders prefer forest fragment interiors over road and residential edge habitats. We conclude that although interior habitats are ideal to maintain large stable populations, the conservation value of low contrast edges containing key site-level resources should not be underestimated for arboreal mammals such as the squirrel glider.     

Spatiotemporal distribution of aboveground litter in a Cryptomeria japonica plantation

We assessed the vertical distribution of litter and its seasonal patterns in the canopy and on the forest floor (soil), as well as litterfall (the flux of litter from the canopy to the soil) in a 33-year-old plantation of Japanese cedar (Cryptomeria japonica D. Don). The masses of total litter, dead leaves, and dead branches in the canopy of C. japonica trees averaged 34.09, 19.53, and 14.56 t dry wt ha⁻¹, respectively, and were almost constant during the study period. The total masses of the annual litterfall were 4.17 and 5.88 t dry wt ha⁻¹ year⁻¹ in the two consecutive years of the study. The mass of the soil litter averaged 7.95 t dry wt ha⁻¹ during the same period. All relationships between the mass of canopy litter and tree-size parameters (diameters at breast height and at the lowest living branch) were linear in a log-linear regression. Compared with the results for this plantation at a younger stage (16 years old), our results suggest that the total mass of dead leaves attached to each tree increases markedly with increasing age, but that the trajectory of this increase as a function of tree size may change from an exponential to a saturation curve with increasing stand age.     

Impacts of silvicultural treatments on arboreal lichen biomass in balsam fir stands on Québec's Gaspé Peninsula: Implications for a relict caribou herd

We investigated immediate, medium and long-term effects of logging on arboreal lichen biomass in old-growth balsam fir forests (Abiesbalsamea (L.) Mill.) in the highlands of Québec's Gaspé Peninsula using three complementary approaches. Firstly, we estimated the immediate loss of lichen biomass following logging and the annual lichen litterfall from remnant trees over 2 post-logging years. Treatments included selection cutting at three intensities (25, 30, 35%), diameter-limit cutting and cutting with protection of regeneration and soils (CPRS). Among studied treatments, we found that CPRS and diameter-limit cutting removed almost all the standing lichen biomass, while selection and partial cut allowed an immediate retention of ∼40–60% of the initial lichen biomass. Our results also suggested that the impact of logging on lichen litterfall rates were higher in silvicultural treatments (3–8.5%) compared to controls (1–2%); litterfall rates did not differ after 1 or 2 years post-treatment. Secondly, we evaluated medium-term effects by comparing pre-harvest fruticose lichen biomass data with data collected at the same site 4 years after experimental thinning operations. Mean fruticose lichen biomass did not change 4 years post-harvest. However, Bryoria spp. biomass did increase relative to Alectoriasarmentosa while Usnea spp. remained unchanged. Finally, the long-term logging effects were assessed by evaluating fruticose lichen biomass along a forest chronosequence in stands aged 30, 50, 70 and 90 years. Lichen biomass increased as a function of time for all genera, especially Alectoria. Logging activities result in direct losses of lichen biomass, but careful selection cutting that retains large lichen bearing trees and maintains post-harvest conditions not detrimental to lichen growth, particularly for Bryoria spp., can ensure a substantial biomass of lichens post-harvest. Such measures may ultimately contribute to maintaining woodland caribou herds that rely on arboreal lichens.