Dispersal ecology of the endangered woodland lichen Lobaria pulmonaria in managed hemiboreal forest landscape

Changes in the forest management practices have strongly influenced the distribution of species inhabiting old-growth forests. The epiphytic woodland lichen Lobaria pulmonaria is frequently used as a model species to study the factors affecting the population biology of lichens. We sampled 252 L. pulmonaria individuals from 12 populations representing three woodland types differing in their ecological continuity and management intensity in Estonia. We used eight mycobiont-specific microsatellite loci to quantify genetic diversity among the populations. We calculated the Sørensen distance to estimate genetic dissimilarity among individuals within populations. We revealed that L. pulmonaria populations have significantly higher genetic diversity in old-growth forests than in managed forests and wooded meadows. We detected a significant woodland-type-specific pattern of genetic dissimilarity among neighbouring L. pulmonaria individuals, which suggests that in wooded meadows and managed forests dominating is vegetative reproduction. The vegetative dispersal distance between the host trees of L. pulmonaria was found to be only 15–30 m. Genetic dissimilarity among individuals was also dependent on tree species and trunk diameter. Lobaria pulmonaria populations in managed forests included less juveniles compared to old-growth forests and wooded meadows, indicating that forest management influences life stage structure within populations. We conclude that as intensive stand management reduces the genetic diversity of threatened species in woodland habitats, particular attention should be paid to the preservation of remnant populations in old-growth habitats. Within managed habitats, conservation management should target on maintenance of the stand’s structural diversity and availability of potential host trees.     

EVALUATING THE IMPACT OF INSECT COMMUNITY ON PINE CATERPILLAR DENSITY IN DIFFERENT STAND CONDITIONS

Abstract  Natural enemies play an important role in inhibiting population growth of pine caterpillar, but they are difficult to be used in systematic management models. This paper attempts to use some forest stand factors to substitute the effect of natural enemies, which could be used in management models. Through the studies from more than 200 stand plots with different stand conditions in Qu County, Changshan County, and Longyou County of Zhejiang Province, 16 predominant species groups from insect community were selected, and the canonical correlation coefficient between the diversity index, species number, individual number of predominant species and the stand factors was analyzed. The results indicated that the canopy density and ground vegetation were the key stand factors for characterizing the function of insect community. The forest area was divided into four types according to the variation of canopy and vegetation conditions by using cluster analysis. The regression models between the rate of variation of pine caterpillar density and the forest factors including canopy density and vegetation covers were developed in each type of forests. There were significant differences in diversity index, species number, individual number of insect community and population density of pine caterpillar among four types of forests, and correlation coefficients of the four regression models were rather high ( r =0. 924 — 0. 964). This means that the classification of the forest stands is reasonable and the stand factors can characterize the effect of natural enemies in practice.     

The lichen flora on Picea abies in a suboceanic spruce forest area in Central Norway with emphasis on the relationship to site and stand parameters

The lichen flora on 400 Picea abies trees (branches, trunks and trunk bases) in 100 patches of suboceanic spruce forest in Central Norway has been investigated. Relationships between occurrence of the species and a number of habitat and tree variables were analysed by detrended correspondence analysis (DCA). A total of 122 lichen species were recorded. Total species number was found to be about the same on branches and trunk bases (considerably lower on trunks), but with higher β-diversity on trunk bases. Most species could be classified as branch specialists, generalists, trunk or trunk base specialists. Among the measured habitat variables, stand age, altitude and vegetation type were found to be the most important for explaining the patterns of species distributions. Alectoria sarmentosa, Mycoblastus sanguinarius and several dry bark species on trunks, including Caliciales species, were more or less confined to old forests, while Usnea spp. were more abundant in young form. Trentepohlia-containing trunk base species like Arthonia vinosa, Dimerella pineti, Lecanactis abietina and Sclerophora coniophaea showed preference for vegetation types indicating nutrient-rich substrates. The number of branch species was highest on lower altitudes while the opposite was true for trunk species. Larger trees with rough bark in older stands had a more species-rich lichen flora, probably because of higher substratum area and availability of more diverse microsites.     

Plant diversity patterns in subtropical evergreen broad-leaved forests of Yunnan and Taiwan

The subtropical evergreen broad-leaved forests of Yunnan and Taiwan were compared along environmental and successional gradients with the aim of identifying important taxon and species diversity as well as the drivers of mountain biodiversity patterns. A detrended correspondence analysis of an exhaustive set of data collected from 105 and 223 plots for Yunnan and Taiwan, respectively, was applied to classify natural mature forest types. Additional data from 72 and 68 plots for Yunnan and Taiwan, respectively, were used for analyses of secondary succession. The floristic richness and diversity index were calculated for each type of forest. In Yunnan, the monsoon forests in mesic-humid sites had more taxa and tended to show higher species diversity than the other two forest types. In Taiwan, species diversity values were significantly higher in the Machilus–Castanopsis zone in the middle altitudes (500–1500 m) than for the other three forest zones. For both Yunnan and Taiwan, the forests at the middle successional stage showed significantly higher species diversity than those at the early successional stage. Differences in diversity between the middle and late stages were not significant. These findings highlight the high species diversity of the natural mature evergreen broad-leaved forests of both Yunnan and Taiwan. In the secondary forests, as succession proceeds, species diversity comes to resemble that of the natural mature forests. In both ecosystems, the drivers of species diversity patterns are moisture, altitude, and succession/disturbance.     

Secondary succession and effects of clear-logging on diversity in the subtropical forests on Okinawa Island,southern Japan

In order to clarify the recovery process of the subtropical forest on Okinawa Island, southern Japan, biomass accumulation and the successional trend of species diversity with time were investigated by comparing plots of old-growth and clear logged secondary forests. Self-thinning was an important factor in the development of young secondary forests, and the small variance in tree size within a stand was related to the stand not being fully stratified after clear-cutting. A large variance of size structure in old secondary and old-growth forests implies re-initiation of the understorey. Additionally, the trajectory of stand development indicated that the subtropical forest quickly recovered aboveground biomass, which reached its upper limit at about 50 years after disturbance. However, there was a large distinction in species diversity between the secondary forests and old-growth forests. The diversity of forest floor plants did not recover well after being clear-cut. This indicates that management of the subtropical forest should not only take timber-oriented tree species into account, but also the biodiversity in ground flora. The secondary forests were characterized by Castanopsis sieboldii and Schima wallichii, and the monopolization of C. sieboldii through secondary succession had a negative influence on species diversity. Distylium racemosum dominated at the late development stage and was considered a long-lived competing species that reduced the dominance of C. sieboldii and facilitated the co-occurrence of understorey species. Light-demanding pioneer tree species such as S. wallichii that regenerated after logging should be replaced by competitive effects of climax species, and thus relayed floristic change might increase species diversity along secondary succession.Nomenclature: Hatushima and Amano (1994).     

EPIPHYTE FLORA AND DIVERSITY ON BASAL TRUNKS OF SIX OLD-GROWTH FOREST TREE SPECIES IN SOUTHERN AND MIDDLE BOREAL FINLAND

Epiphytic lichen and bryophyte species composition, richness and diversity were surveyed on basal trunks of six common old-growth forest tree species,Picea abies,Pinus sylvestris,Betula pendula,Alnus incana,Salix capreaandPopulus tremula, in two old-growth forest areas, one in southern and one in middle boreal Finland. The average species numbers per tree ranged from 18 (Picea) to 27 (Salix) in the southern and from 20 (Populus) to 31 (Salix) in the middle boreal area. A few widespread habitat-generalist species, such as the foliose lichensHypogymnia physodesandPlatismatia glauca, were most abundant on all the tree species, exceptPopulus. Most other epiphyte species showed at least a slight preference for one or two tree species.Populusproved to have the most distinct flora characterized by the abundance of certain, rather specialized crustose lichens and bryophytes. The number of species that occurred on only one tree species was highest onPopulus(9) in the southern and onAlnus(18) in the middle boreal area. Differences in bark acidity and structure were the most likely explanations for the differences between tree species in the epiphytic flora and diversity.SalixandPopuluswere the most important of the tree species studied for the conservation of epiphyte diversity in the boreal forests of Finland.     

Macrolichen diversity as an indicator of stand age and ecosystem resilience along a precipitation gradient in humid forests of inland British Columbia,Canada

The distributional ecology of 87 macrolichens is reported from 14 unmanaged mid-seral and old forest stands along a precipitation gradient in south-central British Columbia. We used a combination of univariate and multivariate statistics to investigate the role of forest structure and stand age in the distribution of epiphytic macrolichens in interior cedar-hemlock forests. Old forests support a higher number of species; although mean species richness is not significantly different between the two age classes. Terricolous and epixylic community structure is correlated with stand age and log characteristics, but the epiphtytic community is not. Epiphytic community structure is strongly associated with precipitation in the old stands, but not in the mid-seral stands. Old forests at the wetter end of the precipitation gradient contained several old-growth associated species, all of which are hygrophytic. Most epiphytic macrolichens associated with old forests are not dependent on specific structural attributes. However, western red cedar (Thuja plicata Donn ex D. Don) harbors the greatest number of arboreal macrolichen species by far in these unmanaged stands and should, therefore, be considered a key indicator in managed forests. Our study suggests that most macrolichen species found in old forests can also occur in 70- to 165-year-old forests dating from stand-replacing fires. Old forests, however, clearly provide important habitat for oceanic epiphytes at the edge of their ecological range in the interior of British Columbia. Our findings illustrate that the macrolichen flora in wet toe-slope stands in humid inland British Columbia has a high level of resilience following disturbance under natural succession conditions. It also underlines the point that some species, like Lobaria pulmonaria, are good indicators of old-growth forests in certain regions but not in others, suggesting a careful use of the term old-growth dependence.     

Tree and stand-scale factors affecting richness and composition of epiphytic bryophytes and lichens in deciduous woodland key habitats

Conservation and sustainable forestry are essential in a multi-functional landscape. In this respect, ecological studies on epiphytes are needed to determine abiotic and biotic factors associated with high diversity. The aim of the present study was to evaluate relative sensitivity of conservation targets (epiphytic bryophytes and lichens) in relation to contrasting environmental variables (tree species, tree diameter at breast height, bark crevice depth, pH, tree inclination, pH, forest stand age, area and type) in boreo-nemoral forests. The study was conducted in Latvian 34 woodland key habitat (WKH) boreo-nemoral forest stands. Generalized linear mixed models and canonical correspondence analysis showed that tree species and tree bark pH were the most important variables explaining epiphytic bryophyte and lichen composition and richness (total, Red-listed, WKH indicator species). Forest stand level factors, such as stand size and habitat type, had only minor influence on epiphytic species composition and richness. The results of the present study indicate a need to maintain the diversity of tree species and large trees, particularly Acer platanoides, Carpinus betulus, Fraxinus excelsior, Populus tremula, Tilia cordata, Ulmus glabra and Ulmus laevis in conservation of epiphytic bryophyte and lichen communities in the future.     

天山森林生态系统树生地衣植物群落数量分类及其物种多样性的研究

地衣是由低等植物中的藻类与菌类中的真菌和兰细菌共生而成的一群特殊的植物。由于耐寒耐旱对生活中的养分要求不高,在养纷贫瘠、环境恶劣的高山寒漠、平原、戈壁和沙漠中地衣都能生长,因而广泛地分布和生长在不同的生态环境中。有关新疆地衣方面的研究报道集中在物种分类水平上,对于地衣群落结构方面的研究比较少。因此,我们应用多元分析中的主分量分析及聚类分析方法对分布在天山森林生态系统中树生地衣植物群落进行数量分类并对群落结构物种多样性、相似性和均匀度等群落参数进行了比较系统的研究。结果表明, 在西部天山不同森林生态系统中树生地衣群落的分布与海拔高度和树种有密切的关系, 不同海拔的不同类型的森林生态系统中分布着不同种类的树生地衣植物。 根据多元分析结果和生境的综合特征,该地区的树生地衣可划分为4种类型: 1) 茎口果粉衣+金黄茶衣群丛Chaenotheca stemonea+Candellaria aurella Association; 2)叉小孢衣+裸扁枝衣+粉唇蜈蚣衣群丛Bryoria furcellata+Evernia esorediosa+Physcia tribacoides Association; 3)亚广开梅衣+槽梅衣+疑小梅衣群丛Parmelia fertilis+Parmelia sulcata+Parmeliopsis ambigua Association; 4)睫毛黑蜈蚣衣+黑蜈蚣衣群丛Phaeophyscia ciliata+Phaeophyscia nigricans Association。其群落多样性指数以亚广开梅衣+槽梅衣+疑小梅衣群丛为最高 (1.920), 叉小孢衣+裸扁枝衣+粉唇蜈蚣衣群丛为最低 (1.562)。     

Predictability of plant and fungal species richness of old‐growth boreal forest islands

Abstract. The fragmentation and deterioration of old‐growth forest habitat by modern forestry have become a major threat to species diversity in Fennoscandia. In order to develop a conservation strategy for the remaining diversity it is essential to identify the existing diversity and to develop appropriate conservation and monitoring programs. For these purposes indicators of conservation value for administrative prioritization are required. This study examines the predictability of plant and fungal species richness on two spatial scales on 46 isolated old‐growth forest islands (0.17 ‐ 12 ha) in a forest‐wetland mosaic. We explore (1) to what extent area, isolation and stand structure variables can explain the variation in species richness and (2) if richness patterns of individual species groups correlate. Isolation showed no relation to species richness. Area explained 50 ‐ 70% of the variation in total species richness and was positively related to the density of crustose lichens and Red‐list species in island interiors. Stand structure variables explained 28 ‐ 66% of the residual variation in total species richness after controlling for island size, and 15 ‐ 73% of the variation in density of species in island interiors. The highest predictability of species richness was found among substrate‐specific fungi and Red‐list species. Different stand structure variables were found to explain richness in the different species groups, and only among a few species groups species richness correlated. Thus, species richness of one single species group is unlikely to be a good indicator for total biodiversity. The results show that measurements of stand size and stand structure variables may be a strong complementary tool, and sometimes a substitute to extensive species inventories when one aims to estimate and monitor plant and fungal species diversity in old‐growth Picea abies forests.     

Avian richness and abundance in temperate Danish forests: tree variables important to birds and their conservation

Many studies on avian diversity and forest structure have focused onfiner scale forest variables such as foliage height diversity, foliagediversity, foliage density, vertical distribution of vegetation and horizontalvegetation density. From a conservation and forestry operational point of viewit would be of great interest if tree variables influenced directly by forestrymanagement decisions also had significant influence on avian richness andabundance. The species, age and size of a tree are examples of such treevariables. A great number of studies also have focused on avian diversityindices to reveal relationships with vegetation variables. However, it may bemore appropriate for foresters and conservation officers to operate withrichness and abundance measures directly, because indices complicateinterpretations on the relative importance of the two variables (richness andabundance) constituting the index. Fourteen managed temperate forests in Denmarkwere investigated for avian species richness and abundance and related tomeasures on different tree variables influenced directly by forestry managementdecisions. A rapid assessment method of avian richness and abundance wasemployed. It consisted of point-counts of bird richness and abundance within 1km² of forest. General linear models were tested byanalyses of variance statistics to reveal the tree variables most important toavian richness and abundance. It was found that more old trees, more treespecies and more tree size-classes correlated with more bird species andindividuals. However, some variation in bird richness and abundance was alsorelated to site quality and/or chance colonization. Moreover, it was shown thatthe guild of cavity-nesting birds correlated positively to age of tree stand.The potential number of bird species in Danish forest is similar to that innearly pristine forest in Poland, and much larger than that recorded in any ofthe forests investigated. Together with the results above, this indicates a highpotential for squeezing in more avian species in a higher quality forest from abiodiversity point of view. Modern Danish forestry affects tree variablesinfluenced directly by forestry management decisions. Such tree variables havegreat influence on avian richness and abundance, but simple measures in forestrypractices can be taken to enhance the conservation of bird richness andabundance.     

澜沧江下游/湄公河上游片断热带雨林物种多样性动态

 在澜沧江下游/湄公河上游的滇南西双版纳地区,通过样方法比较了热带雨林的连片与3个小片断的物种多样性变化趋势。与连续森林比较,片断热带雨林的植物物种丰富度和物种多样性指数都比较低,而且有相当低比例的大高位芽、中高位芽和附生等生活型植物,而藤本、小高位芽和矮高位芽等生活型植物的比例则较高;泛热带、热带亚洲至热带非洲的区系成分比例较高,而当地成分则减少;群落的上层树木比下层树木更加稳定。同样,动物的物种多样性指数和均衡度在片断热带雨林中都较低,与其密切相关的是片断热带雨林的环境质量,而不是片断的大小。此外,也探讨了片断热带雨林物种变化与森林小气候的关系,阐明了由凉湿向干暖转化的“林内效应”是其物种变化的重要原因之一。     

不同立地条件下昆虫群落对松毛虫密度影响的估计(英文)

天敌在松毛虫种群动态中起重要作用,但把天敌的作用加入系统管理模型中却很困难。本文试图用林分因子代替天敌的作用,因为林分条件可以方便地用于系统模型中。通过对浙江省衢县、常山县和龙游县不同立地条件的222块样地的调查数据的分析,从70多科的昆虫群落中选择了16个关键种（科）,并对林分因子和各样地关键种的种数、个体数、多样性之间的关系进行了典型相关分析。结果表明郁闭度和植被条件（灌木层盖度、灌木层高度、草木层盖度、草木层高度、总盖度）是刻划昆虫群落功能的关键林分因子。根据郁闭度的变化和植被条件用系统聚类方法可以把林区分为四种类型,这四种类型林地的昆虫多样性指数、种数、个体数量和松毛虫的密度都存在明显差异;在每种林地都建立了松毛虫密度的变化率与关键林分因子间的回归模型,所有的回归的相关系数都相当高（0．924－0．964）,因此可以认为对林地的分类是合理的,而且用林分因子评估天敌的影响在实践中是可行的。     

Hypocrealean (Hypocreales,Ascomycota) Fungal Diversity in Different Stages of Tropical Forest Succession in Costa Rica1

The relationship between forest succession and microfungal diversity has been poorly studied. Fungi provide important ecosystem services that may deteriorate in deforested or highly disturbed forests. To determine the possible effects of deforestation and forest succession on microfungi, species diversity of hypocrealean fungi (Ascomycota) was compared in forest stands in Eastern Costa Rica representing three stages of succession: 1–2, 25–27 yr old, and an old growth forest. Species diversity in a second‐growth forest fragment surrounded by timber plantations and second‐growth forest was also compared to that of a stand surrounded by old growth forest. The results show that the overall diversity of hypocrealean fungi was inversely proportional to the age of the forest stand, and each family showed different successional trends. Clavicipitaceae was more diverse in the old‐growth forest and was positively related to the age of the forest stand. Nectriaceae was highly diverse in the 1‐ to 2‐yr‐old stand and less diverse in the old‐growth stand. Saprobic and plant pathogenic fungal species were more diverse in the 1‐ to 2‐yr‐old stand and their diversity was inversely proportional to the age of the forest stand. The diversity of insect pathogens was positively related to the age of the forest stand. The 20‐ to 22‐yr‐old forest fragment had the lowest number of species overall. Based on the data gathered in this study, hypocrealean fungal species diversity is related to the successional stage and fragmentation of tropical forest.     

宝天曼地区栓皮栎林恢复过程中高等植物物种多样性变化

对宝天曼地区不同恢复阶段栓皮栎林的高等植物物种多样性特征进行了初步分析。结果表明,各层物种丰富度和多样性指数在不同恢复阶段栓皮栎林表现出草本层＞灌木层＞乔木层的趋势。乔木层物种丰富度和多样性指数基本上随恢复时间的增加而增加;灌木层在未破坏的栓皮栎林内较低,而在其他恢复阶段的栓皮栎林内基本相同;草本层在恢复５年、１５年和２５年的栓皮栎林中较高,而在恢复４５年和未破坏的栓皮栎林内较低。乔木层物种均匀度指数在未破坏的栓皮栎林中较高,在恢复２５年的栓皮栎林中较低;灌木层在恢复４５年的栓皮栎林中较高,在恢复１５年的栓皮栎林较低;草本层在恢复５年的栓皮栎林中较高,在恢复１５年的栓皮栎林中较低。不同恢复阶段栓皮栎林各层次间的物种多样性差异大多不显著,只有乔木层和草本层及灌木层和草本层之间的物种丰富度指数有显著差异。不同恢复阶段栓皮栎林在乔木层物种多样性特征上的差异最大,在灌木层物种多样性特征上有一定差异,在草本层物种多样性特征上没有明显的差异。     

Nuovi reperti di intersessualità nelle Cucurbitacee

Abstract

The aim of this paper is to investigate differences in plant species composition between managed and unmanaged forests, and to assess if these difference give rise to a higher plant diversity in the unmanaged forest. Furthermore our aim is to relate forest structure to differences in plant species composition, identifying the structural attributes more strongly related to the unmanaged forest vegetation. We compared an old-growth forest and a managed highforest in the Abruzzo Lazio and Molise National Park (Central Italy). Plant species composition and diversity, deadwood components and live structure have been analyzed. We used permutational multivariate analysis of variance to test the response of species composition to management factor; furthermore, we compared species richness and beta diversity. Redundancy analysis has been used to relate plant species abundances to structural variables; the importance of dead and living wood components has been compared through variation partitioning. Plant species composition proved to be significantly different in the two sites, and the old-growth stand showed a higher plant diversity. From a structural point of view, we found differences especially in the amount and quality of deadwood, and in the diameter class distribution. These variables are also the most important in determining the old-growth stand plant species composition according to redundancy analysis. Variation partitioning confirmed the greater importance of the deadwood variables. Our results suggest that including deadwood surveys in traditional forest inventories could help in finding forests with both structural and floristic old-growth properties to be considered in conservation programmes. The imitation of natural dynamics, through the creation of gaps avoiding deadwood removal, could be an effective strategy for restoring old-growth conditions, also in terms of plant diversity.     

Effects of forest management on epiphytic lichen diversity in Mediterranean forests

Question: What are the responses of epiphytic lichens to the intensity of management along a large environmental gradient in Mediterranean Quercus forests? Location: Central Spain. Methods: This study was carried out on 4590 trees located in 306 forest stands dominated by Quercus faginea or Quercus ilex ssp. ballota. The effect of forest management and other predictor variables on several species diversity indicators were studied. Variables modelled were total species richness, cyanolichen richness and community composition. A large number of predictor variables were included: forest fragmentation (patch size, stand variability), climate and topographic (altitude, slope, sun radiation, annual rainfall and mean annual temperature) and intensity of management. General linear models and constrained ordination techniques were used to model community traits and species composition, respectively. Results: Total richness and especially cyanolichens richness were significantly and negatively affected by the intensity of management. Lichen composition was influenced by management intensity, climatic and topographic variables and stand variability. Conclusions: In Mediterranean forests, human activities related to forestry, agricultural and livestock use cause impoverishment of lichen communities, including the local disappearance of the most demanding species. The conservation of unmanaged forests with a dense canopy is crucial for lichen diversity.     

Chronosequential change in a butterfly community after clear-cutting of deciduous forests in a cool temperate region of central Japan

Transect counts of butterflies were conducted in the northern part of Ibaraki, central Japan, from 1997 to 2001 at 11 census sites, composed of successive stages of deciduous forest development: grassland (one site, early abandoned stage); cutover land (one site, 1–5 years after clear‐cutting); secondary forests (very young (two sites, 6–9 years), middle (two sites, 16–22 years) and old (two sites, 47–51 years)) and old‐growth natural forests (three sites, ≥124 years old). A total of 86 species and 8858 individual butterflies were recorded by 29 sets (406 times) of transect counts. The species richness (number of species), abundance (number of individuals) and diversity indices (Shannon–Wiener H′ and Simpson's 1–λ) of butterflies were high in the early stages (grassland, cutover land and very young secondary forests) of secondary succession. Typical natural forest species increased with the progress of succession, and the old secondary forests and old‐growth natural forests had similar species composition. In contrast, most of the typical natural grassland species were recorded only in the grassland site. In the cutover land site, the number of individuals of grassland species considerably decreased from the first to the second year; furthermore, only one typical natural grassland species was recorded. Thus, the suitable stage for grassland butterfly species lasts for only 1–2 years after clear‐cutting. Old secondary forests (approximately>50 years old) would be able to give refuge to the forest butterfly species, including typical natural forest species. Based on the results, a practical, forestry‐based plan to conserve butterfly diversity was proposed.     

广东黑石顶南亚热带森林幼苗的区系和生态研究（英文）

 本文研究了自然林下和深入林内2km新开公路的斜坡(当作特殊的林窗)的幼苗的种类组成、多样性、分布格局和生长。林下幼苗种丰富度(99种)和Shannon-Wiener多样性指数(5.43)与所在林分立木种的丰富度(117种)和多样性指数(5.42)相当,而比公路斜坡相近面积上幼苗的相应值(59种,多样性指数4.21)高。林下幼苗的乔木种类占的比例(46％)较公路斜坡幼苗的乔木种类的比例(34％)高,而草本种类占的比例(23%)较后者(32％)低。林下幼苗的木本种类和林分立木的S ф rensen相似系数(0.500)较公路斜坡幼苗木本种类和林分的相似系数(0.171)高得多,林下幼苗的种类组成和公路斜坡幼苗的种类组成的相似性很低(S ф rensen 系数(0.247)。两个生境中大多数优势种群都表现为集群分布。公路斜坡上的幼苗种群似乎集群程度更高。先锋树种的幼苗在公路斜坡较瘦瘠的土壤条件下1～5年生幼苗的平均相对生长率为：0.944～1.555g·g-1·a-1,比在林下耐阴树种幼苗的相对生长率(0.765～1.402)高或相当,但生物量积累较后者慢。在森林中,耐阴树种的幼苗未显出休眠的特性。先锋树种的幼苗有较高比例的叶生物量,而演替后期树种的幼苗则有较高比例的生物量分配给根。     

Woody Species Diversity in Forest Plantations in a Mountainous Region of Beijing,China: Effects of Sampling Scale and Species Selection

The role of forest plantations in biodiversity conservation has gained more attention in recent years. However, most work on evaluating the diversity of forest plantations focuses only on one spatial scale; thus, we examined the effects of sampling scale on diversity in forest plantations. We designed a hierarchical sampling strategy to collect data on woody species diversity in planted pine (Pinus tabuliformis Carr.), planted larch (Larix principis-rupprechtii Mayr.), and natural secondary deciduous broadleaf forests in a mountainous region of Beijing, China. Additive diversity partition analysis showed that, compared to natural forests, the planted pine forests had a different woody species diversity partitioning pattern at multi-scales (except the Simpson diversity in the regeneration layer), while the larch plantations did not show multi-scale diversity partitioning patterns that were obviously different from those in the natural secondary broadleaf forest. Compare to the natural secondary broadleaf forests, the effects of planted pine forests on woody species diversity are dependent on the sampling scale and layers selected for analysis. Diversity in the planted larch forest, however, was not significantly different from that in the natural forest for all diversity components at all sampling levels. Our work demonstrated that the species selected for afforestation and the sampling scales selected for data analysis alter the conclusions on the levels of diversity supported by plantations. We suggest that a wide range of scales should be considered in the evaluation of the role of forest plantations on biodiversity conservation.