Spatial hints of forest ecotone indicating forest succession, a case of larch forests in Baihuashan Reserve, north China

In cold or alpine areas of northern China, birch forests and larch forests are the two primary forest types. These forests are also characteristic of a south branch of boreal forests in Asia. Some ecologists argue that larch forests can replace birch forests, but this still remains a question due to fragmentary or short observations. The ecotone between a larch forest patch and a birch forest patch is the arena in which the two species interplay and compete with each other, and studies of these areas are meaningful to understanding forest succession. In the alpine area of the Baihuashan Reserve, northern China, we sampled a larch-birch forest ecotone with eight plots in four transects and then analyzed population structures of larches and birches. The results show that the edges of the larch forest patch are composed of many larch saplings or young trees, but the edges of the birch forest patch are mainly composed of old birches. Across the ecotone, the larches, on average, are taller than the birches. These facts suggest that larch saplings can permeate into birch forest patches, probably by seed dispersal, germination, successful competition and growth, but birch saplings cannot permeate into larch forest patches. Therefore, on the ecotone, larch forest patches can steadily expand by unceasing permeation into birch forest patches, whereas birch forest patches progressively recede due to ultimate death of the old and poor recruitment of the young. Larch forest patches replace birch forest patches in a stepwise manner, causing succession from birch forests to larch forests. This study not only confirms that larch forests can naturally replace birch forests, but also introduces a simple and reliable method, employing spatial hints, to study forest succession. Additionally, the findings are of benefit to cultivation or development of larch forests in cold or alpine areas of the North Temperate Zone, which can be a huge carbon sink.     

Spatial hints of forest ecotone indicating forest succession, a case of larch forests in Baihuashan Reserve, north China

In cold or alpine areas of northern China, birch forests and larch forests are the two primary forest types. These forests are also characteristic of a south branch of boreal forests in Asia. Some ecologists argue that larch forests can replace birch forests, but this still remains a question due to fragmentary or short observations. The ecotone between a larch forest patch and a birch forest patch is the arena in which the two species interplay and compete with each other, and studies of these areas are meaningful to understanding forest succession. In the alpine area of the Baihuashan Reserve, northern China, we sampled a larch-birch forest ecotone with eight plots in four transects and then analyzed population structures of larches and birches. The results show that the edges of the larch forest patch are composed of many larch saplings or young trees, but the edges of the birch forest patch are mainly composed of old birches. Across the ecotone, the larches, on average, are taller than the birches. These facts suggest that larch saplings can permeate into birch forest patches, probably by seed dispersal, germination, success-ful competition and growth, but birch saplings cannot permeate into larch forest patches. Therefore, on the ecotone, larch forest patches can steadily expand by unceasing permeation into birch forest patches, whereas birch forest patches progressively recede due to ultimate death of the old and poor recruitment of the young. Larch forest patches replace birch forest patches in a stepwise manner, causing succession from birch forests to larch forests. This study not only confirms that larch forests can naturally replace birch forests, but also introduces a simple and reliable method, employing spatial hints, to study forest succession. Additionally, the findings are of benefit to cultivation or development of larch forests in cold or alpine areas of the North Temperate Zone, which can be a huge carbon sink.     

甘肃兴隆山自然保护区森林演替对鸟类群落结构的影响

运用固定面积法调查了青林三个主要演替阶段森林(阔叶林、混交林和针叶林)的鸟类群落结构。结果表明,混交林中鸟类物种数、鸟类物种多样性和种团多样性最高,阔叶林最低。方差分析和聚类分析均表明,三种演替阶段森林的鸟类群落组成差异显著。所记录到的35种鸟类中有11种差异显著。其中,山雀科和科在阔叶林中占优势,而柳莺亚科在混交林和针叶林中占优势。食性种团中,阔叶林以食虫鸟和食果食虫鸟为主;混交林和针叶林均以食虫鸟、食果食虫鸟、食谷鸟和食果鸟为主。鉴于阔叶林和混交林有向顶级群落(针叶林)演替的趋势,建议采取人为干扰来维持三种演替阶段森林的面积,以便从景观水平上保护鸟类物种多样性。     

大兴安岭落叶松林不同演替阶段土壤细菌群落结构与功能潜势

采用土壤细菌16S rDNA高通量测序方法研究了大兴安岭汗马自然保护区落叶松林不同演替阶段的土壤细菌群落结构和功能.结果表明: 不同演替阶段落叶松林土壤细菌优势门为变形菌门、酸杆菌门、疣微菌门、拟杆菌门、放线菌门、浮霉菌门和绿弯菌门,随着演替的进行,酸杆菌门相对丰度逐渐增加,绿弯菌门相对丰度逐渐减少,优势门相对丰度在不同演替阶段不同.细菌群落α多样性在不同演替阶段间无显著差异,但其群落结构分别在落叶松幼龄林与中龄林、幼龄林与过熟林、近熟林与成熟林之间存在显著差异.土壤氧化还原电位、土壤pH和有效磷是影响细菌群落结构的主要环境因素,其中土壤氧化还原电位对微生物群落结构影响最大.随着演替的进行,细菌参与的固氮作用、反硝化作用、氨氧化作用、木质素降解作用呈逐渐减弱的趋势,硫酸盐异化还原作用呈先降后升的趋势,碳固定作用呈先升后降的趋势,碱性磷酸酶没有明显的变化规律,影响土壤功能的主要因素有土壤有效磷和氧化还原电位等.     

Changes in tree phenology along natural regeneration in a seasonally dry tropical forest

The applicability of succession models from temperate and tropical wet forests to threatened seasonally dry tropical forests (SDTFs) is questioned. Plant phenology affects ecosystem functions and changes along forest regeneration gradient. To investigate the recovery of ecological functions after disturbances in a SDTF, we recorded the vegetative and reproductive phenologies for trees (DBH >5 cm) for 17 months in southeast Brazil in three successional stages: early (10–15 years after clearing), intermediate (25–30) and late (>50). The vegetative phenology of the 523 individuals was strongly seasonal, with 3% of individuals presenting green leaves in a deciduous dry season. Besides structural and floristic differences, phenological trends were similar between the later stages. Reproduction occurred with higher intensities in the early stage and in the advanced stages only in the dry season, providing key resources to local fauna. The studied SDTF is resilient to ecological functions, rapidly recovering functional processes. The integration of structural and functional knowledge of succession of STDFs may lead to better management of its secondary remnants. Our study suggests that classical forest succession theory developed for other ecosystems may not fully reflect the pattern of SDTF succession, an ecosystem that originally covered 42% of the earth's tropical and subtropical landmass.     

喀斯特峰丛洼地不同生态系统的土壤肥力变化特征

基于喀斯特峰丛洼地坡耕地、草丛、灌丛、人工林、次生林、原生林6种典型生态系统的土壤主要养分、矿质养分和微生物这3组变量共计20个指标的调查、取样和分析,运用多重比较分析、主成分分析和典范相关分析探讨了其土壤肥力变化特征、主要影响因子及两两之间的相互关系。结果表明,喀斯特峰丛洼地土壤pH值为6.60—7.75,土壤主要养分、微生物种群数量和微生物生物量明显高于同纬度地区地带性红壤,矿质养分含量相对较低,其中SiO2、Al2O3、Fe2O3占矿质全量的90%以上。土壤肥力的总体趋势为原生林>次生林>灌丛>草丛>坡耕地>人工林。喀斯特石漠化地区实行林草结合的退耕还林还草模式更有利于土壤生态系统的环境改善,坡耕地应多施有机肥和氮肥,人工林应多施氮肥。原生林植物与养分之间达到了良好的平衡状态,主要应加强森林抚育管理,改善森林环境,保障植物、土壤养分及微生物之间的良好协调关系。确保土壤资源的合理利用,促进喀斯特峰丛洼地乃至整个西南喀斯特区域植被的迅速恢复和生态重建。     

Legacy forest structure increases bird diversity and abundance in aging young forests

Many studies have demonstrated the importance of early‐successional forest habitat for breeding bird abundance, composition, and diversity. However, very few studies directly link measures of bird diversity, composition and abundance to measures of forest composition, and structure and their dynamic change over early succession. This study examines the relationships between breeding bird community composition and forest structure in regenerating broadleaf forests of southern New England, USA, separating the influences of ecological succession from retained stand structure. We conducted bird point counts and vegetation surveys across a chronosequence of forest stands that originated between 2 and 24 years previously in shelterwood timber harvests, a silvicultural method of regenerating oak‐mixed broadleaf forests. We distinguish between vegetation variables that relate to condition of forest regeneration and those that reflect legacy stand structure. Using principal components analyses, we confirmed the distinction between regeneration and legacy vegetation variables. We ran regression analysis to test for relationships between bird community variables, including nesting and foraging functional guild abundances, and vegetation variables. We confirmed these relationships with hierarchical partitioning. Our results demonstrate that regenerating and legacy vegetation correlate with bird community variables across stand phases and that the strength with which they drive bird community composition changes with forest succession. While measures of regeneration condition explain bird abundance and diversity variables during late initiation, legacy stand structure explains them during stem exclusion. Canopy cover, ground‐story diversity, and canopy structure diversity are the most powerful and consistent explanatory variables. Our results suggest that leaving varied legacy stand structure to promote habitat heterogeneity in shelterwood harvests contributes to greater bird community diversity. Interestingly, this is particularly important during the structurally depauperate phase of stem exclusion of young regenerating forests.     

Linking vegetation structure and bird organization: response of mixed-species bird flocks to forest succession in subtropical China

As forests undergo natural succession following artificial afforestation, their bird assemblages also change. However, interspecific avian social organization associated with forest succession has not been fully understood, particularly for mixed-species bird flocks. To disentangle how mixed-species flocks change as a function of local forest structure, we analyzed flock characteristics (particularly species richness, flocking frequency and propensity) and vegetation physiognomies along a presumed successional series (early, middle, and advanced) simultaneously in subtropical forests in southern China. As hypothesized, monthly point counts demonstrated that complexity of flocks increases with the progression of natural forest succession at a local scale. Advanced forests differed significantly from pioneering plantations with respect to vegetation structure, flock characteristics and constituents (especially for understory specialists). Importantly, forest succession affected flock patterns particularly in relation to the flocking propensity of regular species, and the frequency of nuclear species (Huet’s fulvetta Alcippe hueti), which in turn determined flocking occurrence at different successional stands. Canonical correspondence analysis indicated that understory flocking species (mainly Timaliidae babblers) were significantly associated with intact native canopy cover, complex DBH diversity, as well as high densities of dead trees and large trees, representing a maturity level of successional stands. Our study reveals that the effect of natural forest succession on mixed-species bird flocks is species-specific and guild-dependent. From a conservation perspective, despite a high proliferation of pine plantation in southern China, priority should be placed on protecting the advanced forest with a rich collection of understory flocking specialists.     

Effects of forest modification on bird community composition and seed removal in a heterogeneous landscape in South Africa

Human disturbance threatens and modifies forest ecosystems worldwide. Previous studies have investigated the effects of human impact on local bird communities in disturbed forests, but we still lack information on how bird species richness and ecological processes respond to different forest modifications present at a landscape scale. In a heterogeneous South African landscape, we chose six types of indigenous scarp forest, differing in the intensity of human disturbance: continuous natural forests and natural forest fragments in nature reserves, forest fragments in eucalyptus plantations, fragments in the agricultural matrix, forest gardens and secondary forests in game reserves. In 36 study sites, we investigated the bird community using point counts and observed the seed removal of birds at the native tree species Celtis africana. Species richness did not differ among the forest types, but abundance varied significantly with most birds observed in fragments in the agricultural matrix, forest gardens, and secondary forests. The higher bird abundance in these forests was mainly due to forest generalists, shrubland and open country species whereas forest specialists were rarely present. Changes in species composition were also confirmed by multivariate analysis which clearly separated bird communities by forest type. Frugivore abundance in C. africana was highest in natural forest fragments, fragments in the agricultural matrix, forest gardens and secondary forests. The same trend was found for the estimated total number of fruits removed per C. africana tree, though the differences among forest types were not significant. Consequently, modified forests seem to maintain important ecological functions as they provide food sources for generalist species which may, due to their mobility, enhance natural plant regeneration. However, we could show that protected forest habitats are important refugees for specialist species sensitive to human disturbance.     

松材线虫侵袭引发的植被演替对鸟类群落的影响

松材线虫(Bursaphelenchusxylophilus)是引起严重森林病害的外来物种,可能导致森林生态系统急剧退化。为了探讨在松材线虫侵袭所引起的森林演替过程中植被结构变化对鸟类群落的影响,我们研究了这些常绿阔叶演替林中的鸟类群落结构。2004年5–6月,我们在浙江省宁波市选择了分别处于3个不同演替阶段的7个样地:包括象山县被松材线虫侵袭5年后的常绿阔叶灌丛和侵袭12年后的常绿阔叶林样地各3个,同时在天童国家级森林公园选择了约40龄的常绿阔叶林样地1个。结果显示,在常绿阔叶灌丛和松材线虫侵袭12年后的常绿阔叶林中,鸟类物种多样性和丰富度均显著高于约40龄常绿阔叶林;3类栖息地的鸟类多度、均匀度均无显著差异;在侵袭12年后的常绿阔叶林中鸟类群落最丰富。多元回归分析结果显示,立地年龄是影响鸟类群落组成的主要因素。     

Macrocharcoal-Based Chronosequences Reveal Shifting Dominance of Conifer Boreal Forests Under Changing Fire Regime

Balsam fir (Abies balsamea) and black spruce (Picea mariana) forests are the main conifer forest types in the North American boreal zone. The coexistence of the two species as well as their respective canopy dominance in distinct stands raises questions about the long-term evolution from one forest type to the other in relation to environmental factors including climate and stand disturbance. We tested the hypothesis that repetitive fire events promote the succession of balsam fir forest to black spruce forest and vice versa. Postfire chronosequences of one black spruce (BSP) and one balsam fir (BFI) sites were reconstructed based on the botanical composition and ¹⁴C-dated soil macrocharcoals. The results support the hypothesis of a successional dynamics. The BSP site has been affected by fires for the last 7600 years, whereas the BFI site, after having been impacted by several fires during the first half of the Holocene, evolved in a fire-free environment for the last 4400 years. Periods of fire activity facilitated the dominance of black spruce forests. The cessation of fires around 4400 cal. years BP on BFI site marks the beginning of the transition from black spruce to balsam fir stands. This succession is a long process, due to the ability of black spruce to regenerate by layering in the absence of fire. The resulting balsam fir stands are ancient and precarious ecosystems, since fire generally leads to the return of black spruce. The increase in balsam fir to the detriment of black spruce in boreal forests is a response to a decrease in fire frequency.     

Thermokarst rates intensify due to climate change and forest fragmentation in an Alaskan boreal forest lowland

Lowland boreal forest ecosystems in Alaska are dominated by wetlands comprised of a complex mosaic of fens, collapse‐scar bogs, low shrub/scrub, and forests growing on elevated ice‐rich permafrost soils. Thermokarst has affected the lowlands of the Tanana Flats in central Alaska for centuries, as thawing permafrost collapses forests that transition to wetlands. Located within the discontinuous permafrost zone, this region has significantly warmed over the past half‐century, and much of these carbon‐rich permafrost soils are now within ~0.5 °C of thawing. Increased permafrost thaw in lowland boreal forests in response to warming may have consequences for the climate system. This study evaluates the trajectories and potential drivers of 60 years of forest change in a landscape subjected to permafrost thaw in unburned dominant forest types (paper birch and black spruce) associated with location on elevated permafrost plateau and across multiple time periods (1949, 1978, 1986, 1998, and 2009) using historical and contemporary aerial and satellite images for change detection. We developed (i) a deterministic statistical model to evaluate the potential climatic controls on forest change using gradient boosting and regression tree analysis, and (ii) a 30 × 30 m land cover map of the Tanana Flats to estimate the potential landscape‐level losses of forest area due to thermokarst from 1949 to 2009. Over the 60‐year period, we observed a nonlinear loss of birch forests and a relatively continuous gain of spruce forest associated with thermokarst and forest succession, while gradient boosting/regression tree models identify precipitation and forest fragmentation as the primary factors controlling birch and spruce forest change, respectively. Between 1950 and 2009, landscape‐level analysis estimates a transition of ~15 km² or ~7% of birch forests to wetlands, where the greatest change followed warm periods. This work highlights that the vulnerability and resilience of lowland ice‐rich permafrost ecosystems to climate changes depend on forest type.     

Canopy transpiration of mountain mixed forest as a function of environmental conditions in boundary layer

The canopy transpiration of mountain mixed forest was investigated during summer 2006 at research plot Smrekovec in Tatra National Park in Slovakia after heavy windstorm in November 2004 on the area of 12,000 hectares. The research plot is situated in untouched forest at altitude 1249 m on the southern-east oriented slope. The forest is mixed with 80% of spruce trees and 20% of larch trees with rich under storey vegetation, 120 years old, 7th altitudinal vegetation stage. Whole tree sap flow based on up to dated stem tissue heat balance method was continuously measured in nine 120-years old larch and spruce trees. Stem basal area was used for tree-canopy up-scaling. Meteorological parameters were measured on the top of eddy stuff tower above investigated forest. Two virtual monocultures were assumed for characterizing of both species. The sap flow and tree transpiration were calculated for the whole measured period for both spruce and larch virtual forests.     

Quantifying ecological memory during forest succession: A case study from lower subtropical forest ecosystems in South China

The concept of ecological memory provides a new perspective for research on forest succession by including historical factors and the initial state of ecological processes. However, there are still significant gaps between the concept and its application. We selected nine proxy indicators (plant species, soil seed banks, soil microbes, soil animals, birds, soil age, soil pollen, soil mineral distribution, and light environment) and developed a method to quantify ecological memory and succession in a subtropical forest succession in South China. Taking the climax-monsoon evergreen broad-leaved forest as the reference ecosystem, we found that ecological memory increased nonlinearly and accumulated following a specific assembly rule during succession. Memory concerning major soil microbes and soil animals, which improve the soil substrate, mainly accumulated from the initial to the early successional stage. Memory concerning the number of bird species and the availability of light, which ensure a source of regenerative seeds and the survival of understory seedlings, mainly accumulated from the early to middle successional stages. Memory concerning vegetation and soil seed banks mainly accumulated late in succession, guaranteeing that the ecosystem would reach the regional climax stage. Prospective memory was greater than retrospective memory in every successional stage except the late stage, which indicated that all stages but the late stage were undergoing progressive succession. Our study demonstrates that the concept of ecological memory and the proposed evaluation framework are useful for guiding research on succession and restoration, and especially for assessing how “far” a restored ecosystem is from a reference ecosystem or how far a restored ecosystem has deviated from its natural succession trajectory.     

The Origin and Dynamics of Subalpine White Spruce and Balsam Fir Stands in Boreal Eastern North America

Associations among the few tree species in the North American boreal landscape are the result of complex interactions between climate, biota, and historical disturbances during the Holocene. The closed-crown boreal forest of eastern North America is subdivided into two ecological regions having distinct tree species associations; the balsam fir zone and the black spruce zone, south and north of 49°N, respectively. Subalpine old-growth stands dominated by trees species typical of the balsam fir forest flora (either balsam fir or white spruce) are found on high plateaus, some of which are isolated within the black spruce zone. Here we identified the ecological processes responsible for the distinct forest associations in the subalpine belt across the eastern boreal landscape. Extensive radiocarbon dating, species composition, and size structure analyses indicated contrasted origin and dynamics of the subalpine forests between the two ecological regions. In the black spruce zone, the subalpine belt is a mosaic of post-fire white spruce or balsam fir stands coexisting at similar elevation on the high plateaus. With increasing time without wildfire, the subalpine forests become structurally similar to the balsam fir forest of the fir zone. These results concur with the hypothesis that the subalpine forests of this area are protected remnants of an historical northern expansion of the fir zone. Its replacement by the fire-prone black spruce forest flora was caused by recurrent fires. In the subalpine belt of the fir zone, no fire was recorded for several millennia. Harsh climate at high altitude is the primary factor explaining white spruce dominance over balsam fir forming a distinct subalpine white spruce belt above the balsam fir dominated forest.     

Succession Influences Wild Bees in a Temperate Forest Landscape: The Value of Early Successional Stages in Naturally Regenerated and Planted Forests

In many temperate terrestrial forest ecosystems, both natural human disturbances drive the reestablishment of forests. Succession in plant communities, in addition to reforestation following the creation of open sites through harvesting or natural disturbances, can affect forest faunal assemblages. Wild bees perform an important ecosystem function in human-altered and natural or seminatural ecosystems, as they are essential pollinators for both crops and wild flowering plants. To maintain high abundance and species richness for pollination services, it is important to conserve and create seminatural and natural land cover with optimal successional stages for wild bees. We examined the effects of forest succession on wild bees. In particular, we evaluated the importance of early successional stages for bees, which has been suspected but not previously demonstrated. A range of successional stages, between 1 and 178 years old, were examined in naturally regenerated and planted forests. In total 4465 wild bee individuals, representing 113 species, were captured. Results for total bees, solitary bees, and cleptoparasitic bees in both naturally regenerated and planted conifer forests indicated a higher abundance and species richness in the early successional stages. However, higher abundance and species richness of social bees in naturally regenerated forest were observed as the successional stages progressed, whereas the abundance of social bees in conifer planted forest showed a concave-shaped relationship when plotted. The results suggest that early successional stages of both naturally regenerated and conifer planted forest maintain a high abundance and species richness of solitary bees and their cleptoparasitic bees, although social bees respond differently in the early successional stages. This may imply that, in some cases, active forest stand management policies, such as the clear-cutting of planted forests for timber production, would create early successional habitats, leading to significant positive effects for bees in general.     

Assessing avian diversity and community composition along a successional gradient in traditional Lacandon Maya agroforests

Evidence regarding the ability of agroforests to conserve biological diversity has been mixed; they tend to maintain avian communities with species richness similar to that of undisturbed forest ecosystems but generally do not completely preserve community composition. Using a combination of occupancy modeling and non-metric multidimensional scaling on point-count data, we assessed changes in avian community diversity and composition along a successional gradient in traditional Lacandon Maya agroforests and compared them to protected areas in the region. Bird species richness and diversity in Lacandon agroforests peaked in early secondary forest stages. These agroforests' mean Shannon–Weiner diversity was 5% higher than that of nearby protected areas, but their species richness was similar. Community composition in Lacandon agroforests changed throughout succession, with earlier stages supporting communities distinctly characterized by generalist species, while subsequent, less-intensively managed stages tended to support more forest-dwellers. The bird community observed in even the most mature secondary forest stages in Lacandon agroforests differed from that of undisturbed rain forest ecosystems. These results demonstrate the potential of traditional Lacandon agroforestry management to conserve avian biodiversity while ensuring food sovereignty for farmers. However, because the community composition of early-successional stages was different than later stages, shortening fallow cycles and reducing forest cover to increase agricultural production will limit the species this system can support. This study illustrates the value of incorporating traditional agroecosystems into conservation planning as well as maintaining protected areas, because the latter serve as refugia for species that require undisturbed forest habitat in an agroecological matrix.     

Assemblages of wood-inhabiting fungi along the gradients of succession and naturalness in boreal pine-dominated forests in Fennoscandia

In boreal forests, the level of naturalness and the stage of succession explain most of the variation in forest structure within a particular forest type. Thus, these two factors should also have a major effect on species assemblages in forests, at least on species groups associated with wood. The present study is the first attempt to analyze empirically the simultaneous effects of forest succession and naturalness on wood-inhabiting fungi, a taxonomic group of special ecological importance. The study area was situated in eastern Finland, middle boreal zone. A total of 41 study plots were established in Pinus sylvestris forests representing three levels of forest naturalness: natural, seminatural and intensively managed forests. Five stages of succession were distinguished according to the age of the dominating tree layer (<10, 40, 70, 110, and >150 yr old), except in managed forests where only four stages were available. A total of 5328 records of 195 species of fungi were made. The first, open stage of succession was clearly the most species-rich period of succession in all levels of forest naturalness. In natural and seminatural forests, the first stage of succession was also very distinctive in its fungal composition, and thus of special value in protecting biodiversity in boreal forests. In the succession following the first stage, the level of naturalness had more effect on assemblages of fungi than did the stage of succession. Intensive forest management affects threatened species particularly. In conclusion, natural young stages of succession should also be included in the network of boreal forest reserves.     

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.     

Structure and Composition of Natural Gmelin Larch (Larix gmelinii var. gmelinii) Forests in Response to Spatial Climatic Changes

Background

Many theoretical researches predicted that the larch species would decrease drastically in China under future climatic changes. However, responses of the structural and compositional changes of Gmelin larch (Larix gmelinii var. gmelinii) forests to climatic changes have rarely been reported.

Methodology/Principal Findings

Field survey was conducted to examine the structures and compositions of natural Gmelin larch forests along a climatic gradient. Stepwise linear regression analyses incorporating linear and quadratic components of climatic and non-climatic factors were performed on the structural and compositional attributes of those natural Gmelin larch forests. Isothermality, Max Temperature of Warmest Month (TempWarmestMonth), Precipitation of Wettest Month (PrecipWettestMonth), Precipitation Seasonality (PrecipSeasonality) and Precipitation of Driest Quarter (PrecipDriestQuarter) were observed to be effective climatic factors in controlling structure and composition of Gmelin larch forests. Isothermality significantly affected total basal area of larch, while TempWarmestMonth, PrecipWettestMonth and PrecipSeasonality significantly affected total basal area of Mongolian pine, and PrecipDriestQuarter significantly affected mean DBH of larch, stand density of larch and total basal area of spruce and fir.

Conclusions/Significance

The summer and winter temperatures and precipitations are all predicted to increase in future in Northeast China. Our results showed the increase of total basal area of spruce and fir, the suppression of regeneration and the decrease of stand density of larch under increased winter precipitation, and the decrease of total basal area of larch under increased summer temperature in the region of current Gmelin larch forest. Therefore, we suggest that larch would decrease and spruce and fir would increase in the region of future Gmelin larch forest.