Landscape context of plantation forests in the conservation of tropical mammals

Plantation forests have been expanding in many tropical and subtropical environments. Howerver, even when they replace less wildlife friendly land uses such as pastures and annual crops, the biodiversity levels of pristine natural habitats often have not been recovered. Here we addressed how the landscape context of plantation forests located in South-eastern Brazil affects species richness and community resilience of medium and large size mammals. The area covered by native habitat fragments surrounding plantation forests is positively related to functional richness, including the presence of species more vulnerable to extinction in fragmented landscapes. In addition, the degree of aggregation of plantation forest stands is negatively related to more vulnerable species. No primates were recorded in our seven plantation forest sites (ranging from 272 to 24,921 ha), even when they were seen in native habitat fragments adjacent to commercial tree stands. Two invasive species (Sus scrofa and Lepus capensis) were recorded in four plantation forest sites. The impoverishment of fauna in plantation forests is due to two factors. First, plantation forests generally are structurally simplified habitats when compared to highly diverse tropical forests. Secondly, the isolation from habitat fragments which act as source of individuals in the landscape precludes the establishment of individual in plantation forest. We also highlighted the management practices to improve the complexity of vegetation in commercial tree stands should be taken cautiously, insofar as reduced productivity per area entails a greater demand for land. Thus, an alternative would be intensify the management of the commercial tree stands for wood production together with the restoration of adjacent areas set aside to conservation and native habitat fragments protection.     

A general framework to describe the alteration of natural tree species composition as an indicator of forest naturalness

The alteration of natural tree species composition is defined as the deviation of the current tree species composition from that of the natural state. It can be used as a measure of human influence on forest vegetation, and thus as an indicator of the naturalness of forest vegetation. The aim of the study was to develop a standard procedure for estimating the alteration of natural tree species composition, to explain factors driving alteration and to examine its significance for susceptibility of forest stands to natural disturbances. The alteration of natural tree species composition was estimated for the Dinaric region (5556 km², Slovenia) by the Robič Index of Dissimilarity (RID), ranging from 0 (completely natural) to 100 (completely altered). The index was calculated on the compartment level (24 ha each on average) with data on current and potential natural forest vegetation. The influence of human activities on tree species alteration was examined by using topographic and accessibility variables. The susceptibility of forest stands to natural disturbances was analysed with data on sanitary felling. In the study area, the natural tree species composition of forest stands is moderately preserved; the average value of RID was 50.05, ranging from 1.76 to 100, and the coefficient of variation was 0.49. The alteration of the natural tree species composition of forest stands is primarily the result of forest management and past land use, conditioned either by topography or accessibility of forests. The degree of alteration of tree species composition decreased along the gradients of rockiness, inclination and elevation. A greater degree of alteration appeared on the slopes of intermediate and south facing aspects than on north facing slopes, and in areas that were closer to the forest edge. A higher level of alteration significantly increases the susceptibility of forest stands to natural disturbances. The procedure represents a novel approach in modelling the alteration (naturalness) of tree species composition of forest vegetation. It is applicable at different spatial scales and fosters an understanding of the patterns of tree species composition under the influence of human activity across forest landscapes.     

Landscape-level tree diversity assessment in tropical forests of southern Eastern Ghats,India

This large-scale, landscape-level study aims to assess tree species diversity, stem density and stand structure of six major tropical hill forests of southern Eastern Ghats, India, namely, Bodamalai (BM), Chitteri (CH), Kalrayan (KA), Kolli hills (KO), Pachaimalai (PM) and Shervarayan hills (SH). The Eastern Ghats of India is relatively under-studied compared with the Western Ghats biodiversity hotspot. The entire stretch of southern Eastern Ghats was divided into smaller grids of 6.25 km × 6.25 km, totaling to 120 grids. Within each grid, a belt transect of 0.5 ha (5 m × 1000 m) area was laid and all trees ≥30 cm girth at breast height (gbh) were enumerated. A total of 272 tree species (≥30 cm gbh) that belonged to 181 genera and 62 families were recorded in the total 60 ha area inventoried. Diversity indices such as Shannon, Simpson and Fisher's alpha indices were 2.44, 0.03 and 42.1, respectively, for the whole 60 ha area. One way ANOVA revealed that the species richness varied significantly across the six sites (F_(5,823) = 4.854, p < 0.0002). Also, the contribution of tree species to total species richness classified by three plant types viz. evergreen, brevi-deciduous and deciduous species varied significantly across the sites (One way ANOVA: F_(2,15) = 10.05, p < 0.002). Similarity indices such as Jaccard and Sørensen showed that sites CH and KA are more similar in terms of species composition. The total stand density and basal area for the total 60 ha area were 27,412 stems (457 stems ha⁻¹) and 1012.12 m² (16.9 m² ha⁻¹), respectively. The stand density and basal area for the six sites ranged from 290 (in site BM) to 527 stems ha⁻¹ (in site KA) and from 5.6 (in site BM) to 24.4 m² ha⁻¹ (in site KO), respectively. Stand density and basal area of tree species varied significantly across the six hill complexes (F_(5,823) = 4.85, p < 0.0002 and F_(5,823) = 2.71, p < 0.02, respectively). A positive correlation was obtained between stand density and species richness in sites PM (r_s = 0.65, p < 0.05) and SH (r_s = 0.67, p < 0.05), but not in other sites. The predominant tree species in the tropical forests of southern Eastern Ghats include Albizia amara, Euphorbia antiquorum, Canthium dicoccum var. dicoccum, Memecylon edule, Chloroxylon swietenia and Nothopegia heyneana. Taxonomically, Euphorbiaceae constituted the most diverse family with 25 species. Whereas, by tree abundance the Mimosaceae with 4126 stems enumerated from the 60 ha area formed the dominant family. Bray–Curtis cluster analysis, based on tree species composition and abundance revealed that the low-diverse site BM formed a separate entity from other hill complexes. This large-scale tree diversity inventory provides a baseline data for a variety of investigations and is expected to be useful for effective forest management and biodiversity conservation of southern Eastern Ghats region.     

Tree Species Composition, Structure, and Aboveground Wood Biomass of a Riparian Forest of the Lower Miranda River, Southern Pantanal, Brazil

The aboveground wood biomass (AWB) of tropical forests plays an important role in the global carbon cycle, and local AWB estimates provide essential data that enable the extrapolation of biomass stocks to ecosystem or biome-wide carbon cycle modelling. Few AWB estimates exist in Neotropical freshwater floodplains, where tree species distribution and forest structure depend on the height and duration of periodic inundations. We investigated tree species composition, forest structure, wood specific gravity, and AWB of trees ≥10 cm dbh in 16 plots totalling an area of 1 ha in a seasonally inundated riparian forest of the lower Miranda River, southern Pantanal, Brazil. The 443 tree individuals belonged to 46 species. Four species (Inga vera, Ocotea suaveolens, Tabebuia heptaphylla and Cecropia pachystachya) comprised more than 50% of the Total Importance Values (TIV), and floristic similarities between the plots averaged 38%. Although we detected an overall increase in species diversity correlated with decreasing flood levels, the most important tree species had almost identical distribution patterns along the flooding gradient. The stand basal area per plot (±?s.d.) amounted to 3.0?±?1.1 m² (47.8?±?18.1 m²/ha), and the tree heights averaged 10.9?±?1.4 m. Multiplying the individual basal areas by individual tree heights and a form factor of 0.6, we estimated the aboveground wood volume (AWV) for each individual, and for each plot (24.4?±?11.7 m³, 391.1?±?188 m³/ha). Wood specific gravity (SG) varied between 0.39 g/cm³ (Cecropia pachystachya) and 0.87 g/cm³ (Tabebuia heptaphylla), with a stand level average of 0.63?±?0.12 g/cm³. Multiplying the individual AWV with species SG, we estimated the plot AWB to be 16.2?±?6.4 Mg (259.4?±?102 Mg/ha). This value is comparable to that reported for late-successional forest stands of Amazonian floodplain forests, and it is close to the worldwide tropical average AWB. Because tree heights in the present forest were comparatively low when compared to other Neotropical forests, we found that resprouting of stems accounted for comparatively high basal areas. We argue that stem resprouting is an adaptation of tree species originating in non-flooded Cerrado to the seasonal inundations of riparian forests.     

Conservation value of timber quality versus associated non-timber quality stands for understory diversity in Nothofagus forests

Conservation strategies of forested landscapes must consider biodiversity of the included site types, i.e. timber-quality forests and associated non-timber-quality stands. The objectives were to characterize forest overstory structure in timber-quality versus associated non-timber-quality stands; and to compare their understory communities. Six forest types were sampled in Nothofagus forests of Tierra del Fuego (Argentina): two timber-quality N. pumilio forests, and four associated non-timber-quality stands (edge, N. antarctica, wetlands and streamside forests). Overstory structure and understory vegetation (species richness, frequencies, cover and biomass) were characterized during spring and summer seasons. Analysis of variance and multivariates were carried out. Overstory structure differed across the site types, with higher tree size, canopy closure and tree volume in timber-quality stands. Fifty-one understory plant species were observed, but understory variables varied with site types, especially wetlands (highest native and exotic richness, cover and biomass, and 25% of exclusive species). Site types were grouped in three: N. antarctica stands, streamside stands and the other N. pumilio forests according to multivariate analysis. Forty three percent of plants were distributed in all site types, and all timber-quality forest understory species were present in some associated non-timber-quality stands. Timber-quality N. pumilio forests have a marginal value for understory conservation compared to associated non-timber-quality stands, because these last include all the plants observed in timber-quality forests and also possess many exclusive species. Therefore, protection of associated non-timber-quality stands during forest management planning could increase understory conservation at landscape level, and these could be better reserves of understory diversity than retentions of timber-quality stands.     

六盘山森林植被碳密度空间分布特征及其成因

深入了解干旱缺水地区森林植被碳密度的空间分布特征是定量评价森林固碳能力、合理协调林水矛盾的重要基础。然而,目前有关干旱缺水地区的植被碳密度的研究仅限于典型样地上的碳储量、碳密度的比较,对区域尺度上森林植被碳密度的空间分布特征了解较少。为此,利用宁夏六盘山自然保护区2005年森林资源一类清查数据,计算了森林植被碳密度,并分析了其与林分结构特征和环境因子的关系。结果表明,六盘山的森林植被碳密度(t/hm2)平均为26.17(0.67—120.63),其中天然次生林为30.2(7.6—120.6),显著高于人工林的15.7(0.67—66.7)。森林植被碳密度随林龄增加而线性增大,天然林和人工林的平均增速分别为1.11和2.48 t hm-2a-1,而且,部分未成熟林的林分植被碳密度已接近甚至超过全国同类森林类型成熟林的植被碳密度平均值。随林分密度增加,森林植被碳密度增大,但在林分密度1000株/hm2后,森林植被碳密度不再增大,达到其最大值,其中,天然林为75.4 t/hm2,人工林为34.6 t/hm2;林冠郁闭度对森林植被碳密度的影响与林分密度相似,森林植被碳密度增长的郁闭度拐点为0.5。水分条件是影响六盘山森林植被碳密度的重要因素,森林植被碳密度(t/hm2)由700 mm以上地点的32.5(7.6—120.6)下降至年降水量500—600 mm地点的10.9(0.67—42.9),而且随年降水量减少,最大森林植被碳密度所对应的海拔高度呈增加趋势,如在年降水量为700、600—700和600 mm的地区,最大碳密度所在海拔高度分别为1900—2100、2100—2300和2300—2500 m。综上所述,研究区森林植被还有较大的固碳潜力,从提高森林固碳功能角度来看,林分郁闭度不宜超过0.5。     

Biomass,carbon density and diversity of tree species in tropical dry deciduous forests in Central India

Tropical dry deciduous forests play a significant role in regulating the biogeochemical cycles. Present study assesses the carbon stock of tropical dry deciduous forests varying in tree density, basal cover, and diversity located in Singrauli district of Madhya Pradesh in Central India. Field sampling was carried out in six forest sites viz., Chitrangi, East Sarai, Gorbi, Renukoot, West Sarai, and Waidhan, of Singrauli. A total of 29 tree species belonging to 18 families were recorded across the forest ranges where tree density, basal area and diversity values varied from 702 (Gorbhi Range) – 1671 (East Sarai range) individuals ha^?1; 15.43 (Renukhund range) – 71.76 m² ha^?1 (Chitrange range) and 0.69 (West Sarai range) – 2.52 (Gorbi range), respectively. Total biomass estimated ranged from 103.32 (Renukhund range) – 453.54 Mg ha^?1 (Chitrange range) while the total tree carbon density varied from 48.97 to 214.97 Mg C ha^?1. The variation in carbon storage in the studied ranges was found dependent on density of trees in different diameter and age classes and tree species diversity. Diospyros melanoxylon, Butea monosperma, Shorea robusta, Senegalia catechu, Spondias pinnata, and Lagerstroemia parviflora were the dominant species at different study sites (forest ranges) and contributed towards higher carbon storage in respective forest ranges. Study endorses field-based approach for carbon estimations based on above and belowground assessments as a more realistic approach to understand sink potential of natural forests.     

Rapid Increases in Forest Understory Diversity and Productivity following a Mountain Pine Beetle (Dendroctonus ponderosae) Outbreak in Pine Forests

The current unprecedented outbreak of mountain pine beetle (Dendroctonus ponderosae) in lodgepole pine (Pinus contorta) forests of western Canada has resulted in a landscape consisting of a mosaic of forest stands at different stages of mortality. Within forest stands, understory communities are the reservoir of the majority of plant species diversity and influence the composition of future forests in response to disturbance. Although changes to stand composition following beetle outbreaks are well documented, information on immediate responses of forest understory plant communities is limited. The objective of this study was to examine the effects of D. ponderosae-induced tree mortality on initial changes in diversity and productivity of understory plant communities. We established a total of 110 1-m² plots across eleven mature lodgepole pine forests to measure changes in understory diversity and productivity as a function of tree mortality and below ground resource availability across multiple years. Overall, understory community diversity and productivity increased across the gradient of increased tree mortality. Richness of herbaceous perennials increased with tree mortality as well as soil moisture and nutrient levels. In contrast, the diversity of woody perennials did not change across the gradient of tree mortality. Understory vegetation, namely herbaceous perennials, showed an immediate response to improved growing conditions caused by increases in tree mortality. How this increased pulse in understory richness and productivity affects future forest trajectories in a novel system is unknown.     

STABILITY AND INSTABILITY IN PLANT COMMUNITIES FOLLOWING FIRE

Tree species composition and density were monitored in closed oak-hickory forest and forest-prairie edge for a period of five years after a prescribed burn. In the closed forest, tree stem density declined markedly following the burn. Tree basal area and density decreased from 17.5 m²/ha and 630 trees/ha in the preburn sample to 12.0 m²/ha and 310 trees/ha five years later. In contrast, on the forest-prairie edge, tree basal area and density increased slightly during the same time period from 3.0 m²/ha and 117 trees/ha to 5.2 m²/ha and 172 trees/ha. Our data suggest that closed canopy forests in fire susceptible areas accumulate fuels to levels that encourage fires of sufficient intensity to destabilize forest systems and convert them to open forests or savannahs. Conversely, on the forest-prairie edge, amounts and patterns of fuel accumulation, and species response to burning, are such that fire can be considered to be a factor promoting stability.     

Richness and Density of Birds in Timber <Emphasis Type="Italic">Nothofagus pumilio</Emphasis> Forests and their Unproductive Associated Environments

Research on forest management impact focuses mainly on timber stands, and leaves out the unproductive forest environments. These stands are spatially mixed with timber forests. The objective was to evaluate richness and density of birds in timber Nothofagus pumilio forests and their unproductive associated environments, and discuss forest management implications. These stands showed significant differences in their forest structure, which generate a great variety of ecological environments. A total of 1881 individuals belonging to 30 bird species were observed during the sampling, in spring and summer seasons. These species were mainly migratory and insectivores, Passeriforms being the most important group. From 12 to 17 birds/ha were found, which varied with the forest environments and seasons. Timber stands of Nothofagus pumilio support a low number of bird species. Most of them are opportunistic and a few prefer these woods over other forested or afforested areas. Low bird density and richness characterize these austral forests, which share their diversity with a high variety of ecosystems along Patagonia. Timber N. pumilio forests has a marginal value for bird species conservation, considering its richness, density and the percentage of this forest in the total forested landscape of Tierra del Fuego (Argentina).     

Quantifying tree carbon stock in historically conserved Seminary Hills urban forest of Nagpur,India

Urban forests help regulating flow of ecosystem services and are efficient to sequester atmospheric carbon. Tree carbon stock in urban forests and green spaces can help improving human well-being. Nagpur being one of the fastest growing urban agglomerate in India that has faced rapid loss of green spaces in last three decades. Present study assessed tree biomass carbon storage potential of a historically conserved large (67.41 ha) Seminary Hills Reserve forest of Nagpur. A total of 150 quadrats of 100 m² were laid to understand the vegetation structure and tree biomass storage. Overall structure and composition of the forest was assessed while, non-destructive biomass estimation was carried out using tree volume eqs. A total of 27 tree species belonging to 12 plant families were observed from the forest with only 6 tree species being dominant and remaining 21 being rare in occurrence. The maximum tree carbon storage was observed in dominant tree species of Hardwickia binata (76.30 t C ha^?1) followed by 17.04 t C ha^?1 in Tectona grandis and 1.19 t C ha^?1 in Boswellia serrata. Carbon stock in other co-dominant species was reported in Terminalia bellirica (76.57 kg C ha^?1), Gardenia resinifera (1118.6 g C ha^?1) and Terminalia arjuna (84.8 g C ha^?1). Total carbon stock of dominant tree species present in Seminary Hills urban forest was 94.53 ± 39.6 t C ha^?1. The study intends to bring focus ecosystem benefits from Urban Forests in growing urban sprawls of India and the need to include their vital role in urban planning.     

Structure of a pristine Picea abies forest in northeastern Europe

Abstract. The forest structure in a large, relatively homogeneous area of pristine Picea abies taiga in the southern boreal region west of the Ural mountains was studied along four 500-m long transects. P. abies dominated the forest in association with Abies sibirica and Betula spp. The mean volume of living trees was 216 m³/ha. This value varied among the four transects, from 138 - 252 m³/ha. Mean density of trees (DBH > 1 cm) (and variation over the transects) was 2 064/ha (1670 - 2710). Living trees classified as dying or seriously damaged made up 2.9 (2.5 - 3.5) % of the living tree volume. Betula was an important canopy component and made up 16% of the living tree volume. The number of dead standing trees varied from 195 - 325/ha, corresponding to a volume of 10.8 - 70.7 m³/ha. The density of trees with a broken stem was 90 - 170/ha and their estimated volume 7.6 - 41.3 m³/ha. Standing dead trees and trees with broken stems represented 10.4 and 8.9% of the total standing tree volume (living + dead), respectively. The mean volume of decaying logs on the forest floor was 117 (84.4–156.2) m³/ha, corresponding to 54 (35 - 113) % of the living tree volume. The canopy-forming trees were present in the understory as abundant saplings and suppressed individuals. The size distribution of the dominant tree species resembled the inverse J-shape. Generally, the forest was characterized by a high small-scale structural variation and a larger-scale relative homogeneity. This pattern is consistent with forest dynamics where the forest consists of a small-scale mosaic of patches in different stages of recovery following disturbance. Our results suggest that the ecology and dynamics of extensive areas of natural boreal forests can be driven by small-scale disturbance.     

Effects of overstory and understory vegetation on the understory light environment in mixed boreal forests

Abstract. The percentage of above-canopy Photosynthetic Photon Flux Density (%PPFD) was measured at 0, 50 and 100 cm above the forest floor and above the main understory vegetation in stands of (1) pure Betula papyrifera (White birch), (2) pure Populus tremuloides (Trembling aspen), (3) mixed broad-leaf-conifer, (4) shade-tolerant conifer and (5) pure Pinus banksiana (Jack pine) occurring on both clay and till soil types. %PPFD was measured instantaneously under overcast sky conditions (nine locations within each of 29 stands) and continuously for a full day under clear sky conditions (five locations within each of eight stands). The percentage cover of the understory layer was estimated at the same locations as light measurements. Mean %PPFD varied from 2% at the forest floor under Populus forests to 15% above the understory vegetation cover under Betula forests. Percent PPFD above the understory vegetation cover was significantly higher under shade intolerant tree species such as Populus, Betula and Pinus than under shade tolerant conifers. No significant differences were found in %PPFD above the understory vegetation cover under similar tree species between clay and till soil types. The coefficient of variation in %PPFD measured in the nine locations within each stand was significantly lower under deciduous dominated forests (mean of 19%) than under coniferous dominated forests (mean of 40%). %PPFD measured at the forest floor was positively correlated with %PPFD measured above the understory vegetation and negatively correlated with cumulative total percent cover of the understory vegetation (R² = 0.852). The proportion of sunflecks above 250 and 500 mmol m^–2 s^–1 was much lower and %PPFD in shade much higher under Populus and Betula forests than under the other forests. Differences in the mean, variability and nature of the light environment found among forest and soil types are discussed in relation to their possible influences on tree succession.     

Morphological plasticity of Parrotia persica leaves in eastern Hyrcanian forests (Iran) is related to altitude

Variation in leaf characters of Parrotia persica in relation to their position in the canopy along an altitudinal gradient were studied. Genetic and phenotypic characters make P. persica one of the most noteworthy plants in the five floristic regions of Iran. It is an endemic species of the Hyrcanian forests, and occurs naturally from sea level to over 900 m a.s.l. on the north side of the Mountain Ranges of Alborz, northern Iran. There was a significant effect of altitude only on few leaf features [width of lamina, base angle (internal angle of lamina), number of pair vein (number of principal veins of lamina) of leaf, top and end of leaf figure]. Among different geographical sides of the crown, there was no significant difference in the plasticity of leaf features, but leaf figure (both top of leaf figure and end of leaf figure) showed the lowest plasticity among the different leaf characters. Of all characters measured, the lowest plasticity among the three populations was found for base angle and number of vein pairs. A PCA analysis showed that leaf petiole and maximum width of lamina in 0.9 of its length, together with leaf figure and width of lamina, accounted for the greatest variation in difference of populations.     

岷江冷杉林皆伐后次生群落结构和物种多样性的演替动态

为阐明岷江冷杉林皆伐后次生群落的演替过程,采用空间代替时间的方法,在川西米亚罗林区海拔3100—3600 m的阴坡选择岷江冷杉林皆伐后次生演替10、20、30、40和50a阶段的次生群落作为研究对象,对其群落结构和物种多样性的动态进行了研究。不同演替阶段的树木均呈显著聚集分布。按群落中优势种的重要值将该演替序列划分为3个类型:悬钩子-蔷薇灌丛、白桦阔叶林和桦木-岷江冷杉针阔混交林。随次生演替,乔木和灌木种的物种丰富度趋于增加,而草本种的物种丰富度趋于减少;乔木和灌木种的Shannon-Wiener多样性指数趋于增大,而草本的Shannon-Wiener多样性指数趋于减小;乔木、灌木和草本层的Pielou均匀度指数均趋于增大;乔木层的Simpson优势度指数趋于减小,灌木和草本层的Simpson优势度指数在演替0—40年阶段趋于增大,而在演替50a阶段趋于减小。在该演替序列中,乔木、灌木和草本层的物种组成均呈耐荫种替代非耐荫种的趋势。     

Regeneration of Betula albosinensis in Strip Clearcut and Uncut Forests of the Qinling Mountains in China

To contribute to a better understanding of the regeneration strategy of Betula albosinensis forests and the likely reasons behind either the successful recovery or failure after strip clearcutting, we compared the population structures and spatial patterns of B. albosinensis in eight B. albosinensis stands in Qinling Mountains, China. Four cut and four uncut stands were selected, and each sampled using a single large plot (0.25 ha). Results indicated that, on the one hand, B. albosinensis recruitment was scarce (average of 48 stems ha⁻¹) in the uncut stands, relative to the mature population (average of 259 stems ha⁻¹), suggesting a failure of recruitment. On the other hand, the subsequent regeneration approximately 50 years after the strip clearcutting showed that the density of the target species seedlings and saplings has increased significantly, and the current average density of seedlings and saplings was 156 stems ha⁻¹. The clumped spatial pattern of B. albosinensis suggested that their regeneration was highly dependent on canopy disturbance. However, recruitment remained poor in the uncut stands because most gaps were small in scale. The successful regeneration of sunlight-loving B. albosinensis after strip clearcutting was attributed to the exposed land and availability of more sunlight. Bamboo density did not influence B. albosinensis recruitment in the uncut stands. However, stand regeneration was impeded after strip clearcutting; thus, removing bamboo is essential in improving the competitive status of B. albosinensis at the later stage of forest regeneration after clearcutting. The moderate severity of disturbance resulting from strip clearcutting reversed the degeneration trend of primary B. albosinensis stands. This outcome can help strike a balance between forest conservation and the demand for wood products by releasing space and exposing the forested land for recruitment. Life history traits and spatiotemporal disturbance magnitude are important factors to consider in implementing effective B. albosinensis regeneration strategies.     

Structural heterogeneity and tree spatial patterns in an old-growth deciduous lowland forest in Cantabria, northern Spain

Old-growth deciduous forests in western Europe, for the most part, consist of small tracts that often may be atypical due to human disturbance, poor soil productivity or inaccessibility. In addition, very little information on tree age distributions, structural heterogeneity and tree spatial patterns appears to be available for west-European forests. Characterization of the structural features of tree populations in these old-growth stands can provide the basis to design conservation plans and also inform on how present forests might look in the absence of human interference. Four old-growth stands in a deciduous forest in the Cantabrian lowlands, northern Spain, were surveyed to determine forest structure and spatial patterns. Live and dead trees were identified, measured and mapped, and live trees were cored for age estimation. Structural heterogeneity was analyzed by means of the spatial autocorrelation of tree diameter, height and age, and the uni- and bivariate spatial patterns of trees were analyzed. The dominant species, Fagus sylvatica and Quercus robur, showed reverse-J shaped size distributions but discontinuous age distributions, with maximum ages of 255–270 yr. Tree ages suggested that the forest was largely modified by past changes in forest-use, especially by temporal variation in grazing intensity. Spatial autocorrelation revealed that former parkland stands were heterogeneous with respect to tree height only, while high forest stands were composed of patches of even-aged and even-sized trees. Young trees were clumped at varying distances and establishment occurred preferentially in canopy gaps, except for Ilex aquifolium that mainly occurred beneath mature Quercus trees. Surviving trees became less intensely clumped in the dominant species, and more strongly clumped in understorey ones, which may have been due to the effects of intraspecific competition and of canopy trees on tree survival, respectively. The spatial associations between species varied within the forest, probably as a consequence of specific establishment preferences and competitive interactions.     

Biomass carbon density and carbon sequestration capacity in seven typical forest types of the Xiaoxing’an Mountains,China

森林生物碳储量作为森林生态系统碳库的重要组成部分,在全球碳循环中发挥着重要作用。以小兴安岭7种典型林型为研究对象,通过外业样地调查与室内实验分析相结合的方法,从林分尺度对林分生物量与碳密度进行计量,分析了林分生物碳储量的空间分配格局,并对林分年固碳能力与碳汇潜力进行了探讨。结果表明:小兴安岭不同林型从幼龄林到成熟林的乔木层碳密度增长速率为:蒙古栎(Quercus mongolica)林>兴安落叶松(Larix gmelinii)林>云冷杉(Picea-Abies)林>樟子松(Pinus sylvestris var.mongolica)林>山杨(Populus davidiana)林>红松(Pinus koraiensis)林>白桦(Betula platyphylla)林。7种典型林型不同龄组(幼龄林、中龄林、近熟林和成熟林)林分生物量碳密度分别为:红松林31.4、74.7、118.4和130.2 t·hm–2;兴安落叶松林28.9、44.3、74.2和113.3 t·hm–2;樟子松林22.8、52.0、71.1和92.6 t·hm–2;云冷杉林23.1、44.1、77.6和130.3 t·hm–2;白桦林18.8、35.3、66.6和88.5 t·hm–2;蒙古栎林25.0、20.0、47.5和68.9 t·hm–2;山杨林19.8、28.7、43.7和76.6 t·hm–2。红松林、兴安落叶松林、樟子松林和蒙古栎林在幼龄林时林分年固碳量较高,其他林型在成熟林时林分年固碳量较高。7种典型林型不同龄组的林分生物量碳密度均随林龄增长而增加,但不同林型的碳汇功能存在差异,同一林型不同林龄的生物量碳密度增幅差异也较大。林分年固碳量在0.4–2.8 t·hm–2之间,碳汇能力较强、碳汇潜力较大。尤其是小兴安岭目前林分质量较差,幼龄林和中龄林所占的比重较大,具有较大的碳汇潜力。研究结果可为森林经营管理及碳汇功能评价提供参考。     

Plant species diversity,community structure and invasion status in insular primary forests on the Sekimon uplifted limestone (Ogasawara Islands)

Native forests on oceanic islands are among the most threatened ecosystems. The forests formed on Sekimon uplifted limestone in Haha-jima Island (Ogasawara Islands) have not yet been destroyed by human activities and remain as primary forests harboring several narrow endemic endangered plants. In this paper, we described the plant species diversity, community structure, and status of invasion by alien plants in the mesic forests of Sekimon. The Sekimon forest was characterized by low tree diversity (37 species), high stem density (1731 ha^?1), and high basal area (63.9 m² ha^?1), comparing with natural forests in world islands. The forests were dominated in the number of stems by the sub-tree Ardisia sieboldii followed by the trees Pisonia umbellifera and Elaeocarpus photiniifolius. The invasive tree Bischofia javanica ranked fourth for basal area and third for the number of stems (DBH?≥?10 cm), and its distribution expanded, especially near a past plantation site. Surveys of forest floor vegetation revealed that species richness of vascular plants was 109 species and that many alien plants had already invaded the forests. Despite the low species richness of alien (16% for vascular flora and 8% for trees), the high frequency of aliens on the forest floor suggests that they have colonized successfully in the Sekimon forest. Extrapolation analysis based on the rarefaction curves predicted that the vascular plants in the Sekimon (25 ha) accounted for 135 species (29.9% of the vascular flora of the Ogasawara Islands) and endemic plants were 85 species (62.0%). The fact that the 39 vascular species recorded in our plots were listed in Japanese Red List suggests that the Sekimon forest should be conserved as a sanctuary of biodiversity. Because alien plants are invading the forests without apparent anthropogenic disturbance, immediate action to eradicate these invaders is highly needed.     

Investigating the role of impoundment and forest structure on the resistance and resilience of mangrove forests to hurricanes

The present study evaluates how a prolonged artificial flooding regime in impounded mangrove forests influences the regeneration after medium-sized forest destruction created by two hurricanes in 2004 in the Indian River Lagoon, Florida, USA. Disturbance patterns, forest structure, and regeneration were investigated. We found disturbed areas, characterized by uprooted and snapped trees, and intact forests in close proximity. The canopy turnover was greater in forests in higher succession stages with median tree diameter at breast height of 7.6 ± 5.7 cm compared to the intact forest with 3.7 ± 1.2 cm. Larger trees with lower densities were more susceptible to hurricane damage. We observed that regeneration of the open patches was dominated by the flood-tolerant species Rhizophora mangle (89.9%) instead of the faster-growing pioneer species Laguncularia racemosa (7.0%). Some of the disturbed areas created by the hurricanes were not recolonized. The regeneration rate of the disturbed areas expressed by vegetation closure >50% differed between almost zero to 100% in three different impoundments. We concluded that the artificial flooding regime imposed by impoundment is the predominant selective force in the successive process according to the species composition. However, we were not able to detect the driving factors that prevented mangrove establishment in disturbed areas.