Trophic structure of fish assemblages in the lower Miranda River, Pantanal, Mato Grosso do Sul State, Brazil

Of a total of 101 fish species caught in the Lower Miranda River floodplain, 29 were omnivorous, 16 ichthyophagous, 12 herbivorous, 18 detritivorous, 8 zooplanktophagous, 7 insectivorous, 2 lepidophagous, 4 ichthyophagous/insectivorous and 4 zooplanktophagous/insectivorous. Almost half of the species belong to omnivorous and detritivorous trophic guilds. The same is not true when biomass is considered. The number of fish species by trophic guild didn't change along the year whereas the biomass changed significantly. The frequency of abundant fish species was not the same for the sampled environments.     

Influence of Tree Species Composition and Community Structure on Carbon Density in a Subtropical Forest

We assessed the impact of species composition and stand structure on the spatial variation of forest carbon density using data collected from a 4-ha plot in a subtropical forest in southern China. We found that 1) forest biomass carbon density significantly differed among communities, reflecting a significant effect of community structure and species composition on carbon accumulation; 2) soil organic carbon density increased whereas stand biomass carbon density decreased across communities, indicating that different mechanisms might account for the accumulation of stand biomass carbon and soil organic carbon in the subtropical forest; and 3) a small number of tree individuals of the medium- and large-diameter class contributed predominantly to biomass carbon accumulation in the community, whereas a large number of seedlings and saplings were responsible for a small proportion of the total forest carbon stock. These findings demonstrate that both biomass carbon and soil carbon density in the subtropical forest are sensitive to species composition and community structure, and that heterogeneity in species composition and stand structure should be taken into account to ensure accurate forest carbon accounting.     

Scent-Marking of Giant Otter in the Southern Pantanal, Brazil

Giant otters live in social groups, consisting of a mating pair and one or two litters. Groups are territorial and mark their territories often with scent-marks. Our objectives were to evaluate the frequencies of marking and over-marking according to the social status of the individuals and to define the different postures used during the marking. We observed four groups, totaling 25 individuals (five alpha males, four alpha females, seven adult females, one adult male and eight juveniles) with group size ranging between four and 13 individuals. The study was conducted between July 2006 and July 2007 in the Vermelho River and in a stretch of the Miranda River, in the Southern Pantanal. We observed the groups for a total of 2006 min and recorded 95 events of marking totaling 84.9 min. Time spent marking varied between groups and ranged from 4.3 to 44.7 min. The alpha males marked more frequently (62% of marking events, 55 min) than the alpha females (17% of marking events, 13.6 min). Of the 59 events of scent-marking by the alpha males, 32 over-marked the marks of other individuals from the group. Of the 16 events of scent-marking of the alpha females, five over-marked that of other females from the same group. When scent-marking, alpha males used the 'stepping' posture most frequently (63%), then 'fore-paw rubbing' (24%), 'latrine use' (7%), and 'body rubbing' (6%). Alpha females used the 'stepping' posture most frequently (65%), then 'latrine use' (19%) and 'fore-paw rubbing' (12%), with only one event of 'body rubbing' observed during marking. Subordinate females used the 'stepping' posture (76%) and 'latrine use' (24%) during marking. Scent-marking can play many roles in mammals and for giant otters, and the main roles appear to be communication of social and sexual status and territorial defense.     

Short-Term Temporal Changes in Tree Live Biomass in a Central Amazonian Forest, Brazil

We monitored seventy-two 1 ha permanent plots spread over 64 km² of terra firme forest at Reserva Ducke (Manaus, Amazonas, Brazil) over 2-yr intervals to assess the effects of a soil and topographic gradient on the rate of change in the aboveground tree live biomass (AGLB). AGLB increased significantly over the 2-yr intervals, exhibiting a mean rate of change of 1.65 Mg/ha/yr (bootstrapped 95% CI: 1.15, 2.79). The rate of change varied according to tree size class; understory and sub-canopy trees exhibited higher rates of change. Over the whole period, the rate of change was not related to soil or topographic features of the plots, but there was evidence that the relationships varied depending on the year of measurement. In the plots monitored between 2001 and 2003 we found a significant relationship between AGLB change and the soil textural gradient, but this relationship was not evident in plots monitored between 2002 and 2004. This suggests that both the temporal variation in the soil–biomass change relationship and the size structure of the forest need to be included in models of biomass change in Amazonia. We also noted that the rate of biomass change is sensitive to the equation used to estimate AGLB. Allometric models that incorporate wood-density data provide higher per plot AGLB estimates, but lower rates of change, suggesting that variations in floristic composition have important implications for carbon cycling in diverse tropical forests.
Abstract in Portuguese is available at http://www.blackwell-synergy.com/loi/btp .     

Rapid Recovery of Biomass, Species Richness, and Species Composition in a Forest Chronosequence in Northeastern Costa Rica

Secondary forests are a vital part of the tropical landscape, and their worldwide extent and importance continues to increase. Here, we present the largest chronosequence data set on forest succession in the wet tropics that includes both secondary and old-growth sites. We performed 0.1 ha vegetation inventories in 30 sites in northeastern Costa Rica, including seven old-growth forests and 23 secondary forests on former pastures, ranging from 10 to 42 yr. The secondary forest sites were formerly pasture for intervals of <1–25 yr. Aboveground biomass in secondary forests recovered rapidly, with sites already exhibiting values comparable to old growth after 21–30 yr, and biomass accumulation was not impacted by the length of time that a site was in pasture. Species richness reached old-growth levels in as little as 30 yr, although sites that were in pasture for > 10 yr had significantly lower species richness. Forest cover near the sites at the time of forest establishment did not significantly impact biomass or species richness, and the species composition of older secondary forest sites (>30 yr) converged with that of old growth. These results emphasize the resilience of tropical ecosystems in this region and the high conservation value of secondary forests.
     

塔里木河下游柽柳灌丛地上生物量估测

根据划分的柽柳灌丛大、中、小等级,在塔里木河下游英苏至喀尔达依区段进行地表采样、称重,采用统计相关法对柽柳年龄及地径关系进行分析,构建柽柳直立枝与单丛地上生物量估测模型,对模型精度进行检验,筛选最佳模型,并对模型估测值与实测值进行卡方检验。结果表明:(1)输水后柽柳新萌直立枝地径随年龄增加而增大,但输水前柽柳萌生直立枝的地径随年龄增加未呈现规律性变化。在地下水条件非一致性的干旱荒漠区,柽柳地径大小不能作为判断其年龄的依据。(2)根据柽柳标准枝和灌丛因子实测数据,用一元线性函数、幂函数、指数函数、对数函数4种函数进行柽柳直立枝生物量估测模型拟合结果表明,幂函数w=2.007(d2 h)0.837估测模型最优,其总体估测精度达89.92%。(3)以冠幅面积单变量、冠幅周长与丛高双变量构建的柽柳单丛生物量估测模型的精度分别为78.95%和80.09%。(4)以全收获法实测数据为真值对估测模型进行精度检验,柽柳冠幅面积为自变量模型的估测精度为80.54%,柽柳冠幅周长和丛高估测模型的精度为66.85%。(5)对柽柳单株及单丛生物量模型估测值与实测值进行卡方检验结果表明两者之间无显著差异。研究认为,由于柽柳冠幅在高分辨遥感数据上容易获取,柽柳冠幅面积估测模型在传统生物量估测和遥感生物量估测都具有实用价值。     

Length–weight relationships and length at first maturity for fish species in the upper Miranda River,southern Pantanal wetland,Brazil

Length–weight relationships (LWR) were estimated for 17 species and total length at first maturity (L50) for three species of freshwater fishes from the Miranda River, southern Pantanal, Brazil. The b values were compared for some species in the Paraguay River basin with the northern (Cuiabá River) part of the basin; differences in length–weight relationships were significantly different for Pseudoplatystoma corruscans, P. reticulatum (syn. P. fasciatum). First references on L50 and LWR are presented for two and eight fish species, respectively, as well as the new maximum total length for two species.     

江西武夷山河岸带阔叶林群落的物种组成和多样性分析

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

Fire as a Recurrent Event in Tropical Forests of the Eastern Amazon: Effects on Forest Structure,Biomass, and Species Composition1

The effects of fire on forest structure and composition were studied in a severely fire-impacted landscape in the eastern Amazon. Extensive sampling of area forests was used to compare structure and compositional differences between burned and unburned forest stands. Burned forests were extremely heterogeneous, with substantial variation in forest structure and fire damage recorded over distances of <50 m. Unburned forest patches occurred within burned areas, but accounted for only six percent of the sample area. Canopy cover, living biomass, and living adult stem densities decreased with increasing fire inrensiry / frequency, and were as low as 10–30 percent of unburned forest values. Even light burns removed >70 percent of the sapling and vine populations. Pioneer abundance increased dramatically with burn intensity, with pioneers dominating the understory in severely damaged areas. Species richness was inversely related to burn severity, but no clear pattern of species selection was observed. Fire appears to be a cyclical event in the study region: <30 percent of the burned forest sample had been subjected to only one burn. Based on estimated solar radiation intensities, burning substantially increases fire susceptibility of forests. At least 50 percent of the total area of all burned forests is predicted to become flammable within 16 rainless days, as opposed to only 4 percent of the unburned forest. In heavily burned forest subjected to recurrent fires, 95 percent of the area is predicted to become flammable in <9 rain-free days. As a recurrent disturbance phenomenon, fire shows unparalleled potential to impoverish and alter the forests of the eastern Amazon.     

Allometric Models for Tree Volume and Total Aboveground Biomass in a Tropical Humid Forest in Costa Rica1

Allometric equations for the estimation of tree volume and aboveground biomass in a tropical humid forest were developed based on direct measurements of 19 individuals of seven tree species in Northern Costa Rica. The volume and the biomass of the stems represented about two‐thirds of the total volume and total aboveground biomass, respectively. The average stem volume varied between 4 and 11 Mg/tree and the average total aboveground biomass ranged from 4 to 10 mg/tree. The mean specific gravity of the sampled trees was 0.62 ± 0.06 (g/cm³). The average biomass expansion factor was 1.6 ± 0.2. The best‐fit equations for stem and total volume were of logarithmic form, with diameter at breast height (R²= 0.66 ? 0.81) as an independent variable. The best‐fit equations for total aboveground biomass that were based on combinations of diameter at breast height, and total and commercial height as independent variables had R² values between 0.77 and 0.87. Models recommended for estimating total aboveground biomass are based on diameter at breast height, because the simplicity of these models is advantageous. This variable is easy to measure accurately in the field and is the most common variable recorded in forest inventories. Two widely used models in literature tend to underestimate aboveground biomass in large trees. In contrast, the models developed in this study accurately estimate the total aboveground biomass in these trees.     

Impacts of Wildfire on the Composition and Structure of Riparian Forests in Southern California

In southern California, wildfire is a ubiquitous agent shaping plant communities. Although fire impacts have been widely studied in chaparral-covered uplands, few data are available regarding fire and riparian vegetation. This study provides an example of the impact of a severe fire on riparian habitat. Plant species found in southern California gallery forests are typically adapted to maintaining populations following flood disturbances; we seek to determine whether structural and compositional changes following fire here demonstrate a similar quasi-equilibrium response. We sampled 65 quadrats on 11 transects along two streams in the Los Padres National Forest to characterize tree species size–class distributions before and after the 2002 Wolf Fire. We tested whether species exhibited differential patterns of survivorship and regeneration following the fire, and also tested for spatial variability in mortality within the floodplain. Alnus rhombifolia dominated the pre-fire forest, but experienced severe mortality in the fire and showed very limited resprouting after 3 years. Other prominent taxa (Populus, Salix, Quercus spp.) also lost considerable standing basal area, but had substantially greater rates of resprouting, resulting in a dramatically altered post-fire vegetation composition and structure. Fire impacts did not vary with landform position, leading to a distinctive homogenizing disturbance that contrasts with the spatially zoned and relatively stabilizing compositional influence that flood events have in this same riparian setting.     

Possible Negative Effect of General Flowering on Tree Growth and Aboveground Biomass Increment in a Bornean Tropical Rain Forest

We tested the effect of general flowering (GF), community‐wide masting, and drought stress on current‐year tree diameter growth and aboveground biomass increment (ABI). General flowering but not drought had a marginally significant negative effect on tree growth and ABI at the community level. Analyses of dominant species clarified this pattern.     

Wood Specific Gravity Variations and Biomass of Central African Tree Species: The Simple Choice of the Outer Wood

Context

Wood specific gravity is a key element in tropical forest ecology. It integrates many aspects of tree mechanical properties and functioning and is an important predictor of tree biomass. Wood specific gravity varies widely among and within species and also within individual trees. Notably, contrasted patterns of radial variation of wood specific gravity have been demonstrated and related to regeneration guilds (light demanding vs. shade-bearing). However, although being repeatedly invoked as a potential source of error when estimating the biomass of trees, both intraspecific and radial variations remain little studied. In this study we characterized detailed pith-to-bark wood specific gravity profiles among contrasted species prominently contributing to the biomass of the forest, i.e., the dominant species, and we quantified the consequences of such variations on the biomass.

Methods

Radial profiles of wood density at 8% moisture content were compiled for 14 dominant species in the Democratic Republic of Congo, adapting a unique 3D X-ray scanning technique at very high spatial resolution on core samples. Mean wood density estimates were validated by water displacement measurements. Wood density profiles were converted to wood specific gravity and linear mixed models were used to decompose the radial variance. Potential errors in biomass estimation were assessed by comparing the biomass estimated from the wood specific gravity measured from pith-to-bark profiles, from global repositories, and from partial information (outer wood or inner wood).

Results

Wood specific gravity profiles from pith-to-bark presented positive, neutral and negative trends. Positive trends mainly characterized light-demanding species, increasing up to 1.8 g.cm^-3 per meter for Piptadeniastrum africanum, and negative trends characterized shade-bearing species, decreasing up to 1 g.cm^-3 per meter for Strombosia pustulata. The linear mixed model showed the greater part of wood specific gravity variance was explained by species only (45%) followed by a redundant part between species and regeneration guilds (36%). Despite substantial variation in wood specific gravity profiles among species and regeneration guilds, we found that values from the outer wood were strongly correlated to values from the whole profile, without any significant bias. In addition, we found that wood specific gravity from the DRYAD global repository may strongly differ depending on the species (up to 40% for Dialium pachyphyllum).

Main Conclusion

Therefore, when estimating forest biomass in specific sites, we recommend the systematic collection of outer wood samples on dominant species. This should prevent the main errors in biomass estimations resulting from wood specific gravity and allow for the collection of new information to explore the intraspecific variation of mechanical properties of trees.     

南亚热带常绿阔叶林优势种群的生物量与生物量增量

粘木种群的生物量为７０．１４ｔ／ｈｍ２,生物量增量为２．３２ｔｈｍ２ａ－１。其总生物量的９０％以上分布在ｄ≥２０ｃｍ的大树,仅有０．０４％～０．０５％分布在ｄ＜１０ｃｍ的小树。在各器官的分配是：树干为６５％,根为２５％,枝为１１％,而叶仅占有２％。粘木的平均径向增长为０．３５ｃｍ／ａ。应用树干解析法和形率法估算树干的生物量,两者的结果差别不大。但形率法则既省力省时,又较方便。粘木的形率为０．７１。     

Bird Species Sensitivity in a Fragmented Landscape of the Atlantic Forest in Southern Brazil1

I tested whether terrestrial/understory habits, large body sizes, low tolerance to edge or to matrix habitat, and food/habitat specialization are characteristics of the most vulnerable bird species based on point counts conducted in 14 forest fragments in northern Paraná, southern region of the Brazilian Atlantic forest. In addition, the sensitivity level of each bird species to forest fragmentation in northern Paraná (high, medium, and low) was compared to the Viçosa region, another fragmented landscape of the Atlantic forest. Contrary to expectations, large body size and terrestrial/understory habits were not features clearly related to high sensitivity to forest fragmentation; but species with tolerance to edge did have lower sensitivity. I found also that specialized habitat/food were not good predictors of extinctions; the most specialized guilds, bamboo and vine‐tangle insectivores and trunk and twig insectivores, had a high number of species with low sensitivity. Patterns of sensitivity were compared for 75 bird species that occurred in both northern Paraná and Viçosa; higher incongruence occurred for 14 and 7 species considered as highly sensitive in Viçosa but were of medium or low sensitivity, respectively, in northern Paraná. These differences may occur because sensitivity to habitat fragmentation may vary from the center to the periphery of a species' geographic range. Geographic variation in patterns of sensitivity to forest fragmentation may be important for conservation planning.     

Temporal Changes in Tree Species and Trait Composition in a Cyclone-prone Pacific Dipterocarp Forest

Our understanding of the effects of tropical cyclones on species composition and dynamics of forest communities is mainly derived from studies that have considered single cyclonic events. Here we examined changes in the tree species and functional trait composition in an 8-ha Dipterocarp forest at Palanan in the northeastern Philippines that is subject to a high frequency of cyclonic disturbance (1–4 cyclones annually). The plot has been censused four times over a 16-year interval allowing us to consider the medium-term forest dynamics in response to repeated cyclones. We hypothesized that as the forest community in Palanan has been selected under frequent disturbance by cyclones, it should show little functional change across the census intervals. We analyzed changes in demography, species composition, and community-weighted functional traits (specific leaf area, leaf area, wood density, and specific growth rate) across the censuses and compared these against cyclone intensities during the census intervals. Demographic changes across census years suggest that the community responded to cyclonic disturbances through substantial turnover in the small- and medium-size individuals, and that there has been an increase in plot-level stem density and basal area across the measured period. Trait compositional changes from 1994 to 2010 were mostly small, but indicate a shift towards species with larger leaves and faster growth rates—traits that are associated with fast recovery after disturbance. These changes all coincide with a large intense cyclone between the second and third censuses, suggesting that cyclone strength, more than cyclone frequency, affects this forest.     

Aboveground Carbon Storage and Its Links to Stand Structure,Tree Diversity and Floristic Composition in South-Eastern Tanzania

African savannas and dry forests represent a large, but poorly quantified store of biomass carbon and biodiversity. Improving this information is hindered by a lack of recent forest inventories, which are necessary for calibrating earth observation data and for evaluating the relationship between carbon stocks and tree diversity in the context of forest conservation (for example, REDD+). Here, we present new inventory data from south-eastern Tanzania, comprising more than 15,000 trees at 25 locations located across a gradient of aboveground woody carbon (AGC) stocks. We find that larger trees disproportionately contribute to AGC, with the largest 3.7% of individuals containing half the carbon. Tree species diversity and carbon stocks were positively related, implying a potential functional relationship between the two, and a ‘win–win’ scenario for conservation; however, lower biomass areas also contain diverse species assemblages meaning that carbon-oriented conservation may miss important areas of biodiversity. Despite these variations, we find that total tree abundance and biomass is skewed towards a few locally dominant species, with eight and nine species (5.7% of the total) accounting for over half the total measured trees and carbon, respectively. This finding implies that carbon production in these areas is channelled through a small number of relatively abundant species. Our results provide key insights into the structure and functioning of these heterogeneous ecosystems and indicate the need for novel strategies for future measurement and monitoring of carbon stocks and biodiversity, including the use for larger plots to capture spatial variations in large tree density and AGC stocks, and to allow the calibration of earth observation data.     

鄂西南天然林主要乔木树种物种组成及林分空间结构动态变化研究

该研究以鄂西南木林子国家级自然保护区内天然林为研究对象,以森林内胸径≥5 cm的乔木个体为具体分析对象,通过乔木树种重要值及其角尺度、大小比、混交度等林分空间结构参数的一元分布,阐述林分空间分布格局、大小分化程度、林木混交程度及变化,并通过分析林分空间结构参数的二元分布,探究各参数之间的联系,揭示5年间其林分空间结构特...     

Species Composition,Physiognomy and Plant Diversity of the Tropical Montane Evergreen Broad-leaved Forest in Southern Yunnan

Species composition, physiognomy and plant diversity of the less known tropical montane forests in southern Yunnan were studied based on the data from 15 sampling plots in three sites. These forests are mainly dominated by the families Theaceae, Fagaceae, Lauraceae and Euphorbiaceae in floristic composition, and dominated by evergreen phanerophytes with mesophyllous leaves. These forests are similar to lower montane rain forests in equatorial southeastern Asia in floristic composition and altitudinal distributions, but differ in physiognomy by having few epiphytes, but more lianas and more plants with compound leaves. These differences could be due to strongly seasonal climate and so-called mass elevation effect in southern Yunnan. They also differ from the tropical seasonal rain forests at lower altitudes in southern Yunnan by having conspicuously lower species richness, few epiphytes, fewer mega-mesophanerophytes, more abundant micro-nanophanerophytes and hemicryptophytes and more plants with microphyllous leaves. It is suggested that these forests could be termed tropical montane evergreen broad-leaved forests, and be a vegetation type from the northern margin of mainland southeastern Asia controlled by a strongly seasonal climate.     

Distribution of Herbaceous Species in the Soil Seed Bank of a Flood Seasonality Area,Northern Pantanal,Brazil

To identify factors affecting the spatial distribution of soil seed banks of herbaceous species in the Pantanal floodplain, Brazil, the aims of this study were: to characterize the seed bank in terms of the abundance, richness and composition of germinated seeds; to relate these characteristics to flood duration, elevation, chemical and physical properties of the soil and to examine the seed bank’s spatial pattern. Soil samples were collected at 14 points and were then placed in a greenhouse to allow germination to occur. Each sample point had the flood level monitored, the elevation measured and the soil properties identified. A total of 1710 seedlings from 26 species were recorded, of which Echinodorus tenelus was the most abundant (24.9%). Cyperaceae and Poaceae were the richest floristic families (5 species each), with Alismataceae the most represented in terms of number of individuals (36% of the total). Duration of flooding plays an important role in determining Pantanal soil seed banks. The flood pulse influences the abundance (r = 0.79; P = 0.006; partial), richness (r = 0.61; P = 0.02; partial) and composition of the soil seed bank (Pillai trace = 0.552; P = 0.027), carrying the seeds to areas where the duration of flood is longer. Except for aluminium, the soil characteristics expressed by the first principal component of PCA exert indirect positive effects on the seed bank. This is because this component was correlated with the duration of inundation (r = 0.76). Elevation and the toxic effect of aluminium do not vary sufficiently to be able to influence seed bank characteristics. The correlograms show that soil seed banks have no discernible spatial pattern, even though most species are dispersed hydrochorically. This suggests that, at the scale of the study, the tendency for flooding to cause homogeneous dispersion has no influence on seed‐bank spatial structure, because of the complexity of flood‐plain geomorphology. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)