Bryophyte Species Richness and Composition along an Altitudinal Gradient in Gongga Mountain,China

An investigation of terrestrial bryophyte species diversity and community structure along an altitudinal gradient from 2,001 to 4,221 m a.s.l. in Gongga Mountain in Sichuan, China was carried out in June 2010. Factors which might affect bryophyte species composition and diversity, including climate, elevation, slope, depth of litter, vegetation type, soil pH and soil Eh, were examined to understand the altitudinal feature of bryophyte distribution. A total of 14 representative elevations were chosen along an altitudinal gradient, with study sites at each elevation chosen according to habitat type (forests, grasslands) and accessibility. At each elevation, three 100 m × 2 m transects that are 50 m apart were set along the contour line, and three 50 cm × 50 cm quadrats were set along each transect at an interval of 30 m. Species diversity, cover, biomass, and thickness of terrestrial bryophytes were examined. A total of 165 species, including 42 liverworts and 123 mosses, are recorded in Gongga mountain. Ground bryophyte species richness does not show any clear elevation trend. The terrestrial bryophyte cover increases with elevation. The terrestrial bryophyte biomass and thickness display a clear humped relationship with the elevation, with the maximum around 3,758 m. At this altitude, biomass is 700.3 g m⁻² and the maximum thickness is 8 cm. Bryophyte distribution is primarily associated with the depth of litter, the air temperature and the precipitation. Further studies are necessary to include other epiphytes types and vascular vegetation in a larger altitudinal range.     

Gene Regulatory Variation Mediates Flowering Responses to Vernalization along an Altitudinal Gradient in Arabidopsis

Steep environmental gradients provide ideal settings for studies of potentially adaptive phenotypic and genetic variation in plants. The accurate timing of flowering is crucial for reproductive success and is regulated by several pathways, including the vernalization pathway. Among the numerous genes known to enable flowering in response to vernalization, the most prominent is FLOWERING LOCUS C (FLC). FLC and other genes of the vernalization pathway vary extensively among natural populations and are thus candidates for the adaptation of flowering time to environmental gradients such as altitude. We used 15 natural Arabidopsis (Arabidopsis thaliana) genotypes originating from an altitudinal gradient (800–2,700 m above sea level) in the Swiss Alps to test whether flowering time correlated with altitude under different vernalization scenarios. Additionally, we measured the expression of 12 genes of the vernalization pathway and its downstream targets. Flowering time correlated with altitude in a nonlinear manner for vernalized plants. Flowering time could be explained by the expression and regulation of the vernalization pathway, most notably by AGAMOUS LIKE19 (AGL19), FLOWERING LOCUS T (FT), and FLC. The expression of AGL19, FT, and VERNALIZATION INSENSITIVE3 was associated with altitude, and the regulation of MADS AFFECTING FLOWERING2 (MAF2) and MAF3 differed between low- and high-altitude genotypes. In conclusion, we found clinal variation across an altitudinal gradient both in flowering time and the expression and regulation of genes in the flowering time control network, often independent of FLC, suggesting that the timing of flowering may contribute to altitudinal adaptation.Environmental gradients, such as temperature or water availability, provide an ideal setting to study how species adapt to contrasting environmental scenarios (Reich et al., 2003; Keller et al., 2013). Many studies have shown that phenotypic plant traits such as leaf number, allocation to reproductive biomass, and height change along environmental gradients (Etterson, 2004; Leger and Rice, 2007; Fischer et al., 2011), and some studies could correlate environmental clines to changes in allelic frequencies at specific candidate genes (Manel et al., 2010; Poncet et al., 2010; Fischer et al., 2013).Although allelic variation at genes with major effects may explain variation in some phenotypes, fine-tuning of other quantitative traits along an environmental gradient may require an adjustment of larger regulatory networks (Whitehead and Crawford, 2006; Hodgins-Davis and Townsend, 2009; Hodgins et al., 2013). In Arabidopsis (Arabidopsis thaliana), numerous genetic pathways have been studied extensively, mainly using laboratory accessions (Shinozaki and Yamaguchi-Shinozaki, 2007; Wellmer and Riechmann, 2010; Ó’Maoiléidigh et al., 2014). However, how consistently such pathways are expressed in natural populations, and how they respond to different environmental conditions, often remains unclear. Studying the expression of genetic pathways in natural genotypes originating from an environmental cline under a variety of climatic scenarios provides an ideal approach to understanding how plants can adapt to contrasting environments along a climatic gradient.Across altitudes, environmental gradients are particularly steep: climatic conditions, including temperature, solar radiation, and precipitation, may change dramatically on a small geographic scale (Körner, 2007), while daylength and other factors remain constant. Many phenotypic traits, such as height, total seed weight, leaf size, and allocation to vegetative reproduction, have been found to change along altitudinal gradients in plants (Byars et al., 2007; Gonzalo-Turpin and Hazard, 2009; Fischer et al., 2011). Among these, the timing of flowering (i.e. the transition from vegetative growth to the reproductive phase) is a key developmental phase transition in seasonal alpine environments, as its accuracy is crucial for reproductive success: too-early flowering increases the risk of encountering detrimental frost (Kollas et al., 2013), whereas time for seed maturation may run out if flowering starts too late (Inouye and Wielgolaski, 2003; Chuine, 2010). These contrasting selective pressures may change along an altitudinal gradient, where the vegetation period becomes shorter with increasing altitude.In Arabidopsis, an annual weed native to Eurasia and northern Africa, two different life cycles have been described (Koornneef et al., 2004; Alonso-Blanco et al., 2009): summer annuals germinate and flower within one growing season and do not require winter to initiate flowering; winter annuals germinate usually in autumn, overwinter as vegetative rosettes, and flower in the following spring. Accessions expressing a winter-annual life cycle need vernalization (a prolonged cold period) in order to initiate flowering; otherwise, they remain in a vegetative rosette stage for an extended period of time.On the molecular level, the transition to flowering is among the best-studied processes in plants (Wellmer and Riechmann, 2010; Andrés and Coupland, 2012), and in Arabidopsis, several genetic pathways controlling flowering are known. Signals from the vernalization pathway, photoperiod pathway, autonomous pathway, GA pathway, and plant age all contribute to ensuring the correct timing of flowering (Ehrenreich et al., 2009; Wellmer and Riechmann, 2010; Srikanth and Schmid, 2011). Within the vernalization pathway, a number of key players have been identified (Andrés and Coupland, 2012; Schmitz and Amasino, 2012; Song et al., 2012; Zografos and Sung, 2012). In winter annuals, a functional FRIGIDA (FRI) allele is required to activate FLOWERING LOCUS C (FLC). FLC strongly suppresses the flowering promoters FLOWERING LOCUS T (FT) and AGAMOUS LIKE20 (AGL20; also referred to as SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1) and thus inhibits flowering. During vernalization, VERNALIZATION INSENSITIVE3 (VIN3) represses FLC, and the repressed state is maintained in subsequent warm periods by epigenetic silencing (Crevillén and Dean, 2011; Zografos and Sung, 2012), allowing FT, AGL20, and, through positive feedback with AGL20, AGL24 (Liu et al., 2008) to initiate flowering. Many natural populations and most laboratory accessions, among them Columbia-0 (Col-0), carry nonfunctional FRI or FLC alleles and thus respond only weakly to vernalization, resulting in fast flowering, summer-annual life cycles (Johanson et al., 2000; Gazzani et al., 2003; Shindo et al., 2005).In addition to the well-studied FLC branch of the vernalization pathway, FLC-independent components of the vernalization response have been identified. For example, AGL19 has been found to promote flowering following vernalization without interacting with FLC (Schönrock et al., 2006), and relatives of FLC, the MADS AFFECTING FLOWERING genes (MAF1–MAF5; MAF1 is also referred to as FLOWERING LOCUS M [FLM]; De Bodt et al., 2003), have been shown to inhibit flowering in a similar way to FLC (Ratcliffe et al., 2003; Scortecci et al., 2003; Werner et al., 2005; Sung et al., 2006; Gu et al., 2013). Genes MAF2 to MAF5 (Ratcliffe et al., 2003) are arranged in a tandem gene array and vary extensively among natural populations (Caicedo et al., 2009; Rosloski et al., 2010), and several recent studies have associated this polymorphic region with natural variation in flowering time (Salomé et al., 2011; Silady et al., 2011; Lasky et al., 2012; Fournier-Level et al., 2013; Grillo et al., 2013), making these genes interesting candidates for studying associations between flowering time and ecological parameters.Associating genetic variation at a single gene with latitude or altitude has often proven to be difficult (Shindo et al., 2005; Stinchcombe et al., 2005; Méndez-Vigo et al., 2011), although Caicedo et al. (2004) found evidence for epistatic interactions between FRI and FLC alleles associated with latitude. Interestingly, some recent studies suggest that regulatory processes within the vernalization pathway may contribute to natural phenotypic variability (Shindo et al., 2006; Strange et al., 2011). Overall, the response to vernalization appears to be a complex process in natural populations, potentially involving epigenetic regulation of a number of genes. Therefore, to gain a better understanding of the involvement of this complex genetic network in the response to ecological parameters, it is essential to study multiple interacting genes of the vernalization pathway simultaneously.Here, we used 15 natural Arabidopsis genotypes originating from an altitudinal cline (800–2,700 m) in the Swiss Alps to study the associations between vernalization, flowering initiation, gene expression and regulation, and altitude. Importantly, all genotypes originated from a restricted geographic range; thus, confounding effects such as differences in daylength, as found along latitudinal clines, can be excluded. We measured flowering time and the expression of 12 genes of the vernalization pathway under different vernalization scenarios to assess whether the response to vernalization is associated with altitude. In particular, we tested the hypotheses that (1) flowering time correlates with altitude; (2) genotypes from high altitudes need longer vernalization periods to initiate flowering reliably; (3) gene expression and regulation of the vernalization pathway can explain flowering time; (4) gene expression and regulation of the vernalization pathway is associated with altitude; and (5) FLC-independent branches of the vernalization pathway are important for initiating flowering and, thus, for altitudinal adaptation in natural populations.     

Supercooling along an Altitudinal Gradient in Espeletia schultzii, a Caulescent Giant Rosette Species

Rada, F., Goldstein, G., Azocar, A. and Torres, F. 1987. Supercoolingalong an altitudinal gradient in Espeletia schultzii, a caulescentgiant rosette species.—J. exp. Bot. 38: 491–497. Tropical high Andes plants may be exposed to sub-zero temperaturesany night of the year. These plants have to rely on mechanismswhich protect them from these environmental conditions but atthe same time allow their growth and development. Supercoolinghas been found to be the principal avoidance mechanism in leavesof the caulescent giant rosette genus Espeletia in the Andes.We report here the differences in supercooling capacity andcold injury in several Espeletia schultzii populations growingalong an altitudinal gradient. The relationships between supercooling,water potential and leaf anatomy were also investigated. Thesupercooling capacity increased and injury temperature decreasedfrom lower to higher elevation populations. These changes maybe explained in terms of physiological, morphological and anatomicalcharacteristics of the leaves. Key words: Espeletia schultzii, supercooling, freezing avoidance mechanisms     

Species Richness Pattern along Altitudinal Gradient in Central European Beech Forests

The unimodal species richness-altitude distribution pattern seems to be universal. To investigate the validity of this phenomenon in homogeneous substrate and vegetation conditions, we sampled beech-dominated forests in five volcanic mountain ranges in the Western Carpathians. European beech (Fagus sylvatica L.) formed monodominant closed-canopy stands at altitudes from 300 to 1,200 m. Along this gradient, the influence of beech on understory plant species richness was expected to be strong and uniform. The shape of the species richness-altitude relationship was analyzed for three datasets: herb layer, shrub layer, and both layers merged together. Contrary to prediction, the studied species richness-altitude relationship was inversely unimodal, with a minimum at intermediate altitudes. Quadratic regression models were statistically significant for all three datasets (P<0.001) and the explained variability ranged from 12 % to 20 %. The possible explanation for the observed pattern is twofold. In the central part of the altitudinal gradient, low species richness is due to strong competition by monodominant beech with accumulation of leaf litter and uptake soil resources, mainly water. This influence is somewhat released towards the margins of the gradient. Secondly, the species pool from the neighbouring communities increases species richness only in the lower parts of the altitudinal gradient.     

No Evidence of Complementary Water Use along a Plant Species Richness Gradient in Temperate Experimental Grasslands

Niche complementarity in resource use has been proposed as a key mechanism to explain the positive effects of increasing plant species richness on ecosystem processes, in particular on primary productivity. Since hardly any information is available for niche complementarity in water use, we tested the effects of plant diversity on spatial and temporal complementarity in water uptake in experimental grasslands by using stable water isotopes. We hypothesized that water uptake from deeper soil depths increases in more diverse compared to low diverse plant species mixtures. We labeled soil water in 8 cm (with ¹⁸O) and 28 cm depth (with ²H) three times during the 2011 growing season in 40 temperate grassland communities of varying species richness (2, 4, 8 and 16 species) and functional group number and composition (legumes, grasses, tall herbs, small herbs). Stable isotope analyses of xylem and soil water allowed identifying the preferential depth of water uptake. Higher enrichment in ¹⁸O of xylem water than in ²H suggested that the main water uptake was in the upper soil layer. Furthermore, our results revealed no differences in root water uptake among communities with different species richness, different number of functional groups or with time. Thus, our results do not support the hypothesis of increased complementarity in water use in more diverse than in less diverse communities of temperate grassland species.     

Variation and Sexual Dimorphism of Body Size in the Plateau Brown Frog along an Altitudinal Gradient

Variation in body size and sexual size dimorphism(SSD) can have important consequences for animal ecology, behavior, population dynamics and the evolution of life-history traits. Organisms are expected to be larger in colder climate(i.e., Bergmann's rule) and SSD varies with body size(i.e., Rensch's rule). However, the underlying mechanisms are still elusive. The plateau brown frog(Rana kukunoris), a medium-sized anuran species with femalebiased SSD, is endemic to the Qinghai-Tibetan Plateau(QTP). From 1797 m(Maoxiang'ping) to 3453 m(Heihe'qiao) in the eastern margin of the QTP, we surveyed 10 populations of R. kukunoris and collected phalanges and snout vent length(SVL) data for 258 adult individuals(199 males versus 59 females). Based on these data, we explored how body size and SSD varying along the altitudinal gradient and examined the corresponding effects of temperature. We found body size to be larger at higher altitude for males but not for females, with likely effects from the temperature on the variation in male body size. Sex differences in growth rates may be the main cause of the variation in SSD. Our results suggested that only males follow the Bergmann's rule and variation in SSD of R. kukunoris do not support the Rensch's rule and its inverse. Therefore, the variations of body size can be different between sexes and the applicability of both Bergmann's rule and Rensch's rule should depend on species and environment where they live.     

Assessing Intraspecific Variation in Effective Dispersal Along an Altitudinal Gradient: A Test in Two Mediterranean High-Mountain Plants

Background

Plant recruitment depends among other factors on environmental conditions and their variation at different spatial scales. Characterizing dispersal in contrasting environments may thus be necessary to understand natural intraspecific variation in the processes underlying recruitment. Silene ciliata and Armeria caespitosa are two representative species of cryophilic pastures above the tree line in Mediterranean high mountains. No explicit estimations of dispersal kernels have been made so far for these or other high-mountain plants. Such data could help to predict their dispersal and recruitment patterns in a context of changing environments under ongoing global warming.

Methods

We used an inverse modelling approach to analyse effective seed dispersal patterns in five populations of both Silene ciliata and Armeria caespitosa along an altitudinal gradient in Sierra de Guadarrama (Madrid, Spain). We considered four commonly employed two-dimensional seedling dispersal kernels exponential-power, 2Dt, WALD and log-normal.

Key Results

No single kernel function provided the best fit across all populations, although estimated mean dispersal distances were short (<1 m) in all cases. S. ciliata did not exhibit significant among-population variation in mean dispersal distance, whereas significant differences in mean dispersal distance were found in A. caespitosa. Both S. ciliata and A. caespitosa exhibited among-population variation in the fecundity parameter and lacked significant variation in kernel shape.

Conclusions

This study illustrates the complexity of intraspecific variation in the processes underlying recruitment, showing that effective dispersal kernels can remain relatively invariant across populations within particular species, even if there are strong variations in demographic structure and/or physical environment among populations, while the invariant dispersal assumption may not hold for other species in the same environment. Our results call for a case-by-case analysis in a wider range of plant taxa and environments to assess the prevalence and magnitude of intraspecific dispersal variation.     

沿海拔梯度武夷山3种典型森林凋落物及养分归还动态

为了解武夷山森林凋落物量和养分归还特征,对武夷山3个海拔典型森林的凋落物量和养分动态开展连续3年的监测。结果表明,常绿阔叶林(645 m)、针阔混交林(1 028 m)和针叶林(1 442 m)的凋落物总量分别为471.25、453.77和409.84 g/m~2,森林凋落物总量随海拔升高呈减少的趋势。武夷山3种典型森林的凋落物总量具有明显的季节变化,均呈双峰型,但常绿阔叶林与针阔混交林和针叶林的凋落物总量峰值和次峰值出现时间近似相反。3种典型森林凋落物中落叶占绝对优势(78.1%～87.6%),落枝和其他组分较少。武夷山3种典型森林凋落物的养分年归还量均表现为C N K P,且养分归还总量随海拔升高而减少。常绿阔叶林的凋落物量和养分归还量较高,可能与环境条件和植被特征相关。这为中亚热带森林生态系统养分循环和森林碳循环机理研究提供了理论依据。     

Patterns of Genetic Variation across Altitude in Three Plant Species of Semi-Dry Grasslands

Background

Environmental gradients caused by altitudinal gradients may affect genetic variation within and among plant populations and inbreeding within populations. Populations in the upper range periphery of a species may be important source populations for range shifts to higher altitude in response to climate change. In this study we investigate patterns of population genetic variation at upper peripheral and lower more central altitudes in three common plant species of semi-dry grasslands in montane landscapes.

Methodology/Principal Findings

In Briza media, Trifolium montanum and Ranunculus bulbosus genetic diversity, inbreeding and genetic relatedness of individuals within populations and genetic differentiation among populations was characterized using AFLP markers. Populations were sampled in the Swiss Alps at 1800 (upper periphery of the study organisms) and at 1200 m a.s.l. Genetic diversity was not affected by altitude and only in B. media inbreeding was greater at higher altitudes. Genetic differentiation was slightly greater among populations at higher altitudes in B. media and individuals within populations were more related to each other compared to individuals in lower altitude populations. A similar but less strong pattern of differentiation and relatedness was observed in T. montanum, while in R. bulbosus there was no effect of altitude. Estimations of population size and isolation of populations were similar, both at higher and lower altitudes.

Conclusions/Significance

Our results suggest that altitude does not affect genetic diversity in the grassland species under study. Genetic differentiation of populations increased only slightly at higher elevation, probably due to extensive (historic) gene flow among altitudes. Potentially pre-adapted genes might therefore spread easily across altitudes. Our study indicates that populations at the upper periphery are not genetically depauperate or isolated and thus may be important source populations for migration under climate change.     

Predictive Mapping of Species Richness and Plant Species' Distributions of a Peruvian Fog Oasis Along an Altitudinal Gradient

Tropical arid to semi‐arid ecosystems are nearly as diverse as more humid forests and occupy large parts of the tropics. In comparison, however, they are vastly understudied. For instance, fog precipitation alone supports a unique vegetation formation, locally termed lomas, on coastal mountains in the Peruvian desert. To effectively protect these highly endemic and threatened ecosystems, we must increase our understanding of their diversity patterns in relation to environmental factors. Consequently, we recorded all vascular species from 100 random 4 × 4 m plots on the fog‐exposed southern slope of the mountain Mongón. We used topographic and remotely sensed covariates in statistical models to generate spatial predictions of alpha diversity and plant species' distribution probabilities. Altitude was the most important predictor in all models and may represent fog moisture levels. Other significant covariates in the models most likely refer also to water availability but on a finer spatial scale. Additionally, model‐based clustering revealed five altitudinal vegetation zones. This study contributes to a better spatial understanding of the biodiversity and spatial arrangement of vegetation belts of the largely unknown but highly unique lomas formations. Furthermore, mapping species richness and plant species' distributions could support a long‐needed lomas strategic conservation scheme.     

The Effect of Positive Interactions on Temporal Turnover of Community Composition along an Environmental Gradient

It has been demonstrated that the interplay between negative and positive interactions simultaneously shapes community structure and composition. However, few studies have attempted to examine the effect of facilitation on compositional changes in communities through time. Additionally, due to the difficulties in collecting the long-term data, it would be useful to indicate the rate of temporal turnover using a readily obtainable metric. Using an individual-based model incorporating plant strategies, we examined the role of facilitation on the temporal turnover of communities located at different positions along an environmental gradient for three model scenarios: CM without facilitation; CFM-U, a unimodal relationship between facilitation and environmental severity; and CFM-L, a positively linear relationship between facilitation and environmental severity. Our results demonstrated that facilitation could increase, decrease or have no remarkable effect on temporal turnover. The specific outcome depended on the location of the focal community across the environmental gradient and the model employed. Compared with CM, the inclusion of positive interactions (i.e. CFM-U and CFM-L), at intermediate environmental stress levels (such as S = 0.7 and 0.8) resulted in lower Bray-Curtis similarity values; at other severity levels, facilitation slowed down (such as S = 0.3 and 0.4 at low to medium stress levels, and S = 0.9 at high stress levels) or had only a subtle effect (such as at S = 0.1) on temporal turnover. We also found that the coefficient of variation (CV) in species abundances and the rate of temporal variability showed a significant quadratic relationship. Our theoretical analysis contributes to the understanding of factors driving temporal turnover in biotic communities, and presents a potential metric (i.e. CV in species abundances) assessing the consequences of ongoing environmental change on community structure.     

Intraspecific Functional Trait Variation in a Tree Species (Lithocarpus dealbatus) along Latitude

We quantied intraspecic variation and covariation of leaf mass per area (LMA), leaf dry matter concentration (LD), leaf frost sensitivity (LFS) and Fv/Fm of leaves of 8 Lithocarpus dealbatus populations across the geographical distribution from north to south to determine the magnitude and whether it is related to environmental conditions, latitude and mean annual temperature. The results showed that the total variation (coefcient of variation) of LMA, LD, LFS and Fv/Fm were 160%, 177%, 211% and 401% respectively. The total intraspecic variation was contributed by the difference among populations, individuals and leaves. The difference among populations accounted for the largest total variation in LMA, LD and Fv/Fm, whereas the difference among leaves accounted for the largest total variation in LFS. On population level, LMA was significantly positive related to the latitude and Fv/Fm was significantly negative, but LD and LFS were not related to the latitude. LMA decreased while Fv/Fm increased significantly with the increase of mean annual temperature. LD was a downward quadratic variation, and LFS was upward with the increase of mean annual temperature. The principal component analysis of four functional traits showed that no population was located nearer to the origin of the first and second principal component, and populations at the edge of distribution area located at both sides of the first principal component axis. The results suggested that the environmental variation in the distribution could cause intraspecic variation of functional traits. There is no population could represent a species in functional traits. When an average trait value for species is considered and trait comparisons are done among species, intraspecific variation of traits could not be ignored.     

Restoration of Species Richness in Abandoned Mediterranean Grasslands: Seeds in Cattle Dung

Abstract Endozoochory has proven to be a highly effective mechanism in the dispersal of viable seeds in Mediterranean grasslands. We studied the effect of cattle dung application on species richness, particularly on the reintroduction of species lost after abandonment. Sown and control plots were monitored for 3 years after dung sowing. We found a significant increase in small‐scale richness, which may be attributed to the treatment, with the inclusion of species detected in the dung and in the grazed pasture. The differences in richness and floristic composition diminished over time. This experiment proves the potential utility of this treatment for the restoration of species richness in abandoned pastures, although supplementary steps are necessary, including further sowing and/or shrub cutting in subsequent years.     

Topology of Plant - Flower-Visitor Networks in a Tropical Mountain Forest: Insights on the Role of Altitudinal and Temporal Variation

Understanding the factors determining the spatial and temporal variation of ecological networks is fundamental to the knowledge of their dynamics and functioning. In this study, we evaluate the effect of elevation and time on the structure of plant-flower-visitor networks in a Colombian mountain forest. We examine the level of generalization of plant and animal species and the identity of interactions in 44 bipartite matrices obtained from eight altitudinal levels, from 2200 to 2900 m during eight consecutive months. The contribution of altitude and time to the overall variation in the number of plant (P) and pollinator (A) species, network size (M), number of interactions (I), connectance (C), and nestedness was evaluated. In general, networks were small, showed high connectance values and non-nested patterns of organization. Variation in P, M, I and C was better accounted by time than elevation, seemingly related to temporal variation in precipitation. Most plant and insect species were specialists and the identity of links showed a high turnover over months and at every 100 m elevation. The partition of the whole system into smaller network units allowed us to detect small-scale patterns of interaction that contrasted with patterns commonly described in cumulative networks. The specialized but erratic pattern of network organization observed in this tropical mountain suggests that high connectance coupled with opportunistic attachment may confer robustness to plant-flower-visitor networks occurring at small spatial and temporal units.     

铜壁关自然保护区种子植物物种丰富度的海拔梯度格局——兼论物种密度的计算方法

利用对铜壁关自然保护区多次考察形成的种子植物数据库,结合通过GIS生成的区域数字高程模型(DEM)数据,分析了该区域种子植物物种丰富度及物种密度沿海拔梯度的变化特征。结果表明, 科、属、种的丰富度随海拔的升高,先增加后降低,在中海拔区域达到最大值,科、种的丰富度最大值出现在海拔1400~1800 m的范围内,属的丰富度最大值出现在1000~1400 m的海拔范围。科、属、种的密度随海拔升高先下降后上升,再下降后再上升;且最大值都出现在保护区最高海拔3000~3400 m的范围内。物种丰富度和物种密度分布格局明显受到海拔梯度的影响,海拔梯度综合了水热条件等诸多因素。铜壁关种子植物科、属、种水平上的物种丰富度的海拔分布格局符合中域效应假说;同时还对目前常用的计算物种密度的"对数模型"方法的普遍适用性提出质疑。     

Dissolved Organic Carbon in Headwater Streams and Riparian Soil Organic Carbon along an Altitudinal Gradient in the Wuyi Mountains,China

Stream water dissolved organic carbon (DOC) correlates positively with soil organic carbon (SOC) in many biomes. Does this relationship hold in a small geographic region when variations of temperature, precipitation and vegetation are driven by a significant altitudinal gradient? We examined the spatial connectivity between concentrations of DOC in headwater stream and contents of riparian SOC and water-soluble soil organic carbon (WSOC), riparian soil C:N ratio, and temperature in four vegetation types along an altitudinal gradient in the Wuyi Mountains, China. Our analyses showed that annual mean concentrations of headwater stream DOC were lower in alpine meadow (AM) than in subtropical evergreen broadleaf forest (EBF), coniferous forest (CF), and subalpine dwarf forest (SDF). Headwater stream DOC concentrations were negatively correlated with riparian SOC as well as WSOC contents, and were unrelated to riparian soil C:N ratio. Our findings suggest that DOC concentrations in headwater streams are affected by different factors at regional and local scales. The dilution effect of higher precipitation and adsorption of soil DOC to higher soil clay plus silt content at higher elevation may play an important role in causing lower DOC concentrations in AM stream of the Wuyi Mountains. Our results suggest that upscaling and downscaling of the drivers of DOC export from forested watersheds when exploring the response of carbon flux to climatic change or other drivers must done with caution.     

太白山北坡小型兽类物种多样性垂直分布格局北大核心CSCD

物种多样性沿海拔梯度的垂直分布格局一直是生物多样性研究的热点问题,其中最为普遍的分布模式为中峰格局。为了解太白山北坡小型兽类物种组成和物种多样性垂直分布格局,本研究于2020和2021年两年的6至9月采用样线法、铗日法和陷阱法对太白山北坡小型兽类物种进行调查。在海拔780~3767.2 m之间,以200 m为梯度,设置采集样点15个,累计布置4150铗次,陷阱105个,样线8条。共记录小型兽类4目7科12属21种148只,阔叶林中的小型兽类物种多样性普遍高于针叶林,物种多样性在中海拔地区栓皮栎(Quercus variabilis)林、锐齿槲栎(Q.aliena)林最高,高海拔地区秦岭冷杉(Abies fargesii)林最低。小型兽类物种多样性垂直分布格局为左偏倚中峰格局,物种多样性在1500~2300 m海拔段内出现峰值。这种分布格局和林型中小型兽类东洋界与古北界、特有种与非特有种在太白山地区交汇有关,太白山北坡南北纵列的山脉-沟谷地貌为南北物种扩散和迁移提供了有利条件,在沟谷内气候和地理特征相似,形成了规律的林型垂直带谱,这使得小型兽类物种多样性垂直分布也具有相似的特点。     

The Effect of Dew and Fog on Lithic Lichens Along an Altitudinal Gradient in the Negev Desert

The negative effect of high levels of heavy metals on the activity of soil microorganisms is well-known. However, some microorganisms survive even in high levels of heavy metals, and the microbial activity can therefore, help to recover these polluted soils. Microbial metal uptake in contaminated soils has to be tightly regulated to avoid toxic effects for the cells. These mechanisms of metal resistance are frequently associated to transport-related membrane proteins that mediate bacterium's direct metabolic interactions with the complex soil and aquatic harsh environments. This study reports the identification of gene clusters in rhizobial strains that are regulated by heavy metals, particularly chromium. A DNA fragment was amplified from R. leguminosarum, and in silico analysis of the sequence obtained revealed a putative protein homologue to a cation/multidrug efflux pump component (GenBank DQ398937). Another amplified DNA fragment, with 960 bp, has strong homology with anion ABC transporters (GenBank ZP_002212691) and a peptide ABC transporter (GenBank NP_766950), was identified in Mesorhizobium loti (GenBank DQ398941) and Sinorhizobium meliloti. Using Chromosome Walking technique, a single product from Sinorhizobium meliloti was cloned and sequenced. This new fragment enlarged more 302 bp to the initial sequence corresponding to the ABC transporter, confirming homology with an ATPase from PP superfamily (GenBank ZP_00197146.1).     

Taxonomy of the Solidago virgaurea Group (Asteraceae) in Poland,with Special Reference to Variability along an Altitudinal Gradient

The morphological differentiation and taxonomic treatment of lowland and high-mountain morphotypes within the Solidago virgaurea group are controversial. To clarify the taxonomic status of these taxa, we conducted a morphometric analysis of 1,746 individuals from 80 localities along an altitudinal gradient from the lowlands of northern Poland to the Carpathians and Sudetes of southern Poland. Multivariate morphometric analyses, cluster analyses and principal component analyses, were used to examine the morphological differentiation within the S. virgaurea group in Poland. Canonical discriminant analysis was applied to determine the morphological characters that best discriminate among the taxa. The stability of the high-mountain Solidago minuta morphotype was tested in an experimental field established in lowland Poland; individuals transplanted from various mountain sites were cultivated at this site, and the morphotypes remained stable in terms of their floral and vegetative characters. Multivariate analyses revealed two morphologically distinct taxa in the S. virgaurea group, which correspond to lowland S. virgaurea s. str. and high-mountain S. minuta as recognised in some European floras. The most important morphological characters for distinguishing the taxa are the number of tubular florets per capitulum, inner involucral bract width and involucre height. Vegetative and inflorescence characters appear to have less taxonomic value because they changed continuously with altitude. A key for identifying S. virgaurea and S. minuta in Poland is presented.     

北京市麻雀体质水平沿城市化梯度的变化

麻雀是城市和乡村均有分布的鸟类物种.快速的城市化正在使城市麻雀的栖息地和食物资源大量减少.以北京市为例,研究了麻雀的体质水平沿城市化梯度的变化,以期为我国城市化过程中的鸟类保护提供参考.研究结果表明城市高层楼房居民区、低层楼房居民区以及大学校园中麻雀的体质指数显著低于郊区环境,而城市公园和平房居民区麻雀的体质水平则与郊区环境的差异较小.随采样点城市化水平的增加,麻雀的体质水平呈下降趋势,高度城市化的环境导致麻雀的体质水平下降.在城市化过程中,增加城市公园的数量及居民区的植被覆盖量可为麻雀等鸟类提供必要的生活资源,从而实现城市化过程中的生物多样性保护.