中亚热带喀斯特常绿落叶阔叶林空间结构特征

喀斯特常绿落叶阔叶林是中国西南喀斯特地区非地带性顶极森林群落,该研究基于相邻木关系的角尺度、混交度和大小比数3个结构参数,对木论国家级自然保护区常绿落叶阔叶林25 hm^(2)大型固定监测样地整体、上木层、下木层及其优势物种的空间结构特征进行了分析,以期揭示其森林空间结构现状,为喀斯特植被恢复重建提供依据。结果表明:(1)样地群落整体为轻度聚集分布格局,接近随机分布,物种高度混交且个体间大小分化程度相近,上木层呈现随机分布、强度混交和中庸偏亚优势状态,下木层呈现聚集分布、强度混交和中庸偏劣势状态。(2)样地内优势物种大多处于轻度聚集分布、强度混交且中庸偏劣势的状态。(3)林木大小比数与胸径、树高均呈显著负相关关系,混交度与胸径、树高均呈显著正相关关系,随林木的生长发育,树种优势度逐渐增大,物种多样性逐渐增强。研究认为,木论常绿落叶阔叶林空间结构尚未完全稳定,正处于演替中后期,具有发育成顶极群落的潜力。     

喀斯特与非喀斯特森林乔木叶性状及其相关性网络的差异

喀斯特地区岩石裸露、土壤浅薄、持水能力差。对比分析喀斯特和非喀斯特森林树种叶性状有利于了解叶片对喀斯特生境的生理生态适应。前期比较研究集中在叶经济学性状,对叶水力学(抗旱)和机械抗性(防御)性状关注较少。该研究测定热带-亚热带地区典型喀斯特和非喀斯特森林共101种乔木的叶形态解剖、机械抗性和水力学性状,比较两个植物类群叶性状以及性状网络的差异。结果发现:(1)与非喀斯特森林乔木相比,喀斯特森林乔木叶撕裂力(F_t)较大、最大导水率(K_leaf＿max)较高,膨压丧失点(Ψ_tlp)和气孔安全边界均较低。(2)喀斯特森林乔木叶性状网络的平均路径长度和直径较短,边缘密度较大,表明叶性状之间的关联程度更高。(3)喀斯特森林乔木叶性状网络的关键性状为比叶质量(LMA)和机械抗性,而非喀斯特森林则为叶厚度(LT)和叶密度。喀斯特森林乔木LMA与Ψ_tlp负相关,与F_t正相关,即增加叶构建成本可同时提高机械抗性和耐失水能力;非喀斯特森林乔木无此相关关系。(4)喀斯特森林乔木K_leaf＿...     

柠条抗旱的生理生态与土壤水分关系的研究

采用LI－1600气孔计和压力室测试了风沙土上生长的柠条的SPAC系统的水分关系和P－V水分特征曲线,结果表明：当沙土含水率（W）的水分特征曲线的回归方程为：ψs=-40．32196×0．427905W,沙土平均含水率大于45％,柠条固沙林生长正常,叶水势高。沙土含水率小于4．5％时,柠条生长速度显著下降,柠条清晨叶水势（ψm）与沙土含水率（W）的回归方程为：ψm=－0．35926·e6．31144／W,风沙土上生长的柠条的“经济水阈”大约在4．5％左右,“生命水阈”大约在3．5％左右。     

西双版纳热带山地常绿阔叶林蕨类植物的组成及生态特征

根据4个50m×50m样地(400个5m×5m小样方,共计1hm2取样面积)的详细调查及对各样地外蕨类植物区系的采集调查,研究了西双版纳热带山地常绿阔叶林蕨类组成特点及其数量特征等。结果表明:在所调查的5hm2滇南热带山地常绿阔叶林里记录有蕨类植物64种;在生活型组成上,以地面芽和地下芽为主;在叶特征上,以革质和纸质叶居多,叶形以一回羽状和二回羽状叶占优势;在森林群落中蕨类植物有明显的季相变化;在重要值上,狗脊、疏叶蹄盖蕨、苏铁蕨、光叶鳞盖蕨、清秀复叶耳蕨和假稀羽鳞毛蕨的重要值之和占重要值总和的84.02%,其中,狗脊的重要值占重要值总和的1/3以上,它们是该森林群落中占优势的蕨类种类,在生态分布上为该森林群落的\"适宜种\";研究还发现,勐腊凤尾蕨为该森林群落的确限种。     

喀斯特常绿落叶阔叶混交林植物与土壤地形因子的耦合关系

基于中国科学院亚热带农业生态研究所在木论国家级自然保护区借鉴CTFS标准建立的2hm2喀斯特常绿落叶阔叶混交林动态监测样地(50个20m×20m样方),选取代表木本植物群落、土壤性质和地形因子的22个指标,对其总体特征及三者之间的相互关系进行了经典统计分析、主成分分析、聚类分析与典型相关分析。结果表明,喀斯特常绿落叶阔叶混交林生态系统的景观异质性强、土壤养分含量高、物种丰富且结构合理,除海拔、Simpson指数、均匀度、pH之外的18个指标均呈中、强变异;综合土壤因子是影响生态系统的主要因子群,其次是综合群落多样性因子和结构性因子,综合地形因子的作用相对较弱;4种不同类型真实而直观地表征了群落类型、土壤肥力和地形的差异,相对优化的第3种类型主要分布在海拔较高、裸石率较大、坡度较高的阴坡中上部;植被、土壤、地形两两之间均存在着较高的相关性,植被与土壤因子之间,有机质、氮、磷起较大的作用,主要影响群落结构,植被和地形之间,坡向和岩石裸露率影响群落结构和物种丰富度,而坡向和坡位直接导致了土壤有机质、全氮、有效磷和pH的变化。     

南亚热带森林演替过程生物量和生产力动态特征

以鼎湖山森林演替的空间系列及黑石顶天然次生林为研究对象,探讨了南亚热带森林群落生物量和生产力动态特征。研究结果表明,随着演替进程的发展,群落的生物量不断积累,但生物量的各用份的动态趋向并不一致,其中叶生物量的最高值出现在演替的中后期．在演替过程中生产力的动态与生物量变化相一致,随着演替的进展第一性生产力不断增加,但演替过程生产力的发展速率不是均匀的,生产力在群落的演变前期发展较侠,在中、后期则发展较慢。     

中国亚热带森林动态监测样地常绿和落叶木本被子植物谱系结构及生态习性差异

常绿和落叶木本被子植物是组成东亚地区亚热带阔叶林的两个主要植物类群。探索常绿和落叶木本被子植物的生态位差异, 对于推测亚热带阔叶林群落的生物多样性维持机制, 具有重要意义。该研究采用线性回归模型和Mantel检验多元回归等统计手段, 分析了中国亚热带地区8个森林动态监测样地的常绿和落叶木本被子植物谱系和生态习性差异。主要结果: (1)该研究的788个被子植物分类单元的叶习性(常绿和落叶)具有一定的谱系保守性。常绿和落叶植物对光照、温度、水分、土壤反应和土壤肥力因子的生态习性均有差异, 表现为常绿植物偏好较低的光照和土壤pH, 以及较高的温度、水分和土壤肥力; 落叶植物则相反。(2)样地内落叶较常绿植物的种间谱系散布更收敛, 但生态习性散布更发散; 样地间落叶较常绿类群的谱系组成差异更小, 但生态习性差异更大; 样地间落叶类群的谱系组成差异随年平均气温差异的增大而增大。(3)落叶/常绿植物物种数量的比例随年平均气温升高而降低, 而旱季持续时间和年降水量等因子的影响不明显。该研究证实了我国亚热带地区8个森林动态监测样地内的常绿和落叶木本被子植物在谱系和生态习性上均存在巨大差异, 生态位分化在很大程度上是促进亚热带阔叶林群落内生物多样性维持的重要机制。     

喀斯特常绿落叶阔叶混交林物种多度与丰富度空间分布的尺度效应

物种多样性的空间分布格局及其尺度效应是生态学研究的重点,对于理解物种多样性的形成和维持机制以及生物多样性的管理和保护均具有重要意义。以贵州茂兰国家级自然保护区分布的亚热带原生性喀斯特常绿落叶阔叶混交林为研究对象,分析了2个1hm2(100m×100m)样地中物种多度和丰富度的空间分布特征及其与取样尺度的关系,采用方差和变异系数描述多度和丰富度在5个尺度(5m×5m,10m×10m,20m×20m,25m×25m,50m×50m)上的空间变异性。结果表明:(1)两个样地的物种多度和丰富度具有尺度依赖性特征;(2)由于多度具有叠加性,物种多度的方差随着尺度的增加呈线性增加,而变异系数呈线性下降;(3)丰富度的方差随尺度的增加表现出单峰分布的特征,在25 m×25 m尺度上达到最大值,变异系数则随取样尺度的增加而呈线性下降。研究表明,物种多度具有尺度推演规律,而丰富度却没有,因此,应慎重进行物种丰富度的尺度推演。在分析喀斯特森林物种多样性时,应注重尺度效应带来的影响。     

Bryophytes in perennially moist forests of Papua New Guinea: ecological orientation and predictions of disturbance effects

Water relations of bryophytes must be understood along at least four dimensions: hydration/dehydration frequency; hydration duration; dehydration duration; degree of water loss. All these are biomass-dependent functions such that large colonies of bryophytes may maintain hydration longer than smaller colonies. The spread of a bryophyte colony allows lateral movement of capillary water; contiguous clones will thus allow lateral conduction of that water. In contrast, separated tufts or cushions may store water but will contribute very little to its transfer over the surface of the phorophyte.
Many of the tropical rainforests of New Guinea have a larger mass of epiphytic bryophytes than any temperate forest. The primary effect of disturbance in these forests is a reduction in bryomass, presumably due to desiccation because of increased insolation and wind movement. The reduction of bryomass will decrease water and mineral retention in the bryophyte clones; and the reduction in the size of those clones will reduce their contiguity and thus interfere with bryophyte-mediatcd water and mineral transfer. Disturbance may alter bryophyte species frequency but, under present agricultural and forestry practices in New Guinea, I have seen no evidence of significant loss of bryophyte species.     

Changes in morphological and physiological traits of the freshwater plant <Emphasis Type="Italic">Ranunculus peltatus</Emphasis> with the phosphorus bioavailability

Plastic adjustments in response to P availability were investigated for a freshwater, submerged plant, Ranunculus peltatus Schrank at various stages in its life-cycle. A series of three, nine-day-experiments was performed under controlled conditions in April, June and August. R. peltatus plasticity was tested in response to three phosphorus water concentrations (50, 100, 300 μg/l PO₄³⁻–P) and was evaluated using eight morphological and ecophysiological traits related to plant nutrient uptake and use. Some plastic adjustments in R. peltatus were found to be significant mostly for the April experiment. R. peltatus displayed higher nutrient uptake and lower NUE when P availability was high. It tended also to adapt its P uptake rate which decreased during the experiment. When P availability was low, reverse results were found in the four ecophysiological traits. No morphological plastic adjustments in response to P enrichment were identified in R. peltatus concerning branching or creation of roots. However, the production of sexual organs tended to be enhanced by low P concentrations in the water. Ecophysiological rather than morphological adjustments were highlighted in R. peltatus with respect to P availability. Plasticity was found to depend strongly on the particular phenological stage. These results may constitute valuable information concerning the evaluation and ecological significance of plasticity in freshwater plants     

Are the dynamics of tropical forests dominated by large and rare disturbance events?

A recent Ecology Letters paper of Fisher et al. (2008) utilized a modelling framework to investigate disturbance effects on forest biomass dynamics. But it contains serious methodological and conceptual errors. Associated conclusions are unlikely to be correct.     

Butterfly diversity and silvicultural practice in lowland rainforests of Cameroon

Butterfly diversity and abundance were sampled across eight 1-ha silvicultural treatment plots in southern Cameroon. The plotsincluded a cleared and unplanted farm fallow, cleared and replanted forestplots, and uncleared forest plots. The replanted plots were line-planted withTerminalia ivorensis, but differed in the degree and methodof clearance. A total of 205 species of butterflies were collected over twodifferent seasons. Several sampling methods were used, including hand collecting andbaited canopy traps. Sites with the greatest degree of disturbance andlowest level of tree cover had the lowest number of individuals and species ofbutterflies. The farm fallow had substantially fewer individuals and species ofbutterflies than the other plots. The replanted plots were intermediate betweenthe farm fallow and uncleared forest in terms of abundance, richness andcomposition. With all three forms of multivariate analysis (Morisita similarityindex clustering, detrended correspondence analysis and two-way indicatorspecies analysis) largest differences were found between the farm fallow anduncleared forest plots. The butterfly fauna of the uncleared forest more closelyapproximated that of the manually cleared plot than that of the mechanicallycleared plot. We found that although, in general, young replanted forest plotsare a poor substitute for native forest, they do provide habitat for some forestspecies and that this may increase over time as the plots mature.     

Ecophysiological responses to light availability in three Blechnum species (Pteridophyta, Blechnaceae) of different ecological breadth

In Chilean evergreen temperate forest, fern species of the genus Blechnum occur in diverse microhabitats ranging from large gaps to heavily shaded understoreys. We hypothesised that differences in the ecological breadth of three co-occurring Blechnum species would be associated with differences in magnitude of ecophysiological responses to light availability. We quantified the field distribution of each species in relation to diffuse light availability (% canopy openness), and measured in situ variation in photosynthetic capacity (A), dark respiration (R _d) and specific leaf area (SLA) across the light gradient. The response of SLA of each species was also evaluated in a common garden in two light conditions (understorey and forest edge). The three Blechnum species differed significantly in the range of light environments occupied (breadth: B. chilense > B. hastatum > B. mochaenum). Despite significant interspecific differences in average A and R _d, the response of these traits to light availability did not differ among species. However, there was significant interspecific variation in both the mean value and the plasticity of SLA to light availability, the species with least ecological breadth (B. mochaenum) showing a flatter reaction norm (lower response) than its two congeners. This pattern was also found in the common garden experiment. The adjustment of leaf morphology (SLA) to light availability appears to be an important mechanism of acclimation in these Blechnum species. The narrow range of light environments occupied by B. mochaenum may be at least partly attributable to its inability to display phenotypic plasticity in SLA to changes in light availability.     

木瓜榕传粉生物学

 木瓜榕（Ficus auriculata Lour.）是雌雄异株植物,它只有通过大果榕小蜂（Ceratosolen emarginatus Mayr）传粉才能获得有性繁殖,大果榕小蜂也仅在木瓜榕雄果内产卵才得以繁衍后代。经两年来的实验和研究结果表明：木瓜榕繁殖能力在不同季节随进蜂量的多少而变化,雌树在4月和11月出现的两次结果高峰期与进蜂量最多的时期相遇;同时雄树与雌树在11月挂果高峰期重叠,导致该期进入雄果产卵的雌蜂量减少,进蜂量高峰推迟到部分雄果成熟、只有稀少接受果的3月下旬和4月上旬。木瓜榕在与大果榕小蜂互惠共生的进化历程中,逐渐完善了自身保证远交的繁殖机制,它们在不同程度上受到雌雄异熟、雌雄异株和短花柱雌花不亲和3种机制的共同作用。温湿度对大果榕小蜂访果行为有明显的影响,在温湿度变化缓和的早晚,有利于榕小蜂出行,雌蜂访果最为频繁。大果榕小蜂活动最佳的温湿度是：温度20～24 ℃之间、湿度85%～93%之间;温度高于29 ℃、湿度低于58% 或风雨天均不利于该蜂出行活动。榕小蜂日活动高峰的出现先后在不同季节略有差异,高温高湿的夏季榕小蜂活动出现早,7∶40达高峰;秋季榕小蜂活动推迟,高峰出现在11∶00;干凉的冬季最晚,13∶00才到达高峰。通过人工套袋、放蜂传粉试验,平均进8头的隐头果传粉效率最高,单果平均种子数量为11 247粒,结实率50.8%,未受精的败育花8 207朵;平均进蜂4头以下或10头以上的隐头果,由于花粉量不足或者雌蜂争夺资源的损伤使种子量下降,平均结实率分别达37.2% 和44.4%;放蜂试验结果与大量调查自然界中每果进蜂量和结实率的结果一致。     

Invasive species can handle higher leaf temperature under water stress than Mediterranean natives

Thermal tolerance of Photosystem II (PSII) highly influences plant distribution worldwide because it allows for photosynthesis during periods of high temperatures and water stress, which are common in most terrestrial ecosystems and particularly in dry and semi-arid ones. However, there is a lack of information about how this tolerance influences invasiveness of exotic species in ecosystems with seasonal drought. To address this question for Mediterranean-type ecosystems (MTE) of the Iberian Peninsula, we carried out an experiment with fifteen phylogenetically related species (8 invasive and 7 native, Pinus pinaster Ait., Pinus radiata D. Don, Schinus molle Linn., Elaeagnus angustifolia L., Eucalyptus globulus Labill., Acacia melanoxylon R. Br., Gleditsia triacanthos L., Pistacia terebinthus L., Rhamnus alaternus L., Anagyris foetida L., Colutea arborescens L., Oenothera biennis L., Epilobium hirsutum L., Achillea filipendulina Lam. and Achillea millefolium L). Seedlings were grown and maximal photochemical efficiency of PSII (Fv/Fm) was measured at two water availabilities (well-watered and with water stress). PSII thermal tolerance measurements were related to specific leaf area (SLA), which varied significantly across the study species, and to the mean potential evapotranspiration (PET) of the month with the lowest precipitation in the native areas of both groups and in the invaded area of the Iberian Peninsula. Additionally, PSII thermal tolerance measurements under water stress were phylogenetically explored. Invasive and native species neither differed in SLA nor in their thermal tolerance under well-watered conditions. For well-watered plants, SLA was significantly and positively related to PSII thermal tolerance when all species were explored together regardless of their invasive nature. However, this relationship did not persist under water stress and invasive species had higher plastic responses than Mediterranean natives resulting in higher leaf temperatures. Higher PSII thermal tolerance could explain invasiveness because it allows for longer periods of carbon acquisition under water stress. In fact, PSII thermal tolerance was positively related to the PET of the invaded and native areas of the Iberian Peninsula. PSII thermal tolerance was not related to PET at the native range of the invasive species, suggesting that successful invasive species were plastic enough to cope with novel dry conditions of the Iberian Peninsula. Moreover, our phylogenetic results indicate that future scenarios of increased aridity in MTE associated to climate change will filter invasion success by taxonomic identity. This study reveals the importance of studying ecophysiological traits to understand and better predict future biological invasions.     

Functional anatomy of five endangered tropical timber wood species of the family Dipterocarpaceae

Wood anatomy of five dipterocarp species endemic to the Philippines was studied with the goal to explore functional wood traits of ecological significance. Stem wood of 6-year-old trees grown under similar environmental conditions in a plantation (Leyte, Philippines) was used. Wood densities decreased in the following order Hopea plagata > Dipterocarpus kerrii > Parashorea malaanoman > Shorea almon ≈ Shorea contorta. This was mainly caused by significantly thicker fiber cell walls of H. plagata and D. kerrii than those of the other three species. Wood density was negatively correlated with the abundance of axial parenchyma cells. Predicted conductance was independent from wood density and lowest in H. plataga and highest in D. kerrii and S. contorta. These results indicate that H. plagata and D. kerrii is woods have higher constructions costs in term of carbon per unit of biomass, and that H. plagata is probably better acclimated to varying soil moisture than the other species.