石灰岩地区连片出露石丛生境植物水分来源的季节性差异

以桂西北石灰岩地区连片出露石丛生境次生林群落为研究对象, 运用稳定性氢氧同位素技术结合IsoSource模型, 分析了5种典型植物(半落叶乔木粉苹婆(Sterculia euosma)、落叶乔木菜豆树(Radermachera sinica)、常绿灌木鹅掌柴(Schefflera octophylla)以及落叶灌木红背山麻杆(Alchornea trewioides)和紫弹树(Celtis biondii))水分来源的季节性差异。结果表明: 雨季, 除鹅掌柴同时利用部分前期雨水外, 其余4种植物均主要利用最近15天内的雨水(利用比例的平均值之和均超过80%)。旱季, 5种植物均主要利用最近一次雨水与前期雨水(一个月前)的混合(利用比例的平均值之和均超过80%), 其中乔木和常绿灌木对前期雨水的利用比例更高(利用比例的平均值均超过50%)。植被良好的石灰岩连片出露石丛生境中, 植物主要以不同时期的雨水为主要水源, 这可能与石灰岩发育的裂隙及其储水能力有关。储存在裂隙中的雨水通过植物蒸腾的方式返回大气, 这一良好的水文循环过程应得到充分的保护。     

出露基岩生境典型植物树干液流对自然降水和连续干旱的响应特征

以西南喀斯特地区常见的出露基岩生境为研究对象,针对该类生境典型乔木类植物菜豆树和圆叶乌桕,应用TDP热扩散探针技术,结合遮雨试验,分析了植物树干液流对自然降水和连续干旱的响应特征.结果表明:在生长季不同时期,降水后2树种液流密度较降水前均有一定程度的升高,但始终呈现落叶乔木圆叶乌桕高于半落叶乔木菜豆树的特征;连续2个月遮雨条件下,2树种液流密度均无明显降低的趋势,表明2树种均不依赖受近期降水主导的水源;通过对降水前后及连续干旱条件下2树种液流密度与环境因子的拟合关系研究发现,气象因素差异对水分环境变化条件下植物蒸腾耗水的影响较小.自然降水和短时期的连续干旱并未显著改变2树种的蒸腾耗水特征,这可能与出露基岩生境特殊的水分蓄持环境和乔木类植物依赖相对稳定的深层水源有关.     

Seasonal patterns of terpene content and emission from seven Mediterranean woody species in field conditions

The seasonal pattern of terpene content and emission by seven Mediterranean woody species was studied under field conditions. Emission rates were normalized at 30°C and 1000 μmol·m·s PFD (photosynthetic photon flux density). Bupleurum fruticosum, Pinus halepensis, and Cistus albidus stored large amounts of terpenes (0.01-1.77% [dry matter]) with maximum values in autumn and minimum values in spring. They emitted large amounts of terpenes (2-40 μg·g DM·h), but with no clear seasonal trend except for Cistus albidus, which had maximum values in spring and minimum values in autumn. The nonstoring species Arbutus unedo, Erica arborea, Quercus coccifera and Quercus ilex also emitted large amounts of terpenes (0-40 μg·g DM·h) and also tended to present maximum emission rates in spring, although this trend was significant only for A. unedo. At the seasonal scale, emission rates did not follow changes in photosynthetic rates; instead, they mostly followed changes in temperature. From autumn to spring, the least volatile monoterpenes such as limonene were emitted at highest rates, whereas the most volatile monoterpenes such as α-pinene and β-pinene were the most emitted in summer. The monoterpene emission rates represented a greater percentage of the photosynthetic carbon fixation in summer (from 0.51% in Arbutus unedo to 5.64% in Quercus coccifera) than in the rest of the seasons. All these seasonality trends must be considered when inventorying and modeling annual emission rates in Mediterranean ecosystems.     

Seasonal changes in nitrate use by three woody species: the importance of the leaf-expansion period

Seasonal changes in plant NO₃ ⁻-N use were investigated by measuring leaf nitrate reductase activity (NRA), leaf N concentration, and leaf expansion in one evergreen woody species (Quercus glauca Thunb.) and two deciduous woody species [Acer palmatum Thunb. and Zelkova serrata (Thunb.) Makino]. Leaf N concentration was highest at the beginning of leaf expansion and decreased during the expansion process to a steady state at the point of full leaf expansion in all species. The leaf NRA of all species was very low at the beginning of leaf expansion, followed by a rapid increase and subsequent decrease. The highest leaf NRA was observed in the middle of the leaf-expansion period, and the lowest leaf NRA occurred in summer for all species. Significant positive correlations were detected between leaf NRA and leaf expansion rates, while leaf N concentrations were negatively correlated with leaf area. In the evergreen Q. glauca, the N concentration in current buds increased before leaves opened; concurrently, the N concentration in 1-year-old leaves decreased by 25%. Our results show that the leaf-expansion period is the most important period for NO₃ ⁻-N assimilation by broadleaf tree species, and that decreases in leaf N concentration through the leaf-expansion period are at least partly compensated for by newly assimilated NO₃ ⁻-N in current leaves.     

Potential use in phytoremediation of three plant species growing on contaminated mine-tailing soils in Sardinia

We have analyzed the relationship between total Zn, Pb and Cu concentrations in the soil and the capacity of three plant species to accumulate these elements in their leaves. The study was carried out in a highly contaminated area at Sulcis-Iglesiente (SW-Sardinia, Italy). We took samples of the leaves of Dittrichia viscosa, Cistus salviifolius and Euphorbia pithyusa subsp. cupanii and samples of the soil beneath each of them at depths of 0-30 and 30-60 cm, both in contaminated mine tailings and surrounding areas. Due to the anthropic origin of the soil materials the results varied considerably. Bioavailability of trace elements was mainly related to the calcium-carbonate content and the crystalline and amorphous forms of iron in the soil. The concentration of Zn in the leaves of the three plant species studied was highest, followed by Pb and finally Cu. The leaves of Dittrichia viscosa contained the highest concentrations of trace elements and this species may be considered as being a “phytoextractor” in soils where the trace-element concentrations are not too high. Euphorbia pithyusa subsp. cupanii had low trace-element concentrations in its leaves despite growing in highly contaminated soils, and so might be used as a “phytostabilizer”. Although Cistus salviifolius does not grow in the most contaminated soils, could be considered as a contamination indicator up to a given level.     

Seasonal patterns of dehydrins and 70-kDa heat-shock proteins in bark tissues of eight species of woody plants

Although considerable effort has been directed at identifying and understanding the function and regulation of stress-induced proteins in herbaceous plants, reports concerning woody plants are limited. Studies with herbaceous crops have revealed similarities in the types of proteins that accumulate in response to a wide array of abiotic stresses and hormonal cues such as the accumulation of abscisic acid. Many of the identified proteins appear to be related to dehydrins (the D-11 subgroup of late-embryogenesis-abundant proteins). The objective of the present study was to determine if seasonal induction of dehydrins is a common feature in woody plants and to see if seasonal patterns existed for other stress-induced proteins. Bark tissues from eight species of woody plants were collected monthly for a period of 1.5 years. The species included: peach (Prunus persica) cv. Loring; apple (Malus domestica) cv. Golden Delicious; thornless blackberry (Rubus sp.) cv. Chester; hybrid poplar (Populus nigra); weeping willow (Salix babylonica); flowering dogwood (Cornus florida); sassafras (Sassafras albidum); and black locust (Robinia pseudo-acacia). Immunoblots of bark proteins were probed with a polyclonal antibody recognizing a conserved region of dehydrin proteins, and monoclonal antibodies directed against members of the HS70 family of heat-shock proteins. Some proteins, immunologically related to dehydrins, appeared to be constitutive; however, distinct seasonal patterns associated with winter acclimation were also observed in all species. The molecular masses of these proteins varied widely, although similarities were observed in related species (willow and poplar). Identification of proteins using the monoclonal antibodies (HSP70, HSC70, BiP) was more definitive because of their inherent specificity, but seasonal patterns were more variable among the eight species examined. This study represents only a precursory examination of several proteins reported to be stress related in herbaceous plants, but the results indicate that these proteins are also common to woody plants and that further research to characterize their regulation and function in relation to stress adaptation and the perennial life cycle of woody plants is warranted.     

古田山亚热带常绿阔叶林树皮厚度的变异特征

树皮是木本植物茎干最外层结构,具有保护茎干、养分储存与运输等重要作用。因此,树皮厚度是一项非常重要的功能性状,其变异不仅影响树皮的各种生态功能,还能影响群落构建与物种共存。然而,以往对树皮厚度的研究集中于火灾易发生态系统,对火灾不易发生的亚热带常绿阔叶林的研究仍较缺乏。测量了古田山国家级自然保护区亚热带常绿阔叶林内树种的树皮厚度,并检验了总树皮厚度、内树皮厚度与外树皮厚度在各分类群间以及功能群间的差异。结果发现：1）39个树种807个个体的总树皮厚度、内树皮厚度与外树皮厚度均值分别为1.90 mm、1.38 mm和0.54 mm。漆树科（Anacardiaceae）、杨梅科（Myricaceae）以及亚热带常绿阔叶林代表类群壳斗科（Fagaceae）、山茶科（Theaceae）的树皮厚度较大。短柄枹（Quercus serrata）、木荷（Schima superba）、小叶青冈（Cyclobalanopsis myrsinifolia）等树种的树皮厚度较大。2）种间、科间的各树皮厚度差异均显著。不同功能类群间,乔木类群的各树皮厚度均较灌木类群大,常绿类群的各树皮厚度均较落叶类群大（内树皮厚度除外）。本次研究结果表明,相对于火灾易发生态系统中的树皮厚度,古田山亚热带常绿阔叶林群落内的树皮厚度相对较薄,表明这些森林树种对当地湿润气候的适应性。同时,树皮厚度在各种分类水平与功能群水平间的显著变异,反映了群落内不同生态策略的共存。     

Seasonal patterns of mercury species in water and plankton from softwater lakes in Northeastern Minnesota

Twelve softwater lakes in NE Minnesota were sampled in spring, summer, and fall of 1992 and 1993 for labile (unextracted) methyl-Hg, total (extracted) methyl-Hg, and total Hg in lake water and net plankton (300 µm). The lakes are small (5.6–56 ha), low productivity, headwater drainage or seepage lakes. They are acid-sensitive (ANC 200 µeq/L) but not low pH lakes (average pH 6.6). The lakes ranged in color from 8.5 to 70 PCU. Statistical analysis of the water chemistry variables and mercury species support the conclusion that these were a homogeneous set of lakes; therefore, seasonality of mercury forms was analyzed on combined (mean) data from the 12 lakes. Methyl-Hg in water declined throughout the growing season. Hg_T also declined sharply from spring to summer but increased again in the fall. In contrast to the methyl-Hg and Hg in water, concentrations in plankton were at the lowest levels in spring and rose to higher levels in summer. The mass of mercury in plankton increased from spring to fall, as did the methyl-Hg fraction, which increased from 20% of Hg_T in spring to 52% in autumn. Bioaccumulation factors (BAF) for methyl-Hg in net plankton increased over the growing season. Overall, log BAF for Hg_T in net plankton (wet wt.) was 4.45. Log BAF for methyl-Hg in plankton was 4.90 to 5.43 depending on the analytical form of methyl-Hg in water (labile or total). Seasonal patterns of methyl-Hg and Hg_T did not covary in water, but did covary in plankton. These results support the conclusion that measurement of Hg in water is not adequate in itself to determine the amount of bioavailable Hg (i.e., methyl-Hg) in a lake. Labile (unextracted) methyl-Hg could be a useful measurement of bioavailable Hg. Labile methyl-Hg exhibits the same seasonal patterns as total methyl-Hg, but does not require the extraction steps necessary for measuring total methyl-Hg.     

Rooting characteristics of two widely distributed woody plant species growing in different karst habitats of southwest China

A series of studies claimed that deep root development of plant established in karst regions was facilitated by fractured bedrock beneath the shallow soils; however, bedrock is not a uniform medium for root proliferation. We hypothesized plant species that survived in different karst habitats had some other rooting characteristics rather than deep penetration. To test the hypothesis, coarse root systems of two widely distributed woody species (one tree and one shrub) growing in three typical rocky karst habitats (shallow soil, loose rocky soil and exposed rock) were excavated in karst region of southwest China. Root systems were investigated based on four parameters: maximum rooting depth, maximum radial extent, root tapering pattern and root curvature. In all the three habitats, maximum rooting depths were no deeper than 120 and 40 cm for the tree and shrub species, respectively. Maximum radial extents were extremely large compared with maximum rooting depth, indicating that rooting characteristics were dominated by horizontal extension rather than deep penetration. Roots of both species growing in shallow soil habitat tapered gradually and curved slightly, which was consistent with the specific characteristics of this habitat. On the contrary, roots of the tree species growing in the other two habitats tapered rapidly but curved slightly, while roots of the shrub species tapered gradually but curved strongly. It was speculated that limited depths and rapid tapering rates of the tree roots were likely compensated by their utmost radial extensions, while the shrub species might benefit from its root curvature as the associated root tropisms may increase the ability of root to encounter more water and contribute to potentially high resource absorption efficiency. Our results highlight the importance of taking shallow-rooted species into account in understanding the distribution of natural plant communities and predicting future vegetation dynamics in karst regions.     

Effects of smoke water and karrikin on seed germination of 13 species growing in China

Plant-derived smoke water (SW), derived from combusted plant material, has been shown to stimulate seed germination and improve seedling vigor of a number of plant species from fire-dependent Mediterranean-type climate areas. The effects of SW on seed germination of 13 plant species from southern tropical and subtropical monsoon climate regions of South China are reported for the first time in this study using laboratory and pot trials. Among the 13 species tested, only Aristolochia debilis showed a significant positive response to commercial SW when diluted 1:10. Seed germination of A. debilis was also stimulated by 1–100 nM 3-methyl-2H-furo [2, 3-c] pyran-2-one (karrikin 1 or KAR₁) and by 10–1000 µM gibberellic acid (GA₃). GA₃ stimulated seed germination of Santalum album and significantly elongated the radicles of A. debilis while SW could not. The functions and/or metabolic pathways of Kar₁ and GA₃ are likely to be separate and/or distinct.     

Root density distribution and biomass allocation of co-occurring woody plants on contrasting soils in a subtropical savanna parkland

Plant and Soil - Mechanisms and transporters responsible for Ni uptake in plants are largely unknown. To characterize Ni uptake mechanisms in Ni hyperaccumulators, we compared the effects of...     

Leaf respiration/photosynthesis relationship and variation: an investigation of 39 woody and herbaceous species in east subtropical China

Thirty-nine plant species including woody and herbaceous species grown in wet and warm subtropical regions were collected and classified into woody and herb functional groups. Net photosynthesis (P _n) and dark respiration (R) were measured at constant 25°C under neither water nor nitrogen limited condition to assess whether the R/P _n ratio was constant across different species and functional groups. Our results suggest that P _n and R were highly skewed among the 39 species, ranging from 5 to 25 and 1 to 5 μmol m⁻² s⁻¹, respectively, while R/P _n ratio was normally distributed at 0.1–0.3. Mean R/P _n ratio was 0.19 for 39 species, and 0.20 and 0.18 for woody and herbs, respectively, showing no significant difference between the two groups. Leaf P _n, R, and R/P _n ratios exhibited large variations across 39 species while R/P _n ratio in our subtropical species was considerably higher than other studies. Our results also indicated that the difference within each group was even larger than between the two groups. Based on the pooled data set at global scale, and considering R/P _n ratios performance under a combination of wet and warm conditions, the mean R/P _n ratio of 0.19 fell between the R/P _n ratio of 0.23 under dry and warm conditions and the R/P _n ratio of 0.07 under cold regardless of the precipitation conditions. The comparison with published data sets indicated significant effects of long-term precipitation and temperature on leaf R/P _n ratios at global scale, and we found that the plants adapting to warm and wet climates including our thirty-nine species tend to have a lower R/P _n ratio.     

南亚热带森林群落种-多度的对数正态分布模型研究

通过对地处南亚热带的广东省黑石顶自然保护区森林群落的定点研究结果的分析表明：当用１,２,３,…分组每种个体数ｒ时,５个不同类型的群落样地的种一多度分布的直方图都呈明显的倒Ｊ－形;经Ｐｒｅｓｔｏｎ“倍程（ｏｃｔａｖｅｓ）”法分组ｒ后,其种－多度都服从对数正态分布。由种－多度模型可以推出另一新的模型一个体一多度分布模型,即Ｉ（Ｒ）＝２R0ＳＯＥＸＰ［［１ｎ２）２／４ａ２〕ＥＸＰ｛－ａ２（Ｒ－（ＲＯ＋１ｎ２／２ａ２）］２｝,它也符合对数正态分布。另外,还运用积分方法推导出估计总体（整个群落）中总种数Ｓ*和总个体数Ｉ*理论值的公式,用此公式估计的结果较为合理。     

钱江源国家公园古田山常绿阔叶林木本植物的萌生更新特征

萌生更新是木本植物在原位进行更新的有效手段,使群落具有较强的恢复力。但以往研究侧重于实生更新,森林中木本植物的萌生更新特征及其在森林群落中的地位仍未得到足够理解。基于钱江源国家公园古田山国家级自然保护区内5 hm2亚热带常绿阔叶林样地的群落数据,分析木本植物萌生更新的数量特征,同时对不同分类单元、不同功能类群的萌生能力等进行比较。结果表明:(1)样地内64%的物种、20%的实生个体已经发生萌生更新现象,且萌生茎的数量占样地总个体数量的24%;(2)物种水平与科水平上,萌生能力均表现为显著差异(F=13.11,P0.001;F=27.45,P0.001)。腺蜡瓣花、柳叶蜡梅、宜昌荚蒾、窄基红褐柃、美丽马醉木等物种的萌生能力较强,蜡梅科、忍冬科、木兰科、壳斗科等类群的萌生能力较强;(3)不同垂直结构层次(林冠层、亚乔木层、灌木层)的萌生能力差异显著(F=117.5,P0.001),灌木层物种的萌生能力是林冠层与亚乔木层的1倍左右。不同生活型(常绿组分与落叶组分)的萌生能力差异显著,常绿类群的萌生能力显著高于落叶类群(P0.001)。萌生更新在亚热带常绿阔叶林中具有重要地位,可能是物种多样性维持、群落更新与演替的机制之一。灌木物种与常绿物种有着较强的萌生能力,暗示着萌生可能是植物适应荫蔽环境的生态策略之一。     

亚热带常绿阔叶林木本植物幼树阶段抽枝展叶的权衡关系

亚热带常绿阔叶林植物幼树阶段适应林内生境并开枝散叶是其长成大树的一个重要过程, 植物一年内多次抽枝的现象及其在抽枝展叶过程中小枝伸长、枝茎增粗与叶面积的增加优先顺序及其内在驱动机制还有待进一步研究。该研究对青城山常绿阔叶林木本植物多次抽枝发生比例进行了调查, 并以茶(Camellia sinensis)、细枝柃(Eurya loquaiana)、短刺米槠(Castanopsis carlesii var. spinulosa)、润楠(Machilus nanmu)和大叶山矾(Symplocos grandis) 5种植物的幼树为研究对象, 比较分析了植物在多次抽枝中小枝和叶片生长动态及适应策略的差异。结果显示: 1)一、二次抽枝分别开始于春季(4月)和夏末(8月下旬), 小枝水平上二次抽枝率乔木小于灌木, 常绿植物小于落叶植物。2)一次抽枝小枝枝长、单叶面积, 小枝直径和叶片数量(除大叶山矾外)均高于二次抽枝, 但二次抽枝单叶面积相对生长速率均高于一次抽枝, 二次抽枝叶片比叶质量(LMA)的增长速率高于一次抽枝。3)一次抽枝小枝枝长、叶片数量、小枝直径(除细枝柃和短刺米槠外)和总叶面积(除短刺米槠外)最大相对生长速率均高于二次抽枝, 且大部分物种最大相对生长速率出现在抽枝开始的第一、二周。4)两次抽枝中, 物种先侧重于叶片的生长, 其次是小枝枝长的生长, 最后是小枝直径的增粗。单叶面积和总叶面积皆随着小枝枝长和小枝直径的增加呈显著的异速生长关系, 表明叶片的增长速度大于小枝。单叶面积与叶片数呈显著大于1的异速生长关系, 暗示单叶面积的增长速度大于叶片数的增加速度。小枝枝长与小枝直径也呈显著大于1的异速生长关系, 揭示小枝枝长的增长速度大于小枝直径。综上所述, 两次抽枝过程中, 植物枝叶的优先生长顺序反映了植物为获取更多的资源(尤其是光源)而形成特定的抽枝展叶策略; 二次抽枝单叶面积相对生长速率和LMA增长速率高于一次抽枝, 这可能与植物即将面临的昆虫取食和气温降低压力有关。因此, 了解植物抽枝策略对于理解物种生态适应机制, 揭示物种生活史过程中存在的权衡关系具有重要的理论意义。     

Structure and species richness in wetland continua on sandy soils in subtropical and tropical Australia

Net photosynthetic fixation of wetland plant communities is confined to the period of the year when the surface soil is not waterlogged and is thus well aerated. In the open‐structured vegetation continuum across freshwater wetlands on sandy soils in subtropical and tropical Australia, the sum of the foliage projective covers (FPCs) of the overstorey and understorey strata remains constant, while that of the overstorey decreases to zero as seasonal waterlogging (and anaerobic conditions) in the surface root systems increases. Density and height of the overstorey trees – of only one or two species – and species richness (number of species per hectare) in the understorey decreases along this waterlogging gradient. Melaleuca paperbark trees, possessing surface roots with cortical aerenchyma, may form a closed‐forest at the edge of the wetland continuum wherever there is a continuous flow of aerated water. As global warming progresses, an increase in air temperature in the atmosphere flowing over and through the wetland continuum during the short period of annual foliage‐growth will affect the combined FPCs of overstorey and understorey strata, as well as the leaf‐specific weights of all leaves throughout the plant community. With a reduction in net photosynthetic fixation, species richness of the plant community will slowly decline.     

Source water, phenology and growth of two tropical dry forest tree species growing on shallow karst soils

Seasonally dry tropical forests are dominated by deciduous and evergreen tree species with a wide range of leaf phenology. We hypothesized that Piscidia piscipula is able to extend leaf senescence until later in the dry season due to deeper and more reliable water sources than Gymnopodium floribundum, which loses leaves earlier in the dry season. Physiological performance was assessed as timing of leaf production and loss, growth, leaf water potential, depth of water uptake determined by stable isotopes, and leaf stable isotopic composition of carbon (δ¹³C) and oxygen (δ¹⁸O). P. piscipula took water primarily from shallow sources, whereas G. floribundum took water from shallow and deep sources. The greatest variation in water sources occurred during the onset of the dry season, when G. floribundum was shedding old leaves and growing new leaves, but P. piscipula maintained its leaves from the previous wet season. P. piscipula showed greater relative growth rate, greater leaf expansion rates, and more negative predawn and midday water potentials than G. floribundum. P. piscipula also exhibited greater leaf organic δ¹³C and lower δ¹⁸O values, indicating that the decrease in photosynthetic carbon isotope discrimination was associated with greater stomatal conductance and greater photosynthesis. Our results indicate that the contrasting early and late dry season leaf loss phenology of these two species is not simply determined by rooting depth, but rather a more complicated suite of characteristics based on opportunistic use of dynamic water sources, maximizing carbon gain, and maintenance of water potential during the dry season.     

甘肃4种亚热带常绿阔叶木本植物分布新记录

报道了甘肃省4种亚热带常绿阔叶木本植物分布新记录：黄丹木姜子〔Litsea elongata （Wall. ex Nees） Benth. et Hook. f.〕、总梗女贞（Ligustrum pricei Hayata）、攀缘胡颓子（Elaeagnus sarmentosa Rehder）、栓叶安息香（Styrax suberifolius Hook. & Arn.）。其中,栓叶安息香和攀缘胡颓子也是秦岭植物分布新记录。这些植物的发现进一步丰富了甘肃省亚热带常绿阔叶木本植物资源,对于研究西秦岭地区亚热带木本植物的物种多样性和植物区系具有重要意义。新记录凭证标本存放于陇南师范高等专科学校植物标本室。