中国典型地带陆生等足类的区系研究

通过对我国５个典型地带（热带、亚热带、暖温带、高寒带）２０个样点进行陆生等足类的调查采集，共发现陆生等足类１１科、２９属、７２种。由于各地带自然环境明显不同，造成了物种分布上的差异，其中热睡亚热睦区种类最多，分别为３８种和４７种，两地带物种共占总种数的８０％以上；曙带和温带地区仅发现９种，而高寒带由于平均气温在０℃以下，不利于陆生等足类的生存，故迄今仅发现２种。其区系特点为：（１）区系分布的地带性     

生态-经济发展情景下内蒙古宏观生态系统模拟与分析

内蒙古自治区是我国北方面积最大、种类最全的生态功能区,是我国北方的重要生态屏障,其宏观生态系统状况不仅关系民众生存和生计,而且关系华北、东北、西北乃至全国的生态安全。构建了1990、2000及2015年3期宏观生态系统格局与影响因子数据集;融合区域生态系统发展规划,设置了基准、生态-经济协同发展和生态-经济权衡发展三种情景;应用土地利用均衡分析模型,模拟了3种情景下2025年及2035年内蒙古六大类生态系统结构与空间格局变化。结果表明：在延续历史发展趋势的基准情景和注重经济发展的生态-经济权衡发展情景下,草地和农田生态系统在2035年均无法恢复至2000年的水平,宏观生态系统结构难以达到规划目标;在注重生态保育的生态-经济协同发展情景下,草地、森林与湿地生态系统面积增长较大,符合内蒙古构建中国北方生态屏障的战略定位。从空间上看,农田生态系统面积的减少主要集中在农牧交错带地区,该区域的退耕还草构成了草地生态系统增加的主要来源;草地生态系统面积扩张还分布在近十年来发生草地退化的区域,这与近年来通过实施"京津风沙源治理"、"草原奖补政策"等生态工程建设后内蒙古自治区原有退化的草地生态系统在逐渐恢复的趋势相吻合;森林生态系统面积增加主要集中分布在大兴安岭等几个植被恢复地;城市生态系统主要以原有城镇居民点为中心,在其周边区域呈扩散式增长,特别是在采矿场、工业用地、交通沿线附近城镇面积增加较为显著;荒漠生态系统的缩减主要发生在与其它生态系统的交界处,这与开发利用的便利性、原有生态系统的可开发潜力等密切相关。研究表明,生态-经济发展情景下的宏观生态系统的空间显性模拟是区域国土空间规划和可持续发展的重要科学依据。     

‘Venus trapped,Mars transits': Cu and Fe redox chemistry,cellular topography and in situ ligand binding in terrestrial isopod hepatopancreas

Woodlice efficiently sequester copper (Cu) in ‘cuprosomes'' within hepatopancreatic ‘S'' cells. Binuclear ‘B’ cells in the hepatopancreas form iron (Fe) deposits; these cells apparently undergo an apocrine secretory diurnal cycle linked to nocturnal feeding. Synchrotron-based µ-focus X-ray spectroscopy undertaken on thin sections was used to characterize the ligands binding Cu and Fe in S and B cells of Oniscus asellus (Isopoda). Main findings were: (i) morphometry confirmed a diurnal B-cell apocrine cycle; (ii) X-ray fluorescence (XRF) mapping indicated that Cu was co-distributed with sulfur (mainly in S cells), and Fe was co-distributed with phosphate (mainly in B cells); (iii) XRF mapping revealed an intimate morphological relationship between the basal regions of adjacent S and B cells; (iv) molecular modelling and Fourier transform analyses indicated that Cu in the reduced Cu⁺ state is mainly coordinated to thiol-rich ligands (Cu–S bond length 2.3 Å) in both cell types, while Fe in the oxidized Fe³⁺ state is predominantly oxygen coordinated (estimated Fe–O bond length of approx. 2 Å), with an outer shell of Fe scatterers at approximately 3.05 Å; and (v) no significant differences occur in Cu or Fe speciation at key nodes in the apocrine cycle. Findings imply that S and B cells form integrated unit-pairs; a functional role for secretions from these cellular units in the digestion of recalcitrant dietary components is hypothesized.     

Evaluating asymbiotic seed culture methods and establishing Disa (Orchidaceae) germinability in vitro: relationships, requirements and first-time reports

Many Disa species (80%) have not been germinated in vitro, fuelling conservation fears. Winter-rainfall species are typically germinable, whilst summer-rainfall species are exclusively intractable in vitro. We aimed to establish the in vitro germination requirements for previously ungerminated Disa species. Conventional asymbiotic seed culture protocols were reviewed and their efficacy in summer-rainfall Disa established. Mature seed was subjected to manipulations of media composition and viscosity, incubation temperature and illumination. Immature cultures were also established across four seed maturity classes. Four first-time germinations (D. cooperi, D. nervosa, D. pulchra and D. woodii) resulted from media with increased water availability. Germination rate (>12 weeks), percentage (<30%) and synchrony were not in accordance with values reported for winter-rainfall species (>80% germination in 8 weeks). Germination of immature seed under control conditions was similar to mature seed germination under modified conditions, but neither percentage approached the calculated germination potential (∼viability). Germination control in Disa is proposed as a trade-off between water availability and the presence of phyto-inhibitors in the environment of the embryo—two features typical of seeds exhibiting water-impermeable dormancy.     

Sedimentological evidence for rooting structures in the Early Devonian Anglo-Welsh Basin (UK), with speculation on their producers

Rooting structures preserved as casts in alluvial deposits of the Lower Devonian Lower Old Red Sandstone occur more extensively than previously thought in the Anglo-Welsh Basin. Two rooting structure morphotypes are identified: morphotype 1 being predominantly horizontal, and morphotype 2 comprising vertical forms. Both morphotypes taper along their length, are oval in cross-section, branch, and can be linear or sinuous. Fills are heterolithic in nature. The rooting structures are observed in sediments deposited in a wide variety of environments including both low-sinuosity within-channel bar-tops and accretionary bar surfaces (inclined-heterolithic stratification); accretionary banks of sinuous ephemeral channels (inclined-heterolithic stratification); floodplains (including margins of shallow floodplain ponds) of both ephemeral and perennial river channels, and well-developed calcic Vertisols. Although a vascular plant origin to the rooting structures cannot be discounted, there is circumstantial evidence that the structures were produced by the enigmatic Prototaxites, recently reinterpreted as a giant fungus. It is possible that they represent underground aggregates (rhizomorphs or cords) of hyphae involved in anchorage and nutrient foraging. Organic matter associated with biofilms and crusts is hypothesized as a source of nutrients for the presumed saprotroph.     

Viscosimetric studies on molecular weight fractions of fulvic and humic acids of aquatic,terrestrial and microbial origin

Summary Viscosities were investigated of solutions of fulvic and humic acid molecular weight fractions of aquatic, terrestrial and microbial origin. Aquatic fulvic and humic acid molecules were, at pH 7, more voluminous than other types of humic compounds of similar molecular weight. It would appear that in low molecular weight non-aquatic humic matter, more inter- than intra-molecular bonding is present, with increasing molecular weight the bonding becomes more intra-molecular. Differences between average molecular weight values as obtained by an ultrafiltration method (Amicon) and by viscosimetry ranged from –18.7 to 18.5%. The largest deviations were in the low molecular weight range (<5,500 daltons). Higher molecular weight humics (in particular humic acids) appeared to have a more elongated structure than lower molecular weight material (in particular fulvic acids). Indications were obtained that on hydration humic moleculars become more elongated.     

PO2 and pH changes in the retina of the crab Ocypode ryderi: evidence for aerobic glycolysis

Summary The isolated retina of the terrestrial crab Ocypode ryderi exhibits a pronounced lactate production in spite of being supplied with sufficient O₂ (140 torr). To determine whether this lactate production is caused by hypoxic areas in the tissue or represents aerobic glycolysis, oxygen partial pressure and pH measurements with two-channel glass microelectrodes and additional biochemical analyses were carried out on this organ. Distinct profiles were obtained for O₂ partial pressure and pH inside the tissue. At a depth of 200 m different O₂ partial pressure levels could be observed depending on the O₂ partial pressure in the medium (85 torr at 280 torr and 36 torr at 130 torr, respectively). The extracellular pH displays a similar pattern; it reaches a stable value of 7.15 at 100 m inside the tissue. Lowering bath O₂ partial pressure from 280 torr to about 15 torr (hypoxia) induces a decrease of the O₂ partial pressure in the tissue with different time-courses for different tissue depths. However, hypoxia did not change the extracellular pH. Addition of antimycin A (100 mol · 1^-1) to the medium abolishes the O₂ partial pressure gradient and the delayed recovery of the tissue O₂ partial pressure after hypoxia. These results and the biochemical data suggest that in the crab retina a high glycolytic activity occurs simultaneously with oxydative carbohydrate degradation (aerobic glycolysis).Abbreviations AEC Atkinson energy charge - DC bioelectric potential - dw dry weight - HEPES N-[2-Hydroxyethyl]piperazine-N-[2-ethanesulphonic acid] - PCO₂ carbon dioxide partial pressure - PO₂ oxygen partial pressure - P _tO₂ oxygen partial pressure inside the tissue - P _mO₂ oxygen partial pressure in the medium - pH_t pH inside the tissue - pH_m pH in the superfusion medium     

Maximum rooting depth of vegetation types at the global scale

The depth at which plants are able to grow roots has important implications for the whole ecosystem hydrological balance, as well as for carbon and nutrient cycling. Here we summarize what we know about the maximum rooting depth of species belonging to the major terrestrial biomes. We found 290 observations of maximum rooting depth in the literature which covered 253 woody and herbaceous species. Maximum rooting depth ranged from 0.3 m for some tundra species to 68 m for Boscia albitrunca in the central Kalahari; 194 species had roots at least 2 m deep, 50 species had roots at a depth of 5 m or more, and 22 species had roots as deep as 10 m or more. The average for the globe was 4.6±0.5 m. Maximum rooting depth by biome was 2.0±0.3 m for boreal forest. 2.1±0.2 m for cropland, 9.5±2.4 m for desert, 5.2±0.8 m for sclerophyllous shrubland and forest, 3.9±0.4 m for temperate coniferous forest, 2.9±0.2 m for temperate deciduous forest, 2.6±0.2 m for temperate grassland, 3.7±0.5 m for tropical deciduous forest, 7.3±2.8 m for tropical evergreen forest, 15.0±5.4 m for tropical grassland/savanna, and 0.5±0.1 m for tundra. Grouping all the species across biomes (except croplands) by three basic functional groups: trees, shrubs, and herbaceous plants, the maximum rooting depth was 7.0±1.2 m for trees, 5.1±0.8 m for shrubs, and 2.6±0.1 m for herbaceous plants. These data show that deep root habits are quite common in woody and herbaceous species across most of the terrestrial biomes, far deeper than the traditional view has held up to now. This finding has important implications for a better understanding of ecosystem function and its application in developing ecosystem models.     

Influence of vegetation and soil CO2 exchange on the concentration and stable oxygen isotope ratio of atmospheric CO2 within a Pinus resinosa canopy

Measurements were made of the concentration and stable oxygen isotopic ratio of carbon dioxide in air samples collected on a diurnal basis at two heights within a Pinus resinosa canopy. Large changes in CO₂ concentration and isotopic composition were observed during diurnal time courses on all three symple dates. In addition, there was strong vertical stratification in the forest canopy, with higher CO₂ concentrations and more negative ¹⁸O values observed closer to the soil surface. The observed daily increases in ¹⁸O values of forest CO₂ were dependent on relative humidity consistent with the modelled predictions of isotopic fractionation during photosynthetic gas exchange. During photosynthetic gas exchange, a portion of the CO₂ that enters the leaf and equilibrates with leaf water is not fixed and diffuses back out of the leaf with an altered oxygen isotopic ratio. The oxygen isotope ratio of CO₂ diffusing out of a leaf depends primarily on the ¹⁸O content of leaf water which changes in response to relative humidity. In contrast, soil respiration caused a decline in the ¹⁸O values of forest CO₂ at night, because CO₂ released from the soil has equilibrated with soil water which has a lower ¹⁸O content than leaf water. The observed relationship between diurnal changes in CO₂ concentration and oxygen isotopic composition in the forest environment were consistent with a gas mixing model that considered the relative magnitudes of CO₂ fluxes associated with photosynthesis, respiration and turbulent exchange between the forest and the bulk atmosphere.     

中国陆地生态系统对全球变化的敏感性研究

根据自然植被净第一性生产力综合模型和农业净第一性生产力模型计算了我国自然植被及农作物的净第一性生产力,结果表明:在所有可能的气候条件下,我国陆地生态系统的生产力表现出由东南向西北递减的趋势及明显的条带状分布,并在新疆地区形成明显的低值区。在年平均气温升高2℃且降水不变的情况下,湿润地区生产力增加幅度最大,约增加1～2tDW·hm~(-2)·a~(-1);在年平均气温升高2℃、年降水增加20％的情况下,干旱、半干旱地区生产力增加幅度最大,约增加0.5～3.0tDW·hm~(-2)·a~(-1);在年平均气温升高2℃、年降水减少20％的情况下,湿润地区生产力提高约0.5～1.0tDW·hm~(-2)·a~(-1),干旱、半干旱地区生产力降低约0.5～2.0tDW·hm~(-2)·a~(-1)。