四姑娘山国家级自然保护区岷江冷杉枯落物及土壤的持水能力研究

通过对四姑娘山国家级自然保护区岷江冷杉林地表土壤和林下枯落物的实验分析,得出四姑娘山自然保护区岷江冷杉林0～40cm深度的土壤层最大贮水量为1694.8 t/hm2,林下枯落物最大持水量为233 t/hm2。四姑娘山自然保护区岷江冷杉林土壤及枯落物持水的最大值为1927.8 t/hm2。     

Tamarix and Diorhabda Leaf Beetle Interactions: Implications for Tamarix Water Use and Riparian Habitat

Tamarix leaf beetles (Diorhabda carinulata) have been widely released on western United States rivers to control introduced shrubs in the genus Tamarix, with the goals of saving water through removal of an assumed high water‐use plant, and of improving habitat value by removing a competitor of native riparian trees. We review recent studies addressing three questions: (1) to what extent are Tamarix weakened or killed by recurrent cycles of defoliation; (2) can significant water salvage be expected from defoliation; and (3) what are the effects of defoliation on riparian ecology, particularly on avian habit? Defoliation has been patchy at many sites, and shrubs at some sites recover each year even after multiple years of defoliation. Tamarix evapotranspiration (ET) is much lower than originally assumed in estimates of potential water savings, and are the same or lower than possible replacement plants. There is concern that the endangered southwestern willow flycatcher (Empidonax trailli extimus) will be negatively affected by defoliation because the birds build nests early in the season when Tamarix is still green, but are still on their nests during the period of summer defoliation. Affected river systems will require continued monitoring and development of adaptive management practices to maintain or enhance riparian habitat values. Multiplatform remote sensing methods are playing an essential role in monitoring defoliation and rates of ET on affected river systems.     

武汉市主要绿化树种滞尘效应研究

本实验对武汉市城区主干道主要绿化树种的滞尘效应与叶表面结构进行了研究。结果表明：（1）同一尘源条件下，不同树种的滞尘能力差异显著。乔木中悬铃木滞尘能力较高，可达6.9345 g/m²；小乔木中紫薇和紫叶李是滞尘能力较高的树种，滞尘能力分别为1.9543 g/m²和1.8790 g/m²；灌木中红花檵木和杜鹃等有较强的滞尘能力，分别可达4.0373 g/m²和3.8875 g/m²；（2）利用扫描电镜观察叶表面结构发现：叶表具毛被、褶皱、较深的不规则网格等特征的树种滞尘能力较高，叶表平滑或叶表网格结构规则且较浅时滞尘能力较低；（3）同一树种在不同的尘源条件下滞尘能力差异显著，空气中颗粒物浓度越高，滞尘能力也越大。以车流量近似模拟尘源条件表明，滞尘能力与车流量呈正相关。     

酸雨对水稻不同生育期叶片叶绿体ATP酶的影响

酸雨对植物生长发育具有显著影响。然而,不同生长阶段植物对逆境胁迫的响应存在差异。以模拟酸雨胁迫水稻(Oryza sativa)(孕穗期、灌浆期),利用植物生理生化方法测定了水稻叶肉细胞叶绿体Mg2+-ATPase活性及其基因表达量、光合磷酸化活性、ATP含量、植株相对生长速率(RGR)和叶片净光合速率(Pn),研究酸雨胁迫下孕穗期、灌浆期水稻叶绿体ATP酶的变化及其对植物光合作用影响的机理。结果表明,p H=4.5酸雨使孕穗期水稻RGR、Pn、叶片ATP质量比和光合磷酸化活性均显著提高,灌浆期上述指标变化不明显;p H=3.5和p H=2.5酸雨使上述指标均下降,且随酸雨p H值降低,变幅增加。p H=4.5酸雨使孕穗期、灌浆期水稻ATP合酶基因表达量及Mg2+-ATPase活性升高;p H=3.5和p H=2.5的酸雨使孕穗期、灌浆期水稻ATP酶基因表达量减少,造成Mg2+-ATPase活性降低,且随酸雨p H值降低变幅增加。可以认为,酸雨通过影响ATP酶转录水平,改变Mg2+-ATPase活性、光合磷酸化活性和叶片ATP质量比,进而影响Pn,并最终影响植物生长发育。酸雨胁迫对孕穗期水稻生长发育及光合作用有低促高抑的剂量效应,而低强度酸雨对灌浆期水稻影响不明显。与灌浆期相比,孕穗期对酸雨胁迫较敏感,表明植物不同生长发育阶段对酸雨胁迫响应存在差异,此发现应成为评价酸雨影响植物的一个因素。     

Competition of Hydrogen and Manganese Ions for Adsorption Sites in Sitka Spruce Litter

The competition of hydrogen and manganese ions for adsorption sites in Sitka spruce litter was investigated in a factorial design, simulated acid rain experiment, which involved leaching of litter with simulated throughfall solutions at three pH levels (5.3, 4.3 and 3.3) and three manganese concentrations (0 to 0.2 mg1^-1). the throughfall solution at the lowest pH was the most efficient in removing exchangeable manganese from litter. the manganese concentration in the leachates was approximately proportional to the hydrogen ion concentration in the simulated throughfall solution. Under field conditions, throughfall manganese concentration also naturally tends to increase as a consequence of enhanced foliar leaching of manganese in response to increasing precipitation acidity. the manganese concentration in the simulated throughfall also affected manganese concentration in the leachates, however, and contributed to a buildup of exchangeable manganese in litter, thus counteracting to some extent possible adverse effects of excess leaching due to increased throughfall acidity.     

Challenges to Introducing and Managing Disturbance Regimes for Holocarpha macradenia, an Endangered Annual Grassland Forb

Abstract:  Introducing rare plants to new sites for conservation to offset effects of habitat destruction requires detailed knowledge of habitat requirements, plant demography, and management needs. We conducted a factorial experiment replicated at three coastal prairie sites to test the effects of clipping frequency and litter accumulation on seed germination, seedling survival, reproduction, and seedling recruitment of introduced populations of the endangered, tall-stature, annual forb, Holocarpha macradenia (DC.) E. Greene. Clipping favored H. macradenia , primarily by enhancing seed germination and flower production. Litter accumulation had no effect on seed germination, even after 5 years of treatments. Seedling recruitment was highly site specific with large numbers of recruits recorded at only one of three sites. Although recruitment of seedlings was higher in clipped plots for 2–3 years, by 4–5 years after introduction very few seedlings survived to reproduction in any treatment. We attribute this result to a combination of poor habitat quality, small population size, and lack of a seed bank. We were unsuccessful in introducing this relatively well-studied species of concern to apparently suitable habitat at multiple sites in multiple years, which suggests that translocating rare plant populations to mitigate for habitat destruction is an expensive and highly uncertain endeavor.     

Microscale Spatial Variation in Forest Litter Phytotoxicity

The spatial variation (within a 100 × 100 m plot) in the pollution of forest litter with heavy metals (Cu, Cd, Pb, and Zn), its acidity, and phytotoxicity (measured by the results of the root test using seedlings from a genetically homogeneous sample of common dandelion (Taraxacum officinale s.l.) have been estimated. Forest litter has been sampled in three zones differing in the toxic impact of long-term polymetal pollution by emissions from a copper-smelting plant emissions in the Middle Urals. The phytotoxicity variation is maximum in a moderately polluted plot, where both very high and very low pollution levels were observed, which determines a substantially nonlinear dose–effect relationship. The litter phytotoxicity is mainly accounted for by exchangeable forms of metals. Biological testing of samples from the most polluted plot has demonstrated marked antagonism between heavy metals and acidity.     

Characteristics of Cajander Larch (<Emphasis Type="Italic">Larix cajanderi</Emphasis> Mayr) on Dredging Waste Dumps in the Amur Region

Former dredging sites were studied in the taiga zone of the Amur region (in Khabarovsk Krai). The involvement of Larix cajanderi in plant succession on dredging waste dumps was revealed. Some morphological-anatomical parameters of L. cajanderi needles were compared in trees growing on the dumps and in adjacent open larch stands on waterlogged peaty soils.__________Translated from Ekologiya, No. 4, 2005, pp. 259–263.Original Russian Text Copyright © 2005 by Osipov, Burundukova.     

Ozone Deposition at a Forest Site in NE Bavaria

The dry deposition of ozone to aconiferous forest in northeastern Bavaria(southern Germany) was quantified during 1999with both the eddy correlation method and a bigleaf model. The model included parameterizationsof the atmospheric transfer resistances fromdirect measurements, stomatal resistance from aplant ecological model, and an estimation of thecuticle resistance as function of leaf wetness.Early in the season, the measured and themodelled deposition fluxes were in goodagreement, although the modelled fluxes tended tounderestimate the measured ones. Thisunderestimation was more pronounced in the latesummer, when high nocturnal fluxes werefrequently measured. The model parameterizationof the cuticle and the stomatal resistances didnot allow for such high fluxes. In these cases,the 24 hour average of the measured fluxes wereup to 4.5 times higher than the modelled ones.The reasons for these large discrepancies remainunknown. However, assigning the unaccounted partof the deposition to a nonstomatal surfacedeposition pathway, a new parameterization of therespective resistance yielded an average value of300 s m^-1. It exhibited a decreasing trendthrough the vegetation period.     

鼎湖山主要森林生态系统地表N_2O通量

利用静态箱-气相色谱法对鼎湖山3 种处于演替不同阶段的森林类型(季风常绿阔叶林、针阔叶混交林和马尾松林)的地表N2O 通量进行了 1 年的原位观测和研究.结果表明,3 种林型地表 N2O 通量按从大到小的顺序为:季风林>混交林>松林;不同林型间的 N2O 通量差异与森林土壤的性质有密切关系,C/N 比值较低的季风林凋落叶对土壤中产生N2O 的微生物过程有较为明显的促进作用;从全年来看,松林地表N2O 通量的季节变化不明显,而季风林和混交林的地表 N2O 通量在雨季存在明显的降雨驱动效应,统计分析显示在该地区影响森林地表N2O 通量的主要因子是土壤湿度.