东北几个树种苗木的休眠深度

温带树木通常在秋季停止生长,形成顶芽、落叶,进入冬季休眠状态,翌春再恢复生长,这样周而复始。一般认为这是它们对温带气候季节性节律的一种适应。休眠状态一方面有利于树木度过寒冷而干燥的冬天,同时也为第二年的生长做好准备。但温带树木的休眠实际上存在着几个阶段或几种状态。例如顶芽多在7—8月形成。形成之初如摘去叶片或给以长日照,则顶芽将在当年重新萌动。侧芽形成得更早。在侧芽形成之初如摘去枝顶将刺激侧芽在当年萌动。这时的休眠可称之为相关抑制。芽形成后再过一个时期,这种处理就越来     

Acclimation to high irradiance in temperate deciduous trees in the field: changes in xanthophyll cycle pool size and in photosynthetic capacity along a canopy light gradient

To test the hypothesis that in temperate deciduous trees acclimation to potentially damaging high irradiances occurs via long-term adjustments in foliar photosynthetic capacity, and short-term changes in xanthophyll cycle pool size in response to weather fluctuations, nitrogen concentration and pigment composition were examined along a canopy light gradient in three species –Betula pendula, Populus tremula and Tilia cordata (from most shade intolerant to tolerant), and foliage photosynthetic potentials in P. tremula and T. cordata. Integrated quantum flux density (Q_i) incident on leaves was estimated with a method combining hemispherical photography and light measurements with quantum sensors made over the growing season. Long- and short-term light indices – average total seasonal daily integrated quantum flux density (T_s, mol m^–2 d^–1) and that of the 3 d preceding foliage sampling (T_3d) – were calculated for each sampled leaf. In addition to total integrated quantum flux density, the part of Q_i attributable to direct flux was also computed. Strong linear relationships between the capacity for photosynthetic electron transport per area (J^a_max), estimated from in situ measurements of effective quantum yield of photosystem II (PS II), and Q_i averaged over the season and over the preceding 3 d were found for all studied species. However, the major determinant of J^a_max, the product of electron transport capacity per leaf dry mass (J^m_max) and leaf dry mass per area (M_A), was M_A rather than J^m_max, which was relatively constant along the light gradient. There was evidence that J^a_max is more tightly related to T_s, which characterizes the light climate during foliar development, than to short-term integrated light, possibly because there is little flexibility in adjustments in M_A after the completion of foliar growth. Leaf chlorophyll concentrations and the investment of leaf nitrogen in chlorophyll (Chl/N) were negatively related to Q_i– an investment pattern which improves light harvesting in low light. Xanthophyll cycle pool size (VAZ, violaxanthin + antheraxanthin + zeaxanthin) either expressed per unit chlorophyll (VAZ/Chl) or as a fraction of total carotenoids (VAZ/Car) increased with increasing Q_i in all species. However, contrary to J^a_max, it tended to correlate more strongly with short-term than with long-term average integrated light. There were few interspecific differences in J^a_max, Chl/N, VAZ/Chl and VAZ/Car when the variability in light level incident to the leaves was accounted for, indicating that the foliage of both shade-intolerant and -tolerant temperate tree species possesses considerable phenotypic flexibility. Collectively these results support the view that rapid adjustment of the xanthophyll cycle pool size provides an important means for acclimation to light fluctuations in a time scale of days, during which the potential for photosynthetic quenching of excitation energy is not likely to change appreciably.     

Danish deciduous forest types

In this study, the first comprehensive multivariate statistical analysis of Danish native forest vegetation, based on 1768 sample plots, is presented. Data were composed of data from literature sources and newly collected data. A series of cluster analyses resulted in 24 forest community types, grouped in beech (Fagus sylvatica), oak (Quercus robur-Q. petraea), hornbeam (Carpinus betulus), alder-ash (Alnus-Fraxinus) and lime (Tilia cordata, T. platyphyllos) types, in addition to mixed forest communities with several co-dominant tree species. The described communities are provisionally arranged syntaxonomically, when possible, according to the international phytosociological system. The distribution of ecological indicator values of pH, soil moisture and nitrogen is gradual in relation to the perceived plant communities. Many forest types, such as beech and oak dominated types, obtain indicated values for pH that span most of the indicated gradient. It is suggested that natural Danish forests probably would be composed of a multitude of canopy forming tree species. The present stands with one or a few tree species forming the canopy is the result of long anthropogenic influence and selective logging.     

六盘山辽东栎、少脉椴天然次生林夏季蒸散研究

2004年8～9月份,利用热扩散技术,结合微型蒸渗仪和水文学方法,研究了辽东栎、少脉椴次生林蒸散组成及其与林分结构的关系.结果表明,辽东栎和少脉椴树干的液流密度在"相对静止期"内比较稳定和微弱,其值在0.05μl·cm^-2·min^-1以下;在"活跃期"内树干液流密度上升较快,并呈单峰、双峰或多峰曲线,其值在0.25μl·cm^-2·min^-1以下;两树种单株蒸腾量有明显的种间差异,前者晴天和阴雨天单株蒸腾量分别为5.31和2.48 L·d^-1,为后者的2.3倍和3.75倍.林下灰_栒子和黄刺玫蒸腾速率日均值接近,分别为0.331和0.321 g·g^-1·h^-1.次生林日均蒸散量1.4 mm·d^-1,其中蒸腾量0.72 mm·d^-1、土壤蒸发量0.19 mm·d^-1、林冠截留量0.4 mm·d^-1,各占总量的49.6%、13.3%和37.1%.乔、灌木树种组成对次生林蒸腾量影响的表现不同,前者表现为个体蒸腾量的种间差异,而后者取决于单位林地面积上各树种的叶量.乔木层、灌木层和草本层(含土壤层)日均蒸散量分别为0.96、0.30和0.19 mm·d^-1,各占总量的65.8%、20.9%和13.3%,说明乔木层对林分日蒸散量大小起主要作用,灌木层次之,草本和土壤蒸发量的贡献最小.     

Hydraulic Conductance and Stomatal Sensitivity to Changes of Leaf Water Status in Six Deciduous Tree Species

The relationship between shoot hydraulic conductance (L) and stomatal sensitivity to changes in leaf water status was studied in the saplings of six deciduous tree species. L increased significantly in sequence: Acer platanoides < Tilia Cordata < Padus avium = Quercus robur < Salix caprea = Populus tremula. L was higher in the trees grown in soil with a higher nitrogen content and lower in the trees grown under mild water stress or kept in darkness for several days. L was higher in July than in September in all the species. L correlated positively with maximum photosynthesis, stomatal conductance and stomatal sensitivity to an increase in leaf water potential, but negatively with stomatal sensitivity to a decrease in leaf water potential. The correlations between L and any other parameter were approximated by three different curves: data for water-stressed plants fit to the first, data for plants kept in darkness fit to the second and all the other data fit to the third curve. The reasons of the differences of shoot hydraulic conductance in the different experimental sets and the mechanisms which may cause the correlation between L and the other characteristics are discussed.     

Evaluation of the enzymes involved in primary nitrogen metabolism in Tilia platyphyllos-Tuber borchii ectomycorrhizae

No information is available about Tuber borchii Vittad. ammonium metabolism during its life cycle, which involves the succession of three distinct phases. In this direction, the levels of glutamine synthetase (GS; EC 6.3.1.2), glutamate synthase (GOGAT; EC 1.4.1.13-14) and glutamate dehydrogenase (GDH; EC 1.4.1.2-4) were evaluated in Tilia platyphyllos Scop.-Tuber borchii Vittad. ectomycorrhizae, free living mycelium and non-inoculated roots. In the plant roots, GS shows high specific activity and only NADH-GDH (EC 1.4.1.2) is detectable; on the other hand, in free living mycelium GS and NADPH-GDH (EC 1.4.1.4) can be detected. Ectomycorrhizal metabolism was found to be deeply influenced by the two symbiotic partners. In fact, GS and both forms of GDH are present and their specific activities are higher than those found in the plant root and in the mycelial cells.     

安徽皇藏峪自然保护区南京椴种群结构分析

在野外样方调查基础上,根据径级结构、静态生命表、存活曲线和死亡曲线,探讨了安徽皇藏峪自然保护区内南京椴(Tilia miqueliana Maxim.)种群的动态变化规律及更新方式。结果表明,该种群的径级结构呈倒金字塔型,为衰退型种群;种群的存活曲线为DeeveyⅢ型曲线,幼树死亡率较高,苗期种群不稳定;其更新方式主要为实生苗和萌蘖,其中萌蘖是维持种群个体数量的主要方式。     

不同栽植方式下紫椴幼苗生物量分配及资源利用分析

 通过紫椴（Tilia amurensis Rupr.）幼苗在不同植距下纯栽和与落叶松(Larix gmelini)的混栽沙培试验,初次应用通径分析,研究紫椴幼苗生物量分配和资源利用机制,分析种内和种间竞争及其模式。研究发现总体上植距增大有利于紫椴根、茎、叶各器官的生长。通过通径分析说明,紫椴地下根系对总生长的贡献为0.236 1～0.286 9,地上茎、叶对总生长的贡献为0.732 5～0.775 8,地上部分的贡献是地下根系的2.95倍。表明紫椴幼苗对光具有较强的需求和竞争能力。紫椴和落叶松之间存在悬殊较大的生物量差距,落叶松的根、茎、叶生物量约是相应混栽紫椴的2、5、4倍。通过比较纯栽和混栽试验中的直接通径系数,与落叶松混栽后,紫椴对地下水分养分的竞争下降36.84%,对地上光照空间的竞争增大11.63%。随植距减小落叶松对紫椴的影响增大,紫椴根系生长受落叶松种间竞争影响不显著;地上茎、叶生长只在一定植距范围内受落叶松影响。紫椴与落叶松种间竞争是不同资源利用等级的两树种间的相互作用,以对称性地下竞争与落叶松“平等”地占有地下水分养分资源,从而受落叶松地下竞争较小;在一定空间范围内落叶松以非对称性竞争优先占有地上光照资源影响紫椴生长。