Species differences in total and vertical distribution of branch- and tree-level leaf area for the five primary conifer species in Maine, USA

Vertical distribution of leaf area largely governs both tree structure and function. Models of this important tree attribute have been constructed for several commercially important conifers. However, a limited number of studies have compared alternative modeling techniques and inherent species differences. This study used several existing datasets for the five primary conifer species in Maine, namely balsam fir [Abies balsamea (L.) Mill.], northern white-cedar [Thuja occidentalis (L.)], eastern hemlock [Tsuga canadensis (L.) Carr.], eastern white pine [Pinus strobus (L.)], and red spruce [Picea rubens (Sarg.)] to examine species variation in total and vertical distribution of projected leaf area at the individual branch- and tree-levels. In addition, multiple methods for modeling the vertical distribution of leaf area were examined across the species. For a given branch diameter and location within the crown, eastern hemlock branches held the greatest amount of leaf area, followed by balsam fir, northern white-cedar, white pine, and red spruce. At the tree-level, eastern white pine held the greatest amount of leaf area followed by eastern hemlock, balsam fir, red spruce, and northern white-cedar for a given tree size. Across species, the two-parameter, right-truncated Weibull distribution performed the best for predicting vertical distribution of leaf area when compared to the four-parameter beta and Johnson's S_B distributions (reduction of root mean square error of 1.7–21.1%). Northern white-cedar had a relative distribution of leaf area distinctly different than other species in this study with a mode shifted towards the upper crown. In contrast to red spruce and white pine, the mode of the relative distribution of leaf area for balsam fir and eastern hemlock occurred lower in the crown. Results of this study suggest that differences in total and vertical distribution of leaf area exist between species, but significant amounts of their variation are largely accounted for by bole and crown size.     

Dry matter partitions and specific leaf weight of soybean change with tree competition in an intercropping system

In 2004 and 2005, the yield, leaf area, dry weight and dry weight partitions of soybeans were determined at the Agroforestry Research Site (ARS) (est. 1987, Ontario, Canada). Soybean was intercropped with poplar (Populus deltoides x nigra DN-177 L., 556 m³crown tree⁻¹), silver maple (Acer saccharinum L., 308 m³), black walnut (Juglans nigra L., 148 m³) and pecan (Carya illinoensis Wangenh., 114 m³), or grown alone (monoculture). Yield of soybean was not different in either year between the monoculture and the black walnut or pecan intercrops. In the poplar and silver maple treatments, yield was 66 and 85% (2004 and 2005) lower than in the monoculture. Despite the fact that different tree species were used, there was a significant negative linear regression between yield and tree crown volume (R ² = 0.76, P = 0.0049 and R ² = 0.93, P < 0.0001 in 2004 and 2005, respectively). With increasing tree crown volume, soybean tended to partition more dry matter to the photosynthetic and reproductive parts and less to structural tissue and petiole. This demonstrates the phenotypic flexibility of the crop component in agroforestry systems. Contrary to theoretical predictions, soybean leaves were thicker as shade increased (increase by 6.2 × 10⁻⁴–1.2 × 10⁻³ mg cm⁻², per unit of crown volume), pointing to competitive interactions specific to tree-based intercrops.     

能源植物麻疯树研究进展

本文主要概述了生物能源树种麻疯树近年国内外在资源分布、毒性和药理活性、生物农药活性、生物柴油、生理生态、培育等方面研究进展,并对其种子丰产技术进行了探讨。     

Nutrient cycle of planted forest of Pinus tabulaeformis in the Miyun Reservoir Watershed, Beijing

We studied the nutrient cycle of a planted forest of Pinus tabulaeformis in the Miyun Reservoir Watershed, Beijing. Results show that the total biomass of P. tabulaeformis stands at age 29 in the experimental area is 92627 kg/hm², and the total nutrient store is 695.17 kg/hm² including nitrogen (N), phosphorus (P), kalium (K), calium (Ca) and magnesium (Mg). The sequence of their contents in different organs was given as follows: needle>branch> trunk>root. The annual amount of 85.37 kg/hm² of five nutrient elements were assimilated by P. tabulaeformis, about 0.34% of the total store in soil, and 3.30% of available nutrient store in soil depth from 0 to 30 cm. The nutrient annual retention is 35.92 kg/hm², annual returning 49.46 kg/hm², the rain input 26.04 kg/hm² to the five nutrient elements. The parameter absorption coefficient, utilization coefficient, cycle coefficient and turnover period were cited to describe the nutrient elements cycle characteristic of the planted forest ecosystem of P. tabulaeformis. The absorption coefficient is the ratio of plant nutrient element content to soil nutrient element content, and its sequence of five nutrient elements was given as follows: N>P>K>Ca>Mg. Utilization coefficient is the ratio of the nutrient element annual uptake amount to the nutrient element storage in standing crops, and its sequence of five nutrient elements was: Mg>K> P>N>Ca. The big utilization coefficient means more nutrients stored in the plant. The cycle coefficient is the ratio of the nutrient element annual return amount to the nutrient element annual uptake amount, its sequence: Ca>N>P>K>Mg. Turnover period is the ratio of the nutrient storage in the crops to the annual returning, its sequence: Mg>K>P>N>Ca. __________ Translated from Journal of Beijing Forestry University, 2008, 30(3): 51–56 [译自: 北京林业大学学报]     

Direct plant regeneration from nodal explants of <Emphasis Type="Italic">Balanites aegyptiaca</Emphasis> L. (Del.): a valuable medicinal tree

This report describes in vitro shoot induction and plant regeneration from nodal segments of Balanites aegyptiaca on Murashige and Skoog (MS) medium fortified with 6-benzyladenine (BA), thidiazuron (TDZ) and kinetin (Kin) (0.5–20.0 μM). MS medium supplemented with BA (12.5 μM) was the most effective in inducing bud break and growth and also in initiating multiple shoot proliferation. However, the optimal level of TDZ supplementation to the culture medium was 5.0 μM. Shoot cultures were established by repeatedly subculturing the original nodal explants on the same medium. Highest number of shoots (11.5 ± 0.7) and shoot length (5.0 ± 0.2 cm) were achieved when cultures were subcultured on MS medium supplemented with 12.5 μM BA and 1.0 μM α-naphthalene acetic acid (NAA). The shoots regenerated from TDZ supplemented medium when subcultured to hormone free MS basal medium considerably increased the rate of shoot multiplication and shoot length by the end of fifth subculture. Rooting of the shoots was achieved on MS medium augmented with 1.0 μM indole-3-butyric acid (IBA) plus 0.5% activated charcoal followed by their transfer to half strength MS basal medium. The in vitro raised plantlets with well developed shoots and roots were successfully established in earthen pots containing garden soil and were grown in greenhouse with 70% survival rate. The results of this study provide the first successful report on in vitro direct plant regeneration of B. aegyptiaca.     

Baicalin suppresses expression of Chlamydia protease-like activity factor in Hep-2 cells infected by Chlamydia trachomatis

In this study, we tested the ability of Baicalin to block Chlamydia trachomatis infection and found that the Baicalin blocked infection of Hep-2 cells. Then, we looked into the expression of RFX5 and CPAF gene in Chlamydia-infected cells. We found that RFX5 and CPAF were up-regulated and down-regulated respectively by Baicalin. Since CPAF is responsible for degrading RFX5, we suggest that CPAF was a primary target of Baicalin and played an important role in regulating RFX5. Our findings demonstrate that Baicalin can inhibit C. trachomatis effectively and therefore, can be considered as potential agents for therapy of Chlamydia infectious diseases.     

麻栎资源研究进展及开发利用对策

麻栎是我国传统的优良硬阔叶用材树种,也是一种重要的能源树种。从地理分布、生物学特性、苗木培育、造林经营管理和加工利用等方面总结了我国麻栎的研究进展,探讨了麻栎资源培育和开发利用存在的问题和今后研究的发展方向。     

Effects of water stress on growth,dry matter allocation and water-use efficiency of a leguminous species, <Emphasis Type="Italic">Sophora davidii</Emphasis>

The adaptation responses to different water conditions and the drought tolerance of Sophora davidii seedlings were assessed in a greenhouse experiment. Two-month-old seedlings were subjected to the following water supplies for 95 days: 100, 80, 60, 40 and 20% of field water capacity. The seedlings at 100% FC had the greatest productivity, height, basal diameter, branch number, leaf number and leaf area. Water supply <80% FC was the threshold of drought-initiated negative effects on seedling growth, yield and physiological processes; these parameters were severely reduced at 20% FC, however, there was no plant death during the experiment. Moreover, water stress decreased leaf relative water content, specific leaf area, leaf area ratio, and water-use efficiency (WUE), whereas it increased the biomass allocation to roots, which resulted in a higher root:stem mass ratio under drought. The S. davidii seedlings tolerated drought by maintaining high leaf relative water content and by reducing branching and leaf expansion. However, low productivity and WUE at 20% FC suggested that seedlings did not produce high biomass under severe drought. Therefore, prior to introducing S. davidii in forestation efforts, a water supply >40% FC is recommended for seedlings to maintain growth and productivity. These results provide insights into limitations and opportunities for establishment of S. davidii in arid regions.     

树木挥发物对植食性昆虫的诱导抗性

树木挥发物质对植食性昆虫取食，产卵所产生的诱导抗性是树木与昆虫的长期协同进化过程中的必然结果，树木与植食性昆虫之间发展了一套互相调节，自身开拓资源，产生生存对策的复杂相互关系，本文着重阐明了树木与植食性昆虫的互相策略，诱导抗性的生物化学基础以及诱导抗性在调节植食性昆虫种群中的重要性。     

Coumarins from the aerial part of Halocnemum strobilaceum

Four known coumarins, coumarin (1), 7-hydroxy-3-methylcoumarin (2), oreoselone (3) and heraclenin (4), were isolated from aerial part of Halocnemum strobilaceum. Their structures were determined by 1 and 2-D NMR techniques.