Effects of crown development on leaf irradiance,leaf morphology and photosynthetic capacity in a peach tree

The three-dimensional (3-D) architecture of a peach tree (Prunus persica L. Batsch) growing in an orchard near Avignon, France, was digitized in April 1999 and again four weeks later in May 1999 to quantify increases in leaf area and crown volume as shoots developed. A 3-D model of radiation transfer was used to determine effects of changes in leaf area density and canopy volume on the spatial distribution of absorbed quantum irradiance (PAR(a)). Effects of changes in PAR(a) on leaf morphological and physiological properties were determined. Leaf mass per unit area (M(a)) and leaf nitrogen concentration per unit leaf area (N(a)) were both nonlinearly related to PAR(a), and there was a weak linear relationship between leaf nitrogen concentration per unit leaf mass (N(m)) and PAR(a). Photosynthetic capacity, defined as maximal rates of ribulose-1,5-bisphosphate carboxylase (Rubisco) carboxylation (V(cmax)) and electron transport (J(max)), was measured on leaf samples representing sunlit and shaded micro-environments at the same time that the tree crown was digitized. Both V(cmax) and J(max) were linearly related to N(a) during May, but not in April when the range of N(a) was low. Photosynthetic capacity per unit N(a) appeared to decline between April and May. Variability in leaf nitrogen partitioning between Rubisco carboxylation and electron transport was small, and the partitioning coefficients were unrelated to N(a). Spatial variability in photosynthetic capacity resulted from acclimation to varying PAR(a) as the crown developed, and acclimation was driven principally by changes in M(a) rather than the amount or partitioning of leaf nitrogen.     

柳树造纸及矿柱用材优良无性系选育

柳树速生，产量高，成材期短。木材密度中等，有较高的冲击韧性、抗压及抗弯强度等特性，是良好的造纸用材，作小径级矿柱材也是合适的。根据造纸及矿柱用材的需要，选育出苏柳７９９、苏柳７９５和苏柳９０３三个优良无性系。     

石灰岩土壤特点及对淡竹的影响

利用６０块标准地资料。动用数理统计方法，研究了石灰岩土壤的特点及土壤因子对淡竹生长的影响。研究表明：石灰岩土壤的主要特点是ＰＨ值偏高，盐基和Ｎ含量丰富，特别是Ｃａ含量高。土壤和因子对淡竹的综合影响很大，可以根据土壤的肥力状况来预测淡竹的生长情况，但不同的肥力因子对淡竹的影响程度不同；土壤特殊因子对淡竹的高、径和竹壁厚度影响较大，但对枝下高的影响不显著，不同的特殊因子对淡竹的作用没。     

原条造材优化设计的遗传算法

本文首次应用遗传算法对原条造材进行优化设计。每个可能造出原木段为变量x_i,以造出各种规格材累计价值为目标函数值,当满足各种约束条件时目标函数值最大的造材方案为优化方案,算法设计运行结果表明该方法优化造材效果极为理想。     

Sudden increase in atmospheric CO2 concentration reveals strong coupling between shoot carbon uptake and root nutrient uptake in young walnut trees

We studied the short-term (i.e., a few days) effect of a sudden increase in CO2 uptake by shoots on nutrient (NO3-, P ion, K+, Ca2+ and Mg2+) uptake by roots during vegetative growth of young walnut (Juglans nigra x J. major L.) trees. The increase in CO2 uptake was induced by a sudden increase in atmospheric CO2 concentration ([CO2]). Twelve 2-year-old trees were transplanted and grown in perlite-filled pots in a greenhouse. Rates of CO2 uptake and water loss by individual trees were determined by a branch bag method from 3 days before until 6 days after [CO2] was increased. Nutrient uptake rates were measured concurrently by a hydroponic recirculating nutrient solution system that provided non-limiting supplies of water and nutrients. Six control trees were kept in ambient [CO2] (360 ppm), and [CO2] was increased to 550 ppm for one set of three trees and to 800 ppm for another set of three trees. Before imposing the elevated [CO2] treatments, all trees exhibited similar daily water loss, CO2 uptake and nutrient uptake rates when expressed per unit leaf area to account for the tree size effect. Daily water loss rates were only slightly affected by elevated [CO2]. Carbon dioxide uptake rates greatly increased with increasing atmospheric [CO2], and nutrient uptake rates were proportional to CO2 uptake rates during the study period, except for P ion. Our results show that, despite the important carbon and nitrogen storage capacities previously observed in young walnut trees, nutrient uptake by roots is strongly coupled to carbon uptake by shoots over periods of a few days.     

Using a chain of models to simulate the distribution between quality clusters of a set of boards coming from a sessile oak (<Emphasis Type="Italic">Quercus petraea</Emphasis> Liebl.) resource. Validation of the simulations

Taking sessile oak as an example, this paper initially presents a method to predict the final production (quantity and quality) coming from a forest resource when two sets of data are available. The data sets are from two models: measured or simulated ring width profiles from pith to bark of the constituent trees as well as a mixed model for the basic wood properties which are used to grade the boards into quality clusters. The second part of the paper contains a validation for the proposed method. Simulations are used to predict two basic wood properties (volumetric swelling coefficient and wood density) in the trees of a forest resource in relation to the ring width profile of each tree. The simulations are used to compute a map of these two basic properties in each plank derived from the trees. A quality index derived from this map of basic wood properties in the boards is then used to allocate the planks to quality clusters. The basic wood properties considered in this paper are modelled with linear mixed models. Since computation of the plank properties or definition of the grading rule can use several properties simultaneously, the models used to simulate the basic properties are joint models. Modelling jointly several properties with a mixed model consists of defining a covariance structure between the random effects of the model. Such a model can be substantial in terms of parameters and computational resources required, thus we compared three kinds of joint models. The simplest one is not quite a joint model but is simply obtained from the juxtaposition of independent models, one for each of the two properties taken into consideration. We also defined a model with a moderate covariance structure between the two properties, and lastly, we used a third model with a full covariance structure. Simulations of volumetric swelling coefficient, wood density and the resulting board grading were carried out with each of these three models. All give results roughly in accordance with the observations, but the two truly joint models give better results than the simplest model.     

The role of saltbushes (Atriplex spp.) in arid land rehabilitation in the Mediterranean Basin: a review

Arid lands in the Mediterranean Basin harbour populations of saltbushes over substantial areas. These have been grazed for centuries and often cleared. There are also some 100,000 hectares of artificially established saltbushes, both native and exotic; they include no more than half a dozen species, when large scale plantations are concerned. Another dozen of exotic species, introduced from Australia, Southern and Northern America, have successfully undergone field trials and could be used on a large scale in a near future. The present paper attempts to review the current state of knowledge on Atriplex spp. in the Mediterranean Basin as a means of Arid Land rehabilitation at a time where huge areas in the region have undergone processes of severe degradation or have been subjected to desertization, particularly over the past four decades. In spite of a number of constraints in their establishment, management and utilization, the plantation of Atriplex spp. appears as one of the best way, if not the best one, to rehabilitate desertized areas and restore them to production, under the present state of knowledge on arid land rehabilitation. They, in particular, are amenable to inclusion into new, man-made agro-sylvo-pastoral systems of production well adapted to arid lands and to the needs of their populations.     

Remote sensing in plant diseases using infrared colour aerial photography: applications trials in the Ivory Coast to root diseases of Hevea brasiliensis1

In spite of numerous aeroplane flights and different incerpretations of the infrared colour photographs obtained, the remote sensing of root rotting fungi of rubber tree has failed in practice in the Ivory Coast. The reasons for this failure and conclusions on the efficiency of this method are discussed.     

油松针叶束繁殖研究

以当年生针叶为材料,对影响针叶束生根的冷藏时间、采叶时间、采叶部位、切基与否、培养温度状况、激素处理、培养液成分等因素进行研究。结果表明:在陕西关中地区,油松针叶束培养较适宜的采叶时间在11~12月份,以采当年生枝条中下部的粗壮针叶为好;采叶后冷藏30 d,有利于生根;在培养前进行切基处理生根效果更好;培养时保持温度的相对稳定对针叶束生根极为有利。油松针叶束水培生根的适宜激素类型及其处理方式为:IBA+IAA(1∶1)以150 mg/L的浓度处理24 h;适宜的培养液成分及其浓度为硼酸45~60 mg/L+维生素B15~7 mg/L+硝酸铵30 mg/L+磷酸二氢钾20 mg/L。     

Spatial and temporal variations in leaf area index, specific leaf area and leaf nitrogen of two co-occurring savanna tree species

Foliage growth, mass- and area-based leaf nitrogen concentrations (Nm and N a) and specific leaf area (SLA) were surveyed during a complete vegetation cycle for two co-occurring savanna tree species: Crossopteryx febrifuga (Afzel. ex G. Don) Benth. and Cussonia arborea A. Rich. The study was conducted in the natural reserve of Lamto, Ivory Coast, on isolated and clumped trees. Leaf flush occurred before the beginning of the rainy season. Maximum leaf area index (LAI), computed on a projected canopy basis for individual trees, was similar (mean of about 4) for both species. Seasonal courses of the ratio of actual to maximum LAI were similar for individuals of the same species, but differed between species. For C. febrifuga, clumped trees reached their maximum LAI before isolated trees. The LAI of C. arborea trees did not differ between clumped and isolated individuals, but maximum LAI was reached about 2 months later than for C. febrifuga. Leaf fall was associated with decreasing soil water content for C. arborea. For C. febrifuga, leaf fall started before the end of the rainy period and was independent of changes in soil water content. These features lead to a partial niche separation in time for light resource acquisition between the two species. Although Nm, N a and SLA decreased with time, SLA and N a decreased later in the vegetation cycle for C. arborea than for C. febrifuga. For both species, N a decreased and SLA increased with decreasing leaf irradiance within the canopy, although effects of light on leaf characteristics did not differ between isolated and clumped trees. Given relationships between N a and photosynthetic capacities previously reported for these species, our results show that C. arborea exhibits higher photosynthetic capacity than C. febrifuga during most of the vegetation cycle and at all irradiances.