Parameterization and testing of a biochemically based photosynthesis model for walnut (Juglans regia) trees and seedlings

The biochemically based leaf photosynthesis model proposed by Farquhar et al. (1980) and the stomatal conductance model proposed by Jarvis (1976) were parameterized for walnut. Responses of photosynthesis to CO(2) and irradiance were used to determine the key parameters of the photosynthesis model. Concurrently, stomatal conductance responses to leaf irradiance (Q), leaf temperature (T(l)), water vapor pressure deficit at the leaf surface (D), and air CO(2) concentration at the leaf surface (C(s)) were used to parameterize the stomatal conductance model. To test the generality of the model parameters, measurements were made on leaves from a 20-year-old tree growing in the field, and from sunlit and shaded greenhouse-grown seedlings. The three key parameters of the photosynthesis model (maximum carboxylation rate V(cmax), electron transport capacity J(max), and dark respiration rate R(d)) and the key parameter of the conductance model (reference stomatal conductance, g(sref)) were linearly correlated with the amount of leaf nitrogen per unit leaf area. Unique relationships could be used to describe nitrogen effects on these parameters for leaves from both the tree and the seedlings. Our data allowed separation of the effects of increasing total photosynthetic apparatus per unit leaf area from the effects of partitioning nitrogen among different pools of this apparatus for foliage acclimation to leaf irradiance. Strong correlations were found between stomatal conductance g(s) and Q, D and C(s), whereas the relationship between g(s) and T(l) was weak. Based on these parameterizations, the model adequately predicted leaf photosynthesis and stomatal conductance when tested with an independent set of data obtained for the tree and seedlings. Total light-driven electron flows derived from chlorophyll fluorescence data obtained at different leaf temperatures were consistent with values computed by the model. The model was also tested with branch bag data acquired from a three-year-old potted walnut tree. Despite a relatively large variance between observed and simulated values, the model predicted stomatal conductance and photosynthesis reasonably well at the branch scale. The results indicate that the photosynthesis-conductance model developed here is robust and can be applied to walnut trees and seedlings under various environmental conditions where water is non-limiting.     

油松高世代种子园营建技术

通过对3批142个油松优树半同胞子代进行测定,选出36个优良家系,树高、胸径、材积平均增产15.4%、26.9%、73.3%,遗传增益分别为8.2%、8.5%、22.2%;再从优良家系内选择263个优良单株,树高、胸径、材积平均增产27.2%、41.1%、125.9%,预期遗传增益分别为13.3%、11.7%、37.2%;用选出的优良单株营建高世代无性系种子园,并提出了高世代种子园建立技术和种子高产关键技术.     

Modeling annual production and carbon fluxes of a large managed temperate forest using forest inventories, satellite data and field measurements

We evaluated annual productivity and carbon fluxes over the Fontainebleau forest, a large heterogeneous forest region of 17,000 ha, in terms of species composition, canopy structure, stand age, soil type and water and mineral resources. The model is a physiological process-based forest ecosystem model coupled with an allocation model and a soil model. The simulations were done stand by stand, i.e., 2992 forest management units of simulation. Some input parameters that are spatially variable and to which the model is sensitive were calculated for each stand from forest inventory attributes, a network of 8800 soil pits, satellite data and field measurements. These parameters are: (1) vegetation attributes: species, age, height, maximal leaf area index of the year, aboveground biomass and foliar nitrogen content; and (2) soil attributes: available soil water capacity, soil depth and soil carbon content. Main outputs of the simulations are wood production and carbon fluxes on a daily to yearly basis. Results showed that the forest is a carbon sink, with a net ecosystem exchange of 371 g C m(-2) year(-1). Net primary productivity is estimated at 630 g C m(-2) year(-1) over the entire forest. Reasonably good agreement was found between simulated trunk relative growth rate (2.74%) and regional production estimated from the National Forest Inventory (IFN) (2.52%), as well as between simulated and measured annual wood production at the forest scale (about 71,000 and 68,000 m(3) year(-1), respectively). Results are discussed species by species.     

广东石门台自然保护区生态旅游开发探讨

发展生态旅游是当前自然保护区保护和发展的趋势,每个自然保护区应根据其具体特点来进行.分析广东石门台自然保护区面临的规划、开发、建设等主要问题,就发展生态旅游提出了相应的对策建议.     

香棕(山棕)的园林利用价值与保护的探讨

通过对香棕园林利用价值的探讨及资源状况调查 ,以期为保护和开发利用香棕 ,为美化、绿化、香化环境提供参考     

火炬松家系的早期生长及遗传分析初报

引自美国的7个火炬松家系的生长和遗传分析结果表明，苗期家系间的生长差异不显著，7年生幼林生长差异显著，且高生长与2、4年生存在极显著相关。火炬松的材积遗传力较高，综合材高、胸径和村积等性状选择出2个优良家系，其材积增益可达18.49％。     

Effect of Cropping System on Physical Properties of Clay Soil Under Intensive Rice Cultivation

Cropping systems are thought to alter soil quality in paddy rice fields. This study was conducted to quantify the long‐term effects of continuous crop production under different cropping systems with different crop rotations on physical properties of alluvial clay soil in the Mekong Delta, Vietnam. Soil samples were collected from four treatments: (i) traditional intensive rice monoculture with three rice crops per year (R–R–R); (ii) rotation with two rice crops and maize (R–M–R); (iii) rotation with two rice crops and mung bean (R–Mb–R); and (iv) rotation with one rice and two upland crops, mung bean and maize (R–Mb–M). We hypothesized that cropping systems with rotations of upland crops and their temporary beds improve the physical quality of paddy rice soil; hence, they are better options towards sustainable agriculture. Results show an improvement of soil physical quality for systems with two rice crops and one upland crop (R–M–R and R–Mb–R) and those with one rice crop with two upland crops (R–Mb–M) compared with intensive rice monoculture (R–R–R). This was translated in decreased bulk density and soil strength, increased soil organic carbon and total porosity, and higher aggregate stability index, plant‐available water capacity, and Dexter's S index, especially at depths of 10–20 and 20–30 cm. The systems with different upland crops (maize or mung bean) showed similar high physical quality improvement. To maintain soil quality in future seasons, introducing a cropping system with at least one upland crop in rotation with rice is recommended. Copyright © 2014 John Wiley & Sons, Ltd.     

小麦后移栽棉的氮肥、密度效应及器官建成动态研究

采用二次均匀设计，研究氮肥和密度对小麦后移栽棉皮棉产量及其它主要经济性状的影响，建立了产量等性状的二次模型，通过对产量模型的分析，提出小麦后移栽棉适宜的施氮量为２１０～２３０ｋｇ／ｈｍ２、密度为４．７５万～４．９０万株／ｈｍ２．同时建立了不同器官（如株高、总果枝等）的建成动态模型，并提出小麦后移栽棉不同生育阶段器官建成动态的合理指标     

亚硫酸氢钠在葡萄上的应用研究

不同浓度的NaHSO3在葡萄上的应用研究表明，以100ppm效果最佳。于浆果膨大期处理3次，能获得增产、优质和早熟的效果，这与NaHSO3能增加叶绿素含量、提高光合效率和增加果穗重密切相关。     

Lightning Protection Performance of Transmission Line with High Tower and Great Span

This paper studies lightning protection performance of transmission line with high tower and great span, and puts forward the lightning shielding model of transmission line with high tower and great span. The model simulates the developing process of lightning downward leader, and take the effect of upward leader to downward leader into account. Moreover, the model consider backward lightning , that is even downward leader have developed lower than transmission line, Which will be occur lightning line. Aim at a certain sea transmission line with great span, its lightning performance is calculated with regular method, EGM and the model. The results have been analysed and compared. Because of thinking over backward lightning , the model can be used for calculating lightning shield performance of all kinds of transmission lines.