Altitudinal and longitudinal variations in Pinus brutia (Ten.) of Crete Island,Greece: some needle,cone and seed traits under natural habitats

Four populations representing the entire natural distribution range of Pinus brutia (Ten.) in Crete (Greece) were sampled to determine: (1) Altitudinal variation within populations of Lassithi, Vorizia, Koustagerako, and Samaria, and; (2) Longitudinal variation among the four populations, based on morphological and anatomical differences in cone, needle and seed characteristics. Samples were collected from 10 trees per altitude, at three altitudes in each population. A total of 12 morphological and anatomical traits from needles, cones and seeds were analyzed to assess the altitudinal and longitudinal variations of the species in the island. The number of teeth per cm showed significant (P<0.01) differences between altitudes in Samaria, Vorizia and Lassithi, while needle length, width and the number of resin canals showed significant differences (P<0.01) between altitudes in Koustagerako. Cone width showed patterns of variation along the altitudinal gradient in Koustagerako, Samaria and Vorizia. Most traits had their highest means at the middle altitudes (650masl) in all the four populations. Overall, no clear altitudinal differentiation was detected, probably due to high rate of gene flow. Longitudinal variability showed a clear pattern of differentiation along the east–west climatic gradient. Needle length, width, sheath length, number of teeth per cm and the number of resin canals were the most useful traits for determining the climatic gradient clines.     

用热扩散式茎流计测定园林树木蒸腾耗水量

采用热扩散式边材液流探针和环境自动监测系统对北京3种园林树木的树干液流及主要环境因子进行了一个生长季的同步观测.结果表明,3树种树干液流的日变化呈明显的单峰曲线,晴天的液流速率大于多云天和阴天,紫叶李和悬铃木的日耗水量明显大于元宝枫;对不同天气3树种每h的液流速率与相应的环境因子进行逐步回归分析.结果显示,影响3树种液流速率的主要环境因子是空气温度、空气相对湿度、辐射强度和5 cm土层温度,在不同天气里起主导作用的因子不同,环境因子与树干液流之间的数量关系能较好地预测树木的蒸腾耗水量.     

Defining competition vectors in a temperate alley cropping system in the midwestern USA: 2. Competition for water

A study was carried out in an alley cropping system in the Eastern Maize Belt of the United States with the objective of quantifying the competition for water between trees (black walnut (Juglans nigra L.) and red oak (Quercus rubra L.) and maize (Zea mays L.). Spatial and temporal variation in soil moisture, tree and maize rooting patterns, tree and maize water uptake, and maize leaf area expansion were determined in three treatments; barrier (polyethylene root barriers separating maize and tree roots), trench (trenching without a polyethylene barrier), and no barrier (control). Significant temporal variation in soil moisture was observed in both black walnut and red oak alley cropping systems. The barrier and trench treatments resulted in higher soil moisture in the maize alley and lower soil moisture in the tree row than the no barrier treatment. Uptake of water by maize was higher in the barrier than the no barrier treatment. However, tree water uptake was higher in the no barrier treatment than in the barrier treatment because tree roots utilized water from the maize alley. Maize leaf area was negatively impacted by water stress in the no barrier treatment. Quantification of rooting patterns revealed that maize and tree roots were concentrated in the top 30 cm soil layer where water fluctuations were greatest. The barrier and trench treatments successfully eliminated the belowground root competition between trees and maize and resulted in greater leaf area and higher grain yields than the no barrier treatment. Thus, competition for water rather than competition for light seems to be critical in defining the productivity and sustainability of this alley cropping system.This revised version was published online in November 2005 with corrections to the Cover Date.     

Spatially distributed morphological characteristics of macropores in forest soils of Hitachi Ohta Experimental Watershed, Japan

Morphological characteristics of macropores in forest soil profiles were investigated at Hitachi Ohta Experimental Watershed in Japan. Nine individual profiles at different locations (various spatial scales in a catchment) and twenty profiles at one site (a small spatial scale) were excavated to the bedrock to investigate density, origin, diameter, direction, and gradient of macropores. Macropore densities in a soil profile ranged from 3.5 to 29.1 per m and from 5.4 to 75.1 per m², respectively. Subsurface erosion, root channels, and interactions between subsurface erosion and root channels accounted for 36.9, 36.5, and 19.0%, of the described macropores. The mean macropore diameter in organic-rich soil layer (17–20 mm) was larger than in the B horizon (11–14 mm) at both spatial scales. The dominant gradients of all macropores in the organic-rich soil layer and B horizon were at negative oblique angles. Approximately 90% of the macropores in the organic-rich soil layer and approximately 80% of the macropores in the B horizon fell within the range between −50 and 50 degree planar direction. Subsurface flow and root systems are believed to play important roles in determining the morphological characteristics of macropores. These characteristics appear to have variable influences in different soil horizons rather than at different spatial scales. A part of this paper was presented at the 103th (1992) and 105th (1994) Annual Meetings of Japanese Forestry Society.     

应用热扩散式探针法对南方红壤丘陵区湿地松人工林耗水量的研究

运用Granier热扩散式探针法对湿地松(Pinus elliottii)树干液流密度进行长期连续测定,并对其周围多个气象要素和土壤要素进行同步测定。湿地松生长旺季不同月份晴天液流密度日变化规律基本一致,但液流启动、到达峰值的时间以及开始升高、开始下降的时间间隔存在差异。样木解析结果表明,处于低龄期的湿地松,整个木质部都可看作边材,边材面积和胸径可用二次函数很好地拟合。方差分析结果表明:不同胸径湿地松树干液流密度不存在显著性差异,与胸径无紧密关系。回归分析结果表明:湿地松日累计液流量与边材面积呈显著的线性相关关系,相关关系的判定系数达0.99。另外,单位边材面积日累计液流量与入选各气象因素的相关性显著,相关程度大小顺序为光合有效辐射>冠层相对湿度>冠层温度。结合边材面积-胸径回归方程和样木胸径调查资料,分别采用2种方法推算整个标准地的耗水量。经比较,2种方法所得结果差别不大,各自适用于一定的范围。     

Long-term changes in forest floor processes in southern Appalachian forests

Soil nutrient concentrations decreased in an aggrading southern Appalachian forest over a 20-year period. Construction of nutrient budgets showed significant nutrient sequestration aboveground including increased forest floor mass. We hypothesized that the changes in forest floor mass resulted from decreased litter decomposition rates because of decreased litter quality. In 1992 and 1993, we repeated a litter decomposition experiment conducted in 1969 and 1970 to test this hypothesis. In addition, we examined microarthropod populations and functional groups as litter decomposed. For four of the five species tested, first-year decomposition rates were about the same in both experiments. Initial litter nutrient concentrations of P were lower in all tree species in the most recent sampling. N, Ca, and Mg concentrations also declined in some species. These declines often resulted in decreased nutrient release rates during decomposition. Microarthropod populations differed significantly among litter species, as well as between years (probably resulting from differences in growing-season rainfall). For some litter species we found significant relationships between microarthropod populations and nutrient concentration (primarily C and N); however, most r²-values were low. Data suggest that changes in forest floor mass probably resulted from decreased litter quality and that those changes may have an effect on microarthropod populations.     

Financial feasibility of using shelterbelts for swine odor mitigation

A farm-level financial feasibility was performed to examine the use of shelterbelts as a swine odor mitigation technology. Shelterbelts are purposefully planted rows of trees and shrubs around the main sources of swine odor—swine buildings, manure storage systems, and crop fields that receive land applied manure. By using a series of model pork finishing farms and a number of differing shelterbelt design scenarios, the shelterbelt establishment and long-term (20 years) maintenance costs were calculated using a discounted cash flow analysis. Total costs for examined pork finishing farms, depending upon the shelterbelt design scenario, and whether or not government cost-share programming was used, ranged from $0.01 to $0.65 per pig produced. Study results emphasized the importance of cost-share programs, particularly Environmental Quality Incentive Program (EQIP). In most cases, both with and without cost-share programming, the total costs were well below reported pork producer expenditures for odor management.

基于树干液流通量的沙地樟子松合理林分密度的确定

应用热扩散式树干茎流计(TDP)对辽宁省章古台樟子松人工固沙林生长季期间树干液流速率进行了连续5年的测定,结合同步观测的降水、林冠截留量、林内蒸发散量和土壤水分含量,利用水量平衡的方法,推算了现阶段樟子松应有的合理密度。结果表明:4月上中旬沙地樟子松液流启动,10月中下旬液流基本结束,生长季(4-10月)各月平均液流速率分别为2.58、4.78、5.19、5.01、4.84、4.30、1.93 cm·h^-1,以6月份的最高,其次依次为7、8、5、9月份,4、10两月平均液流速率较低。通过推算,径阶14、16、18、20 cm的樟子松纯林的合理密度分别应为688、531、422、344株·hm^-2,现有同径阶的林分普遍存在密度过大的问题。研究结果对于现有林分的科学经营具有重要的指导意义。     

森林采运系统中原条流最优控制的研究

运用系统分析理论，揭示了森林采运系统中原条流具有时空性、连续性、服务性、可控性和经济性的特征。以与原条流量有关的生产和贮存费之和最小，组织原条运输和贮木场作业均衡生产为目标，运用现代控制理论建立了原条流宏观和微观控制的数学模型。通过实例证明了“两段式运材工艺”比“冬贮夏运（流）工艺”，具有显著的经济效益。     

霍林河流域洪水径流演变规律及驱动机制研究

霍林河是松嫩平原西部地区科尔沁、向海和查干湖湿地的重要补给水源,其洪泛作用对流域洪泛区环境系统的景观维系起着决定作用。选取流域3个代表测站近50年来的年最大洪峰流量序列,分析流域洪水径流演变的规律及驱动机制,包括自然和人为干扰两方面,可以为流域防洪减灾及洪水资源化利用提供理论依据。霍林河洪水以雨洪型为主,洪水多发于降雨...