Approach to the estimation of red heart occurrence in Fagus sylvatica based on geometric relationships between branch scar development and knot dimensions

Abstract

The effect of branch scars on the initiation and occurrence of red heart in beech (Fagus sylvatica L.) was studied on 17 trees with red heartwood and 14 trees with no discoloured heartwood, all of which were selected from a 120-year-old high-forest stand in Germany. Logistic regression was used to predict the probability of red heart occurrence for a given tree. The model was based on individual probabilities derived from geometric relationships between scar and knot morphologies, and integrated the diameter at breast height. Using this model, 27 of 31 trees were correctly classified, and the two groups of trees were clearly distinguished by probabilities below 0.25 and above 0.85 (with one exception). Given the constitution of the model, only 17 of 616 scars were found to initiate red heart formation, and the parameters of mechanistic variables were strongly correlated. The results suggest specifying the relationship between scars, knots and red heart, and extending the scope of the model.     

浑善达克沙地南缘沙化草地围封过程中土壤种子库与地上植被的耦合关系

在浑善达克沙地南缘,以围封不同年限的沙化草地(1年、4年、9年)为试验样地,并以未围封沙化草地作对照,深入研究了沙化草地围封过程中,土壤种子库与地上植被的耦合关系。结果表明,对沙化草地实施围栏封育,可显著提高土壤种子库与地上植被的物种丰富度;不同围封年限间,二者在植被群落组成上,均表现出较高的相似性,且相临阶段相似性较高,随围封年限差异的增加,相似性逐渐减小,但这一变化前者滞后于后者,表明草地在恢复演替中,前者较后者具有滞后性;4种类型样地之间,土壤种子库密度以及地上植被密度差异均极显著,且二者之间均存在显著正相关性,其关系均可用二次曲线描述。     

一种全站仪精准量测立木直径的方法

立木直径是森林资源调查的重要参数。本文提出了一种基于免棱镜全站仪对边测量原理的立木树干直径精 准量测方法,并以南方全站仪NTS-3401 为例,对该方法的理论精度进行了论证,结合量测数据对实际精度进行了 分析。结果表明:免棱镜全站仪对边测量原理的立木树干直径精准量测方法的理论精度中误差在0.4 mm 以内;使 用胸径尺量测立木直径3 次取平均值作为真值,用来检验全站仪量测立木树干直径的精度,数据表明真误差控制 在1 mm 以内,而林业测量中要求测量结果精确至1 mm。本文提出的全站仪精准量测立木直径的方法达到了林业 测量中量测立木直径毫米级的精度要求,可以解决非接触式量测立木上部(2 m 以上)直径的难题。      

Grazing Abandonment Delays the Effect of Temperature on Aboveground Net Primary Production in Atlantic Grasslands

We used an Atlantic grassland system on the Iberian Peninsula to ascertain whether monthly climate variability explains variation in monthly aboveground net primary production (ANPP) and to test whether climate-ANPP relationships depend on grazing regime. In 2005, large herbivores (beef cattle, dairy sheep, and horses) were excluded through fencing three 2 500-m² plots, each located in a different location; adjacent grazed plots of equal size were established. ANPP was measured monthly during the next three growing periods (2006 ? 2008), and locally measured climate data were obtained from a public database. Because between-site variation in annual ANPP was not significant, we used data averaged across sites to test for the effect of monthly climate variability on monthly ANPP by means of dynamic regression. Enhanced ANPP was found after grazing abandonment, probably due to the sudden dominance of productive graminoids. Variation in monthly rainfall did not contribute to explain monthly ANPP under grazing or grazing exclusion. Simultaneous mean monthly air temperature explained monthly ANPP under grazing. By contrast, the effect of temperature on ANPP under grazing exclusion was delayed by 1 mo. We suggest that this delay can be explained by the development of a thick organic layer (litter) that insulated the soil in the grazing exclusion plots. However, changes in floristic composition and, consequently, in phenology might also have contributed to the differential response.     

Geographic variability in taxonomic composition,standing stock,and productivity of the mesozooplankton community around the Kuroshio Current in the East China Sea

Despite the low productivity that has been thought to characterize plankton communities in the western boundary current of the North Pacific Subtropical Gyre, many migratory fishes risk encountering low food availability during crucial life history stages by reproducing and recruiting in the Kuroshio region (i.e., the Kuroshio Paradox). Here, we report on geographic variability in taxonomic composition, biomass, and productivity of the mesozooplankton community in the Kuroshio Current and neighboring waters in the East China Sea. Calanoid copepods were the most abundant mesozooplankton taxon throughout our sampling stations. Small copepods, which include nauplii and poecilostomatoids, and gelatinous metazoans were the next most abundant. Seasonal variability in mesozooplankton standing stock (i.e., abundance and biomass) and productivity (i.e., production rate and protein synthetase activity) exceeded spatial variability across the stations and regions. The mesozooplankton community was characterized by high biomass and production rates in the summer, as well as high abundance and protein synthetase activity in the fall. No significant differences were found for mesozooplankton standing stock and productivity in the Kuroshio Path relative to those on the continental shelf or on the outside of the Kuroshio Path. Our results indicate that the standing stock and productivity of the mesozooplankton community in the Kuroshio Path are equivalent to those on the continental shelf, and that these communities are supported by small copepods and gelatinous zooplankton. We suggest that the mesozooplankton standing stocks and productivity provide adequate food availability for migratory fishes in the Kuroshio and neighboring waters in the East China Sea.     

抛秧物理立苗对水稻生长的影响及其调控因素的研究

【目的】研究抛秧物理立苗对水稻生育的影响及其调控因素,探讨提高物理立苗的技术指标,为改善生产上抛秧群体起点质量提供理论依据。【方法】通过设置直立苗、倾斜苗、平躺苗3种物理立苗姿态,研究不同物理立苗状况对抛秧稻生育的影响,从整地、抛栽高度、水层深度、不同球土比例等方面试验,探讨抛秧物理立苗的调控因素。【结果】直立苗在抛后活棵快,各生育阶段干物重、N素吸收、光合势、净同化率、抗倒性、产量上都高于倾斜苗,并显著高于平躺苗;在土壤5—6cm呈烂糊状,抛高为3m时,直立苗率最高,达81%;随着抛栽时水层深度的增加,直立苗比例逐渐减少;对苗高而言,宜控制在10—16cm,适当选择孔大的塑盘,抛后的直立苗比例超过70%。【结论】直立秧苗各阶段生育状况好于倾斜苗和平躺苗,显著好于平躺苗。提高直立苗比例,可有效促进抛秧高产的形成。土壤5—6cm烂糊,采用矮壮苗,适当提高球土比例,抛高3—4m条件下,立苗效果好。     

三维激光扫描系统在立木材积测定中的应用

该文提出了一种测定疏林立木材积的新方法,即利用三维激光扫描系统测量立木材积并建立材积表.采用该方法在标准地内按径阶对立木进行三维扫描,可以获取基本测树因子(包括立木的胸径、树高、冠幅)和三维立木模型,由Cyclone扫描软件可以计算立木材积.由扫描获取的立木胸径和树高能够回归建立二元立木材积方程.为检验扫描获取的基本测树因子的精度以及材积方程的适用程度,将扫描后的立木伐倒,并采用区分求积法实测材积.对比扫描数据和实测数据,扫描获取的基本测树因子和扫描材积均满足精度要求,说明这种新方法能够用于森林资源调查和建立立木材积表.     

Seedbank phytosociology of the Strandveld Succulent Karoo,South Africa: a pre‐mining benchmark survey for rehabilitation

Prior to the mining of heavy minerals, the seedbank of the Strandveld Succulent Karoo was investigated to serve as a benchmark for the future rehabilitation of the area. Seedbank composition and species' abundance were determined with the seedling emergence method. By using the Braun‐Blanquet method, five main vegetation units were identified in concordance with results obtained for the standing vegetation. A total of 108 species were recorded in the seedbank, which represents c. 50 per cent of the species recorded in the standing vegetation of the total study area. Seven annual species (3 per cent) were unique to the soil seedbank. On community level, similarity in species composition between the standing vegetation and the soil seedbank ranged between 39·2 per cent and 48·8 per cent, with a similarity of 54·3 per cent for the total study area. Annual and perennial species' similarity in species composition between the standing vegetation and the seed bank totalled 74·8 per cent and 43·1 per cent respectively. Post‐mining topsoil replacement as well as seeding and transplanting of selected local species will be essential to revegetate this area. Copyright © 2001 John Wiley & Sons, Ltd.