Thinning intensity effects on carbon and nitrogen stores and fluxes in a Norway spruce (Picea abies (L.) Karst.) stand after 33 years

The present paper deals with C and N storage in soil and vegetation, litter fall and CO₂ efflux from the soil 32–33 years after early thinning in a Norway spruce (Picea abies (L.) Karst.) stand in order to evaluate the effect of thinning regime on C sequestration. At 22 years old, the stand was reduced from 3190 to 2070, 1100 and 820 trees per hectare in four replicates. The N2070 treatment represents the recommended start density in practical forestry, while the other represent a moderate to large reduction in tree number at the present stand age. Aboveground biomass was estimated from single tree measurements of diameter and height based on allometric functions. Litter fall was collected during one and a half years and soil respiration was measured on five occasions during one summer. Ground vegetation was mapped and sampled for biomass, C and N determination. A significant decrease in aboveground tree (including stump-root system) C storage of 27% and 22% due to thinning was found in the N820 and N1100 treatments, respectively, compared to the N2070 treatment. Ground vegetation C storage was little affected by treatment, while litter fall C showed a non-significant decrease in the N820 and N1100 treatments compared to the N2070 treatment. Soil respiration was significantly lower in parts of the summer in the N2070 treatment compared to the N820 treatment. The reason for this is still unexplained since no differences in soil temperature, soil moisture or litter fall chemistry was found between the treatments. No significant treatment effects on humus and mineral soil C storage could be detected. With the present soil variability, the time period of 32 years is probably too short to detect soil C differences due to thinning. The N storage followed the same pattern as for C.     

Relationships between morphological traits and resistance to pine wood nematode in two Japanese pines

It has been suggested that certain morphological traits of Japanese pines function as resistance factors against the pine wood nematode (PWN), Bursaphelenchus xylophilus. The aim of this study was to verify this concept, and to determine the relationships between traits and resistance at both the individual and family levels. Relationships between survival rate and morphological traits of Pinus densiflora and Pinus thunbergii were studied after inoculation with PWN. Morphometric parameters used were height, basal diameter of the axis, and the number of branches from the axis. Three indices of relationships were analysed: (1) among individuals within a family (survival difference between smaller and larger morphometric populations within each family); (2) among individuals (correlation between each morphometric average and survival rate in quintile populations of all subjects within each pine species based on the order of morphometric values); and (3) among families (correlation between each morphometric average and survival rate in the family). Both significant and non-significant differences were detected within a family, indicating a need for macro techniques. Among individuals, a thicker axis and more branches were correlated with increased survival, indicating that they are resistance factors. However, these correlations were not significant among different families. These results indicate that morphological traits cannot be used to evaluate resistance at a family level, even if they are significant at an individual level. Further studies on traits associated with resistance should be conducted at a family rather than an individual level, to breed for Japanese pines with resistance to PWN.

芜湖市5所公园地被植物应用状况分析

为进一步明确地被植物在城市公园中的景观应用,采用实地调研的方法,记录并分析安徽省芜湖市内的赭山公园、镜湖公园、九莲塘公园、滨江公园(一期)和雕塑公园的地被植物应用状况.结果显示,5所公园常用地被植物共有94种,其中草本41种、木本53种,麦冬等7种草本及洒金桃叶珊瑚等32种木本地被植物应用最多;各公园的滨水区域地被植物...     

森林生态系统中林分胸径和树高的Granger因果关系研究

滞后阶数为1时,胸径和树高互为Granger原因,这从理论上证明,建立胸径和树高模型是合理的.当滞后阶数为2时,胸径不再是树高的Granger原因,但树高仍是胸径的Granger原因,两者相比,树高的影响更深远.所以在森林培养时,应更加注重树高,以维持树高对胸径的影响.     

国毛毛丛直径形态特征的探讨

通过对毛丛直径形态的分析和研究来达到以下两个目的：一是了解羊毛在生长过程中毛丛中纤维细度的变化和原因，为羊毛生产者在育种和改进羊群管理方面提供一些科学试验依据；二是根据毛丛直径形态的特征，结合强力和断裂位置等原毛指标，来分析和判断在毛条加工过程中毛条的质量情况，如毛条中纤维的长度和长度分布等，来指导羊毛加工和生产。     

不同地表覆盖处理对湿地松二代种子园土壤含水率的影响研究

对不同地表覆盖处理下湿地松二代种子园土壤含水率情况进行了研究,结果表明:①不同覆盖处理之间,土壤含水率Ⅰ和土壤含水率Ⅲ存在极显著差异,土壤含水率Ⅱ差异不显著.②各覆盖处理下土壤含水率Ⅰ高低顺序为:白薄膜＞锯木屑＞黑薄膜＞对照,且最高值比最低值高26.69％;各覆盖处理下土壤含水率Ⅱ高低顺序为:白薄膜＞黑薄膜＞锯木屑＞对照,且最高值比最低值高20.64％;各覆盖处理下土壤含水率Ⅲ高低顺序为:黑薄膜＞白薄膜＞锯木屑＞对照,且最高值比最低值高26.61％.     

Evaluation of the water use efficiency of alternative farm practices at a range of spatial and temporal scales: A conceptual framework and a modelling approach

Water is the principal limiting resource in Australian broadacre farming, and the efficiency with which farmers use water to produce various products is a major determinant both of farm profit and of a range of natural resource management (NRM) outcomes. We propose a conceptual framework based on multiple water use efficiencies (WUEs) that can be used to gain insight into high-level comparisons of the productivity and sustainability of alternative farming practices across temporal and spatial scales. The framework is intended as a data aggregation and presentation device. It treats flows of water, biomass and money in a mixed farming system; economic inefficiencies in these flows are tracked as they are associated with a range of NRM indicators.We illustrate the use of the framework, and its place in a larger research programme, by employing it to synthesise the results from a set of modelling analyses of the effect of land use choices on long-term productivity and a range of NRM indicators (frequency of low ground cover, deep drainage, N leaching rates and rate of change in surface soil organic carbon). The analyses span scales from single paddocks and years to whole farms and have been carried out with the APSIM and GRAZPLAN biophysical simulation models and the MIDAS whole-farm economic model.In single wheat crops in one study, different land uses in preceding years affect grain yield primarily by affecting the harvest index. When the scale changes to cropping rotations, the critical factor affecting overall water use efficiency is found to be the proportion of stored soil water that is transpired by crops. When ordinated in terms of their water use efficiencies, a set of 45 modelled rotation sequences at another location are differentiated mainly by the proportion of pasture in the rotation; when rotations are ordinated using key NRM indicators, the proportion of lucerne pasture is the main distinguishing factor. Finally, we show that for whole crop-livestock farms at three different locations across southern Australia, the pattern of water use efficiencies in the most profitable farming systems changes in similar ways as cropping proportion is altered. At this scale, land use choices affect multiple water use efficiency indices simultaneously and commodity prices determine the balance of the resulting economic tradeoffs.Limitations to the use of the WUE framework arising from its relative simplicity are discussed, as are other areas of farming systems research and development to which it can be applied.     

Individual tree diameter increment model for managed even-aged stands of ponderosa pine throughout the western United States using a multilevel linear mixed effects model

A diameter increment model is developed and evaluated for individual trees of ponderosa pine throughout the species range in the United States using a multilevel linear mixed model. Stochastic variability is broken down among period, locale, plot, tree and within-tree components. Covariates acting at tree and stand level, as breast height diameter, density, site index, and competition indices are included in the model as fixed effects in order to explain residual variability. The data set used in this study came from long-term permanent research plots in even-aged, pure stands both planted and of natural origin. The data base consists of six levels-of-growing stock studies supplemented by initial spacing and other permanent-plot thinning studies for a total of 310 plots, 34,263 trees and 153,854 observations. Regression analysis is the preferred technique used in growth and yield modeling in forestry. We choose the mixed effects models instead of the regression analysis approach because it allows for proper treatment of error terms in a repeated measures analysis framework. Regional growth and yield models exist for ponderosa pine. However, data collection and analysis procedures differ. As a result, comparisons of growth responses that may be due to geographic variation of the species are not possible. Our goal is to present a single distance-independent diameter increment model applicable throughout the geographic range of ponderosa pine in the United States and by using only data from long-term permanent plots on sites capable of the productivity estimated by Meyer [Meyer, W.H., 1938. Yield of Even-Aged Stands of Ponderosa Pine. US Department of Agriculture Technical Bulletin 630].     

夏季森林地下火分类及火行为特点

通过对黑龙江省近10年来各地发生的夏季森林地下火进行实地踏查和研究分析，对地下火的分类和夏季森林地下火蔓延规律、日变化规律、火行为特点进行了研究。     

马尾松人工混交林直径分布规律的研究

应用5种概率分布律对马尾松人工混交林的直径分布规律进行拟合。结果表明：马尾松人工混交林的胸径分布基本上符合威布尔分布、正态分布和β分布。C、偏度、峭度等特征值符合人工林生长特点。