陕北黄土丘陵区枣树引种初报

陕北老区现有枣树44万多亩,占全省枣树面积的70%以上,主要分布在黄河沿岸,年产红枣3630多万公斤。但离黄河较远的黄土丘陵沟壑区,枣树较少。据调查,除气候差异外,主要原因是品种不良,品质较差,产量较低。为了寻找适宜陕北黄土丘陵区栽植的优质丰产枣树品种,我们从1985年春开始进行引种试验。经过6年的努力,取得了初步结果,现报告如下。1 材料与方法1.1 材料来源1985年3月下旬至5月上旬,先后从山东省乐陵县引进金丝小枣、长红枣、无核     

黄土丘陵区枣园施肥试验

根据黄土丘陵区土壤肥力特点及土体结构，选用硝酸铵和过磷酸钙作为试验肥料，进行了不同施肥量试验。结果表明，黄土丘陵区穴施磷肥的效果要比传统的施肥方法效果好，最佳施肥量为1．0kg／株～1．5kg／株；枣树对硝铵反应十分敏感，施肥量必须严格控制，黄土丘陵区硝铵的最适施肥量为0．10kg／株～0．25kg／株，过多或过少都会明显影响枣树的吊果率和产量。     

隔坡水平沟栽植枣树是黄土丘陵地区治坡最佳模式

隔坡水平沟栽植枣树是黄土丘陵地区治坡最佳模式杨家洪，张志善，郭绍仙（山西省农业科学院太原，０３００００）１黄土丘陵区发展枣树是脱贫致富的主要途径１．１枣树的起源枣树是我国最早的栽培果树之一，其原生种为酸枣，是由峻枣在漫长的历史长河中．经过自然和人工选...     

子洲县山杏低产林改造技术

根据林业生产实践和相关资料,总结提出了陕北黄土丘陵区山杏低产林改造技术和管理措施。     

陕北黄土丘陵区仁用杏早期丰产栽培技术

陕北黄土丘陵区仁用杏早期丰产栽培技术杨荣慧，常晓明，鲁向平，李平（陕西省黄土高原治理研究所，陕西米脂７１８１００）陕西省政府已把仁用杏的推广栽培确定为陕北贫困山区脱贫致富措施之一。我所近几年对一些杏树优良品种进行了引种栽培试验，现将坡地栽培技术、整地...     

枣树增产措施的探讨

枣树是我县的一大干果,现有结果枣树80万株,人均7株。但是产量却很低,年总产140万至200万斤,平均株产2斤。为了探讨枣树增产的有效措施,于1980年在长泞公社南合流大队,进行了枣树增产技术措施的研究。南合流大队位于黄土丘陵区,全大队254户,1002口人,耕地2280亩,结果枣树12000株,主栽品种是榆次芽枣,树龄30至50年。1966年是最高产年,红枣总产24万斤,1979年是最低产年,总产只有1万斤,平均株产不足1斤。这里枣树产量低的主要原     

黄土高原“着装”必须处好四个关系

陕北黄土丘陵区包括榆林地区南部和延安市北部,大约20个县的全部或部分区域。这一区域也是全省五大地貌类型中,生态环境最为恶劣的一类。 水土流失是这个区域主要的生态灾害。区域内有85％以上的土地不仅存在水土流失,而且     

浅谈陕北老区红枣开发与利用

我省是全国红枣生产区之一,陕北老区又是我省红枣重要产地。全省有枣树62.78万亩,年产鲜枣5179.4万公斤,陕北老区就有枣树44.0万亩,占全省枣树面积70%以上,年产红枣3630万公斤。枣树在陕北老区主要分布在黄河、洛河、无定河沿岸,以黄河沿岸为最多。以现有分布范围来看,除定边、吴旗外,其余各县均有枣树生长。其中清涧,绥德、佳县、吴堡、延长、延川等县,是我省和陕北老区产红枣最多的县。     

陕北枣树的整形修剪技术

根据陕北枣树的立地条件,在多年实践的基础上对陕北枣树的整形修剪技术进行了系统总结。     

浅谈黄土丘陵区造林绿化

本文分析了黄土丘陵区的自然特点，提出了在黄土丘陵区营造防护林的指导思想和方针，最后指出了在黄土丘陵区造林的树种选择和有关技术问题。     

Predicting moisture content and density distribution of Scots pine by microwave scanning of sawn timber II: evaluation of models generated on a pixel level

The purpose of this study was to use images from a microwave sensor on a pixel level for simultaneous prediction of moisture content and density of wood. The microwave sensor functions as a line-scan camera with a pixel size of 8mm. Boards of Scots pine (Pinus sylvestris), 25 and 50mm thick, were scanned at three different moisture contents. Dry density and moisture content for each pixel were calculated from measurements with a computed tomography scanner. It was possible to create models for prediction of density on a pixel level. Models for prediction of moisture content had to be based on average values over homogeneous regions. Accuracy will be improved if it is possible to make a classification of knots, heartwood, sapwood, etc., and calibrate different models for different types of wood. The limitations of the sensor used are high noise in amplitude measurements and the restriction to one period for phase measurements.     

林木最近距离分布模型的研究

林木距离分布是森林结构的重要体现，林木最近距离分布的估计是应用与距离有关的单木生长模型、林分空间结构模拟与重现以及森林可视化经营的重要基础。研究提出了模拟林木最近距离分布的新途径，指出林木距离分布遵从Weibull分布。结构丰富天然林的林木最近距离分布仅用2参数的Weibull分布函数足以很好地表达。研究提出的描述林木最近距离分布模型是进一步用非耗时费力的因子预测距离分布的前提。     

冀北山区森林生态系统服务价值评价

以冀北山地的森林生态系统为研究对象,利用《中国森林生态系统服务功能观测与评估规范(LY/T1721-2008)》中的评估方法,定量评价了该区不同植被类型生态系统服务价值。冀北山地森林生态系统服务功能总价值为579.13亿元/a,其中涵养水源价值为294.09亿元/a,固碳释氧价值为142.81亿元/a,物种保育价值为87.37亿元/a,保育土壤价值为27.20亿元/a,营养物质积累价值为25.04亿元/a,净化大气价值为1.95亿元/a,森林游憩价值为0.67亿元/a。其中,核桃楸、椴树和桦树的单位面积服务价值最大。     

资源约束条件下工期、质量、成本综合均衡优化

工期、质量、成本称为工程项目的三大控制目标,三者相互依存,相互影响.工程项目优化控制的理想结果是同时实现合理的工期、较低的费用和较高的质量.利用多属性效用函数以及效用分解定理,建立了基于资源约束条件下的工期、质量、成本的综合均衡优化与控制模型,并引入遗传算法,对模型进行求解.通过一个应用实例,对实际施工中的工期、质量、成本综合均衡优化给出了备选方案.     

Prediction of annual tree growth and survival for thinned and unthinned even-aged maritime pine stands in Portugal from data with different time measurement intervals

An annual individual tree survival and growth model was developed for pure even-aged stands of maritime pine in Portugal, using a large data set containing irregularly time-spaced measurements and considering thinning effects. The model is distance-independent and is based on a function for diameter growth, a function for height growth and a survival function. Two approaches are compared for modeling annual tree growth. The first approach directly estimates a future diameter or height using well-known growth functions formulated in difference form. The second approach estimates diameter or height using a function in differential form estimating the increment over a year period. In both approaches, the function parameters were related to tree and stand variables reflecting the competition status of the tree as well as of a thinning response factor. Variable growth and survival rates were assumed in the modeling approaches. An iterative method was used to continuously update tree and stand attributes using a cut-off to convert the survival probability for a living or a dead tree. The individual tree diameter growth model and the survival probability model were fitted simultaneously using seemingly unrelated regression (SUR). Parameters of the height function were obtained separately as the number of observations for height was much lower than the number of observations for diameter, which may affect the statistical inference and the estimation of contemporaneous cross-equation error correlation inherent to the system of equations. PRESS residuals were used to evaluate the predictive performance of the diameter and the height growth functions. Additional statistics based in the log likelihood function and also in the survival probability were computed to evaluate the survival function. The second modeling approach, which integrates components of growth expansion and decline, performed slightly better than the first approach. A variable accounting for the thinning response that was tested proved to be significant for predicting diameter growth, even if the model already included competition-related explanatory variables, namely the basal area of trees larger than the subject tree. However, this thinning response factor was not significant for predicting height growth.     

Sustainability and Biodiversity

Abstract

The implementation of the Rio protocol and the preservation of biodiversity at the national and regional levels is an important step in achieving sustainable forestry. This is indeed a challenging task since our knowledge of the ecology and habitat demands for but a few species is severely restricted. Research in the last years shows that forest species have very different qualitative and spatial demands on their environment, which require complex and broad solutions. This poses a great problem for conservation and often forces societies/decision-makers to make decisions based on assumptions rather than on empirical data. With assumptions follow uncertainty, a factor that is necessary to control. We identify and discuss the uncertainties of steps that are considered to be important for preserving biodiversity on a regional level and exemplify this with cases from southern Sweden. We argue that there is no universal solution for the conservation of biodiversity. In strongly fragmented and transformed regions like southern Sweden, a mix of species approaches and ecosystem approaches is necessary for biodiversity conservation. Programs for preserving biodiversity should be flexible, not rigid, allowing for modifications due to a constantly increasing body of knowledge and environmental changes. Prominent gaps in our knowledge include species dispersal ability and propensity, extinction rates and the species dependence on fragmentation and landscape history. It is possible that the question of responsibility species (a species for which a region has an explicit conservational responsibility) may gain in importance, an issue with far-reaching implications for economy and inter-regional compensatory systems.     

承载索许用荷重设计法研究

原传统的许用应力法,在承载索设计计算中运算繁琐,应用不便。本文提出许用荷重设计法,在抛物线理论的基础上推导出一系列计算公式,编制承载索数值表,建立起系统的许用荷重设计方法。     

林业科技期刊在科技兴林中的作用

林业科技期刊是林业科技情报的重要组成部分、是传播科学技术的重要载体；是科技成果、科学技术转化为生产力的媒介；是培养教育林业科技人才的阵地；是增强林业发展后劲的源泉；是增进科技合作与交流的桥梁。提出了办好林业科技期刊，优化报道，明确服务对象等是加快科技兴林步伐的关键措施。     

Biomass harvesting from buffer strips in Italy: three options compared

There is an urgent need for new, mechanized systems that may restitute some profitability to buffer strip harvesting and motivate regular maintenance. An opportunity for innovation is offered by the growing success of chip-fed boilers, since the production of chips is simpler than that of logs and has a higher potential for cost reduction. Within this context, a study was conducted in Italy with the goals of: (a) designing three alternative chip harvesting methods for buffer strips, (b) field-testing the performance of each alternative, and (c) developing a model for estimating the cost of these methods under varying operational and economic conditions. The three harvesting methods reflected different mechanization levels, with escalating investment requirements. Overall, the study demonstrated that frequent maintenance of young, single row buffer strips generates profits only when thoroughly mechanized. Using a dedicated feller-buncher, a front-end loader for extraction and an industrial truck-mounted chipper brought the delivered cost below the 14 €/m³ loose chips (approximately 4 €/GJ) presently paid by the district heating stations. However, the intermediate-mechanization system showed the highest potential for improvements. The␣study generated a spreadsheet-based model for predicting the effects of varying work conditions and cost hypotheses.