黄羊滩风蚀沙地地表风蚀量的研究

该文通过对黄羊滩不同类型风蚀沙地的地表风蚀的观测表明,地表风蚀量受地表植被盖度影响较大,地表风蚀量以植被盖度10%以下的沙化林草地为最大,沙化农田次之,这两者为主要沙尘来源,其风蚀沙化量远高于植被盖度10%以上的沙化林草地,是当前防沙治沙工程实施的重点。     

农田土壤风蚀防治技术研究进展

通过文献计量学的方法对我国农田土壤风蚀防治技术的研究进展、研究热点进行了检索与分析,将农田土壤风蚀防治技术分为保护性耕作措施、机械措施、生物措施、化学措施4种类型.目前,我国农田风蚀防治技术研究还处于发展阶段,主要开展以生物措施(农田防护林)为基础、保护性耕作措施(秸秆还田)为主、机械措施为辅、化学措施为新的发展趋势等...     

土壤风蚀与植被防护研究

在收集总结国内外土壤风蚀与植被防护相关研究文献的基础上,从土壤风蚀原理、风蚀影响因素、风蚀预报模型、土壤风蚀容忍量、植被覆盖防风蚀效应等方面评述了国内外土壤风蚀与植被防护的研究现况,据此指出了研究中存在的问题,提出了今后的研究方向。     

免耕留茬控制风蚀机理

通过对四种不同高度、不同密度的向日葵留茬地的观测,发现:留茬高度越大、密度越大,对地表风速的降低和粗糙度的增大作用越明显,反之则越弱;茬高、密度大的留茬,控制风蚀作用也十分显著,反之,其作用弱,而在没有留茬时,风蚀加重,地表收集到的风蚀物含量增加。     

乌兰察布盟后山地区风蚀沙化的防治措施

乌兰察布盟后山区风蚀沙化面积大，严重威协着该区人民生活、生存，已引起各方面的关注，为此文章就乌盟后山地区风蚀沙化状况进行了分析，并提出了以生物工程为主的防治措施，供生产中参考。     

经营方式对风蚀沙土地力影响的研究

该文对宣化县黄羊滩风蚀沙土地力因子进行了野外调查与室内分析,结果表明:不同经营方式对风蚀沙土地 力因子影响显著不同,营林方式对风蚀沙土的改良进程非常缓慢,必须人工促进调节地力因子。同时,将粘粒、胶粒及有 机质这3个因子确定为风蚀沙土的特征因子,作为地力调节的指标因子。     

风沙源区应注重风蚀治理

2000年国家紧急启动了京津周边地区风沙源治理工程,至今已运行了三年,其中风沙源项目的水土保持项目比重较大,本文试从风蚀治理与水蚀设计思路上提一点建议。因害设防,正确区分水蚀与风蚀。水利部公布目前全国水土流失面积比1990年减少11万平方公里,而风蚀面积却呈上升趋势。内蒙古自治区的水土流失面积中水蚀面积15万平方公里,风蚀面积是59万平方公里,约占水土流失面积的80%。如果用单一水蚀的防御标准可能得不偿失,因为在内蒙古水蚀不常遇而风蚀年年遇,春天甚至月月都能遇。因此在内蒙古这样的风蚀强烈地区进行水土保持治理,应由单一水蚀…     

引黄灌渠沿岸沙丘土壤风蚀的研究

选择引黄灌渠清淤形成的沙丘作为研究对对象，采用标尺法分别观测了有林地及裸露地的土壤风蚀情况，同时分析了土壤机械组成、土壤物理性状及水文状况，结果证明，植树造林能显著地改良土壤，减弱土壤风蚀，有林地比裸露地土壤贮水量增加９．９８－３１．８５ｔ／ｋｍ＾２，土壤风蚀深度降低４０％以上。     

浅论干旱、半干旱地区土壤风蚀发生机理及防治措施

土壤风蚀是导致干旱半干旱地区土地沙漠化与沙尘暴的主要原因之一。本文分析了我国荒漠化现状、土壤风蚀发生机理、影响土壤风蚀的自然因素和人为因素以及土壤风蚀的防治措施。并根据以上分析，对土壤风蚀治理提出了几点建议。     

半干旱区沙质农田土壤风蚀防治的效应研究

本文研究了不同作物留茬和建设农田防护林对遏制农田土壤风蚀的效应。结果表明：不同作物残茬留量对农田土壤风蚀具有一定的控制作用,但仅留茬措施不能根本性遏制农田土壤风蚀;高积沙农田的风蚀深度和土壤风蚀量均高于平沙地农田,其中〉10m高积沙农田的风蚀深度和土壤风蚀量分别为2．9cm和289．5t／hm2;农田防护林带内的平均风蚀深度和平均土壤风蚀量分别为0．38cm和38．85t／hm2,仅为林带外的18．10％和18．49％,说明在该区建立农田防风林（网）是遏制农田土壤风蚀的有效途径。     

Browsing Damage on Pine (Pinus sylvestris and P. contorta) by a migrating moose (Alces alces) Population in Winter: Relation to Habitat Composition and Road Barriers

In Scandinavia, moose (Alces alces L.) sometimes cause severe browsing damage to economically-important pine. Moose-vehicle accidents have spurred construction of fences along roads, and these may interfere with moose migration between summer and winter ranges, or the road alone may be a barrier. If this happens and moose build up along roads, landowners may suffer economically. Therefore, this study investigated whether roads, fences or other factors influence the use of young pine stands by moose. Eighty stands along roads in northern Sweden were evaluated in which individually-browsed branches were counted on 9972 pines. Moose browsing was not significantly related to birch (Betula pendula Roth, B. pubescens Ehrh.) density, nor did it differ between pines (Pinus contorta Douglas or P. sylvestris L.). However, increased pine density, site productivity and proximity to a highway were associated with increased browsing. Further large-scale studies are needed to understand moose habitat selection and the effects of roads.     

Effects of Root Freezing on the Physiology and Growth of Picea glauca,Picea mariana and Pinus banksiana Seedlings Under Different Soil Moisture Regimes

The root systems of 2-yr-old Picea glauca, Picea mariana and Pinus banksiana seedlings were submitted to various frost temperatures during an artificial frost to induce different levels of root damage. Frost-damaged and control seedlings were placed in a greenhouse under high and low soil moisture regimes. Seedling growth and physiology were evaluated periodically. Seedling survival was reduced when root damage reached levels of 60-80%. Root systems of all three species showed partial to total recovery by the end of the experiment. In general, root freezing damage caused reductions in seedling growth, with these reductions becoming less significant over time. Root damage had little to no effect on black spruce and jack pine seedling physiology, while white spruce CO 2 uptake decreased with increasing root damage. Shoot nitrogen content of all three species decreased slightly with increasing root damage.     

Stand Structure in Pine,Spruce and Deciduous Forests: A Comparison Between Finnish and Russian Karelia

This study investigated the stand structure in pine, spruce and deciduous forests in the border district of Finland and Russia. A total of 46 mature forest stands was selected as pairs, the members of each pair being as similar as possible with respect to their forest site type, age, moisture and topography. The stands were then compared between the two countries by means of basal areas and number of stems. The proportions of dominating tree species were 2-12% lower, and correspondingly the proportions of secondary tree species higher, in Russian forests. The density of the forest stock was also higher in each forest type in Russia. The forests in the two countries differed most radically in terms of the abundance of dead trees. The amount was two to four times higher in Russian deciduous and spruce forests, and in pine forests the difference was 10-fold. The stand structures indicated that Russian coniferous stands, in particular, were more heterogeneous than intensively managed pine and spruce stands in Finland.     

Growth and Terminal Bud Formation in Picea abies Seedlings Grown with Alternating Diurnal Temperature and Different Light Qualities

The root collar diameter and the height:diameter ratio are of particular importance in container-grown seedlings where a high density in the containers may produce spindly seedlings. Temperature regimes and light quality are known to affect plant growth. The aim of this study was to identify responses in Picea abies (L.) Karst. seedlings grown with light providing different red:far-red ratios and under temperature regimes with alternating day (DT) and night temperature (NT) from negative (DT < NT) to positive (DT > NT) difference (DIF) between DT and NT. Experiments were conducted in controlled environment chambers and in a daylight phytotron. Only limited thermoperiodic responses appeared in P . abies seedlings with respect to seedling height and dry weight accumulation. The formation of terminal buds, however, was clearly delayed in seedlings grown at negative DIF. The results indicate a requirement for day extension light that is high in far-red, to prevent terminal bud formation under natural short-day conditions. An extended study should be conducted to clarify the minimum level of light intensity and the optimal light quality needed to prevent terminal bud formation under natural short-day conditions.     

CAD与建筑设计的关系

本文分析了CAD在设计中引起的正面和负面影响,并进行了系统的阐述,从而使设计者在应用中能够保持客观的态度。     

Natural Regeneration in Clear-cuts: Effects of Scarification,Slash Removal and Clear-cut Age

The effects of soil scarification (mounding), slash removal and clear-cut age on the natural regeneration in clear-cuts was evaluated using data from four sites in southern Sweden. The treatments were carried out during a good seed and establishment year for birch ( Betula pubescens Ehrh. and B. pendula Roth). Scarification had the strongest positive effect on the density of naturally regenerated seedlings, especially in birch, but also in pine ( Pinus sylvestris L.) and spruce [ Picea abies (L.) Karst]. Slash removal had a positive effect on birch density. No statistically significant effect of clear-cut age was found. In addition, no statistically significant interactions between clear-cut age and scarification or slash removal were found. The ingrowth of field vegetation was the fastest in areas that were not scarified, less rapid in areas scarified on old clear-cuts, and the slowest after scarification in fresh clear-cuts. In conclusion, it may be possible to control the density of birch during a good establishment year for birch. If birch is desired, the best combination of treatments is to remove the slash and scarify; otherwise, these treatments should be avoided.     

Risk Perception Among Non-industrial Private Forest Owners

Based on an enquiry, risk perception among non-industrial private forest owners is described in relation to climate change and forestry hazards. Of the respondents, 11% took action to remedy the effects of climate change. Out of a given set, hazards were ranked according to each respondent's experience of recent substantial financial loss to the estate and in relation to his or her willingness to make investments aimed at risk reduction. For each hazard, the respondent assessed the risk in four classes ranging from very high to negligible risk. Six hazards were considered most problematic in all three aspects: browsing damage, falling timber prices, damage by wind, spruce bark beetle, root rot and pine weevil. A majority of the respondents claimed to take action to reduce the risk associated with at least one hazard, while 35% did not know whether they did. Excluding climate change, the need for decision support was the largest in relation to damage by wind owing to a combination of perceived high risk and a high level of ignorance in relation to whether risk-reducing measures were taken.     

Interactions in decomposition and N mineralization between tropical legume residue components

In situ produced plant residues contain a mixture of different plant components of varying quality. To assess synergistic or antagonistic interactions occurring during the decomposition and mineralization of such mixtures, individual plant parts (stems, leaves, leaf litter and roots) or the mixture of stems, leaves and leaf litter of the agroforestry species pigeonpea (Cajanus cajan) or of crop residues of peanut (Arachis hypogaea) or of the weed hairy indigo (Indigofera hirsuta) were incubated in pots for 19 weeks. Periodically, remaining plant residues were sieved out (>2 mm), weighed and N content as well as soil mineral N determined. Above- and below-ground residues of peanut decomposed fastest and showed the largest N release in agreement with their high N concentration and low-acid detergent fibre (ADF) : N ratio. Hairy indigo was hypothesized to be of lower quality than pigeonpea because of its high-polyphenol content. However, it decomposed faster than pigeonpea, largely because of the higher N and lower lignin concentration of its components. Ranking of individual plant components for N mineralization resulted in the following pattern, leaves > leaf litter > roots > stems. In mixtures of the different plant components a similar species order in decomposition was obtained, e.g. peanut > hairy indigo > pigeonpea. The amount of N released from the mixture was dominated by stem material that comprised 46–61% of the mixture. The interactions in mixtures were relatively small for peanut (generally high-quality components) as well as for pigeonpea (low proportion of high-quality components, i.e. N rich leaf material). However, a positive interaction occurred during later stages of N mineralization in the mixture of hairy indigo as it had a significant proportion of N rich components and absence of highly reactive polyphenols. Thus, for plants with low to intermediate chemical quality attributes, manipulating plant composition (e.g. by varying harvest age, affecting stem and leaf proportions) will be important to obtain significant interactions during decomposition when its components are mixed.     

Pasture production and tree growth in a young pine plantation fertilized with inorganic fertilizers and milk sewage in northwestern Spain

The use of organic waste materials such as milk sewage as an organic fertilizer could have the dual advantages of organic-waste disposal and reduced dependence on inorganic fertilizers. The effects of fertilization with (1) conventional mineral fertilization, (2) milk sewage sludge at 40 kg N ha⁻¹ target rate and (3) no fertilization on pasture production and tree growth were examined in an experiment consisting of two pasture mixtures under a one-year-old Pinus radiata plantation with a density of 2500 trees ha⁻¹. The two pasture mixtures were: (1) Dactylis glomerata L. var. saborto (25 kg ha⁻¹) + Trifolium repens L. group Ladino (4 kg ha⁻¹) + Trifolium pratense L. var. Marino (1 kg ha⁻¹); (2) Lolium perenne L. var. Tove (25 kg ha⁻¹) + Trifolium repens L. group Ladino (4 kg ha⁻¹) + Trifolium pratense L. var. Marino (1 kg ha⁻¹). The experiment began in the spring of 1995 using a randomized block design with three replicates in Castro Riberas de Lea (Lugo, Galicia, north-western Spain). Plot size was 12 × 8 m², with a 1 m buffer strip between plots. Two-year data showed that fertilization with either material had a positive effect on pasture production, with no significant difference between the two fertilization treatments. Tree growth in the milk sewage sludge plot was significantly higher than in the control plots. Inorganic fertilization increased pasture production, but affected tree growth negatively. The results show that milk sewage sludge could be used as a fertilizer in silvo-pastoral systems. This revised version was published online in June 2006 with corrections to the Cover Date.