三峡库区典型森林植被类型对坡面产流影响

在一定地形地貌基础上,植被与降水是决定坡面产流、产沙量的主要因素.2005～2006年对重庆缙云山4个天然林地径流场和农地径流场进行定位观测,结果表明:①森林植被在一定范围内对坡面径流量有削减作用,前期降雨对坡面径流有影响;②坡面径流峰值与暴雨峰值呈一一对应关系,马尾松和常绿阔叶林的变化幅度较小,楠竹林和常绿阔叶灌丛变化较大;③地下径流深与降雨量呈一一对应关系,地下径流深与降雨量关系反映出前期降雨对地下径流量的影响;④马尾松阔叶混交林、常绿阔叶林和常绿阔叶冠丛地下径流峰值的总体趋势是随降雨强度的增加而增加;楠竹林和农地随降雨强度的增加而呈下降趋势.     

不同退耕还林模式对地表径流及土壤物理性状影响的研究

通过对辽东山区退耕还林综合效益监测场不同恢复模式3 a连续的定点观测,结果表明:坡耕地在退耕后具有较强的植被自然恢复能力,生态防护功能增强,人工辅助措施能加速植被恢复速度;退耕后对水土流失的控制作用显著,年均减少泥土流失量达103.91 g·m~(-2)以上,总体防护效果呈现为自然区>乔灌区>乔木区>对照区;退耕还林还草一定程度地改善了土壤的物理性状,土壤的渗透性能增强,提高了坡地的水土保持能力。     

苦竹＋扁穗牛鞭草退耕种植模式植被结构特征分析

洪雅县在实施退耕还林还草工程中，选择土壤条件较好的地段营造苦竹（Pleioblastus）、撑绿杂交竹Bambusa pervariabilis×Dendrocala mopsis）、楠竹（Phyuostachys pubesens）、慈竹（Neosinocalamus affinis）与优质牧草扁穗牛鞭草（H．compressa L．f.）的立体种植植被恢复模式，利用退耕还林还草工程的契机栽竹种草大力发展奶牛、奶羊等养殖业和生产竹材，逐步调整农村产业结构。本文就苦竹＋牛鞭草退耕种植后的植被变化特征作简要分析。     

南方红壤区不同管理模式下的马尾松林水沙特征与植被作用

基于标准坡面径流小区观测,比较不同雨量水平植被对地表径流量的贡献,同时利用水文功能连通性原理和灰色关联法对相关土壤和植被参数进行比较。结果表明:①小区减流减沙效果为“林下流”<封禁管理<马尾松纯林<人工乔灌草混交;②地上和地下的植被特征对坡面水文过程阻抗明显;③相关参数的影响程度为土壤含水量<植被盖度<植被高度<有机质含量。不同雨量下小区水沙过程不相一致,小区尺度上植被特征对坡面水土保持起重要作用。     

闽东北鹫峰山不同迹地与不同植被恢复模式对径流的影响

指出了在闽东北鹫峰山对不同迹地采取不同植被恢复模式所造成的地表径流和泥沙流失不尽相同.通过分析能够减少地表径流和泥沙流失的排序为:人工造林模式＜人工促进天然更新模式＜天然更新模式和采伐迹地＜退耕农地＜火烧迹地＜矿山迹地.经过4年植被恢复,所有迹地上的植被均已郁闭,地表径流深显著变小,泥沙流失得到有效控制;以采伐迹地(B2)和退耕农地(B3)上采用人工造林模式(A1)的样地植被,具有较强的保水和固土能力,产生土壤侵蚀的地表径流深最小(二者分别为17.6mm和10.3mm),流失泥沙量也最少(二者分别为0.5g.m-2和0.4g.m-2).     

贵州开阳喀斯特山地几种不同植被类型的地表径流研究

对贵州开阳喀斯特山地几种不同植被类型,用设置径流小区方法,观测降雨量及径流量,对各种植被类型的地表径流进行比较。结果表明:几种植被类型中,全年的地表径流量为:退耕还林新造林>针叶林>针阔混交林>阔叶林>灌木林。不同植被类型对径流有着不同的调节作用,几种植被对径流的调节作用大小为:灌木林>阔叶林>针阔混交林>针叶林>退耕还林新造林。     

广西龙桥林区不同植被类型水文效益的研究

1985～1987年,在广西龙桥林区,对杉木、马尾松人工纯林和柠檬桉与马尾松人工混交林,以及天然灌木草本群落4种不同植被类型对降水的截留、地表径流及调蓄功能等水文效益进行测定,结果表明,对降水的截留效果以马尾松林为最好,混交林次之,杉木林较差,在同一植被类型的不同层次,以乔木层的截留量占绝对优势;对减少地表径流和延缓洪峰的效果,以层次结构较为复杂的混交林最佳。在同一植被类型内部结构特征的诸因子中,活地被物层的总盖度和草本层的生物量,是影响地表径流的主导因子:植被土壤对降水的调蓄功能,以混交林为最好。其他3种植被类型差异不大。说明在山地防护林建设中,营造针阔叶混交林,使其形成复层林,并保护好灌木草本层和死地被物层,对增强森林的调蓄能力具有重要的意义。     

辽东山区退耕还林地植被恢复调查研究

辽东山区是辽宁省重要的水源涵养基地和中部城市群的天然绿色屏障,在退耕还林过程中选择不同的植被恢复模式对退耕地植被群落的发育演替、生态功能的发挥具有不同的作用。文章通过对草河口退耕还林监测场植被恢复不同模式连续3年的调查研究认为,辽东山区在坡耕地退耕之初的几年内,植被自然恢复比较快,生态功能也比较强,但人工辅助措施能加快植被恢复进程,尤其是乔灌模式植被群落发育最好,为生态功能的发挥提供了必要的物质基础。     

退耕还林工程对会泽县农户的影响

截至2005年,会泽县退耕还林(草)面积为1.67万hm2,预计30a后活立木蓄积可增加39万m3.退耕地水土流失明显减少,地表径流比退耕前显著下降.于2006年5月在金钟镇5个有代表性的自然村共抽取了50户退耕农户进行调查,经分析认为,退耕还林(草)工程的实施对农户生产生活的影响主要是:推动了农户土地利用结构调整,使土地利用的可持续性增加;各类农作物种植结构变化不大,农产品产值结构变动较大;提高了农户总体福利水平.提出了保障工程可持性的对策和措施:对剩余劳动力进行技能培训,促进农户收入多元化,建立生态效益补偿制度等.     

渗透坡面林地地表径流运动的有效糙率研究

在流域水文学研究与应用领域中,坡面水流占有十分重要的地位,但如何获取坡面水流的有效糙率是至关重要的一步。本文针对林地地表径流运动的形成过程和运动特点,建立了林地渗透坡面地表径流运动基本方程,通过讨论土壤水分运动和地表径流运动参数,将土壤水分运动简化为一维Ｓｍｉｔｈ－Ｐａｒｌａｎｇｅ模型,地表径流简化为运动波模型,采用一步Ｌａｘ－Ｗｅｎｄｒｏｆｆ有限差分格式进行数值模拟,以最小离差平方和为目标函数,通过叠代计算获取林地地表径流的有效糙率。根据人工模拟降雨地表径流过程实测资料计算了油松林、刺槐林、蒙古栎林３种林分的有效糙率,计算结果表明,２２ａ生刺槐林地的最大,在０．１９３１～０．２１３１之间;其次为３０ａ生蒙古栎林地,为０．１７０１;２０ａ生油松林地为０．１４２３。从参数寻优的结果来看,ｍ值在２．７６～３．０９０     

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.