基于3S技术的泗阳县杨树种植面积动态分析

利用3S技术,对泗阳县近20 a杨树种植面积的动态变化情况进行了分析。结果表明,1988～2006年间,泗阳县分别有23.00%的农田和8.15%的聚落转变成林地,杨树种植面积呈显著上升趋势,占国土面积的比例由11.95%提高到18.92%。从杨树林地斑块面积占比看,1988年10～100 hm2的杨树林斑块所占比例最大,约占所有杨树林面积的70%;由于近年来持续的大规模杨树造林,到2006年原有的杨树林斑块逐步连接形成大规模成片林,大于100 hm2的杨树成片林所占比例达到了约50%,杨树种植布局进一步得到优化。     

泗阳县林下种植主要模式及其发展潜力初步分析

对泗阳县杨树片林郁闭前的复合经营模式和郁闭后的中草药种植模式及其发展潜力进行了总结、分析,初步提出了适合泗阳县及周边地区不同林地的林农、林药高效复合栽培模式;并展望了发展林下中草药经济的前景,提出了其存在问题及对策。     

喀斯特地区低丘缓坡林地适宜性评价

为合理确定低丘缓坡土地开发为林地的适宜性,进而确定开发的空间和时序,选择了地形地貌、土壤和开发利用条件3类10个指标,建立了适用于喀斯特地区低丘缓坡林地适宜性评价指标体系;采用专家打分和层次分析法确定指标权重,并应用GIS技术对喀斯特地区低丘缓坡林地适宜性进行了评价。结果表明:高度适宜区面积为831.01 hm2,适宜区面积3 680.43 hm2,基本适宜区面积10 668.29 hm2,不适宜区面积785.56 hm2。坡度和相对高度是影响林地适宜性等级和空间分布的主导因素。     

基于GIS的林地生态适宜性评价——以青藏高原东部迭部益哇沟林区为例

为改善林地生态环境,提高林地资源利用价值,以迭部县益哇沟林区为研究区,运用GIS软件进行信息分析与处理,对研究区林地生态适宜性的影响因子(海拔、坡度、坡向、土壤成分、土壤机械组成)进行等级分级并分配权重,综合对研究区的林地生态适宜性进行分析评价.结果 表明:研究区树木生长状况较好,整体林地适宜性处于较优水平,属于Ⅰ等适...     

基于3S技术闽江入海口沿岸林地质量等级评价研究

以闽江入海口沿岸试验区林地为研究对象,对林地质量从数量结构及空间结构进行了探讨。结果表明,3级林地数量占绝对优势,占总面积的38.14%。其次是4级林地面积,占总面积的29.15%,1级和5级面积比例都较少,分别占总面积的6.44%和5.58%。林地质量综合分布,南部要优于北部,5级林地南部占多数。南部、北部所占比例分别为55%、45%;4级林地面积绝大部分分布于南部,南部、北部所占比例分别为73%、27%;3级林地面积北部分布较多,南部、北部所占比例分别为61%、39%;林地质量为1级的林地南部也较多,但总数量很少。南部、北部所占比例分别为89%、11%,面积分别为609hm2、75hm2。     

昆明市林地立地质量状况分析

在近期昆明市森林资源规划设计调查成果资料基础上进行补充调查,从坡度和土壤厚度2方面对昆明市林地立地质量状况进行分析．结果表明：全市立地质量较好的林地资源占全市林业用地面积的58．22％,适宜发展商品林：其余的41．78％为立地质量较差的林地资源,主导利用方向为以防护为主的公益林．林分质量分析结果,昆明市各林分立地条件类型单位面积蓄积量的大小反映了不同立地质量林地的林木生长水平差异．建议根据林地立地质量和林分质量进行合理布局,制定昆明市林业产业发展规划．     

巴彦淖尔市山地丘陵区林地立地类型划分及分布状况

文章在对巴彦淖尔市山地丘陵区林地立地类型进行划分的基础上,分析各立地类型在林地中的分布状况,同时计算不同立地类型乔木林的单位面积蓄积,从而为评价山地丘陵区林地立地质量、确定经营方向和编制林业规划提供理论依据.巴彦淖尔市山地丘陵区划分为9个立地类型组23个立地类型,其中石质丘陵中厚层土立地类型面积最大(131 366.7...     

基于GIS技术的区域主要桉树树种用地适宜性评价

使用地理信息系统(GIS)与数学模型集成技术,以福建省现状林地、果园、茶园、牧草地、荒草地、沙地以及裸土地为评价对象,建立了评价因子空间及属性数据库。使用250m栅格为基本评价单元,对福建省主要桉树树种土地适宜性、质量进行评价。结果表明,主要受地域热量状况及低温冻害的制约,福建省桉树树种及其无性系适宜用地资源主要分布于闽南沿海地区和闽中、闽西和闽北内陆低海拔地区。     

泗阳县南方型杨树林分栽植密度调查研究

根据对泗阳县南方型杨树林分调查结果表明 ,栽植密度对杨树生长量的影响十分明显 ,经济效益差异也很显著 ,建议对林龄 (或树龄 )未超过 4a的栽植密度不合理的林地进行密度调整。具体做法 :对 4m× 7m的成片林 ,每隔 3株间伐 1株 ;对小片林 ,若栽植的是 3行 ,将其株距进行调整 ,保持每株营养面积 30m2 左右 ;若栽植的是 3行以上 ,对密度为 1 5m× 1 5m和 2m× 2m的进行间伐 ,使其成为 6m× 6m的株行距 ,对密度为 2 5m× 2 5m的进行隔株隔行间伐 ,将其调整为 5m× 5m呈三角形的配置模式。对双行杨树 ,尽量将其株行距调整接近 4m。对林龄超过 5a以上 ,栽植密度不合理、生长又较差的林地或“四旁”林 ,可在采伐后按适宜密度重新栽植     

基于物元模型的长江流域森林植被恢复适宜性评价

以长江流域大于15°的坡耕地和裸地为评价对象,根据土地利用状况、植被景观格局和自然环境特点,建立了长江流域植被恢复适宜性评价指标体系,采用土地适宜性评价的物元模型分别对长江上游和中下游2个区域森林植被的恢复适宜性进行了评价,并在此基础上探讨森林植被恢复后的长江流域潜在森林植被格局。结果表明,长江流域适宜森林植被恢复的面积为54 103 km~2,占评价区域总面积的91.11%,主要分布在上游低海拔区域以及中下游地区;属于较适宜恢复等级的面积为2 945 km~2,占评价区域总面积的4.96%,分布在上游的山地和高山峡谷区;属于不适宜恢复等级的土地面积为2 336 km~2,占评价区域总面积的3.93%,主要分布在上游海拔4 000 m以上地区和高山峡谷区。采用价值当量法评估结果表明,森林植被恢复后长江流域生态系统服务功能价值将增加770.34亿元/a。     

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.