橡胶间种砂仁模式下凋落物的特征

文章研究了橡胶＋砂仁胶园间种模式凋落物的年凋落总量和节律、凋落物组成、分解速率、营养元素及养分释放。结果表明：橡胶林下间种砂仁的胶园凋落物具有较多的热带季雨林的特征，总凋落量为７．６５ｔ／ｈｍ２·ａ，与海南岛山地雨林相近；凋落物组分中明显较高的叶含量形成了橡胶＋砂仁模式自己独特的凋落物组分比值；占凋落物总量３９．７％的砂仁枯落物，在胶砂复合生态系统的养分归还上占有十分重要的地位。     

橡胶与砂仁间作复合生态系统营养元素循环的研究

橡胶与砂仁间作和纯橡胶林两种林分营养元素净积累、归还及营养元素在植物、土壤之间生物循环的研究结果表明：间种砂仁可明显增加林分植物库中营养元素的含量，间作林中营养元素总积存量达３４４７．０７ｋｇ／ｈｍ２，是纯胶林的２．５３倍；营养元素总归还量每年每公顷为３６３．２６ｋｇ，是纯胶林的１．４４倍，其中Ｎ，Ｐ，Ｋ，Ｃａ，Ｍｇ的年归还量分别是纯胶林的１．９，２．５４，１．４２，１．０５，１．１６倍；间作林中的Ｎ的归还量为最大，纯胶林中以Ｃａ的归还量为最大，两种林分均以Ｐ的归还量为最小。间作林中营养元素的年吸收总量为１０８３．４３ｋｇ／ｈｍ２，是纯胶林的２．１倍。尽管营养元素的循环系数低于纯胶林，但吸收系数却高于纯胶林，可见间种有利于植物对土壤库中营养元素的吸收。     

白石山森林土壤有机质及氮,磷,钾养分状况研究

对太行山脉北端白石山不同类型森林土壤中氮、磷、钾养分全量及有效量进行了室内分析。结果表明：土壤有机质平均含量为１８．３７％￣１０６．３４ｇ／ｋｇ，全氮量为１．１１￣３．４３ｇ／ｋｇ，全钾量为２０．６９￣２５．４６ｇ／ｋｇ；碱解氮含量为３８．５￣２４４．３ｍｇ／ｋｇ，速效钾含量为１３３．２￣２１４．４ｍｇ／ｋｇ，有机质及氮、钾全量较高，有效供应较好；全磷量多低于０．８ｇ／ｋｇ，速效磷多低于１０ｍｇ／     

不同植被类型土壤理化性质及水源涵养功能研究

对丽水实验林场3种植被类型的土壤理化性质和涵养水源的功能进行了实验研究，结果表明，阔叶林、毛竹林土壤有机质含量相对较高，这2种林分可较好改善土壤养分状况；马尾松下的土壤pH值较低，酸性较强，土壤有效P含量高，各植被类型下的林地枯落物持水量大小依次是：阔叶林（16．453t／hm^2）〉毛竹林（7．142t／hm^2）〉马尾松林（2．656t／hm^2）；土壤持水量大小依次是：毛竹林〉阔叶林〉马尾松林。     

农林业复合生态系统沙兰杨－小麦－玉米群落类型氮、磷、钾再循环指数灵敏度分析

本文对黄淮海平原豫北地区农林业生态系统沙兰杨－小麦－玉米群落类型营养元素氮、磷、钾在系统内的分布、累积、循环进行了系统的研究，并对三种营养元素的再循环指数及其灵敏度进行了分析。结果表明：在植物组分库中，氮、磷、钾的年累积量分别为３１７．４３６，７０．９１７和２３８．７５８ｋｇ／ｈｍ２，年吸收量分别为３１０．４４４，６８．３２９和２２９．８０１ｋｇ／ｈｍ２；在枯落物库中，三种元素的年凋落量分别为２４．３５，３．７９和３３．９６ｋｇ／ｈｍ２·ａ；在０─８０ｃｍ的土壤库中，三种元素的全量分别为：２８５．５６，３４７．３８和４８９．４８ｇ／ｍ２，有效量分别为３６．８１，２６．５４和６２．８７ｇ／ｍ２；三种元素的归还率分别为５．０２％，３．１％和１０．５％，吸收系数分别为０．１１，０．０２和０．００４７，利用系数分别为０．９８，０．７６和０．９８，循环系数分别为０．０７８，０．０５５和０．１５。输出趋于减少的营养元素的再循环指数，植物凋落层对于增加再循环指数是最关键的。营养元素磷再循环指数的灵敏度比氮和钾大，即磷的循环过程是最不稳定的。     

N、P、K和石灰对咖啡产量的影响

Ｎ、Ｐ、Ｋ和石灰对咖啡产量的影响ＳＴＡＬＥＮ，Ｐ。等１９８４－１９８９年对１５龄咖啡（Ｓ．７９５）树进行了田间试验，Ｎ＋Ｐ２Ｏ５＋Ｋ２Ｏ年用量分别为１２０＋９０＋１２０、１６０＋１２０＋１６０、２００＋１５０＋２００或２４０＋１８０＋２４０ｋｇ／ｈｍ...     

杉木光皮桦混交林效益的调查研究

对桂西北杉木光皮桦混交林和杉木纯林的对比研究表明,３５年生杉桦混交林的立木蓄积量为４４１．０８７ｍ＾３／ｈｍ＾２,比杉木纯林高３．６％。混交林枯枝地层现存量及其Ｎ、Ｐ、Ｋ、Ｃａ、Ｍｇ五种元素的积累量分别为１３．１８ｔ／ｈｍ＾２和２９９．５ｋｇ／ｈｍ＾２,分别比杉木纯林高９．７％和６９．９％。８混交林地（０～１００ｃｍ）土壤容重为０．８１～１．２２ｇ／ｃｍ＾３,比杉木纯林低１．０％～８．０％,而土壤孔隙度,通气度和持水量分别比杉木纯林高２．０％～３．９％。土壤有机质、全氮、水解氮、有效磷和速效钾分别比杉木纯高５．５％～４９．８％。     

科尔沁沙地飞播造林治沙技术研究

经试验，在科尔沁沙地开展飞播造林，播区应选在平缓沙地上，播期以６月最好。可供飞播的植物种有山竹子、锦鸡儿、草木樨、沙打旺。最佳播种量单播时山竹子为２２．５ｋｇ／ｈｍ＾２，锦鸡儿为７．５￣１５ｋｇ／ｈｍ＾２，草木樨为４．５ｋｇ／ｈｍ＾２，沙打旺为７．５ｋｇ／ｈｍ＾２；混播时锦鸡儿＋草木樨＋沙打旺，播种量为（７．５＋４．５＋３）ｋｇ／ｈｍ＾２，播时种子应进行“大粒化”处理，播后对播区进行封禁保护。     

北方栗树营养状况及树体养分分配规律的研究

１９９５～１９９７年在辽宁，北京，天津和山东省市栗产区调查了栗园中栗树营养状况及养分分配规律，研究结果表明，凡每公顷产量超过２２５０ｋｇ，的栗园，土壤有机质含量〉１．２％；全Ｎ〉０．６６％，水解Ｎ〉９．６ｍｇ／１００ｇ，有效Ｐ〉０．６ｍｇ／１００ｇ，有效Ｋ〉４ｍｇ／１００ｇ。叶片中Ｎ，Ｐ，Ｋ含量分别为２．１％，０．１％和０．３５％，生殖器官Ｎ，Ｐ，Ｎ分别占５１．８％，６１．２％，７１．０５％；叶分     

油松林枯落物对坡面土壤侵蚀的影响

本文研究了油松林枯落物对林地坡面土壤侵蚀的影响，即土壤颗粒在雨滴击溅和冲刷作用下，枯落物对侵蚀性降水所引起的土壤流失有抑制作用，并对枯落物防止土壤侵蚀功能作一探讨。研究表明原状枯落物层（２ｃｍ厚）油松林下无溅蚀发生，去掉枯落物层有微量溅蚀发生；其侵蚀径流量由有枯落物覆盖地表的２３１５ｍ￣３／（ｋｍ￣２·ａ）较无枯落物的５９３７．５ｍ￣３／（ｋｍ￣２·ａ）减少６１．２４％，其侵蚀模数由有枯落物层的１．１４４ｔ／（ｋｍ￣２·ａ）较无枯落物层的８．９２ｔ／（ｋｍ￣２·ａ）减少８７．７１％，在该油松林集水区，因原状枯落物保护较好，所以在该流域无水土流失，起到了水土保持的作用。     

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.