广州市石门伯乐树群落特征

伯乐树(Bretschneidera sinensis)为我国Ⅰ级重点保护植物,研究其种群及所在群落特征,对揭示其濒危机制及保护有重要意义。根据样方调查,对广州市石门国家森林公园伯乐树所在群落的种类组成、种群结构、群落外貌及特征进行分析。结果表明,在1 200 m2的样地中,有维管植物76种,隶属于44科65属,其中以热带性分布属占明显优势,所占比例为84.91%;群落分层明显,外貌终年常绿。生活型以中高位芽为主,占29.0%;按照Raunkiaer的频度等级定律,A级频度值为65.8;年龄结构不完整,大树、幼苗数量极少;植株多出现在沟谷旁斜坡的林缘或林窗,在群落演替过程中处于劣势地位。结实母株少、幼苗成活率低是制约伯乐树种群发展壮大的主要限制因子。为有效保护伯乐树,应加强伯乐树生物学、生态学特性和繁殖技术的研究。     

黄檗种群保护与发展的对策与技术措施

以吉林上营森林经营局适宜黄檗生长的林分为对象,调查其野生种群的生存现状,结果表明:黄檗占林分株数的8.7%,天然更新的幼苗幼树占12.5%,长势良好。要继续加强黄檗天然种群的保护力度,依法严格禁止采伐利用,并加强巡护,保护野生植株不被破坏;同时可采取人工造林、冠下植苗补植与直播种子造林、加强天然幼苗幼树抚育、建立珍惜珍贵树种培育基地等技术措施,增加黄檗种群数量。     

广东连州田心梅树冲伯乐树种群及其生境特征

伯乐树是国家Ⅰ级重点保护野生植物,其自然种群在广东连州田心梅树冲的个体数量较多。2013年用HOBO温湿度记录仪对其生境温湿度进行监测,同时测定土壤的理化特性、叶面光照强度、叶片生理生态特性、种群结构等,以分析伯乐树种群及其群落的生境特征。结果表明,生境2013年的年均气温17.356℃,年均相对湿度92.002％,符合中国伯乐树生境年均气温15℃以上,相对湿度80％以上的条件;土壤pH为6.38,有机质含量为0.50％,所测得的叶面光照强度小于旷地的10％。叶片SPAD值40.81-45.73,净光合速率3.53-4.07μmol/（m2·s）（以CO2计）,蒸腾速率0.90-1.40 mmol/（m2· s）（以H2O计）,水分利用效率2.91-3.92。2012年和2013年伯乐树种群为Poisson分布型;年龄结构、地径结构和树高结构均呈纺锤形,表明因受2008年初南岭地区冰雪灾害的影响,大树和更新层幼苗均受到破坏,为衰退种群。     

黄枝润楠林下更新幼树幼苗基本特征及分布类型

在南平茫荡山林下更新幼树幼苗调查的基础上,采用扩散系数、聚集指数、扩散指数、聚块性指数以及Cassie RM指数等几个聚集度指标判定其分布类型,并进行可信度验证。结果表明:黄枝润楠为绝对优势树种,对群落所在的森林生态系统的功能发挥起主导作用;群落中绝大部分种群幼树幼苗的分布类型为聚集分布,小部分树种幼树幼苗为均匀分布,仅栲树为随机分布,群落种群幼树幼苗总体上分布类型表现为聚集分布。     

稀珍树种——伯乐树

伯乐树属伯乐科,是一种适应性较强的树种。幼树较能耐荫、耐瘠,在深山沟谷或山岳的阔叶林中生长良好,结果累累,种源丰富,易于繁殖发展。通道发现的伯乐树,高达20多米,胸径60厘米以上,树干小枝均通直,平滑无     

赣江源自然保护区伯乐树次生林群落特征及种间关联性

本研究以石城县赣江源自然保护区内的伯乐树群落为研究对象,基于野外样地调查,对伯乐树生境特征和群落特征进行了初步的分析.结果表明:伯乐树分布在该保护区701～953 m的低山区域.群落共有植物17科24属29种.其中乔木7科9属12种,灌木10科15属17种,草本植物很少,物种组成相对简单,多样性较低.坡度和海拔是引起生境差异的重要因素,海拔、坡度以及MgO含量对物种分布的影响最大.乔木层的整体关联性表现出显著的负关联性,负关联种对居多,占总对数的51.5％,正关联对数占总对数的43.9％,无关联对数占总对数的4.5％;群落结构仍然处于不稳定阶段,而伯乐树与细叶青冈、山杜英呈现较好的正关联性,且细叶青冈在群落内重要值较大;而与罗浮栲呈现负关联性.因此,我们认为在对现有伯乐树种群进行保护时,需要结合其在不同阶段的生活习性,对林分进行全周期的管理,且正向关联的树种对于其幼苗更新有显著的作用.     

巴山北坡不同干扰条件下栓皮栎种群结构与动态

对巴山北坡2个干扰环境下的栓皮栎种群结构、数量动态和空间分布格局进行对比研究.种群A分布于较低海拔地区,距离居民点近,持续受到砍柴、放牧等强烈干扰,群落发育较差;种群B分布于较高海拔,远离居民点,受人为干扰少,群落发育较好.结果表明:A种群的更新能力较弱,幼龄个体数量少,并以萌生起源幼龄个体占优势,呈现衰退势态,种群B更新能力较强,幼龄个体数量丰富,以实生起源个体占优势,呈现持续发展势态;2个种群存活曲线均属于Deevey Ⅲ,在Ⅰ-Ⅲ龄期,幼苗死亡率最高;萌生苗在资源利用方面占有明显优势,在幼苗到幼树的生长转化过程中,比例逐渐增大;不同生境栓皮栎种群幼苗、小幼树、大幼树和大树均呈聚集分布,但种群聚集强度均随着年龄的增加而逐渐减小;对影响栓皮栎种群生长和发育的环境因素主成分分析表明,人为干扰是最主要的影响因子.在未来的经营和管理中,低海拔地区应尽量减少人为干扰和间伐频次,保留足够数量的结实母树,促进种群结实及种子成苗;应适时对高海拔地区种群进行抚育,间伐非目的树种,调整环境因素和种间关系.促进天然条件下种群结实和种子成苗.     

极小种群海南风吹楠种群的数量特征及动态

通过对广西分布区海南风吹楠野生资源的调查,从径级结构、静态生命表、存活曲线以及乔木重要值等方面,分析了海南风吹楠种群的生态学特征。结果表明:(1)海南风吹楠种群径级结构呈典型的倒J型,偏态分布极为明显,种群结构大致趋于稳定型,但径级结构、幼苗库存在明显不均衡性。(2)存活曲线趋于Deevey-Ⅱ型,幼苗阶段的高死亡率是导致其种群濒危的重要原因,且光因素是该树种生长和种群发展的限制性环境因子。(3)海南风吹楠在5龄级以前,树高与胸径的增长几乎呈线性相关,此后开始变缓。(4)海南风吹楠在群落中的竞争优势不明显,6龄级以后消失率增高。针对海南风吹楠濒危的原因,对现有种群进行适度人工干预,提高幼苗至幼树的转化率,加强片段化居群间的基因交流是当前海南风吹楠种群恢复的关键。     

南岭山地伯乐树天然种群和人工种群遗传多样性比较

为评价伯乐树迁地保护林的遗传完整性,采用ISSR分子标记技术对南岭山地伯乐树2个人工种群和4个天然种群的遗传多样性进行分析比较。结果显示:7条引物共检测出86个条带,其中62条为多态条带;各种群多态条带百分比(PPB)和Shannon表型多样性指数(HPOP)分别为36.05%～53.49%和0.2040～0.3079;天然种群PPB和HPOP分别为70.93%和0.3882,高于人工种群(PPB=53.49%,HPOP=0.2941)。分子方差分析(AMOVA)表明,天然种群的遗传分化(ΦST=0.3407)明显高于人工种群(ΦST=0.2248)。研究结果认为,伯乐树在物种水平和种群水平都具有较高的遗传多样性,已建立的迁地保护种群不能有效地保护南岭地区天然种群的遗传完整性,建议营建人工迁地保护种群尽可能地从多个不同种群中收集种质材料。     

不同生境香果树种群的径级结构与分布格局

应用"相邻格子法"对不同生境下的香果树种群进行每木调查,获得野外资料.采用空间代替时间的方法,研究香果树的径级结构和分布格局,以及应用泊松方差/均值比、负二项式分布、Lloyd平均拥挤度指数和聚块指数4个指标分析其种群格局状况.结果表明:不同生境下的香果树径级结构具有较大的相似性--均缺乏幼苗和幼树,种群呈衰退趋势;不同生境下的香果树种群聚块规模为8～32 m2;种群的空间分布格局主要为集群分布;格局动态明显呈现由集群分布到随机分布的扩散趋势.建议采取相应的措施保护母树,尤其是20年生以上的母树;还应加强对种子及幼苗生长动态变化的研究.     

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.