兴安落叶松老龄林落叶松林木死亡格局以及倒木对更新的影响

对兴安落叶松老龄林落叶松林木死亡格局和死亡木对更新的影响进行了研究 .结果表明 ,丛桦落叶松林和杜香落叶松林的枯立木以中径木占多数 ,赤杨落叶松林主要为中、大径木 ,草类落叶松林主要是中、小径木 .落叶松枯立木主要因火烧、受压和老死而形成 .丛桦落叶松林和赤杨落叶松林掘根倒木较多 .杜香落叶松林和草类落叶松林的倒木以风折为主 .地形、山体走向和盛行风向对树倒方向影响很大 .丛桦落叶松林倒木方向杂乱 ,赤杨落叶松林林木均向东倒下 ,杜香落叶松林和草类落叶松林的掘根木分别向南、东北方倒下 ,两者的风折木倒向随机性较大 .草类落叶松和赤杨落叶松老龄林内 ,倒木更新为 1 8和 40株·m- 2 ,远远高于矿物土基质上 2株·m- 2 的水平 .丛桦落叶松林内倒木和林地上更新均相当好 ,约为 2 8株·m- 2 .杜香落叶松林倒木更新效果不突出 .     

促进兴安落叶松天然更新的出苗条件研究

根据４０多块标准地调查,促进更新措施后兴安落叶松１年生幼苗出现的频度及数量与种子年关系很大,幼苗更新效果最好的是种子年当年,更新频度可达６０％以上,幼苗平均为１．０—２．０×１０３株·ｈａ－１,其他年份促进的效果较差．同时,也与迹地类型、种源状况和整地质量关系较大．一般在山坡中、下部,土壤湿润的杜香落叶松和藓类越桔落叶松林迹地促进效果较好,其更新频度为６０—７０％．绝大部分更新幼苗出现在表土裸露、无杂草灌木、土壤湿润的地方．更新频度与植被盖度呈明显的衰减指数相关．促进地块距下种林墙最好不超过６０ｍ范围．     

兴安落叶松种群格局的分形特征——关联维数

种群格局关联维数揭示出个体空间关联的尺度变化规律,表明种群个体的空间相关程度。采用关联维数对大兴安岭兴安落叶松种群格局的研究表明,各类兴安落叶松林中兴安落叶松种群格局具有较高的关联维数（接近２）,个体空间关联程度较高,其次序为杜鹃－兴安落叶松林（１．７４６）＞草类－兴安落叶松林（１．７４０）＞越桔－兴安落叶松林（１．５５０）＞杜香－兴安落叶松林（１．４６８）。兴安落叶松－白桦林中兴安落叶松种群格局的关联维数较小（＜１．５１２,远离２）,个体间关联较弱,处于劣势伴生地位。通过将各天然森林类型与兴安落叶松人工林比较显示,个体空间相关程度由高至低的次序为兴安落叶松人工林（１．７６２）＞兴安落叶松天然林（１．６２６）＞兴安落叶松－白桦林（１．４３４）,揭示出兴安落叶松种群在不同森林类型中个体空间关联的尺度变化的差异。文中还对综合运用各种分形维数揭示种群格局尺度变化特征的问题进行了讨论。     

兴安落叶松种群格局的分形特征信息维数

种群格局信息维数能够刻划格局强度的尺度变化程度,揭示出种群个体分布的非均匀性状况。采用信息维数对大兴安岭兴安落叶松种群格局的研究显示,各类兴安落叶松林中兴安落叶松种群格局的信息维数大小依次为越桔－兴安落叶松林（１．４８０）＞杜香－兴安落叶松林（１．３７３）＞杜鹃－兴安落叶松林（１．３２１）＞草类－兴安落叶松林（１．０９３）。虽为群落建群种,兴安落叶松种群格局的信息维数较低（＜１．５,远离２）,格局     

不同林型兴安落叶松林火烧迹地物种组成及多样性研究

以内蒙古大兴安岭兴安落叶松林火烧迹地为研究对象,采用分层取样的方法对群落中植被进行了调查,分析比较了3种不同林型兴安落叶松林群落恢复过程中物种组成及多样性的差异。结果表明:不同林型兴安落叶松林群落各层α多样性指数总体表现为草本层灌木层乔木层。不同林型兴安落叶松林火烧迹地群落恢复12年后,草本层的Simpson和Shannon-Wiener指数均小于对照样地并呈现出草类-兴安落叶松林杜香-兴安落叶松林杜鹃-兴安落叶松林的趋势,而在灌木层则各指数均大于对照样地并呈现出草类-兴安落叶松林杜鹃-兴安落叶松林杜香-兴安落叶松林的趋势。     

应用色赤杨营造防火林带试验研究

在落叶松林地对色赤杨林带进行护林阻火试验表明，色赤杨是一种速生耐火树种，５～６ａ后其郁闭度可达０．９以上；林带下可燃物较其它阔叶树少，仅为０．８ｋｇ·ｍ－２；春秋２季火险期内较安全，自然阻火作用明显     

大兴安岭地区林下土壤酶活性对冻融交替的响应

以寒温带偃松林、杜鹃-白桦林、杜鹃-落叶松林和杜香-落叶松林4种典型林分下土壤为研究对象,采用室内冻融模拟培养方法,研究冻融循环次数(0、1、3、5、7、15次循环)对各林分不同土层脲酶、蔗糖酶和蛋白酶活性的影响,分析冻融过程中各林分下土壤酶活性与多元理化变量间的相关性。结果表明：冻融对土壤脲酶活性呈先提高后抑制作用,冻融结束后其活性较未冻融均无显著变化;冻融对蔗糖酶活性呈先抑制后提高作用,冻融结束后蔗糖酶活性显著提高8.5%～40.3%;冻融对蛋白酶活性呈先提高后抑制作用,冻融结束后蛋白酶活性显著降低13.8%～68.9%。冻融结束后,杜香-落叶松林和偃松林下脲酶分别与铵态氮和含水量呈显著正相关,偃松林、杜鹃-白桦林和杜香-落叶松林下蛋白酶与无机氮化合物呈显著负相关。杜鹃-落叶松林和杜香-落叶松林下蔗糖酶与有机质呈显著正相关。     

宝天曼自然保护区栓皮栎林生物量和净生产力研究

对河南内乡宝天曼自然保护区４５年生天然次生栓皮栎林的生物量和净生产力的研究表明,栓皮栎林生物量为１６７．６４１７ｔ·ｈｍ－２,其中乔木层为１５８．８３８２ｔ·ｈｍ－２,占总量的９４．７５％;该林净生产力为８．４８８０ｔ·ｈｍ－２·ａ－１,其中乔木层为７．９２５４ｔ·ｈｍ－２·ａ－１,生物量平均相对生长速率为０．０４１．灌木层的生物量和净生产力分别为０．０６９４和０．０４５６ｔ·ｈｍ－２·ａ－１;而草本层的分别为０．１０４１和０．０９０８ｔ·ｈｍ－２·ａ－１．凋落物现存量为８．６３ｔ·ｈｍ－２,凋落物量为５．０３９５ｔ·ｈｍ－２·ａ－１,分别占总量的５．１５％及５９．３７％．净生产量与叶面积指数、叶量成正比关系,而与叶效率呈负相关关系．     

1980—1999年大兴安岭灌木、草本和地被物林火碳释放估算

应用排放因子法,对大兴安岭林区1980-1999年间主要森林类型中灌木、草本和地被物因森林火灾释放的碳量及主要含碳温室气体量进行了估算．结果表明：不同森林类型灌木、草本和地被物的排放因子不同,以杜香-兴安落叶松林的灌木、草本和地被物层CO2排放因子最大,为93．08％,樟子松林最小,为82．56％;樟子松林CO和CxHy排放因子最大,分别为10．25％和0．84％,杜香-兴安落叶松林最小,分别为6．55％和0．30％．结合灌木、草本和地被物层生物量和碳储量数据,得出20年间大兴安岭典型森林类型灌木、草本和地被物层因森林火灾释放的总碳量为6．56Tg,年平均0．33Tg,约占全国森林火灾碳释放量的11．55％～16．30％;直接释放的含碳温室气体22．03Tg,其中CO2的释放量占总释放量的85．20％,CO占总释放量的14．21％,CxHy占总释放量的0．59％．     

磷胁迫条件下落叶松幼苗对难溶性磷的利用

以ＡｌＰＯ４为Ｐ源在温室内采用砂培的方法,研究了落叶松（Ｌａｒｉｘ ｇｍｅｌｉｎｉ）２年生幼苗对难溶性Ｐ酸盐的利用状况。结果表明,落叶松幼苗可以利用一定数量的ＡｌＰＯ４。在供ＡｌＰＯ４不接种菌根菌时,落叶松幼苗吸收的Ｐ可达正常供Ｐ时的３５．１％和６４．９％。不同菌种对落叶松幼苗利用ＡｌＰＯ４的影响不同。接种点柄乳牛肝菌（Ｓｕｉｌｌｕｓ ｇｒａｎｕｌａｔｕｓ）时,落叶松幼苗对ＡｌＰＯ４的利用量高于不     

海南岛热带低地雨林刀耕火种弃耕地自然恢复过程中的群落构建

研究群落构建机制是群落生态学的一个重要目标, 群落动态过程中的构建规律对于了解群落演替机理有重要的作用。该文以海南岛刀耕火种干扰后自然恢复的10 hm ²热带低地雨林为研究对象, 通过比较不同恢复阶段的次生林(15年、30年和60年)和老龄林在幼苗、幼树和成年树群落的物种组成, 揭示次生演替过程中的群落构建规律。研究结果表明, 老龄林中不同径级群落的物种多样性及不同径级间的物种相似度显著高于各恢复阶段的次生林, 但优势种在群落中的比例低于各恢复阶段的次生林。随着自然恢复过程的进行, 次生林群落物种组成与老龄林的相似性也逐渐增大, 支持演替平衡理论。所有恢复阶段样地中幼苗的个体、物种丰富度和基于多度涵盖估计量(ACE)都低于幼树和成年树群落, 幼苗层物种组成与幼树、成年树也有较大差异, 说明新增到幼苗群落可能是一个难于预测的过程。研究结果说明了确定过程和随机过程共同决定了次生演替的群落构建。     

落叶松水浸液对胡桃楸种子萌发和幼苗生长的影响

研究了落叶松水浸液对胡桃楸种子萌发和幼苗生长的影响.结果表明,与对照相比,25 g ·kg^-1浓度的落叶松根水浸液,125 g·kg^-1浓度的落叶松皮、枝水浸液对胡桃楸种子发芽率、发芽指数均表现出显著的促进作用（P＜0.05）;12.5 g·kg^-1和25 g·kg^-1浓度的落叶松根水浸液、12.5 g·kg^-1浓度的落叶松皮水浸液对胡桃楸幼苗苗高、地径生长的促进作用显著（P＜0.05）.高浓度的落叶松叶水浸液对胡桃楸种子萌发和幼苗生长具有明显的促进作用（P＜0.05）.而落叶松叶水浸液对胡桃楸种子发芽率、发芽指数、苗高以及地径的促进作用却随着水浸液浓度的降低,呈逐渐下降的趋势.施加落叶松水浸液对胡桃楸种子萌发以及幼苗生长的促进作用可能与树种间的化学相互作用有关.     

The contribution of understory light availability and biotic neighborhood to seedling survival in secondary versus old-growth temperate forest

Seedling survival plays an important role in the maintenance of species diversity and forest dynamics. Although substantial gains have been made in understanding the factors driving patterns of seedling survival in forests, few studies have considered the simultaneous contribution of understory light availability and the local biotic neighborhood to seedling survival in temperate forests at different successional stages. Here, we used generalized linear mixed models to assess the relative importance of understory light availability and biotic neighborhood variables on seedling survival in secondary and old-growth temperate forest in north eastern China at two levels (community and guild). At the community level, biotic neighborhood effects on seedling survival were more important than understory light availability in both forests. In both the old-growth and secondary forests, conspecific basal area had a negative effect on seedling survival, consistent with negative conspecific density dependence. At guild levels, the relative importance of light and biotic neighborhood on seedling survival showed considerable variation among guilds in both forests. Available understory light tended to have positive effects on seedling survival for shrub and light-demanding species in the old-growth forest, but negative effects on survival of shade-tolerant seedlings in the secondary forest. For tree species and shade-tolerant species, the best fit models included neighborhood variables, but that was not the case for shrubs, light-demanding, or mid shade-tolerant species. Overall, our results demonstrate that the relative importance of understory light availability and biotic factors on seedling survival vary with species life-history strategy and forest successional stage.     

Dispersal ecology of the endangered woodland lichen Lobaria pulmonaria in managed hemiboreal forest landscape

Changes in the forest management practices have strongly influenced the distribution of species inhabiting old-growth forests. The epiphytic woodland lichen Lobaria pulmonaria is frequently used as a model species to study the factors affecting the population biology of lichens. We sampled 252 L. pulmonaria individuals from 12 populations representing three woodland types differing in their ecological continuity and management intensity in Estonia. We used eight mycobiont-specific microsatellite loci to quantify genetic diversity among the populations. We calculated the Sørensen distance to estimate genetic dissimilarity among individuals within populations. We revealed that L. pulmonaria populations have significantly higher genetic diversity in old-growth forests than in managed forests and wooded meadows. We detected a significant woodland-type-specific pattern of genetic dissimilarity among neighbouring L. pulmonaria individuals, which suggests that in wooded meadows and managed forests dominating is vegetative reproduction. The vegetative dispersal distance between the host trees of L. pulmonaria was found to be only 15–30 m. Genetic dissimilarity among individuals was also dependent on tree species and trunk diameter. Lobaria pulmonaria populations in managed forests included less juveniles compared to old-growth forests and wooded meadows, indicating that forest management influences life stage structure within populations. We conclude that as intensive stand management reduces the genetic diversity of threatened species in woodland habitats, particular attention should be paid to the preservation of remnant populations in old-growth habitats. Within managed habitats, conservation management should target on maintenance of the stand’s structural diversity and availability of potential host trees.     

Long-term persistence of aspen – a key host for many threatened species – is endangered in old-growth conservation areas in Finland

Large, dead and dying European aspens (Populus tremula L.) host many threatened species in Fennoscandian boreal forests. Large aspen trees have mostly disappeared and are being harvested from the managed forests that cover 95% of the forest area in Finland. Due to the small area protected (4.1%), the aspen-associated species may encounter major difficulties in the protected areas if aspen trees disappear due to natural forest succession. The availability of aspens was assessed in the old-growth conservation area network in eastern Finland. We mapped all the living and dead aspens in 15 protected old-growth forests. The total number of counted trees was 32 903 individuals. Current amounts of living (2.7 m³/ha) and especially dead aspens (2.8 m³/ha) in the protected areas were higher than in the surrounding managed forests (1.1 and 0.1 m³/ha for living and dead trees, respectively). However, while saplings (dbh<5 cm) occur in most of the areas (12 individuals/ha on average) they survive poorly and young aspen cohorts (5 cm <dbh<15 cm) are lacking or are very rare. The most likely reason for the poor sapling survival is high browsing pressure by the mammalian herbivores, especially the moose. The moose population has increased many times in Finland during the past decades. The poor regeneration of aspens implies that the value of the old-growth conservation areas for aspen-associated species will face a serious bottleneck within a few decades when the currently middle-aged tree cohorts disappear. If the current high browsing pressure and lack of natural disturbances continue the obligatory aspen-associated species may disappear both locally and regionally from the network of the protected areas.     

Diversity of Medicinal Plants among Different Forest-use Types of the Pakistani Himalaya

Diversity of Medicinal Plants among Different Forest-use Types of the Pakistani Himalaya Medicinal plants collected in Himalayan forests play a vital role in the livelihoods of regional rural societies and are also increasingly recognized at the international level. However, these forests are being heavily transformed by logging. Here we ask how forest transformation influences the diversity and composition of medicinal plants in northwestern Pakistan, where we studied old-growth forests, forests degraded by logging, and regrowth forests. First, an approximate map indicating these forest types was established and then 15 study plots per forest type were randomly selected. We found a total of 59 medicinal plant species consisting of herbs and ferns, most of which occurred in the old-growth forest. Species number was lowest in forest degraded by logging and intermediate in regrowth forest. The most valuable economic species, including six Himalayan endemics, occurred almost exclusively in old-growth forest. Species composition and abundance of forest degraded by logging differed markedly from that of old-growth forest, while regrowth forest was more similar to old-growth forest. The density of medicinal plants positively correlated with tree canopy cover in old-growth forest and negatively in degraded forest, which indicates that species adapted to open conditions dominate in logged forest. Thus, old-growth forests are important as refuge for vulnerable endemics. Forest degraded by logging has the lowest diversity of relatively common medicinal plants. Forest regrowth may foster the reappearance of certain medicinal species valuable to local livelihoods and as such promote acceptance of forest expansion and medicinal plants conservation in the region.     

Effects of plant leachates from four boreal understorey species on soil N mineralization, and white spruce (Picea glauca) germination and seedling growth

BACKGROUND AND AIMS: Natural regeneration of white spruce (Picea glauca) after disturbance has been reported to be very poor. Here a study was made to determine whether C compounds released from understorey species growing together with white spruce could be involved in this regeneration failure, either by (1) changing soil nutrient dynamics, (2) inhibiting germination, and/or (3) delaying seedling growth. METHODS: Foliage leachates were obtained from two shrubs (Ledum palustre and Empetrum hermaphroditum) and one bryophyte (Sphagnum sp.) with high phenolic compound concentrations that have been reported to depress growth of conifers in boreal forests, and, as a comparison, one bryophyte (Hylocomium splendens) with negligible phenolic compounds. Mineral soil from a white spruce forest was amended with plant leachates to examine the effect of each species on net N mineralization. Additionally, white spruce seeds and seedlings were watered with plant leachates to determine their effects on germination and growth. KEY RESULTS: Leachates from the shrubs L. palustre and E. hermaphroditum contained high phenolic compound concentrations and dissolved organic carbon (DOC), while no detectable levels of C compounds were released from the bryophytes Sphagnum sp. or H. splendens. A decrease in net N mineralization was determined in soils amended with L. palustre or E. hermaphroditum leachates, and this effect was inversely proportional to the phenolic concentrations, DOC and leachate C/N ratio. The total percentage of white spruce germination and the growth of white spruce seedlings were similar among treatments. CONCLUSIONS: These results suggest that the shrubs L. palustre and E. hermaphroditum could negatively affect the performance of white spruce due to a decrease in soil N availability, but not by direct effects on plant physiology.     

川西亚高山暗针叶林恢复过程中岷江冷杉天然更新状况及其影响因子

在川西亚高山米亚罗林区海拔3 100~3 600 m阴坡、半阴坡, 以立地条件基本一致的箭竹和藓类林型不同恢复阶段(20~40 a生的箭竹阔叶林、50 a生的箭竹针阔混交林、160~200 a生的箭竹原始暗针叶老龄林; 20~40 a生的藓类阔叶林、50 a生的藓类针阔混交林、160~200 a生的藓类原始暗针叶老龄林)的群落为研究对象, 共设置了50个样方(20 m×20 m), 采用空间代时间的方法分析了岷江冷杉(Abies faxoniana)的天然更新状况, 并采用通径分析法对其影响因子进行分析。结果表明: 箭竹和藓类两种森林类型岷江冷杉幼苗、幼树和小树的密度偏低。对于箭竹林型不同恢复阶段, 岷江冷杉幼苗密度＜幼树密度＜小树密度; 对于藓类林型不同恢复阶段, 藓类阔叶林幼树密度大于幼苗和小树密度, 藓类针阔混交林小树密度大于幼苗和幼树密度, 而藓类原始暗针叶老龄林幼苗密度大于幼树和小树密度。藓类林型岷江冷杉天然更新状况好于箭竹林型。对箭竹林型而言, 影响岷江冷杉天然更新的关键因子为母树密度、倒木蓄积量、箭竹盖度和苔藓层厚度, 其中母树密度和倒木蓄积量对岷江冷杉天然更新起着促进作用, 箭竹盖度和苔藓层厚度对岷江冷杉天然更新起着阻碍作用; 对于藓类林型而言, 影响岷江冷杉天然更新的关键因子为灌木盖度和苔藓层厚度。灌木和苔藓有利于幼苗的发生, 但不利于幼苗向幼树、小树的过渡。     

大兴安岭北部兴安落叶松种子在土壤中的分布及其种子库的持续性

 种子年后原始老龄林下自然散布的兴安落叶松土壤种子极为丰富,有生活力的土壤种子数量为190～320粒／m2,并且不同林型间有显著差异。70%～80%的种子主要居于土壤表层2～4cm范围内。落叶松老龄林种子年后第一年夏季土壤中丰富的种子即锐减,土壤中大多数种子的生活力保持1年,少数稍长,也不超过2年。显然,落叶松土壤种子库属于间断类型。人工撒播种子试验结果表明,位于土壤浅层(0～10cm)的种子生活力保存只1年,而深层(10～20cm)尽管对种子生活力保持有利,也不能超过2年。土壤病害是种子致死的重要原因。