神农架地区米心水青冈林和锐齿槲栎林的格局与过程

本文对神农架地区广泛分布的米心水青冈林和锐齿槲栎林的种群和群落学特征、干扰历史、更新策略、生物量、生产量及元素循环特征进行了研究。得到如下结论： 1 米心水青冈林是神农架地区山地垂直分布的地带性植被类型，主要群落学特征为：（1）建群种明显，该区域主要有2种类型，即米心水青冈林和米心水青冈、锐齿槲栎林;（2）群落结构简单，但物种组成丰富，在6600m~2样地中出现高等植物（不含苔藓植物）77科150属271种，组成种类以蔷薇科、百合科、忍冬科、虎耳草科、樟科、杜鹃花科和壳斗科为主;（3）群落乔木层（占重要值的12％）和灌木层（占盖度的15％）中含有一定比例的常绿树种;（4）群落生活型以高位芽植物（70.89%）占绝对优势，其次为地面芽植物（15.50%）和地下芽植物(12.92%)。 2 米心水青冈是多主干的树种，萌枝现象普遍，但萌枝数量不同地点差异较大。通过萌枝产生的枝群体平均密度为257 ± 99.3n•hm~(-2)。枝群体的年龄结构表现为“幼龄个体数目较多型”和“中国年龄阶段数目较多型”，并且有较多的枝群体表现出一致的年龄结构。从整个群落米心水青冈的年龄结构来看，表现出发展型种群的特点。枝群体的分布格局为随机分布。9丛米心水青冈完整的年轮分析结果表明，它们萌枝的时间不是边疆的，而与森林的受干扰有关。根据83个圆盘和生长锥芯资料，米心水青冈在萌枝后成长为乔木层或林冠层的过程中，径向生长表现为5种模式。这是丛株内竞争的结果。萌枝在米心水青冈林的维持和发展过程中，具有重要的生态学作用。 3 锐齿槲栎林是神农架地区山地垂地分布的地带性植被类型，主要群落学特征为：（1）建群种明显，该区域主要有2种类型，即锐齿槲栎林和锐齿槲栎、米心水青冈林;（2）群落乔木层和灌木层中含有一定比例的常绿树种，和暖温带的落叶栎林有较大差异;（3）群落物种组成丰富，不仅具有典型的温带科属，还有典型亚热带分布的科属，组成种类主要以蔷薇科、百合科、忍冬科、虎耳草科、山茱萸科、杜鹃花科、壳斗科和樟科;（4）生活型以高位芽植物（66.32%）占绝对优势，其次为地面芽（23.51%）和地下芽（9.47%）植物。 4 通过样地调查、树干解析及直径分析法，对米心水青冈林和锐齿槲栎林受压和释压历史及更新策略进行了研究。米心水青冈直径生长表现为5种模式。而锐齿槲栎只表现为2种模式。85.9 ± 6.9%的米心水青冈有过受压过程，平均受压2.1 ± 0.8次，平均受压时间为47 ± 24.1a，最长受压时间73a，平均释压次数为1.6 ± 0.7次，平均释压时间为23 ± 21.5a，而60.83%的锐齿槲栎都均有1次受压。平均受压时间为19 ± 14a，受压后没有表现出释压过程。结合高生长和径向生长，认为米心水青冈是耐阴树种，它的更新策略是在林下形成苗性萌枝，在有林窗形成时释压生长进入乔木层;而锐齿槲栎是不耐阴树种，它的更新策略是通过产生大量种子，当有大的林窗时，幼苗在林窗内生长逐步进入乔木层。 5 神农架地区102-130a成熟米心水青冈林的生物量在251.31-358.63T•hm~(-2)之间，平均为288.70 ± 48.30T•~(-2)，20-60a锐齿槲栎林群落生物量在134.85-301.20T•hm~(-2)，平均为231.60 ± 78.10T•hm~(-2)。虽然米心水青冈林和锐齿槲栎林灌木层草本层及藤本植物组成很丰富，但二种类型森林生物量的95％以上集中在乔木层。乔木层生物量主要集中在少数优势种中。在米心水青冈林生物量从大到小的序列中，前5种植物分别占乔木层总生物量58.67%-96.37%不等，同样锐齿槲栎林前5种植物占群落生物量的68.13%-95.26%。常绿植物占乔木层生物量的比例变化较大，米心水青冈林中占2.85-18.70%，锐齿槲栎林中一般常绿植物占0.8-9.98%，只有1个锐齿槲栎林样地常绿植物（主要是粉白杜鹃）占乔木层生物量的44.04%。米心水青冈林生物量根冠比为0.27 ± 0.05，锐齿槲栎林为0.21 ± 0.06。神农架地区米心水青冈林的生物量，在成熟的欧洲水青冈林及日本的水青冈林生物量范围之内，而锐齿槲栎林生物量远远大于我国温带落叶栎林的生物量。 6 神农架地区102-130a米心水青冈林生产量范围在1857-2786g•m~(-2)•a~(-1)，平均为2330 ± 397 g•m~(-2)•a~(-1)。20-60a锐齿槲栎林的生产量范围在1319-2521 g•m~(-2)•a~(-1)，平均为1930 ± 498 g•m~(-2)•a~(-1)。米心水青冈林和锐齿槲栎林乔木层生产量占群落总生产量的95％以上，乔木层各器官生产量大小顺序为叶> 树干> 枝和根，其中叶生产量占乔木层的一半以上，达53.87 ± 2.72%（米心水青冈林）和57.31 ± 6.23%（锐齿槲栎林）。在乔木层生产量从大到小的序列中，前5种植物平均占乔木层总生产量的81.03 ± 13.94%（米心水青冈林，范围在62.75%-92.66%）和84.23 ± 9.68%（锐齿槲栎林，范围在68.54-95.11%）。米心水青冈林和锐齿槲栎林群落地下部分生产量占总生产量的比例分别为11.29 ± 1.02%和9.22 ± 2.72。和我国其它地区地带性植被类型相比。米心水青冈林和锐齿槲栎生产量是较高的，和亚热带绿阔叶林生产量接近，但在器官分配上两者差异较大。 7 米心水青冈林和锐齿槲栎林土壤均呈酸性。其中锐齿槲栎林地土壤酸性更强。土壤元素特征表现为Al>C>K>Mg>Ca>N>S、P的特点，富铝化作用明显。8种元素在群落优势植物不同部位含量差异较大，N、P、K、Ca、Mg基本上是以叶片含量最高，树干或根中最低。仅从叶片来看，元素特征表现为C>Ca、N>K>Mg>S>P、Al。优势植物的C/N和C/P显著高于暖温带落叶阔叶林优势植物。8种元素在米心水青冈林和锐齿槲栎林中积累量分别为147.09 ± 25.60和116.00 ± 37.63 Mg hm~(-2)a~(-1)，其中97％以上积累在群落乔木层。两种森林类型各元素的积累量都表现为C>Ca, N> K> Mg> P> S> Al的特点。米心水青风林和锐齿槲栎林8种元素的年存留量分别为6263 ± 90.8和5946 ±246 kg hm~(-2)a~(-1),其中N、P、K、Ca、Mg 5种主要营养元素的存留量分别为179.7 ± 18.2和169.4 ± 23.5kg hm~(-2) a~(-1)。两种森林类型各元素的存留量都表现为C> N> Ca> K> Mg> S> P> Al。

神农架锐齿槲栎种群更新及区域生物多样性保护对策

摘要 神农架有着丰富的生物多样性和相对完整的森林生态系统，锐齿槲栎（Quercus aliena var. acuteserrata）是该地区落叶阔叶林重要的建群种之一，是其山地植被垂直带上的一个重要类型，对维持生态系统的稳定和水土保持具有重要意义。本论文主要研究了影响锐齿槲栎种群更新的一些重要因素以及探讨了神农架地区生物多样性的保护对策。 锐齿槲栎种子雨时空分布格局的研究结果表明：不同样地间种子雨的密度差别很大。树木的不同空间方位及种子的不同性状（被昆虫侵害、未发育成熟和有活力）在种子雨密度上的差异都极其显著。但在所研究的距离范围内（2－6m），与母株的距离对种子雨的密度影响不明显。相关性分析显示，样地中的种子雨空间分布与幼苗分布没有直接关系。实验中还发现，被昆虫侵害的种子较早下落，种子雨与落叶时间的不同步性有利于锐齿槲栎幼苗的建成。锐齿槲栎种群的结实存在明显的大小年现象，其结实周期约为2年。 动物对种子的散布与传播是影响锐齿槲栎种群更新的重要因素。在研究小型啮齿目动物对锐齿槲栎种子传播影响的实验中，用样方内布置铁夹的方法共捕获8种小型啮齿目动物，隶属3科、4属。实验结果还证明，不同林型和不同时间段（种子下落高峰期和种子基本落完时期）内小型啮齿目动物的捕食活动规律不同，林下灌木层类型对动物取食橡子和搬运距离也有一定的影响。 光对锐齿槲栎幼苗更新影响的研究结果表明，锐齿槲栎在林窗及林下都有大量的幼苗，而其幼树却很少。坡向对锐齿槲栎种群的更新有重要影响，光照好的东南坡上的更新情况明显比光照较少的西北坡好。光照梯度处理实验证明，光照强度影响锐齿槲栎幼苗的资源分配方式和比例，一定的遮荫环境更有利于锐齿槲栎幼苗的生长。 米心水青冈林（Fagus engleriana）和锐齿槲栎林在神农架地区广泛分布,两者分布的海拔范围比较相近,并形成一定面积的混交林。通过典型样地调查以及对苗木光合作用与资源分配的研究，结果表明：这两个树种具有不同的光利用策略，米心水青冈比较耐荫，林下更新较好，而锐齿槲栎林下更新不良，在光照较好的林窗下及次生裸地上更易更新。 神农架保护区是我国建立较早的以保护森林生态系统为主的自然保护区，是是联合国人与生物圈的保护地区之一，具有重要的生态价值和科研价值。保护区的建立对该地区的生物多样性保护发挥了重要的作用，但仍然面临着种种威胁。通过对神农架自然保护区当地社区的基本情况进行实地调查，分析结果表明，当地社区经济发展与生物多样性保护的矛盾比较突出，人类活动的干扰使景观破碎化呈增加趋势，整个生态系统比较脆弱。针对以上种种问题，建议加快制定有关保护区管理的法律;建立国家生态效益的补偿机制;推动实施社区共管;加强科研与区域生物多样性保护网络的协作;发展特色经济;加强能力建设，促进当地社区社会经济的全面发展。

大巴山两种水青冈林的群落特征分析

水青冈林是欧洲、北美东部和日本温带地区最主要的地带性植被之一。在我国，水青冈林仅分布在亚热带山地。因此，无论其物种组成，还是其群落特征都具有明显的区域特点。然而，有关我国水青冈林群落特征的研究还相对较少。大巴山是我国水青冈林分布最集中的地区之一，保存有较大面积的原始水青冈林。本文通过样方调查和植物群落数量特征统计分析的方法，研究了当地巴山水青冈群落和米心水青冈群落的物种多样性特征和群落结构与动态。主要结果如下： 巴山水青冈群落7个样地中，共记录到维管束植物77科、142属、217种。乔木层以壳斗科、杜鹃花科等科为主;灌木层以蔷薇科、忍冬科以及乔木树种的幼树为主;草本层以苔草属植物及普通鹿蹄草占优势。群落区系地理成分划分为16个类型及亚型。不同多样性指数的大小在不同层次有所不同。阳坡、半阳坡的物种多样性高于阴坡;不同层次的物种多样性与海拔、土壤特征的回归关系不同。群落建群种和乔木层主要树种的重要值与物种多样性主要表现为负相关关系。灌木层物种多样性主要受到环境因素的影响，而乔木层和草本层物种多样性更明显地受到环境因子和群落自身特征的双重影响。 巴山水青冈群落的乔木层成层明显。根据树冠高度分布可以将其划分为两个亚层，第一亚层高度约为19-27m，第二亚层高度约为5-9m。高位芽植物在群落生活型谱中所占比例最高，其次是地下芽植物、地面芽植物、一年生植物和地上芽植物。巴山水青冈的株数－高度、株数－胸径分布曲线均呈现两头高、中间低的格局，中间高度和中间径级的植株数量很少。 米心水青冈群落4个样地中，共记录到维管束植物74科、140属、197种。乔木层以壳斗科、蔷薇科等科为主;灌木层以蔷薇科、忍冬科等占优势;草本层主要由莎草科、菊科和百合科等科组成。群落的区系地理成分一共划分为18个类型及亚型。除物种丰度外，物种多样性各个指数的顺序均为草本层>乔木层>灌木层。乔木、灌木、竹子的多度和盖度（乔木的盖度以胸高面积代替）均与物种多样性密切相关。 根据树冠高度可将米心水青冈群落的乔木层划分为两个亚层，第一亚层高度约为16-22m，第二亚层高度约为5-9m。近半数乔木物种在群落中呈簇生状。生活型谱中，高位芽植物占优势，其次是地下芽植物、地面芽植物、一年生植物，没有地上芽植物。米心水青冈的实生幼苗十分匮乏，幼树以萌生树为主。其株数－高度、株数－胸径分布曲线呈递减趋势，幼龄个体数＞中龄个体数＞老龄个体数。

Specific leaf area and leaf area index in developing stands of Fagus sylvatica L. and Picea abies Karst

European beech (Fagus sylvatica L.) and Norway spruce (Picea abies Karst.) are two of the most ecologically and economically important forest tree species in Europe. These two species co-occur in many locations in Europe, leading to direct competition for canopy space. Foliage characteristics of two naturally regenerated pure stands of beech and spruce with fully closed canopies were contrasted to assess the dynamic relationship between foliage adaptability to shading, stand LAI and tree growth. We found that individual leaf size is far more conservative in spruce than in beech. Individual leaf and needle area was larger at the top than at the bottom of the canopy in both species. Inverse relationship was found for specific leaf area (SLA), highest SLA values were found at lowest light availability under the canopy. There was no difference in leaf area index (LAI) between the two stands, however LAI increased from 10.8 to 14.6 m2m-2 between 2009 and 2011. Dominant trees of both species were more efficient in converting foliage mass or area to produce stem biomass, although this relationship changed with age and was species-specific. Overall, we found larger foliage plasticity in beech than in spruce in relation to light conditions, indicating larger capacity to exploit niche openings.

Vertical variation in autumn leaf phenology of Fagus sylvatica L. in southern Germany

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Differences in Soil Fungal Communities between European Beech (Fagus sylvatica L.) Dominated Forests Are Related to Soil and Understory Vegetation

Fungi are important members of soil microbial communities with a crucial role in biogeochemical processes. Although soil fungi are known to be highly diverse, little is known about factors influencing variations in their diversity and community structure among forests dominated by the same tree species but spread over different regions and under different managements. We analyzed the soil fungal diversity and community composition of managed and unmanaged European beech dominated forests located in three German regions, the Schwäbische Alb in Southwestern, the Hainich-Dün in Central and the Schorfheide Chorin in the Northeastern Germany, using internal transcribed spacer (ITS) rDNA pyrotag sequencing. Multiple sequence quality filtering followed by sequence data normalization revealed 1655 fungal operational taxonomic units. Further analysis based on 722 abundant fungal OTUs revealed the phylum Basidiomycota to be dominant (54%) and its community to comprise 71.4% of ectomycorrhizal taxa. Fungal community structure differed significantly (p≤0.001) among the three regions and was characterized by non-random fungal OTUs co-occurrence. Soil parameters, herbaceous understory vegetation, and litter cover affected fungal community structure. However, within each study region we found no difference in fungal community structure between management types. Our results also showed region specific significant correlation patterns between the dominant ectomycorrhizal fungal genera. This suggests that soil fungal communities are region-specific but nevertheless composed of functionally diverse and complementary taxa.

Tree Species Composition and Harvest Intensity Affect Herbivore Density and Leaf Damage on Beech, Fagus sylvatica, in Different Landscape Contexts

Most forests are exposed to anthropogenic management activities that affect tree species composition and natural ecosystem processes. Changes in ecosystem processes such as herbivory depend on management intensity, and on regional environmental conditions and species pools. Whereas influences of specific forest management measures have already been addressed for different herbivore taxa on a local scale, studies considering effects of different aspects of forest management across different regions are rare. We assessed the influence of tree species composition and intensity of harvesting activities on arthropod herbivores and herbivore-related damage to beech trees, Fagus sylvatica, in 48 forest plots in three regions of Germany. We found that herbivore abundance and damage to beech trees differed between regions and that – despite the regional differences - density of tree-associated arthropod taxa and herbivore damage were consistently affected by tree species composition and harvest intensity. Specifically, overall herbivore damage to beech trees increased with increasing dominance of beech trees – suggesting the action of associational resistance processes – and decreased with harvest intensity. The density of leaf chewers and mines was positively related to leaf damage, and several arthropod groups responded to beech dominance and harvest intensity. The distribution of damage patterns was consistent with a vertical shift of herbivores to higher crown layers during the season and with higher beech dominance. By linking quantitative data on arthropod herbivore abundance and herbivory with tree species composition and harvesting activity in a wide variety of beech forests, our study helps to better understand the influence of forest management on interactions between a naturally dominant deciduous forest tree and arthropod herbivores.

Migration and population expansion of Abies, Fagus, Picea, and Quercus since 15000 years in and across the Alps, based on pollen-percentage threshold values

Aims: The aim of this study is to explore the migration (colonization of new areas) and subsequent population expansion (within an area) since 15 ka cal BP of Abies, Fagus, Picea, and Quercus into and through the Alps solely on the basis of high-quality pollen data. Methods: Chronologies of 101 pollen sequences are improved or created. Data from the area delimited by 45.5–48.1°N and 6–14°E are summarized in three ways: (1) in a selection of pollen-percentage threshold maps (thresholds 0.5%, 1%, 2%, 4%, 8%, 16%, and 32% of land pollen); (2) in graphic summaries of 250-year time slices and geographic segments (lengthwise and transverse in relation to the main axis of the Alps) as pollen-percentage curves, pollen-percentage difference curves, and pollen-percentage threshold ages cal BP graphed against both the length and the transverse Alpine axes; and (3) in tables showing statistical relationships of either pollen-percentage threshold ages cal BP or pollen expansion durations (=time lapse between different pollen-percentage threshold ages cal BP) with latitude, longitude, and elevation; to establish these relationships we used both simple linear regression and multiple linear regression after stepwise-forward selection. Results: The statistical results indicate that (a) the use of pollen-percentage thresholds between 0.5% and 8% yield mostly similar directions of tree migration, so the method is fairly robust, (b) Abies migrated northward, Fagus southward, Picea westward, and Quercus northward; more detail does not emerge due to an extreme scarcity of high-quality data especially along the southern foothills of the Alps and in the eastern Alps. This scarcity allows the reconstruction of one immigration route only of Abies into the southern Alps. The speed of population expansion (following arrival) of Abies increased and of Picea decreased during the Holocene, of Fagus it decreased especially during the later Holocene, and of Quercus it increased especially at the start of the Holocene.

What drives European beech (Fagus sylvatica L.) mortality after forest fires of varying severity?

Predicting the timing and amount of tree mortality after a forest fire is of paramount importance for post-fire management decisions, such as salvage logging or reforestation. Such knowledge is particularly needed in mountainous regions where forest stands often serve as protection against natural hazards (e.g., snow avalanches, rockfalls, landslides). In this paper, we focus on the drivers and timing of mortality in fire-injured beech trees (Fagus sylvatica L.) in mountain regions. We studied beech forests in the southwestern European Alps, which burned between 1970 and 2012. The results show that beech trees, which lack fire-resistance traits, experience increased mortality within the first two decades post-fire with a timing and amount strongly related to the burn severity. Beech mortality is fast and ubiquitous in high severity sites, whereas small- (DBH <12 cm) and intermediate-diameter (DBH 12–36 cm) trees face a higher risk to die in moderate-severity sites. Large-diameter trees mostly survive, representing a crucial ecological legacy for beech regeneration. Mortality remains low and at a level similar to unburnt beech forests for low burn severity sites. Beech trees diameter, the presence of fungal infestation and elevation are the most significant drivers of mortality. The risk of beech to die increases toward higher elevation and is higher for small-diameter than for large-diameter trees. In case of secondary fungi infestation beech faces generally a higher risk to die. Interestingly, fungi that initiate post-fire tree mortality differ from fungi occurring after mechanical injury. From a management point of view, the insights about the controls of post-fire mortality provided by this study should help in planning post-fire silvicultural measures in montane beech forests.