川西高山林线交错带凋落物纤维素分解酶活性研究

以川西高山林线交错带3种典型植被类型(针叶林、高山灌丛、高山草甸)下两个层次(LF层: 新鲜凋落物层和发酵层; H层: 腐殖质层)的凋落物为研究对象, 分别模拟凋落物分解的前期和后期阶段, 对凋落物分解过程中的纤维素酶活性及凋落物质量进行了研究。结果表明, 凋落物分解前期的纤维素酶活性和纤维素含量均显著高于分解后期, 但植被类型对LF和H层的纤维素含量的影响都不显著。双因素方差分析结果表明, 凋落物分解阶段对纤维素酶活性和纤维素含量的影响比植被类型对纤维素酶活性和纤维素含量的影响更大。不同种类的纤维素酶活性在分解前期和分解后期受到不同因子的限制。凋落物分解前期, 微晶纤维素酶和β-葡萄糖苷酶活性可能受N、P含量的限制, 而羧甲基纤维素酶主要受底物纤维素含量控制; 凋落物分解后期, 羧甲基纤维素酶和β-葡萄糖苷酶可能受C、N含量的限制。生态化学计量学的理论预测, 底物质量比C:N > 27或C:P > 186时会限制微生物生长, 因此判断高山林线交错带凋落物微生物生物量和纤维素酶活性同时受到底物N、P的限制, 尤其是高山草甸上微生物生物量在凋落物分解前期受到底物N、P的限制比分解后期更显著, 这充分说明了底物质量调控着凋落物分解过程中的纤维素酶活性和微生物生物量。     

高山林线交错带高山杜鹃的凋落物分解

凋落物分解是维持生态系统生产力、养分循环、土壤有机质形成的关键生态过程。高山林线交错带是陆地生态系统中对气候变化响应的敏感区域。季节变化和海拔梯度上的植被类型差异可能会影响该区域凋落物的分解,进而对高山生态系统的碳氮循环产生重要影响。采用凋落物分解袋的方法,研究了川西高山林线交错带优势种高山杜鹃(Rhododendron lapponicum)凋落叶在雪被期和生长季的分解特征。结果显示:(1)季节变化和植被类型对高山杜鹃凋落物的分解均具有显著影响(P0.05),凋落叶的质量损失主要发生在生长季且在高山林线最大,暗针叶林中雪被期的质量损失略高于生长季,但差异不显著;(2)林线交错带上高山杜鹃凋落叶分解缓慢,一年干物质失重率为9.62%,拟合分解系数k为0.145;(3)高山杜鹃凋落叶的质量变化主要体现在纤维素降解显著且集中在雪被期,木质素无明显降解,在高山林线上C/N、C/P、木质素/N变化幅度较小且C、N、P的释放表现得稳定而持续。结果表明,季节性雪被对林线交错带内高山杜鹃分解的影响不仅局限在雪被期内,雪被融化期间频繁的冻融作用和雪融水淋洗作用可能会促进高山杜鹃凋落物在生长季初期的分解。总的来看,在气候变暖的情景下,雪被的缩减、生长季的延长和高山杜鹃群落的扩张可能加速高山林线交错带高山杜鹃凋落物的分解。     

How the timberline formed: altitudinal changes in stand structure and dynamics around the timberline in central Japan

Background and Aims

Altitudinal timberlines are thought to move upward by global warming, a crucial topic in ecology. Tall tree species (the conifer Abies mariesii and the deciduous broad-leaved Betula ermanii) dominate the sub-alpine zone between 1600 and 2500 m a.s.l., the timberline, on Mount Norikura in central Japan. Dwarf pine Pinus pumila dominates above the timberline to near the summit (3026 m a.s.l.). This study evaluated how the timberline formed on Mount Norikura by examining altitudinal changes in stand structure and dynamics around the timberline.

Methods

One hundred and twenty-five plots of 10 m × 10 m were established around the timberline (2350–2600 m a.s.l.). Trunk diameter growth rate during 6 years was examined for A. mariesii, B. ermanii and P. pumila. Mortality during this period and mechanical damage scars on the trunks and branches due to strong wind and snow were examined for A. mariesii only.

Key Results

The density, maximum trunk height and diameter of A. mariesii in plots decreased with altitude. The maximum trunk height of B. ermanii decreased with altitude, but density and maximum trunk diameter did not decrease. In contrast, the density of P. pumila abruptly increased from around the timberline. A strong negative correlation was found between the densities of P. pumila and tall tree species, indicating their interspecific competition. Trunk diameter growth rates of A. mariesii and B. ermanii did not decrease with altitude, suggesting that these two tall tree species can grow at the timberline. The ratio of trees with mechanical damage scars increased with altitude for A. mariesii, a tendency more conspicuous for larger trees. The mortality of larger A. mariesii was also greater at higher altitude. Tall tree species may not increase their trunk height and survive around the timberline because of mechanical damage.

Conclusions

This study suggests that the altitudinal location of the timberline is mainly affected by mechanical damage due to strong wind and snow rather than by growth limitation due to low temperature. Therefore, the timberline would not move upward even under global warming if these growth and mortality characteristics do not change for a long time.     

川西高山林线交错带凋落叶分解初期转化酶特征

胞外酶对于有机质的降解具有重要的作用。在凋落物分解过程中,酶活性不仅受到凋落物种类或基质质量的影响,还受到环境因素的影响。转化酶催化蔗糖水解为葡萄糖和果糖,因此在凋落物分解早期,转化酶比降解难分解物质的酶具有更重要的作用。以川西高山林线交错带12种代表性凋落叶为研究对象,对林线交错带不同植被类型下的凋落叶转化酶活性以及物种和环境因子对转化酶活性的影响进行了研究。结果表明:同一植被类型下,12个物种转化酶活性具有极显著差异(P0.01)。物种、环境因子及其交互作用对转化酶活性有极显著的影响(P0.01)。初始纤维素含量与转化酶活性极显著正相关(P0.01)。初始木质素和总酚含量与转化酶活性极显著负相关(P0.01),能够共同解释转化酶活性变异的50.8%。不同植物生活型中,禾草类转化酶活性均为最高,这可能与禾草类较高的初始纤维素含量、较低的木质素和总酚含量有关。多元线性回归分析表明,凋落叶含水量能单独解释转化酶活性变量的62.1%,是环境因子中最重要的变量。从植被类型来看,大多数物种的转化酶活性在针叶林中均极显著高于高山草甸和灌丛(P0.01),这可能与针叶林中凋落叶的含水量最高且雪被最厚有关。历经一个雪被期分解后,凋落叶初始质量与环境因子的综合作用能够解释转化酶活性变异的79.1%,表明川西高山林线交错带凋落叶分解前期转化酶活性主要受初始木质素含量、总酚含量和含水量的调控。在全球气候变化情景下,凋落物水分含量的变化将会强烈的影响凋落叶分解前期的转化酶活性。     

川西高山林线交错带凋落叶分解速率与初始质量的关系

对我国川西高山林线交错带14种代表性植物凋落叶分解速率与初始质量的关系进行研究.结果表明: 高山林线交错带植物凋落叶分解速率（k）为0.16～1.70,乔木和苔藓凋落叶分解较慢,灌木凋落叶次之,草本凋落叶分解最快.凋落叶分解速率与N、木质素、酚类物质、C/N、C/P、木质素/N均具有显著的线性回归关系.通径分析得出,木质素/N和半纤维素含量可以解释k变异的78.4%,其中木质素/N可以解释k变异的69.5%,木质素/N对k的直接通径系数为-0.913.主成分分析表明,第1排序轴k、分解时间（t）的贡献率达99.2%,木质素/N、木质素含量、C/N、C/P与第1排序轴呈显著正相关,其中木质素/N与第1排序轴的相关关系最强(r=0.923).木质素/N是影响川西高山林线交错带植物凋落叶分解速率的关键质量指标,且凋落叶初始木质素/N越高,分解速率越低.     

神农架国家公园林线过渡带土壤真菌多样性

林线过渡带是陆地生态系统对气候变化响应的敏感区域,研究林线过渡带土壤真菌的群落结构和形成机制,对于预测气候变化对土壤养分循环和维持陆地生态系统功能的影响具有重要意义。利用Illumina高通量测序技术分析了神农架国家公园林线上下的灌木林和针叶林的土壤真菌群落结构和多样性。结果表明,在真菌物种组成上,两种植被类型的土壤优势菌门、属和种类不同,针叶林和灌木林的优势菌门分别是担子菌门(Basidiomycota)和接合菌门(Zygomycota)。除趋势对应分析(DCA)和不相似性检验(Dissimilarity test)表明两种林型的土壤真菌群落结构组成存在显著差异,且针叶林土壤真菌Shannon指数、Chao值和Richness指数均显著(P0.05)高于灌木林。典范对应分析(CCA)和Mantel检验显示土壤真菌群落结构与土壤p H、植物多样性、土壤温度和土壤湿度存在显著相关性。因此,林线过渡带上下的土壤真菌群落结构和多样性存在显著差异,土壤p H、植物多样性、土壤湿度和土壤温度可能是影响土壤真菌群落结构的重要因素。     

Differential survival among life stages contributes to co‐dominance of Abies mariesii and Abies veitchii in a sub‐alpine old‐growth forest

Questions: Are there interspecific differences in mortality and recruitment rates across life stages between two shade‐tolerant dominant trees in a sub‐alpine old‐growth forest? Do such differences in demography contribute to the coexistence and co‐dominance of the two species? Location: Sub‐alpine, old‐growth forest on Mt. Ontake, central Honshu, Japan. Methods: From 1980 to 2005, we recorded DBH and status (alive or dead) of all Abies mariesii and A. veitchii individuals (DBH ≥ 5 cm) in a 0.44‐ha plot. Based on this 25 year census, we quantified mortality and recruitment rates of the two species in three life stages (small tree, 5 cm ≤ DBH < 10 cm; subcanopy tree, 10 cm ≤ DBH < 20 cm; canopy tree, DBH ≥ 20 cm). Results: Significant interspecific differences in mortality and recruitment rates were observed in both the small tree and sub‐canopy tree stages. In this forest, saplings (< 5 cm DBH) are mostly buried by snow‐pack during winter. As a consequence, saplings of A. mariesii, which is snow and shade tolerant, show higher rates of recruitment into the small tree stage than do those of A. veitchii. Above the snow‐pack, trees must tolerate dry, cold temperatures. A. veitchii, which can more readily endure such climate conditions, showed lower mortality rate at the subcanopy stage and a higher recruitment rate into the canopy tree stage. This differential mortality and recruitment among life‐stages determines relative dominance of the two species in the canopy. Conclusion: Differential growth conditions along a vertical gradient in this old forest determine survival of the two species prior to reaching the canopy, and consequently allow co‐dominance at the canopy stage.     

长白山林线交错带形状与木本植物向苔原侵展和林线动态的关系

采用样带调查法测定了长白山岳桦林缘形状对入侵苔原木本植物和分布,树木生长和死亡的影响,阐述了林缘形状形成与生境小气候的关系,探讨了不同形状林缘更新格局形成的原因和林线的动态,林缘入侵物种主要由岳桦和东北赤杨组成。凹型林缘外入侵权地木向苔原侵展的距离和茎数,以及平均基径,基面积主平均高度均明显高一直线型和凸型林缘,其中凸型林缘的值最低,且锭离林缘降低最为迅速,随远离林缘入侵植株枯梢率增高分枝数增殖,     

Holocene dynamics of the alpine timberline in the High Sudetes

The study focuses on the High Sudetes that represent the most distinctive islands of alpine forest-free area among hercynian mid-mountains of Central Europe. Based on data from newly taken cores and previously published pollen profiles, comparison of the development of the alpine timberline position is carried out. The first of the analysed pollen profiles — the Labsky důl core in the Krkonoše Mts spans the whole period of the Holocene, the Keprník and Mezikotlí profiles in the Hruby Jeseník Mts bring information from the Subboreal/older Subatlanticum turn to the present. An exceptional position of the Krkonoše Mts in terms of permanent presence of the alpine belt throughout the Holocene was confirmed. Three oscillations of the alpine timberline during the Lower Holocene were detected in the profile from the Labsky důl site. In the Hruby Jeseník Mts a temperature dependent forest-free area existed at least since Subboreal to the present.     

川西亚高山林线过渡带及邻近植被土壤性质

研究了川西亚高山林线过渡带及邻近植被上缘流石滩草甸与下缘冷杉林残积母质土壤物理、化学和生物学特性.结果表明:从流石滩草甸→林线过渡带→冷杉林,土层逐渐增厚,表层土壤(0～30 cm)粉粒、粘粒、物理性粘粒含量、团聚度、结构系数和自然含水量逐渐增高,砂粒含量逐渐降低,阳离子交换量(CEC)、交换性盐基含量、盐基饱和度以及水解性酸含量逐渐增高,pH值逐渐降低,有机质及养分库全P、全K、有效N、有效P和速效K含量逐渐增高,土壤物理结构和化学性质逐步有所改善,但亚高山林线过渡带区域残积母质土壤成土过程缓慢.林线过渡带表层土壤细菌、真菌、放线菌及微生物总量,土壤脲酶、蔗糖酶、酸性磷酸酶、中性磷酸酶、多酚氧化酶及过氧化氢酶活性高于邻近植被上缘流石滩草甸与下缘冷杉林,体现了作为生态交错带,林线过渡带比邻近植被土壤具有相对较强的生物学活性.     

雪被期川西高山林线交错带两种地被物凋落物分解与土壤动物多样性

以针叶林代表性地被植物锦丝藓和高山冷蕨为研究对象,采用凋落物分解网袋法,研究了高山林线交错带(暗针叶林-林线-高山草甸)的锦丝藓植物残体、高山冷蕨凋落叶及混合凋落物经过一个雪被期分解后的质量损失与土壤动物群落结构特征.结果表明: 雪被期林线交错带上两种地被物的质量损失率在高山草甸最大,锦丝藓表现更为显著,两种凋落物混合促进了分解过程且在林线上表现尤为显著.在交错带凋落物中共获取土壤动物968头,隶属于5纲10目35科,优势类群以弹尾目和蜱螨目为主.在林线上凋落物中获得的土壤动物个体数和类群数高于高山草甸和暗针叶林.典范对应分析(CCA)表明,土壤动物类群与雪被期平均温度关系最为密切,特有物种如等翅目和地蜈蚣目仅在暗针叶林出现,半翅目和啮目仅在高山草甸出现.地被物种类对土壤动物多样性的影响在暗针叶林和高山草甸大于林线.多元回归分析表明,日平均温度和雪被厚度能够解释凋落物质量损失率变异的30.8%,而土壤动物因子能解释质量损失率变异的8.3%,它们共同解释质量损失率变异的34.1%.雪被是影响高山两种地被物凋落物分解的最关键因子.     

Regeneration and coexistence of two Abies species dominating subalpine forests in central Japan

Summary The mechanism of coexistence of the dominant firs Abies veitchii and A. mariesii is described in relation to regeneration patterns for climax subalpine forests of the northern Yatsugatake Mountains, central Honshu, Japan. Two mature stand types, pure conifer stands of Abies spp., and mixed stands of Abies spp. and hardwoods (mainly the birch Betula ermanii), are distinguished. Pure stands are likely to show simultaneous decay, followed by evenaged regeneration of stand-floor seedlings (<20 cm tall), Rapidly growing A. veitchii dominates over A. mariesii in this type of regeneration, which is occasionally invaded by light-demanding Betula. In constrast, mixed stands degenerate rather slowly, followed by the regeneration of Abies from the bank of suppressed saplings (>20 cm tall), which persist only in mixed stands. The more shade-tolerant A. mariesii is supeior in this type of regeneration, while Betula does not succeed, and mixed stands change to pure stands with time. The fact that two patterns of Abies regeneration occur in a certain ratio in the forest is what enables the two Abies species to coexist. A simple dynamical system model supports this conclusion.     

高山林线与气候变化关系研究进展

20世纪全球气候经历了异常的变化。20世纪是过去1000年中增暖最大的1个世纪,并且90年代是最暖的10年。作为两个生态系统的过渡地带,生态过渡带是监测全球变化的重要地点,而森林和苔原之间的高山林线是全球变化最为敏感的地点。从高山林线树木个体对气候变化的响应、气候变化下林线处树木的更新、林线格局变化以及高山林线与气候变化关系研究中所采用的研究方法等方面,综合论述了国内外的研究进展,最后提出了高山林线研究中需要注意的问题,并对今后的研究趋势作了展望。     

Effects of wind and thermal conditions on timberline formation in central Japan: a lattice model

The upper distribution limit of tall tree species Abies mariesii is the timberline in central Japan, and dwarf pine Pinus pumila dominates above the timberline to near the summit. My previous studies suggested that the main cause of the timberline formation is the increase in mortality due to strong wind in winter rather than low growth due to low summer temperature. This study evaluated how wind velocity affects timberline formation and if the altitude of timberline moves upward due to high thermal conditions, by using a lattice model. Increase in wind velocity throughout the altitude lowered the altitudes of upper distribution limits of the two species. On the contrary, prolonged growth period due to high thermal conditions increased the upper distribution limit of P. pumila, and the upper distribution limit of A. mariesii was hardly affected by the change of growth period. However, the upward shift of the upper distribution limit of P. pumila due to the prolonged growth period in the model would not be realistic because P. pumila had already distributed up to near the summit. This study concludes that A. mariesii is a superior competitor to P. pumila at low altitudes with low wind velocity, but dwarf pine P. pumila can dominate at higher altitudes because A. mariesii suffers severe mechanical damage due to strong wind in winter, and that the altitude of the timberline does not move upward even under high thermal conditions due to global warming.     

Development of acute frost drought in Rhododendron ferrugineum at the alpine timberline

Summary Acute winter frost drought in Rhododendron ferrugineum at the alpine timberline was provoked by removing the snow that had covered the shrubs and by irradiating and rewarming the twigs in situ in a climatized chamber simulating snow melt conditions. Water potential decreased to -2.3 MPa within three days. After activation of photosynthesis on the 1st day, the COr-uptake decreased during the 2nd day and approached zero at the 3rd day. With advanced desiccation, the internal COr concentration of the leaves increased indicating an impairment of chloroplast functions. The procedure of the disturbances appears to be similar to that of other acute drought events.     

Vegetative phenology of alpine plants at Tateyama Murodo-daira in central Japan

The vegetative phenology of 29 alpine species, including herbaceous and woody summergreens and evergreens, was investigated. Summergreen species initiated and completed leaf growth earlier than evergreen species. The green period of leaves in summergreen plants was determined largely by the time of growth initiation. Early initiation of growth in summergreen plants contributes to the increase in photosynthetic carbon gain. Early cessation of growth in summergreens is advantageous for the growth in the following year because it leads to an increase in stored photosynthates. The growth period of leaves and stems in alpine plants correlated with the time of growth initiation more strongly than with the time of growth cessation, indicating the importance of early growth initiation for the increase in plant growth. The growth period of leaves was positively correlated with the sum of leaf lengths and the number of leaves. Herbs with a long growth period of more than 50 days had perennial shoot axes not terminated by inflorescences, suggesting a relationship between the growth period and shoot habit. Two summergreen species were completely dead by mid-September, before the air temperature decreased below 0°C. The remaining summergreen species died immediately after the air temperature decreased to −1.4°C in late September.     

高山林线形成机理及植物相关生理生态学特性研究进展

高山林线作为极端环境条件下树木生存的界限,由于其对气候变化的敏感性,在全球变化研究中得到了广泛关注。研究高山林线形成机理以及林线地带植物相关生理生态学特性成为预测未来气候变化条件下植被动态变化的出发点。对于高山林线形成机理研究主要关注两方面问题：（1）林线地带外界环境如何限制乔木生长和分布,其内在机理如何;（2）灌木及草本相对于乔木在林线地区有哪些生存优势,从乔木到灌木及草本生活型演变的功能及意义如何。综述了当前高山林线形成机理及相关生理生态特性的国内外最新研究成果,指出尽管温度（尤其是生长季低温）在全球尺度上能解释大部分高山区域林线的分布,但树木生长和生存受限的内在机理并没有弄清楚,目前主要存在“碳受限”以及“生长受限”假说两大争论焦点。另外,理论上受温度控制的高山林线对气候变化的响应表现出不同的模式,表明全球变化对林线分布和植被生长影响的复杂性和不确定性。因此,未来的研究应该关注影响林线地区植被生长的多种生理生态学过程,比如水分及养分利用过程,以及从乔木到灌木及草本生活型演变的功能意义,从而为林线形成机理以及对气候变化的响应提供更好的解释。     

Difference in microhabitat-related regeneration patterns between two subalpine conifers, Tsuga diversifolia and Abies mariesii, on Mount Hayachine, northern Honshu, Japan

Seedling and tree-establishment microhabitats of Tsuga diversifolia and Abies mariesii were examined on the herb- and dwarf bamboo-dominated forest floor on Mount Hayachine, a mountain under intermediate snow conditions in northern Honshu, Japan. The four microsite types were fallen logs, buttresses, rocks and ground. The ground substratum was further divided into four subtypes by dominant undergrowth species: Lycopodium, Pteridophyllum, Carex and dwarf bamboo. The establishment of T. diversifolia seedlings on the ground was scarce, and depended mostly on non-ground microsites (i.e. fallen logs, buttresses and rocks). The seedling establishment of A. mariesii was not dependent on specific substrata, although on the ground, establishment sites were limited to the Lycopodium subtype situated on convex sites. Among the microhabitats for seedling establishment, larger trees of A. mariesii rarely occurred on higher portions of the non-ground microsites. In contrast, T. diversifolia could grow up to the height of canopy-layer trees in such microsites. Thus, non-ground microsites seem to be unsuitable for tree establishment in A. mariesii, and are probably useful microhabitats for regenerating T. diversifolia to avoid competition with A. mariesii. We also compared seedling-establishment microhabitats for the two conifers between Mount Hayachine and two other mountain regions under different undergrowth conditions (moss-dominated and dense dwarf bamboo-dominated). Our findings suggested that seedling recruitment in non-ground microsites was primarily determined by undergrowth conditions; T. diversifolia preferred such microsites where the moss-covered area was low, and A. mariesii preferred where dwarf bamboo-covered area was high.