大兴安岭北部地区原始林火干扰历史的研究

在大兴安岭阿龙山林业局的一个集水区,通过样地法（９６个样地）,调查了大量的火疤木,研究了景观水平上的火状况。结果表明,由１８２５至１９９３年间样区共发生１４次火灾,火烧种类主要是地表火,但也有少量树冠火;火烧强度主要为弱度火;火场面积通常很大;火烧平均间隔期为３７ａ,火烧轮回期的约３０ａ。这些指标对大于大兴安岭北部林区有一定的代表意义。大兴安岭北部林区的火状况主要决定于兴安落叶松的抗火特性和森林群     

中度火干扰对兴安落叶松林土壤呼吸的影响

通过测定中度火干扰后塔河地区兴安落叶松(Larix gmelinii)林生长季土壤呼吸(R_s),并进一步探究火干扰后影响土壤呼吸变化的主要环境因子。选择在塔河林业局火烧4年后兴安落叶松林中度火烧迹地设置样地,选择临近未过火区域设置对照样地。土壤呼吸通量用LI-8100进行测量,土壤异养呼吸(R_h)采用壕沟法进行测量。火烧迹地与未火烧对照样地生长季土壤呼吸速率平均值分别为(3.67±1.03)μmol CO_2m~(-2)s~(-1),(4.21±1.25)μmol CO_2m~(-2)s~(-1)。火烧迹地土壤呼吸速率显著降低(P0.05)。生长季土壤呼吸组分的动态变化表明,土壤呼吸速率的降低是因为土壤自养呼吸(R_a)显著降低导致的(P0.05)。温度是控制这一地区生长季土壤呼吸变化的主要环境因子。与对照样地相比,火烧迹地土壤呼吸的变化与土壤温度具有更强的相关性。塔河地区兴安落叶松林火烧迹地和未火烧对照样地Q_(10)分别为5.85±1.06,4.25±1.19,火干扰后Q_(10)显著增加(P0.05)。研究结果表明:在全球气候变化的背景下火干扰后中国塔河地区兴安落叶松林生态系统对温度的变化更为敏感。本研究结果将为研究中国塔河地区火干扰后碳循环变化提供数据支持。     

剪叶损伤与昆虫取食对兴安落叶松(Larix gmelinii)针叶中缩合单宁诱导作用的差异

单宁是植物内与抗虫性相关的重要次生代谢物质.为了研究昆虫取食及剪叶诱导对兴安落叶松(Larix gmelinii)针叶内缩合单宁含量的影响,用剪叶法和落叶松毛虫(Dendrolimus superans)幼虫取食处理5年生兴安落叶松苗,以香草醛-盐酸法测定其剩余健康针叶内缩合单宁含量的变化.结果表明:(1)处理后1～10d,剪叶4枝75%,8枝50%、75%,12枝25%、50%、75%及虫伤4枝75%的兴安落叶松健康针叶内的缩合单宁含量均明显高于对照(P<0.01),15d时,剪叶8枝75%,12枝50%的兴安落叶松针叶内的缩合单宁含量仍高于对照(P<0.05),说明剪叶与虫伤处理均能诱导缩合单宁含量增加.(2)剪叶4枝75%,8枝50%,12枝25%、75%的处理之间,诱导的缩合单宁含量差异不显著(P>0.05).剪叶8枝75%,12枝50%诱导缩合单宁含量增加幅度比其它剪叶处理大,且诱导持续时间长.说明剪叶程度虽能影响缩合单宁含量,但二者并不呈线性关系.(3)剪叶4枝75%在5d时诱导缩合单宁含量最高,虫伤4枝75%在10d时诱导缩合单宁含量最高,说明剪叶诱导的缩合单宁含量高峰早于虫伤处理.但处理后1～10d,剪叶及虫伤4枝75%的落叶松针叶内缩合单宁含量均明显高于对照(P<0.01或P<0.05),之后与对照差异不显著(P>0.05),说明在受到诱导处理后,兴安落叶松产生应激反应,使其针叶内缩合单宁含量在一定时间内先增加,后逐渐恢复到正常水平.由上可见,可以采取适当的损伤处理取得与昆虫取食相似的兴安落叶松抗性反应.     

基于CENTURY模型模拟火烧对大兴安岭兴安落叶松林碳动态的影响

火作为森林生态系统重要的自然干扰因子之一,对森林的碳动态有着不可忽视的影响.本研究使用CENTURY模型模拟了大兴安岭呼中林区兴安落叶松林的碳收支对不同强度火烧的响应.结果表明:在不同强度火烧后,土壤总碳库呈先升后降再逐渐恢复的变化趋势,而林分生物碳库则先降后升,其中,林分细小组分碳库的恢复速度明显快于大组分,各碳库的波动程度随火烧强度的增大而增大.森林植被的净初级生产力(NPP)和土壤异养呼吸在火后均先降后升,但NPP的恢复快于土壤异养呼吸,二者的动态变化改变了林分的碳源/汇作用.轻微火烧后,兴安落叶松林仍表现为弱碳汇,并很快恢复到火前水平;其他强度的火烧使兴安落叶松林在短期内(9～12年)表现为碳源,随后逐渐转为碳汇.较低强度的林火不仅可以促进落叶松林的更新、减少死可燃物,也不会对林分的碳汇功能造成太大影响;高强度的严重林火对土壤和林木碳库造成严重损失,延缓森林的恢复,并可使林分表现为较长时间的碳源.     

兴安落叶松林火烧迹地土壤有效磷与土壤微生物生物量磷时空演变特征

野火是大兴安岭活跃的生态干扰因子，显著影响火烧迹地土壤有效磷(AP, Available Phosphorus)和土壤微生物生物量磷(MBP, Microbial Biomass Phosphorus),本文旨在了解兴安落叶松林火烧迹地AP、MBP的时空演变特征，并在此基础上探究两者间的偶联机制。采用“以空间换时间”的研究方法，于大兴安岭塔河地区兴安落叶松林火烧迹地选取实验样地，于未过火兴安落叶松林选取对照样地，踏查每个样地的海拔、坡度、坡向、坡位信息，测定火烧迹地土壤AP、MBP含量，分析兴安落叶松林火烧迹地AP与MBP的时空演变特征。火干扰后，火烧迹地土壤AP、MBP含量均随恢复时间表现出先减少后增加的趋势，恢复初期火烧迹地MBP含量显著低于未过火样地，AP含量显著高于未过火样地(P<0.05);不同海拔火烧迹地AP、MBP含量差异显著(P<0.05),不同海拔未过火样地AP、MBP含量均无显著差异(P>0.05)。火烧迹地土壤MBP、AP的随机森林回归模型的模型总解释度约为84%,而未过火样地的模型总解释度约为60%,两个模型均达到了极显著水平(P<0.0...     

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。     

兴安落叶松种群的稳定性与火干扰关系的研究

从种群生态学和干扰生态学的角度出发,采用火史重建的方法,研究了大兴安岭北部兴安落叶松种群的稳定性与火干扰的关系。结果表明：研究区内历史上火干扰频繁,平均间隔期为２８．９年,火烧强度较低。兴安落叶松依靠较强的耐火力、火力恢复力及自我恢复力具一定的稳定性。种群耐火力与长期火状况密切相关,表现为：低频类〈中频类〈高频类,高强类〈中强类〈低强类。火后恢复力与自我恢复力和最近一次火烧强度及距今时间密切相关：     

叶损伤诱导兴安落叶松针叶中10种酚酸的变化

酚酸是一类重要次生抗虫物质.为研究损伤及昆虫取食诱导对兴安落叶松针叶内酚酸含量的影响,采用3种不同程度剪叶或落叶松毛虫幼虫取食处理兴安落叶松幼树,以高效液相色谱技术测定兴安落叶松健康针叶中酚酸含量.结果表明：与对照相比,处理后1 d,剪叶或昆虫取食4枝50%针叶处理的兴安落叶松幼苗健康针叶中,除阿魏酸无显著差异外,苯甲酸、咖啡酸、绿原酸、水杨酸、苯乙酸、肉桂酸、香草酸、丁香酸和没食子酸9种酚酸均差异显著;4枝75%针叶处理的10种酚酸含量均发生显著变化.说明剪叶及虫害50%、75%针叶处理均达到诱导阈值,能显著诱导兴安落叶松化学防御.在损伤程度相同情况下,处理1 d时,剪叶4枝50%、75%诱导的咖啡酸、苯乙酸、肉桂酸、香草酸和没食子酸的含量显著高于虫害诱导处理;5 d时,剪叶4枝50%、75%诱导处理的这5种酚酸含量显著低于虫害诱导处理;10 d时,两种方法诱导的酚酸含量差异不显著.说明剪叶诱导处理的酚酸含量变化比昆虫取食处理迅速,且诱导强度与剪叶程度相关.采用适当处理诱导针叶中酚酸含量的变化来增强兴安落叶松对害虫的防御能力是可行的.     

兴安落叶松的结实及其与短枝年龄结构的关系

继1989年以后,1991年大兴安岭林区兴安落叶松又出现一次结实,结实率平均为63.8％,且结实的林木多出现在过火的林地上。胸径28cm以上的林木结实率可达到80％以上,而且结实量多的林木绝大部分(85％以上)是树冠稀疏的。球果多集中于树冠的中部。短枝年龄结构格局对结实具有重要影响。短枝的数量以1、2年生最多,但结实的短枝主要属于3—7年生的短枝,一次种子丰收年,需要消耗大量的短枝数量,花芽中大部分为雄花,直接用于形成球果的雌花,一般尚不足20％。开花结实成熟年龄短枝的存蓄率愈高,其结实的潜力也愈大,出现种子年的可能性也愈大。     

增温和光周期变化对东北地区兴安落叶松主要物候期的影响

兴安落叶松在东北地区森林生态系统的结构与功能中起着重要作用,气候变化背景下东北地区气温增加且光照缩短必将影响兴安落叶松的变化,特别是物候这一气候变化的敏感指标。弄清其物候对气候变化的响应有助于揭示兴安落叶松的变化趋势。但是,当前关于兴安落叶松物候对温度、光周期及其协同作用的响应机制仍不清楚。针对东北地区温度剧增、日照时数减少的特点,2019年4月至11月开展了3年生兴安落叶松幼苗主要物候期响应温度和光周期变化的大型人工气候室模拟控制实验。结果表明：(1)不同程度的增温对兴安落叶松生长周期(展叶始期至完全变色期)无显著影响,但显著缩短生长盛期(展叶盛期至叶变色普期),且增温2.0℃较增温1.5℃对生长盛期影响更大。(2)长光照显著增加兴安落叶松的生长周期(9.25 d),短光照对兴安落叶松生长周期的影响不显著,且长光照和短光照均使兴安落叶松生长盛期缩短,二者对兴安落叶松生长盛期影响表现一致。(3)长光照、短光照分别与增温协同作用均使兴安落叶松生长盛期缩短,其中增温2.0℃与长光照协同作用对生长盛期缩短更显著(34.67 d)。(4)与生长始期(展叶始期)和末期(完全变色期)相比,兴安落叶...     

The effect of crown position and date of sampling on biomass,nutrient concentrations and contents of needles and shoots in European larch

 The nutrient concentrations and contents of needles and shoots of 22-year-old European larch (Larix decidua Mill.) were evaluated with respect to crown position, age of tissues and sampling date during a complete growing season. Concentrations of N, P, K, Ca, Mg and Zn in the needles and of N, P and K in the shoots differed significantly among the dates of sampling. The concentrations of N and Mn in the needles and all nutrients in the shoots (except Mg) also differed significantly with crown position. Maximum needle biomass was observed in the middle crown position (55% of the total) and maximum shoot biomass, in the lower crown position (52% of the total). Maximum needle and shoot nutrient contents were observed in the middle position of the living crown for long shoot, short shoot-1, short shoot-2, short shoot-3 and, short shoot-4 age classes while highest contents for short shoot-5 and short shoot-6 age classes were observed in the lower crown position. Biases up to 42% for Mg in the needles and 200% for K in the shoots were obtained when only long shoot tissues are used for content evaluation. For needles and shoots, Mg and K are more difficult nutrients to evaluate. A sampling methodology is proposed for evaluating nutrient contents of the living crown. Accepted: 10 August 1995     

Shoot elongation,leaf demography and bud formation in relation to branch position on Larix laricina saplings

Summary Shoot development was investigated on branches of Larix laricina (Du Roi) K. Koch trees growing in their 8th year in two plantations and in a natural stand approximately 12 years old. Expansion of throughout-crown series of short and long shoots was measured weekly, and later colour change and natural fall of leaves were assessed. Similar shoots were collected at intervals and dissected, the long shoots by 25-leaf segments. Leaf area and weight, as well as time of bud formation, were determined. Increasing acropetal trends were evident in time to bud burst: duration of short-shoot leaf-cluster expansion; size of leaf clusters and number, area and weight of leaves per cluster; duration and rate of long-shoot elongation; number, area and weight of leaves on long shoots; time to terminal-bud formation on long shoots. Along each long shoot, stem and leaf elongation and lateral-axis formation progressed acropetally. Lateral axes were most numerous on second to fourth 25-leaf segments. On longer shoots, some axes in middle segments developed as sylleptic short shoots rather than as lateral buds. Leaves of short shoots and basal leaves on long shoots turned yellow and abscissed sooner than axial leaves on long shoots. Colour change and loss among axial leaves were acropetal along shoots and up the crown. Thus, last-formed leaves, in axils of some of which lastformed lateral buds occurred, were held longest.     

Annual and spatial variation in shoot demography associated with masting in Betula grossa: comparison between mature trees and saplings

Backgrounds and Aims

Shoot demography affects the growth of the tree crown and the number of leaves on a tree. Masting may cause inter-annual and spatial variation in shoot demography of mature trees, which may in turn affect the resource budget of the tree. The aim of this study was to evaluate the effect of masting on the temporal and spatial variations in shoot demography of mature Betula grossa.

Methods

The shoot demography was analysed in the upper and lower parts of the tree crown in mature trees and saplings over 7 years. Mature trees and saplings were compared to differentiate the effect of masting from the effect of exogenous environment on shoot demography. The fate of different shoot types (reproductive, vegetative, short, long), shoot length and leaf area were investigated by monitoring and by retrospective survey using morphological markers on branches. The effects of year and branch position on demographic parameters were evaluated.

Key Results

Shoot increase rate, production of long shoots, bud mortality, length of long shoots and leaf area of a branch fluctuated periodically from year to year in mature trees over 7 years, in which two masting events occurred. Branches within a crown showed synchronized annual variation, and the extent of fluctuation was larger in the upper branches than the lower branches. Vegetative shoots varied in their bud differentiation each year and contributed to the dynamic shoot demography as much as did reproductive shoots, suggesting physiological integration in shoot demography through hormonal regulation and resource allocation.

Conclusions

Masting caused periodic annual variation in shoot demography of the mature trees and the effect was spatially variable within a tree crown. Since masting is a common phenomenon among tree species, annual variation in shoot demography and leaf area should be incorporated into resource allocation models of mature masting trees.     

Responses of crown architecture in Betula pendula to competition are dependent on the species of neighbouring trees

We measured the growth responses of individual shoots and branches of Betula pendula when growing next to trees of the same species or Pinus sylvestris, Larix sibirica or Alnus glutinosa. We used the three-dimensionally digitized response variables and the size and distance of trees growing within a 5-m radius of the study trees to establish a relationship between tree performance and the effect of competing neighbouring tree species on crown architecture. B. pendula was able to modify its crown architecture and thus alter its strategy to compete with different neighbours. Trees of B. pendula growing beside species counterparts had the highest growth of new long shoots in relation to the already existing branch length [growth vigour (GV)], while GV was the lowest next to L. sibirica. With B. pendula or P. sylvestris as its main neighbour, B. pendula invested in short shoots by growing them rather densely in short branches with limited numbers, whereas with L. sibirica the number, length and angle of the branches were high. The competitive response was also strongly dependent on tree ontogeny and the shoot and branch characteristics were significantly affected by their location inside the crown. B. pendula was able to respond to the challenges posed by its neighbours, which was also reflected in the GV. The ability to maintain steady growth with alternative crown designs in different neighbourhoods reflects plasticity in the crown responses.     

Gibberellin mediates daylength-controlled differentiation of vegetative meristems in strawberry (Fragaria × ananassa Duch)

Background  

Differentiation of long and short shoots is an important developmental trait in several species of the Rosaceae family. However, the physiological mechanisms controlling this differentiation are largely unknown. We have studied the role of gibberellin (GA) in regulation of shoot differentiation in strawberry (Fragaria × ananassa Duch.) cv. Korona. In strawberry, differentiation of axillary buds to runners (long shoot) or to crown branches (short shoot) is promoted by long-day and short-day conditions, respectively. Formation of crown branches is a prerequisite for satisfactory flowering because inflorescences are formed from the apical meristems of the crown.     

Cost and probability of flowering at the shoot level in relation to variability in shoot size within the crown of Vaccinium hirtum (Ericaceae)

Size-related variation in the cost and probability of flowering among shoots within a crown of Vaccinium hirtum was investigated to clarify patterns and regulation of flowering at the shoot-module level, below the level of the individual. The apices of previous-year shoots differentiated into current-year shoots vegetatively (vegetative branches) or became reproductive by developing inflorescences (reproductive branches). Length growth and fate of current-year shoots were determined, and the future potential for reproduction was estimated using a matrix model of shoot dynamics. Reproductive branches had fewer current-year shoots and shorter total shoot lengths and thus had a reduced potential for reproduction compared with vegetative branches, indicating the cost of flowering at the shoot level. This cost of flowering was higher in longer shoots. The probability of the initiation of flowering in a shoot increased with increasing shoot length in shorter shoots, reached a maximum in medium-sized shoots, and decreased in longer shoots. The size-related changes in the probability of flowering at the shoot level can be largely explained by the size-dependent changes in shoot-level resource availability and cost of flowering.     

Factors controlling resource allocation in mountain birch

We present a comprehensive analysis of factors affecting resource allocation and crown formation in a subarctic birch tree, Betula pubescens ssp. czerepanovii (Orlova) Hämet-Ahti. Using biomass measurements and digitized data on tree architecture, we investigated several hypotheses on various factors that may modify plant growth. We also analyzed the extent to which different mechanisms operate at different scales, ranging from individual shoots to the whole branches or trees. Different factors affected allocation at different levels of organization. Stem age had a minor effect, suggesting that similar control mechanisms operate at all stages of development. Fates of individual shoots were affected by their local growing conditions as indicated, for example, by the dependence of long shoot production on light. Buds formed in the current long shoots were likely to become new long shoots. In the innermost crown parts, radial growth had priority compared to long shoot production. Elongation of individual long shoots was controlled by two conflicting factors. Long distance from the roots suppressed growth, probably indicating costs associated with resource transportation, whereas a high level of light augmented growth. In contrast, growth of entire branches was not so clearly related to the availability of resources, but showed limitation due to allometric scaling. This set a relationship between the maximum long shoot number and the overall branch size, and may indicate allometric constraints to the way a tree is constructed. Strict allometric relationships existed also between other structural traits of mountain birch, most of them similar at all levels of branching hierarchy. However, despite the upper level restrictions set by allometry, source-sink interactions and localized responses of individual shoots operated as local processes that directed allocation towards the most favourable positions. This may be a mechanism for achieving efficient tree architecture in terms of resource intake and costs of transportation.     

EXPERIMENTAL CONTROL OF THE SHOOT SYSTEM IN SPORELINGS OF PTERIDIUM AQUILINUM

The shoot system of Pteridium develops from a simple, upright sporeling type through a rhizomatous leaf-bearing form, into a complex system with rapidly growing, leafless long shoots and slowly growing, leafy lateral branches or short shoots. Transitional stages axe available in sporeling material and ontogeny may be controlled by specific carbohydrate levels. At concentrations of sucrose below 2% a rhizomatous sporeling plant may be maintained indefinitely in the leaf-bearing state. At 2–8% sucrose, the short shoot habit becomes established, and at 4–8% it may be reliably stabilized. If concentrations up to 5 mg/liter of kinetin are added to cultures of intact plants or to excised short and long shoot apices of plants, the long shoots expand slowly into determined (no further growth possible even on transfer back to basal medium) club-shaped tips. The short shoot apices, by contrast, quickly proliferate into callus-like masses and will re-form organized meristems over the entire lobulate surface on transfer to medium lacking kinetin. The morphogenetic significance of these findings is discussed.     

The Effect of Bud Position on Branch Growth and Bud Abscission in Quercus petraea (Matt.) Liebl.

The time at which a bud began to expand was related to its positionnot only on an individual shoot but also within the crown. Thedistribution of buds and branches on the shoot was uneven; theshoot tip, where they were densely clustered, was termed the‘whorl; and the remainder of the shoot, where they werewidely spaced, the ‘interwhorl’ stem. In spring,the terminal bud started expanding before the ‘whorl’buds which preceded the ‘interwhorl’ stem buds;completion of the flush of growth, determined by the end ofleaf expansion, occurred in the reverse order, ‘interwhorl’> ‘whorl’ > terminal. Similarly bud expansionstarted at the top of the crown and progressed downwards, andthe first shoots to complete their flush were at the bottomof the crown. Approximately 60% of the buds on each shoot beganexpanding in spring but only about half of these formed branches.Bud abscission began in May and by Sep. 45% of buds originallypresent had abscised. Most of-the buds that did not abscisewere the small buds at the base of the shoot that were not originallyassociated with a leaf. Approximately 42% of ‘whorl’buds and 28% of MnterwhorP stem buds formed branches. ‘Whorl’branches were approx. 60% longer that ‘interwhorl’stem branches; buds on the lower surface of the shoot producedlonger branches than those on the upper surface. The implicationsof the results for the development of crown form and selectionof superior oak are discussed. Quercus petraea, oak, buds, branches, crown form     

Plant module size influences the intra‐tree distribution and abundance of a shoot‐boring sawfly in young balsam fir

Field surveys were carried out to assess the effects of intra‐tree variation in developing shoot length within and among crown levels on the density and abundance of the balsam shoot‐boring sawfly, Pleroneura brunneicornis Rohwer (Hymenoptera: Xyelidae), in young balsam fir, Abies balsamea (L.) Mill. (Pinaceae). Overall, cardinal direction had no influence on shoot‐borer density or abundance; however, the highest percentage and abundance of bored shoots occurred on intermediate‐sized shoots within the crown (i.e., in the mid‐crown and on the distal‐lateral and medial‐lateral shoots). Comparatively, few shoot borers occurred in the upper or lower crown levels, or on the relatively large terminal shoots within branches. This distribution appears indicative of the higher suitability of intermediate‐sized shoots within hosts for either egg lay or larval performance. Results of this study are most consistent with predictions of the ‘optimal module size’ hypothesis, which posits that herbivore responses to plant module size should reflect the balance of tradeoffs between utilizing relatively large, nutritious shoots vs. small, more easily exploited shoots.