Changing regularity of plant and insect community characteristics due to pest outbreaks in Larix principis- rupprechtii plantations

Research has indicated that simple forest eco-system composition,structure and diversity have uncompli-cated community relationships and insufficient pest control capabilities.To investigate changing characteristics of plant and insect communities in under pest outbreaks in Larix principis-rupprechtii plantations,the research areas were defined as mature(48–50 years)and young(24–29 years)infested stands along with healthy stands.The results show a reduction in the complexity and diversity of plant communi-ties and herbaceous plant guilds(polycultures of beneficial plants)and the complexity and dominance of insect com-munities,especially natural insect enemies.The results also show the relative simplicity of the main factors of commu-nity change and development that represent the characteris-tics of pest outbreaks in L.principis-rupprechtii plantations.The complexity and diversity of plant communities,particu-larly herbaceous plant guilds play a fundamental role in the regulation and development in forest ecosystems.

Interpreting Larix principis-rupprechtii radial growth in northern China based on the Vaganov-Shashkin model

Changes in annual radial growth is an important indication of climate change. Dendroclimatology studies in northern China have focused on linear statistical analysis,but lacking studies based on the process of ring formation to clarify the radial growth of trees. Tree-ring width standard chronology(STD) was established using samples of Larix principis-rupprechtii collected at 2303 m altitude on Luya Mountain. Using the Vaganov-Shashkin(VS) model to simulate growth and development, the internal physiological mechanism of radial growth is identified. It was concluded that:(1) the growing season of L. principis-rupprechtii was May to September;(2) soil moisture was a significant factor in the early and late growing seasons, and temperature was the dominant factor in its main growth period;and(3) formation of narrow ring widths was closely related to drought stress, the development of wide ring widths will be restricted by increasing future temperatures. The VS model is applicable for radial growth simulation of subalpine coniferous forests and for guiding the cultivation of local tree species in the future.

Stem Respiration of a Larch (Larix gmelini) Plantation in Northeast China

Stem respiration is an important part of the activity of a tree and is an important source of CO2 evolution from a forest ecosystem. Presently, no standard methods are available for the accurate estimation of total stem CO2 efflux from a forest. In the current study, a 33-year-old (by the year 2001) larch (Larix gmelini Rupr.) plantation was measured throughout 2001-2002 to analyze its monthly and seasonal patterns of stem respiration. Stem respiration rate was also measured at different heights, at different daily intervals and any variation in the larch plantation was recorded. The relationship between stem temperature, growth status and respiration rate was analyzed. Higher respiration rates were recorded in upper reaches of the larch tree throughout the season and these were affected partially by temperature difference. Midday depression was found in the diurnal changes in stem respiration. In the morning, but not in the afternoon, stem respiration was positively correlated with stem temperature. The reason for this variation may be attributed to water deficit, which was stronger in the afternoon. In the larch plantation, a maximum 7-fold variation in stem respiration was found. The growth status (such as mean growth rate of stem and canopy projection area) instead of stem temperature difference was positively correlated with this large variation. An S-model (sigmoid curve) or Power model shows the greatest regression of the field data. In the courses of seasonal and annual changes of stem respiration, peak values were observed in July of both years, but substantial interannual differences in magnitude were observed. An exponential model can clearly show this regression of the temperature-respiration relationship. In our results, Q(10) values ranged from 2.22 in 2001 to 3.53 in 2002. Therefore, estimation of total stem CO2 efflux only by a constant Q(10) value may give biased results. More parameters of growth status and water status should be considered for more accurate estimation.

华北落叶松(Larix principis-rupprechtii)林大步甲属(Carabus)物种多样性及其变化

在山西庞泉沟国家自然保护区华北落叶松不同林龄的人工林和天然林内，利用巴氏罐诱法，对其地表甲虫大步甲属Carabus物种进行了系统的调查，结果表明：（1）共获得大步甲属标本1290号，分属于10种，9种是该保护区的新记录种类，其中ecanaliculatus沟步甲、ccrassesculptus粗皱步甲、C．maniifestus罕丽步甲、cvladimirskyi长叶步甲为优势种，肩步甲c．hummeli、刻翅步甲C.scultipennis、粒步甲C．granulatus为常见种。（2）不同林地物种丰富度S、多样性H＇、优势度D、个体数量Ⅳ存在显著差异，均匀度J不存在显著差异；S、H’、D、J在人工林25年生林地最高；N在天然林20～30年生林地最多；β多样性人工林5年生林地最高。（3）4种优势种季节性变化总体上是沟步甲的盛发期为7月和8月份；粗皱步甲的高峰期为7月份；罕丽步甲7月、5月、9月份和6月份发生数量多，8月份稀有；长叶步甲8月份和9月份为盛发期；不同物种在不同林地出现的高峰期是不一致的。（4）物种相似性分析结果是天然林35～45a和60～80a，人工林25a和天然林5—8a极相似，其余为中等不相似和中等相似。（5）生境相似性分析的结果是天然林35～45a和60～80a相似性最高，人工林5年生与天然林20～30a、35—45a生境相似性差异逐渐增大。（6）生境指示种分析的结果是粗皱步甲、罕丽步甲为广布种，肩步甲仅在天然林35～45a和60～80a生的林地采集到，其中在天然林35～45a林地生境物种指示值高达96．73。

Phenological observations on Larix principis-rupprechtii Mayr. in primary seed orchard

Through 5 years of phenological observations on Larix principis-rupprechtii Mayr. in primary seed orchard and studies on population and individuals of clones, the annual periodic phenological laws were revealed and the annual phe-nological periodic table was drawn up. The correlation between various phenophases, the air temperature and active accumu-lated temperature were analyzed and expounded. The authors also analyzed the similarities and differences of phenophases among clonal individuals as well as the blooming properties of male and female flowers at the same time. This study could pro-vide theoretical reference for working out the production plan of improved varieties and other management measures in seed orchard of Larix principis-rupprechtii.

Effects of Exogenous Organic Acids on Phosphorus Availability of Dark Brown Forest Soils and Phosphorus Absorption and Accumulation of Larix olgensis Seedlings with Nutrient Deficiency

Different proportions of A1 and B horizons dark brown forest soils （A1∶B=1∶2） were utilized to set the soil nutrient deficient conditions, and Larix olgensis seedlings were cultivated. By simulating organic acids concentrations in forest litter leachates of northeast China, the effects and mechanism of different concentrations of organic acid solutions on phosphorus （P） availability of dark brown forest soils and P absorption of Larix olgensis seedlings with nutrient deficiency were studied. The results showed that, compared with A1 horizon soils, available P contents of mixed soils in A1 and B horizons decreased, and P accumulation and efficiency of P uptake in root and leaves of Larix olgensis seedlings also decreased, but efficiency of P utilization increased. After treatments of exogenous organic acids, available P contents of mixed soils increased and the impact sequence of different organic acids were succinic acid 〉 citric acid 〉 oxalic acid; the concentration of 5.0 mmol/L had the best function, and the best effect of organic acids was at 20 d. Organic acids also increased P accumulation and efficiency of P uptake in roots and leaves of Larix olgensis seedlings, but decreased efficiency of P utilization. The impact strength of organic acids on P accumulation and efficiency of P uptake varied with treatment time, type and concentration of organic acids. The results of 20 d and 30 d in roots were higher than those of 10 d, however, the results of 10 d and 20 d in leaves were higher than those of 30 d, thus, at the earlier stage of organic acids treatments, more P absorbed were transferred to leaves, and at the later stage, more P would be accumulated in roots. The concentration of 10.0 mmol/L had the best function, and the impact sequence of different organic acids was succinic acid 〉 citric acid 〉 oxalic acid. Therefore, organic acids might contribute to P absorption and accumulation by Larix olgensis seedlings, final y increasing the adaptability and endurance of Larix olgensis seedlings to nutrient deficient soils.

Studies on the Secretion of Organic Acids from Roots of Two-year-old Larix olgensis under Nutrient and Water Stress

[Objective] This study aimed to investigate the effects of nutrient and water stress on the secretion of organic acids from roots of two-year-old Larix olgensis. [Method] Different nutrient and water stress conditions were designed to investi- gate the types and quantities of organic acids secreted from roots of two-year-old L. olgensis. [Result] Under nutrient and water stress, the types of organic acids secreted from roots of two-year-old L. olgensis increased, which varied with different stress levels. In addition, nutrient and water stress also increased the secretory vol- ume of organic acids from roots of two-year-old L. olgensis. The increment in total amount of organic acids reached the maximum under Level 1 （high stress）. Among different types of organic acids, the increment in secretory volume of citric acid reached the maximum, followed by malic acid, while oxalic acid presented relatively small increment. Furthermore, the increment in secretory volume of these three organic acids all reached the maximum under Level 1. [Conclusion] The proportion of the secretory volume of each organic acid accounting for the total amount of organic acids varied slightly, but the overall order was unchanged.

Analysis on Natural Regeneration Characteristics and Growth Factors of Two Cut-over Lands of Larix gmelini Forests in Greater Khingan Mountains

[Objective] This study aims to analyze the natural regeneration characteristics and growth factors of two cut-over lands of Larix gmelini forests in Greater Khingan Mountains. [Method] A database was established based on the information of natural regeneration cut-over sample plots of Larix gmelini forests in Greater Khingan Mountains. Natural regeneration characteristics of clear-cutting sample plot and shelterwood-cutting sample plot of Larix gmelini in the northern regions of Greater Khingan Mountains were investigated by programming analysis. [Result] The natural regeneration of two principal felling systems was both good, and that of shelterwood-cutting sample plot was better. There were significant linear regression relationships among various growth factors of naturally regenerated plants. [Conclusion] This study provided scientific theoretical guidance for subsequent deforestation and regeneration in Greater Khingan Mountains.

Genetic Variation and Differentiation of Larix decidua Populations in Swiss Alps

Genetic diversity within and among six subpopulations of Larix decidua Mill. from two altitudinal transects of Swiss Alps was investigated using 6 enzyme systems coding for 8 loci. Globally, the mean proportion of polymorphic loci was 22.9%, the average number of alleles per locus was 1.3, and the mean expected heterozygosity was 0.095. Only 5.8% of the genetic variation resided among populations. The mean genetic distance was 0.006. Several significant differences of gene frequencies were found between different age classes. Positive values of the species mean fixation index observed in this study suggested a considerable deficit of heterozygotes in the populations of L. decidua of Swiss Alps. At one of the sites (Arpette), the highest subpopulation in elevation gave the lowest level of genetic diversity (as evidenced by the lowest proportion of polymorphic loci and the lowest mean expected heterozygosity) and the largest value of genetic distance when compared to other subpopulations. The genetic differences between the highest subpopulation and the other ones suggest that the founder effect may be an important factor influencing genetic differentiation of L. decidua populations at Arpette transect.

移栽自不同纬度的落叶松(Larix gmelinii Rupr.)林的春季土壤呼吸

以往的土壤呼吸(RS)研究大多集中于生长季,而对非生长季RS的认知甚少。常见于中高纬度地区的春季土壤冻融交替是影响陆地生态系统碳循环的关键事件,是RS年内变化格局的转折期。但是春季冻融交替期间RS的动态规律及其机理过程尚缺乏了解。研究以我国北方森林的优势类型——兴安落叶松(Larix gmelinii Rupr.)林为对象,在其自然分布区内,将地处4个纬度(处理)的8年生兴安落叶松林生态系统整体移至其分布区的南缘,以模拟气候暖化对RS及其组分的影响。在春季土壤冻融交替时期,采用红外气体分析法和根系排除法测定了移栽自不同纬度的落叶松林的RS和异养呼吸(RH)及其相关的环境因子。研究结果表明:RS与温度的耦联关系随土壤解冻进程而变化。在解冻初期和中期,RS的日进程与温度解耦联,但在土壤完全解冻后却强烈地依赖于土壤温度。从整个土壤解冻过程看,4个处理的RS和RH与土壤温度和含水量相关极显著(R2=0.569～0.743,P<0.001)。解冻的初期和中期的RS基本上来自RH组分,土壤根际呼吸(RR)到4月底才出现。RS和RH均受到实验处理、解冻时期及其交互作用的显著影响。RS和RH的平均值随着解冻的进程而增大,而且RS与RH之间的差异也随之增大。RS波动在0.50～3.30μmolCO2m-2s-1之间;而RH则波动在0.52～3.04μmolCO2m-2s-1之间。在相同气候条件下,4个处理RS有随着纬度的增加而增加的趋势,而且RS对土壤温度的响应程度也随纬度增加而增加。研究结果意味着土壤解冻期间来自纬度较高的兴安落叶松林的R对气候变暖方案的响应可能更为强烈。

Characteristics of Reproductive Biology for Larix Originating in Japan

The paper summarized the life cycle ,environmental features and distributions of Larix origination in Japan.The time of blooming and fruiting and the ways of cone collection and seeds storage were introduced.The treating methods of seeds germination and the sowing time for both Japanese larch (Larix kaempferi Carr)and Dahurian larch (Larix gmelinii var.Japonica Pilger) were discussed.

兴安落叶松(Larix gmelini)幼中龄林的生物量与碳汇功能

兴安落叶松是我国的主要用材林,由于传统上对木材的长期依赖,使得其资源受到破坏,年龄结构发生改变,成过熟的原始林日渐减少,绝大部分是次生的幼中龄林。因此,研究其幼中龄林的生物量及碳汇功能很重要。森林生物量与森林生态系统的固碳能力密切相关,生物量与碳储量的多少直接影响到森林生态系统的功能,因而生物量与碳储量问题成为不同尺度生态学研究的热点。以我国大兴安岭兴安落叶松林为研究对象,通过样地调查,并结合我国森林资源清查资料对内蒙古大兴安岭地区兴安落叶松林的幼中龄林的生物量转换因子(BEF)、生物量及碳储量、碳密度、碳汇功能等进行了估算。通过实测数据及模型分析,得出以下基本结论:研究对象的BEF在0.4557与0.6988之间变动,平均值为0.5332。干、皮、枝、叶各组分生物量的分配比为:68.74:14.86:10.54:5.86。分别树干、树皮、枝、叶等组分,对其生物量与蓄积量的关系进行了拟合,建立了多组分生物量蓄积量的相关模型,分别是:干:y=0.4683x-11.291;皮:y=0.0472x+3.5674;枝:y=0.0415x+1.6787;叶:y=0.0197x+1·3405,均有很好的线性关系。地上生物量随蓄积量的增加而增加,其线性关系为:B=0.5767V-4.7042。利用近期清查数据,按材积源生物量法推算总生物量为9.49×107t,按0.5097的含碳率计算,得出兴安落叶松林幼中龄林总的碳储量为4.84×107t,碳密度为19.616t/hm2。通过两期数据对比分析,5a间所研究林分的碳储量增加0.89×107t,碳密度增加0.404t/hm2,说明其发挥着一定的碳汇作用。尽管近年来大兴安岭兴安落叶松林表现出了明显的碳汇功能,但整体上碳固定能力还不强,碳密度低于我国平均森林碳密度。应通过科学经营,挖掘潜力,使大兴安岭地区的森林生态系统在全球碳循环中发挥更大的作用。

六盘山南坡华北落叶松(Larix principis-rupprechtii)树干直径生长及其对气象因子的响应

2005年6~9月份在宁夏六盘山南侧的西峡林场,应用带状树木径向变化记录仪(Dendrom eter)研究了5株华北落叶松树干的直径生长过程,结果表明,在无雨或小雨(日降雨量<10mm)天气下,树干直径变化呈现出明显的日周期性,可将其划分为3个阶段:收缩阶段、膨胀阶段和生长阶段;在连续降雨(日降雨量≥10mm)及随后的几个晴天中,树干直径变化并不表现出完整的日周期性。基于Deslauriers等人的方法,提出了树干直径日生长量估计的修正公式,并计算了华北落叶松树干直径日生长量和累积生长量,结果表明,各样木树干直径日生长量的季节变化趋势一致,即表现为前快后慢的季节变化格局,6~7月份为快速生长期,其日均生长量在27.0~44.2μm之间;8~9月份为缓慢生长期,其日均生长量在10μm以下;各测定样木的树干直径日生长量具有明显的个体差异,这主要与林木个体大小及其所处林分中的微环境条件差异有关;整个观测期内的树干直径累积生长过程可以较好地用幂函数描述。主分量分析和偏相关分析表明,影响树干径向生长的气象因子可划分为3类,其中日降雨量、日最低气温、日平均太阳辐射和日平均空气饱和差是影响树干径向生长的主要因子。

辽东山区长白落叶松(Larix olgensis)种子雨和种子库

长白落叶松是东北地区主要的用材树种，其种子雨和种子库研究鲜见报道。在辽东山区用收集器收集的种子分析了长白落叶松种子雨组成、质量和扩散距离，每隔2个月调查1次种子库数量，并结合靛蓝染色法测定每次种子的活力来分析土壤种子库动态。结果表明，辽东山区的长白落叶松种子雨从8月中旬开始，9月末到10月初达到高峰期，11月初结束。在起始期，种子雨以干瘪的不完整种子为主，而从高峰期开始，种子雨以完整种子为主。整个长白落叶松种子雨中不完整种子约占种子雨总量的45％，这些不完整种子由被动物取食、空粒和病虫害危害种子组成。完整种子的平均生活力为56．4％，即有活力的种子仅占整个种子雨的30％。种子雨集中在母树周围，在林缘1次扩散距离一般不超过1．5倍树高。种子雨到达地面之后，主要分布在枯枝落叶层，土壤0—5em层有少量分布，土壤5em以下没有种子分布；土壤种子库的种子主要在翌年雪融化后开始萌发、被取食、搬运以及腐烂，其中腐烂种子数占45．4％，动物取食为30．0％。种子库的种子数量和活力在冬季没有明显变化，而在翌年，种子数量和活力明显减少，4、6月和8月份种子数量分别为（506．3±35．56）粒m^-2，（267．1±17．47）粒m^-2和（143．6±9．83）粒m^-2，对应的活力分别为47．8％±4．68％，19．4％±3．39％和0％，这表明长白落叶松种子不能在地面形成连续的种子库。

太白红杉(Larix chinensis)混交林径级结构与竞争的关系

混交林的径级结构和竞争关系的研究可在一定程度上预测群落的动态变化趋势。探讨了太白山太白红杉(Larix chinensis)混交林的径级结构和竞争关系,并对该区域森林的动态变化趋势进行了预测。结果表明:①在混交林内,太白红杉幼苗数量较少,更新差,种群径级结构呈衰退型;而巴山冷杉(Abiesfargesii)幼苗数量较多,更新良好,种群径级结构为增长型。②太白红杉种内竞争强度大于种间竞争强度,巴山冷杉种内竞争强度小于种间竞争强度。在混交区域,巴山冷杉处于群落的优势地位,而太白红杉处于劣势地位,应加强对太白红杉的保护,合理抚育管理太白红杉幼苗。

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。

兴安落叶松(Larix gmelinii Rupr.)叶片养分的空间分布格局

对中国东北温带森林生态系统主要树种兴安落叶松(Larix gmelinii Rupr.)24个采样点72个叶片样品有机碳(C)、全氮(N)、全磷(P)和全钾(K)的化学组成、地理分布格局及其与气候因子的关系进行了研究。结果表明,叶片C、N、P和K含量的几何平均数分别为543.970、16.902、2.373mg/g和14.625mg/g,且叶片的C含量>N含量>K含量>P含量;叶片的C/N、C/P和N/P分别为32.183、229.226和7.123。随纬度的增加、年均温度和年均降雨量的降低,兴安落叶松叶片C、N含量和N/P显著降低,叶片C/N和K含量显著升高,叶片P含量和C/P的变化没有达到显著水平。叶片N含量随纬度与年均温度的变化与全球及其它大尺度的研究结果相反,而N/P与其一致,这与在该区域的其它物种的研究结果基本一致。这可能是由于在本研究区域北部寒温带越往高纬度地区年均温度和年均降雨量越低、生长季越短,因此成土作用弱导致植物可以吸收利用的养分越少,但是由于植物显著降低的N含量和变化不明显的P含量导致了叶片N/P随纬度的增加和年均温度和年均降雨量的降低而降低,这与全球尺度的研究结果一致。兴安落叶松叶片养分分布格局与全球尺度和中国区域研究结果的差异说明了加强区域叶片养分特征研究的重要性。叶片养分与气候因子的显著线性相关说明气候因子是影响叶片养分特征的一个主要因子。

太白红杉(Larix chinensis)叶的形态解剖学特征与环境因子的关系

根据生态气候学方法推断出不同海拔高度气候指标 ,应用多元统计方法 ,对分布于秦岭太白山地区海拔 30 0 0～ 340 0 m的太白红杉 ( L arix chinensis)叶特征进行了生态解剖学研究 ,分析了影响其变化的主导生态因子。观察指标包括叶形态指标 (叶片总厚度、每束叶中的叶数和叶长宽比 )、叶解剖学特征 (叶表皮角质膜厚度 ,上、下表皮厚度 ,近上、下表皮叶肉厚度 ,内皮层厚度 ,管胞直径 ,叶转输组织和维管束厚度及其与叶片总厚度之比 )。结果表明 :1水热综合因子是影响太白红杉叶长宽比和叶表皮角质膜厚度的主导因子 ,随着水热综合因子的增大 ,叶长宽比呈增加趋势 ,而角质膜厚度则逐渐变薄。2年降水量是影响其它形态解剖学指标的主导因子 ,随着年降水量的增加 ,每束叶中的叶数、叶厚度、管胞直径、叶转输组织和维管束厚度、内皮层厚度、转输组织和维管束厚度及其与叶总厚度之比呈减少和变薄的趋势 ,而上、下表皮厚度则逐渐增加。 3近上、下表皮叶肉厚度与环境因子无明显相关 。

芦芽山华北落叶松(Larix principis-rupprechtii)树轮宽度年表对气候因子的响应

在芦芽山地区采集3个不同海拔的华北落叶松(Larix principis-rupprechtii),在传统去趋势的基础上,采用"signal-free"方法对拟合曲线进行修正,避免了中等频率的气候信息引起的拟合偏差,最终建立3个不同海拔树轮宽度标准年表(STD)。同时以10a为界对上述年表进行滤波处理,得到3个低频年表。年表特征值表明,随着海拔升高,年轮平均轮宽变窄,敏感性和高频信息增强,低频信息减弱,这可能与逐渐恶劣的生境有关。中、低海拔年表的低频信息更一致,中、高海拔的高频信息更接近,而高、低海拔无论是标准年表还是高频、低频年表相似性均较差。树轮气候响应分析显示,低海拔STD年表与5月最低温负相关最为显著,STD和低频年表均与5、6月份土壤温度显著负相关,说明生境暖干,树木主要受生长季的干旱胁迫;中海拔STD年表与当年5月最高温正相关最为显著,STD和低频年表与土壤温度相关均不显著,说明生境逐渐变得冷湿,生长季的低温成为树木生长的限制因子;高海拔STD年表与气象要素相关不显著,低频年表与当年4月土壤温度正相关,说明高海拔最为冷湿,并有季节性冻土分布,生长季的土壤低温成为树木生长的限制因子。因此,全球变暖的趋势将更有利于高海拔树木的生长,而低海拔树木的干旱胁迫进一步加剧。

兴安落叶松(Larix gmelinii)光合能力及相关因子的种源差异

为认识我国北方森林的优势树种——兴安落叶松（Larix gmelinii Rupr．）光合作用对环境变化的响应和适应特征，在其自然分布区内选择地理和气候差异显著的6个种源，采集种子并播植于其分布区南界的均一立地条件下26a后，测定针叶的光合能力及其相关因子，比较种源间差异及其随月份和冠层位置的变化。结果表明：最大净光合速率（Pmax）、表观光量子效率（AQY）、比叶重（LMA）和单位叶面积氮含量（虬）的种源差异显著（P〈0．05），变化幅度分别为6．10～8．78μmolCO2·m^-2·s^-1、0．0325—0．0427μmolCO2·μmol^-1 photons、85．1～114．3g·m^-2和1．72～2．26g·m^-2。但是光补偿点（LCP）、光饱和点（LSP）、暗呼吸速率（Rd）和单位面积叶绿素含量（Chla）的种源差异不显著，平均值分别为61．2μmolphotons·m^-2·s^-1、1093txmolphotons·m^-2·s^-1、2．34txmolCO2·m^-2·s^-1和0．12g·m^-2。Pmax、Chla、No和LMA两两之间均呈极显著正相关（p〈0．001）。随树冠从下往上升高，Pmax、LCP、Na和LMA呈逐渐增高的趋势，这种垂直变化格局受种源的显著影响。除AQY之外，种源对光合能力及其相关因子的月份变化格局没有显著影响，多表现为7月低-8月高-9月低的变化格局。研究展示的兴安落叶松针叶的光合能力及其一些相关因子的种源间差异可能是其光合机构对种源地环境条件长期生理适应的结果。