贵州野生柑橘的抗寒性测定和综合评价

以贵州3个野生柑橘种类宜昌橙、酸橙、白黎檬和栽培品种‘默科特’的一年生枝条为试材,人工设置4℃(CK)、0℃、-5℃、-10℃、-15℃、-20℃、-25℃低温冷冻处理24h,研究了4个柑橘种类枝条膜脂过氧化作用、抗氧化酶活性和有机渗透调节物质的变化,并应用Logistic方程建立回归模型确定其半致死温度(LT50),应用隶属函数法综合评价野生柑橘种类的抗寒性。结果表明:(1)随着温度的降低,4个柑橘种类枝条的电解质外渗率均呈"S"型上升,SOD、POD活性以及可溶性蛋白、可溶性糖含量均先升后降,MDA含量在宜昌橙枝条中逐渐缓慢上升,在其余材料枝条中则先升高后下降;栽培品种‘默科特’枝条的保护酶活性、渗透调节物质含量在0℃或者-5℃达到峰值,而宜昌橙则在-15℃或者-20℃达到最大值,两者的MDA含量则分别在-15℃和-25℃达到最大值。(2)利用电解质外渗率拟合Logistic方程推算的宜昌橙、酸橙、白黎檬和‘默科特’的低温半致死温度分别为-14.86℃、-7.28℃、-8.45℃和-5.88℃;用隶属函数法与Logistic方程分析所得各柑橘种类的抗寒性强弱结果基本一致,4个柑橘种类的抗寒性强弱顺序为:宜昌橙酸橙白黎檬‘默科特’。研究认为,抗寒性强的柑橘枝条的保护酶活性、渗透调节物质和MDA含量达到峰值的温度更低,具有更强的抗氧化胁迫能力和渗透调节能力,且野生柑橘的抗寒性较栽培种强;半致死温度和隶属函数法均可有效评价柑橘种类的抗寒性。     

水杨酸对大花三色堇幼苗耐热性的影响

大花三色堇性喜冷凉、忌酷热。该研究以大花三色堇3个自交系08H 、HAR 和 E01为材料,分别测定了40℃高温处理4、8和12 h 时不同基因型大花三色堇幼苗的生理指标,以及不同浓度(0.1、1、2 mmol?L-1)水杨酸预处理对热胁迫下大花三色堇幼苗耐热性的影响。结果表明：在高温胁迫下大花三色堇电解质外渗量增加,随着处理时间的延长,电解质外渗更多,可溶性糖含量先增加后降低,POD 酶活性先提高后降低;与其他2个自交系相比,HAR 表现出较好的耐热性,其可溶性糖含量、POD 酶活性的增加均较高,而电解质外渗率偏低;与对照相比,3种浓度 SA 预处理均显著降低了大花三色堇幼苗的电解质外渗率,增加了幼苗体内可溶性糖含量,提高了大花三色堇的幼苗体内脯氨酸含量和 POD 酶活性;其中1 mmol?L-1的 SA 预处理对高温胁迫下大花三色堇幼苗体内可溶性糖的含量增加最高,最大程度减缓幼苗体内的电解质外渗量,08H 和 HAR 的脯氨酸含量和 POD 酶活性达到最大值。而对 E01而言,0.1 mmol?L-1的水杨酸预处理的脯氨酸含量和 POD 酶活性最高。该研究结果探讨了高温胁迫下不同基因型大花三色堇幼苗的生理表现,以及外施水杨酸对增强大花三色堇幼苗耐热性的效果,为大花三色堇抗热栽培提供重要的基础资料。     

低温胁迫对4种常绿阔叶植物膜脂过氧化及保护酶活性的影响

选取我国北方4种常绿园林树木大叶女贞、广玉兰、小叶女贞、黄杨的当年生枝条和叶片为试材,采用人工冷冻处理,经过对不同处理温度后各树种叶片的失水率、保护酶的活性、MDA含量和枝条及叶片细胞膜透性等指标进行测定分析。研究结果：表明随着处理温度的降低,各树种叶片和枝条的相对电导率值呈上趋势,在4个树种中黄杨上升得较缓慢,而小叶女贞上升的幅度最高,同一处理温度下,各树种枝条的相对电导率低于其叶片的相对电导率;黄杨MDA含量随处理温度的降低表现为先降低后增加的变化趋势,在-20~0℃之间MDA含量均有所下降,而其他树种MDA总体含量随处理温度的降低表现为增加的变化趋势;各树种叶片SOD酶活性均表现为随着温度的降低呈先升高后降低的变化趋势,但各树种SOD酶活性趋势发生变化的温度不同,而POD酶活性随处理温度的降低基本表现为逐渐降低的变化趋势。根据各项指标测定结果对4种树种的抗寒性强弱进行比较,结果为：黄杨＞广玉兰＞大叶女贞＞小叶女贞。     

混合盐碱胁迫对青山杨渗透调节物质及活性氧代谢的影响

为研究青山杨(Populus pseudo-cathayana × P. deltoides)对盐碱的适应能力,对青山杨2年生扦插苗进行不同盐度和碱度的28组胁迫处理.结果表明：随盐浓度增加,青山杨叶片的电解质外渗率、丙二醛和脯氨酸含量呈上升趋势,可溶性糖、SOD和POD活性先升后降.pH值升高使电解质外渗率、丙二醛和POD活性呈上升趋势,脯氨酸和可溶性糖含量先升后降,SOD活性上升趋势不明显.盐浓度低于100 mmol·L^-1时,随pH值升高,各项生理指标的变化不明显,SOD具有较高的活性;盐浓度在200 mmol·L^-1、pH 8.99以上时,其电解质外渗率在50%以上,POD活性和丙二醛含量大幅度增加,脯氨酸和可溶性糖含量下降,SOD活性较低.推断盐浓度>200 mmol·L^-1、pH>8.99的盐碱条件不适宜青山杨的生长.     

2个欧李品种对碳酸盐胁迫生理响应的初步研究

在盆栽条件下,以不同浓度的NaHCO₃溶液浇灌农大欧李3和4号2年生组培苗,测定苗木叶片的生理指标。结果表明：随胁迫时间的延长,两个品种的叶绿素a呈先变化平缓后降低趋势,各处理间差异显著;叶绿素a/b在整个处理时期变化平稳;脯氨酸呈先变化平缓后升高趋势;农大欧李3号的电解质外渗率、MDA和POD活性呈先变化平缓后升高再降低的趋势,各处理间差异不显著;中、低浓度SOD活性整个胁迫期变化平缓,高浓度的在整个胁迫期间变化较大,各处理间差异极其显著;农大欧李4号电解质外渗率、SOD、POD和MDA在处理期间呈先升高后降低趋势,胁迫解除后,高浓度处理的电解质外渗率、SOD、POD活性上升、低浓度处理下降,MDA则相反。在长期的NaHCO₃胁迫过程中,农大欧李3号和4号都显示了强的耐盐性。     

夏季栾树群落冠层结构对其环境温湿度的调节作用

为探究栾树群落降温增湿作用与其冠层结构参数的相关性在一天中的变化趋势,于天气晴朗的夏季对北京奥林匹克森林公园栾树群落内部和对照点的温度、相对湿度、群落冠层结构参数进行了铡定.结果表明:栾树群落的郁闭度与叶面积指数、平均叶倾角呈显著相关,且叶面积指数与平均叶倾角呈显著相关;在夏季8:00-18:00,栾树群落可降低空气温度0.43～7.53℃,在12:00左右达到降温最大值,增加相对湿度1％ ～ 22％,且在10:00左右增湿作用最显著,而在18:00-次日8:00降温增湿效果不明显;9:00-12:00,郁闭度和叶面积指数显著影响栾树群落的降温增湿作用;12:00-14:00,仅郁闭度与降温增湿作用显著相关;直到18:00,郁闭度和叶面积指数共同决定了栾树群落的降温增湿作用.因此,影响栾树群落降温增湿作用的冠层结构参数在一天中随着时间的推移发生变化.     

不同模型对黄山栾树快速光曲线拟合效果的比较

用Li-6400光合仪同时测定了CO2浓度为380和600μmol·mol-1条件下黄山栾树的光响应曲线和快速光曲线,分别采用不同模型进行了拟合.结果表明:直角双曲线模型和双指数方程拟合得到的最大电子传递速率远大于实测值;直角双曲线模型、非直角双曲线模型、单指数方程不能拟合黄山栾树存在PSⅡ动力学下调的快速光曲线,只有双指数方程和直角双曲线修正模型可以拟合黄山栾树存在PSⅡ动力学下调的快速光曲线,且可以计算它的饱和光强.综合拟合结果可知,直角双曲线修正模型不仅可以很好地拟合黄山栾树的快速光曲线,而且得到的最大电子传递速率和饱和光强与实测值相符合.此外,通过拟合植物的快速光曲和光响应曲线,还可以判断在饱和光强时它的电子传递速率与碳同化是否同时达到最大值.     

四种野生苔草属植物的耐寒性评价

以采自泰山的白颖苔草、披针叶苔草、青绿苔草和低矮苔草为材料,观察越冬期间田间适应性并测定低温胁迫下抗寒相关的生理指标,计算半致死温度(LT₅₀),利用模糊隶属函数法对耐寒性进行综合评价.结果表明: 4种野生苔草属植物均能安全越冬,且翌春恢复生长良好,年绿期达到260～310 d,越冬期间枯叶率为12%～95%;LT₅₀为-18.65～-11.74 ℃.随着低温胁迫的加剧,4种苔草的丙二醛(MDA)含量、游离脯氨酸(Pro)和可溶性蛋白含量总体呈先上升后下降的趋势,可溶性糖含量呈上升趋势.除披针叶苔草表现为整体呈下降趋势外,其他3种苔草的超氧化物歧化酶(SOD)活性均呈先上升后下降的趋势.耐寒性相对较弱的白颖苔草较早地积累MDA、Pro和可溶性糖.可溶性蛋白含量在低温处理后期达到最大值,且苔草的耐寒性越强其峰值越小.在低温处理初期披针叶苔草SOD活性显著高于其他3种苔草.4种苔草属植物的耐寒性强弱为:披针叶苔草>青绿苔草>低矮苔草>白颖苔草.     

PEG模拟干旱胁迫对糜子幼苗生理特性的影响

以'榆糜1号'和'榆糜3号'为试验材料,采用PEG模拟水分胁迫方法,研究了干旱胁迫对糜子幼苗生理生化特性的影响.结果显示,(1)2品种幼苗叶片的细胞电解质外渗率、叶片的MDA含量、游离脯氨酸含量和可溶性糖含量均在胁迫2 d后逐渐上升,但保护酶SOD和POD的活性均呈先升高后降低的变化趋势,2品种幼苗在不同强度PEG胁迫下总体变化趋势基本一致,且各胁迫处理间差异显著(P<0.05).(2)2品种在相同处理下差异显著(P<0.05),其中,10%～30 0A PEG胁迫8 d时,'榆糜3号'比'榆糜1号'的细胞电解质外渗率、叶片的MDA含量增加幅度小,而游离脯氨酸含量和可溶性糖含量增加幅度较大,但保护酶SOD和POD的活性下降幅度较小,说明相同渗透胁迫下'榆糜1号'比'榆糜3号'叶片的细胞膜透性增加幅度大,但渗透调节物质增加较少,细胞膜系统受干旱伤害会更大,其抗旱性相对较弱.综合各项生理指标的分析认为,'榆糜3号'具有较强的抗旱能力.     

柏木根系分泌物对栾树细根形态及N、P含量的影响

为研究混交过程中柏木根系分泌物对栾树细根生长的影响,以一年生栾树盆栽幼苗为研究对象,通过施加1株、2株、4株、8株4个浓度柏木根系分泌物(分别记为G1、G2、G4、G8)于栾树盆栽中,探讨柏木根系分泌物对栾树幼苗1～5级细根形态及N、P含量的影响。结果表明:(1)栾树细根直径随根序的增加而增大,施加根系分泌物显著减小了1～2级细根的直径(P0.05);细根比根长、比表面积均随根序的增加而减小,施加根系分泌物显著增大了1～2级细根的比根长及比表面积(P0.05);随根系分泌物施加浓度的提高,栾树比根长及比表面积先增大,而直径先减小,然后均趋于平缓波动的态势。(2)栾树细根N、P含量均随根序的增加而减小,而N/P在根序间的变化不显著;施加柏木根系分泌物显著增大了栾树1～2级细根的N、P含量(P0.05),但减小了1～5级细根的N/P;随根系分泌物施加浓度的提高,栾树细根P含量增大,N/P减小,而N含量先增加后呈现平缓变化的趋势。(3)栾树细根N、P含量均与其比根长、比表面积和直径等形态特征之间呈显著的相关关系(P0.05)。研究发现,柏木根系分泌物可改善土壤养分的有效性,从而缓解栾树植株的缺P症状,细根通过调整其形态以提高养分利用效率;柏木根系分泌物主要影响栾树1～2级细根的形态及N、P含量;4株柏木根系分泌物的剂量更有利于栾树根系的生长。     

Defensive traits of savanna trees – the role of shoot exposure to browsers

To investigate patterns of plant defence, a study was conducted on 13 tree species in Botswana. We tested the hypotheses that (1) shoots on small, young trees are more defended than shoots at the same height on tall, mature individuals and (2) shoots within browsing height are more defended than shoots above the reach of browsers, on mature trees. Plant traits studied were total phenolics, tannin activity, nitrogen (N), acid-detergent fibre (ADF), and degree of spinescence (in three species). We found some support for the first hypothesis. Overall young trees had a significantly higher concentration of total phenolics than mature trees and on species level these differences were significant for three of the 13 species. However, we found no differences in tannin activity, spinescence or ADF concentration between young and mature trees, and four species had higher levels of N in young trees, suggesting higher overall palatability. Contrary to our second hypothesis, shoots within browsing height were less chemically defended (total phenolics and tannin activity) than shoots above browsing height in six of 13 species. Two species had less ADF in lower shoots, and no significant differences were found in N or spinescence for any species. This study included a broad range of tree species at two sites and the results indicate that general theories of plant defence, originating from boreal and northern temperate forests, cannot be simply applied to savanna ecosystems.     

Biomass partitioning and leaf N,P - stoichiometry: comparisons between tree and herbaceous current-year shoots

We compare the biomass partitioning patterns and the nitrogen/phosphorus (N,P) stoichiometry of the current-year shoots of tree and herbaceous species and ask whether they scale in the same ways. Our analyses indicate that few statistically significant differences exist between the shoot biomass partitioning patterns of the two functional species-groups. In contrast, statistically significant N,P - stoichiometric differences exist between the two functional groups. Across all species, dry leaf mass scales nearly as the square of basal stem diameter and isometrically with respect to dry stem mass. However, total leaf N scales as the 1.37-power and as the 1.09-power of total leaf P across herbaceous and tree shoots, respectively. Therefore, tree shoots can be viewed as populations of herbs elevated by their older, woody herbaceous cohorts. However, tree leaf stoichiometry cannot be modelled in terms of herbaceous N,P - leaf stoichiometry.     

Variation in crown light utilization characteristics among tropical canopy trees

BACKGROUND AND AIMS: Light extinction through crowns of canopy trees determines light availability at lower levels within forests. The goal of this paper is the exploration of foliage distribution and light extinction in crowns of five canopy tree species in relation to their shoot architecture, leaf traits (mean leaf angle, life span, photosynthetic characteristics) and successional status (from pioneers to persistent). METHODS: Light extinction was examined at three hierarchical levels of foliage organization, the whole crown, the outermost canopy and the individual shoots, in a tropical moist forest with direct canopy access with a tower crane. Photon flux density and cumulative leaf area index (LAI) were measured at intervals of 0.25-1 m along multiple vertical transects through three to five mature tree crowns of each species to estimate light extinction coefficients (K). RESULTS: Cecropia longipes, a pioneer species with the shortest leaf life span, had crown LAI <0.5. Among the remaining four species, crown LAI ranged from 2 to 8, and species with orthotropic terminal shoots exhibited lower light extinction coefficients (0.35) than those with plagiotropic shoots (0.53-0.80). Within each type, later successional species exhibited greater maximum LAI and total light extinction. A dense layer of leaves at the outermost crown of a late successional species resulted in an average light extinction of 61% within 0.5 m from the surface. In late successional species, leaf position within individual shoots does not predict the light availability at the individual leaf surface, which may explain their slow decline of photosynthetic capacity with leaf age and weak differentiation of sun and shade leaves. CONCLUSION: Later-successional tree crowns, especially those with orthotropic branches, exhibit lower light extinction coefficients, but greater total LAI and total light extinction, which contribute to their efficient use of light and competitive dominance.     

Rhamnaceae with multiple lateral buds: an architectural analysis

TOURN, G. M., TORTOSA, R. D. & MEDAN, D., 1992. Rhamnaceae with multiple lateral buds: an architectural analysis. A study was made of the morphology and architecture of three species of Rhamnaceae (Ziziphusjujuba, Zjziphus mistol and Paliurus spina-Christi) with multiple lateral buds. The developmental potential of individual meristems of bud complexes was studied and different kinds of shoots were recognized: vegetative long shoots (dominant and subordinate), flowering branches, short shoots and thorn-tipped branchlets. According to the different orders of branching and the patterns of growth, the architectural model for every species was determined. The architecture of the three species does not conform to that of known tree models. Ziziphus mistol and Paliurus spina-Christi have an architecture intermediate between Attim's and Roux's models; Ziziphusjujuba results in a combination of Koriba's and Roux's models.     

Common allometric response of open-grown leader shoots to tree height in co-occurring deciduous broadleaved trees

Background and Aims

Morphology of crown shoots changes with tree height. The height of forest trees is usually correlated with the light environment and this makes it difficult to separate the effects of tree size and of light conditions on the morphological plasticity of crown shoots. This paper addresses the tree-height dependence of shoot traits under full-light conditions where a tree crown is not shaded by other crowns.

Methods

Focus is given to relationships between tree height and top-shoot traits, which include the shoot''s leaf-blades and non-leafy mass, its total leaf-blade area and the length and basal diameter of the shoot''s stem. We examine the allometric characteristics of open-grown current-year leader shoots at the tops of forest tree crowns up to 24 m high and quantify their responses to tree height in 13 co-occurring deciduous hardwood species in a cool-temperate forest in northern Japan.

Key Results

Dry mass allocated to leaf blades in a leader shoot increased with tree height in all 13 species. Specific leaf area decreased with tree height. Stem basal area was almost proportional to total leaf area in a leader shoot, where the proportionality constant did not depend on tree height, irrespective of species. Stem length for a given stem diameter decreased with tree height.

Conclusions

In the 13 species observed, height-dependent changes in allometry of leader shoots were convergent. This finding suggests that there is a common functional constraint in tree-height development. Under full-light conditions, leader shoots of tall trees naturally experience more severe water stress than those of short trees. We hypothesize that the height dependence of shoot allometry detected reflects an integrated response to height-associated water stress, which contributes to successful crown expansion and height gain.     

Impact of a gall-inducing aphid on Pistacia atlantica Desf. trees

The impact of gall-inducing aphids on shoot development was analyzed in 900 shoots from 20 pistachio trees, Pistacia atlantica Desf. (Anacardiaceae): 600 in which the axillary—lateral buds were galled by Slavum wertheimae HRL during the previous growth season, and 300 ungalled shoots. Although P. atlantica is a compensating tree, and the aphids do not attack the apical buds, further development of shoots from the apical buds was stopped in 62% of the galled shoots, while only 8.7% of nongalled shoots stopped their growth. Further development was stopped more often on shoots carrying two or more galls than on shoots supporting only one gall. To assess the hypothesis that bud destruction by the aphids explains this pattern, a field experiment was conducted in 140 shoots, distributed across seven trees. One, two or three axillary buds from five shoots of each tree were removed for each treatment, and five other shoots were marked as controls. Only 14 shoots (10%) of the 140 did not develop. The growth of the other shoots was not very different among the treatments. The colonization of the apical shoots, which developed on previously treated shoots, by three other galling aphid species was monitored. Removing lateral buds considerably reduced the establishment of Geoica sp. galls (70% of them colonized control shoots), but weakly influenced Forda riccobonii (Stefani). It also contributed only 5% of the total variance of the distribution of Smynthurodes betae West. The different results of the survey and the experiment show that the impact of S. wertheimae galls on the future growth of shoots from apical buds is more complex than the simple physical destruction of the axillary buds. Handling editor: Graham Stone     

Behavior of current-year shoots as a mechanism to determine the floral sex allocation at the level of individual tree and population in Siberian alder (Alnus hirsuta var. sibirica)

Floral sex allocation (weight of male flower buds over weight of female flower buds) was examined at the levels of current-year shoot, individual tree and population, and the tree individual level and population level floral sex ratio was explained as a consequence of the behavior of current-year shoots in the shoot-level monoecious (flowering current-year shoots have both male and female flowers) species, Siberian alder (Alnus hirsuta var. sibirica). The current-year shoot level floral sex allocation was not size-dependent and not different over years. However, in the year when the reproductive intensity was high, individual tree level floral sex allocation was size-dependent and the population level floral sex allocation was relatively female-biased. The female-biased floral sex allocation at the population level resulted from many gynoecious shoots (current-year shoots which have only female flowers). These results suggest that the floral sex allocation of Siberian alder was controlled not by changing the floral sex allocation of each current-year shoot, but by shifting the sex expression of current-year shoots from shoot-level monoecy to shoot-level gynomonoecy.     

Diversity of flowering and fruiting phenology of trees in a tropical deciduous forest in India

BACKGROUND AND AIMS: In the dry tropics, vegetative phenology varies widely with tree characteristics and soil conditions. The present work aims to document the phenological diversity of flowering and fruiting with reference to leafing events in Indian dry-tropical tree species. METHODS: Nine tree species, including one leaf-exchanging and eight deciduous showing varying leafless periods, were studied. Monthly counts of leaves, flowers and fruits were made on 160 tagged twigs on ten individuals of each species for initiation, completion and duration of different phenological events through two annual cycles. KEY RESULTS: Variation in flowering relative to leaf flushing (which occurred just prior to or during a hot, dry summer) revealed five flowering types: summer flowering (on foliated shoots), rainy-season flowering (on foliated shoots following significant rains), autumn flowering (on shoots with mature leaves), winter flowering (on shoots undergoing leaf fall) and dry-season flowering (on leafless shoots). Duration of the fruiting phenophase was shortest (3-4 months) in dry-season and winter-flowering species, 6-9 months in rainy-and autumn-flowering species, and maximum (11 months) in summer-flowering species. A wide range of time lag (<1 to >8 months) between the start of vegetative (first-leaf flush) and reproductive (first-visible flower) phases was recorded in deciduous species; this time lag was correlated with the extent of the leafless period. A synthesis of available phenological information on 119 Indian tropical trees showed that summer-flowering species were most abundant (56 % of total species) amongst the five types recognized. CONCLUSIONS: The wide diversity of seasonal flowering and fruiting with linkages to leaf flush time and leafless period reflect the fact that variable reproductive and survival strategies evolved in tree species under a monsoonic bioclimate. Flowering periodicity has evolved as an adaptation to an annual leafless period and the time required for the fruit to develop. The direct relationship between leafless period (inverse of growing period) and time lag between onset of vegetative and reproductive phases reflects the partitioning of resource use for supporting these phases. Predominance of summer flowering coupled with summer leaf flushing seems to be a unique adaptation in trees to survive under a strongly seasonal tropical climate.     

干旱区多枝柽柳的生长特性

多枝柽柳是分布最为广泛的柽柳属植物之一。也是维持干旱区荒漠生态系统的关键植物种。本研究运用树轮年代学和树干解析方法。对额济纳地区不同生境条件下多枝柽柳的年轮生长、高生长和地径生长等方面的特征进行初步探讨。多枝柽柳每年形成1个年轮。树盘偏心生长极为普遍．完整树轮大多在10龄以内区域,10龄以外都呈单个或多个不完整年轮生长区。多枝柽柳单枝在1～4年高生长缓慢．4～8龄之间属于快速生长期,10年以上生长速率急剧下降。不同地下水位条件下三组样本径生长年增长速率达到极大值的年龄分别为21、56和74年,水环境条件是影响多枝柽柳径向生长的主要因素。同一年年轮宽度随枝高呈减小趋势。多枝柽柳边材的树轮数一般在3～5轮之间,进入老龄阶段有增加趋势。边材宽度随年龄增长逐渐减小。     

Regeneration strategies of tree species in the laurel forest of Tenerife (The Canary Islands)

The laurel-forest of the Canary Islands is a montane cloud-forest. In order to gain some knowledge on the processes that maintain tree species diversity, we conducted an analysis of three different laurel-forest plots of the Anaga massif (Tenerife), varying in canopy composition but growing under similar environmental conditions. For each plot we recorded basal area of the canopy trees (h<1.30 m), the density of suckers and seedlings (h>1.30 m), as well as seed-bank composition. The plots have similar regeneration composition, which appears to be independent of differences in canopy composition. Laurus azorica is the most common seedling species, whereas Prunus lusitanica is the most abundant species among suckers and basal shoots. Neither Erica arborea nor Myrica faya, the two main canopy trees in one of the plots, were found in any of the stands as seedlings or suckers, despite their existence as viable seeds in the seed-bank. The regeneration composition and the canopy composition in one of the plots is remarkable different, revealing differents dynamics processes in the three plots. The results suggest the existence of three well-defined ecological groups: pioneer (regeneration primarily by seedlings), non-pioneer (regeneration by seedlings and suckers) and remnant species (regeneration primarily by suckers).These three groups and the effect of small scale disturbances (natural and human-induced), could help to understand the maintenance of tree species richness.