L-system-based model of growth of dark coniferous tree species

On the basis of L-systems a mathematical model was designed to describe the growth of a dark coniferous tree. The software models a virtual timber stand composed of single trees and its further development. To eliminate branch crossing of growing trees, the rule forbidding shoot growth into the space already occupied was applied to the model. The model parameters were defined for two dark coniferous species of the southern Sikhote-Alin’ — Jezo spruce (Picea jezoensis) and Khingam fir (Abies nephrolepis). The model describes various modifications of tree crown under the influence of neighbouring trees, height uncertainty of crown starting point, variation of taper and shape of a trunk depending on plantation density, and recovery of normal tree growth after singling. Comparison of the modelled results and empirical observations show that the model succeeds in describing the growth both of single trees and of mixed plantations.     

高CO2浓度对温带三种针叶树光合光响应特性的影响

将长白山地区阔叶红松林中主要针叶树种红松、红皮云杉和长白落叶松的幼苗 ,盆栽于模拟自然光照和人工调节CO2 浓度为 70 0和 40 0 μmol·mol-1的气室内两个生长季 ,在各自的生长环境条件下 ,利用CI 30 1PS便携式CO2 分析系统测定针叶的光合光响应曲线 .结果表明 ,不同树种及同一树种的不同CO2浓度处理间差异明显 .比较饱和净光合速率、暗呼吸、光补偿点、光饱和点、及光能利用率 (QUE)的变化可见 ,长白落叶松为阳性树种 ,其光合作用对高CO2 浓度的适应能力较好 ,红松树种次之 ,阴性树种红皮云杉光合作用对高CO2 浓度适应能力最差 .并初步探讨了供试树种光合生理特性及其演替状况间的联系     

Different photosynthesis-nitrogen relations in deciduous hardwood and evergreen coniferous tree species

Rapidly induced responses can alter host plant suitability for insect growth and survival. The effects of defoliation on the suitability of potted 5-year-old red pine, Pinus resinosa Ait., for the sawfly Neodiprion sertifer (Hymenoptera: Diprionidae), were measured in two experiments. In the first, overall larval growth rate increased on seedlings within 8 days of low (<15%) defoliation. Suitability varied among larval age groups: defoliation increased the performance of older larvae, but not that of young larvae. In the second experiment, larval survival and weight varied non-linearly with defoliation intensity 8 weeks after treatment. Similar responses were observed following artificial and natural defoliation, and on early- and late-season seedlings. These results suggest that some evergreen conifers can respond rapidly to defoliation injury, and that herbivores may simultaneously acclimate to the induced response as they develop. The relative importance of induced response rates to plant-insect interactions is discussed.     

Vegetation characteristics and eco-hydrological processes in a pristine mire in the Ob River valley (Western Siberia)

Relations between vegetation characteristics and eco-hydrological processes were assessed in a pristine mire in the valley of the Ob River (Western Siberia). Along a transect from the terrace scarp to the river, field data were collected on vegetation composition, peat stratigraphy, peat chemistry, hydrology and hydrochemistry. Based on floristic composition, eight vegetation communities were distinguished. Hydraulic head measurements were used to obtain an indication of groundwater flow directions. The water balance of the mire was calculated with a two-dimensional steady-state numerical groundwater model. Water types were defined based on cluster analysis of hydrochemical data. The results revealed that the dominant hydrological factor in the Ob mire is the discharge of groundwater, which supplies about threefold more water than net precipitation. Although the discharge flux decreases with increasing distance from the terrace scarp, high water levels and a “groundwater-like” mire water composition were observed in the major part of the study site. Precipitation and river water play only a minor role. Despite dilution of discharging groundwater with rainwater, spatial differences in pH and solute concentrations of the surficial mire water are small and not reflected in the vegetation composition. Although small amounts of silt and clay were found in the peat in the proximity of the river, indicating the occurrence of river floods in former times, no river-flood zone could be recognized based on hydrochemical characteristics or vegetation composition. A comparison of the Ob mire with well-studied and near-natural mires in the Biebrza River valley (Poland) revealed substantial differences in both vegetation characteristics and the intensity and spatial pattern of eco-hydrological processes. Differences in the origin and ratios of water fluxes as well as a dissimilar land use history would seem to be key factors explaining the differences observed.     

干热河谷主要造林树种气体交换特性的坡位效应

植物光合与水分生理特征是植物逆境适应能力评价的重要参考指标.极端生境下,坡位的选择有时成为造林成败的关键.探讨了元谋金沙江干热河谷9个主要造林树种光合与蒸腾作用在不同坡位间的空间差异及干热季向湿润季转换的时序差异.结果表明,低的坡位有助于树种维持相对高的净光合速率,且树种不同,由坡位引起的光合增益效应亦具有较大差别;低坡位的光合增益效应在干热季更为明显,而在湿润季,干热胁迫解除,低坡位的光合增益效应具有较大程度的降低;在不同坡位间发生的光合限制主要受非气孔因素主导.无论在干热季或湿润季,与净光合速率的变化情形一致,低的坡位均促进了树种的蒸腾速率.水分利用效率受坡位的影响较为复杂,因树种、季节而异.     

Seasonal changes in the Modulus of Elasticity of living branches of three coniferous species

The seasonal changes in the Modulus of Elasticity (E) of living branches ofCryptomeria japonica, Chamaecyparis obtusa andLarix leptolepis were investigated over a period of 1 year by means of a quick and non-destructive method previously introduced by the authors. Two sample trees were used for each species and 12 branches were selected from each tree. Readings of the experiments began in summer 1992 and were successively conducted in autumn 1992, winter 1993, spring 1993 and finally in summer 1993. Our investigations revealed that meanE values increased in cold seasons and decreased in warm or hot seasons. Mean values ofE estimated in summer (1993) were relatively close to those estimated in summer 1992 indicating that any changes that occurred were the direct result of the environmental factors prevailing in the intervening seasons. Extremely high meanE values were measured when the branches were in a frozen state in winter; 69.4%, 29.9% and 24.6% higher than the previous summer for branches ofCryptomeria japonica, Chamaecyparis obtusa andLarix leptolepis, respectively. This sharp increase over the initialE values measured in summer 1992 was quite likely due to the freezing effect of rime on the branches.     

小径竹对亚高山暗针叶林优势 树种林窗更新的影响

在亚高山岷江冷杉林中选取面积≤50m2,50~150m2,>150m2的林窗,每种类型内均包含3种小径竹盖度(≤20%、20%~50%、>50%),共调查林窗9个,并调查包含这3种小径竹盖度的三块林下对照样地,研究了该类森林林窗更新与小径竹生长的关系。结果表明:(1)无论林窗大小,林窗内的更新幼苗数量都比林下的多,林窗更新是岷江冷杉群落更新的主要途径;(2)所选林窗均为发育早期,林窗对更新树种的种类组成和数量的影响主要表现在幼苗上。糙皮桦幼树及幼苗数量随林窗面积的增加而急速增加,它的更新更需要较大的林窗;(3)不同小径竹盖度下幼苗的密度呈现显著性变化,小径竹的生长明显抑制了森林幼苗的更新及填充的进程;(4)华西箭竹的分散程度随林窗面积的增大而降低,而平均高度和基径则有增加的趋势。     

几种针阔叶树种不同光照强度下叶绿素荧光特性的研究

测定研究了油松、新疆杨等7种针阔叶树种不同光照强度下最大量子效率(ΦP)和实际量子效率(PhiPSⅡ)等叶绿素荧光特性的变化规律,进而研究了树木对光照强度适应性。结果表明,ΦP和PhiPSⅡ随光强度增加呈下降趋势,二者的光进程变化呈正相关直线。运用方程获得的量子效率最大点、光进程变化转折点和量子效率最小点,可评价树木光合量子效率的大小和对强光的适应性。依PhiPSⅡ最大值对被试树种光合量子效率排序为沙棘>白榆>新疆杨>白腊>油松>白木千>侧柏;依ΦP光进程变化转折点和量子效率最小点对应的光强度评价被试树木对强光的适应能力排序为新疆杨>白榆>侧柏>白腊>油松>沙棘>白木千,结果与被试树种生态特征基本一致。     

南亚热带气候下三种树木径向生长季节节律研究

用带状测树器对南亚热带气候条件下的落叶树柚木（Ｔｅｃｔｏｎａ ｇｒａｎｄｉｓ Ｌ．ｆ．）、喜树（Ｃａｍｐｔｏｔｈｅｃａ ａｃｕｍｉｎａｔａ Ｄｅｃｎｅ）和常绿树火烧花（Ｍａｙｏｄｅｎｄｒｏｎ ｉｇｅｕｍ Ｋｕｒｚ）１６年生（测定开始时年龄）的立木的径向生长进行了６ａ的测定。研究结果表明,所测立木的年均胸围生长量在１．５～２．５ｃｍ（胸径生长量为０．４８～０．８０ｃｍ）之间,年间有一定的差异。年生长     

Comparative phylogeography of three common Neotropical tree species

Aim To determine spatial and temporal commonalities in patterns of chloroplast DNA (cpDNA) variation in three widespread Neotropical tree species. We examine whether patterns of genetic variation are more consistent with Pliocene or Pleistocene divergence. Location Central American forests, located in El Salvador, Nicaragua, Costa Rica and Panama. Methods We collected sequences from two cpDNA loci from c. 30 locations for each of three species –Bursera simaruba (Burseraceae; n = 278), Brosimum alicastrum (Moraceae; n = 210) and Ficus insipida (Moraceae; n = 222) – and additionally sequenced one nuclear locus for Bursera simaruba (n = 45). We used Monmonier’s algorithm to detect genetic barriers between regions. Divergence times between these regions were estimated using coalescent analyses. Results Spatial genetic boundaries were found in similar areas for these species, namely between Costa Rica and Nicaragua for all three species, and between El Salvador and Nicaragua for two species. These boundaries visually coincide with the spatial delimitations of Pliocene islands and previously hypothesized Pleistocene refugia. Divergence time estimates between regions are more consistent with Pleistocene divergence in two of the three species. Main conclusions Our results point to strong commonalities in the spatial locations of genetic boundaries in these three species, despite the complex geological and climatological history of this region, and ecological differences between the species. While spatial genetic boundaries coincide conspicuously with possible Pliocene and Pleistocene barriers to gene flow, we cannot distinguish between the two scenarios because of the strong spatial overlap of both barriers. However, the temporal data tentatively suggest that some of this divergence occurred in the Pleistocene, although limitations in the analysis cannot confirm Pleistocene divergence without external, corroborating data. While we cannot definitively implicate a single historical process as driving patterns of genetic differentiation in all three species, our results represent an initial step towards identifying a common history of Central American tree species.     

Influence of species and abiotic factors on extreme tree ring modulation:

 The influence of biotic (tree species) and abiotic factors (regional climate, altitude and stand aspect) on extreme tree-ring widths is dendroecologically investigated. Negative pointer years are observed when abrupt radial growth reductions (exceeding 40%) occurred synchronously in a given tree population. Pointer year intensity is expected to follow several theoretical models when trees are sampled along ecological gradients in various site conditions. Hypotheses are made about expected patterns of pointer year spatial distribution. They are compared with observed results obtained with Norway spruce [Picea abies (L.) Karst.] and silver fir (Abies alba Mill.) sampled in two French Alpine valleys (Tarentaise and Maurienne) with different regional climates, on two aspects and three altitude levels. Results reveal that extreme years follow expected patterns well. Thus, clear site modulations are observed in 1956 and 1986 (only trees located in Maurienne reacted). Moreover, species differences are observed, with typical cases of single species sensitivity (for spruce, occurring in 1962 and 1992). Abiotic factors such as altitude and aspect also involve clear pointer year patterns, such as narrow rings in 1976 due to summer drought that occurred especially at lower altitudes. However, some observed extreme years sometimes appear to be a combination of two (or three) of these one-factor theoretical models (e.g. 1921 with both lower altitude level and only observed in Tarentaise; 1948 involving both higher altitude and northern slopes). These results demonstrate the consistency of various tree-ring and climate relationships along ecological gradients.     

Pattern of tree species diversity in riparian forest fragments of different widths (SE Brazil)

Width is an essential element of the spatial configuration of riparian forests and may be fundamental in determining their corridor function. In the present study we tested the effect of forest width on floristic structure (tree species composition and diversity) in 15 fragments of riparian forest in an agricultural fragmented landscape of SE Brazil. All these fragments were chosen in a geomorphological homogeneous river reach under similar soil, topographic and human disturbance conditions in order to minimize the influence of these factors. The forest widths considered ranged from 30 to 650 m. The results showed that total species richness and climax species richness were significantly greater when we consider larger fragments, as has been observed in other studies. Nevertheless, species diversity and evenness were not significantly correlated with forest width. The analysis of species composition showed that the narrowest fragments were characterized by species well adapted to temporary flood conditions, while medium and wide fragments showed a composition typical of drier upland areas. Therefore, the effect of forest width on floristic structure appears to be more strongly linked to the effect of river floods in the case of the fragments studied. The existence in riparian corridors of a drier forest, in general richer and more diversified than the annually flooded forest, seems to favor the maintenance of regional species diversity in fragmented landscapes.     

Effects of life history strategies and tree competition on species coexistence in a sub-boreal coniferous forest of Japan

We examined the effects of different life history strategies and tree competition on species coexistence in a northern coniferous forest. We investigated the growth and demography of trees with stems ≥1 cm dbh in a 2-ha study plot in the Taisetsu Mountains of northern Japan. Three species, Abies sachalinensis, Picea jezoensis, and Picea glehnii, were found to be dominant in the forest. A. sachalinensis was the most dominant species in the understory, while the two Picea spp. were more abundant in the larger dbh size classes. The turnover rate of A. sachalinensis was about twice that of the Picea spp. The relative growth rate of understory trees in each species did not differ between different canopy conditions (closed canopy or canopy gap). The competitive advantage between A. sachalinensis and P. glehnii switched as they grew from understory (A. sachalinensis superior competitor) to canopy trees (P. glehnii superior competitor). Meanwhile, A. sachalinensis and P. jezoensis exhibited different environmental preferences. We propose that reversal in competitive superiority between different growth stages and trade-off between longevity and turnover are more important factors to promote their coexistence than regeneration niche differentiation related to canopy gaps in this sub-boreal coniferous forest.     

Seasonality and drivers of stem CO2 efflux for four temperate coniferous tree species

Aims Stem CO₂ efflux (E_s) is an important component of annual carbon budget in forest ecosystems, but how biotic and environmental factors regulate seasonal and inter-specific variations in E_s is poorly understood. The objectives of this study were: (1) to compare seasonal dynamics in E_s for four temperate coniferous tree species in northeastern China, including Korean pine (Pinus koraiensis), Korean spruce (Picea koraiensis), Mongolian pine (Pinus sylvestris var. mongolica), and Dahurian larch (Larix gmelinii); and (2) to explore factors driving the inter-specific variability in E_s during the growing and non-growing seasons.
Methods Ten to twelve trees for each tree species were sampled for E_s and stem temperature at 1 cm depth beneath the bark (T_s) measurements in situ with an infrared gas analyzer (LI-6400 IRGA) and a digital thermometer, respectively, from July to October 2013 and March to July 2014. The daily stem circumference increment (S_i), sapwood nitrogen concentration ([N]), and related environmental factors were monitored simultaneously.
Important findings The temporal variation in E_s for the four tree species overall followed the changes in T_s throughout the study period, with the maxima occurring in the summer months (late May to early July) characterized by higher temperature and more rapid stem growth and the minima in spring (late March to April) or autumn (October) having lower temperature. T_s accounted for 42%-91% and 56%-89% of variations in E_s during the growing (May to September) and non-growing (other months) seasons, respectively. Furthermore, apart from T_s, we also found significant regression relationships between E_s and S_i, relative air humidity and [N] during the growing season, but their forms and correlation coefficients were species-dependent. These results indicated that T_s was the dominant environmental factor affecting seasonal variations in E_s, but the magnitude of the effect varied with tree species and growth rhythm. Mean E_s for each of the four tree species was significantly higher in the growing season than in the non-growing season, whereas within the season there were also significant differences in mean E_s among the tree species (all p < 0.05). The temperature sensitivity of E_s (Q₁₀ value) did not differ significantly among the tree species during the growing season, ranging from 1.64 for Dahurian larch to 2.09 for Mongolian pine, but did differ during the non-growing season which varied from 1.80 for Korean pine to 3.14 for Dahurian larch. Moreover, Korean spruce, Mongolian pine and Dahurian larch had significantly greater Q₁₀ values in the non-growing season than in the growing season (p < 0.05). These findings suggested that the differences of the response of E_s to temperature change for different tree species were mainly from the non-growing season. Because the seasonality and inter-specific variability in E_s for these temperate coniferous tree species were primarily controlled by multiple factors such as temperature, we conclude that using a single annual temperature response curve to estimate the annual E_s may lead to more uncertainty.     

Latitudinal gradients of coniferous tree species,vegetation, and climate in the Sierran-Cascade axis of Northern California

Latitudinal gradients of tree species composition along the Sierran/Cascade axis in northern California were explored by comparing forests of Lassen Volcanic and Yosemite National Parks, USA. A calibration procedure based on canonical correspondence analysis predicted a mean rate of elevational displacement of 172.1 m/° latitude for Lassen sites in Yosemite. This is a steep latitudinal gradient compared with other temperate uplands (which average around 100 m/⁰ latitude), but it corresponds with the magnitude of the July mean temperature gradient (143 m/⁰ latitude) and the annual precipitation gradient (230 m/⁰ latitude). Elevational displacement of basal-area weighted species means showed considerable variation. The range for montane species was 20–153 m/⁰ latitude; for subalpine species the range was 142–305 m/⁰ latitude. This disparity is related to differential temperature lapse rates between regions and is reinforced by contrasting biogeographic affinities of montane vs. subalpine species. Whereas it is uniformly hot and dry during the growing season at lower elevations in both regions, growing seasons in the subalpine zone are significantly warmer and drier (at comparable elevations) in Yosemite, the more southerly locale. Furthermore, montane species are principally of Sierran affinity, whereas subalpine are primarily of Pacific Northwestern affinity.     

桉树与针叶树、阔叶树生理生化指标季节变化的比较

该文对广西桂林灵田乡桉树、针叶树和阔叶树生理生化季节变化进行了比较研究。结果表明：桉树与其它4个针阔叶树种的生理生化指标因季节更替而呈现不同的变化规律,其中5个树种叶片的比叶面积是在夏季最高、冬季最低,其均值依次为桉树>红锥>黧蒴栲>杉木>马尾松;叶片叶绿素含量为夏季>秋季>春季>冬季,总叶绿素含量四季平均值为桉树>黧蒴栲>红锥>杉木>马尾松;叶片可溶性糖含量的季节变化为夏季>春季>冬季>秋季,桉树的平均可溶性糖最高;叶片蛋白质含量都在春季最高、夏季最低,阔叶树种的蛋白质含量显著高于针叶树种,桉树的平均蛋白质含量最高;叶片硝酸还原酶活性顺序为夏季>春季>秋季>冬季,桉树的平均硝酸还原酶活性最高。综上所述,在自然生长环境下,这5个树种的生理生化等指标对季节的响应机制不同,但桉树的生理指标大于其他几个树种。这反映了人工种植的桉树具有高生产力和生长优势。     

Spatial structure of zooperiphyton from the Ob River

Data on the qualitative and quantitative composition of zooperiphyton in the middle and lower reaches of the Ob River are reported, revealing the basic factors affecting its growth. Along most of the river, the zooperiphyton forms a continuum, which is disturbed at sites exposed to pollution. It is found that communities dominated by caddisworms prevail over most of the river; a decrease in the river stream velocity causes a change in the communities, with the replacement of Trichoptera by gastropod communities.     

Hydraulic conductivity of branch junctions in three temperate tree species

Summary Hydraulic conductivities were measured in branch junctions and in the proximal segments of Quercus velutina Lam., Acer saccharum Marsh., and Tsuga canadensis (L.) Carr. In all three species, the basal proximal segment was more conductive than the junction by a factor of 1.1–1.5. There was no consistent pattern for the distal proximal segments, where the conductivities were higher, lower, or the same as the junction. These data are discussed in terms of Martin H. Zimmermann's concept of plant segmentation. It is concluded that junction constrictions to water flow contribute less to plant segmentation than the variation in leaf specific conductivity in the crown of these species.