Interactive effects of leaf age and self-shading on leaf structure,photosynthetic capacity and chlorophyll fluorescence in the rain forest tree,Dryobalanops aromatica

In the tropical canopy tree, Dryobalanops aromatica Gaertn. f., upper-canopy leaves (UL) develop under sunlit conditions but are subjected to self-shading within the crown as they age. In contrast, lower-canopy leaves (LL) are exposed to uniform dim light conditions throughout their life span. By comparing leaf morphology and physiology of UL and LL, variations in leaf characteristics were related to leaf age and self-shading. Mass-based chlorophyll (chl) concentration and the chlorophyll/nitrogen (chl/N) ratio were lower and the chl a/b ratio was higher in UL than in LL. In UL, the chl/N ratio gradually increased and the chl a/b ratio gradually decreased with leaf aging, whereas these ratios remained unchanged with leaf age in LL. The effective quantum yield of photosystem II (PSII) (DeltaF/F(m)') at a given irradiance remained unchanged with leaf age in LL, whereas DeltaF/F(m)' changed with leaf age in UL. These data indicate N reallocation within the leaves from carbon fixation components to light harvesting components and a dynamic regulation of photochemical processes of PSII in response to increased self-shading of UL. Despite the difference in light environment with leaf age between UL and LL, maximum photosynthetic rates and nitrogen-use efficiency decreased with leaf aging in both UL and LL. Constancy in the chl/N ratio with leaf age in LL indicated that the decrease in photosynthetic capacity was caused by effects other than shading, such as leaf aging. We conclude that N reallocation and acclimation of PSII to self-shading occurred even in mature leaves, whereas the change in photosynthetic capacity with leaf age was more conservative.     

基于森林自然度的城市森林状况评价

研究应用层次分析法建立森林自然度评价体系,运用等间距法将城市森林自然度综合指数分为5个等级,基于森林自然度对石家庄市5个行政区以及周边接壤区县森林状况进行评价。评价结果表明：长安区、桥东区、桥西区、新华区、裕华区5个行政区和井陉矿区的自然度等级为5,评价结果为人工森林群落;正定县、栾城县、藁城市的自然度等级为4,评价结果为半人工森林群落;鹿泉市的自然度等级为3,评价结果为远天然森林群落;井陉县的自然度等级为2,评价结果为半天然森林群落;石家庄市森林状况自然度等级总体偏低。最后,根据不同区域的评价结果提出相应的经营措施。     

Assessment of salt tolerance in eucalypts using chlorophyll fluorescence attributes

Chlorophyll fluorescence attributes were investigated for their potential as rapid, non-invasive indices of salt stress in eucalypts. After representative clones of E. camaldulensis and E. urophylla×grandis were subjected to salinity treatments, dark-adapted and quenching attributes did not show consistent responses to salinity stress. The light-adapted attribute F _ds, when measured in a controlled environment, did decline, often before physical symptoms of stress were visible. This value is required for the derivation of the effective quantum yield, and each measurement can be acquired and automatically recorded in a few seconds, permitting the rapid survey of large groups in a propagation facility. Monitoring of plants, that were treated with increasing concentrations of NaCl over time, permitted overall ranking of the responses of groups of clones and seedlings. Usually the data were heteroscedastic, so non-parametric methods of statistical analysis were used, and P0.01 for ascribing significance to differences. Also, following the responses of individuals within clones and provenances showed the method should be useful for the early detection of particularly susceptible or resistant seedlings.     

Influence of stand,site and meteorological variables on the maximum leaf area index of beech,oak and Scots pine

Different multiple linear regression models of maximum leaf area index (LAI_max) based on stand characteristics, site quality, meteorological variables and their combinations were constructed and cross-validated for three economically important tree species in Flanders, Belgium: European beech (Fagus sylvatica L.), Pedunculate oak (Quercus robur L.) and Scots pine (Pinus sylvestris L.). The models were successfully tested on similar datasets of experimental sites across Europe. For each species, ten homogeneous and mature stands were selected, covering the species’ entire stand productivity range based on an a priori site index classification. LAI_max was derived from measurements of leaf area index (LAI) made by means of hemispherical digital photography over the whole growing season (mid-April till end October 2008). Species-specific models of LAI_max for beech and oak were mostly driven by management practice affecting stand characteristics and tree growth. Tree density and dominant height were main predictors for beech, while stand age and tree-ring growth were important in the oak models. Scots pine models were more affected by site quality and meteorological variables. The beech meteorological model showed very good agreement with LAI at several European sites. Scots pine’s stand model predicted well LAI across Europe. Since the species-specific models did not share common predictors, generic models of LAI_max were developed for the 30 studied sites. Dominant height was found to be the best predictor in those generic models. As expected, they showed a lower predictive performance than species-specific ones.     

林地和林木评价

文中说明林地和林木评价结果具体体现为林价，讨论了实施林价的目的及评估方法，同时指出其计算内容应包括营林经营总投人及利息、林木年数、利润、损失、税金、级差地租、树种价差等项目。     

Estimation of leaf color variances of Cotinus coggygria based on geographic and environmental variables

Capturing leaf color variances over space is important for diagnosing plant nutrient and health status,estimating water availability as well as improving ornamental and tourism values of plants.In this study,leaf color variances of the Eurasian smoke tree,Cotinus coggygria were estimated based on geographic and climate variables in a shrub community using generalized elastic net(GELnet) and support vector machine(SVM) algorithms.Results reveal that leaf color varied over space,and the variances were the result of geography due to its effect on solar radiation,temperature,illumination and moisture of the shrub environment,whereas the influence of climate were not obvious.The SVM and GELnet algorithm models were similar estimating leaf color indices based on geographic variables,and demonstrates that both techniques have the potential to estimate leaf color variances of C.coggygria in a shrubbery with a complex geographical environment in the absence of human activity.     

Determinants of drought effects on crown condition and their relationship with depletion of carbon reserves in a Mediterranean holm oak forest

Severe droughts may increase physiological stress on long-lived woody vegetation, occasionally leading to rapid defoliation and progressive increase in mortality of overstorey trees. Over the last few years, episodes of drought-induced tree dieback have been documented in a variety of woodlands and forests around the world. However, the factors determining tree survival and subsequent recovery are still poorly understood, especially in resprouter species. We have studied the effects of a single drought episode on crown condition in a holm oak (Quercus ilex L.) forest located in NE Spain 7 years after the drought event. Generalized linear models were used to study the environmental correlates of forest crown condition 7 years after the drought event. Additionally, we evaluated the association between crown condition and the carbon and nutrient reserves stored in lignotubers 7 years after the drought. Our study reveals the multifactor nature of a drought-driven forest dieback in which soil depth and the characteristics of individual trees, particularly their number of stems, determined a complex spatial pattern of tree-level responses. This dieback was associated with a depletion of the carbon reserves in lignotubers 7 years after the episode, representing a reduction of up to 60% in highly drought-damaged trees. Interestingly, in the absence of new acute droughts, successive surveys in 2007-11 showed a direct association between carbon reserves depletion and further deterioration of crown condition. More frequent droughts, as predicted by climate change projections, may lead to a progressive depletion of carbon reserves and to a loss of resilience in Mediterranean resprouter species.     

Cadmium and lead effects on chlorophyll fluorescence,chlorophyll pigments and proline of Robinia pseudoacacia

Heavy metal contamination is one of the most important abiotic stresses affecting physiological activities of plants.We investigated the effects of cadmium(Cd) and lead(Pb) on chlorophyll fluorescence(Fv/Fm,Fo,and Fm),photosynthetic pigments(chlorophyll a and b),and proline in one-year-old seedlings of Robinia pseudoacacia.The seedlings were treated twice over a period of 10 days with Cd and Pb at concentrations of 0,250,500,1000 and2000 mg L-1.Saline solution containing Cd and Pb was sprayed on the leaves.Chlorophyll and proline contents were measured after 10 days.Chlorophyll fluorescence of R.pseudoacacia was affected slightly by high concentrations(1000,2000 mg L-1) of Cd and Pb.Chlorophyll a and a/b increased at 1000 and 2000 mg L-1of Cd and proline content of leaves was similar in all treatments of Cd and Pb.Our results indicated that photosynthetic sensitivity of R.pseudoacacia to Cd and Pb contamination was weak.Photosystem II chlorophyll pigments were not damaged by Pb and Cd stress.We conclude that chlorophyll fluorescence along with chlorophyll and proline contents are useful indicators of Cd and Pb stresses in R.pseudoacacia which widely planted in urban polluted regions in Iran.     

基于哑变量的湿地松林分断面积生长模型

[目的]为更好地估测福州市湿地松人工林林分断面积生长情况,同时为湿地松人工林的经营提供参考依据.[方法]基于样地调查数据选用理查德方程、逻辑斯蒂、Mitscherlich和Schumacher等基础模型,引入优势木平均高和年龄因子为自变量并将林分密度指数作为密度指标加入到基础断面积模型中.在最优基础模型中引入哑变量,建...     

Grazing effects on the sustainability of an oak coppice forest

In Greece, deciduous oak forests usually provide both, wood production and grazing of understory vegetation. Grazing as a management tool was assayed in a deciduous oak coppice forest of 2000 ha under conversion during the management period of 1991–2005 in Central Macedonia, Greece. In this forest, 1340 cows and 3880 goats were grazing from May to October along the years. The impact of grazing pressure on forest growth was related to the difference of the overall wood stock in two sampling times conducted during the management period of 1991 and 2005. Three grazing pressures were distinguished in the forest: heavy, moderate and light. The moderate grazing improved tree growth and provided significant wood production during the management period. It has also resulted in a sustainable production of herbage and browse in the understory, supporting the maintenance of the livestock. It seems that the conversion of a deciduous oak coppice forest to a high forest along with livestock grazing in the understory is a very efficient management scheme for sustainable production in such a forest.     

Physiological and phenological responses of oak seedlings to oak forest soil in the absence of trees

Established trees influence the growth and physiology of seedlings by altering above- and belowground conditions; however, tree influences on seedling physiology via belowground interactions are not well understood. We used soil transfers to an open field to examine the belowground influences of a Quercus ellipsoidalis E.J.Hill dominated forest on Q. ellipsoidalis seedling mycorrhizal infection, nutrient uptake, growth and photosynthesis over three years. After two years, seedlings planted with large quantities of forest soil (HF treatment) had greater leaf mass and foliar N concentrations than seedlings receiving smaller quantities of forest soil (LF) and control treatments. Mycorrhizal infection was greater in the HF treatment after one year compared with the LF and control treatments, with a positive correlation of foliar N and mycorrhizal infection in Year 2. There were marked effects of treatments on seedling spring phenology with HF seedlings breaking bud up to 17 days earlier than seedlings in the other treatments. The HF seedlings also had more rapid leaf expansion and larger leaves, and an increase in net photosynthetic rates. These results highlight complex linkages between above- and belowground physiology: forest soil had substantial effects on seedling physiology, including traits such as phenology that have previously been considered to be under aboveground control. Belowground influences of trees on conspecific seedlings may play a critical role in early seedling establishment.     

Effects of shade on morphology,chlorophyll concentration,and chlorophyll fluorescence of four Pacific Northwest conifer species

Four species of Pacific Northwestconifer seedlings (ponderosa pine [Pinusponderosa Dougl. ex Laws.], Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco], westernredcedar [Thuja plicata Donn ex D. Donn], andwestern hemlock [Tsuga heterophylla (Raf.)Sarg.]) were planted in individual pots and grownunder shade-cloth shelters that provided four levelsof shade (0% [full sunlight], 35%, 55%, and 75%)for approximately 30 weeks. Height growth wasrecorded every 2 weeks. Initial and final seedlingmorphology and chlorophyll concentrations weremeasured. Chlorophyll fluorescence was measuredmonthly. All species responded similarly to shade. Although height growth was greatest under 75% shadeand least in 0% shade, total biomass production wassignificantly lower and shoot:root ratio significantlyhigher in 75% shade than in 0% shade. As thetreatment shade level increased from 0% to 75%,F_v/F_m was significantly lower whilechlorophyll concentrations were significantly higher. These results indicate that photochemical efficiencyof all four species was lower under higher shade. Morphological and physiological responses differedgreatly among species and corresponded with theirdegree of shade tolerance.     

石栎、青冈栎和杉木混交林分的空间结构

为了弄清优质林分的结构特征,应用传统林分结构因子分析方法,配合混交度、角尺度、大小比数3个林分空间结构参数,分析了位于江苏宜兴近郊的自然保护区内宜兴小黑沟石栎、青冈栎、杉木混交林的空间结构特征。结果表明:石栎、青冈栎、杉木混交林物种丰富度较高,乔木层共出现9个树种,径级结构分布连续,群落垂直结构特征明显,可分为3个林层;林分平均混交度为0.516,处于强度混交状态;林分平均角尺度为0.482,属于随机分布;林分平均大小比数为0.482,有超过40%的林木处于优势状态;石栎、青冈栎和杉木种群优势度明显,群落暂时处于相对稳定状态。     

Spatial prediction of forest stand variables

This study aims at the development of a model to predict forest stand variables in management units (stands) from sample plot inventory data. For this purpose we apply a non-parametric most similar neighbour (MSN) approach. The study area is the municipal forest of Waldkirch, 13 km north-east of Freiburg, Germany, which comprises 328 forest stands and 834 sample plots. Low-resolution laser scanning data, classification variables as well rough estimations from the forest management planning serve as auxiliary variables. In order to avoid common problems of k-NN-approaches caused by asymmetry at the boundaries of the regression spaces and distorted distributions, forest stands are tessellated into subunits with an area approximately equivalent to an inventory sample plot. For each subunit only the one nearest neighbour is consulted. Predictions for target variables in stands are obtained by averaging the predictions for all subunits. After formulating a random parameter model with variance components, we calibrate the prior predictions by means of sample plot data within the forest stands via BLUPs (best linear unbiased predictors). Based on bootstrap simulations, prediction errors for most management units finally prove to be smaller than the design-based sampling error of the mean. The calibration approach shows superiority compared with pure non-parametric MSN predictions.     

Area-level analysis of forest inventory variables

Small-area estimation is a subject area of growing importance in forest inventories. Modelling the link between a study variable Y and auxiliary variables X—in pursuit of an improved accuracy in estimators—is typically done at the level of a sampling unit. However, for various reasons, it may only be possible to formulate a linking model at the level of an area of interest (AOI). Area-level models and their potential have rarely been explored in forestry. This study demonstrates, with data (Y = stem volume per ha) from four actual inventories aided by aerial laser scanner data (3 cases) or photogrammetric point clouds (1 case), application of three distinct models representing the currency of area-level modelling. The studied AOIs varied in size from forest management units to forest districts, and municipalities. The variance explained by X declined sharply with the average size of an AOI. In comparison with a direct estimate mean of Y in an AOI, all three models achieved practically important reduction in the relative root-mean-squared error of an AOI mean. In terms of the reduction in mean-squared errors, a model with a spatial location effect was overall most attractive. We recommend the pursuit of a spatial model component in area-level modelling as promising within the context of a forest inventory.     

Solute accumulation of chestnut oak and dogwood leaves in response to throughfall manipulation of an upland oak forest

To determine the biochemical basis of osmotic adjustment, seasonal and treatment differences in foliar water- soluble organic solutes and inorganic ions were investigated for two hardwood species that exhibited osmotic adjustment in a Throughfall Displacement Experiment at the Walker Branch Watershed near Oak Ridge, Tennessee. Leaf samples of overstory and understory chestnut oak (Quercus prinus L.) and understory dogwood (Cornus florida L.) were collected during the 1994 (wet) and 1995 (dry) growing seasons from each of three treatments: dry (-33% throughfall), ambient (control) and wet (+33% throughfall). Foliar soluble carbohydrates and organic acids were measured by gas chromatography-mass spectrometry. During May 1994, when the demand for sucrose was greatest, dogwood accumulated small amounts of glucose, quinic acid and Mg2+, offsetting a decline in nitrate concentration. As the mild drought continued and tree growth slowed, there was a significant accumulation of sucrose in dogwood in the dry treatment in June, and a trend toward increased K+. In overstory chestnut oak in the dry treatment over the same period, there were significant accumulations of fructose, glucose and K+, and a trend toward increased quinic acid accumulation. Sucrose did not become a key osmotically active compound in chestnut oak until August 1994. In 1995, with the exception of understory chestnut oak, there was no accumulation of K+ in either species. During the severe drought of 1995, monosaccharides, particularly glucose and fructose, accounted for most of the osmotic adjustment in both species. Among solutes, glucose constituted the largest accumulation in dogwood in the dry treatment in August 1995, followed by fructose and sucrose. There was only a moderate increase in solutes in chestnut oak trees in 1995, with fructose and glucose constituting over 50% of the predicted solute accumulation in July. Both species accumulated a wider array of solutes during the dry year than during the wet year, but treatment differences in solute accumulation in chestnut oak were partially limited by drought. The greater dehydration tolerance of chestnut oak than dogwood was evident in the higher baseline concentrations of organic solutes and the greater array of solutes accumulated in response to drought.     

Effects of oak root pruning in forest nurseries on potential pathogen infections

Despite the general practice of root pruning, little is known about the potential impact of reducing shoot/root systems of oak seedlings in this way on their future susceptibility to pathogens, for example Cylindrocarpon spp., Fusarium spp., Ilyonectria spp., Pythium spp. Phytophthora spp. or Rhizoctonia spp. In this study, root‐pruned and non‐pruned seedlings of Quercus robur grown under controlled conditions were inoculated with aggressive and less‐aggressive pathogens. Results indicated, in contrast to our initial assumption, that pathogens significantly reduced lateral root biomass more in non‐pruned seedlings, the extent of the response depending on the pathogens species. In response to pathogen pressure, pruned seedlings tended to attain a higher dry stem mass fraction, but lower dry leaf mass fraction. Pathogens also suppressed leaf mass in total root dry mass fraction (dry leaf mass/total root dry mass ratio, in g × g^?1) more in pruned than in non‐pruned seedlings. These results suggest differences in growth between non‐pruned and pruned seedlings in response to pathogen stress. In nurseries, root pruning of oak trees may enhance the reduction in leaf mass in lateral roots mass fraction resulting from pathogen infections, which may decrease seedling quality. It is therefore important to ensure a low level of inoculum of soil‐borne pathogens to minimize the risk of seedling infection.     

Seasonal variations in leaf area index,leaf chlorophyll,and water content; scaling-up to estimate fAPAR and carbon balance in a multilayer,multispecies temperate forest

Seasonal differences in phenology between coniferous and deciduous tree species need to be considered when developing models to estimate CO(2) exchange in temperate forest ecosystems. Because seasonal variations in CO(2) flux in temperate forests are closely correlated with plant phenology, we quantified the phenology of forest species in a multilayered forest with patches of Scots pine (Pinus sylvestris L.) and oak (Quercus robur L.) in Brasschaat, Belgium. A scaling-up modeling approach was developed to simulate reflectance at the leaf and canopy scales over a one-year cycle. Chlorophyll concentration, water content, specific leaf area and leaf area index of the forest species were measured throughout an entire year (1997). Scaling-up from the leaf to canopy was achieved by linking the PROSPECT and SAIL models. The result is the annual progression of the fraction of absorbed photosynthetically active radiation (fAPAR) in a 1 km(2) forest area, which can be directly related to high-resolution, remotely sensed data.     

Decomposition of needle/leaf litter from Scots pine, black cherry, common oak and European beech at a conurbation forest site

Litter decomposition was studied for 2 years in a mixed forest serving as a water protection area (Rhine-Neckar conurbation, SW Germany). Two experiments differing in initial dry weight equivalent in litterbags were set up: one to compare decomposition of European beech leaves (Fagus sylvatica) with common oak leaves (Quercus robur), and the other comparing decomposition of Scots pine needles (Pinus sylvestris) with black cherry leaves (Prunus serotina Ehrh.), respectively. Mass losses were greater for oak litter than for beech (75.0 versus 34.6%), and for cherry litter than for pine (94.6 versus 68.3%). In both experiments, a strong initial loss of soluble compounds occurred. The changes in litter N and P concentrations and the decrease in C-to-N ratio coincided with changes in residual mass. However, neither tannin and phenolic concentrations nor NMR could explain the pronounced variation in mass loss after 2 years. Differences in litter palatability and toughness, nutrient contents and other organic compounds may be responsible for the considerable differences in residual mass between litter types. The fast decay of black cherry leaves appears to play a major role in the present humus dynamics at the studied site. Since black cherry has a high N demand, which is mainly met by root uptake from the forest floor, this species is crucial for internal N cycling at this conurbation forest site. These effects together may significantly contribute to prevent nitrate leaching from the forest ecosystem which is subject to a continuous N deposition on an elevated level.