Evaluation of tree and stand-level growth models using national forest inventory data

Two models, Carbware (CW) and Growfor (GF), of different resolution and based on different frameworks were evaluated in relation to stand-level forecasts of volume and basal area using Ireland’s National Forest Inventory (NFI) data. CW is a distance-independent single-tree model that is based on diameter increment. GF is a stand-level dynamic empirical model that uses the von Bertalanffy–Richards growth equation in a state-space framework. NFI data were used as input to the models, and each model’s projections were compared to NFI data at the next measurement cycle. The NFI is a permanent sampling system with the objective to assess the composition and extent of the forest estate. A subset of the NFI was used in the study, single-species even-aged plots comprising Sitka spruce and lodgepole pine. The accuracy and performance of the CW and GF models were analysed using residual analysis and standard statistical techniques. Results show that both models require improvement, though the study has raised concerns regarding the suitability of the NFI data for this type of investigation.     

湖南省现有森林植被主要树种的碳含量

探讨了湖南省现有森林植被17种树种(杉木、马尾松、湿地松、柏木、乐昌含笑、红花木莲、樟树、桢楠、甜槠、青冈栎、木荷、杜英、山矾、枫香、拟赤杨、杨树、毛竹)各器官的碳含量及其各器官碳含量的算术平均值。结果表明:同一树种不同器官碳含量差异不显著,不同树种各器官碳含量由高至低的排序不完全一致,不同树种同一器官或同一树种不同器官碳含量算术平均值存在一定的差异;针叶树、常绿阔叶树、落叶阔叶树和毛竹各器官碳含量(g·g-1)的变化范围分别为0.491~0.566,0.421~0.549,0.449~0.550,0.470~0.496,各树种种内各器官碳含量算术平均值在0.486~0.551 g·g-1之间变化,柏木最高,毛竹最低;针叶树碳含量高于阔叶树、毛竹,各树种树干碳含量普遍较高于其它各器官,变化范围在0.493~0.556 g·g-1之间,地上部分碳含量普遍高于相应树种的地下部分;17种树种各器官碳含量的算术平均值为0.504 g·g-1。     

Foliage nutrient concentration and lopping time of agroforestry tree species in the Western Himalayan region of India

Tree foliage is a nutrient-rich and important source of green fodder to sustain the livestock during the lean winter period of a season in the low and mid hill regions of Indian Himalaya. Knowledge of the variations in mineral nutrient composition of the foliage during an active growth season helps in determining optimum lopping time to harvest nutrient-rich fodder. Changes in the nutrient concentrations of Albizia stipulata and Ougenia oojeinensis foliage during the annual growth season were studied to find out an optimum lopping time. Two dissimilar trends in variation of nutrients in foliage with the advancement of growth season were observed. These were: (1) depletion/dilution of N, P, K and S and (2) accumulation of Ca, Mg and Na. The depletion was more from October onwards, and accumulation reached to its maximum in November-December. Therefore, the period from October to December, preferably November, can be regarded as optimum lopping time for A. stipulata. For O. oojeinensis, the corresponding time could be September to November, preferably October. Ougenia foliage contained higher concentration of N, P, Ca, Mg, and Na than that of Albizia. This revised version was published online in June 2006 with corrections to the Cover Date. This revised version was published online in June 2006 with corrections to the Cover Date.     

Factors affecting nutrient concentration and stoichiometry of forest trees in Catalonia (NE Spain)

Although some studies have observed significant correlations between latitude and climate gradients and tree leaf nutrient concentration and stoichiometry, others have not. This study examined the nutrient concentrations of tree leaves in 3530 plots of the Catalonian Forest Inventory. Catalonia is a Mediterranean region located in NE Iberian Peninsula. It has a long land-use history and includes the large industrial-urban area of Barcelona but still contains a large forest area (42%). In the forests of Catalonia, leaf nutrient concentration increased and leaf C:nutrient ratios decreased from south to north, which paralleled the increase in MAP (mean annual precipitation) and the decrease in MAT (mean annual temperature), which was expected in a Mediterranean climate where the availability of water is the most limiting factor for plant nutrient uptake. In addition, the availability of water, which influences productivity, was associated with low leaf N:P content ratios, which is consistent with the Growth Rate Hypothesis. At a regional scale, the results support the Soil-Age Hypothesis because the youngest soils in the Pyrenees had the lowest leaf N:P ratios. Furthermore, the type of forest (evergreen, deciduous, or coniferous) explained some of the variation in leaf nutrient concentrations and stoichiometry. Nutrient concentrations were highest in deciduous trees and lowest in coniferous trees. Leaf nutrient concentrations and stoichiometry were mainly correlated with climate, but other factors such as the chemical properties of soil and rock, phylogenetics, and different ecological histories and anthropogenic factors such as pollution, had an effect.     

不同施钾水平对油茶树体生长和林地养分含量的影响

为了确定油茶幼林钾肥最适施用量,从而为油茶的科学施肥提供理论依据,以‘赣无’系列的5年生油茶林分为试验对象,设置了5个钾素水平处理(K0、K1、K2、K3、K4),1个施用复合肥的对照处理(CKFHF)和1个不施肥的处理对照(CK0),就不同施肥处理对油茶树体生长、叶片养分积累和土壤养分含量的影响情况进行了试验、测定与分析。结果表明:施肥均能显著提高油茶树体各生长指标的增幅和叶片及土壤中各种养分的含量;随着施钾水平的提高,油茶树体各生长指标的增幅和叶片中各种养分的含量均随之增加,K3处理的达到最大值,复合肥处理的肥效小于K2处理;随着施钾水平的提高,油茶林地土壤中速效钾和有机质的含量均显著性增加,而土壤中碱解氮和有效磷的含量则随着施钾水平的提高均先减小后增加,K4处理的降到最小值;对油茶叶片中的钾含量、土壤中的速效钾含量与施钾量进行拟合,得出其响应曲线,并确定了对油茶幼树施用钾肥的最适用量范围为317.72~322.25 g/株。     

森林生态系统养分循环的研究

森林具有多功能、多效益的特点,人们对森林经营的要求,不仅是经济效益,随着社会的发展更日益着重于生态效益和社会效益.因此对森林生态系统定位研究的成果,将会为森林经营管理者提供决策的理论基础和最佳的实施方案.如若对系统中各成分和功能过程得到全面的了解,通过系统的计算机模拟可以表示出系统内各成分相互作用以及整个系统对不同干扰、环境污染和经营管理措施的反应,将对实现林业向生态化转变,为森林多效益稳定而永久利用发挥作用.     

The influence of the forest canopy on nutrient cycling

Rates of key soil processes involved in recycling of nutrients in forests are governed by temperature and moisture conditions and by the chemical and physical nature of the litter. The forest canopy influences all of these factors and thus has a large influence on nutrient cycling. The increased availability of nutrients in soil in clearcuts illustrates how the canopy retains nutrients (especially N) on site, both by storing nutrients in foliage and through the steady input of available C in litter. The idea that faster decomposition is responsible for the flush of nitrate in clearcuts has not been supported by experimental evidence. Soil N availability increases in canopy gaps as small as 0.1 ha, so natural disturbances or partial harvesting practices that increase the complexity of the canopy by creating gaps will similarly increase the spatial variability in soil N cycling and availability within the forest. Canopy characteristics affect the amount and composition of leaf litter produced, which largely determines the amount of nutrients to be recycled and the resulting nutrient availability. Although effects of tree species on soil nutrient availability were thought to be brought about largely through differences in the decomposition rate of their foliar litter, recent studies indicate that the effect of tree species can be better predicted from the mass and nutrient content of litter produced, hence total nutrient return, than from litter decay rate. The greater canopy complexity in mixed species forests creates similar heterogeneity in nutritional characteristics of the forest floor. Site differences in slope position, parent material and soil texture lead to variation in species composition and productivity of forests, and thus in the nature and amount of litter produced. Through this positive feedback, the canopy accentuates inherent differences in site fertility.     

张掖市退耕还林树种的选择及配置模式

从张掖市的自然环境、地理位置、气候条件、土质状况、水资源利用等方面着手，结合树木生态学特性、生理适应性以及观赏特性，分析总结出本区域退耕还林的适宜树种及配置模式。     

解析森林、林木与林地

通过对森林、林地、林木概念的分析，明确了这些概念的内涵，对指导林业基础工作提供参考。     

沿海防护林树种适应性测试技术总结

建国以来，蓬莱市在82km长的海岸线上建起了400多hm^2的沿海防护林带。防护林带的主要树种为黑松、刺槐。近几年，由于海水倒灌，气候干旱以及病虫危害等原因，部分海防林出现树木成片枯死现象，使林相整齐的沿海防护林残缺不全，降低了防护效益。因此引进筛选出适应性强，抗病虫危害，具有良好防护性能的林木新品种，对我市甚至整个北方沿海防护林带建设具有十分重要的意义。在省林科院的指导帮助下，自1997年开始，我们从胶南引进了火炬松、刚松、鲁刺11号、鲁刺13号、白蜡等5个林木新品种，在北沟镇聂家村海滩上进行了栽植试验，取得了良好效果，现将情况总结如下.     

Photosynthetic responses of forest understory tree species to long-term exposure to elevated carbon dioxide concentration at the Duke Forest FACE experiment

We examined the photosynthetic responses of four species of saplings growing in the understory of the Duke Forest FACE experiment during the seventh year of exposure to elevated CO2 concentration ([CO2]). Saplings of these same species were measured in the first year of the Duke Forest FACE experiment and at that time showed only seasonal fluctuations in acclimation of photosynthesis to elevated [CO2]. Based on observations from the Duke Forest FACE experiment, we hypothesized that after seven years of exposure to elevated [CO2] significant photosynthetic down-regulation would be observed in these tree species. To test our hypothesis, photosynthetic CO2-response and light-response curves, along with chlorophyll fluorescence, chlorophyll concentration and foliar N were measured twice during the summer of 2003. Exposure to elevated [CO2] continued to increase photosynthesis in all species measured after seven years of treatment with the greatest photosynthetic increase observed near saturating irradiances. In all species, elevated [CO2] increased electron transport efficiency but did not significantly alter carboxylation efficiency. Quantum yield estimated by light curves, chlorophyll concentration, and foliar nitrogen concentrations were unaffected by elevated [CO2]. Contrary to our hypothesis, there is little evidence of progressive N limitation of leaf-level processes in these understory tree species after seven years of exposure to elevated [CO2] in the Duke Forest FACE experiment.     

杨树林地郁闭前林农间作研究

以郁闭前的杨树人工速生林为研究对象,通过林农间作研究,结果表明：林农间作不仅能获得短期经济效益,对林木生长也有明显的促进作用。     

Interaction of nutrient limitation and elevated CO2 concentration on carbon assimilation of a tropical tree seedling (Cedrela odorata)

Carbon assimilation by Cedrela odorata L. (Meliaceae) seedlings was investigated in ambient and elevated CO2 concentrations ([CO2]) for 119 days, using small fumigation chambers. A solution containing macro- and micronutrients was supplied at two rates. The 5% rate (high rate) was designed to avoid nutrient limitation and allow a maximum rate of growth. The 1% rate (low rate) allowed examination of the effect of the nutrient limitation-elevated CO2 interaction on carbon assimilation. Root growth was stimulated by 23% in elevated [CO2] at a high rate of nutrient supply, but this did not lead to a change in the root:shoot ratio. Total biomass did not change at either rate of nutrient supply, despite an increase in relative growth rate at the low nutrient supply rate. Net assimilation rates and relative growth rates were stimulated by the high rate of nutrient addition, irrespective of [CO2]. We used a biochemical model of photosynthesis to investigate assimilation at the leaf level. Maximum rate of electron transport (Jmax) and maximum velocity of carboxylation (Vcmax) did not differ significantly with CO2 treatment, but showed a substantial reduction at the low rate of nutrient supply. Across both CO2 treatments, mean Jmax for seedlings grown at a high rate of nutrient supply was 75 micromol m(-2) s(-1) and mean Vcmax was 27 micromol m(-2) s(-1). The corresponding mean values for seedlings grown at a low rate of nutrient supply were 36 micromol m(-2) s(-1) and 15 micromol m(-2) s(-1), respectively. Concentrations of leaf nitrogen, on a mass basis, were significantly decreased by the low nutrient supply rate, in proportion to the observed decrease in photosynthetic parameters. Chlorophyll and carbohydrate concentrations of leaves were unaffected by growth [CO2]. Because there was no net increase in growth in response to elevated [CO2], despite increased assimilation of carbon at the leaf level, we hypothesize that the rate of respiration of non-photosynthetic organs was increased.     

Performance of eight tree species in the highland Vertisols of central Ethiopia: growth, foliage nutrient concentration and effect on soil chemical properties

The coverage of trees in the highland Vertisol areas of Ethiopia is very scarce. A tree screening trial was conducted from 1997 to 2002 in Ginchi (central Ethiopia) to select fast growing and high biomass producing tree species; evaluate foliage macronutrient concentration of different tree species; and assess effects of trees on soil chemical properties beneath their canopies. Acacia decurrens Willd, A. mearnsii De Wild and Eucalyptus globulus Labill attained the highest height growth at 64 months as compared to other indigenous and exotic species. E. globulus provided better height increment from 24 to 36 and 36 to 64 months than other tree and shrub species. Acacia mearnssi and A. saligna Labill Wendl produced high biomass at 40 and 64 months. Differences between the highest and lowest dry biomass at 12, 40 and 64 months were 1.13, 29.19 and 38.89 kg tree⁻¹, respectively. None of the tree species resulted in a foliage to stem biomass ratio of >0.98 at 40 and 64 months. Sesbania sesban (L.) Merr had high N and P concentrations in its foliages and stems at 12 and 40 months. Total N under Acacia abyssinica Hochst. Ex Benth, A.␣saligna and S. sesban was slightly greater at 40 months than 12 months.     

森林资源动态管理系统中人工林进界木株数模型研究

引起森林资源动态变化的原因主要有两个方面，一是人为活动对森林资源的影响； 二是自然生长与枯损引起资源的消长变化。进界木生长是引起森林资源变化的重要因素之 一，在“温州市森林资源动态管理系统”软件的设计过程中，对南方集体林区人工林的进 二，界木模型进行了研究，提出了适合于浙南山区的进界木株数变化模型。     

Improving the estimate of forest biomass carbon storage by combining two forest inventory systems

Quantifying forest carbon storage and its spatial distribution at regional scales is critical for the creation of greenhouse gases inventories, the evaluation of forest services and carbon-oriented forest management. The plot-based forest inventory (PBFI) and stand-based forest inventory (SBFI) collect extensive information on trees and stands respectively, and together, provide an opportunity to improve the regional estimates of forest carbon. In this study, we applied the SBFI to overcome the spatial extent limits of the PBFI in neighboring plots and improve the regional carbon estimation. We found that the forests in Sichuan Province reserved a total of 624.2?Tg?C in biomass and featured a large spatial heterogeneity, with high values in natural forests and low values in plantations. We found that the solo use of PBFI derived a slightly higher (46.63?Mg?C/ha) estimation on average compared with the integrated method (43.6?Mg?C/ha). However, when considering the spatial distribution, the PBFI generated an overestimation of young forests located between 3000and 4000?m in elevation, and an underestimation in mature forests. The spatially explicit biomass carbon estimation could be helpful in guiding regional forest management and biodiversity conservation.     

Individual growing conditions that affect diameter increment of tree saplings after selection harvesting in a mixed forest in northern Japan

We analyzed temporal patterns in diameter growth of saplings following selection harvesting in an uneven-aged mixed stand dominated by Abies sachalinensis, Acer mono, Quercus crispula, and Betula ermanii in Hokkaido, northern Japan. We examined interspecific differences in growth responses to local growing conditions including harvesting intensity, crowding, stem size, and past duration of the small growth period. Consistent with expectations based on shade tolerance of the species, the age at which the individual reached a diameter at breast height (DBH) of 12.5 cm was highest for A. sachalinensis and lowest for B. ermanii. The interspecific growth differences between saplings that had or had not experienced local harvesting increased gradually for A. sachalinensis and B. ermanii, but peaked at around 4–6 years after harvesting for Q. crispula. Generalized linear mixed model analysis clearly suggested that individual growth conditions required to enhance diameter growth of saplings differed considerably among species. For Q. crispula and B. ermanii, local harvesting intensity was most strongly and positively associated with diameter growth rate, whereas for A. sachalinensis and A. mono, stem size had the strongest negative effect. Abies sachalinensis saplings responded more to surrounding harvesting when they were relatively small, whereas A. mono showed a weak opposite response. The duration of the small growth period before harvesting had negative effect for A. sachalinensis, but not for the other species. Our study indicated that the influence of selection harvesting on growth of shade-tolerant species depends upon pre- and post-harvest growing conditions.     

Adaptation of a modelling strategy to predict the NPP of even-aged forest stands

The assessment of net forest production is important for both scientific and practical purposes. The current paper presents the application of a recently developed strategy to estimate the net primary productivity of an even-aged Mediterranean pine forest (Natural Park of San Rossore, Central Italy). The strategy is based on the use of two models, C-Fix and BIOME-BGC, whose outputs are combined with forest volume data in order to describe the actual status of the ecosystems examined. The accuracy of the simulation is tested against measurements of current annual increment (CAI) derived from a recent forest inventory of the Park. The results of this test indicate that the methodology must be modified to account for the even-aged nature of the study stands. The modification is performed by the analysis of dendrochronological and tree density data, which characterize the temporal volume and CAI evolution of representative forest stands. The modified methodology is capable of taking into account the effect of stand ageing and yielding nearly unbiased estimates of forest CAI.