Comparison of image and rapid field assessments of riparian zone condition in Australian tropical savannas

Suitable methods for measuring and monitoring the condition of riparian environments are being investigated by government agencies responsible for maintaining these environments in Australia. The objective of this work was to compare two riparian condition assessment approaches, the Tropical Rapid Appraisal of Riparian Condition (TRARC) method developed for rapid on-ground assessment of the environmental condition of savanna riparian zones and an image based riparian condition monitoring scheme. Measurements derived from these two approaches were compared and correlated. The sample representativeness of the TRARC method was evaluated and the cost-effectiveness and suitability for multi-temporal analysis of the two approaches were assessed. Two high spatial resolution multi-spectral QuickBird satellite images captured in 2004 and 2005 and coincident field data covering sections of the Daly River in the Northern Territory, Australia were used in this work. Both field and image data were processed to map indicators of riparian zone condition including percentage canopy cover, organic litter on the ground, canopy continuity, tree clearing, bank stability, and flood damage. Spectral vegetation indices, image segmentation, and supervised classification were used to produce riparian health indicator maps. QuickBird image data were used to examine if the spatial distribution of TRARC transects provided a representative sample of ground based estimates of riparian health indicators. Covering approximately 3% of the study area, the sample mean of the TRARC estimates of individual indicators of riparian zone condition were in most cases within 20% of the global mean derived from the whole imaged riparian area. The cost-effectiveness of the image based approach was compared to that of the ground based TRARC method. Results showed that the TRARC method was more cost-effective at spatial scales from 1 km to 200 km of river in relatively homogeneous riparian zones along rivers with only one channel, while image based assessment becomes more feasible at regional scales (200–2000 km of river). A change detection analysis demonstrated that image data can provide detailed information on gradual change, while the TRARC method is less suited for multi-temporal analysis due to the ranked data format, which inhibits precise detection of change. However, results from both methods were considered to complement each other for single date assessment of riparian zones if used at appropriate spatial scales.     

Temporal development of crown condition of beech and oak as a response variable for integrated evaluations

The evaluation uses the longest available time series for beech and oak defoliation in Germany. The data from Hesse, starting from 1984, show a typical pattern: for the first 12 years, a continuous increase in defoliation was observed ranging from an average value of 14% in 1984 to a peak value of 30%. This was followed by a subsequent decrease in the loss of foliage accompanied by a high variability, until the last monitoring in 2003, where an average value of 25% defoliation was observed. For both tree species, the years of trend reversal were identical. The same pattern was observed in the German federal states: Rhineland-Palatinate, North Rhine-Westphalia, and Bavaria. The year of trend reversal was identical in Hesse and Rhineland-Palatinate. In North Rhine-Westphalia, it occurred 1 year earlier and in Bavaria 3 years earlier. Whereas defoliation trends were clearly demonstrated, tree mortality did not appear on a large scale. The sample trees were grouped into four discrete clusters according to their annual defoliation values from 1984 to 2003. In 1996, the clusters represent 15, 25, 35, and 50% defoliation values. Regarding beech in Hesse, there was no overlap in the defoliation curves observed among the different clusters. These four clusters having different degrees of defoliation over the whole time span of 20 years were used for a further detailed statistical analysis. For discrete variables like crown spacing and—in the case of beech—fruit bearing, mosaic plots were applied in order to visualize relations of low dimensional contingency tables, with defoliation trends being used as the response variable. The data show for beech a very clear relation between defoliation and age, relative crown spacing, stand composition, and fruit bearing. Regarding oak, besides age and relative crown spacing, the years with significant appearance of biotic stress factors—leaf eating insects—show a clear relation to trends of defoliation. The statistical model used in this study—logistic regression—allows applying a multinomial response variable and a number of continuous or categorical explanatory variables. With this approach, an iterative optimized selection of effect variables was used to test the relevance of different variables on the defoliation pattern of the same four clusters mentioned above. For this, the variables were grouped in an iterative process with five steps, starting with a few basic variables of tree and site information, and ending with a total of more than 20 variables in the fifth step. The process selects first the variables which are of significance on the defoliation, and calculates the possible errors in the grouping of the different trees to the four clusters. In this analysis of beech, the basic tree and stand variables: age, relative crown spacing, stand composition and fruit bearing proved to be the most relevant group of parameters, with the other variables explaining the variation of defoliation only to a minor extent. More complex model levels do not change any basic selected variables; however, Cation Exchange Capacity (CEC), C/N-ratio, Al- and Ca-proportion of CEC are additionally selected and give a hint of the relevance of soil conditions. Regarding beech, the errors of the statistical model are lower compared to oak.     

北京市十三陵林场森林健康状况及经营对策研究

从十三陵林场森林资源树种单一、结构失调等现状出发,借鉴前期研究成果,建立森林生态系统健康评价体系;结合相关调查数据,对全场40块林班,798块小班,总面积8 504.88hm2的森林资源从小班和林班两个层次进行健康评价。依据此评价结果,提出森林健康经营对策。     

森林生态系统健康评价现状及展望

以森林生态系统健康评价的概念为出发点,从评价层次、评价指标、评价方法和评价标准等方面剖析森林健康评价的关键技术,综述国内外有关森林生态系统健康评价的研究进展,并分析当前研究中存在的问题,如指标体系不够完善、评价方法有待完善、评价标准主观性强、评价结果不准确等。今后森林生态系统健康评价研究的重点应着重于理论探索和方法完善方面,从研究健康机制入手,完善评价指标体系,改进评价的手段、方法和技术,确立不同区域主要森林类型的健康标准,为调控不健康的森林、保持森林健康状态、实现森林生态系统的可持续发展提供理论依据和技术支持。     

美国的森林动态评价模型及其对中国森林健康评价的启示

应用动态模型评价森林健康状况,预测树木或林分的生长与收获,以及在不同立地条件下采用某些特定的营林技术措施后林分的动态变化,一直是森林健康评价及管理的核心问题.当前在美国应用的两个森林动态评价及决策模型SIMPPLLE和MAGIS主要是用来评价当前林分状况、模拟林分发展以及预测不同经营管理方式下林分未来的动态变化状况,通过分析不同决策下森林植被的收获状况,选择最优化的管理措施以及实施措施的时间及地点制定最优化决策.针对现阶段中国森林健康评价中,以建立评价指标体系进行静态评价、缺乏空间信息数据和森林健康经营动态变化规律模型等问题,提出今后应针对中国实际情况开展切合实际的研究,开发出以促进森林健康经营为目的的动态预测模型和决策模型,提高森林健康的预测能力,完善森林健康经营综合评价技术体系.     

以昆虫为指示物种监测和评价森林生态系统健康初探

森林生态系统健康是保证生态系统服务功能的前提, 森林生态系统健康评价方法及指标体系已成为森林生态系统健康研究的核心内容。昆虫是森林生物多样性的重要组成部分, 在森林生态系统主体群落中, 昆虫与植物密切关联。森林害虫胁迫及昆虫多样性变动, 对于评估森林生态系统健康状况具有重要价值。研究显示, 昆虫多样性可应用于对森林生态系统健康的快速评估。     

基于BP神经网络确立森林健康快速评价指标

拟定森林健康快速评价(RAFH)指标,通过对训练样本的模式识别来构建一个BP神经网络,观察其能否收敛,并以测试样本为新的输入项进行模拟,采用误差百分比法、线性回归检验法和Nash-Sutcliffe效率法对模拟值与期望值的吻合程度进行检验,以此验证拟定指标的合理性.结果表明:在隐含层神经元n≥16时,网络能较好地收敛,说明该网络输入项--林分层次结构、病虫害程度和土壤厚度3个指标的训练样本值与目标输出项--森林健康精准评价(PAFH)结果的非线性相关程度高;模拟值与期望值的相对误差均值为-6.140 9%,回归方程斜率为0.968 3,截距为0.049 0,Nash-Sutcliffe效率为0.905 4,均表明二者之间吻合较好.因此,林分层次结构、病虫害程度和土壤厚度可以作为森林健康快速评价(RAFH)的指标.     

基于WebGIS的森林健康评价与区划专家支持系统的设计与实现

为了解决森林经营单位森林健康状况的评价问题,利用综合因子评价法建立了改进的林分级森林健康评价指标体系,并基于ArcGISServer开发了森林健康评价与区划专家支持系统．以八达岭林场为例进行了森林健康评价与区划．结果表明,该系统可辅助实现森林经营单位健康状况判定、区划、出图、查询和统计等功能,并可以根据已有数据自定义评价指标体系及实时生成评价结果．     

中山市常绿针叶林与阔叶林群落结构健康研究

以植物群系为评价单元,通过相关性检验和主成分分析,从森林生物多样性与群落结构数量特征的众多因子中提取出最重要的健康评价指标,利用层次分析法(AHP法)对中山市常绿针叶林与阔叶林群落结构健康进行综合评价。结果表明:建群种更新苗数、乔木种类、灌木层密度和草本层盖度是影响中山市常绿针叶林群落结构健康最主要的4个因子;5种常绿针叶林群系结构健康得分排序为:湿地松-马尾松林>杉木林>马尾松林>岗松-湿地松林>湿地松林。建群种更新苗数、草本层盖度和乔木株数是影响中山市常绿阔叶林群落结构健康最大的3个因子;8种常绿阔叶林群系结构健康得分排序为:粘木-凹叶红豆林>华鼠刺-粘木-凹叶红豆林>乌榄-樟树林>白颜树-红车林>降真香-白颜树林>荷木-台湾相思林>台湾相思林>银柴-小盘木-红车林。     

Vulnerability of planted forests to biotic and abiotic disturbances

Losses through reduced growth or mortality attributable to pests, diseases, and abiotic disturbances are generally less in intensively managed, planted forests than in natural forests. Among plantation forests, the most healthy forests are those of exotic species growing a long way from their native range (e.g., Pinus radiata D. Don in New Zealand) and the least healthy ones are those of indigenous species (e.g., Eucalyptus nitens (Deane & Maiden) Maiden in Tasmania). The better health of plantations is a reflection of the generally good growing conditions, the proper matching of site to species that is possible in artificial culture and in the case of exotic species, the freedom from the many pests and diseases present in the native habitat of exotics.     

Landscape-scale variation in the structure and biomass of the hill dipterocarp forest of Sumatra: Implications for carbon stock assessments

One of the first steps in estimating the potential for reducing emissions from deforestation and forest degradation (REDD) initiatives is the proper estimation of the carbon components. There are still considerable uncertainties about carbon stocks in tropical rain forest, coming essentially from poor knowledge of the quantity and spatial distribution of forest biomass at the landscape level.     

Combining optimization and simulation tools for short-term planning of forest operations

The use of optimization techniques is well established in forest short-term planning and decision-making. Yet, existing techniques may pose some limitations for tackling with stochastic factors impacting in the execution of forest operations, such as delays, equipment breakdowns and other unexpected events. This paper explores the potential of using optimization techniques in combination with discrete-event simulation (DES) models for planning harvesting and logistics operations acknowledging uncertainty. DES models may be useful for assessing the performance and identifying bottlenecks associated with the execution of the deterministic plans retrieved with optimization techniques, when such stochastic events occur. This paper further presents an approach for the combination of a heuristic and a DES model developed in SIMIO. This approach was used to solve the raw material reception problem (RMRP) at a Portuguese pulp mill. This paper concludes with the analysis of the performance of deterministic schedules for the wood trucks considering uncertainty in their arrival at the mill.     

林业有害生物胁迫指标在森林健康评价中的特殊性及森林康复策略

从林业有害生物与森林、森林生态系统及森林灾害的关系出发,分析了林业有害生物胁迫指标在森林健康评价中的特殊性,指出林业有害生物是森林生态系统中各种不健康因素对系统影响的"放大器",是系统出现问题的"指示剂",并用该指标对森林健康状况进行了评价;对我国森林类型进行了分组,在此基础上提出了针对林业有害生物的森林康复策略。     

退耕还林工程监测与评价信息系统平台设计

针对退耕还林工程的特点和工程监测与评价的要求,以退耕还林工程区资源与环境信息为基础,遥感为实时信息获取手段,ARCGIS引擎为开发工具,VB、VC为开发语言,专家知识为纽带,构建退耕还林工程监测与评价信息系统,以实现对工程的实时监测、评估和监督,保证工程的顺利完成。     

Ecological background of crown condition,growth and nutritional status of <Emphasis Type="Italic">Picea abies</Emphasis> (L.) Karst. in the Bavarian Alps

Using a representative sample of stands from a cross section through the Bavarian portion of the northern Calcareous Alps, this study evaluates the plausibility and significance of causal hypotheses for an explanation of the poor crown condition of Norway spruce in mountain forests: (1) ozone exposure in conjunction with (a) drought and (b) ample water supply; (2) soil-borne nutrient deficiency; (3) drought; and (4) tree age. Site index and, in a subset of stands, foliar nutrient concentrations are considered as additional indicators of tree vigour. According to principal component analysis and multiple regression, crown condition was controlled by soil chemistry (transparency increased towards shallow calcareous soils), stand age and, to a smaller degree, by an interaction between ozone exposure and drought. Site index was best explained by a model including elevation, soil chemistry and drought. Tree nutrition clearly reflected the main soil chemical gradient, and P, N and Fe deficiencies were found in transparent stands, which had markedly smaller needles. The similar distributions of crown transparency, site index and nutrition present a strong argument for the hypothesis that soil chemistry has constrained the vigour of spruce trees in the Calcareous Alps for a long time. By leaving unproductive stands to age naturally, forest management has accentuated the pattern of crown condition. In the heterogeneous alpine landscape, possible effects of recent increases in ozone exposure have to be viewed extremely carefully against the background of these natural and anthropogenic covariables.     

Using pre-classification to improve the accuracy of species-specific forest attribute estimates from airborne laser scanner data and aerial images

The aim of this study was to examine whether pre-classification (stratification) of training data according to main tree species and stand development stage could improve the accuracy of species-specific forest attribute estimates compared to estimates without stratification using k-nearest neighbors (k-NN) imputations. The study included training data of 509 training plots and 80 validation plots from a conifer forest area in southeastern Norway. The results showed that stratification carried out by interpretation of aerial images did not improve the accuracy of the species-specific estimates due to stratification errors. The training data can of course be correctly stratified using field observations, but in the application phase the stratification entirely relies on auxiliary information with complete coverage over the entire area of interest which cannot be corrected. We therefore tried to improve the stratification using canopy height information from airborne laser scanning to discriminate between young and mature stands. The results showed that this approach slightly improved the accuracy of the k-NN predictions, especially for the main tree species (2.6% for spruce volume). Furthermore, if metrics from aerial images were used to discriminate between pine and spruce dominance in the mature plots, the accuracy of volume of pine was improved by 73.2% in pine-dominated stands while for spruce an adverse effect of 12.6% was observed.     

Demand for non-timber forest products: Surveys of urban consumers and sellers in Switzerland

In recent years, worldwide socioeconomic, ecological, and cultural changes have led to a paradigm shift in forestry and forest management. Some years ago, most forest enterprises exclusively focused on wood production, whereas today, forest management is expected to be multifunctional and economically as well as socially and ecologically sustainable [Harrison, S., Herbohn, J., Niskanen, A., 2002. Non-industrial, smallholder, small-scale and family forestry: what's in a name? Small-scale Forest Economics. Management and Policy 1 (1), 1–11; Schmithuesen, F., 2004. Forest policy developments in changing societies — political trends and challenges to research. Towards the sustainable use of Europe's forests: Forest ecosystems and landscape research: Joensuu: European Forest Institute, Proc., vol. 49, pp. 87–99]. In this context, non-timber forest products (NTFPs) such as forest honey, mushrooms, or berries could gain importance as an additional source of income for the forestry sector. To assess the market potential of NTFPs in Switzerland, two corresponding surveys were conducted. A consumer survey (N = 897) conducted in six cities in Switzerland investigated the purchase of Swiss NTFPs, consumer preferences, and demand potentials. An additional survey of sellers of NTFPs (N = 105) looked at these aspects from a complementary perspective. The results showed that there is a high esteem and considerable demand potential for such products among urban consumers. Food products were mentioned most frequently. Both consumers and sellers considered quality and environmental friendliness the most important attributes of NTFPs. Structural and organizational innovations and considerable marketing efforts and sales promotion would be required to expand the market for Swiss NTFP, however. Our results indicate that certification of the products' origin, environmental performance, and quality could support such efforts and that recreational and ecological forest services have a synergetic potential for the marketing of NTFPs.     

The susceptibility of white spruce seedlings to overwinter injury and their post-injury field responses

Foliar and stem injury was assessed in white spruce (Picea glauca (Moench) Voss) seedlings planted in the spring and in the summer of 1992 and injured during their first overwintering on two sites in the southeastern boreal forest of British Columbia. Freeze-desiccation appears to be the main cause of the injury. Seedlot effect on the injury was significant, while planting time effect was not. Although the seedlot effect may be confounded with stock-type effect, analyses indicated increasing injury with increasing seedling height and declining ground-level diameter. Seedling vigour (height and diameter increments in the previous growing season) was also significantly related to the injury which increased with increasing vigour but the significance of this relationship varied from site to site. Condition of injured seedlings generally declined further during the post-injury growing season. This decline was greater in spring-planted than in summer-planted seedlings. Excavated root systems of container-grown seedlings showed the majority of post-planting root growth originating from the bottom-third of the nursery-container plug, deeper than 10 cm from the soil surface. This is seen as a factor potentially contributing to desiccation injury as the soil in the geographic region often remains frozen at these depths long into spring.     

吉林省辉南森林经营局基层林场转为公益型林场的测算探讨

深化重点国有林区和国有林场苗圃管理体制改革是当前林业战线的重要任务之一。本文根据本局森林资源现状的研究分析,提出了将基层林场转为公益型林场,并对林场的规模、人员设置及生态效益进行了科学测算。     

Uncertainties of mapping aboveground forest carbon due to plot locations using national forest inventory plot and remotely sensed data

Abstract

Forest carbon sinks significantly contribute to mitigation of atmospheric concentrations of carbon dioxide. Thus, estimating forest carbon is becoming important to develop policies for mitigating climate change and trading carbon credits. However, a great challenge is how to quantify uncertainties in estimation of forest carbon. This study investigated uncertainties of mapping aboveground forest carbon due to location errors of sample plots for Lin-An County of China. National forest inventory plot data and Landsat TM images were combined using co-simulation algorithm. The findings show that randomly perturbing plot locations within 10 distance intervals statistically did not result in biased population mean predictions of aboveground forest carbon at a significant level of 0.05, but increased root mean square errors of the maps. The perturbations weakened spatial autocorrelation of aboveground forest carbon and its correlation with spectral variables. The perturbed distances of 800 m or less did not obviously change the spatial distribution of predicted values. However, when the perturbed distances were 1600 m or larger, the correlation coefficients of the predicted values from the perturbed locations with those from the true plot locations statistically did not significantly differ from zero at a level of 0.05 and the spatial distributions became random.