Characterizing forest species composition using multiple remote sensing data sources and inventory approaches

Abstract

The purpose of the study was to evaluate tree species composition estimated using combinations of different remotely sensed data with different inventory approaches for a forested area in Norway. Basal area species composition was estimated as both species proportions and main species by using data from airborne laser scanning (ALS) and airborne (multispectral and hyperspectral) imagery as auxiliary information in combination with three different inventory approaches: individual tree crown (ITC) approach; semi-individual tree crown (SITC) approach; and area-based approach (ABA). The main tree species classification obtained an overall accuracy higher than 86% for all ABA alternatives and for the two other inventory approaches (ITC and SITC) when combining ALS and hyperspectral imagery. The correlation between estimated species proportions and species proportions measured in the field was higher for coniferous species than for deciduous species and increased with the spectral resolution used. Especially, the ITC approach provided more accurate information regarding the proportion of deciduous species that occurred only in small proportions in the study area. Furthermore, the species proportion estimates of 83% of the plots deviated from field measured species proportions by two-tenths or less. Thus, species composition could be accurately estimated using the different approaches and the highest levels of accuracy were attained when ALS was used in combination with hyperspectral imagery. The accuracies obtained using the ABA in combination with only ALS data were encouraging for implementation in operational forest inventories.     

Possibilities for harmonizing national forest inventory data for use in forest biodiversity assessments

Representatives of the national forest inventories (NFIs) of27 European countries and the USA evaluated possibilities fora common approach to forest biodiversity reporting. The projectwas conducted under the auspices of COST (European Cooperationin the field of Scientific and Technical Research) Action E43,‘Harmonisation of National Forest Inventories in Europe:Techniques for Common Reporting’. Based on the analysisof responses to an initial questionnaire regarding the mostecologically important and technically feasible variables formonitoring forest biodiversity using NFI data, 16 key variableswere selected. Responses to a second questionnaire consistingof six questions regarding assessment of the 16 key variablesrevealed that the NFIs of most responding countries alreadyassess a large proportion of these variables. Each of the 16variables is assessed in at least eight NFIs. However, the responsesregarding assessment methods and necessary field crew expertisevaried considerably. As a first example, although tree diametersat breast height (d.b.h.) are assessed by every country, thereis a wide range of minimum d.b.h. thresholds from 0 mm in Finlandto 12 cm in Cyprus and Switzerland. As a second example, eightcountries estimated that almost all inventory variables requirehighly skilled forest staff with specialized training, but mostcountries agree that a middle level of expertise is sufficient.Despite differences in current NFI methods, overall, the resultsof the study indicate positive possibilities for achieving amoderate level of European-wide harmonization.     

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.     

甘肃省森林资源连续清查体系的建立与完善

论述了甘肃省森林资源连续清查体系的建立及逐步完善的过程，分析了每次复查的技术特点及存在的问题，提出了进一步完善和优化森林资源连续清查体系的意见。     

A model-based performance test for forest classifiers on remote-sensing imagery

Ambiguity between forest types on remote-sensing imagery is a major cause of errors found in accuracy assessments of forest inventory maps. This paper presents a methodology, based on forest plot inventory, ground measurements and simulated imagery, for systematically quantifying these ambiguities in the sense of the minimum distance (MD), maximum likelihood (ML), and frequency-based (FB) classifiers. The method is tested with multi-spectral IKONOS images acquired on areas containing six major communities (oak, pine, fir, primary and secondary high tropical forests, and avocado plantation) of the National Forest Inventory (NFI) map in Mexico. A structural record of the canopy and optical measurements (leaf area index and soil reflectance) were performed on one plot of each class. Intra-class signal variation was modelled using the Discrete Anisotropic Radiative Transfer (DART) simulator of remote-sensing images. Atmospheric conditions were inferred from ground measurements on reference surfaces and leaf optical properties of each forest type were derived from the IKONOS forest signal. Next, all forest types were simulated, using a common environmental configuration, in order to quantify similarity among all forest types, according to MD, ML and FB classifiers. Classes were considered ambiguous when their dissimilarity was smaller than intra-class signal variation.     

An aerial photograph auto-interpretation system for forest resource inventory

Aerial photographs arc important information sources for forest inventory. With the development of science and technology, an automated approach to aerial photograph interpretation has been sought. This paper introduces an experimental computer system for the auto-interpretation of aerial photographs. On thebasis of the experimental system, several algorithms are developed for the interpretation of density, crown closure, working groups and species composition of forest stands. Experiments show that auto—interpretation works well for some forest inventory data.     

Remote sensing and forest inventory for wildlife habitat assessment

Researchers and managers undertaking wildlife habitat assessments commonly require spatially explicit environmental map layers such as those derived from forest inventory and remote sensing. However, end users of geospatial products must often make choices regarding the source and level of detail required for characterizing habitat elements, with few published resources available for guidance. We appraised three environmental data sources that represent options often available to researchers and managers in wildlife ecological studies: (i) a pre-existing forest inventory; (ii) a general-purpose, single-attribute remote sensing land cover map; and (iii) a specific-purpose, multi-attribute remote sensing database. The three information sources were evaluated with two complementary analyses: the first designed to appraise levels of map quality (assessed on the basis of accuracy, vagueness, completion, consistency, level of measurement, and detail) and the second designed to assess their relative capacity to explain patterns of grizzly bear (Ursus arctos) telemetry locations across a 100,000-km² study area in west-central Alberta, Canada. We found the forest inventory database to be reasonably functional in its ability to support resource selection analysis in regions where coverage was available, but overall, the data suffered from quality issues related to completeness accuracy, and consistency. The general-purpose remote sensing land cover product ranked higher in terms of overall map quality, but demonstrated a lower capacity for explaining observed patterns of grizzly bear habitat use. We found the best results using the specific-purpose, multi-attribute remote sensing database, and recommend that similar information sources be used as the foundation for wildlife habitat studies whenever possible, particularly those involving large areas that span jurisdictional boundaries.     

Development of mobile GIS system for forest resources second-class inventory

A special mobile GIS(Geographic Information System) system used for forest resources second-class inventory was developed on the basis of traditional forest resources inventory,remote sensing,GPS(Globe Positioning System) and embedded technology.Portable instrument,embedded development and the integration technology of RS(Remote Sensing),GIS and GPS are all used in this special mobile GIS system.Further,the system composition,key techniques,and current situation of the practical application in China were analyzed in the study.The results are important for applying modern high-tech for the planning and design of digital forest resources to improve the precision and efficiency of inventory and reduce the labor cost and financial investment.     

国家森林资源连续清查森林健康监测方法的探讨

对国家森林资源连续清查森林健康的监测方法进行分析,指出现行监测方法的局限性,并结合欧洲和美国森林健康监测指标体系和森林资源调查监测同行的专家意见,提出新的监测指标和评价方法,为进一步完善有关国家森林资源连续清查森林健康监测的技术标准和调查方法提供参考。     

基于森林资源清样调查资料的森林生产力估算模式--以中国油松林为例

准确地评估森林净第一性生产力(NPP)对于评估全球收支有着十分重要的作用。本文充分利用森林资源清样调查资料,并动态地评估森林生产力,以油松林为例建立了反映生物因素(蓄积量V和林龄A)和气候因素(年实际蒸散E)综合影响的中国油松林生物气候生产力(NPPa)模型。基于所建模型和第四次我国油松林资源的清样调查资料(1989-1993年),估算了中国油松林的净第一性生产力,并借助于地理信息系统软件给出了中国油松林的分布格局。结果表明:我国油松林的平均净第一性生产力为7.82thm-2a-1,其变化幅度为3.32~11.87thm-2a-1。中国油松林净第一性生产力有明显的区域差异,表现为南高北低的分布趋势。山西和陕西为中国油松林的集中分布区,生产力水平处于中等,约为7.4thm-2a-1;油松林集中分布区的南部(四川、湖北、河南等省),生产力水平较高,均大于7.7thm-2a-1;而在油松林集中分布区的北部和西部(内蒙古、宁夏等省),生产力水平较低,NPP均低于5thm-2a-1。该研究为利用森林资源清样调查资料评估森林NPP的动态及研究其对气候变化的响应提供一个有效思路。图3表2参46。     

EPSFM系统在森林资源调查中的应用

本文在简要介绍EPSFM(森林资源地理信息系统)的基础上，结合森林资源调查的第一信息基本特点，阐述了FPSFM系统在森林资源调查中应用的基本技术和方法，并给出了详尽的实例说明。     

森林资源连续清查体系改进建议

介绍了国外林业发达国家森林资源连续清查体系的抽样设计、样地设计以及调查因子;概述了我国森林资源连续清查的发展情况及存在问题;并从抽样设计、年度出数以及与林地年度变更结合使用方面提出了改进建议。     

Value of forest information

Traditionally, the quality of forest inventory data has been measured with root mean square error of interesting variables. In many occasions, however, even this information has not been available for all variables of interest, as the main focus has always been on the accuracy of timber volume estimates. In recent years, the quality of data as a basis for decision-making has also been considered, using so-called cost-plus-loss analysis. In such analysis, the optimal data acquisition method is defined to be the one which minimizes the total costs of inventory, i.e., the direct inventory costs and the losses due to suboptimal decisions based on incorrect data. It would, however, be possible to go even further, and estimate the value of certain information, or even information concerning a certain forest variable/parameter in decision-making. This is possible when utilizing Bayesian decision theory. It would enable inventory researchers to concentrate on important issues, and managers to invest optimally on data acquisition process. This review presents the research carried out in valuation of information in different fields and discusses the possibilities to use it in forestry applications.     

掌上电脑森林调查系统在集体林权制度改革工作中的应用

集体林权体制改革涉及林农切身利益,是目前我省林业工作的一项重要任务。利用先进技术对林改小班进行准确定位、精确测量是林改工作的基础。集GIS、GPS、PDA技术于一身的掌上电脑森林调查系统应用到林改实际工作中,提高了小班定位精度,保证了小班界线及面积的准确性。     

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.     

3S集成技术在森林资源调查中的应用

森林资源调查是建立或更新森林经营方案、制定森林采伐限额、进行林业工程规划设计和森林资源管理的基础,也是制定区域国民经济发展规划和林业发展规划、实行森林生态效益补偿和森林资源资产化管理、指导和规范森林科学经营的重要依据。近年来,以微电脑为基础的3S（RS、GIS、GPS）集成技术进行的高精度面积测量和GIS自动成图,为提高面积测量精度和不同地类准确定位提供了重要技术保障。星源通掌上森林资源调查仪是以3s集成技术为基础研制的森林资源调查仪器,为检验其测量精度,在汪清林业局不同林地选择地形明显、最易勾绘的10个小班进行精度检验,小班的勾绘面积最小为1．34hm^2,最大为35．80m^2。结果表明,测量精度最低为98．0％,最高为99．2％,平均为98．71％;星源通掌上森林资源调查仪可广泛应用于森林资源调查、伐区调查设计、造林地验收、林火损失评估、征占用林地调查等多个方面。     

浅析我国森林资源清查体系存在的问题与对策

全国森林资源清查是通过定期、准确查清各省的森林资源数量、质量及其消长动态,从而掌握森林生态系统的现状和变化趋势,对森林资源与生态状况进行综合评价。由于清查覆盖面积大、跨度时间长,清查结果不能有效及时利用。本文浅析了我国森林资源连续清查体系在应用中存在的不足,并提出改进措施,以期为完善我国森林资源连续清查体系提供参考。     

Efficiency of alternative forest inventory methods in partially harvested stands

Forest inventory is vital to all aspects of forest management and inventory methods can vary greatly in their accuracy, precision, efficiency and cost. In Maine, much of the forestland base has been managed using partial harvesting methods over the past two decades. These partial harvesting methods generally produce highly heterogeneous stand structures and composition. Consequently, it is currently unclear which inventory methods are best given the distinct spatial and structural heterogeneity that is created. We compared efficiency and stand-level inventory estimates using horizontal point, fixed area and horizontal line sampling measurement methods in 16 partially harvested stands across northern and central Maine. Some stand-level variables were sensitive to measurement method (e.g., volume, quadratic mean diameter and small stem density and basal area), while others were less sensitive (e.g., overall basal area and stem density). Efficiency, defined as a combination of precision of volume estimates and measurement time, varied among measurement methods at lower stand basal area values but was similar at higher basal area, with the exception of the fixed area method. Overall, horizontal line sampling proved to be a viable method in post-partial harvest stand conditions. Our results illustrate the trade-offs between precision and time costs involved in several measurement methods under a range of heterogeneous stand conditions.     

Selecting tree species for testing climate change migration hypotheses using forest inventory data

The lack of objective tree species lists hinders the assessment of climate change effects on tree species distributions. The goal of this study was to develop and evaluate criteria for selecting tree species used in large-scale tree migration monitoring efforts. The results of this study indicate that tree migration conclusions are highly dependant on the species selected for examination. It was found that tree species’ median latitudes or forecasted future areas provided objective criteria for development of species lists for migration hypothesis testing with the latter being insensitive to simulation error. Furthermore, only 10–15 of the top species, in terms of high median latitudes or loss in forecasted future area, are needed to maximize the sensitivity of a migration index. The use of such criteria in this study indicated a northward shift of sensitive tree populations of 27 km. It is suggested that examining species only the most likely to migrate serves as an objective starting point for migration detection. In contrast, the inclusion of all tree species commonly observed in large-scale forest inventories can obfuscate migration detection with tree species that have little ecological reason to immediately migrate in a changing climate.     

利用森林资源连续清查数据编制地位级表

首先利用新疆阿勒泰山国有林管局森林资源连续清查中的279块华山松样地,通过对比选择了方程作为地位级导向曲线的最优模型;在此基础上采用等分法编制了地位级表,并对其精度进行了检验;结果表明其精度可靠,达到了林业生产和调查的要求。