Spatial variability and optimal sampling strategy of soil respiration

Soil respiration is the second largest flux of carbon between terrestrial ecosystems and the atmosphere and is affecting climate sensitivity and vulnerability of the terrestrial carbon stock. Monitoring soil carbon dioxide efflux is a complex task, due to the high spatial and temporal variability of the fluxes. For this reason, more than 30 sampling points are required to attain reliable estimates of ecosystem soil respiration. However, the number of sampled points is often limited by labour, time and budget constraints. Stratified sampling is an alternative to random sampling as a method to reduce the number of sampling points when an effective proxy variable is available for the definition of the strata.     

A simulation study on the effects of plot size and shape on sampling plant species composition for biodiversity management

Sustainable management of plant diversity in a forest requires adequate information that is often derived from samples. With limited resources, the plot design has to be efficient. Most studies focused on evaluating effects of plot designs on sample estimates of species richness at landscape scale. This study aims at filling a knowledge gap by investigating how plot size and shape affect sample estimates of species composition at a local scale. Two census datasets with distinct forest ecosystems were used. Fifteen combinations of plot size and shape were simulated. Species compositional similarity between two combinations of plot design at a sample point was estimated by Jaccard and Sørensen indices, and their abundance-adjusted counterparts. Similarity in species composition decreased with increasing difference between two plot sizes. Plots with varying shapes were found to have different local species composition but could be similar in the number of observed species, which has not been explicitly reported elsewhere. For less species-rich forests, a 0.025–0.05 ha circular plot is recommended. For species-rich forests, a 0.05–0.1 ha rectangular plot with aspect ratio of at least 1:20 is recommended. The results should be of interest to stakeholders managing small area forests for conservation of plant diversity.     

Identifying dendroecological growth releases in American beech,jack pine,and white oak: Within-tree sampling strategy

The objective of this project was to identify the timing of growth release events detected from tree ring widths and compare whether two cores taken from the same tree reconstructed the same disturbance history. This research question is important because current dendroecological reconstructions of canopy disturbance rely on sampling one core per tree; however, the variation of releases from different cores from the same tree has never been evaluated. We sampled two increment cores from 20 jack pine, 17 white oak, and 19 American beech and identified release events with two commonly employed methods: radial growth averaging technique and boundary line criteria. In jack pine, 85% of the paired cores showed identical releases with the radial growth averaging technique, but 15% of the paired cores varied in reconstructed growth releases. In the jack pine, no releases were identified with the boundary line criteria for any of the paired cores. In the white oak, 65% had identical releases identified with the radial growth averaging technique and 35% of the pairs showed differences. The boundary line criteria for white oak had agreement between releases for 76% of the pairs and different release histories for 24% of the pairs. In the American beech, we were only able to use the radial growth averaging technique and this method showed identical release timing for 79% of the paired cores and differences in 21% of the paired cores. This level of within-tree growth variation is unlikely to influence identification of stand-wide disturbances; however, for reconstructions of small-scale disturbances it is likely to under-represent disturbance events. Therefore, for small-scale disturbance reconstructions, we recommend dendroecologists consider sampling two cores per tree instead of the standard sample of one core per tree.     

Poisson sampling and some alternatives in timber sales sampling

Sampling schemes are studied for timber sales where every tree in the population has to be visited. A strong linear relationship is known to hold between the variable of interest, volume in m³ (y), and tree basal area times height (x) (in cm²m). Purposive sampling of trees over the X-range and stratified sampling with regression estimators are recommended as worthwhile alternatives to Poisson sampling for efficiency and for yielding consistently good results where the model between the dependent and independent variables is known to be reasonable. Two other designs, selecting the n trees with largest X-values and the trees with 20% smallest and 80% largest X-values, are shown to be high-risk procedures.     

A preliminary evaluation of throughfall sampling techniques in a mature coniferous forest

Rainfall, throughfall and stemflow were measured and canopy interception loss was derived for 14 rainfall events from June 22 to August 30, 2008 within a mature declining hybrid white spruce(Picea glauca(Moench) Voss × P. engelmannii Parry ex Engelm.)- subalpine fir(Abies lasiocarpa(Hook.) Nutt.)- lodgepole pine(Pinus contorta var.latifolia Dougl. ex Loud.) stand in south-central British Columbia, Canada. Stemflow was negligible during the study period, while, respectively throughfall and canopy interception loss accounted for approximately59.4% and 40.6% of the 50.1 mm of cumulative rainfall. Throughfall variability was assessed with three approaches involving roving and stationary wedge-type gauges, and stationary trough gauges. Throughfall exhibited large spatial variability with the coefficient of variability of study period throughfall sampled using 16 stationary trough gauges being30.3%, while it was 38.0% and 28.7% for 32 stationary and 32 roving wedge gauges, respectively. Our analysis suggests that a roving gauge method is better than a stationary approach since the errors associated with event mean throughfalls are summed quadratically and a greater portion of the canopy area is sampled. Trough gauges were more efficient than wedge gauges; however, this efficiency was less than expected given their much larger sampling areas, suggesting that spatial autocor-relation lengths of throughfall may be longer than the trough systems. The spatial distribution of throughfall showed a high degree of temporal persistence throughout the study suggesting the existence of stable "wet" and "dry" inputs to the floors of these coniferous forests.     

立木调查中样地的面积、数量与抽样精度的关系

抽样调查是立木调查中常用的调查方式,抽样比、样地面积、样地数量与获得的各项调查因子之间存在着一定的关系。通过不同样地面积、不同样地形式和数量的对比实验,以实例来说明其间存在的关系,供同行在实际工作中参考。     

中心抽样分布律的初步研究

根据谭启栋教授提出的典型中心抽样设想及肖兴彦等人对典型中心抽样分布律的研究成果，提出中心抽样分布律的数学模型，并对其四个特征数加以求证，同时对中心抽样方法作以介绍。中心抽样方法即在概知总体平均值的附近随机选取一定数量的样本单元，以样本平均值作为总体平均值的无偏估计。此法选取样本少，估测精度高。     

A method for axenic sampling of wood from standing trees

A method is described to collect wood samples axenically from standing trees by the use of a Pressler borer in conjunction with protective sterile jackets.     

Combining double sampling for stratification and cluster sampling to a three-level sampling design for continuous forest inventories

We extend the well-known double sampling for stratification sampling scheme by cluster subsampling to a three-level design and present corresponding estimators based on the infinite population approach in the first phase. After stratification of the sample points (phase I), a second-phase sample is drawn independently among the first-phase points within each stratum. On level III, clusters are formed of those phase II points and a sample of clusters is finally drawn without replacement. We used the forest planning units compartment and subdistrict as clusters and moreover formed clusters with a heuristic for the vehicle routing problem. The precision of the new estimator was compared to that achieved with classical double sampling for stratification in a case study. The results indicate that the expected increase in sampling errors caused by clustering cannot be compensated by the reduced inventory costs under the conditions given in the case study.     

A review of the sampling theory of comprehensive forest resources monitoring

Sampling is a key technique in comprehensive forest resources monitoring. The history of the sampling survey was briefly reviewed and sampling theories were classified and compared in detail. On the basis of that, the application of different sampling methods in comprehensive forest resources monitoring was illustrated in accordance with the sampling classification of Michael Köhl et al. Improvement of the sampling system in China was discussed to meet the new requirements of forest monitoring.     

Design-unbiased point-to-object sampling on lines,with applications to areal sampling

Sampling methods that depend on the distance between a sample point and a fixed number of objects, such as trees or downed logs, have often been proposed in the forestry and ecology literature. However, such methods have been biased when objects are not distributed with complete spatial randomness, have required difficult field procedures (such as measuring the position of out-of-sample objects), or both. Here a new approach based on measurement of the distance to objects along sample lines is proposed. The approach does not require measuring the position of out-of-sample objects, and its design-unbiased estimators require only simple arithmetic. Furthermore, because many useful sampling procedures can be related back to sampling on a line, the new method leads quickly to sampling procedures applicable when objects are distributed in a two-dimensional region. These include, among others, fixed-count approaches to line intersect sampling, a new approach to variable-area transect sampling, and a density-adapted variable sector sampling method.     

A strategy for identifying introduced provenances and translocations

Native species of oak in Britain have been of great importancein our history for their many uses, and have thus been subjectto management and planting by man for centuries. Following eventssuch as the Enclosure Acts of the late eighteenth century andthe Napoleonic wars, many oaks would have been planted. Translocationsand introductions of foreign genotypes were greatly encouragedby early landscape gardeners such as Capability Brown. Britainmust, therefore be a mosaic of native and non-native oaks. Amajor problem arises when we try to identify non-native trees. Due to their long life-cycle, oaks are of necessity both phenotypicallyplastic and genetically very variable and it has been virtuallyimpossible to discriminate between native and non-native formsusing traditional methods. The advent of new molecular genetictechniques however, now allows us to identify DNA markers thatcan distinguish between such forms. The geographic patternsfor two chloroplast DNA markers will be presented. One clearlydifferentiates between oaks from eastern Europe versus westernEurope and can be used to identify translocations of easternEuropean oaks into Britain and western Europe. The second identifiesgenotypes native to East Anglia and can be used to recognizetranslocations into and out of East Anglia.     

森林分层抽样程序

分层抽样在森林资源二类调查、木材消耗量调查、农村社会经济调查当中都经常应用。本文基于CASIO-4500P机型研制其应用程序,供有关人员参考。     

Interval sampling methods in Zagros forests using GIS

In this study, for accuracy and cost an optimal inventory method was examined and introduced to obtain information about Zagros forests, Iran. For this purpose,three distance sampling methods(compound, order distance and random-pairs) in 5 inventory networks(100 m × 100 m, 100 m × 150 m, 100 m × 200 m,150 m × 150 m, 200 m × 200 m) were implemented in GIS environment, and the related statistical analyses were carried out. Average tree density and canopy cover in hectare with 100% inventory were compared to each other.All the studied methods were implemented in 30 inventory points, and the implementation time of each was recorded.According to the results, the best inventory methods for estimating density and canopy cover were compound150 m × 150 m and 100 m × 100 m methods, respectively. The minimum amount of product inventory time per second(T), and(E%)2 square percent of inventory error of sampling for the compound 150 m × 150 m method regarding density in hectare was 691.8, and for the compound 100 m × 100 m method regarding canopy of 12,089 ha. It can be concluded that compound method is the best for estimating density and canopy features of the forests area.     

粗鞘双条杉天牛的危害分布和抽样方法研究

本文采用聚集度指标、频次比较及回归分析方法对粗鞘双条杉天牛在杉木人工纯林的为害分布进行了研究.结果表明,粗鞘双条杉天牛在人工杉木林中为害分布属受密度制约的聚集型分布,其临界密度为m_0=2.5961株/样方;受害株的分布以植株群为基本单元,其形成是由于该天牛扩散活动能力弱,产卵范围比较集中所致.根据回归关系式m=0.6280 0.7905m,可确定随机抽样的理论抽样数θ,θ=t~2/D~2((a 1)/X β 1),以5种不同的抽样调查方法进行比较,结果以棋盘式和平行线抽样调查的结果精确度最高.     

A national forest resources assessment for Costa Rica based on low intensity sampling

A goal of a National Forest Inventory (NFI) is the provision of information which is relevant and required for national level decision making and monitoring in forestry, but also for related sectors.

This paper presents and discusses a pilot study from Costa Rica where in 2000/2001 a low intensity sampling approach was used to generate national level forestry information. On a 15 km × 15 km grid air photo plots were interpreted for forest and land cover type. Readily available 1997 aerial photographs were used that were, however, only available for about 70% of the country: of the 228 grid points for the whole country only 159 could be aerial photo interpreted. Out of the 15 km × 15 km base grid of sample points, a 2 × 3 subset was selected for field assessment, resulting in a sample of 40 cluster plots, each comprising of four elongated rectangular sub-plots of 150 m × 20 m located on the perimeter of a square of 500 m side length.

Two novel components were integrated into the inventory: (1) the field plots were established on all lands, so that the tree resource was not only tallied inside forests but also on all other tree-bearing lands outside forests. (2) In addition to the biophysical information gathered on the traditional field plots, interviews were carried out with forest owners on the site of the field plots, in order to obtain data on the use of the forest resource.

Field work was carried out by 6 field crews and took altogether about 3 months. Results were generated from the field samples for the entire country. Aerial photo based area estimates were compared to the corresponding estimations from field sampling for the same area. According to the field sampling the forest cover for Costa Rica in 2001 is estimated to be 48.4% (simple standard error percent 9.3%). An estimated 8.2% of the total volume (dbh > 30 cm, all species) is outside forest.

This inventory took place with support from Food and Agriculture Organization (FAO) in the framework of FAO–Forest Resources Assessment's (FRA) Program Support to National Forest Assessments; it was carried out jointly by Sistema Nacional de Áreas de Conservación (SINAC), the Costa Rican authority responsible for forestry issues, and Centro Agronómico de Investigación y Enseñanza (CATIE), an international agricultural research center. Experiences of the study were subsequently used to implement similar inventories in three more countries (Guatemala, Cameroon, The Philippines).     

NON-DESTRUCTIVE SAMPLING FOR YIELD ESTIMATION

AIMThemostcommonmethodforas-sessingtotalbiomassisbydestructive1ysampling,i.e.cuttingdownrandomsam-ples,weighingthem,andextrapo1atingtheresultsfortheentirep1antation.Theesti-matewi1lgenerallybemoreaccuratewithalargersample,butenteringa3-5yearo1dplantationtocutdownshootsanddragthemouttobeweighed,isatime-con-sumingbusiness.Itisthereforenecessarytofindsomereliab1emeansofestimatingbiomassfromparameterswhichcanbeeas-ilymeasuredwhi1etheshootsarestillstanding.Amodelneedstobecreatedtoassessbiomassfirs…     

太尔的中国攻略

在全球 2000年太尔公司的前身Neste Chemicals OY及Dyno ASA由北欧最大的工业投资集团IK通过资本运作合并成为新公司--Dynea.     

太尔的中国攻略——太尔绿色家居粘合剂

根据有关国际组织的调查统计,世界上30％的新建和重修的建筑物中发现室内空气有害健康,空气污染被列入对公众健康危害的五种环境因素之一。美国历时五年的一项专题调查发现,大部分室内空气污染程度是室外空气的2～5倍,甚至超过100倍。日本政府的一个调查小组经过检测后于近日宣布,日本27.3％的住宅空气中的甲醛值、12.3％的住宅内的甲苯值和0.13％的住宅中的二甲苯值都明显超标。