The economic impact of green-up constraints in the southeastern United States

Green-up, or adjacency, requirements are a common constraint in forestry. The American Forest and Paper Association has developed a Sustainable Forestry Initiative that includes a green-up constraint which limits the average clearcut opening to 48 ha for 3 years or until the average height of the regenerated trees is >1.4 m. In addition to constraining the average clearcut size, many forestry companies in the southeastern USA voluntarily limit their maximum clearcut size to between 60 and 90 ha. In this research, a heuristic algorithm was used to develop tactical forest plans that consider both the maximum and average clearcut sizes. Economic effects of the green-up constraints were estimated for situations where intensive management can reduce the length of the green-up time from 3 to 2 years on a 21 600 ha ownership in Georgia (USA). For a 60-ha maximum opening size, this reduction in green-up time from 3 to 2 years resulted in an additional US$ 66 600 in present net worth (PNW) over a 10-year analysis period. This corresponds to a US$ 10 per harvested ha, or a 0.8% increase in PNW. The benefit gained by reducing the length of the green-up period is less with a 90-ha maximum clearcut size, where PNW increases by US$ 45 600, or US$ 6.70 per harvested ha, a 0.5% increase. While the total volume per period was near the volume goal produced by a strategic forest plan, the spatial restrictions and the desire to maximize net present value resulted in lower volume of timber products (sawlogs and chip-and-saw logs) from older forest stands. A sensitivity analysis showed that an increase in price or yield further reduced the economic incentive for the reduction of the length of the green-up constraint. As price or volume decreased below expectations, however, the incentive to use intensive forest management practices to reduce the length of the green-up constraint became more attractive, since the differences between a 2-year and 3-year green-up time requirement may be large enough to pay for more intensive management practices.     

Estimating the effects of adjacency and green-up constraints on landowners of different sizes and spatial arrangements located in the southeastern U.S.

The maximum clearcut size and green-up period is important for land managers adhering to voluntary and regulatory guidelines. Therefore the impact of actual and hypothetical clearcut size restrictions is a concern for forest landowners who manage land and intend to practice forestry for profit. In this research, the effect of a 97.1 ha (240 ac) clearcut size constraint with a green-up period of 2-yrs is assessed for forest landowners with different forest land sizes, ownership patterns, and age class distributions. A meta heuristic which consists of threshold accepting, 1-opt tabu search, and 2-opt tabu search is used to develop spatially-constrained forest plans for 27 hypothetical forest landowners. These results are compared to a relaxed solution produced with linear programming, and statistical analyses are used to determine significant differences. The analysis provided enough evidence to suggest that two factors (size of ownership pattern and initial age class distribution), and one interaction factor (ownership size × initial age class distribution) are significant in explaining the differences in the percent reduction in forest plan value among the forests managed by the hypothetical forest landowners. From an absolute value reduction perspective, small-sized older forests were most affected. From a percent value point of view, one can conclude from this analysis that landowners with small-sized forests and young initial age class distributions will be significantly more affected by potential adjacency and green-up restrictions in the southeastern U.S. than other types of landowners.     

Surveys in Private and Communal Forests: Data Collection Methods in Bavaria

More than half of the forest land in Bavaria belongs to private forest owners, who contribute a large amount of the industrial timber supply. The level of information about private forests is in comparison to the communal forests inadequate. The increasing demand for data about the forest sector in Bavaria can be partially covered by regular inventories but requires supplementary monitoring activities. Regular surveys based on voluntary participation deliver data, but often do not fulfil statistical requirements due to low response rates of 15–20% to postal surveys. The Bavarian annual postal cutting survey has been built up over 5 years using a roster of voluntary participants. This pragmatic and cost-effective approach provides reliable data for statistical purposes and gives insight in the forest management activities of small-scale forest owners. Recent technical developments, in particular the availability of grids and digital land-use maps, facilitate the random sampling of forest owners. This approach has been applied in a climate change project, but the results did not meet the expectations because of low response rates. The rather labour- and cost-intensive census of forest owners as applied in the project in Eastern Bavaria cannot be recommended except in exceptional circumstances. In the described project a qualitative approach with four distinct questionnaires has been adopted in order to identify ways to reach forest owners that are either not interested in their forests or do not respond to requests. Due to low response rates the objectives of the study could only be partially achieved.     

An analysis of Norway spruce stem quality in Baden-Württemberg: results from the second German national forest inventory

Additional information concerning the quality of growing stock in forests has been obtained for the first time in Baden-Württemberg and Rheinland-Pfalz during the course of Germany’s second national forest inventory (BWI 2; conducted during the period 2001–2002). In this article, the quality assessment—called stem quality rating method—is described with a special focus on its potential to provide the basis for a more detailed investigation of the growing stock’s quality distribution. As a main result, the article presents and illustrates a model-based quantification of single tree and stand/site variable effects on the quality distribution of Norway spruce. Single tree variables showing a significant effect are diameter at breast height (DBH), height–DBH-ratio (h/d-value), age and distance to forest edge. Additional stand/site variables which have a significant effect are altitude, terrain slope, stand type and inventory team. Due to the ordinal type of the response variable, a categorical regression model is applied. Non-linear effects of predictor variables were detected and modeled by integration of smoothing spline terms. Validating model predictions with regard to expert knowledge in forestry led to the integration of simple constraints in the linear predictor, which controls whether category-specific effects are fitted or not. The resulting model could be described as a vector generalized additive non-proportional odds regression model. This improved insight into the determination of stem quality could be applied in optimization studies to derive optimal silvicultural treatments and in the setting up of management guidelines. Assuming constant relationships between predictor and response variables over time, the combined application with growth simulators allows for a prediction of future joint quality and size class assortment distributions. Finally, the model would allow for a sustainability control of stem quality over time if a consecutive inventory will be conducted during the course of the third German national forest inventory (BWI 3).     

Exploring the “last biotic frontier”: Are temperate forest canopies special for saproxylic beetles?

Conserving saproxylic beetles in temperate forests will require a better understanding of habitat requirements. So far, quantitative community studies have rarely considered their vertical requirements. In comparison with the tropical forest canopy, it remains to be seen whether a comparably high level of beetle diversity exists in the temperate forest canopy.We compared saproxylic beetle assemblages at two vertical levels in three temperate French forests. Two datasets originated from emergence traps of pine and oak deadwood substrates (mid-canopy and forest floor branches) in lowland forests. The third compared flying beetle fauna at mid-canopy and understory levels using pairs of flight interception traps in beech-fir mountain forests.Our study provided contrasting results regarding the contribution of each stratum to biodiversity. Whereas higher abundance and species richness were apparent in understory samples in beech-fir stands and in oak branches, no difference for richness - or even the opposite pattern for abundance - was observed in pine branches. A significant inter-strata dissimilarity was revealed in all datasets. Each stratum harbored specialist taxa. Exclusive canopy species accounted for 20-40% of all species. In accordance with dissimilarity partitioning, arboreal saproxylic beetle communities were not just nested subsets of ground assemblages.It is likely that microhabitat requirements, food availability and other non-resource-based factors (microclimate preference, species interactions) drive the stratification of beetle assemblages.Our results lend support (i) to the recommendation of a multi-strata sampling strategy for forest insects and (ii) to management practices in favour of valuable canopy micro-habitats.     

Relationships between diameter and height of trees in natural tropical forest in Tanzania

The relationship between tree height (h) and tree diameter at breast height (dbh) is an important element describing forest stands. In addition, h often is a required variable in volume and biomass models. Measurements of h are, however, more time consuming compared to those of dbh, and visual obstructions, rounded crown forms, leaning trees and terrain slopes represent additional error sources for h measurements. The aim of this study was therefore to develop h–dbh relationship models for natural tropical forest in Tanzania. Both general forest type specific models and models for tree species groups were developed. A comprehensive data set with 2 623 trees from 410 different tree species collected from a total of 1 191 plots and 38 sites covering the four main forest types of miombo woodland, acacia savanna, montane forest and lowland forests was applied. Tree species groups were constructed by using a k-means clustering procedure based on the h–dbh allometry, and a number of different non-linear model forms were tested. When considering the complexity of natural tropical forests in general and in particular variations of h–dbh relationships due to high species diversity in such forests, the model fit and performance were considered to be appropriate. Results also indicate that tree species group models perform better than forest type models. Despite the fact that the residual errors level associated with the models were relatively high, the models are still considered to be applicable for large parts of Tanzanian forests with an appropriate level of reliability.     

A multi-criterion index for the evaluation of local tropical forest conditions in Mexico

Despite the ecological and economical importance of tropical forests they are currently affected by human activities, mainly through deforestation and selective extraction. With the aim of making an opportune diagnosis of the condition of forests, we developed an ecological index based on qualitative and semi-quantitative data, allowing a quick diagnosis in order to manage and conserve tropical forests. We evaluated 44 plots of tree vegetation, measuring canopy height, number of strata, tree cover, dominant trees, number of tree species, as well as the management of and damage to the forest. The data of each parameter was classified in categories of 3, 4 or 5, which were normalized between 0 and 1 for the worst and best characteristics, respectively. For the purpose of analysis, the average, a set of IF–THEN rules, and fuzzy logic were applied and as a result we obtained a model that measures the ecological condition of the tropical forests. The model has the advantages of having an ecological basis, allows data to be gathered quickly and is clear and easy to manage and interpret. When running the model, the value of each intermediate variable is displayed, thus allowing the detection of where necessary action is required to improve the ecological condition of the forest. We expect this index to contribute in evaluating the effectiveness of forest management and possibly offer advice for the short-term management and conservation of the remnants of tropical forests.     

Characterizing changes in land cover and forest fragmentation from multitemporal Landsat observations (1993-2018)in the Dhorpatan Hunting Reserve,Nepal

Natural forces and anthropogenic activities greatly alter land cover,deteriorate or alleviate forest frag-mentation and affect biodiversity.Thus land cover and forest fragmentation dynamics have become a focus of concern for natural resource management agencies and biodiversity con-servation communities.However,there are few land cover datasets and forest fragmentation information available for the Dhorpatan Hunting Reserve (DHR) of Nepal to develop targeted biodiversity conservation plans.In this study,these gaps were filled by characterizing land cover and forest frag-mentation trends in the DHR.Using five Landsat images between 1993 and 2018,a support vector machine algorithm was applied to classify six land cover classes:forest,grass-lands,barren lands,agricultural and built-up areas,water bodies,and snow and glaciers.Subsequently,two landscape process models and four landscape metrics were used to depict the forest fragmentation situations.Results showed that forest cover increased from 39.4％ in 1993 to 39.8％ in 2018.Conversely,grasslands decreased from 38.2％ in 1993 to 36.9％ in 2018.The forest shrinkage was responsible for forest loss during the period,suggesting that the loss of for-est cover reduced the connectivity between forest and non-forested areas.Expansion was the dominant component of the forest restoration process,implying that it avoided the occurrence of isolated forests.The maximum value of edge density and perimeter area fractal dimension metrics and the minimum value of aggregation index were observed in 2011,revealing that forests in this year were most fragmented.These specific observations from the current analysis can help local authorities and local communities,who are highly dependent on forest resources,to better develop local forest management and biodiversity conservation plans.     

Using mixed integer programming and airborne laser scanning to generate forest management unitsOA

Airborne laser scanning(ALS) has been widely applied to estimate tree and forest attributes, but it can also drive the segmentation of forest areas. Clustering algorithms are the dominant technique in segmentation but spatial optimization using exact methods remains untested. This study presents a novel approach to segmentation based on mixed integer programming to create forest management units(FMUs). This investigation focuses on using raster information derived from ALS surveys. Two mainstrea...     

基于随机森林的杉木标准树高曲线

以湖北省赤壁市国有林场40块杉木人工林实测数据为例,运用随机森林方法,以胸径、优势树高、优势胸径为自变量,建立树高预测模型。首先根据随机森林的置换精度重要性筛选出建模的自变量,并确定决策树的数量和竞争节点变量数,得到决定系数R2为0.9450,均方误差MSE为2.6966的随机森林树高预测模型。利用检验数据对随机森林树高预测模型和传统树高预测模型分别进行精度检验。结果表明：随机森林模型的拟合效果与预测效果都优于该传统树高模型,随机森林模型可以作为有效的树高预测技术。 关键词：杉木;标准树高曲线;随机森林     

Adaptive versus fixed policies for economic or ecological objectives in forest management

In the context of forest management, a fixed harvesting policy consists in trying to convert stands of trees to a chosen state at fixed intervals, regardless of the stand state and of the state of the market. In an adaptive policy, instead, the post-harvest state and the timing of the harvest depend on the stand and market states at the time of the decision. The objective of this study was to determine the practical gain from the theoretically superior adaptive policies. To this end, we compared optimal fixed and adaptive policies obtained with identical models and assumptions, and with data from the Douglas-fir/western-hemlock forests in the Pacific Northwest of the United States. In maximizing economic returns from harvests over an infinite time horizon, the net present value was 17 percent higher with an adaptive than with a fixed policy. It was 22 percent higher when the objective was to maximize annual harvest. The adaptive policy was even more superior with undiscounted, non-economic objectives, such as the area of spotted owl habitat (+37 percent gain), or the area of late-seral forest (+51 percent), but less so in maximizing the stock of high quality logs (+6 percent). The adaptive formulation also lent itself readily to multi-objective management.     

树木、林内、林冠上与森林区风速廓线研究

One of the most important and frequently studied variable in forests and the most basic element in governing transport processes of airflow is wind speed. The study of wind profile, defined as the change of wind velocity with height, and wind velocity are important because of tree physiological and developmental responses. Generally, wind profiles above the ground or at a canopy surface follow classical logarithm law, but wind profiles in a single tree and in a forest stand are not logarithmic. This paper summarizes the results of wind profile studies within a single tree, in a forest stand, above the forest canopy and in a forest area from recent research in a coastal pine forest. The results demonstrate that: 1) wind profiles with in a single conifer tree crown showed an exponential function with height, 2) wind profiles in forest stands were able to be expressed by attenuation coefficient of wind, 3) wind profiles over a forest canopy could be determined using profile parameters (friction velocity, roughness length and displacement), and 4) for a forest area, the extreme wind speed could be predicted reasonably using the methods developed for the design of buildings. More research will be required to demonstrate: 1) relationships between wind profiles and tree or stand characteristics, 2) the simple methods for predicting wind profile parameters, and 3) the applications of wind profile in studies of tree physiology, forest ecology and management, and the detail ecological effects of wind on tree growth.     

Comparison of fixed area and distance sampling methods in open forests: case study of Zagros Forest,Iran

The main aim of this study was to evaluate methods for fixed area and distance sampling in the Zagros open forest area in western Iran.Basic forest management and planning required appropriate quantitative and qualitative information.Two sampling methods were compared on the basis of the actual means of characteristics derived from the 100 % survey.In total,37 sampling plots were systematically installed with a grid of 100 m 9 100 m in the study area.Density,crown canopy,and basal area of the stands were measured.The 100 % survey showed that tree density above 12.5 cm diameter at breast height was 68.04 stem ha~(-1),basal area was 15.16 m~2ha~(-1) and crown canopy percentage was 35.71 % ha~(-1).The values for the traits determined by the two sampling methods differed significantly(P=0.05).When the time required for the methods was compared,transect sampling required less than systematic-random sampling.Therefore,the transect sampling method was the more economical method for the Zagros open forests.The transect sampling method was statistically defensible and practical for quantitating characteristics of the Zagros open forests.     

干旱半干旱区山地森林的水分调节功能

处于中国西北干旱半干旱区的山地森林以独特的水文作用成9为山前平原及川区绿洲生态经济系统稳定发展的基础。以典型山地森林祁连山水源涵养林的主要群落青海云杉林为例，通过长期定位观测研究森林调节小气候的水文规律及功能，揭示了森林对降水的分配调节作用。森林通过林冠层截留降水使到达林内的降水量减少、强度降低、雨滴对地面的冲击减弱，避免林内发生地表径流引起水土流失；森林通过林冠层遮蔽减弱太阳辐射降低了林内土壤蒸发，保持林内湿度较高、土壤含有较多水分，为喜湿耐荫植物生长发育创造了适宜的阴湿环境，并提供了充足的水分条件；森林的蒸腾发散使同一高度林区上空的湿度比草地或裸地高，改变了局地大气环流，为降水形成准备了物质条件，起到了增加林区降水的作用。     

Assessing rates of forest change and fragmentation in Alabama,USA, using the vegetation change tracker model

Forest change is of great concern for land use decision makers and conservation communities. Quantitative and spatial forest change information is critical for addressing many pressing issues, including global climate change, carbon budgets, and sustainability. In this study, our analysis focuses on the differences in geospatial patterns and their changes between federal forests and nonfederal forests in Alabama over the time period 1987–2005, by interpreting 163 Landsat Thematic Mapper (TM) scenes using a vegetation change tracker (VCT) model. Our analysis revealed that for the most part of 1990 s and between 2000 and 2005, Alabama lost about 2% of its forest on an annual basis due to disturbances, but much of the losses were balanced by forest regeneration from previous disturbances. The disturbance maps revealed that federal forests were reasonably well protected, with the fragmentation remaining relatively stable over time. In contrast, nonfederal forests, which are predominant in area share (about 95%), were heavily disturbed, clearly demonstrating decreasing levels of fragmentation during the time period 1987–1993 giving way to a subsequent accelerating fragmentation during the time period 1994–2005. Additionally, the identification of the statistical relationships between forest fragmentation status and forest loss rate and forest net change rate in relation to land ownership implied the distinct differences in forest cutting rate and cutting patterns between federal forests and nonfederal forests. The forest spatial change information derived from the model has provided valuable insights regarding regional forest management practices and disturbance regimes, which are closely associated with regional economics and environmental concerns.     

Breeding bird community composition in different successional vegetation in the montane coniferous forests zone of Taiwan

To examine the relationship between forest succession following fire and the composition of bird communities, we investigated the vegetation structure, bird population density, foraging behavior and guild structure in bamboo grasslands (11 years since the last fire), pine savanna (41 years), pine woodland (58 years), old-growth hemlock forest (never burned), and old-growth spruce forest (never burned) in the Tatachia area of central Taiwan. Canopy height, total foliage cover, tree density, total basal area of tree, total basal area of snags, foliage height diversity, and tree species richness all increased with successional age. However, shrub cover peaked in intermediate successional stages. The vertical profile of foliage cover was more diverse in later successional forests, which had more breeding bird species and ecological guilds. All the breeding bird species recorded in early and intermediate stages were also found distributed in the late successional forests. Because Taiwan has high precipitation and humidity, and most forest fires in Taiwan are caused by human activities, forest fires and large areas of early successional vegetation were probably rare in the mountain areas of Taiwan prior to the arrival of humans. Therefore, bird species have not had enough time to adapt to areas with early or intermediate successional vegetation. Moreover, late successional forests host all the major plant species found in the early and intermediate stages and have higher foliage height diversity index, which was positively correlated with the bird species richness and bird species diversity index in this study. As a result, all breeding bird species and guilds in the area can be found in late successional forests. Efforts for conserving avian diversity in Taiwan should focus on protecting the remaining native old-growth forests.     

非公有制人工商品林限额采伐管理制度创新探讨

基于林农的视角,以福建省闽侯县为例,探讨非公有制商品林限额采伐管理制度创新。提出以市场经济体制、服务型政府新视角及以人为本为价值取向;对公益林和商品林分别采取不同的采伐管理制度,科学合理地划定生态公益林,遵循林农意愿编制人工商品林经营方案,简化非公有制人工商品林的审批手续,取消育林基金改征环境绿化税,严格实行凭证运输制度,建立林地档案,公开林业生产要素信息等思路。     

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...     

中美国有林森林经营计划制定比较研究

美国是世界上林业较发达国家之一,国有林经营有着悠久的历史。文中对比分析了中美国有林森林经营计划的发展历程、法律基础、制定过程以及森林计划内容。针对我国国有林森林计划中的不足,提出:1）加强国有林森林经营计划制定中的公众参与;2）细化国有林管理,重视可获取的最佳科学信息;3）加强计划评估、制定、监测的适应性管理;4）以可持续经营为核心制定国有林森林经营计划;5）转换立法思路,完善国有林相关法律法规。     

Theoretical perspectives for enhancing biological diversity in forest ecosystems in Europe

Forests produce a great variety of wood and non-wood products and services. For a long time foresters have understood themselves to be guarantors for the sustainable management of forests, particularly for the long-term production of timber. In the context of the environmental movement of the 1960s, the timber-oriented perception of forests was challenged by an ecosystem orientation, focusing on the maintenance and enhancement of biological diversity. Since then, forest policy has been characterised by two opposing positions, or camps, both of whom pursue their interests in the formulation and implementation of policies for forests. Both sides seek to ensure biological diversity in forests by quite a number of national, European and international legally binding instruments and non-legally binding initiatives for forests. As it is too early for evaluation studies on the outcome of these policy means, an assessment of the chance of a compromise between the two camps is sought on theoretical grounds using the rational choice theory, common-property regimes, and the belief systems approach. All three approaches provide some theoretical perspectives for enhancing biological diversity in forests: the rational choice approach by means of basic principles of national forest programmes, the common-property regimes by the internalisation of conflicting forest uses, and the belief systems approach by the probability of changes in ideological beliefs.