Janne Uuttera

Comparison of percentile based prediction methods and the Weibull distribution in describing the diameter distribution of heterogeneous Scots pine stands.

Abstract The goal of this study was to compare percentile based distribution methods and the Weibull distribution method in predicting the stand characteristics of forests with great variability in their diameter distribution. Stand structure characteristics were compared between thinned and unthinned stands dominated by Scots pine. The thinned forests were located in eastern Finland, while the unthinned natural forests were located in Republic of Karelia and Leningrad district, Russian Federation. Each data sets included 49 stands. The diameter distributions were more heterogeneous in the unthinned stands. Most of the thinned stands formed unimodal distributions. Among the unthinned stands, decreasing, multi-modal and irregular forms of diameter distributions were also found. In these data, percentile based distribution methods proved to be considerably more effective in predicting the diameter distribution than the Weibull distribution method. With the percentile based distribution method it was also possible to reproduce considerably varying shapes of diameter distributions.

Determination of the spatial distribution of trees from digital aerial photographs

Abstract This study examined the possibilities of using computerized digital aerial photograph interpretation in determining the spatial distribution of trees. The material of the study included eight mapped stands in the municipality of Hyytiala (61°50′N and 24°18′E), in southern Finland. The aerial photographs used were taken in June 1995 at a scale of 1:5000. Two approaches for determining the spatial pattern of trees were used. Firstly, in the point-process based approach used in this study, the individual trees in the digital aerial photograph were segmented by a robust segmentation method, based on recognition of the pattern of tree crowns with sub-pixel accuracy. Secondly, the crown coverage was determined by region growing segmentation combined with active surface representation. The significance of the differences in the means of image coverage pattern indices between the various spatial distribution categories was tested with one-way variance analysis. Because the process misclassified clustered spatial patterns as regular patterns, and regular patterns as random patterns, the usability of digital aerial photographs seems to be limited for the point-process based determination of the spatial pattern of trees if the scale is 1:5000 or less. When image coverage pattern indices were applied, the differences in the means of the spatial distribution categories proved not to be clearly statistically significant due to the great variation within classes. However, interpretation of crown coverage could have applications in practical forestry due to the low resolution requirements for the images used.

The structure of forest stands in virgin and managed peatlands: a comparison between Finnish and Russian Karelia

Abstract This study investigated the changes caused by management, including drainage and thinnings, in peatland forest stand structure. Drained peatland sites in Finnish North Karelia were compared within the same type groups and nutrient status levels of virgin peatlands in the Republic of Karelia, the Russian Federation. The variables studied, which depict stand structure variation, included: (1) the diameter of the median tree; (2) the range of sampled diameters; (3) the basal area of the stand; (4) the estimated number of tree storeys; and (5) the number of the tree species. The number of tree storeys was determined through non-parametric Kernel estimation. Over a long duration, management smooths the natural multi-modal structure of virgin peatland stocking by decreasing the variation in size-distribution. Management also changes the natural tree species dynamics on peatland sites by providing a competitive advantage to the tree species, which adjust best to the changed growing conditions. These species begin to dominate the habitat and reduce the species diversity. The effect of recent thinnings and cleaning cuttings on the forest structure is dependent upon fertility of the site and the stage of the forest stock at the moment of silvicultural operation. Cleaning cuttings may have also an increasing effect on the structural diversity of peatland forest stand.

Impact of forest management history on the state of forests in relation to natural forest succession Comparative study, North Karelia, Finland vs. Republic of Karelia, Russian Federation

Abstract The purpose of this study was to examine the impact of the recent history of forest management on the state and structure of forests. Comparisons were made between test areas in the south-eastern part of North Karelia, Finland, and the western part of the Republic of Karelia, Russian Federation. The test areas are located in the same climatic region, but their history of forest management has been considerably different during the past 50 years. They therefore also provide possibilities for wider international observations. The total biodiversity of a large forest area consists of the existence and area distribution of the forest succession stages. Within these stages the stand structure reflects the processes of the small natural vegetation succession cycle of boreal coniferous forests. Considering the factors that maintain potential forest biodiversity, it is clearly seen that the forests in the Republic of Karelia are in a more natural state than those of North Karelia. However, considering the natural fire ecology of the region, both test areas have a paucity of old forests. When examining the stand characteristics reflecting the small succession cycle within habitats, the forests in the Republic of Karelia have more of the crucial factors typical of species classified as threatened in Finland. If mimicking the natural dynamics of boreal coniferous forests is taken as a goal of forest management, the desired habitat diversity can be achieved only by maintaining all stages of the large vegetation succession cycle. Within the succession stages of young, middle-aged and mature stands, structural variation and variation of tree species composition should be increased. This can be achieved by means of forest management and forestry operations, but these policies, on the other hand, may decrease wood production.

Spatial harvest scheduling approach for areas involving multiple ownership

Abstract This study presents a practical harvest scheduling approach for multiple ownership planning. The approach has both spatial and non-spatial goals, namely, a spatial landscape-level goal to cluster ecologically valuable resources is considered simultaneously with timber production goals. Harvest scheduling is based on the location of the stand, on one hand, and on an economic variable depicting the cutting maturity of the stand, on the other hand. Proximity to valuable resources decreases the likelihood that the stand is cut. Therefore, harvests tend to be located outside potential resource clusters with small and isolated economically mature stands being cut first. In the application of the approach the landscape-level spatial objective was to cluster old forest stands (age⩾80) and simultaneously maintain a predefined cutting volume. A stands economic cutting maturity was measured with value increment percentage. In the top-down application of the approach the timber harvest target was specified only for the whole planning area. In the bottom-up application it was specified separately for individual holdings, aiming at promoting the acceptability of the plan. The presented approach was clearly able to cluster old forest patches. In the case study area, the mean size of old forest patches increased from 3.4 to 5.7 ha in 30 years in the top-down plan, and to 4.6 ha in the bottom-up plan. An application of the current planning practice (referred to as the reference plan) decreased the mean patch size to 2.9 ha. The presented approach is easy to apply in forest planning practice.

Differences in the structure of primary and managed forests in East Kalimantan, Indonesia

Abstract This study investigated if primary and managed forests of Southeast Asian tropical forests can be distinguished by quantitative forest structure characteristics, which are easy to measure in the field. Such a method could help select analytically and objectively small fragments of primary forests for conservation purposes within planning areas. The test area was located close to Tanah Grogot in the southern part of East Kalimantan, Indonesia. The field inventory of the test area was made with systematic cluster sampling. Altogether, the data included 304 clusters with 6475 sample plots, which included 47 386 measured trees. Differences in the structure between primary and managed forests were analyzed with quantitative characteristics: number of stems per hectare; total volume per hectare; Shannons index of tree species richness; Hills index of tree species richness and evenness of the abundances; Q-statistics of the cumulative tree species abundance curves; average shape of diameter distributions; and peaks of smoothed diameter distributions. Characteristics of the forest structure were investigated in the whole data, by tree species classes, diameter classes, and forest management status classes. The results of the study show that it is possible to find a set of easily measurable characteristics that reveal the changes caused by the management in tropical forests. However, because management affects mostly the economically and also ecologically valuable large dipterocarps, it is reasonable to examine the conducted changes separately by diameter classes and preferably by different tree species classes rather than in the tree data as a whole.

Decreasing the fragmentation of old forests in landscapes involving multiple ownership in Finland: economic, social and ecological consequences

The management of biological diversity at the landscape level in Finland is complicated by the relatively small size of the holdings and the fact that the habitats of species do not necessarily follow the holding borders. Therefore, there is a great need to develop such forest-planning approaches that aim at solving the problems that some species have faced due to modern forestry, including the fragmentation of old forests. One way to deal with fragmentation is to aggregate old forests into larger patches, a goal that may be achieved by excluding some areas from forestry operations or by restricting the intensity of treatments. In a planning area under multiple ownership, the sizes, shapes and relative locations of set-aside areas are important, since they affect the social equity of the proposed forest plans. In this study, the effects of two conflicting goals, i.e. the improvement of old-forest patterns, and the equal participation of forest owners were studied in a privately owned forest area in Finland. This was made possible through the examination of the consequences of alternative strategies to delineate areas set aside. The two main results of the study were, first, that it is difficult to reach these goals simultaneously, and, second, the time interval relevant in the management planning of private forestry is quite short with respect to efforts to change landscape structure significantly. However, in real planning situations, it is important to specify the locations of forest holdings whose owners are willing to acknowledge biodiversity values above the level defined in the legislation. In addition, ecologically important areas should be located and connected to the above information. According to the results of this study, it seems that a compensation system would facilitate the restructuring of the forest landscapes towards an ecologically enhanced structure.