Hampus Holmström

Simultaneous Estimations of Forest Parameters using Aerial Photograph Interpreted Data and the k Nearest Neighbour Method

Information about the state of the forest is of vital importance in forest management planning. To enable high-precision modelling, many forest planning systems demand input data at the single-tree level. The conventional strategy for collecting such data is a plot-wise field inventory. This is expensive and, thus, cost-efficient alternatives are of interest. During recent years, the focus has been on remote sensing techniques. The k nearest neighbour (kNN) estimation method is a way to assign plot-wise data to all stands in a forest area, using remotely sensed data in connection with a sparse sample of field reference plots. Plot-wise aerial photograph interpretations combined with information from a stand register were used in this study. Nearness to a reference plot was decided upon using a regression transform distance. Standing stem volume was estimated with a relative root mean square error (RMSE) equal to 20% at the stand level, while age could be estimated with a RMSE equal to 15%. A cost-efficient data-capturing strategy could be to assign plot data with the presented kNN method to some types of forest, while using traditional field inventories in other, more valuable, stands.

Carbon balances of bioenergy systems using biomass from forests managed with long rotations: bridging the gap between stand and landscape assessments

Studies report different findings concerning the climate benefits of bioenergy, in part due to varying scope and use of different approaches to define spatial and temporal system boundaries. We quantify carbon balances for bioenergy systems that use biomass from forests managed with long rotations, employing different approaches and boundary conditions. Two approaches to represent landscapes and quantify their carbon balances – expanding vs. constant spatial boundaries – are compared. We show that for a conceptual forest landscape, constructed by combining a series of time‐shifted forest stands, the two approaches sometimes yield different results. We argue that the approach that uses constant spatial boundaries is preferable because it captures all carbon flows in the landscape throughout the accounting period. The approach that uses expanding system boundaries fails to accurately describe the carbon fluxes in the landscape due to incomplete coverage of carbon flows and influence of the stand‐level dynamics, which in turn arise from the way temporal system boundaries are defined on the stand level. Modelling of profit‐driven forest management using location‐specific forest data shows that the implications for carbon balance of management changes across the landscape (which are partly neglected when expanding system boundaries are used) depend on many factors such as forest structure and forest owners’ expectations of market development for bioenergy and other wood products. Assessments should not consider forest‐based bioenergy in isolation but should ideally consider all forest products and how forest management planning as a whole is affected by bioenergy incentives – and how this in turn affects carbon balances in forest landscapes and forest product pools. Due to uncertainties, we modelled several alternative scenarios for forest products markets. We recommend that future work consider alternative scenarios for other critical factors, such as policy options and energy technology pathways.

Simulated effects of browsing on the production and economic values of Scots pine (Pinus sylvestris) stands

ABSTRACT Effects of browsing damage on Scots pine (Pinus sylvestris) production and economic value were simulated on sites ranging in fertility from relatively poor to relatively high. Effects of browsing damage on growth and survival after trees had exceeded browsing-height were estimated using data from a browsing study. Stem lists were produced when stems had reached a height of about 4 m. Individual tree data were then imported into the Heureka simulation system to generate predictions about stand production and economic value. Six browsing levels were simulated: 0, 2, 5, 10, 15 and 27% browsing damage annually. The 2% and 5% browsing levels had only minor effects on production, whilst higher browsing levels significantly reduced production. However, the effect on economic value was more pronounced and even the 2% browsing level had significant effects on estimated land expectation values. Results from this simulation may support discussions about acceptable browsing levels in young Scots pine stands.

Using value functions to elicit spatial preference information

Decision making in forest planning often involves situations, where the value of the stand is dependent on its location or the properties of the stands nearby. Often the most intuitive tool to describe spatial objectives and outcomes is a visual map. However, evaluating and comparing different maps may prove a considerable cognitive burden, especially over large areas and in long-term planning. In this study, we investigate the use of value functions for eliciting spatial preference information from maps. Our case study is part of a project investigating the possibilities of increasing broadleaf-tree-dominated habitats in a northern Swedish landscape. The experts involved in the project evaluated maps showing different fragmentation patterns. Different spatial indices were then calculated for the maps, and expert evaluations were used to sketch value functions describing the preferred fragmentation level. The approach was found to be a quick way of translating spatial preferences into numerical values and conceptualizing the relatively abstract concept of fragmentation in the landscape. Furthermore, the results show that the choice of a certain fragmentation index has a crucial effect on the value function.

Riparian forests along small streams on managed forest land in Sweden

ABSTRACT This study investigated characteristics of riparian forests on managed forest land in Sweden. Forest and site characteristics were inventoried at three sites, located along a south to north gradient, in 139 transects placed perpendicular to 38 stream reaches (<10 m wide), in forests representing the age classes 0–25, 26–75 and >75 years. Starting from the stream edge, the 30 m long transects were divided into three zones: 0–5, 5–15 and 15–30 m. The stem volumes of Pinus sylvestris L., Picea abies (L.) H. Karst, Betula spp. and broadleaved trees, the basal area share of Alnus spp., the stem density, and Sphagnum spp. coverage all showed an effect of zone (p < 0.05). The 0–5 m zone had the lowest volume of P. sylvestris and the highest volumes of P. abies, Betula spp. and broadleaved trees as well as the highest total stem density and basal area share of Alnus spp. Some characteristics of the northernmost site tended to differ from the two sites located in south-central Sweden. Knowledge of the characteristics of riparian forests as found in this study could aid long-term forestry planning and improve precision in the preservation and development of riparian forests with certain qualities.

Simulation of the long-term effects of different strategies for precommercial thinning in Pinus sylvestris

ABSTRACT The influence of the intensity and timing of precommercial thinning (PCT) on stand development and financial return was studied in Scots pine stands. Functions describing the early development of the stand structure after PCT were developed. The functions were based on 195 plots within 41 PCT experiments in Sweden. The dimension distribution of the established stand was estimated and used as input to the decision support system Heureka, to simulate the stand development until final felling. The studied treatments included PCT to 1000, 2000 and 3000 stems ha−1 at mean heights of 2, 4 and 6 m. Separate simulations were carried out for different site fertilities. Mean annual volume increment increased with increasing number of stems after PCT whereas the timing of PCT had only a small effect. The land expectation value (LEV) generally decreased with increasing mean height at PCT, primarily because of the increased cost of PCT. LEV decreased with increasing number of stems after PCT at low fertility sites whereas only minor differences were found for PCT to 1000 and 2000 stems ha−1 at medium and high fertility sites. The general pattern persisted when different scenarios of future timber quality were simulated.