Publications
NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.
2010
Authors
Carina E. Johansen Christian Lydersen Paul E. Aspholm tore Haug Kit M. KovacsAbstract
No abstract has been registered
Authors
David Bredström Petrus Jönsson Mikael RönnqvistAbstract
A cost-efficient use of harvesting resources is important in the forest industry. The main planning is carried out in an annual resource plan that is continuously revised. The harvesting operations are divided into harvesting and forwarding. The harvesting operation fells trees and puts them in piles in the harvest areas. The forwarding operation collects piles and moves them to storage locations adjacent to forest roads. These operations are conducted by machines (harvesters, forwarders and harwarders), and these are operated by crews living in cities/villages that are within some maximum distance from the harvest areas. Machines, harvest teams and harvest areas have different characteristics and properties and it is difficult to find the best possible match throughout the year. The aim of the planning is to find an annual plan with the lowest possible cost. The total cost is based on three parts: production cost, traveling cost and moving cost. The production cost is the cost for the harvesting and forwarding. The traveling cost is the cost for driving back and forwards (daily) from the home base to the harvest area and the moving cost is associated with moving the machines and equipment between harvest areas. The Forest Research Institute of Sweden (Skogforsk), together with a number of Swedish forest companies, has developed a decision support platform for the planning. One important element of this platform is that it should find high-quality plans within short computational times. One central element is an optimization model that integrates the assignment of machines to harvest areas and schedules the harvest areas during the year for each machine. The problem is complex and we propose a two-phase solution method where, first, we solve the assignment problem and, second, the scheduling. In order to be able to control the scheduling in phase 1 as well, we have introduced an extra cost component that controls the geographical distribution of harvest areas for each machine in phase 1. We have tested the solution approach on a case study from one of the larger Swedish forest companies. This case study involves 46 machines and 968 harvest areas representing a log volume of 1.33 million cubic meters. We describe some numerical results and experience from the development and tests.
Abstract
Information retrieval from spatiotemporal data cubes is key to earth system sciences. Respective analyses need to consider two fundamental issues: First, natural phenomena fluctuate on different time scales. Second, these characteristic temporal patterns induce multiple geographical gradients. Here we propose an integrated approach of subsignal extraction and dimensionality reduction to extract geographical gradients on multiple time scales. The approach is exemplified using global remote sensing estimates of photosynthetic activity. A wide range of partly well interpretable gradients is retrieved. For instance, well known climate-induced anomalies in FAPAR over Africa and South America during the last severe ENSO event are identified. Also, the precise geographical patterns of the annual–seasonal cycle and its phasing are isolated. Other features lead to new questions on the underlying environmental dynamics. Our method can provide benchmarks for comparisons of data cubes, model runs, and thus be used as a basis for sophisticated model performance evaluations.
Authors
Miguel D. Mahecha Markus Reichstein Nuno Carvalhais Gitta Lasslop Holger Lange Sonia I. Seneviratne Rodrigo Vargas Christof Ammann M.Altaf Arain Alessandro Cescatti Ivan A. Janssens Mirco Migliavacca Leonardo Montagnani Andrew D. RichardsonAbstract
The respiratory release of carbon dioxide (CO2) from the land surface is a major flux in the global carbon cycle, antipodal to photosynthetic CO2 uptake. Understanding the sensitivity of respiratory processes to temperature is central for quantifying the climate–carbon cycle feedback. We approximated the sensitivity of terrestrial ecosystem respiration to air temperature (Q10) across 60 FLUXNET sites with the use of a methodology that circumvents confounding effects. Contrary to previous findings, our results suggest that Q10 is independent of mean annual temperature, does not differ among biomes, and is confined to values around 1.4 ± 0.1. The strong relation between photosynthesis and respiration, by contrast, is highly variable among sites. The results may partly explain a less pronounced climate–carbon cycle feedback than suggested by current carbon cycle climate models.
Abstract
No abstract has been registered
Authors
Stig Strandli Gezelius Jesper Raakjær Troels Jacob HeglandAbstract
No abstract has been registered
Abstract
Protected Landscapes (PLs) are increasingly used in Norway to conserve cultural (human modified) landscapes. In many cases the maintenance of agricultural activities in PLs is required to preserve landscape character. Whilst research exists on land conservation policies in general, the particular effects of PL on management and adjustment of the farms involved have not received attention in the literature. We present results from a questionnaire sent to owners of agricultural land within PLs in Norway. Whilst landowners were divided upon the effects of PLs on farm management, the economic situation of the farm was little affected. Furthermore, changes in farm management after the establishment of a PL did not seem to have been driven by the establishment of the PLs per se. Most importantly, farm management changes were related to potential options to develop the farm and its land. A statistical model showed that PL-farms did not differ significantly from farms outside PL in the development of their land use or animal husbandry. Our findings thus indicate that the establishment of PL played a minor role as a driving force of changes in farm management and farm income.
Abstract
Traditional wood preservatives based on biocides are effective against wood-deteriorating organisms because of their toxicity. By contrast, modified woods are non-toxic by definition. To investigate the efficiency of various wood modifications, quantitative real-time polymerase chain reaction (qPCR) was used to profile the DNA amounts of the white-rot fungus Trametes versicolor (L.) [Lloyd strain CTB 863 A] during an 8-week-long growth period in treated Pinus sylvestris (L.) sapwood. The studied wood was modified by acetylation, furfurylation, and thermal treatment. The traditional wood preservatives bis-(N-cyclohexyldiazeniumdioxy)-copper (Cu-HDO) and chromated copper arsenate (CCA) were used as references, whereas untreated P. sylvestris (L.) sapwood served as a control. The maximum levels of fungal DNA in native wood occurred at the end of the experiment. For all wood treatments, the maximum fungal DNA level was recorded after an incubation period of 2 weeks, followed by a decline until the end of the trial. For the preservative-treated woods, Cu-HDO showed the lowest level of fungal DNA throughout the experiment, indicating that exploratory hyphal growth is limited owing to the phytotoxicity of the treatment. The other treatments did not inhibit the exploratory hyphal growth phase. We conclude that qPCR studies of hyphal growth patterns within wood should provide a powerful tool for evaluating and further optimizing new wood protection systems.
Authors
Tuula Kantola Mikko Vastaranta Xiaowei Yu Paivi Lyytikainen-Saarenmaa Markus Holopainen Mervi Talvitie Sanna Kaasalainen Svein Solberg Juha HyyppäAbstract
Climate change and rising temperatures have been observed to be related to the increase of forest insect damage in the boreal zone. The common pine sawfly (Diprion pini L.) (Hymenoptera, Diprionidae) is regarded as a significant threat to boreal pine forests. Defoliation by D. pini can cause severe growth loss and tree mortality in Scots pine (Pinus sylvestris L.) (Pinaceae). In this study, logistic LASSO regression, Random Forest (RF) and Most Similar Neighbor method (MSN) were investigated for predicting the defoliation level of individual Scots pines using the features derived from airborne laser scanning (ALS) data and aerial images. Classification accuracies from 83.7% (kappa 0.67) to 88.1% (kappa 0.76) were obtained depending on the method. The most accurate result was produced using RF with a combination of data from the two sensors, while the accuracies when using ALS and image features separately were 80.7% and 87.4%, respectively. Evidently, the combination of ALS and aerial images in detecting needle losses is capable of providing satisfactory estimates for individual trees.
Authors
Svein SolbergAbstract
Four alternative airborne laser scanning (ALS) canopy penetration variables were compared for their suitability for mapping of gap fraction, leaf area index and disturbances in a Scots pine forest. The variables were based on either echo counting or intensity, and on either first or first and last echoes. ALS data and field-measured gap fraction and effective leaf area index (LAIe) were gathered before and after a severe insect defoliation by pine sawflies. LAIe is a commonly used form of leaf area index that is mathematically derived from gap fraction, and includes the areas of foliage, branches and trunks, and which is not corrected for the clumping of foliage. The ALS penetration variables were almost equally strongly related to field-measured gap fraction and LAIe. The estimated slopes in the LAIe models varied from 0.94 to 2.71, and had coefficient of determination R 2 values of 0.92–0.94. They were strongly correlated to each other (R 2 values of 0.95–0.98) and agreed fairly well for temporal changes of LAIe during the summer and the insect defoliation (R 2 values of 0.82–0.95). Counting of first and last echoes produced penetration rates close to the gap fraction, and this penetration variable was able to penetrate tree crowns. Ground-only echoes represented mostly between-tree gaps, and canopy-first-ground-last pulses represented mostly within-canopy gaps. However, the penetration variables based on first and last echoes suffered from the problem that a second echo might be impaired both in low and in tall canopies. In low canopies, two adjacent echoes from the same pulse would be too close in time to be separated by the sensor, while in tall canopies the pulse might apparently be fragmented down through the canopy. The intensity-based penetration variables needed to be supplemented with reflectance values, or at least the ratio between reflectance of the canopy and the ground, and this ratio was estimated from the data. The study demonstrated that one might be able to distinguish between disturbance types, e.g. between defoliation and cutting, by comparing alternative ALS penetration variables. Insect defoliation was dominated by an increase in within-canopy gaps and, correspondingly, the fraction of partly penetrating canopy-first-ground-last pulses. Tree removals from cutting were dominated by increases in between-tree gaps and the corresponding fraction of ground-only pulses.