Bengt Jonsson

A forest inventory method based on density‐adapted circular plot size

A method using sample plots with “fixed number of stems, random circular plot size”; in the stand‐description phase was studied both theoretically and empirically in several regards; it was also developed for practical purposes. We call this inventory method “the density‐adapted method”;. The advantage of this method, compared with the currently employed method, is that the work per sample plot is proportional to the amount of useful information gathered per sample plot. In simulation studies, “forests”; are simulated, and the density‐adapted method is then used in these “forests”;. Generally speaking, the bias amounts to a few percent in the realistic forests that are simulated. The bias is sometimes positive and sometimes negative. Positive bias results from a high degree of clustering, negative from high evenness. In actual stand structures, the density‐adapted method has been proven to produce an insignificant amount of bias. Long‐term prognoses in conjunction with timber assessment calculations have ...

Thinning response functions for single trees of pinus sylvestris L. and picea abies (L.) karst

Regression functions are presented for estimating the thinning response of the annual‐ring‐width increment in single trees of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.). The thinning response of a tree is defined as the ratio between the actual annual‐ring width and the corresponding assumed annual‐ring width unaffected by thinning. Optional growth models are presented which isolate the thinning response. The models allow for a quantitative determination of the role of thinning within the complex growth process. Given knowledge of the time, intensity, and method of the thinnings, the models allow estimation of the total response to thinning. This response is influenced by all previous thinnings—active as well as natural, induced by crowding—in the stand in question.

Stand establishment and early growth of planted Pinus sylvestris and Picea abies related to microsite conditions

Stand establishment and early height growth of planted Scots pine and Norway spruce trees were investigated in relation to microsite conditions. The 20 - year old pure and mixed stands studied are located on a six hectare experimental site with a harsh climate at high altitude in Swedish Lapland. Observations were made on 360 circular sample plots, each with a 3 m radius, laid out in a systematic pattern over the site. The site conditions were measured separately for each sample plot and were related to seedling survival and mortality, height, and height increment of single trees on individual sample plots. The results show that seedling survival and height increment of single trees are correlated with ground vegetation, frost holes, logging residues and stump occurrence at the local level of 3 m circular plots, as well as with local elevation and tree species mixture. In the stand establishment phase, Scots pine was found to be more sensitive to site conditions than Norway spruce. For Scots pine, this wa...

PIXE as a tool for determination of acidified forests

Abstract The trace element content along tree cores of Norway spruce (Picea abies), collected at the experimental area E67 Faxboda, has been analysed by means of PIXE. Trace element content profiles along tree cores from trees grown on plots exposed to dolomite liming, sulphuric acid acidification and on reference plots have been determined. Changes, correlated to the acidification, have been observed. Calcium and the manganese/calcium ratios within a sample possess strong correlations to the artificial acidification at the experimental area. Local factors, like a high calcium content, are likely to influence the result.

Analysis of trace element content in tree cores by PIXE

Abstract Nine tree cores of 8 to 12 cm in length from spruce have been scanned using PIXE as a microsonde of millimetre size for the contents and profiles of trace elements. Eighteen elements have been found at ppm to 1000 ppm level. The preliminary statistical analysis of the raw data led to some interesting results. The calcium content decreases with increasing age of the tree. There is a strong correlation between the calcium content and the manganese and strontium content. Several of the core samples have high concentration peaks within one or a few annual rings for the elements iron, titanium, copper, lead and zinc. All peaks can be correlated to a rapid decrease in the growth rate of the tree.

ANALYSIS OF TREE SAMPLES FROM AN ACIDIC AND A LIMED ENVIRONMENT BY MEANS OF PIXE

Three tree core samples of Norway spruce (Picea Abies) have been analysed by PIXE. The concentration profiles for 17 elements heavier than sodium have been determined by means of one PIXE measurement every 2 mm along the samples. The samples were collected at Faxboda, an experimental area north of Uppsala where artificially acidified and limed environmental experiments are made. One sample from each of an acidified, a limed and a reference area has been collected. The main interest is focused on potassium, calcium, manganese, iron, copper and zinc. All three samples have about the same concentration profile in the heartwood. Large differences are observed in the sapwood. In the sample from the limed area the calcium content is much higher and the iron and chromium. contents are lower than in the sample from the reference area. In the sample from the acidified area the calcium and potassium contents are lower and the manganese, iron and chromium contents are much higher than in the sample from the referenc...

Optimal harvesting time in single‐ and multiple‐purpose forest management

In single‐purpose timber producing forestry, the optimal harvesting time occurs when the net revenue on the stumpage value equals the cost of renting the land (the land‐use cost) minus the change in land value. In multiple‐purpose forestry, the optimal time for harvesting occurs when the sum of the net revenues of the stumpage value and the amenity value is equal to the cost of renting the land minus the change in the land value. This land value is the sum of the land value for timber production and the land value for amenity services in the case of combined management of timber and amenity‐resources.