[Show abstract][Hide abstract] ABSTRACT: Wood is the main terrestrial biotic reservoir for long-term carbon sequestration, and its formation in trees consumes around 15% of anthropogenic carbon dioxide emissions each year. However, the seasonal dynamics of woody biomass production cannot be quantified from eddy covariance or satellite observations. As such, our understanding of this key carbon cycle component, and its sensitivity to climate, remains limited. Here, we present high-resolution cellular based measurements of wood formation dynamics in three coniferous forest sites in northeastern France, performed over a period of 3 years. We show that stem woody biomass production lags behind stem-girth increase by over 1 month. We also analyse more general phenological observations of xylem tissue formation in Northern Hemisphere forests and find similar time lags in boreal, temperate, subalpine and Mediterranean forests. These time lags question the extension of the equivalence between stem size increase and woody biomass production to intra-annual time scales. They also suggest that these two growth processes exhibit differential sensitivities to local environmental conditions. Indeed, in the well-watered French sites the seasonal dynamics of stem-girth increase matched the photoperiod cycle, whereas those of woody biomass production closely followed the seasonal course of temperature. We suggest that forecasted changes in the annual cycle of climatic factors may shift the phase timing of stem size increase and woody biomass production in the future.
[Show abstract][Hide abstract] ABSTRACT: The quantification of cambial growth over short time periods has been hampered by problems to discern between growth and the swelling and shrinking of a tree stem. This paper presents a model, which separates cambial growth and reversible water-potential induced diurnal changes from simultaneously measured whole stem and xylem radial variations, from field-measured Scots pine trees in Finland. The modelled growth, which includes osmotic concentration changes, was compared to (direct) dendrometer measurements and microcore samples. In addition, the relationship of modelled growth and dendrometer measurements to environmental factors were analysed. Results showed that the water-potential induced changes of tree radius were successfully separated from stem growth. Daily growth predicted by the model exhibited a high correlation with the modelled daily changes of osmotic concentration in phloem, and a temperature dependency in early summer. Late summer growth saw higher dependency on water availability and temperature. Evaluation of the model against dendrometer measurements showed that the latter masked a true environmental signal in stem growth due to water-potential induced changes. The model provides better understanding of radial growth physiology and offers potential to examine growth dynamics and changes due to osmotic concentration, and how the environment affects growth.
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Full-text · Article · Mar 2015 · Plant Cell and Environment
[Show abstract][Hide abstract] ABSTRACT: The properties of wood and wood tracheids from trees growing in peatland stands are still insufficiently known. The long-term
effects of thinning on wood and tracheid properties of Scots pine (Pinus sylvestris L.) were investigated in two thinning experiments on peatland sites in central Finland. The two sites were ditched for the
first time in 1958 and 1973, and thinning experiments were established in 1987 and 1993, respectively. Thinning increased
the basal area increment of the remaining trees by 20 per cent. No differences between the trees that were growing on the
thinned plots and those that were growing on the unthinned control plots were found in the latewood proportion, wood density,
tracheid diameter, cell wall thickness and tracheid length. Moreover, the wood and tracheid properties did not differ markedly
from those of corresponding material originating from mineral soil sites. The results confirm the previous results on mineral
soils, which showed that an increasing availability of resources primarily increases the rate of tracheid production but has
no major effects on wood and tracheid properties.
[Show abstract][Hide abstract] ABSTRACT: The control of tree growth vs environment by carbon sources or sinks remains unresolved although it is widely studied. This study investigates growth of tree components and carbon sink–source dynamics at different temporal scales.We constructed a dynamic growth model ‘carbon allocation sink source interaction’ (CASSIA) that calculates tree-level carbon balance from photosynthesis, respiration, phenology and temperature-driven potential structural growth of tree organs and dynamics of stored nonstructural carbon (NSC) and their modifying influence on growth. With the model, we tested hypotheses that sink demand explains the intra-annual growth dynamics of the meristems, and that the source supply is further needed to explain year-to-year growth variation.The predicted intra-annual dimensional growth of shoots and needles and the number of cells in xylogenesis phases corresponded with measurements, whereas NSC hardly limited the growth, supporting the first hypothesis. Delayed GPP influence on potential growth was necessary for simulating the yearly growth variation, indicating also at least an indirect source limitation.CASSIA combines seasonal growth and carbon balance dynamics with long-term source dynamics affecting growth and thus provides a first step to understanding the complex processes regulating intra- and interannual growth and sink–source dynamics.
[Show abstract][Hide abstract] ABSTRACT: In the Nordic countries, temperature and precipitation regimes are predicted to change as a result of climate change, which may reduce water availability and thus tree growth. This study presents a spatial approach for analysing variations in the annual radial increments of trees across a latitudinal transect. The aim was to evaluate the importance of daily temperature, precipitation and soil water content as regulators of tree growth across a north-south gradient. Increment cores were collected from living Scots pine (Pinus sylvestris L.) trees growing on dry and sandy soils in five regions in Finland and two regions in Estonia. A total of 1 024 trees were measured across 551 sample plots. No clear latitudinal trend was evident in the magnitude of the correlation between the variations in annual increment and the current summer's temperature, but the time period most strongly related to the increment variation shifted towards earlier dates with a decrease in latitude southwards. Thus, the results challenge the traditional findings that the growth of trees located at lower latitudes is less affected by temperature. Moreover, the results demonstrate the importance of using high-resolution weather data when analysing variations in the radial increments of trees. In all of the regions, including the high northern latitudes, high precipitation in the current summer promotes tree growth, and the correlation between summer precipitation and the increment variation increases with a decrease in latitude. The correlations between increment variation and soil water content estimated using two different models were lower than those involving precipitation. The results suggest that accurate soil information is needed to describe the connection between water content and tree growth.
Full-text · Article · Nov 2014 · Agricultural and Forest Meteorology
[Show abstract][Hide abstract] ABSTRACT: Considerable changes in tree growth are projected due to the expected climate change. The expected changes of climate call for a better insight into the growth responses of trees to varying environmental conditions over large geographical regions. The aim of this study was to analyse the intra-annual tracheid production of Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.) across a latitudinal gradient in Finland (60–68°N). The number of tracheids and the day of the year for the onset, fastest rate, and cessation of tracheid production were determined from microcores repeatedly collected in nine stands during growing seasons of 2001–2009. The onset of tracheid production varied from late May in southern Finland to mid-June in northern Finland. On all stands, tracheid production initiated earlier and ceased later for Scots pine than for Norway spruce. On average, the fastest tracheid production rate occurred slightly after the summer solstice, but variation between sites and years was high. In the northernmost Scots pine stand, the length of the growing season was less than two months and the onset of tracheid production required clearly lower TS than elsewhere. The results imply that within Finland, year-to-year weather variation has a marked impact on the timing of tracheid production. However, the results indicate that the Norway spruce and Scots pine have adapted and are able to adjust their tracheid production according to the local conditions.
No preview · Article · Aug 2014 · Agricultural and Forest Meteorology
[Show abstract][Hide abstract] ABSTRACT: Heterobasidion annosum (Fr.) Bref. s.l., a group of fungi causing root rot, is a serious threat to Norway spruce (Picea abies (L.) Karst.) stands in northern Europe. A new stochastic spatial model (Hmodel) was developed to simulate H. annosum s.l. infection and spread within a stand. Hmodel was combined with the stand-level decision support system MOTTI, resulting in a platform for estimating H. annosum s.l. development and its effect on tree growth and timber quality. Three H. annosum s.l. scenarios, representing different levels of risk for H. annosum s.l. infections simulated for a typical Norway spruce stand in southern Finland, demonstrated that the mycelial growth rate in the roots of living trees was the most critical parameter influencing the simulation results. In addition, the simulation results indicated that the number of infected trees in the previous stand plays a major role in H. annosum s.l. dynamics within the subsequent tree generation. Hmodel was designed to be a flexible platform for researchers to simulate the effects of H. annosum s.l. on stand dynamics and, vice versa, the effects of different silvicultural methods on H. annosum s.l. dynamics.
No preview · Article · Jul 2014 · Canadian Journal of Forest Research
[Show abstract][Hide abstract] ABSTRACT: Site index is an important characteristic for forest management and growth modelling, especially with regard to the ongoing environmental changes. This study introduces a new methodological approach to detecting and quantifying long-term changes in site index. It consists of: (1) a module to construct a reference site index curve from the data under investigation, (2) an OLS-based-CUSUM test to identify change points in development of site index over time, (3) a composite estimator for quantifying changes of the site index over time. The approach was developed using data from 541 Norway spruce (Picea abies [L.] Karst.) long-term experimental plots in southwest Germany between 1872 and 2010. The method is designed to exploit height measurement series of stands growing at different times and different locations (temporally and spatially disjunct). The approach indicated a change in the trajectory of site indices in the early 1950s. Site indices were stable until the change point and have displayed an almost continuous increase since then.
[Show abstract][Hide abstract] ABSTRACT: In Finland, pruning of Norway spruce has recently gained increasing interest, in spite of the past negative results associated
with fungal infections. The aim of the study was to compare the growth of pruned and unpruned Norway spruce and to determine
the effects of pruning on the defects in wood and visual grade distribution of the sawn boards. The material consisted of
60 pruned and 20 unpruned trees. The pruning occurred 20 years before the felling. Approximately 25 per cent of the living
crown was removed, but the pruning did not reduce either the diameter or the height growth of the trees. The pruning decreased
the number of knots on a board surface by 10 knots per board, i.e. 2–3 knots per metre of length of the board. In the outermost
boards, the pruned trees had 67–75 per cent fewer knots. Discoloration or decay occurred in 12–17 per cent of the boards,
but pruning did not increase the frequency of defects. Due to the presence of fewer and smaller knots, the quality distribution
of the boards from the pruned trees was shifted towards the better quality classes. The results demonstrated that pruning
will provide butt logs with a smaller knotty core and boards with higher value than logs from unpruned trees.
[Show abstract][Hide abstract] ABSTRACT: In the Nordic countries, growth of Norway spruce (Picea abies (L.) Karst.) is generally limited by low availability of nutrients, especially nitrogen. Optimizing forest management requires better insight on how growth responds to the environmental conditions and their manipulation. The aim of this study was to analyse the effects of nutrient optimization on timing and the rate of tracheid formation of Norway spruce and to follow the differentiation of newly formed tracheids. The study was performed during two growing seasons in a long-term nutrient optimization experiment in northern Sweden, where all essential macro- and micronutrients were supplied in irrigation water every second day from mid-June to mid-August. The control plots were without additional nutrients and water. Tracheid formation in the stem was monitored throughout the growing season by weekly sampling of microcores at breast height. The onset of xylogenesis occurred in early June, but in early summer there were no significant between-treatment differences in the onset and relative rate of tracheid formation. In both treatments, the onset of secondary cell wall formation occurred in mid-June. The maximum rate of tracheid formation occurred close to the summer solstice and 50% of the tracheids had been accumulated in early July. Optimized nutrition resulted in the formation of ∼50% more tracheids and delayed the cessation of tracheid formation, which extended the tracheid formation period by 20-50%, compared with control trees. The increased growth was mainly an effect of enhanced tracheid formation rate during the mid- and later-part of the growing season. In the second year, the increased growth rate also resulted in 11% wider tracheids. We conclude that the onset and rate of tracheid formation and differentiation during summer is primarily controlled by photoperiod, temperature and availability of nutrients, rather than supply of carbohydrates.
[Show abstract][Hide abstract] ABSTRACT: This study focused on wood density and annual ring width in Norway spruce (Picea abies (L.) Karst.) grown in uneven-aged stands (UAS). In total, 96 trees were harvested from five UAS that had been managed by single-tree selection for decades. A data set of 27 trees from even-aged stands (EAS) was used for comparison. In the UAS trees, high density and narrow annual rings were found in the juvenile wood near the pith. Thereafter, wood density rapidly decreased until the 20th annual ring, followed by an increase toward the bark. In the outermost rings, wood density again slightly decreased. The trends in wood density in the UAS trees correspond with those reported for naturally regenerated, even-aged Norway spruce stands, with the exception of the decrease in the outermost rings. A mixed linear model with ring width, cambial age, and canopy position as fixed parameters accounted for 53% of the variation in wood density of the UAS trees. In contrast to UAS trees, EAS trees showed increased wood density in the outer rings as a result of decreasing growth rate. The abrupt change in wood density of UAS trees may affect the properties of timber sawn close to the pith.
Full-text · Article · Sep 2013 · Canadian Journal of Forest Research
[Show abstract][Hide abstract] ABSTRACT: Models were developed for predicting the proportion of latewood, wood density, tracheid length, tracheid width, and the ratio of cell wall thickness to tracheid width in individual annual rings of Scots pine (Pinus sylvestris L.). The models needed to be applicable as a part of a stand growth simulation system, which is based on growth models at the tree level. Data were collected from long-term thinning, thinning-fertilisation, and precommercial thinning experiments on mineral soil and drained peatland in southern and central Finland. The wood and tracheid properties were related to radial increment rate and distance from the pith outwards. An increased increment rate, caused by the different treatments and environmental conditions, resulted in similar types of changes in the wood and tracheid properties irrespective of the factors promoting radial increment. Although most of the average values of the properties were predicted unbiased, there were large random variations between individual trees and annual rings. The fixed parts of the models accounted for the following percentages of the variation: latewood proportion, 42%, wood density, 35%, tracheid length, 84%, tracheid width, 44%, and cell wall percentage, 29%. Incorporating the models for wood and tracheid properties into forest management planning systems enables estimates for the conversion of different silvicultural regimes into internal stem structure and wood quality.
No preview · Article · Sep 2012 · Forest Ecology and Management
[Show abstract][Hide abstract] ABSTRACT: In recent years, forest information has been evaluated increasingly through its value in decision making, not solely through its statistical accuracy. The value of forest information is rooted in the ability to make better decisions with better data. When the adopted option differs from the optimal, it incurs suboptimality losses, defined as the difference between the outcome (typically NPV) of the optimal and selected options. In this study, we analyse the value of timber quality information for the timber buyer selecting stands to be purchased with a given budget or demand constraint. In the basic constrained linear programming approach, the option selected as optimal with erroneous data may prove to be infeasible when evaluated with error-free data. To properly estimate the value of information, the costs of violating the constraints need to be included. We present a stochastic goal programming approach for solving this problem in which the violations are penalized with the interest of a loan, in the case of budget constraint, and with diminishing revenues, in the case of demand constraints. We show that information on timber quality has value to the buyer, increasing with the penalty. The value varied from 0 to about 80 €·ha–1, assuming only the timber quality assessments to be uncertain. Using the stochastic solution instead of expected value solution also has value for the buyer.
No preview · Article · Jul 2012 · Canadian Journal of Forest Research
[Show abstract][Hide abstract] ABSTRACT: We studied the effects of artificial soil frost on cambial activity and xylem formation on 47-year-old Norway spruce [Picea abies (L.) Karst.] trees grown on medium fertile site type (with moraine soil) in eastern Finland (62°42′N; 29°45′E). Different
soil frost treatments applied were: (1) natural snow accumulation and melting (control, CTRL); (2) artificial removal of snow
from soil surface during two consecutive winters (OPEN); and (3) snow clearing and insulation (FROST), which was in other
ways similar to OPEN, but the ground was insulated in early spring to delay soil thawing. Each treatment was replicated in
three blocks, and two sample trees in each plot were repeatedly microcored during growing seasons of 2006–2007 for the analysis
of the onset, cessation and the duration of xylem formation. The phases of tracheid differentiation (tracheids in radial enlargement,
secondary cell wall formation, and mature tracheids) were measured from the microcores of 2007. The intra-ring growth and
wood density variables were analysed based on X-ray densitometry. In FROST in 2006, xylem formation started a week later than
in the other treatments. In 2007, no difference was found between the treatments. The discrepancy in results between the two
study years may be explained by between-years variation in weather, i.e., the winter was colder in 2005/2006 than in 2006/2007.
No effects of soil frost treatments on tracheid differentiation and on most of the intra-ring growth and density variables
were discovered. Our results suggest that the delayed thawing of moraine soil may slightly affect the onset, timing and duration
of xylem formation in Norway spruce. However, the effects of delayed soil frost may depend also on the soil type and become
more evident with increasing water holding capacity of the soil.
KeywordsCambium–Delayed soil thawing–Picea abies–Radial increment–Tracheid differentiation
[Show abstract][Hide abstract] ABSTRACT: We derive and analyze a model that relates the growth rate of cross-sectional area (‘csa’) at any height on the central stem of a tree to crown-length dynamics. The derivation is based, in part, on assumptions that (a) active csa on the central stem relates allometrically to the length of crown above the cross section, and (b) inactive csa is proportional to active csa within the crown. We also assume that the deactivation rate of csa beneath the crown is determined, in part, by the rate of crown rise. Integration of the growth-rate model under an additional assumption—that total crown length is constant after stand closure—provides a simple model of annual or periodic growth of total csa that can be fit to standard growth data. Three implications of the assumptions and integration are notable: (1) total csa within the crown scales allometrically with stem length above the cross section; (2) for a special case, total csa beneath the crown scales with stem length above the cross section; more generally, csa scales with a linear combination of the stem and crown lengths; and (3) the stem beneath the crown forms to approximate a frustum of a quadratic paraboloid. Basal area data from a loblolly pine (Pinus taeda L.) spacing trial show good agreement with (1) and (2), and with an empirical model developed from the special case of (2). Data from the plots of a Norway spruce (Picea abies (L.) Karst.) thinning trial, where crown length remained approximately constant, show good agreement with (2) and the empirical model. Prediction (3) is demonstrated by simulation.
[Show abstract][Hide abstract] ABSTRACT: We studied the intra-annual wood formation in a Norway spruce provenance experiment in southern Finland from 2004–2008. Two Finnish provenances, northern and southern, as well as German and Hungarian provenances were included. Timing of tracheid formation and differentiation, and tracheid dimensions were determined from periodically extracted microcores. The aim was to determine the differences between the years and provenances in the timing of the xylogenesis and in the xylem characteristics. Year-to-year variation was high both in timing of tracheid formation and xylem characteristics, while between-provenance differences were small. The onset of tracheid formation varied from early May to late June in different trees in different years. The onset of tracheid formation was not closely related to the annual variations of temperature sum. In all the years, daily temperatures exceeded the threshold +5°C for several weeks before the onset of tracheid formation. The highest tracheid formation rate occurred after the summer solstice in all years and generally coincided with the highest daily temperatures during the growing season. Tracheid production ceased early in 2006 due to a mid-summer drought. Cell differentiation continued late in autumn as non-mature tracheids were still observed around mid-September. No clear differences between the provenances in the timing of tracheid formation were observed, although the Finnish provenances tended to initiate tracheid formation slightly earlier than the other provenances. The tree-ring widths of the Finnish provenances were also wider, while tracheid diameter of the German provenance was slightly smaller. Our results indicate that between-tree variation in the timing of wood formation is high compared with the latitude effect of seed source.
[Show abstract][Hide abstract] ABSTRACT: Regional and temporal growth patterns of Norway spruce (Picea abies (L.) Karst.) were evaluated in 40 stands along a transect of over 500 km running from central Finland to the Arctic spruce timberline. Standard deviation of the ring-width series increased from south to north, but the geographical differences in mean sensitivity and first-order autocorrelation were small. The high degree of similarity in growth variation between stands indicated similar growth responses of trees to weather variation despite different environmental conditions along the transect. The most pronounced differences in the regional increment chronologies were found between the southernmost and northernmost stands. Growth variation was most strongly correlated with current June mean temperature, and correlation between growth and July temperature increased from south to north. In addition, negative correlation was observed between winter temperatures, particularly February temperature, and growth variation. Growth was more weakly correlated with precipitation than with temperature.
No preview · Article · Feb 2011 · Canadian Journal of Forest Research
[Show abstract][Hide abstract] ABSTRACT: Branch development of Scots pine (Pinus sylvestris L.) was studied in 19 thinning experiments in southern and central Finland. Data were collected from 229 trees on sites of different fertility with different stand density, age, and canopy position. Stem sections that included the thickest branch or knot of the whorl were sawn out from the whorls below the lowest living and dead whorl. The stem sections were dissected and the years of birth, suppression, death, and occlusion of the branches were determined. Diameter growth of the branches continued for a longer time in older trees. Branch growth was also prolonged by rapid radial growth of the stem. On average, branches died 7 years after their growth cessation. The number of years that branches stayed alive after growth cessation was independent of the tree or stand characteristics. After the death of a branch, more than 40 years elapsed before the branch was occluded. Large branch diameter and rapid radial growth of the stem increased the width of the loose knot zone in the stem. The results showed that there are limited possibilities of using delayed thinnings to reduce the knottiness of timber, and artificial pruning is needed to produce timber of high quality.
No preview · Article · Feb 2011 · Canadian Journal of Forest Research
[Show abstract][Hide abstract] ABSTRACT: The effect of thinning intensity on the growth rate and tracheid dimensions of Norway spruce (Picea abies (L.) Karst) was studied in two long-term thinning experiments (Heinola and Punkaharju) in southeastern Finland. The stand age was 86 and 67 years in Heinola and Punkaharju, respectively. Thinning intensities in this study were lower and higher than recommended in the 1960s for forestry practice in Finland. An increase in tree growth rate (31% in Heinola and 37% in Punkaharju) caused by the high thinning intensity resulted in slightly shorter tracheids (9% in Heinola and 4% in Punkaharju) than with the low thinning intensity. Increased growth rate had no pronounced effect on tracheid cell wall thickness and lumen diameter. A faster growth rate slightly decreased the average cell wall thickness of an annual ring, but the changes in average lumen diameter were small. The effect of thinning intensity was similar in earlywood and latewood. Variation in fiber properties between and within individual trees and annual rings was large. In conclusion, the current thinning intensities used in Finnish forestry practice enhance growth rate but have a rather small effect on tracheid dimensions.
No preview · Article · Feb 2011 · Canadian Journal of Forest Research
[Show abstract][Hide abstract] ABSTRACT: A total of 19 thinning experiments were performed in southern and central Finland to study branchiness of Scots pine (Pinus sylvestris L.). Data were collected from 229 trees of different ages and canopy positions growing on sites of different fertility and thinned to different stand densities. They were used to construct models for predicting vertical trends of branch angle and branch diameter along the stem. By using the variance component model, it was possible to separate the stand-, plot-, and tree-level variations of the dependent variables. However, as the random stand and plot effects were small, they were ignored. The random tree effect of the branch angle model was slightly higher compared with the random tree effect of the branch diameter model. Branch angle increased rapidly in the upper part of the crown, but the increase levelled off in the lower part of the stem. Branch diameter increased from the stem apex to the lower part of the crown and then decreased again towards the base of the tree. Stand density measures were significant variables in the models of branch angle and branch diameter. However, they could be excluded without loss of accuracy if variables describing dimensions of the tree were used as independent variables. Relative crown length and stem diameter were adequate tree-level variables for describing branch characteristics. Validation of the models constructed without variables describing stand density revealed no biased behaviour with respect to stand density. It was concluded that branch characteristics can be predicted from the measurement of some tree-level variables without detailed knowledge of the stand history.
No preview · Article · Feb 2011 · Canadian Journal of Forest Research