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Decaying dead wood density measurements are a useful indicator for multiple purposes, such as for estimating the amount of carbon in dead wood and making predictions of potential diversity of dead wood inhabiting fungi and insects. Currently, qualitative decay phases are used as wood density estimates in many applications, since measuring the density is laborious. A quantitative measure of density would, however, be preferred over the qualitative one. Penetrometers, which are commonly used for measuring the density of standing trees, might also be applicable to dead wood density measurements. We tested the device for making quick, quantitative measurements of decaying logs. The penetrometer measures the depth into which a pre-loaded spring forces a pin in the wood. We tested pins of 5 and 10 mm diameter together with an original 2.5 mm pin and compared the results with gravimetric density measurements of the sample logs. Our results suggest that the standard pin works for less decayed wood, but for more decomposed wood, the thicker 5 mm pin gave more reliable estimates when the penetration measures were converted to densities with a linear regression function (R = 0.62, F = 82.9, p = 0.000). The range of wood densities successfully measured with the 5 mm pin was from 180 to 510 kg m. With the 10 mm pin, the measuring resolution of denser wood was compromised, while the improvement at the other end of density scale was not large. As a conclusion, the penetrometer seems to be a promising tool for quick density testing of decaying logs in field, but it needs to be modified to use a thicker measuring pin than the standard 2.5 mm pin.2â3

Phenological time series of flowering and bud burst of Populus tremula (L.) and Betula sp., and the flowering of Pinus sylvestris (L.), Alnus glutinosa (L.) and Alnus incana (L.) were constructed from data collected in Finland during the period 1896â1955. The resulting combined time series were examined with two aims in mind: first, to determine the phenological regularities between different species and, second, to detect patterns of spring advancement over a geographically large area. The results indicate that the geographical pattern of spring advancement is rather uniform from year to year, and between different species. Furthermore, the mechanisms regulating the timing of phenological events in different species seem to function in a similar way, suggesting an unanimous optimal response to climatic conditions.

The evaluation of process-based models (PBM) includes ascertaining their ability to produce results consistent with forest growth in the past. In this study, we parameterized and evaluated the hybrid model PipeQual with datasets containing traditional mensuration variables collected from permanent sample plots (PSP) of even-aged Norway spruce (Picea abies (L.) Karst.) stands in Finland. To initialize the model in the middle of stand development and reproduce observed changes in Norway spruce crown structure, the built-in empirical relationships of crown characteristics were made explicitly dependent on the light environment. After these modifications, the model accuracy at the whole dataset level was high, with slope values of linear regressions between the observations and simulations ranging from 0.77 to 0.99 depending on the variable. The average bias ranged between -0.72 and 0.07 m in stand dominant height, -0.68 and 0.57 cm in stand mean diameter, -2.62 and 1.92 [m.sup.2] in stand basal area, and 20 and 29 [m.sup.3] in stand total stem volume. Stand dynamics after thinning also followed reasonable closely the observed patterns. Accurate predictions illustrate the potential of the model for predicting forest stand growth and forest management effects in changing environmental conditions. Key words: Picea abies, growth simulation model, validation, forest management effect, growth response. L'evaluation des modeles fonctionnels comprend la determination de leur capacite a produire des resultats coherents avec la croissance forestiere passee. Dans cette etude, nous avons parametre et evalue le modele hybride PipeQual a l'aide de jeux de donnees contenant des variables de mesures traditionnelles recoltees a partir de placettes echantillons permanentes dans des peuplements equiennes d'epicea commun (Picea abies (L.) Karst.) en Finlande. Pour initialiser le modele au milieu des stades de developpement des peuplements et reproduire les changements observes dans la structure de la cime des epiceas communs, les relations empiriques integrees au modele decrivant les caracteristiques de la cime ont ete rendues explicitement dependantes de l'environnement lumineux. Apres ces modifications, la precision du modele pour l'ensemble des jeux de donnees etait elevee; la valeur de la pente des regressions lineaires entre les observations et les simulations variait de 0,77 a 0,99 selon la variable. Le biais moyen de la hauteur dominante du peuplement variait de -0,72 a 0,07 m, celui du diametre moyen du peuplement de - 0,68 a 0,57 cm, celui de la surface terriere du peuplement de -2,62 a 1,92 [m.sup.2], et celui du volume total du peuplement de 20 a 29 [m.sup.3]. La dynamique des peuplements apres une eclaircie suivait aussi le comportement des valeurs observees d'assez pres. La precision des previsions met en evidence le potentiel du modele a prevoir la croissance des peuplements et les effets de l'amenagement forestier sous des conditions environnementales changeantes. [Traduit par la Redaction] Mots-cles: Picea abies, modele de simulation de la croissance, validation, effet de l'amenagement forestier, reaction de la croissance., Introduction The importance of forests as resources of raw material is growing due to increasing pressure to reduce the use of fossil fuels and fossil-based materials. At the same time, [...]

Biomass combustion is considered to be carbon neutral, but intensive biomass harvesting may negatively impact carbon stocks in forest soil and vegetation, which can offset the benefits of substituting fossil fuels with biomass. Here we evaluated conventional stem-only harvesting, whole-tree harvesting (WTH), and WTH excluding needles in terms of timber yield, biomass harvests, and forest carbon sequestration. We simulated harvest scenarios in current and changed climates with a process-based growth model (PipeQual) that was integrated with models describing soil decomposition (ROMUL) and soil water dynamics. Furthermore, we compared gains and losses of forest carbon with reductions in fossil-fuel emissions that result from using harvested biomass for energy production. WTH negatively affected stand growth, biomass, and soil carbon stock; negative effects on growth and biomass can be reduced by leaving nitrogen-rich needles behind during WTH. In a changed climate, organic-matter decomposition and nitrogen mineralization accelerated and tree growth was enhanced, increasing the carbon stock of trees and slightly decreasing the soil carbon stock. In the changed climate, WTH had less influence on forest growth and a similar influence on soil carbon sequestration than in the current climate. In the current climate, the WTH decreased the forest carbon stock by, on average, 26.8 Mg C x [ha.sup.-1] over the rotation period. If harvested forest residues are used for energy production instead of fossil fuels, emissions decline by 19 Mg C x [ha.sup.-1] (when WTH is applied over a rotation period). Thus, our analysis suggests that using forest residues for energy production leads to a net increase in carbon emissions. Key words: carbon sequestration, climate change, bioenergy, nitrogen balance, whole-tree harvesting. On assume que la combustion de biomasse est carboneutre mais la recolte intensive de biomasse peut avoir un impact negatif sur les stocks de carbone dans la vegetation et les sols forestiers, ce qui peut reduire les avantages que procure la substitution des combustibles fossiles par la biomasse. Dans cet article nous evaluons l'exploitation conventionnelle qui consiste a recolter seulement le tronc, l'exploitation par arbres entiers (WTH) et WTH sans les aiguilles en termes de production de matiere ligneuse, de recolte de biomasse et de sequestration du carbone forestier. Nous avons simule les scenarios d'exploitation dans les conditions climatiques actuelles et futures en tenant compte des changements climatiques avec un modele de croissance ecophysiologique (PipeQual) qui a ete integre a des modeles de decomposition du sol (ROMUL) et de dynamique de l'eau du sol. De plus, nous avons compare les gains ou les pertes de carbone forestier aux reductions des emissions dues aux combustibles fossiles realisees en utilisant la biomasse recoltee pour la production d'energie. WTH a eu un impact negatif sur la croissance du peuplement, la biomasse et les stocks de carbone dans le sol; les effets negatifs sur la croissance et la biomasse peuvent etre minimises en laissant les aiguilles riches en azote sur le parterre de coupe. Si on tient compte des changements climatiques, la decomposition de la matiere organique et la mineralisation de l'azote seraient plus rapides et la croissance des arbres serait meilleure, ce qui augmenterait les stocks de carbone dans les arbres et les diminuerait legerement dans le sol. Toujours en tenant compte des changements climatiques, WTH aurait moins d'influence sur la croissance de la foret et une influence sur la sequestration du carbone dans le sol semblable a celle qui existe dans les conditions climatiques actuelles. Dans les conditions climatiques actuelles, WTH diminue en moyenne les stocks de carbone forestier de 26,8 Mg C x [ha.sup.-1] au cours de la periode de rotation. Si les residus forestiers sont utilises pour la production d'energie au lieu des combustibles fossiles, les emissions diminuent de 19 Mg C x [ha.sup.-1] (lorsque WTH est appliquee pour la duree de la periode de rotation). Par consequent, notre analyse indique que l'utilisation des residus forestiers pour la production d'energie se traduit par une augmentation nette des emissions de carbone. [Traduit par la Redaction] Mots-cles: sequestration du carbone, changements climatiques, bioenergie, bilan de l'azote, exploitation par arbres entiers., Introduction Forests provide various sustainable means to mitigate climate change. In addition to carbon (C) sequestration in forests and wood products, harvested biomass can replace fossil fuels in energy production. [...]

We combine a process-based growth model for even-aged Norway spruce (Picea abies (L.) Karst.) with economics and optimization. Carbon storage is subsidized based on stand growth and product decay. We include detailed optimized thinnings and timber quality features and present cost functions for stand-level C[O.sub.2] storage. In contrast to earlier studies, our results suggest that changing thinning strategies and postponing thinnings are at least as important as lengthening the rotation period when considering economically efficient carbon storage. The role of thinning is most important in less fertile sites. Contrary to the generic Faustmann model, a higher interest rate increases rotation length on our fertile site. Including carbon release from decaying timber products as reductions from carbon subsidies only has minor effects on optimal solutions. The fertile site stores more discounted carbon. However, with a 1% interest rate, the less fertile site is cost-efficient up to 13 C[O.sub.2] t * [ha.sup.-1], and with a 3% interest rate, it is cost-efficient up to 14 C[O.sub.2] t * [ha.sup.-1]. After these points, carbon storage on the fertile site becomes cheaper. The economic costs of carbon storage suggest that it is optimal to apply carbon storage in Norway spruce forests to meet greenhouse gas reduction commitments. Resume: Nous combinons economique et optimisation a un modele de croissance a base ecophysiologique pour l'epicea commun (Picea abies (L.) Karst.) en peuplement equienne. Le stockage du carbone est subventionne sur la base de la croissance des peuplements et la decomposition des produits du bois. Nous incluons des caracteristiques detaillees de qualite du bois et des eclaircies optimisees et nous presentons des fonctions de cout pour le stockage du C[O.sub.2] a l'echelle du peuplement. Contrairement aux etudes precedentes, nos resultats indiquent qu'il est au moins aussi important de modifier les strategies d'eclaircie et de retarder les eclaircies que d'allonger la periode de rotation lorsqu'on tient compte de l'efficacite du stockage du carbone du point de vue economique. Le role de l'eclaircie est tres important dans les stations moins fertiles. Contrairement au modele generique de Faustmann, un taux d'interet plus eleve allonge la periode de rotation dans notre station fertile. L'inclusion du carbone libere par la decomposition des produits du bois, qui contribue a reduire les subventions pour le carbone, n'a que des effets mineurs sur les solutions optimales. La station fertile emmagasine plus de carbone actualise. Cependant, la station moins fertile est rentable jusqu'a 13 t * [ha.sup.-1] de C[O.sub.2] avec un taux d'interet de 1 % et jusqu'a 14 t * [ha.sup.-1] de C[O.sub.2] avec un taux d'interet de 3 %. Au-dela, il devient moins couteux d'emmagasiner le carbone dans la station fertile. Le cout economique du stockage du carbone indique que l'utilisation des forets d'epicea commun a cette fin, dans le but d'honorer les engagements concernant la reduction des gaz a effet de serre, est une solution optimale. [Traduit par la Redaction], Introduction Forests are widely considered a relatively low-cost tool in carbon dioxide (C[O.sub.2]) sequestration (e.g., IPCC 2007). Soil and vegetation combined are the second largest carbon pool after oceans (IPCC [...]

We conducted an experiment to find out how future climate conditions will impact the spring development of photosynthetic capacity of silver birch leaves. We had two greenhouse conditions. In the simulated future climate condition, we had both elevated temperatures and CO2concentration, while for reference we had trees growing under current climate conditions. We used two methods to measure the development of photosynthetic capacity: first, the maximum quantum efficiency of photosystem II with a fluorescence meter; and second, the CO2assimilation rate with gas exchange measurements. The development of full photosynthetic capacity took around two weeks following the bud burst. The maximum quantum efficiency developed slightly faster than the CO2assimilation rate. Both measurement methods showed that an elevated CO2concentration enhanced the development of photosynthetic capacity beyond the impact of temperature only. The enhancement under the conditions of our simulated climate change translates to achieving photosynthetic capacity up to five days earlier, which impact should be taken into account in simulations of photosynthetic productivity. [ABSTRACT FROM PUBLISHER]

We test whether litter quality, litter quantity and weather data are enough to estimate soil carbon stocks by models. We also test whether inclusion of soil water holding capacity improves soil carbon stock model estimates. Litter input was estimated from stem volume maps provided by the National Forest Inventory, while understorey vegetation was estimated using new biomass models. The litter production rates of trees were based on previous research, while for understorey biomass those were estimated from measured data. We applied Yasso07 and ROMUL models across Finland and ran those models into steady state; thereafter, measured soil carbon stocks were compared with model estimates. We found that the role of understorey litter input is underestimated when the Yasso07 model is parameterised, especially in northern Finland. We also found that the inclusion of soil water holding capacity in the ROMUL model improved predictions, especially in southern Finland. Our results imply that the ecosystem modelling community and greenhouse gas inventories should improve understorey litter estimation in the northern latitudes. Our simulations and measurements show that models using only litter quality, litter quantity and weather data underestimate soil carbon stock in southern Finland and this underestimation is due to omission of the impact of droughts to the decomposition of organic layers. [ABSTRACT FROM AUTHOR]

Biomass combustion is considered to be carbon neutral, but intensive biomass harvesting may negatively impact carbon stocks in forest soil and vegetation, which can offset the benefits of substituting fossil fuels with biomass. Here we evaluated conventional stem-only harvesting, whole-tree harvesting (WTH), and WTH excluding needles in terms of timber yield, biomass harvests, and forest carbon sequestration. We simulated harvest scenarios in current and changed climates with a process-based growth model (PipeQual) that was integrated with models describing soil decomposition (ROMUL) and soil water dynamics. Furthermore, we compared gains and losses of forest carbon with reductions in fossil-fuel emissions that result from using harvested biomass for energy production. WTH negatively affected stand growth, biomass, and soil carbon stock; negative effects on growth and biomass can be reduced by leaving nitrogen-rich needles behind during WTH. In a changed climate, organic-matter decomposition and nitrogen mineralization accelerated and tree growth was enhanced, increasing the carbon stock of trees and slightly decreasing the soil carbon stock. In the changed climate, WTH had less influence on forest growth and a similar influence on soil carbon sequestration than in the current climate. In the current climate, the WTH decreased the forest carbon stock by, on average, 26.8 Mg C·ha−1 over the rotation period. If harvested forest residues are used for energy production instead of fossil fuels, emissions decline by 19 Mg C·ha−1 (when WTH is applied over a rotation period). Thus, our analysis suggests that using forest residues for energy production leads to a net increase in carbon emissions. [ABSTRACT FROM AUTHOR]

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We studied the onset of spring phenology and the long-term trends of 31 species at the Oulainen-Ohineva site (64°13′N, 24°53′E) in central Finland. The species studied represented a wide range including deciduous trees, shrubs, grasses, 18 species of migratory birds and six insect species. The duration of the species-specific time series varied from 4 years up to 54 years during the 1952-2005 observation period. An advancing trend (p < 0.05) in the timing of spring phenology was only found for five species (with over 15 years of observations), namely, Formica rufa group, Rana temporaria, Grus grus, Ficedula hypoleuca and Hirundinidae. In local species with more than 38 years of observations, the temperature trend turned out to be the best variable to describe the advancement of the phenological event. For birds in six cases out of ten the best factor for explaining the advancement, as well as the temperature, was the NAO index. [ABSTRACT FROM AUTHOR]

According to prevailing theory, air temperature is the main environmental factor regulating the timing of bud burst of boreal and temperate trees. Air temperature has a dual role in this regulation. First, after the cessation of growth in autumn, prolonged exposure to chilling causes rest completion, i.e., removes the physiological growth-arresting conditions inside the bud. After rest completion, prolonged exposure to warm conditions causes ontogenetic development leading to bud burst or flowering. During the past three decades, several simulation models based on chilling and forcing have been developed and tested. In recent modeling studies of the timing of bud burst in mature trees, the simpler thermal-time models that assume forcing starts on a fixed date in the spring have outperformed the chilling-forcing models. We hypothesize that this discrepancy may be due to some element missing from the chilling-forcing models.We tested two new model formulations by introducing reversing, temperature-driven elements that precede forcing and by fitting the models to seven historical time series of data of flowering and leaf bud burst of common boreal tree species. In these tests, both of the new models were generally more accurate in predicting the timing of bud burst than a classical chilling-forcing model, but less accurate than the simple thermal-time model. We therefore conclude that besides chilling, other environmental factors are involved in the regulation of the timing of bud burst. Further work is needed to determine if the regulatory factors derive from air temperature or from some other environmental condition such as changes in light conditions, like day length or night length. [ABSTRACT FROM PUBLISHER]

Timing of bud burst and frost damage risk for leaves of Betula spp. in response to climatic warming in Finland was examined with two models. In the first model, ontogenetic development in spring was triggered by an accumulation of chilling temperatures. The second model assumed an additional signal from the light climate. The two models gave radically different estimates of frost damage risk in response to climate warming. [ABSTRACT FROM PUBLISHER]

We tested three theories predicting the timing of bud burst in mature birch (Betula pendula Roth) trees utilizing a 60-year phenological time series together with meteorological temperature observations. Predictions of the timing of bud burst based on light conditions in addition to temperature were more accurate than predictions based on dormancy development and temperature (prediction standard error of 2.4 days versus 4.3 days). The signal from light conditions, represented by fixed calendar date, determined the start of bud ontogenesis rather than dormancy release. We suggest that models developed to predict the timing of bud burst be utilized in the analysis of plant responses to climate change and of climate change itself. [ABSTRACT FROM PUBLISHER]

Collecting phenological data is a slow process. Although such data have been collected by a number of organizations, the reliability of these data is not known because the data-generating process cannot be repeated. No further observations to improve the reliability can be obtained. However, the data usually consist of several overlapping observation series and this overlap can be utilized to construct a combined phenological time series and to improve its reliability. We have developed two techniques for selecting the most reliable observations or observation series and thereby improve the reliability of the combined time series. Both techniques require that the method used to combine the separate phenological time series adjusts the individual series to eliminate possible systematic differences between them. A data set of bud burst in Betula pendula Roth collected in Central Finland during 1896–1955 was adjusted and used to test both techiques. Both techniques considerably improved the reliability of the combined time series; the mean of the confidence intervals of the annual means decreased by 12%. Despite the improvement in reliability, the resulting changes in the annual values of the combined time series were small, the largest change being 2.5 days. Removing outliers was the most effective method of improving reliability, i.e., it resulted in the greatest improvement with the smallest number of discarded observations. [ABSTRACT FROM PUBLISHER]