Current Opinion in Environmental Sustainability, 2013
At a global level, it is estimated that nearly two-thirds of ecosystem services have been degrade... more At a global level, it is estimated that nearly two-thirds of ecosystem services have been degraded in just fifty years. The additional stresses imposed by climate change will require extraordinary adaptation. This paper synthesises main result of a large Finnish project studying the vulnerability of key ecosystem services to climate change and the possibilities for the individual sectors to adapt to these changes. The project based its work on data and infrastructures of nine intensively studied areas belonging to the Finnish LTER (Long-Term Ecological Research) network. The methods developed and used included remote sensing, derivation of impact scenarios, dynamic modelling, laboratory experiments, interactive workshops and expert judgement. The results clearly indicated not only complex interactions between the different ecosystem processes but also trade-offs between the ecosystem services. Climate change was predicted to have both positive and negative effects on key ecosystem services in Finnish conditions, the results being sector-specific and scenariospecific. Provisioning services like food and timber production would largely benefit from increasing temperatures and prolongation of the growing season in the cool Finnish conditions (with e.g. estimated increases in growth rates of trees up to 80% and the introduction of a wider selection of crops), although increasing occurrence of factors such as fungal diseases and insect outbreaks were estimated to cause increasing risks. On the other hand, climate change was predicted to pose a major threat to several endangered and valuable species, water and air quality, and tourism services dependent on present climate conditions. Goal conflicts between maximising service production and meeting environmental quality objectives were also identified. Adaptation options and impact thresholds identified together with local enterprises and experts are presented.
Five years of carbon dioxide exchange measured with the eddy covariance technique at the world... more Five years of carbon dioxide exchange measured with the eddy covariance technique at the world's north-ernmost urban flux station SMEAR III located in Helsinki, Finland, were analyzed. The long-term measurements and high-latitude location enabled us to examine the seasonal and annual variations of CO 2 exchange, and to identify differ-ent factors controlling the measured exchange. Online traf-fic counts and soil respiration measurements were utilized in the study. Furthermore, the advantage of the station is that the complex surrounding area enables us to distinguish three different surface cover areas that can be evaluated separately. We also tested different methods (artificial neural networks and median diurnal cycles) to fill gaps in CO 2 flux time se-ries and examined their effect on annual emission estimates. The measured fluxes were highly dependent on the prevail-ing wind direction with the highest fluxes downwind from a large road and lowest downwind from the area of hi...
Currently, phloem transport in plants under field conditions is not well understood. This is larg... more Currently, phloem transport in plants under field conditions is not well understood. This is largely the result of the lack of techniques suitable for the measurement of the physiological properties of phloem. We present a model that interprets the changes in xylem diameter and live bark thickness and separates the components responsible for such changes. We test the predictions from this model on data from three mature Scots pine trees in Finland. The model separates the live bark thickness variations caused by bark water capacitance from a residual signal interpreted to indicate the turgor changes in the bark. The predictions from the model are consistent with processes related to phloem transport. At the diurnal scale, this signal is related to patterns of photosynthetic activity and phloem loading. At the seasonal scale, bark turgor showed rapid changes during two droughts and after two rainfall events, consistent with physiological predictions. Daily cumulative totals of this t...
Woody plants can suffer from winter embolism as gas bubbles are formed in the water-conducting co... more Woody plants can suffer from winter embolism as gas bubbles are formed in the water-conducting conduits when freezing occurs: gases are not soluble in ice, and the bubbles may expand and fill the conduits with air during thawing. A major assumption usually made in studies of winter embolism formation is that all of the gas dissolved in the xylem sap is trapped within the conduits and forms bubbles during freezing. The current study tested whether this assumption is actually valid, or whether efflux of gases from the stem during freezing reduces the occurrence of embolism. CO2 efflux measurements were conducted during freezing experiments for saplings of three Scots pine (Pinus sylvestris) and three Norway spruce (Picea abies) trees under laboratory conditions, and the magnitudes of the freezing-related bursts of CO2 released from the stems were analysed using a previously published mechanistic model of CO2 production, storage, diffusion and efflux from a tree stem. The freezing-rela...
E. 2001. Xylem diameter changes as an indicator of stand-level evapo-transpiration. Boreal Env. R... more E. 2001. Xylem diameter changes as an indicator of stand-level evapo-transpiration. Boreal Env. Res. 6: 45-52. ISSN 1239-6095
1. Plants exhibit a wide variety in traits at different organizational levels. Intraspecific and ... more 1. Plants exhibit a wide variety in traits at different organizational levels. Intraspecific and interspecific studies have potential to demonstrate functional relationships and trade-offs amongst traits, with potential consequences for growth. However, the distinction between the correlative and functional nature of trait covariation presents a challenge because traits interact in complex ways. 2. We present an intraspecific study on Scots pine branches and use functional multi-trait concepts to organize and understand trait interactions and their impacts on growth. Branch-level traits were assessed for 97 branches from 12 Scots pine sites across Europe. 3. To test alternative hypotheses on cause-effect relationships between anatomical traits, hydraulic traits and branch growth, we measured for each branch: the tracheid hydraulic diameter, double cell wall thickness, cell lumen span area, wood density, cavitation vulnerability, wood-specific hydraulic conductivity, the leaf area to sapwood area ratio and branch growth. We used mixed linear effect models and path models to show how anatomical traits determine hydraulic traits and, in turn, how those traits influence growth. 4. Tracheid hydraulic diameter was the best predictor of cavitation vulnerability (R 2 = 0AE09 explained by path model) and specific conductivity (R 2 = 0AE19) amongst anatomical traits. Leaf area to sapwood area ratio had the strongest direct effect on branch growth (R 2 = 0AE19) and was positively associated with the tracheid hydraulic diameter (R 2 = 0AE22). A number of bivariate correlations between traits could be explained by these functional relationships amongst traits. 5. The plasticity in tracheid hydraulic diameter (10.0-15.1 lm) and leaf area to sapwood area ratio (600-6051 cm 2 cm )2 ) and the maintenance of a minimum leaf water potential (between )2 and )2AE5 MPa) appear to drive the anatomical and hydraulic traits of Scots pine across Europe. These properties are major drivers of the functional trait network underlying the growth variation amongst pine branches and thus possibly contribute to the ecological success of pines at a local and continental scale.
A B S T R A C T We determined the landscape variation of forest floor (FF) CO 2 uptake (photosynt... more A B S T R A C T We determined the landscape variation of forest floor (FF) CO 2 uptake (photosynthesis, P), FF CO 2 emission (respiration, R) in relation to net ecosystem CO 2 exchange (NEE) and environmental factors along a forest-mire ecotone in Finland. The 450 m long ecotone extended from xeric, upland pine dominated habitats, through spruce and transitional spruce-pine-birch forest, to sedge peatlands downslope. The CO 2 fluxes were measured at nine stations during 2005 using chamber and IR techniques. Instantaneous P and R measurements for each station were interpolated by fitting their response to continuous records of light (mean R 2 = 0.66) and temperature (mean R 2 = 0.77) recorded nearby to give annual estimates. Stand biomass increment was used to estimate the annual CO 2 exchange contribution of the trees. Annual P values from −307 to −1632 gCO 2 m −2 yr −1 were inversely correlated with FF light (r = −0.96), FF above-ground biomass (r = −0.92) and canopy openness (r = −0.95). Annual R values from 1263 to 2813 gCO 2 m −2 yr −1 were correlated with tree stand foliar biomass (r = 0.77). Estimated NEE values varied from 546 to −1679 gCO 2 m −2 /yr −1 , with P contributing from −307 to −1632 gCO 2 m −2 yr −1 (4-90%) to gross ecosystem photosynthetic production, and R from 1263 to 2813 gCO 2 m −2 yr −1 (70-98%) to gross ecosystem respiration (GR).
Automatic acquisition of plant architecture is a major challenge for the construction of quantita... more Automatic acquisition of plant architecture is a major challenge for the construction of quantitative models of plant development. Recently, 3-D laser scanners have made it possible to acquire 3-D images representing a sampling of an object's surface. A number of specific methods have been proposed to reconstruct plausible branching structures from this new type of data, but critical questions remain regarding their suitability and accuracy before they can be fully exploited for use in biological applications. In this paper, an evaluation framework to assess the accuracy of tree reconstructions is presented. The use of this framework is illustrated on a selection of laser scans of trees. Scanned data were manipulated by experienced researchers to produce reference tree reconstructions against which comparisons could be made. The evaluation framework is given two tree structures and compares both their elements and their topological organization. Similar elements are identified b...
Xylem and phloem need to maintain steady transport rates of water and carbohydrates to match the ... more Xylem and phloem need to maintain steady transport rates of water and carbohydrates to match the exchange rates of these compounds at the leaves. A major proportion of the carbon and nitrogen assimilated by a tree is allocated to the construction and maintenance of the xylem and phloem long distance transport tissues. This proportion can be expected to increase with increasing tree size due to the growing transport distances between the assimilating tissues, i.e., leaves and fine roots, at the expense of their growth. We formulated whole tree level scaling relations to estimate how xylem and phloem volume, nitrogen content and hydraulic conductance scale with tree size, and how these properties are distributed along a tree height. Xylem and phloem thicknesses and nitrogen contents were measured within varying positions in four tree species from Southern Finland. Phloem volume, nitrogen amount and hydraulic conductance were found to be concentrated toward the branch and stem apices, in contrast to the xylem where these properties were more concentrated toward the tree base. All of the species under study demonstrated very similar trends. Total nitrogen amount allocated to xylem and phloem was predicted to be comparable to the nitrogen amount allocated to the leaves in small and medium size trees, and to increase significantly above the nitrogen content of the leaves in larger trees. Total volume, hydraulic conductance and nitrogen content of the xylem were predicted to increase faster than that of the phloem with increasing tree height in small trees (<∼10 m in height). In larger trees, xylem sapwood turnover to heartwood, if present, would maintain phloem conductance at the same level with xylem conductance with further increases in tree height. Further simulations with a previously published xylem-phloem transport model demonstrated that the Münch pressure flow hypothesis could explain phloem transport with increasing tree height even for the tallest trees. Citation: Hölttä T, Kurppa M and Nikinmaa E (2013) Scaling of xylem and phloem transport capacity and resource usage with tree size. Front. Plant Sci. 4:496.
Nikinmaa, E. 2002. A method for generating stand structures using Gibbs marked point process. Sil... more Nikinmaa, E. 2002. A method for generating stand structures using Gibbs marked point process. Silva Fennica 36(1): 265-277.
A B S T R A C T Data on net CO 2 exchange from eight forests in Denmark, Sweden, Finland and Icel... more A B S T R A C T Data on net CO 2 exchange from eight forests in Denmark, Sweden, Finland and Iceland were used to analyse which factors were controlling photosynthesis and respiration. The forests consisted of different species ranging in climatic condition from temperate to subarctic. Only well mixed conditions were analysed (u * > 0.3 m s −1 ). The parameters of a light response function showed strong seasonal variations with similar behaviour for all stands except for a beech forest where the development of a vigorous ground vegetation in spring affected the photosynthesis parameters differently as compared to the other forests. The beech forest also showed the highest respiration rates in the earlier part of the growing season in contrast to the other forests that showed maximum values in late part of July. The mean halfmonthly nighttime respiration rates were well explained by an equation with one fitting parameter, the respiration rate at 10 • C, with an r 2 = 0.864 for all stands together. The difference between the stands concerning both photosynthesis and respiration parameters were largely explained by the differences in LAI. After normalizing for LAI, the only remaining correlation was between respiration and stand age. These results are promising for application of remote sensing for estimation of respiration as well as gross primary productivity from forests.
Tree models simulate productivity using general gas exchange responses and structural relationshi... more Tree models simulate productivity using general gas exchange responses and structural relationships, but they rarely check whether leaf gas exchange and resulting water and assimilate transport and driving pressure gradients remain within acceptable physical boundaries. This study presents an implementation of the cohesion-tension theory of xylem transport and the Münch hypothesis of phloem transport in a realistic 3-D tree structure and assesses the gas exchange and transport dynamics. A mechanistic model of xylem and phloem transport was used, together with a tested leaf assimilation and transpiration model in a realistic tree architecture to simulate leaf gas exchange and water and carbohydrate transport within an 8-year-old Scots pine tree. The model solved the dynamics of the amounts of water and sucrose solute in the xylem, cambium and phloem using a fine-grained mesh with a system of coupled ordinary differential equations. The simulations predicted the observed patterns of p...
Effect of branch position and light availability on shoot growth of understory sugar maple and yellow birch saplings
Canadian Journal of Botany, 2000
... 1Author to whom all correspondence should be addressed (e-mail: messier.christian@uqam. ca ..... more ... 1Author to whom all correspondence should be addressed (e-mail: messier.christian@uqam. ca ... Schoettle and Smith (1991) found that annual shoot length in-crement and integrated daily photosynthetically active radia-tion (DPAR) at shoot tips increased with increasing height ...
Acclimation of the partitioning of absorbed light energy in Photosystem II (PSII) between photoch... more Acclimation of the partitioning of absorbed light energy in Photosystem II (PSII) between photochemical and non-photochemical processes includes short-term adjustments that are rapidly reversed in the dark and seasonal acclimation processes that are unaffected by dark acclimation. Thus, by using dark-acclimated leaves to study the seasonal acclimation of PSII, the confounding effect of short-term adjustments is eliminated. The maximum quantum yield of photochemistry, estimated by chlorophyll fluorescence analysis as F v /F m , where F v = (F m -F o ), and F m and F o are maximum and minimum chlorophyll fluorescence, respectively, has been widely used to follow the seasonal acclimation of PSII, because it is measured in dark-acclimated leaves. Seasonal changes in F v /F m can be caused by adjustments in either the photochemical capacity in PSII, or the capacity of thermal dissipation in PSII, or both. However, there is a lack of chlorophyll fluorescence parameters that can distinguish between these processes. In this study, we introduce two new parameters: the rate constants of sustained thermal energy dissipation (k NPQ ) and of photochemistry (k P ). We estimated k NPQ and k P from dark-acclimated F o and F m measured during spring recovery of photosynthesis in Scots pine (Pinus sylvestris L.) trees. We suggest that k NPQ and k P be used to study the mechanisms underlying the observed seasonal acclimation in PSII, because these parameters provide quantitative data that complement and extend F v /F m measurements.
Growth of subarctic Scots pine (Pinus sylvestris L.) trees was investigated by a combination of p... more Growth of subarctic Scots pine (Pinus sylvestris L.) trees was investigated by a combination of process-based models and dendroecological approaches. Tree ring width indices were strongly autocorrelated and correlated with simulated photosynthetic production of the previous year and with organic matter N mineralization of the current year. An autoregressive model, with photosynthesis and N mineralization as external inputs, explained growth of the trees well. However, relationships for the period 1950-1992 differed significantly from relationships for the period 1876-1949; the slope of the regression of tree ring width index and photosynthesis was lower for the 1950-1992 period. Also, the autocorrelation structure of the data changed. First-order autocorrelation decreased and second-order autocorrelation increased from the earlier to the later period. This means that growth is becoming less sensitive to variations in photosynthetic production, whereas the relationships between growth and N mineralization are remaining fairly constant. We postulate that, although photosynthesis has increased in response to increasing CO 2 concentrations, tree growth rate cannot parallel the increase in photosynthesis because potential growth rate is limited directly by temperature.
LIGNUM is a whole tree model, developed for Pinus sylvestris in Finland, that combines tree metab... more LIGNUM is a whole tree model, developed for Pinus sylvestris in Finland, that combines tree metabolism with a realistic spatial distribution of morphological parts. We hypothesize that its general concepts, which include the pipe model, functional balance, yearly carbon budget, and a set of architectural growth rules, are applicable to all trees. Adaptation of the model to Pinus banksiana, a widespread species of economic importance in North America, is demonstrated. Conversion of the model to Jack pine entailed ®nding new values for 16 physiological and morphological parameters, and three growth functions. Calibration of the LIGNUM Jack pine model for open grown trees up to 15 years of age was achieved by matching crown appearance and structural parameters (height, foliage biomass, aboveground biomass) with those of real trees. A sensitivity study indicated that uncertainty in the photosynthesis and respiration parameters will primarily cause changes to the net annual carbon gain, which can be corrected through calibration of the growth rate. The effect of a decrease in light level on height, biomass, total tree branch length, and productivity were simulated and compared with ®eld data. Additional studies yielded insight into branch pruning, carbon allocation patterns, crown structure, and carbon stress. We discuss the value of the LIGNUM model as a tool for understanding tree growth and survival dynamics in natural and managed forests. #
2009 Third International Symposium on Plant Growth Modeling, Simulation, Visualization and Applications, 2009
The functional structural plant models (FSPMs) can be defined as models that combine descriptions... more The functional structural plant models (FSPMs) can be defined as models that combine descriptions of metabolic (physiological) processes with a presentation of the 3D structure of a plant. They contain usually the following components 1) Presentation of the plant structure in terms of basic units, 2) Rules of morphological development and 3) Models of metabolic processes that drive the plant growth. The main emphasis in these applications has been individual plants. It is understandable because, due to the detailed description of the plant structure, and consequently, of the local environment of each organ, the FSPMs tend to require a large number of parameters and/or input data. Owing to the large amount of information they contain about the plant to be modeled, they also tend to be computationally heavy. In the following we shortly describe how the three FSPM model components have been realized in the LIGNUM model. Three basic units (Tree segment, Branching point and Bud) are used. We are using the STL template library of C++ to define a blueprint of a tree that can be instantiated by actual representations of the species specific components. We are using four generic algorithms for traversing the data structure of the tree and to make calculations. L-systems are used for specifying the morphological development of the trees. We present three examples of applications made using LIGNUM: a calculation of optimal leaf traits in Sugar maple saplings, a system for storing and analyzing information on decay in city trees and simulation of growth of a tree stand.
Page 1. Effects of tree size and position on pipe model ratios in Scots pine Frank Berninger, Llu... more Page 1. Effects of tree size and position on pipe model ratios in Scots pine Frank Berninger, Lluis Coll, Petteri Vanninen, Annikki Mäkelä, Sari Palmroth, and Eero Nikinmaa Abstract: We investigate how the foliage mass to wood ...
Current Opinion in Environmental Sustainability, 2013
At a global level, it is estimated that nearly two-thirds of ecosystem services have been degrade... more At a global level, it is estimated that nearly two-thirds of ecosystem services have been degraded in just fifty years. The additional stresses imposed by climate change will require extraordinary adaptation. This paper synthesises main result of a large Finnish project studying the vulnerability of key ecosystem services to climate change and the possibilities for the individual sectors to adapt to these changes. The project based its work on data and infrastructures of nine intensively studied areas belonging to the Finnish LTER (Long-Term Ecological Research) network. The methods developed and used included remote sensing, derivation of impact scenarios, dynamic modelling, laboratory experiments, interactive workshops and expert judgement. The results clearly indicated not only complex interactions between the different ecosystem processes but also trade-offs between the ecosystem services. Climate change was predicted to have both positive and negative effects on key ecosystem services in Finnish conditions, the results being sector-specific and scenariospecific. Provisioning services like food and timber production would largely benefit from increasing temperatures and prolongation of the growing season in the cool Finnish conditions (with e.g. estimated increases in growth rates of trees up to 80% and the introduction of a wider selection of crops), although increasing occurrence of factors such as fungal diseases and insect outbreaks were estimated to cause increasing risks. On the other hand, climate change was predicted to pose a major threat to several endangered and valuable species, water and air quality, and tourism services dependent on present climate conditions. Goal conflicts between maximising service production and meeting environmental quality objectives were also identified. Adaptation options and impact thresholds identified together with local enterprises and experts are presented.
Five years of carbon dioxide exchange measured with the eddy covariance technique at the world... more Five years of carbon dioxide exchange measured with the eddy covariance technique at the world's north-ernmost urban flux station SMEAR III located in Helsinki, Finland, were analyzed. The long-term measurements and high-latitude location enabled us to examine the seasonal and annual variations of CO 2 exchange, and to identify differ-ent factors controlling the measured exchange. Online traf-fic counts and soil respiration measurements were utilized in the study. Furthermore, the advantage of the station is that the complex surrounding area enables us to distinguish three different surface cover areas that can be evaluated separately. We also tested different methods (artificial neural networks and median diurnal cycles) to fill gaps in CO 2 flux time se-ries and examined their effect on annual emission estimates. The measured fluxes were highly dependent on the prevail-ing wind direction with the highest fluxes downwind from a large road and lowest downwind from the area of hi...
Currently, phloem transport in plants under field conditions is not well understood. This is larg... more Currently, phloem transport in plants under field conditions is not well understood. This is largely the result of the lack of techniques suitable for the measurement of the physiological properties of phloem. We present a model that interprets the changes in xylem diameter and live bark thickness and separates the components responsible for such changes. We test the predictions from this model on data from three mature Scots pine trees in Finland. The model separates the live bark thickness variations caused by bark water capacitance from a residual signal interpreted to indicate the turgor changes in the bark. The predictions from the model are consistent with processes related to phloem transport. At the diurnal scale, this signal is related to patterns of photosynthetic activity and phloem loading. At the seasonal scale, bark turgor showed rapid changes during two droughts and after two rainfall events, consistent with physiological predictions. Daily cumulative totals of this t...
Woody plants can suffer from winter embolism as gas bubbles are formed in the water-conducting co... more Woody plants can suffer from winter embolism as gas bubbles are formed in the water-conducting conduits when freezing occurs: gases are not soluble in ice, and the bubbles may expand and fill the conduits with air during thawing. A major assumption usually made in studies of winter embolism formation is that all of the gas dissolved in the xylem sap is trapped within the conduits and forms bubbles during freezing. The current study tested whether this assumption is actually valid, or whether efflux of gases from the stem during freezing reduces the occurrence of embolism. CO2 efflux measurements were conducted during freezing experiments for saplings of three Scots pine (Pinus sylvestris) and three Norway spruce (Picea abies) trees under laboratory conditions, and the magnitudes of the freezing-related bursts of CO2 released from the stems were analysed using a previously published mechanistic model of CO2 production, storage, diffusion and efflux from a tree stem. The freezing-rela...
E. 2001. Xylem diameter changes as an indicator of stand-level evapo-transpiration. Boreal Env. R... more E. 2001. Xylem diameter changes as an indicator of stand-level evapo-transpiration. Boreal Env. Res. 6: 45-52. ISSN 1239-6095
1. Plants exhibit a wide variety in traits at different organizational levels. Intraspecific and ... more 1. Plants exhibit a wide variety in traits at different organizational levels. Intraspecific and interspecific studies have potential to demonstrate functional relationships and trade-offs amongst traits, with potential consequences for growth. However, the distinction between the correlative and functional nature of trait covariation presents a challenge because traits interact in complex ways. 2. We present an intraspecific study on Scots pine branches and use functional multi-trait concepts to organize and understand trait interactions and their impacts on growth. Branch-level traits were assessed for 97 branches from 12 Scots pine sites across Europe. 3. To test alternative hypotheses on cause-effect relationships between anatomical traits, hydraulic traits and branch growth, we measured for each branch: the tracheid hydraulic diameter, double cell wall thickness, cell lumen span area, wood density, cavitation vulnerability, wood-specific hydraulic conductivity, the leaf area to sapwood area ratio and branch growth. We used mixed linear effect models and path models to show how anatomical traits determine hydraulic traits and, in turn, how those traits influence growth. 4. Tracheid hydraulic diameter was the best predictor of cavitation vulnerability (R 2 = 0AE09 explained by path model) and specific conductivity (R 2 = 0AE19) amongst anatomical traits. Leaf area to sapwood area ratio had the strongest direct effect on branch growth (R 2 = 0AE19) and was positively associated with the tracheid hydraulic diameter (R 2 = 0AE22). A number of bivariate correlations between traits could be explained by these functional relationships amongst traits. 5. The plasticity in tracheid hydraulic diameter (10.0-15.1 lm) and leaf area to sapwood area ratio (600-6051 cm 2 cm )2 ) and the maintenance of a minimum leaf water potential (between )2 and )2AE5 MPa) appear to drive the anatomical and hydraulic traits of Scots pine across Europe. These properties are major drivers of the functional trait network underlying the growth variation amongst pine branches and thus possibly contribute to the ecological success of pines at a local and continental scale.
A B S T R A C T We determined the landscape variation of forest floor (FF) CO 2 uptake (photosynt... more A B S T R A C T We determined the landscape variation of forest floor (FF) CO 2 uptake (photosynthesis, P), FF CO 2 emission (respiration, R) in relation to net ecosystem CO 2 exchange (NEE) and environmental factors along a forest-mire ecotone in Finland. The 450 m long ecotone extended from xeric, upland pine dominated habitats, through spruce and transitional spruce-pine-birch forest, to sedge peatlands downslope. The CO 2 fluxes were measured at nine stations during 2005 using chamber and IR techniques. Instantaneous P and R measurements for each station were interpolated by fitting their response to continuous records of light (mean R 2 = 0.66) and temperature (mean R 2 = 0.77) recorded nearby to give annual estimates. Stand biomass increment was used to estimate the annual CO 2 exchange contribution of the trees. Annual P values from −307 to −1632 gCO 2 m −2 yr −1 were inversely correlated with FF light (r = −0.96), FF above-ground biomass (r = −0.92) and canopy openness (r = −0.95). Annual R values from 1263 to 2813 gCO 2 m −2 yr −1 were correlated with tree stand foliar biomass (r = 0.77). Estimated NEE values varied from 546 to −1679 gCO 2 m −2 /yr −1 , with P contributing from −307 to −1632 gCO 2 m −2 yr −1 (4-90%) to gross ecosystem photosynthetic production, and R from 1263 to 2813 gCO 2 m −2 yr −1 (70-98%) to gross ecosystem respiration (GR).
Automatic acquisition of plant architecture is a major challenge for the construction of quantita... more Automatic acquisition of plant architecture is a major challenge for the construction of quantitative models of plant development. Recently, 3-D laser scanners have made it possible to acquire 3-D images representing a sampling of an object's surface. A number of specific methods have been proposed to reconstruct plausible branching structures from this new type of data, but critical questions remain regarding their suitability and accuracy before they can be fully exploited for use in biological applications. In this paper, an evaluation framework to assess the accuracy of tree reconstructions is presented. The use of this framework is illustrated on a selection of laser scans of trees. Scanned data were manipulated by experienced researchers to produce reference tree reconstructions against which comparisons could be made. The evaluation framework is given two tree structures and compares both their elements and their topological organization. Similar elements are identified b...
Xylem and phloem need to maintain steady transport rates of water and carbohydrates to match the ... more Xylem and phloem need to maintain steady transport rates of water and carbohydrates to match the exchange rates of these compounds at the leaves. A major proportion of the carbon and nitrogen assimilated by a tree is allocated to the construction and maintenance of the xylem and phloem long distance transport tissues. This proportion can be expected to increase with increasing tree size due to the growing transport distances between the assimilating tissues, i.e., leaves and fine roots, at the expense of their growth. We formulated whole tree level scaling relations to estimate how xylem and phloem volume, nitrogen content and hydraulic conductance scale with tree size, and how these properties are distributed along a tree height. Xylem and phloem thicknesses and nitrogen contents were measured within varying positions in four tree species from Southern Finland. Phloem volume, nitrogen amount and hydraulic conductance were found to be concentrated toward the branch and stem apices, in contrast to the xylem where these properties were more concentrated toward the tree base. All of the species under study demonstrated very similar trends. Total nitrogen amount allocated to xylem and phloem was predicted to be comparable to the nitrogen amount allocated to the leaves in small and medium size trees, and to increase significantly above the nitrogen content of the leaves in larger trees. Total volume, hydraulic conductance and nitrogen content of the xylem were predicted to increase faster than that of the phloem with increasing tree height in small trees (<∼10 m in height). In larger trees, xylem sapwood turnover to heartwood, if present, would maintain phloem conductance at the same level with xylem conductance with further increases in tree height. Further simulations with a previously published xylem-phloem transport model demonstrated that the Münch pressure flow hypothesis could explain phloem transport with increasing tree height even for the tallest trees. Citation: Hölttä T, Kurppa M and Nikinmaa E (2013) Scaling of xylem and phloem transport capacity and resource usage with tree size. Front. Plant Sci. 4:496.
Nikinmaa, E. 2002. A method for generating stand structures using Gibbs marked point process. Sil... more Nikinmaa, E. 2002. A method for generating stand structures using Gibbs marked point process. Silva Fennica 36(1): 265-277.
A B S T R A C T Data on net CO 2 exchange from eight forests in Denmark, Sweden, Finland and Icel... more A B S T R A C T Data on net CO 2 exchange from eight forests in Denmark, Sweden, Finland and Iceland were used to analyse which factors were controlling photosynthesis and respiration. The forests consisted of different species ranging in climatic condition from temperate to subarctic. Only well mixed conditions were analysed (u * > 0.3 m s −1 ). The parameters of a light response function showed strong seasonal variations with similar behaviour for all stands except for a beech forest where the development of a vigorous ground vegetation in spring affected the photosynthesis parameters differently as compared to the other forests. The beech forest also showed the highest respiration rates in the earlier part of the growing season in contrast to the other forests that showed maximum values in late part of July. The mean halfmonthly nighttime respiration rates were well explained by an equation with one fitting parameter, the respiration rate at 10 • C, with an r 2 = 0.864 for all stands together. The difference between the stands concerning both photosynthesis and respiration parameters were largely explained by the differences in LAI. After normalizing for LAI, the only remaining correlation was between respiration and stand age. These results are promising for application of remote sensing for estimation of respiration as well as gross primary productivity from forests.
Tree models simulate productivity using general gas exchange responses and structural relationshi... more Tree models simulate productivity using general gas exchange responses and structural relationships, but they rarely check whether leaf gas exchange and resulting water and assimilate transport and driving pressure gradients remain within acceptable physical boundaries. This study presents an implementation of the cohesion-tension theory of xylem transport and the Münch hypothesis of phloem transport in a realistic 3-D tree structure and assesses the gas exchange and transport dynamics. A mechanistic model of xylem and phloem transport was used, together with a tested leaf assimilation and transpiration model in a realistic tree architecture to simulate leaf gas exchange and water and carbohydrate transport within an 8-year-old Scots pine tree. The model solved the dynamics of the amounts of water and sucrose solute in the xylem, cambium and phloem using a fine-grained mesh with a system of coupled ordinary differential equations. The simulations predicted the observed patterns of p...
Effect of branch position and light availability on shoot growth of understory sugar maple and yellow birch saplings
Canadian Journal of Botany, 2000
... 1Author to whom all correspondence should be addressed (e-mail: messier.christian@uqam. ca ..... more ... 1Author to whom all correspondence should be addressed (e-mail: messier.christian@uqam. ca ... Schoettle and Smith (1991) found that annual shoot length in-crement and integrated daily photosynthetically active radia-tion (DPAR) at shoot tips increased with increasing height ...
Acclimation of the partitioning of absorbed light energy in Photosystem II (PSII) between photoch... more Acclimation of the partitioning of absorbed light energy in Photosystem II (PSII) between photochemical and non-photochemical processes includes short-term adjustments that are rapidly reversed in the dark and seasonal acclimation processes that are unaffected by dark acclimation. Thus, by using dark-acclimated leaves to study the seasonal acclimation of PSII, the confounding effect of short-term adjustments is eliminated. The maximum quantum yield of photochemistry, estimated by chlorophyll fluorescence analysis as F v /F m , where F v = (F m -F o ), and F m and F o are maximum and minimum chlorophyll fluorescence, respectively, has been widely used to follow the seasonal acclimation of PSII, because it is measured in dark-acclimated leaves. Seasonal changes in F v /F m can be caused by adjustments in either the photochemical capacity in PSII, or the capacity of thermal dissipation in PSII, or both. However, there is a lack of chlorophyll fluorescence parameters that can distinguish between these processes. In this study, we introduce two new parameters: the rate constants of sustained thermal energy dissipation (k NPQ ) and of photochemistry (k P ). We estimated k NPQ and k P from dark-acclimated F o and F m measured during spring recovery of photosynthesis in Scots pine (Pinus sylvestris L.) trees. We suggest that k NPQ and k P be used to study the mechanisms underlying the observed seasonal acclimation in PSII, because these parameters provide quantitative data that complement and extend F v /F m measurements.
Growth of subarctic Scots pine (Pinus sylvestris L.) trees was investigated by a combination of p... more Growth of subarctic Scots pine (Pinus sylvestris L.) trees was investigated by a combination of process-based models and dendroecological approaches. Tree ring width indices were strongly autocorrelated and correlated with simulated photosynthetic production of the previous year and with organic matter N mineralization of the current year. An autoregressive model, with photosynthesis and N mineralization as external inputs, explained growth of the trees well. However, relationships for the period 1950-1992 differed significantly from relationships for the period 1876-1949; the slope of the regression of tree ring width index and photosynthesis was lower for the 1950-1992 period. Also, the autocorrelation structure of the data changed. First-order autocorrelation decreased and second-order autocorrelation increased from the earlier to the later period. This means that growth is becoming less sensitive to variations in photosynthetic production, whereas the relationships between growth and N mineralization are remaining fairly constant. We postulate that, although photosynthesis has increased in response to increasing CO 2 concentrations, tree growth rate cannot parallel the increase in photosynthesis because potential growth rate is limited directly by temperature.
LIGNUM is a whole tree model, developed for Pinus sylvestris in Finland, that combines tree metab... more LIGNUM is a whole tree model, developed for Pinus sylvestris in Finland, that combines tree metabolism with a realistic spatial distribution of morphological parts. We hypothesize that its general concepts, which include the pipe model, functional balance, yearly carbon budget, and a set of architectural growth rules, are applicable to all trees. Adaptation of the model to Pinus banksiana, a widespread species of economic importance in North America, is demonstrated. Conversion of the model to Jack pine entailed ®nding new values for 16 physiological and morphological parameters, and three growth functions. Calibration of the LIGNUM Jack pine model for open grown trees up to 15 years of age was achieved by matching crown appearance and structural parameters (height, foliage biomass, aboveground biomass) with those of real trees. A sensitivity study indicated that uncertainty in the photosynthesis and respiration parameters will primarily cause changes to the net annual carbon gain, which can be corrected through calibration of the growth rate. The effect of a decrease in light level on height, biomass, total tree branch length, and productivity were simulated and compared with ®eld data. Additional studies yielded insight into branch pruning, carbon allocation patterns, crown structure, and carbon stress. We discuss the value of the LIGNUM model as a tool for understanding tree growth and survival dynamics in natural and managed forests. #
2009 Third International Symposium on Plant Growth Modeling, Simulation, Visualization and Applications, 2009
The functional structural plant models (FSPMs) can be defined as models that combine descriptions... more The functional structural plant models (FSPMs) can be defined as models that combine descriptions of metabolic (physiological) processes with a presentation of the 3D structure of a plant. They contain usually the following components 1) Presentation of the plant structure in terms of basic units, 2) Rules of morphological development and 3) Models of metabolic processes that drive the plant growth. The main emphasis in these applications has been individual plants. It is understandable because, due to the detailed description of the plant structure, and consequently, of the local environment of each organ, the FSPMs tend to require a large number of parameters and/or input data. Owing to the large amount of information they contain about the plant to be modeled, they also tend to be computationally heavy. In the following we shortly describe how the three FSPM model components have been realized in the LIGNUM model. Three basic units (Tree segment, Branching point and Bud) are used. We are using the STL template library of C++ to define a blueprint of a tree that can be instantiated by actual representations of the species specific components. We are using four generic algorithms for traversing the data structure of the tree and to make calculations. L-systems are used for specifying the morphological development of the trees. We present three examples of applications made using LIGNUM: a calculation of optimal leaf traits in Sugar maple saplings, a system for storing and analyzing information on decay in city trees and simulation of growth of a tree stand.
Page 1. Effects of tree size and position on pipe model ratios in Scots pine Frank Berninger, Llu... more Page 1. Effects of tree size and position on pipe model ratios in Scots pine Frank Berninger, Lluis Coll, Petteri Vanninen, Annikki Mäkelä, Sari Palmroth, and Eero Nikinmaa Abstract: We investigate how the foliage mass to wood ...
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