Lasse Tarvainen

• PhD
• Senior Lecturer at University of Gothenburg

The sensitivity of photosynthesis to temperature has been identified as a key uncertainty for projecting the magnitude of the terrestrial carbon cycle response to future climate change. Although thermal acclimation of photosynthesis under rising temperature has been reported in many tree species, whether tropospheric ozone (O3 ) affects the acclima...

Warming climate increases the risk for harmful leaf temperatures in terrestrial plants, causing heat stress and loss of productivity. The heat sensitivity may be particularly high in equatorial tropical tree species adapted to a thermally stable climate. Thermal thresholds of the photosynthetic system of sun‐exposed leaves were investigated in thre...

Nitrogen (N) fertilization increases biomass and soil organic carbon (SOC) accumulation in boreal pine forests, but the underlying mechanisms remain uncertain. At two Scots pine sites, one undergoing annual N fertilization and the other a reference, we sought to explain these responses. We measured component fluxes, including biomass production, SO...

Current estimates of temperature effects on plants mostly rely on air temperature, although it can significantly deviate from leaf temperature (Tleaf). To address this, some studies have used canopy temperature (Tcan). However, Tcan fails to capture the fine‐scale variation in Tleaf among leaves and species in diverse canopies. We used infrared rad...

PACs (polycylic aromatic compounds) are air pollutants formed in incomplete combustion, e.g., in vehicle engines. Vegetation can potentially remove substantial amounts and act as bioindicators of these pollutants. Increased knowledge of the pollutant removal efficiencies of different tree species is essential for understanding the potential benefit...

Increasing tropospheric ozone (O3) is well known to decrease leaf photosynthesis under steady-state light through reductions in biochemical capacity. However, the effects of O3 on photosynthetic induction and its biochemical limitations in response to fluctuating light remain unclear despite the rapid fluctuations of light intensity occurring under...

The effect of temperature change on leaf physiology has been extensively studied in temperate trees and to some extent in boreal and tropical tree species. While increased temperature typically stimulates leaf CO2 assimilation and tree growth in high-altitude ecosystems, tropical species are often negatively affected. They may operate close to thei...

Boreal forests undergo a strong seasonal photosynthetic cycle; however, the underlying processes remain incompletely characterized. Here, we present a novel analysis of the seasonal diffusional and biochemical limits to photosynthesis (Anet) relative to temperature and light limitations in high‐latitude mature Pinus sylvestris, including a high‐res...

Nitrogen (N) addition causes rapid accumulation of carbon (C) in the soils of boreal forests. The C accumulation has been attributed to an increase in C supply to the soil, to a decrease in mineralization of organic C to CO2, or some combination of the two. We sought to quantify the proportional causes in a case study in a boreal Scots pine forest...

Trees receive growth‐limiting nitrogen from their ectomycorrhizal symbionts, but supplying the fungi with carbon can also cause nitrogen immobilization, which hampers tree growth. We present results from field and greenhouse experiments combined with mathematical modelling, showing that these are not conflicting outcomes. Mycorrhizal networks conne...

The mycorrhizal symbiosis is ubiquitous in boreal forests. Trees and plants provide their fungal partners with photosynthetic carbon in exchange for soil nutrients like nitrogen, which is critical to the growth and survival of the plants. But plant carbon allocation to mycorrhizal symbionts can also fuel nitrogen immobilization, hampering tree grow...

Interpreting phloem carbohydrate or xylem tissue carbon isotopic composition as measures of water‐use efficiency or past tree productivity requires in‐depth knowledge of the factors altering the isotopic composition within the pathway from ambient air to phloem contents and tree ring. One of least understood of these factors is mesophyll conductanc...

Ozone-induced changes in the relationship between photosynthesis (A n) and stomatal conductance (g s) vary among species, leading to inconsistent water use efficiency (WUE) responses to elevated ozone (O 3). Thus, few vegetation models can accurately simulate the effects of O 3 on WUE. Here, we conducted an experiment exposing two differently O 3-s...

Several studies have suggested that CO2 transport in the transpiration stream can considerably bias estimates of root and stem respiration in ring-porous and diffuse-porous tree species. Whether this also happens in species with tracheid xylem anatomy and lower sap flow rates, such as conifers, is currently unclear. We infused 13C-labeled solution...

Elevated ground-level ozone (O 3) concentrations decrease photosynthetic biochemistry more than stomatal conductance (g s), leading to an overall reduction in leaf-scale water use efficiency (WUE). Global warming is expected to lead to more severe and frequent droughts resulting in stomatal closure, increased WUE, and potentially in reduced plant O...

Although ozone (O3) concentration and nitrogen (N) availability are well known to affect plant physiology, their impacts on the photosynthetic temperature response are poorly understood. We addressed this knowledge gap by exposing seedlings of hybrid poplar clone '107' (Populous euramericana cv. '74/76') to elevated O3 (E-O3) and N availability var...

Mesophyll conductance (gm) is a critical variable for the use of stable carbon isotopes to infer photosynthetic water-use efficiency (WUE). Although gm is similar in magnitude to stomatal conductance (gs), it has been measured less often, especially under field conditions and at high temporal resolution. We mounted an isotopic CO2 analyser on a fie...

Terrestrial ecosystems play a very significant role in driving two large global cycles: the carbon and the water cycle. The balance between these two cycles can be described from the plant perspective as water-use efficiency (WUE), briefly photosynthesis/transpiration (A/E). WUE can be defined and interpreted on leaf- to plant- to stand or ecosyste...

The temperature response of photosynthesis is one of the key factors determining predicted responses to warming in global vegetation models (GVMs). The response may vary geographically, owing to genetic adaptation to climate, and temporally, as a result of acclimation to changes in ambient temperature. Our goal was to develop a robust quantitative...

Earth system models (ESMs) use photosynthetic capacity, indexed by the maximum Rubisco carboxylation rate (Vcmax), to simulate carbon assimilation and typically rely on empirical estimates, including an assumed dependence on leaf nitrogen determined from soil fertility. In contrast, new theory, based on biochemical coordination and co‐optimization...

Finite mesophyll conductance (gm) reduces the rate of CO2 diffusion from the leaf intercellular space to the chloroplast and constitutes a major limitation of photosynthesis in trees. While it is well established that gm is decreased by stressors such as drought and high temperature, few studies have investigated if the phytotoxic air pollutant ozo...

Apparent net uptake of carbon dioxide (CO2) during wintertime by a ∼ 90-year-old Scots pine stand in northern Sweden led us to conduct canopy decoupling and subcanopy advection investigations over an entire year. Eddy covariance (EC) measurements ran simultaneously above and within the forest canopy for that purpose. We used the correlation of abov...

Trees are able to reduce their carbon (C) losses by refixing some of the CO2 diffusing out of their stems through corticular photosynthesis. Previous studies have shown that under ideal conditions the outflowing CO2 can be completely assimilated in metabolically active, young stem and branch tissues. Fewer studies have, however, been carried out on...

A key weakness in current Earth System Models is the representation of thermal acclimation of photosynthesis in response to changes in growth temperatures. Previous studies in boreal and temperate ecosystems have shown leaf-scale photosynthetic capacity parameters, the maximum rates of carboxylation (Vcmax ) and electron transport (Jmax ), to be po...

Net uptake of carbon dioxide (CO2) was observed during the winter when using the eddy covariance (EC) technique above a ~90-year-old Scots pine (Pinus sylvestris L.) stand in northern Sweden. This uptake occurred despite photosynthetic dormancy. This discrepancy led us to investigate the potential impact of decoupling of below- and above-canopy air...

Canopy transpiration (EC) is a large fraction of evapotranspiration, integrating physical and biological processes within the energy, water and carbon cycles of forests. Quantifying EC is of both scientific and practical importance, providing information relevant to questions ranging from energy partitioning to ecosystem services, such as primary p...

Numerous studies have shown that temperate and boreal forests are limited by nitrogen (N) availability. However, few studies have provided a detailed account of how carbon (C) acquisition of such forests reacts to increasing N supply. We combined measurements of needle-scale biochemical photosynthetic capacities and continuous observations of shoot...

Repeated measures ANOVA statistics for between plots and age-related variation in the needle properties in the upper canopy shoots including all age three classes presented in Tables 1, 2.

Variation in needle physical and chemical properties with canopy position (upper, mid, lower) in 1-year-old Pinus sylvestris shoots used in continuous shoot-scale net gas exchange measurements.

Photograph of an automated cuvette used for continuous measurements of shoot-scale gas exchange.

Vertical variation in fraction visible sky (openness) in the studied Pinus sylvestris plots.

The impact of including both nitrogen and phosphorus in the predictions of maximum carboxylation rate (Vcmax) and maximum electron transport rate (Jmax) at 25°C in current-year Pinus sylvestris needles.

Apparent net uptake of carbon dioxide (CO2) during winter periods with presumable photosynthetic dormancy has been observed in studies using the eddy covariance (EC) technique above a ~90-year-old Scots pine (Pinus sylvestris L.) stand in northern Sweden. The overall experiment was initiated in 2006 to study the effect of nitrogen (N) availability...

The CoupModel was used to simulate a Norway spruce forest on fertile drained peat over 60 years, from planting in 1951 until 2011, describing abiotic, biotic and greenhouse gas (GHG) emissions (CO2 and N2O). By calibrating the model against tree ring data a “vegetation fitted” model was obtained by which we were able to describe the fluxes and cont...

Simulations of photosynthesis by terrestrial biosphere models typically need a specification of the maximum carboxylation rate ( V cmax ). Estimating this parameter using A – C i curves (net photosynthesis, A , vs intercellular CO 2 concentration, C i ) is laborious, which limits availability of V cmax data. However, many multispecies field dataset...

An apparent “carbon uptake” observed during winter time eddy covariance (EC) measurements of above-canopy carbon fluxes led us to investigate whether decoupling of below- and above-canopy air mass flow and consequently potential below-canopy lateral flow might contribute to this observation. The measurements were conducted at a ~ 90-year-old Scots...

Manipulating tree belowground carbon (C) transport enables investigation of the ecological and physiological roles of tree roots and their associated mycorrhizal fungi, as well as a range of other soil organisms and processes. Girdling remains the most reliable method for manipulating this flux and it has been used in numerous studies. However, gir...

Previous leaf-scale studies of carbon assimilation describe short-term resource use efficiency (RUE) trade-offs where high use efficiency of one resource requires low RUE of another. However, varying resource availabilities may cause long-term RUE trade-offs to differ from the short-term patterns. This may have important implications for understand...

Stomatal conductance (gs) is a key land-surface attribute as it links transpiration, the dominant component of global land evapotranspiration, and photosynthesis, the driving force of the global carbon cycle. Despite the pivotal role of gs in predictions of global water and carbon cycle changes, a global-scale database and an associated globally ap...

The difficulty of obtaining accurate information about the canopy structure is a current limitation towards higher accuracy in numerical predictions of the wind field in forested terrain. The canopy structure in computational fluid dynamics is specified through the frontal area density and this information is required for each grid point in the thr...

Stem CO2 efflux is known to vary seasonally and vertically along tree stems. However, annual tree- and stand-scale efflux estimates are commonly based on measurements made only a few times a year, during daytime and at breast height. In this study, the effect of these simplifying assumptions on annual efflux estimates and their influence on the est...

Afforestation has been proposed as a strategy to mitigate the often high greenhouse gas (GHG) emis-sions from agricultural soils with high organic matter con-tent. However, the carbon dioxide (CO 2) and nitrous ox-ide (N 2 O) fluxes after afforestation can be considerable, de-pending predominantly on site drainage and nutrient avail-ability. Studie...

The sensitivity of carbon (C) assimilation to within-canopy nitrogen (N) allocation and of stomatal conductance (g s) to environmental variables were investigated along a vertical canopy gradient in a fertile Norway spruce [Picea abies (L.) Karst.] stand. Maximum rates of ribulose bisphosphate-saturated carboxylation (V cmax) and electron transport...

Afforestation has been proposed as a strategy to mitigate the often high greenhouse gas (GHG) emissions from agricultural soils with a high organic matter content. However, the carbon dioxide (CO2) and nitrous oxide (N2O) fluxes after afforestation can be considerable, depending predominantly on site drainage and nutrient availability. Studies on t...

A long-established theoretical result states that, for a given total canopy nitrogen (N) content, canopy photosynthesis is maximized when the within-canopy gradient in leaf N per unit area (Na) is equal to the light gradient. However, it is widely observed that Na declines less rapidly than light in real plant canopies. Here we show that this gener...