Ecosystem Services Related to Carbon Cycling - Modeling Present and Future Impacts in Boreal Forests.

Forests regulate climate, as carbon, water and nutrient fluxes are modified by physiological processes of vegetation and soil. Forests also provide renewable raw material, food, and recreational possibilities. Rapid climate warming projected for the boreal zone may change the provision of these ecosystem services. We demonstrate model based estimates of present and future ecosystem services related to carbon cycling of boreal forests. The services were derived from biophysical variables calculated by two dynamic models. Future changes in the biophysical variables were driven by climate change scenarios obtained as results of a sample of global climate models downscaled for Finland, assuming three future pathways of radiative forcing. We introduce continuous monitoring on phenology to be used in model parametrization through a webcam network with automated image processing features. In our analysis, climate change impacts on key boreal forest ecosystem services are both beneficial and detrimental. Our results indicate an increase in annual forest growth of about 60% and an increase in annual carbon sink of roughly 40% from the reference period (1981-2010) to the end of the century. The vegetation active period was projected to start about 3 weeks earlier and end ten days later by the end of the century compared to currently. We found a risk for increasing drought, and a decrease in the number of soil frost days. Our results show a considerable uncertainty in future provision of boreal forest ecosystem services.

Early snowmelt significantly enhances boreal springtime carbon uptake.

We determine the annual timing of spring recovery from space-borne microwave radiometer observations across northern hemisphere boreal evergreen forests for 1979-2014. We find a trend of advanced spring recovery of carbon uptake for this period, with a total average shift of 8.1 d (2.3 d/decade). We use this trend to estimate the corresponding changes in gross primary production (GPP) by applying in situ carbon flux observations. Micrometeorological CO2 measurements at four sites in northern Europe and North America indicate that such an advance in spring recovery would have increased the January-June GPP sum by 29 g⋅C⋅m-2 [8.4 g⋅C⋅m-2 (3.7%)/decade]. We find this sensitivity of the measured springtime GPP to the spring recovery to be in accordance with the corresponding sensitivity derived from simulations with a land ecosystem model coupled to a global circulation model. The model-predicted increase in springtime cumulative GPP was 0.035 Pg/decade [15.5 g⋅C⋅m-2 (6.8%)/decade] for Eurasian forests and 0.017 Pg/decade for forests in North America [9.8 g⋅C⋅m-2 (4.4%)/decade]. This change in the springtime sum of GPP related to the timing of spring snowmelt is quantified here for boreal evergreen forests.

Temperature dependence of leaf-level CO2 fixation: revising biochemical coefficients through analysis of leaf three-dimensional structure.

CO2 fixation in a leaf is determined by biochemical and physical processes within the boundaries set by leaf structure. Traditionally determined temperature dependencies of biochemical processes include physical processes related to CO2 exchange that result in inaccurate estimates of parameter values. A realistic three-dimensional model of a birch (Betula pendula) leaf was used to distinguish between the physical and biochemical processes affecting the temperature dependence of CO2 exchange, to determine new chloroplastic temperature dependencies for V c(max) and Jmax based on experiments, and to analyse mesophyll diffusion in detail. The constraint created by dissolution of CO2 at cell surfaces substantially decreased the CO2 flux and its concentration inside chloroplasts, especially at high temperatures. Consequently, newly determined chloroplastic V c(max) and Jmax were more temperature dependent than originally. The role of carbonic anhydrase in mesophyll diffusion appeared to be minor under representative mid-day nonwater-limited conditions. Leaf structure and physical processes significantly affect the apparent temperature dependence of CO2 exchange, especially at optimal high temperatures when the photosynthetic sink is strong. The influence of three-dimensional leaf structure on the light environment inside a leaf is marked and affects the local choice between Jmax and V c(max)-limited assimilation rates.

Is Rafflesia an endothermic flower?

• The giant flowers of the parasitic Rafflesia occur in the shade of the forest understorey. They present several characteristics in common with the related species, Rhizanthes lowii, which is a strongly endothermic flower. The possible existence of endothermy in Rafflesia tuan-mudae was investigated here. • The internal and surface temperature of the flowers were continuously monitored with fine thermocouples while radiation fluxes and microclimatic variables were recorded. A computational fluid dynamic model was used to predict the concentrations of CO2 inside the diaphragm of the flower. • It was found that the internal parts of the flower were maintained a few degrees (1-6 K) above air temperature. It was not possible to account for this temperature rise without postulating a significant internal source of heat. It was concluded that R. tuan-mudae is an endothermic flower that generates a maximum of 50-60 W m-2 of heat in the centre of the column. • The possible role of endothermy, CO2 and volatiles as elements in the mimicry of the flower to attract pollinating blowflies is discussed and compared with the related species Rhizanthes lowii.