Browsing by Subject "LAND-COVER CHANGE"

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  • Holmberg, Maria; Aalto, Tuula; Akujarvi, Anu; Arslan, Ali Nadir; Bergstrom, Irina; Bottcher, Kristin; Lahtinen, Ismo; Makela, Annikki; Markkanen, Tiina; Minunno, Francesco; Peltoniemi, Mikko; Rankinen, Katri; Vihervaara, Petteri; Forsius, Martin (2019)
    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.
  • Scott, C. E.; Monks, S. A.; Spracklen, D. V.; Arnold, S. R.; Forster, P. M.; Rap, A.; Äijälä, M.; Artaxo, P.; Carslaw, K. S.; Chipperfield, M. P.; Ehn, M.; Gilardoni, S.; Heikkinen, L.; Kulmala, M.; Petäjä, T.; Reddington, C. L. S.; Rizzo, L. V.; Swietlicki, E.; Vignati, E.; Wilson, C. (2018)
    The climate impact of deforestation depends on the relative strength of several biogeochemical and biogeophysical effects. In addition to affecting the exchange of carbon dioxide (CO2) and moisture with the atmosphere and surface albedo, vegetation emits biogenic volatile organic compounds (BVOCs) that alter the formation of short-lived climate forcers (SLCFs), which include aerosol, ozone and methane. Here we show that a scenario of complete global deforestation results in a net positive radiative forcing (RF; 0.12Wm-2) from SLCFs, with the negative RF from decreases in ozone and methane concentrations partially offsetting the positive aerosol RF. Combining RFs due to CO2, surface albedo and SLCFs suggests that global deforestation could cause 0.8 K warming after 100 years, with SLCFs contributing 8% of the effect. However, deforestation as projected by the RCP8.5 scenario leads to zero net RF from SLCF, primarily due to nonlinearities in the aerosol indirect effect.
  • Liu, Yang; Schallhart, Simon; Taipale, Ditte; Tykkä, Toni; Räsänen, Matti; Merbold, Lutz; Hellén, Heidi; Pellikka, Petri (2021)
    The East African lowland and highland areas consist of water-limited and humid ecosystems. The magnitude and seasonality of biogenic volatile organic compounds (BVOCs) emissions and concentrations from these functionally contrasting ecosystems are limited due to a scarcity of direct observations. We measured mixing ratios of BVOCs from two contrasting ecosystems, humid highlands with agroforestry and dry lowlands with bushland, grassland, and agriculture mosaics, during both the rainy and dry seasons of 2019 in southern Kenya. We present the diurnal and seasonal characteristics of BVOC mixing ratios and their reactivity and estimated emission factors (EFs) for certain BVOCs from the African lowland ecosystem based on field measurements. The most abundant BVOCs were isoprene and monoterpenoids (MTs), with isoprene contributing > 70 % of the total BVOC mixing ratio during daytime, while MTs accounted for > 50 % of the total BVOC mixing ratio during nighttime at both sites. The contributions of BVOCs to the local atmospheric chemistry were estimated by calculating the reactivity towards the hydroxyl radical (OH), ozone (O-3), and the nitrate radical (NO3). Isoprene and MTs contributed the most to the reactivity of OH and NO3, while sesquiterpenes dominated the contribution of organic compounds to the reactivity of O-3. The mixing ratio of isoprene measured in this study was lower than that measured in the relevant ecosystems in western and southern Africa, while that of monoterpenoids was similar. Isoprene mixing ratios peaked daily between 16:00 and 20:00 (all times are given as East Africa Time, UTC+3), with a maximum mixing ratio of 809 pptv (parts per trillion by volume) and 156 pptv in the highlands and 115 and 25 pptv in the lowlands during the rainy and dry seasons, respectively. MT mixing ratios reached their daily maximum between midnight and early morning (usually 04:00 to 08:00), with mixing ratios of 254 and 56 pptv in the highlands and 89 and 7 pptv in the lowlands in the rainy and dry seasons, respectively. The dominant species within the MT group were limonene, alpha-pinene, and beta-pinene. EFs for isoprene, MTs, and 2-Methyl-3-buten-2-ol (MBO) were estimated using an inverse modeling approach. The estimated EFs for isoprene and beta-pinene agreed very well with what is currently assumed in the world's most extensively used biogenic emissions model, the Model of Emissions of Gases and Aerosols from Nature (MEGAN), for warm C-4 grass, but the estimated EFs for MBO, alpha-pinene, and especially limonene were significantly higher than that assumed in MEGAN for the relevant plant functional type. Additionally, our results indicate that the EF for limonene might be seasonally dependent in savanna ecosystems.
  • Helbig, Manuel; Waddington, James M.; Alekseychik, Pavel; Amiro, Brian; Aurela, Mika; Barr, Alan G.; Black, T. Andrew; Carey, Sean K.; Chen, Jiquan; Chi, Jinshu; Desai, Ankur R.; Dunn, Allison; Euskirchen, Eugenie S.; Flanagan, Lawrence B.; Friborg, Thomas; Garneau, Michelle; Grelle, Achim; Harder, Silvie; Heliasz, Michal; Humphreys, Elyn R.; Ikawa, Hiroki; Isabelle, Pierre-Erik; Iwata, Hiroki; Jassal, Rachhpal; Korkiakoski, Mika; Kurbatova, Juliya; Kutzbach, Lars; Lapshina, Elena; Lindroth, Anders; Lofvenius, Mikaell Ottosson; Lohila, Annalea; Mammarella, Ivan; Marsh, Philip; Moore, Paul A.; Maximov, Trofim; Nadeau, Daniel F.; Nicholls, Erin M.; Nilsson, Mats B.; Ohta, Takeshi; Peichl, Matthias; Petrone, Richard M.; Prokushkin, Anatoly; Quinton, William L.; Roulet, Nigel; Runkle, Benjamin R. K.; Sonnentag, Oliver; Strachan, Ian B.; Taillardat, Pierre; Tuittila, Eeva-Stiina; Tuovinen, Juha-Pekka; Turner, Jessica; Ueyama, Masahito; Varlagin, Andrej; Vesala, Timo; Wilmking, Martin; Zyrianov, Vyacheslav; Schulze, Christopher (2020)
    Peatlands and forests cover large areas of the boreal biome and are critical for global climate regulation. They also regulate regional climate through heat and water vapour exchange with the atmosphere. Understanding how land-atmosphere interactions in peatlands differ from forests may therefore be crucial for modelling boreal climate system dynamics and for assessing climate benefits of peatland conservation and restoration. To assess the biophysical impacts of peatlands and forests on peak growing season air temperature and humidity, we analysed surface energy fluxes and albedo from 35 peatlands and 37 evergreen needleleaf forests-the dominant boreal forest type-and simulated air temperature and vapour pressure deficit (VPD) over hypothetical homogeneous peatland and forest landscapes. We ran an evapotranspiration model using land surface parameters derived from energy flux observations and coupled an analytical solution for the surface energy balance to an atmospheric boundary layer (ABL) model. We found that peatlands, compared to forests, are characterized by higher growing season albedo, lower aerodynamic conductance, and higher surface conductance for an equivalent VPD. This combination of peatland surface properties results in a similar to 20% decrease in afternoon ABL height, a cooling (from 1.7 to 2.5 degrees C) in afternoon air temperatures, and a decrease in afternoon VPD (from 0.4 to 0.7 kPa) for peatland landscapes compared to forest landscapes. These biophysical climate impacts of peatlands are most pronounced at lower latitudes (similar to 45 degrees N) and decrease toward the northern limit of the boreal biome (similar to 70 degrees N). Thus, boreal peatlands have the potential to mitigate the effect of regional climate warming during the growing season. The biophysical climate mitigation potential of peatlands needs to be accounted for when projecting the future climate of the boreal biome, when assessing the climate benefits of conserving pristine boreal peatlands, and when restoring peatlands that have experienced peatland drainage and mining.