CO2-assimilation, sequestration, and storage by urban woody species growing in parks and along streets in two climatic zones.

Using two cities, Rimini (Italy, Cfa climate) and Krakow (Poland, Cfb), as living laboratories, this research aimed at measuring in situ the capacity of 15 woody species to assimilate, sequester, and store CO2. About 1712 trees of the selected species were identified in parks or along streets of the two cities, and their age, DBH, height, and crown radius were measured. The volume of trunk and branches was measured using a terrestrial LiDAR. The true Leaf Area Index was calculated by correcting transmittance measurements conducted using a plant-canopy-analyser for leaf angle distribution, woody area index, and clumping. Dendrometric traits were fitted using age or DBH as independent variable to obtain site- and species-specific allometric equations. Instantaneous and daily net CO2-assimilation per unit leaf area was measured using an infra-red gas-analyser on full-sun and shaded leaves and upscaled to the unit crown-projection area and to the whole tree using both a big-leaf and a multilayer approach. Results showed that species differed for net CO2-assimilation per unit leaf area, leaf area index, and for the contribution of shaded leaves to overall canopy carbon gain, which yielded significant differences among species in net CO2-assimilation per unit crown-projection-area (AcpaML(d)). AcpaML(d) was underestimated by 6-30 % when calculated using the big-leaf, compared to the multilayer model. While maximizing AcpaML(d) can maximize CO2-assimilation for a given canopy cover, species which matched high AcpaML(d) and massive canopy spread, such as mature Platanus x acerifolia and Quercus robur, provided higher CO2-assimilation (Atree) at the individual tree scale. Land use (park or street), did not consistently affect CO2-assimilation per unit leaf or crown-projection area, although Atree can decline in response to specific management practices (e.g. heavy pruning). CO2-storage and sequestration, in general, showed a similar pattern as Atree, although the ratio between CO2-sequestration and CO2-assimilation decreased at increasing DBH.

Tree height as the main factor causing disappearance of the terricolous lichens in the lichen Scots pine forests.

The lichen Scots pine forests habitats are undergoing rapid disappearance across Europe. Due to the semi-natural character of this habitat and an increase of the nitrification as a result of air pollution, determination of factors responsible for the decrease in lichen field layer cover requires a comprehensive approach. Our study aimed to investigate environmental factors necessary for the determination of active protection measures in order to maintain this vulnerable habitat. Specifically, we aimed to investigate: 1) the environmental factors influencing lichen cover in the lichen Scots pine forests of Bory Tucholskie National Park; 2) the differences in habitat variables between sites with lichen-rich and bryophyte-rich field layers. In our study, we used vegetation and microhabitat properties data collected over three years of surveys, as well as ALS LiDAR data. Our results indicated that lichen and bryophyte cover, tree height, tree cover, thickness of organic matter layer, soil temperature and soil water content differed between lichen-rich and bryophyte-rich sites. We found a significant negative relationship between lichen cover recorded within the field layer and tree height. The lichen-rich field layer developed better in areas with lower tree height and thinner layer of organic matter, which created a favorable habitat conditions for lichen development. Our research revealed the previously unknown impact of tree height for the development of lichen field layer. These findings can be used to plan the active conservation measures of lichen Scots pine forests.