Mentorointi naisyrittäjyydessä - toimiva menetelmä vai muoti-ilmiö? : tarkastelukohteena Naisyrittäjyyskeskus ry:n mentorointiprojektit

Siirretty Doriast

Some ecosystem service aspects of young street tree plantings

In urban forestry, the assessment and valuation of ecosystem services provided by urban trees are increasingly important both for the rationale of planting new trees and for retaining and managing existing tree populations. To support the field of practical urban forestry, research is needed on the net effects of ecosystem services and costs. The aim of this thesis was to analyse the ecosystem service potential of young street tree plantings. To this end, transplanting recovery, tree growth and carbon and water exchange were studied on two case study streets, one planted with Tilia × vulgaris Hayne and the other with Alnus glutinosa (L.) Gaertn. f. pyramidalis Sakari . The relationships between tree growth, tree and soil water and carbon exchange, environmental variables and tree properties were examined. Transplanting recovery of Tilia trees was delayed due to excess soil water, while Alnus trees recovered within the first few years. Alnus shoot growth responded positively and Tilia negatively to an increase in soil water content. Branch leaf area in relation to branch basal area varied, showing effects of transplanting and subsequent adaptation of the trees to the new growing sites. The studied trees accumulated carbon in their woody biomass during the first decade after transplanting, but the sequestration was small relative to carbon loss from the man-made tree soils. Several additional decades of tree growth were estimated to be needed to attain net carbon sequestration in these street tree plantings if peat originating C and/or renewable C lost from tree soils was counted as C loss. Biomass equations developed in traditional forests predicted total aboveground street tree biomass fairly well, but performed unsatisfactorily in estimating specific aboveground biomass compartments. The biomass distribution and litter production of street trees also require further study to gain insights into the role of tree litter in urban biogeochemical cycles. The annual variation in tree water use of the studied trees was high, but within one year, a Penman-Monteith-based evapotranspiration model with added stomatal conductance and leaf area dynamics description, together with soil water status, explained the variation in tree transpiration quite well. Using a single parameterization over all four years examined did not produce reliable tree water use estimates however. Scaling tree transpiration to different canopy cover percentages implied that especially the columnar Alnus trees could transpire a considerable proportion of annual rainfall with attainable canopy cover, potentially contributing to stormwater management.Tietoa ja ymmärrystä kaupunkipuiden tuottamista ekosysteemipalveluista tarvitaan, kun perustellaan puiden istuttamista ja hoitoa. Kaupunkipuuston järkevä hallinta ja ylläpito edellyttävät tietoa puista saatavista hyödyistä, mutta myös niistä kustannuksista, joita hyötyjen tuottamisesta syntyy. Tässä tutkimuksessa arvioitiin nuorten katupuuistutusten potentiaalia hiileen ja veteen liittyvien ekosysteemipalveluiden tuottajina. Puiden siirtoistutuksesta toipumista, hiilen kertymää ja veden käyttöä sekä näiden yhteyttä ympäristöoloihin tutkittiin uusimpien menetelmien avulla. Toisella Helsingin Viikissä seuratulla kadulla kasvoi kantavalle kasvualustalle istutettua puistolehmusta ja toisella pilaritervaleppää. Lehmusten toipumista siirtoistutuksesta viivästytti kasvupaikan liiallinen märkyys, kun taas tervalepät toipuivat muutamassa vuodessa. Tervaleppien versonkasvu parani maan kosteuden lisääntyessä, lehmusten puolestaan heikkeni. Seuratut puut keräsivät hiiltä biomassaansa ensimmäisen vuosikymmenen kuluessa vähemmän kuin niiden kasvualustoista menetettiin hiiltä ilmakehään. Laaditut ennusteet viittasivat siihen, että kuluisi vielä vuosikymmeniä ennen kuin katupuuistutusten nettovaikutus olisi hiiltä sitova, mikäli kasvualustasta menetetty hiili huomioidaan puuistutuksen hiilikustannuksena. Hiilikustannus riippuu kuitenkin kasvualustan hiilen lähteestä ja hajoamisvauhdista. Metsäpuille kehitetyt biomassayhtälöt ennustivat katupuiden maanpäällistä kokonaisbiomassaa hyvin, mutta puun eri osien, kuten oksien tai rungon osalta ennusteet eivät toimineet. Kaupunkipuiden biomassan jakauma ja erityisesti kariketuotto sekä sen rooli kaupunkiekosysteemin ainekierroissa vaativatkin lisää selvitystyötä. Tutkittujen puiden vedenkäyttö vaihteli suuresti vuosien välillä. Yhden vuoden sisällä sitä voitiin selittää melko hyvin Penman-Monteithin yhtälöllä, kun siihen lisättiin kuvaus ilmarakojohtavuudesta, latvuspinnasta ja lehtialan kehityksestä, sekä huomioitiin maan kosteusolot. Kaikkien neljän mittausvuoden yli ei kuitenkaan pystytty kuvaamaan puiden haihdutusta luotettavasti. Puiden vedenkäyttö suhteessa sadantaan ja latvuspeittävyyteen viittasi siihen, että erityisesti pilaritervalepällä voisi olla tarjottavaa hulevesien hallintaan. Hiileen ja veteen liittyvät ekosysteemipalvelut tuovat pienen lisän muiden katupuiden tarjoamien hyötyjen rinnalle

Environmental and crown related factors affecting street tree transpiration in Helsinki, Finland

We investigated the drivers of street tree transpiration in boreal conditions, in order to better understand tree water use in the context of urban tree planning and stormwater management. Two streets built in Helsinki in 2002, hemiboreal zone that had been planted either with Tilia x vulgaris or Alnus glutinosa f. pyramidalis were used as the study sites. Tree water use was measured from sap flow over the 2008-2011 period by the heat dissipation method. Penman-Monteith based evapotranspiration models of increasing complexity were tested against the tree water use measurements to assess the role of environmental and tree related factors in tree transpiration. Alnus and Tilia respectively used 1.1 and 0.8 l of water per m(2) of leaf area per day under ample water conditions, but the annual variation was high. The Penman-Monteith evapotranspiration estimate and soil water status changes explained over 80 % of the variation in tree transpiration when the model was parameterized annually. The addition of tree crown surface area in the model improved its accuracy and diminished variation between years and sites. Using single parameterization over all four years instead of annually varying one did not produce reliable estimates of tree transpiration. Tree transpiration, scaled to different canopy cover percentages, implied that the columnar Alnus trees could transpire as much as all annual rainfall at or less than 50 % canopy cover.Peer reviewe

Quantifying carbon stocks in urban parks under cold climate conditions

Removing CO2 from the atmosphere and storing carbon in vegetation and soil are important ecosystem services provided by urban green space. However, knowledge on the capacity of trees and soils to store carbon in urban parks - especially in the northern latitudes - is scarce. We assessed the amount of organic carbon stored in trees and soil of constructed urban parks under cold climatic conditions in Finland. More specifically, we investigated the effects of management, vegetation type and time since construction on the amount of carbon stored in park trees and soil. We conducted two tree surveys and collected soil samples (0 to 90 cm) in constructed parks managed by the city of Helsinki. The estimated overall carbon density was approximately 130 t per park hectare, when the carbon stock of trees was 22 to 28 t ha-1 and that of soil 104 t ha-1 at the very least. The soil to tree carbon storage ratio varied from 7.1 to 7.5 for vegetated, pervious grounds and from 3.7 to 5.0 for entire park areas. The effects of park management and vegetation type could not be entirely separated in our data, but time was shown to have a distinct, positive effect on tree and soil carbon stocks. The results indicate that park soils can hold remarkable carbon stocks in a cold climate. It also seems that park soil carbon holding capacity largely exceeds that of forested soils in Finland. Preservation and augmentation of carbon stocks in urban parks implies avoidance of drastic tree and soil renovation measures.Peer reviewe

High carbon losses from established growing sites delay the carbon sequestration benefits of street tree plantings - A case study in Helsinki, Finland

We assessed the net carbon (C) sequestration dynamics of street tree plantings based on 10 years of measurements at two case study sites each with different tree species in Helsinki, Finland. We assessed C loss from tree soils and tree C accumulation, tested the applicability of pre-existing growth and biomass equations against observations, and estimated the time point for the beginning of net C sequestration for the studied street tree plantings. The tree woody biomass C accumulation in the first 10 years after planting was 18-32 kg per tree. At the same time the C loss from the growth media was at least 170 kg per growth media volume (25 m(3)) per tree. If this soil C loss was accounted for, the net C sequestration would begin, at best, approximately 30 years after planting. Biomass equations developed for traditional forests predicted more stem biomass and less leaf and branch biomass than measured for the species examined, but total aboveground biomass was generally well predicted.Peer reviewe

Simulating urban soil carbon decomposition using local weather input from a surface model

Non peer reviewe

Carbon sequestration potential of street tree plantings in Helsinki

Cities have become increasingly interested in reducing their greenhouse gas emissions and increasing carbon sequestration and storage in urban vegetation and soil as part of their climate mitigation actions. However, most of our knowledge of the biogenic carbon cycle is based on data and models from forested ecosystems, despite urban nature and microclimates differing greatly from those in natural or forested ecosystems. There is a need for modelling tools that can correctly consider temporal variations in the urban carbon cycle and take specific urban conditions into account. The main aims of our study were to (1) examine the carbon sequestration potential of two commonly used street tree species (Tilia x vulgaris and Alnus glutinosa) growing in three different growing media by taking into account the complexity of urban conditions and (2) evaluate the urban land surface model SUEWS (Surface Urban Energy and Water Balance Scheme) and the soil carbon model Yassol5 in simulating the carbon sequestration of these street tree plantings at temporal scales (diurnal, monthly, and annual). SUEWS provides data on the urban microclimate and on street tree photosynthesis and respiration, whereas soil carbon storage is estimated with Yasso. These models were used to study the urban carbon cycle throughout the expected lifespan of street trees (2002-2031). Within this period, model performances were evaluated against transpiration estimated from sap flow, soil carbon content, and soil moisture measurements from two street tree sites located in Helsinki, Finland. The models were able to capture the variability in the urban carbon cycle and transpiration due to changes in environmental conditions, soil type, and tree species. Carbon sequestration potential was estimated for an average street tree and for the average of the diverse soils present in the study area. Over the study period, soil respiration dominated carbon exchange over carbon sequestration due to the high initial carbon loss from the soil after street construction. However, the street tree plantings turned into a modest sink of carbon from the atmosphere on an annual scale, as tree and soil respiration approximately balanced the photosynthesis. The compensation point when street tree plantings turned from an annual source into a sink was reached more rapidly - after 12 years - by Alnus trees, while this point was reached by Tilia trees after 14 years. However, these moments naturally vary from site to site depending on the growing media, planting density, tree species, and climate. Overall, the results indicate the importance of soil in urban carbon sequestration estimations.Peer reviewe

Irreversible diameter change of wood segments correlates with other methods for estimating frost tolerance of living cells in freeze-thaw experiment: a case study with seven urban tree species in Helsinki

International audienceAbstractKey messageWe assessed tree frost tolerance using electrolyte leakage and a method based on irreversible diameter change of branches. It was shown that irreversible diameter change correlates with electrolyte leakage and USDA hardiness rating and is a good indicator of frost tolerance.ContextThe number of potential tree species for urban green planning is low in northern latitudes where cold tolerance is a critical factor. High cost of urban tree establishment calls for reliable and preferably non-destructive methods for determining their cold tolerance.AimsWe studied the cellular damage occurring during freezing and thawing in branches of seven broadleaved tree species using electrolyte leakage and a method based on branch diameter changes.MethodsCellular damage in branches was studied during the cold-hardy stage in winter and the dehardening stage in early spring in laboratory conditions using both monitoring of frost-induced diameter changes and the common electrolyte leakage method during temperature decrease to −25 °C.ResultsFrost-induced irreversible diameter shrinkage correlated positively with electrolyte leakage. Out of the seven studied species, Quercus palustris and Crataegus monogyna had the highest frost tolerance during the dehardening stage in early spring, whereas Pterocarya fraxinifolia was the least frost tolerant.ConclusionIrreversible shrinkage of branch diameter due to freezing stress is a good and non-destructive method to indicate frost tolerance. It also correlates well with the USDA plant hardiness rating that is based on the minimum temperature range in which the studied species prevail in the USA

The influence of soil temperature and water content on belowground hydraulic conductance and leaf gas exchange in mature trees of three boreal species

Understanding stomatal regulation is fundamental to predicting the impact of changing environmental conditions on vegetation. However, the influence of soil temperature (ST) and soil water content (SWC) on canopy conductance (g(s)) through changes in belowground hydraulic conductance (k(bg)) remains poorly understood, because k(bg) has seldom been measured in field conditions. Our aim was to (a) examine the dependence of k(bg) on ST and SWC, (b) examine the dependence of g(s) on k(bg) and (c) test a recent stomatal optimization model according to which g(s) and soil-to-leaf hydraulic conductance are strongly coupled. We estimated k(bg) from continuous sap flow and xylem diameter measurements in three boreal species. k(bg) increased strongly with increasing ST when ST was below +8 degrees C, and typically increased with increasing SWC when ST was not limiting. g(s) was correlated with k(bg) in all three species, and modelled and measured g(s) were well correlated in Pinus sylvestris (a model comparison was only possible for this species). These results imply an important role for k(bg) in mediating linkages between the soil environment and leaf gas exchange. In particular, our finding that ST strongly influences k(bg) in mature trees may help us to better understand tree behaviour in cold environments.Peer reviewe