Abstract. The DO3SE (Deposition of O3 for Stomatal Exchange) model is an established tool for estimating ozone (O3) deposition, stomatal flux and impacts to a variety of vegetation types across Europe. It has been embedded within the EMEP (European Monitoring and Evaluation Programme) photochemical model to provide a policy tool capable of relating the flux-based risk of vegetation damage to O3 precursor emission scenarios for use in policy formulation. A key limitation of regional flux-based risk assessments has been the assumption that soil water deficits are not limiting O3 flux due to the unavailability of evaluated methods for modelling soil water deficits and their influence on stomatal conductance (gsto), and subsequent O3 flux. This paper describes the development and evaluation of a method to estimate soil moisture status and its influence on gsto for a variety of forest tree species. This DO3SE soil moisture module uses the Penman-Monteith energy balance method to drive water cycling through the soil-plant-atmosphere system and empirical data describing gsto relationships with pre-dawn leaf water status to estimate the biological control of transpiration. We trial four different methods to estimate this biological control of the transpiration stream, which vary from simple methods that relate soil water content or potential directly to gsto, to more complex methods that incorporate hydraulic resistance and plant capacitance that control water flow through the plant system. These methods are evaluated against field data describing a variety of soil water variables, gsto and transpiration data for Norway spruce (Picea abies), Scots pine (Pinus sylvestris), birch (Betula pendula), aspen (Populus tremuloides), beech (Fagus sylvatica) and holm oak (Quercus ilex) collected from ten sites across Europe and North America. Modelled estimates of these variables show consistency with observed data when applying the simple empirical methods, with the timing and magnitude of soil drying events being captured well across all sites and reductions in transpiration with the onset of drought being predicted with reasonable accuracy. The more complex methods, which incorporate hydraulic resistance and plant capacitance, perform less well, with predicted drying cycles consistently underestimating the rate and magnitude of water loss from the soil. A sensitivity analysis showed that model performance was strongly dependent upon the local parameterisation of key model drivers such as the maximum gsto, soil texture, root depth and leaf area index. The results suggest that the simple modelling methods that relate gsto directly to soil water content and potential provide adequate estimates of soil moisture and influence on gsto such that they are suitable to be used to assess the potential risk posed by O3 to forest trees across Europe.

No abstract

The chemistry of seepage water was studied before and after small scale clear-cutting and femel cutting (removing 20% of the trees) between 1999 and 2002 at the Höglwald site in southern Bavaria. The interventions were performed in February 2000 on mature, N-saturated Norway spruce (Picea abies (L.) Karst.) stands with high NO − 3 concentrations before felling. Seepage water was collected with suction cups at 40 cm soil depth in the following treatments: (I) a mature stand (control), (II) a femel-cut, and (III) a clear-cut. In the femel cut subvariants were created with suction cups (plots) at varying distances from pre-selected spruce, which were later removed. The femel treatment was replanted with beech (Fagus sylvatica L.) saplings. On the clear-cut, subvariants of planted beech (close to the stem, interstem area), planted spruce (interstem), or natural spruce regeneration were investigated. Clear-cutting caused high NO − 3 peaks (average values up to 2750 µM) during 2000 and 2001 in all planted tree subvariants during times of comparatively low water fluxes. In contrast to peak concentrations, flux weighted yearly average concentrations showed different trends. In 2000, flux weighted yearly average NO − 3 concentrations were significantly elevated, but only on the subvariants of the interstem area, which covered in the clear-cut plot ca. 62% of the area. However, the subvariant close to the stem (31% of clear-cut area), or the natural spruce regeneration subvariant (6% of clear-cut area) exhibited no significant felling effect. With respect to the whole treatment area, this resulted in no significant felling effect as compared with the control. In the next year (2001), flux weighted yearly average NO − 3 concentrations were not significantly affected by clear-cutting, while the concentrations were even reduced for all of the clear-cut subvariants in 2002. On the subvariant natural spruce regeneration, NO − 3 concentrations remained below the European limit of drinking water (806 µM) during almost the whole investigation period. Selective cutting resulted in slightly reduced NO − 3 concentrations in 2000 and 2001 on the femel treatment. However, no significant effect could be detected for any subvariant in the femel-cut, even not for the subvariant with suction cups closest to the felled spruce. In contrast to many other investigations, clearcutting did not increase the NO − 3 problem on the treatment to a relevant extend. Quite contrary, a decline in NO − 3concentrations to values below the EU level for drinking water and levels below the control and femel treatment just 2 years after cutting were observed. Al 3+ concentrations showed nearly the same trend as NO − 3 , while Ca 2+ , Mg 2+ , and K + concentrations were affected to a lesser degree. Only in 2002 was Ca 2+ significantly lower on the clear-cut as compared to the femel treatment, but not compared to the control. Mg 2+ increased in 2000 on the clear-cut subvariants in the interstem area, but decreased in the years 2001 and 2002. Changes could be obs...

No abstract

No abstract

This study investigates the early effects of forest regeneration with selective, and small scale clear-cutting, on ground beetle (Coleoptera, Carabidae) community composition in a homogenous, mature spruce forest in Southern Bavaria (Ho¨glwald), Germany. Carabid beetles were sampled with pitfall-, emergence-, and window-traps, from 1999 to 2001 during a pre-treatment year, the year of cutting, and the year after cutting. In the spruce stand we found a relatively low species richness with few dominating species. Selective cutting preserved this carabid assemblage. At the clear-cuts carabid species richness increased in the year of cutting, because of the invasion of small open field species, and the persistence of most forest species. Also, number of individuals increased due to higher numbers caught in the window-traps. The first open habitat species appeared just a few months after felling. However, in the next year the numbers of individuals, especially of forest species,were drastically reduced. Also, the number of species decreased, and was just slightly higher than on the control plot (mature stand). According to the DCA (detrended correspondence analysis) forest interior species had the same habitat preferences as net building spiders (Amaurobiidae, Linyphiidae) and other families of beetles (Staphylinidae, Curculionidae). Several groups of open habitat species responded positively on different patches found in the clear-cut: (1) diversity ofground vegetation, respectively coverage of shrubs, (2) favour for moist patterns, and water filled ruts (together with Gastropoda), or (3) low coverage of ground vegetation (together with free hunting spiders, Lycosidae). Different structures side by side (mature forest, selective cutting, open areas) may improve diversity on a forest scale. Small openings can serve as an important retreat for open habitat species. However, if clear-cuts become the dominant element, forest species maybe threatened. With selective cutting species richness of carabids is not improved; however, the remaining forest carabid species may be preserved during the early phase of the regeneration process.

& Key message The diversity of structural injury underlying visible symptoms by ozone stress resulted from the succession of degenerative processes and programmed-cell death events, depending on the ozone uptake and varying on a year-toyear basis. & Context The effects of tropospheric ozone (O 3 ) on the vegetation will remain a lasting concern during the twenty-first century, and deeper understanding of functional and structural responses to O 3 in plant foliage in a changing environment is needed. & Aims Comprehensive analysis of the O 3 injury spectrum, with a view to functional understanding of cellular processes in response to varying O 3 doses. & Methods Characterization of macro-and microscopic symptoms in the sun crown foliage of adult trees exposed to ambient and twice ambient O 3 levels in a Free Air O 3 Enrichment (FACE) experiment using light and electron microscopy. & Results Visible injury triggered by O 3 resulted from (i) degenerative processes of varying severity (photobleaching, accelerated cell senescence, ACS), (ii) programmed cell death with disruption of cell content (hypersensitive reaction-like, HR-like) and occasional leakage of cellular debris into the apoplast, (iii) overlapping degenerative and disruptive processes, primarily in the upper mesophyll and within organelles prone to oxidative stress (chloroplasts and mitochondria) and (iv) necrosis in lower mesophyll with leakage of cellular debris in the intracellular space. & Conclusion Especially the degenerative and disruptive traits showed contrasting structural features. In the case of stippling symptoms, the structural variability was particularly high, as a consequence of interactions between early degenerative and late disruptive processes. These findings thus confirmed the close dependency of processes-and a further spectrum of ozone injury-on rates of ozone uptake. Such relationships and development of injury, as observed in the case of beech (Fagus sylvatica L.) foliage, are expected to be basically similar in other broadleaved tree species.

No abstract