Strategies Towards Scenarios of Forest Damage Due to Air Pollution

This report is a review of the requirements and possibilities of developing a regional scale, long term model for the response of forests to atmospheric pollution. A general input-output structure of such models is delineated, and the input, output and potential model structures are considered. With the objective of specifying the input variables, potential causes of forest damage are classified according to their dynamic properties. Forest damage is further specified, so as to define the output variables. Theoretical and empirical models for the response of forests to air pollution are reviewed, as well as some empirical evidence applicable to the models. The possibilities of constructing scenarios of damage over Europe are assessed, and the present theoretical and practical restrictions are evaluated

Cuticular Needle Erosion and Winter Drought in Polluted Environments - A Model Analysis

A method is developed for analyzing the consequences of pollutant-imposed cuticular erosion for the tolerance of winter drought in coniferous trees. The erosion rate of cuticular wax is modeled in terms of the contact angle of water droplets, as a function of sulphur dioxide, air temperature and relative humidity. Whole tree transpiration during drought is considered, assuming that the state of erosion affects the cuticular resistance of each needle age class. A formula is derived to compare transpiration with the water available in foliage and stem storage. The derivations are applied to a numerical example concerning the transpiration during a warm spell in the spring. Under certain assumptions, increased cuticular transpiration may well give rise to increased winter drought damage. However, many of the parameters and processes still need to be more thoroughly investigated. The most critical open question appears to be the quantitative relationship between cuticular resistance and the state of erosion of the cuticle

Estimation of Local Values of Monthly Mean Temperature, Effective Temperature Sum and Precipitation Sum in Europe

The present paper presents a method for estimating the local values of meteorological variables from measurements in the vicinity of the subject point. Two interpolation methods are considered: the moving averages method, which calculates a weighted average of observations in the neighborhood of the subject point, and the combined method, which improves the moving averages estimate by utilizing the statistical dependence on latitude and altitude of the variables. The methods are applied to the estimation of the local values of monthly mean temperature, monthly precipitation sum, and the effective temperature sum in Europe. The input data consists of 30-year time series of monthly values from a network of meteorological stations, comprising 666 stations for monthly mean temperature and 517 for precipitation. The methods are tested by subtracting one station at a time from the observation network and calculating the values of the climatic variables from the rest of the data. The root mean square error (RMSE) of the smoothed mean temperature in the period May-August is approximately 0.7 degrees Centigrade, and that of the precipitation sum in the order of 70mm. In areas with a denser network of observations, the RMSE is lower

Direct Effects of Sulfur on Forests in Europe - A Regional Model of Risk

A simple dynamic model for the sensitivity and risk in forests under long-term exposure to airborne sulfur is presented. The model is an interpretation of results from long-term forest damage and sulfur dioxide measurements in Czechoslovakia, and it focuses on damage caused by direct, foliar impacts. The input to the model is the annual average SO2 concentration, and the accumulation of impact over time is incorporated. In a regional application of the model, sensitivity is defined as a function of the effective temperature sum. Sensitivity and risk maps of Europe in relation to direct impacts of sulfur are presented

Relation Between Type II Bursts and CMEs Inferred from STEREO Observations

The inner coronagraph (COR1) of the Solar Terrestrial Relations Observatory (STEREO) mission has made it possible to observe coronal mass ejections (CMEs) a in the spatial domain overlapping with that of the metric type II radio bursts. The type II bursts were associated with generally weak flares (mostly B and C class soft X-ray flares), but the CMEs were quite energetic. Using CME data for a set of type II bursts during the declining phase of solar cycle 23, we determine the CME height when the type II bursts start, thus giving an estimate of the heliocentric distance at which CME-driven shocks form. This distance has been determined to be approximately 1.5Rs (solar radii), which coincides with the distance at which the Alfv?n speed profile has a minimum value. We also use type II radio observations from STEREO/WAVES and Wind/WAVES observations to show that CMEs with moderate speed drive either weak shocks or no shock at all when they attain a height where the Alfv?n speed peaks (?3Rs ? 4Rs). Thus the shocks seem to be most efficient in accelerating electrons in the heliocentric distance range of 1.5Rs to 4Rs. By combining the radial variation of the CME speed in the inner corona (CME speed increase) and interplanetary medium (speed decrease) we were able to correctly account for the deviations from the universal drift-rate spectrum of type II bursts, thus confirming the close physical connection between type II bursts and CMEs. The average height (approximately 1.5 Rs) of STEREO CMEs at the time of type II bursts is smaller than that (2.2 Rs) obtained for SOHO (Solar and Heliospheric Observatory) CMEs. We suggest that this may indicate, at least partly, the density reduction in the corona between the maximum and declining phases, so a given plasma level occurs closer to the Sun in the latter phase. In two cases, there was a diffuse shock-like feature ahead of the main body of the CME, indicating a standoff distance of 1Rs - 2Rs by the time the CME left the LASCO field of view

Dichomitus squalens partially tailors its molecular responses to the composition of solid wood

White-rot fungi, such as Dichomitus squalens, degrade all wood components and inhabit mixed-wood forests containing both soft- and hardwood species. In this study, we evaluated how D. squalens responded to the compositional differences in softwood [guaiacyl (G) lignin and higher mannan content] and hardwood [syringyl/guaiacyl (S/G) lignin and higher xylan content] using semi-natural solid cultures. Spruce (softwood) and birch (hardwood) sticks were degraded by D. squalens as measured by oxidation of the lignins using 2D-NMR. The fungal response as measured by transcriptomics, proteomics and enzyme activities showed a partial tailoring to wood composition. Mannanolytic transcripts and proteins were more abundant in spruce cultures, while a proportionally higher xylanolytic activity was detected in birch cultures. Both wood types induced manganese peroxidases to a much higher level than laccases, but higher transcript and protein levels of the manganese peroxidases were observed on the G-lignin rich spruce. Overall, the molecular responses demonstrated a stronger adaptation to the spruce rather than birch composition, possibly because D. squalens is mainly found degrading softwoods in nature, which supports the ability of the solid wood cultures to reflect the natural environment.Peer reviewe

Optimal function explains forest responses to global change

Plant responses to global changes in carbon dioxide (CO2), nitrogen, and water availability are critical to future atmospheric CO2 concentrations, hydrology, and hence climate. Our understanding of those responses is incomplete, however. Multiple-resource manipulation experiments and empirical observations have revealed a diversity of responses, as well as some consistent patterns. But vegetation models-currently dominated by complex numerical simulation models-have yet to achieve a consensus among their predicted responses, let alone offer a coherent explanation of the observed ones. Here we propose an alternative approach based on relatively simple optimization models (OMs). We highlight the results of three recent forest OMs, which together explain a remarkable range of observed forest responses to altered resource availability. We conclude that OMs now offer a simple yet powerful approach to predicting the responses of forests-and, potentially, other plant types-to global change. We recommend ways in which OMs could be developed further in this direction