Alberto Cozzi

Assessment of ozone visible symptoms in the field: perspectives of quality control

The second UN/ECE ICP-Forests Intercalibration Course on the Assessment of Ozone Injury on European Tree Species was carried out in August 2001 at Lattecaldo (Canton Ticino, CH) and Moggio (Lombardy, I). Forty-eight experts from several European countries participated in the exercises and assessed visible symptoms of ozone injury both in open-top chambers (OTC) (Lattecaldo) and under open field (Moggio) conditions. Evaluation of the results indicated a large variability among the teams and call for adequate training of the observers prior to symptom assessment for quality assurance purposes. Highest variability was found for the species developing unclear symptoms which could be confused with senescence processes; such species should not be used in the field. The authors provide suggestions to improve the reliability of the ozone injury assessment on forest plant species.

Leaf shedding, crown condition and element return in two mixed holm oak forests in Tuscany, central Italy

Abstract Litterfall (leaves, flowers, fruits, twigs) was collected every month in two mixed Mediterranean forests of Quercus ilex (holm oak) in central Italy differing for their ecological features: a mesic site (Colognole, CL) and a xeric one (Cala Violina, CV). The survey period lasted 8 years (1992–2000) at CL and 4 years at CV. Chemical analysis of the litterfall was performed in 1997 and 1998. In these 2 years living leaves were also collected for chemical analysis. The main findings were: (i) the litter production was lower and the leaf percentage in the total litterfall was smaller at CV than at CL; (ii) the phenological behavior differed in the two sites and the leaves had greater longevity at CV, whereas at CL trees renewed their crown almost completely each spring; (iii) the chemical composition of the living leaves reflected the edaphic differences between the two sites; (iv) the chemical composition of the senescent leaves and the litter in the two sites was very different; (v) crown transparency and defoliation followed the same pattern of the leaf shedding; (vi) transparency was greater at CL, where the litter production was higher, because of the different shape of the crowns. The differences between the two study areas have been discussed in the light of the different ecology of the two sites, since leaf lifespan is greater in dry and infertile soils.

Implementation of Quality Assurance Procedures in the Italian Programs of Forest Condition Monitoring

In 1996 the assessment of tree condition in Italy was subjected to a Quality Assurance (QA) program. The QA program consisted in (i) the adoption of Standard Operating Procedures (SOPs), the set of Measurement Quality Objectives (MQOs) expressed by Data Quality Limits (DQLs), (iii) a national training and intercalibration course, and (iv) field checks, performed on a number of areas spread over the country. In general, DQLs were achieved for a number of tree condition indices. However, problems were identified with crown transparency, the most used index in the international reports. Additional problems arose when considering the data quality at plot level as a result of the combined achievement of DQLs for the different tree condition indices.

THE IMPACT OF GEOTHERMAL POWER PLANTS ON FOREST VEGETATION. A CASE STUDY AT TRAVALE (TUSCANY, CENTRAL ITALY)

A survey of the crown status of Turkey oak Quercus cerris L.) trees in the boron-rich area atTravale (Southern Tuscany, Italy) was carried outin order to evaluate the impact ofgeothermal power plants. Crown thinness was assessed andmorphological and chemical tests werecarried out on leaf samples. Leaf area and dry weight weredetermined as morphological parameters;while the chemical measurements performed included nitrogenand potassium (among the nutrients),and sulphur, boron, arsenic and mercury (among the elements ofgeothermal origin). Acute damagewas found only in the area immediately adjacent to the outletsand is the result of the action of boron;crown thinness, on the other hand, is affected by the natureof the geological substrate. High quantitiesof sulphur were found in leaves throughout the survey area,due both to the availability of this elementin the geopedological substrate and to the atmospheric inputof geothermal H2S. The leafcontent of this element correlates negatively with thedistance from the power plants. Boron andarsenic are the other geothermal origin elements most commonlyfound in plant matrices. The presenceof these two elements is associated with leaf area reductionand/or an increase of specific dry weight.The most significant impact on the environment appears to beexerted by the southernmost powerplant, where there is an unfavourable ratio between quantityof emissions and height of the chimneys.

Crown status of holm oak (Quercus ilex L.) trees as related to phenology and environmental stress

In order to study the possible interactions between air pollution and climate conditions in Mediterranean evergreen broadleaf species, since 1987 we have been monitoring the annual and infra-annual variations in crown density of Quercus ilex L. (holm oak) in a permanent sample plot. The behaviour of crown density has been compared with litterfall pattern and aging processes in leaves. The results of this study confirm the important impact of climate on crown condition in Mediterranean broadleaves, so that even the role of nonacute pollution can be disguised. Xeromorph adaptations in holm oak leaves are also a mechanism providing a greater protection against pollutants.

Quality Assurance and measurement errors in monitoring tree crown conditions in Italy

The adoption of a comprehensive Quality Assurance (QA) programme for tree condition monitoring resulted in a rapid and steady improvement of data consistency in crown transparency assessment. On the other hand, the assessment of damage due to insects and fungi remains problematic and requires further training and control efforts. While our findings demonstrated the benefits arising from a QA programme and even the need to reinforce it, recent financial constrains have resulted in a severe reduction of the field checks. This will render it difficult to obtain a sound estimate of data quality and will jeopardize the results of any statistical analysis aimed at identifying status and trends of tree conditions in Italy.

Crown condition surveys in Italian forests: issues in reporting findings.

This study examines defoliation and discoloration findings collected throughout the Italian Level I network between 1997 and 2000. Prior to this period no Quality Assurance procedures had been implemented, so that earlier findings cannot be considered reliable. The aim of the study is to compare differentindices used in reporting findings, in order to determine the full potential and limitations of each. In international surveys,findings are normally expressed in terms of individual trees presenting a defoliation level greater than 2 %; this criterion,however, has been challenged since it is not based on scientificevidence. By analysing the distribution of defoliation values(grouped in 5% classes) relating to the main species (Fagus sylvatica, Quercus pubescens, Quercus cerris, Picea abies), the study examines the behaviour of statistical indices such as the median, the mode and the mean. Instead of using the traditional 25% threshold to determine the part of the population with the highest defoliation values, a procedureis suggested whereby a different threshold can be determined foreach species. It is established based on the 90° percentile of cumulative defoliation values recorded over the four-year period. Each index used to report findings possessesits own information potential, and the findings may at times appear contradictory. The use of a combined defoliation and discoloration index (Ilce = Lacking Crown Equivalent Index) is also proposed, but the results obtained do not differin substance from the results relating to defoliation alone. Thefunctional limitations of this index are due mainly to the way the data are collected: for this reason suggestions are made onhow to improve the procedure in future surveys.

Short-Term Changes of Response Indicators of Ecosystem Status in Broadleaved Forests in Tuscany (Central Italy)

The status of different response indicators of forest condition were measured and assessed between 1995 and 1997 at 6 Permanent Monitoring Plots (PMPs) in Tuscany (central Italy), where beech, holm oak and Turkey oak are the most frequent tree species. Foliage transparency, leaf damage and crown dieback have changed significantly over the monitoring period. Leaf area, length of the current year shoots, and total leaf area changed as well, but only for Turkey oak. Changes were consistent between and within the plots. Different indices of plant diversity showed marked changes, apparently linked to natural dynamics within individual ecosystems. These rapid and contrasting fluctuations in the various indicators of forest ecosystem make it difficult to derive a synthesis about the general condition of ecosystems and - especially - about the effects of air pollution.

Ozone injury symptoms on vegetation in an Alpine valley, North Italy

Abstract In recent years multidisciplinary surveys examining the impact of pollutants on forest ecosystems have been carried out in the Valtellina (Northern Italy, Alpine region). A large part of the activity of these surveys has involved the study of ozone and its distribution in the area, development of the exceedances maps (AOT40) and their validation by means of field observation of visible foliar symptoms in the indigenous and sensitive forest vegetation. The present paper reports the results of a field survey carried out in 1998 on the visible symptoms expressed by several native species (trees, shrubs and herbs). A non-systematic grid of 81 plots was assessed throughout the valley. Due to the high variability of the physical (altitude, slope, exposure, etc.) and vegetational (species assemblage, tree age, forest structure) features, the comparability among the plots was found to be very weak, so only the presence or absence of leaf injuries was assessed. Results do not show any correlation between the distribution of foliar symptoms in Valtellina and ozone levels. Rather, leaf injuries follow the same distribution of environmental modifying factors (such as depth and moisture of the soil) and tree sensitivity.

Crown structure modifications in relation to air pollution

Abstract Analysis of crown structure and crown modifications plays a role of primary importance in surveys of ‘new types of forest damage’, since it is a decisive parameter in assessing the health status of a tree. Several forms of ramification alterations have been described in central and northern European species (Norway spruce, beech, Durmast oak, English oak, birch). This study examines the situation in Tuscany and offers a description of the alterations found in the main species typical of the Mediterranean region (Turkey oak, pubescent oak, holm oak, stone pine). The article discusses the potential impact of these alterations on the most typical forest formations, the ones which characterize the Tuscan landscape, and it describes the modifications already under way.