John L. Innes

Identification, measurement and interpretation of tree rings in woody species from mediterranean climates

We review the literature dealing with mediterranean climate, vegetation, phenology and ecophysiology relevant to the understanding of tree‐ring formation in mediterranean regions. Tree rings have been used extensively in temperate regions to reconstruct responses of forests to past environmental changes. In mediterranean regions, studies of tree rings are scarce, despite their potential for understanding and predicting the effects of global change on important ecological processes such as desertification. In mediterranean regions, due to the great spatio‐temporal variability of mediterranean environmental conditions, tree rings are sometimes not formed. Often, clear seasonality is lacking, and vegetation activity is not always associated with regular dormancy periods. We present examples of tree‐ring morphology of five species (Arbutus unedo, Fraxinus ornus, Quercus cerris, Q. ilex, Q. pubescens) sampled in Tuscany, Italy, focusing on the difficulties we encountered during the dating. We present an interpretation of anomalies found in the wood structure and, more generally, of cambial activity in such environments. Furthermore, we propose a classification of tree‐ring formation in mediterranean environments. Mediterranean tree rings can be dated and used for dendrochronological purposes, but great care should be taken in selecting sampling sites, species and sample trees.

Ozone — A Risk Factor for Trees and Forests in Europe?

Tropospheric ozone (O3) may adversely affect tree growth, with critical levels for O3 being exceeded in many parts of Europe. However, unequivocal evidence for O3-induced foliar injury on woody species under field conditions has only been found in a few places. Visible O3 injury appears to occur mainly in the Mediterranean Basin, which is also the area where the least amount of information is available on O3 exposure as well as the sensitivity of individual species. Overall, the quantitative risk assessment of O3 impacts on mature trees and forests is vague at the European scale, as most knowledge is derived from controlled O3 fumigations of young trees, grown in isolation in exposure chambers. Research suggests that risks exist, but these need to be validated for stand conditions. O3-induced changes in resource allocation rather than productivity appear to be crucial as they affect competitiveness and predisposition to parasite attack and may eventually lead to the loss of genetic diversity. ‘Free-air’ O3 fumigations in forest canopies may reveal processes that are susceptible to O3 stress under field conditions and provide a scientific basis towards quantitative risk assessment and realistic definitions of critical levels for O3 in forest ecosystems.

Ozone exposure thresholds and foliar injury on forest plants in Switzerland.

Canton Ticino in southern Switzerland is exposed to some of the highest concentrations of tropospheric ozone in Europe. During recent field surveys in Canton Ticino, foliar symptoms identical to those caused by ozone have been documented on native tree and shrub species. In Europe, the critical ozone level for forest trees has been defined at an AOT40 of 10 ppm.h O3 (10 ppm.h accumulated exposure of ozone over a threshold of 40 ppb) during daylight hours over a six-month growing season. The objective of this study was to determine the amount of ambient ozone required to induce visible foliar symptoms on various forest plant species in southern Switzerland. Species were grown within eight open-top chambers and four open plots at the Vivaio Lattecaldo Cantonal Forest Nursery in Ticino, Switzerland. Species differed significantly in terms of the ppb.h exposures needed to cause visible symptoms. The most to least symptomatic species grown within open-plots in this study rank as Prunus serotina, Salix viminalis, Vibrnum lantana, Rhamnus cathartica, Betula pendula, Rumex obtusifolius, Sambucus racemosa, Morus nigra, Prunus avium, Fraxinus excelsior, Rhamnus frangula, Alnus viridis, Fagus sylvatica and Acer pseudoplatanus. Similar rankings were obtained in the non-filtered chamber plots. The ranking of species sensitivity closely follows AOT values for the occurrence of initial symptoms and symptom progression across the remainder of the exposure season. Species that first showed evidence of foliar injury also demonstrated the most sensitivity throughout the growing season, with symptoms rapidly advancing over ca. 25-30% of the total plant leaf surfaces by the end of the observation period. Conversely, those species that developed symptoms later in the season had far less total injury to plant foliage by the end of the observation period (1.5 to < 5% total leaf area injured). The current European ambient ozone standard may be insufficient to protect native plant species from visible foliar injury, and many more native species may be sensitive to ozone-induced foliar injury than are currently known.

High-altitude and high-latitude tree growth in relation to past, present and future global climate change:

Recent dendroecological studies indicate that the growth rates of trees at some high-latitude and high-altitude sites are increasing. The date of the onset of increased growth is variable ranging from AD 1850 to 1940, with more recent increases occurring in less climatically-stressed areas. The growth data are supported by studies of tree-line dynamics which indicate that many northern and alpine tree- lines have advanced within the last 100 years. Although the causes of the growth increases are uncertain, climatic change appears to be the most likely explanation. As neither growth rates nor the northern extent of forests matches levels reached in the mid-Holocene, when the climate was considerably warmer, the mid-Holocene may represent a useful analogue for studies to predict the effects of global warming. However, in some areas, fertilization by atmospheric nitrogen is likely to be involved, and the possible impact of CO2 fertilization cannot be discounted. Unravelling the effects of these different factors represents a major challenge to dendroecologists.

Observation and Confirmation of Foliar Ozone Symptoms of Native Plant Species of Switzerland and Southern Spain

Tropospheric ozone is considered as the major pollutant of concern to the health and productivity of forests in the eastern United States and has more recently become of increasing concern within the forests of southern Europe. Recent observations have clearly demonstrated foliar injury symptoms to be occurring on many tree and native plant species within remote forested areas. Several plant genera (and a few species within genera) found in both the forests of Switzerland and the southern coastal region of Spain exhibit field symptoms typical of ambient ozone exposures. Ozone exposures for many species have been conducted under controlled CSTR conditions and within open-top chambers within the study areas. Results have confirmed that the O3-like foliar symptoms as observed under natural forest and open grown conditions for many native tree, shrub, and herbaceous species in Spain and Switzerland are caused by exposures to ambient O3.

Incorporating Climate Change Adaptation Considerations into Forest Management Planning in the Boreal Forest

SUMMARY Climate change will pose increasing challenges to forest managers working to achieve sustainable forest management in the boreal forest. To date, discussions around when, where and how to consider adaptation in forest management plans for the boreal forest have been limited. As a starting point, specific objectives for climate change adaptation need to be articulated, which we consider to be synonymous with the criteria for conservation and sustainable management of boreal forests as defined by the Montréal Process. Secondly, because forest management plans are hierarchal — there are higher level strategic plans and lower level operational plans — it is important to distinguish at which planning level adaptation options are most appropriately considered. The purpose of this paper is to put forward a range of alternative adaptation options that forest managers working in the boreal zone could consider during the development of strategic and operational forest management plans in order to achieve sustainability as defined by the Montréal Process.

Potential sampling bias in long-term forest growth trends reconstructed from tree rings : A case study from the Italian Alps

Abstract Tree-ring studies of long-term growth trends have often produced controversial results. In such studies, the largest-diameter trees in a stand are usually sampled. We assessed the influence of stand dynamics on long-term growth trends by examining the past diameters of all the trees living in two uneven-aged subalpine Norway spruce (Picea abies (L.) Karst.) stands in the Italian eastern Alps, as reconstructed from ring widths. The trees were ordered according to diameter, and groups of 12 trees (the 12 largest, the 12 smallest, etc.) were formed. Different diameter groups have different increment curves. In both stands, the 12 largest trees in 1992 have not had consistently faster growth rates than smaller trees. This indicates that changes in diameter ranking order have occurred in the past and may be expected in the future. During stand development, changes occur in the relative position of individual trees, as ordered by diameter. The largest-diameter trees, at any time, may not always have been the largest trees and may not continue to be so. In a given year, the largest trees on average grow slower than other trees, which will become the largest in the future. The mean chronologies of the trees that were among the largest, prior to the harvest, and which presently (in 1992) are no longer in the top 12, and the mean chronologies of the trees that have moved up into the top 12 show very different growth trends. If analysed out of context, they would be interpreted differently, leading to different conclusions on long-term growth trends. When only the 12 largest-diameter trees are sampled, a bias may be present, as the trees may not have been open grown and free of competition in the past. Consequently, studies of long-term growth may be seriously affected by bias attributable to stand dynamics and sampling strategies. In future studies, the growth patterns of all diameter classes in a stand should be assessed, rather than restricting the sampling to the largest diameters.

Application of Structured Decision Making to an Assessment of Climate Change Vulnerabilities and Adaptation Options for Sustainable Forest Management

A logical starting point for climate change adaptation in the forest sector is to proactively identify management practices and policies that have a higher likelihood of achieving management objectives across a wide range of potential climate futures. This should be followed by implementation of these options and monitoring their success in achieving management objectives within an adaptive management context. Here, we implement an approach to identify locally appropriate adaptation options by tapping into the experiential knowledge base of local forest practitioners while at the same time, building capacity within this community to implement the results. We engaged 30 forest practitioners who are involved with the implementation of a regional forest management plan in identifying climate change vulnerabilities and evaluating alternative adaptation options. A structured decision-making approach was used to frame the assessment. Practitioners identified 24 adaptation options that they considered important to implement in order to achieve the regional goals and objectives of sustainable forest management in light of climate change.

Consistency of observations of forest tree defoliation in three European countries.

The crown densities of 186 trees of five common European tree species (Norway spruce (Picea abies), silver fir (Abies alba), Scots pine (Pinus sylvestris), oak (Quercus robur) and beech (Fagus sylvatica) were assessed simultaneously by observation teams from France, Germany and the United Kingdom. Major differences in the scores existed, with the maximum difference on any one tree being 45%. Differences tended to be consistent, with the French team scoring more lightly than the German team and the German team more lightly than the UK team. The differences throw into question the value of international comparisons of forest condition, particularly the use of comparative tables of the extent of “forest decline” in individual European countries.

Biomass burning and its inter-relationships with the climate system

1. Biomass burning and climate: an introduction J.L. Innes. 2. Global Biomass Burning: A Case Study of the Gaseous and Particulate Emissions Released to the Atmosphere During the 1997 Fires in Kalimantan and Sumatra, Indonesia J.S. Levine. 3. Modelling the Effect of Landuse Changes on Global Biomass Emissions S.A. Ferguson, et al. 4. Direct effects of fire on the boreal forest carbon budget E.S. Kasischke, et al. 5. The impact of biomass burning on the global budget of ozone and ozone precursors C. Granier, et al. 6. Impact of the 1997 Indonesian fires on tropospheric ozone and its precursors D.A. Hauglustaine, et al. 7. The Relationship Between Area Burned by Wildland Fire in Canada and Circulation Anomalies in the Mid-Troposphere W.R. Skinner, et al. 8. Underestimation of GCM-calculated short-wave atmospheric absorption in areas affected by biomass burning M. Wild. 9. Wildland Fire Detection from Space: Theory and Application D.R. Cahoon, et al. 10. Climate and vegetation as driving factors in global fire activity E. Dwyer, et al. 11. Modelling the impact of vegetation fires, detected from NOAA-AVHRR data, on tropospheric chemistry in Tropical Africa D. Stroppiana, et al. 12. A rule-based system for burned area mapping in temperate and tropical regions using NOAA/AVHRR imagery J.M.C. Pereira, et al. Fire regime sensitivity to global climate change: An Australian perspective G.J. Cary, J.C.G. Banks. The interaction between forest fires and human activity in southern Switzerland M. Conedera, W. Tinner. 15. Indirect and Long-Term Effects of Fire on the Boreal Forest Carbon Budget E.S. Kasischke, et al. 16. Sustainable forestry as a source of bio-energy for fossil fuel substitution M. Lal, R. Singh. Managing Smoke in United States Wildlands and Forests: A Challenge for Science and Regulations D.G. Fox, et al. 18. Area burned reconstruction and measurement: a comparison of methods C. Larsen. 19. Interactions between biomass burning and climate: Conclusions drawn from the Workshop J.L. Innes, et al. Abbreviations and Acronyms. Index.