Projects

Project 5: Monitoring tree-ring formation

Started in 2007

Description: Tree rings have proved to be an invaluable source of environmental information. Clear evidences of relationships between tree growth and the environmental conditions have soon been identified and used by dendrochronologists to look into the past and in some cases also to infer future predictions under different scenarios of changes. So for example tree rings have been used to date anthropogenic activities, to reconstruct the climate of the past, to study the dynamic of forest growth and succession, to reconstruct the history of ecological events as forest fires, insect outbreaks or geomorphologic processes, or even to quantify hydro- and biochemical cycles. All these information are stored into the characteristics of the rings, as the ring width, the density profile, the chemical composition of the wooden matrix or the anatomical characteristics of the cells.

However, depending on species and environmental settings, this ecological information can appear strongly expressed or diffusely masked by other concurring information. More detailed mechanistic understanding the process of environmental registration is tree rings is thus required to fully exploit the further available information. Thanks to continuously improving measuring techniques and tools there is an increasing capacity in looking with increased resolution into the tree-rings, which might opens new frontiers in environmental research towards the possibility to distinguish between different seasonal signals. An unavoidable and fundamental step towards a mechanistic understanding of the registration process is however the ability to provide a detailed description and timing of ring formation. When during the season, under which environmental condition is what structure produced, are fundamental questions in order to link cause and effect and simultaneously it also provides additional important elements to understand the physiology of tree growth.

This project is aimed at understanding the process of ring formation by monitoring the intrta-annual growth along an altitudinal gradient in the Loetschental.

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Project 4: Tree-ring anatomy

Started in 2004

Description: The anatomy of the wood of trees is to some extent genetically predisposed and to some extent controlled by variable environmental influences. As trees need to adapt their developmental processes to the prevailing environmental situations (e.g. during winter dormancy, bud break or onset of cambium activity), the resulting changes in the underlying metabolic pathways can be traced through time and at various levels. This can be performed either by direct measurements or on the basis of cytological, cellular or morphological manifestations. Whereas physiological manifestations are transitory, others such as cell and cell wall anatomy are permanently ‘archived’. Provided that an exogenous influence had been limiting tree growth for a certain time and intensity, environmental information are recorded by and accessibly stored in a tree and can be analyzed retrospectively .

Various techniques are dealing with the way of ‘opening’ such archives to obtain ecophysiological information. Dendrochronologically dated tree rings, due to their annual resolution, are widely exploited to reconstruct past ecological conditions . Among the features available from tree rings, the width is mostly used; it integrates the prevailing conditions throughout the whole growing period and, with decreasing intensity, of several prior years. However, the identification and understanding of many ecological processes require a resolution higher than one year, so that new proxies in dated tree rings need to be explored in order to reconstruct past ecological events more precisely. In this sense, wood density had become a successful character since the 1970s, allowing to reconstruct summer temperature along the boreal forest border. More recently, the year-to-year variation of the stable isotopes of carbon, hydrogen and oxygen in the polymers of the wooden cell walls was disclosed as a valuable information carrier. But the recent technical and software advances in automatic optical measuring systems allow to look out for proxies with even greater potential and thus promoted quantitative wood anatomy to a most promising candidate.

Wood anatomical features are the direct result of cambial activity. They often enclose ecologically relevant information and constitute the basis for ‘ecological wood anatomy’ in that, e.g., the dimensions and density of water conductive cells are related to site conditions and differences in these features among tree species or populations indicate long-term adaptations along ecological gradients. But the same wood anatomical features enclose also year-to-year and, moreover, intra-annual variations according to the conditions shortly before and during the growing period, so that time series can be obtained and studied retrospectively.

Few current publications have shown the potential of annually dated quantitative wood-anatomical features. For example, clear relationships between climate and the size of the conductive cells in trees, such as tracheids in conifers or vessels in broad-leaved trees, have been disclosed for conifers, diffuse-porous hardwoods, and for ring-porous hardwoods. However, numerous tree species and ecosystems have still to be screened to verify the capability of quantitative wood-anatomical candidates in different environments.

We are of the opinion that tree-ring anatomy is an emerging topic with promising perspectives in current tree/climate research. This project is aimed at collecting new data and exploring the potential of this innovative approach.

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Project 3: Forest dynamic in abandoned chestnut coppices

Duration: 2003 – 2009

Description: Sweet chestnut (Castanea sativa Mill.) is a tree species that has been intensively cultivated for centuries as a monoculture (coppices and orchards), even at the limits of its potential ecological range. Chestnut forest ecosystems still represent an important landscape component in the mountainous regions around the European Mediterranean basin and in the Southern Alps, covering more than 2.2 million ha. Since the early 1950s, however, changes in the socio-economic structure of the rural areas and the spread of chestnut diseases such as chestnut blight (Cryphonectria parasitica (Murr.) Barr.) and ink disease (Phythophtora spp.) have caused a decline in the cultivation of sweet chestnut forests in many European regions. As a result, both coppices and orchards were abandoned and gave way to a more natural forest development. Chestnut coppices, which for millennia have been regularly and intensively managed for fast timber production, have long exceeded their usual rotation length (< 20 years). Today, they are over-aged and highly monotonic in structure. Analyses of stand development and of competition processes between Castanea sativa and other species are crucial for understanding current and future forest succession processes and for anticipating landscape development within the extended chestnut belt of the Southern Alps.

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Project 2: Investigation into ring shake of chestnut (Terminated)

Duration: 2000 – 2002

Description: This project was concerned with the development of ring shake, a wood defect that very often occurs in European chestnut (Castanea sativa Mill.). These studies must be placed in a general research context aimed at assembling a better picture of the complex phenomenon of ring shake in order to evaluate new preventive measures that contribute to minimise the risk of ring shake occurrence.

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Project 1: Valorization of chestnut wood from abandoned chestnut coppices (Terminated)

Duration: 1998 – 2002

Description: Chestnut (Castanea sativa Mill.) coppice is a man-made forest type that has been managed for centuries in short rotations to rapidly produce woody biomass. These forests, which nowadays cover significant areas within Europe, experience a general neglect and are subsequently being abandoned. Most of them are now over-aged, very dense, and highly monotone. Wood produced is thought to be invaluable and therefore lack of silvicultural treatments. This project intends to evaluate the potential that such abandoned forest have in supplying quality wood and propose measures for an improved exploitation.

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