Buchmann Nina

Water availability and tree growth of scots pine and pubescent oak - a multiproxy analysis

Project Number: CH-4824
Project Type: Dissertation
Project Duration: 11/25/2006 - 06/30/2008 project completed
Funding Source: ETH ,
Leading Institution: ETH Zürich
Project Leader: Prof. Nina Buchmann
Institut für Agrarwissenschaften (IAS)
ETH Zürich
ETH Zentrum, LFW C 56
Universitätsstr. 2
8092 Zürich
Phone: +41 (0) 44 632 39 59 ; +41 (0) 44 632 30 83
FAX: +41 (0) 44 632 10 37
e-Mail: nina.buchmann(at)usys.ethz.ch

related to this project.
for which the project has a relevance.

Research Areas:

environmental sciences

Drought induced forest decline will gain in importance as the frequency and severity of drought events is expected to increase during the 21st century. Drought has also been discussed as a major cause for the decline of Scots pine (Pinus sylvestris L.) in the dry inner- Alpine valleys.

The impact of drought on tree performance, meaning the successful growth of trees, was examined in this thesis. The project aimed 1) to analyse the impact of severe drought on tree performance in the dry, low-elevated forest belt of the Swiss Rhone valley and 2) to evaluate the potential of Scots pine to maintain its dominance in these forests even under a projected hotter and drier climate. Tree growth under drought was analysed using different proxies (radial increment, wood anatomical parameters and stable carbon isotopes) on two time scales (inter- and intra-annual) using two different approaches (survey and experiment). The specific objectives of this thesis were 1) to identify the growth adaptation of Scots pine and pubescent oak (Quercus pubescens Willd.) to drought focussing on the inner-tree water conducting system, 2) to quantify the impact of drought and crown density on timing, quality and amount of wood formation in Scots pine and 3) to assess the process of storage depletion in Scots pine and estimate species potential to perform in a future climate.

Chapter I analyzed the adaptation of the water conducting system to drought for Scots pine and pubescent oak. Therefore tree growth at a passively irrigated site along an open water channel was compared with growth under naturally dry conditions. Under drought, the water conducting system of Scots pine consisted of fewer conduits with thinner cell walls but bigger lumen diameters. In contrast, the conduits were smaller in pubescent oak under drought. In addition, latewood width and therefore also the number of latewood vessels, was reduced. Tree growth of Scots pine was more dependant on water availability than tree growth of pubescent oak. Thus pubescent oak might have gradual advantages over Scots pine. However, also the growth of pubescent oak was retarded by drought, as seen by the frequent absence of latewood. Thus its success as a substitute species for Scots pine in a drier and hotter climate is doubtful.

In chapter II the synergetic impact of drought and crown density, as an estimator for tree vigour, on tree growth of Scots pine was analysed on an inter- and intra-annual scale within an irrigation experiment. The results showed that even trees of low crown density are able to recover from drought under improved environmental conditions, as all trees profited from irrigation, as seen for example, by the increasing tree-ring width. Irrigation also led to a prolonging of the growth period by up to five weeks. Low crown density in combination with drought had a strong negative synergistic effect on tree growth as seen for example, by the long-lasting growth reduction after the drought year 2003 in trees of mid and low crown density. This might be due to progressing storage depletion; therefore the resistance against stressors might be rather low. As a result, increasing mortality, especially in tress of low crown density, should be expected under ongoing climate change.

In chapter III the analysis focused on the carbon metabolism and in particular on the process of storage depletion in Scots pine of diverse crown density classes, studied by ?13C analysis on an inter- and intra-annual time scale. Results on the intra-annual scale showed that the assimilates produced at the beginning of the growth period were not sufficient to cover the carbon demand for tree growth. Thus stored carbohydrates were used for tree growth, even more in trees growing under low water supply. This continuous consumption of carbon reserves leads to storage depletion if the storages cannot be replenished within the growth period. On the annual scale, a high correlation between earlywood ?13C and the current drought index and the immediate response of ?13C to irrigation indicates high turnover rates. If high turnover rates were due to a reduced storage-pool, then all trees on dry sites, even if no or only slight signs of decline were observable in the crowns, would increasingly suffer under drought.

The results of the thesis contribute to a better understanding of the mechanistic role of drought in Scots pine decline, with implications not only for the future landscape development in Valais, but also for other dry regions in the inner-Alps. Under the assumption of a hotter and drier future climate, increasing mortality rates of Scots pines should be expected. Pubescent oak might act as a substitute species for Scots pine in today’s climate but our results also indicate that in a hotter and drier climate pubescent oak might also soon reach the physiological limits.

URL: http://e-collection.library.ethz.ch/eserv/eth:116/eth-116-01.pdf

Eilmann, Britta. 2008. Water availability and tree growth of scots pine and pubescent oak - a multiproxy analysis. Dissertation, ETH Zürich.

Herzog, Claude Phillip. 2017. Growth and Decay of Scots Pine Roots. Dissertation. ETH Zürich. pdf Dissertation

Last update: 4/5/22
Source of data: ProClim- Research InfoSystem (1993-2024)
Update the data of project: CH-4824

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