Research Collection Master Thesis Vegetation dynamics after forest fire in comparison to the pre- fire state Author(s): Temperli, Christian Publication Date: 2007 Permanent Link: https://doi.org/10.3929/ethz-a-005517791 Rights / License: In Copyright - Non-Commercial Use Permitted This page was generated automatically upon download from the ETH Zurich Research Collection. For more information please consult the Terms of use. ETH Library Vegetation dynamics after forest fire in comparison to the pre-fire state Diploma thesis, department of environmental science ETH, Zürich, carried out at the Swiss Research Institute WSL Christian Temperli December 2007 Reference: Co-reference: Prof. Dr. Harald Bugmann Dr. Thomas Wohlgemuth ETH Zürich WSL Swiss Federal Research Institute Institut f. Terrestrische Ökosysteme Disturbance Ecology Universitätstrasse 16 Zürcherstr. 111 CH-8092 Zürich CH-8903 Birmensdorf Switzerland Switzerland The regeneration of vegetation after the forest fire above Leuk, VS, Switzerland in 2003: Comparison to the pre-fire state and analyses with respect to climate, fire intensity and CWD. Cover picture: Fire patch above Leuk, VS, Switzerland on August 1, 2007. 2 Abstract Christian Temperli (2007): Vegetation dynamics after forest fire in comparison to the pre-fire state. Diploma thesis, departement of Environmental Science ETH, Zürich. A wild fire caused by arson destroyed in August 2003 300 ha of forest above the central alpine town of Leuk, Switzerland. The burned montane to sub-alpine forest ranged from 800 m.a.s.l. up to the timberline at 2100 m.a.s.l. at the south facing slope of the Valais main valley. As the succession processes along the large ecological gradient are of great interest in times of increased wild fire frequency they have been monitored since 2004. Additionally the local climate has been recorded by means of temperature and precipitation sensors installed in the fire patch. In line with this diploma thesis the vegetation data was compared to the pre-fire state and mainly analysed with respect to climate and fire intensity. Most species (re-)colonised the fire patch in the first two post-fire years. The highest species richness and vegetation covers were recorded at the most humid sites at high altitudes where temperatures and fire intensity were low. Until 2007 also the unfavourable hot and dry sites at lower altitudes where most of the soil was combusted by the fire were colonised by many species. The vegetation is still sparse at these sites though. The development of the species richness depends strongly on the scale in consideration. Whereas the species richness one year after the fire was surprisingly nearly as high as before the fire at a scale of 25 a it took four years to reach the pre-fire state on the small scale of 0.3 a. In the past two years high dominances of Epilobium angustifolium and Calamagrostis varia at higher altitudes and Conyza canadensi s and Rubus sp . at lower altitudes have developed. These species do not impede the regeneration of early colonising trees ( Populus tremula, Salix sp . and Betula pendula ). In contrary, the number of tree saplings found at the favourable sites at high altitudes was very high and regular succession climaxing in Norway spruce and Larch forest can be expected. Below 1200 m.a.s.l. the direction of the succession tends to Oak forest though. Keywords: Biodiversity, forest, regeneration, climate, fire, Valais . 3 Contents ABSTRACT ........................................................................................................................................................ 3 CONTENTS ........................................................................................................................................................ 4 1. INTRODUCTION ....................................................................................................................................... 6 2. METHODS ................................................................................................................................................ 9 2.1. STUDY AREA .............................................................................................................................................. 9 2.1.1. Geography .................................................................................................................................... 9 2.1.2. Climate ........................................................................................................................................ 10 2.1.3. Soils ............................................................................................................................................. 11 2.1.4. Vegetation .................................................................................................................................. 11 2.1.5. Fire impact on soils and vegetation ............................................................................................ 12 2.2. DATA COLLECTION .................................................................................................................................... 13 2.2.1. Vegetation data .......................................................................................................................... 13 2.2.2. Geographical data ...................................................................................................................... 14 2.2.3. Climate data................................................................................................................................ 15 2.3. DATA PREPARATION .................................................................................................................................. 17 2.3.1. Vegetation data .......................................................................................................................... 17 2.3.2. Climate data................................................................................................................................ 19 2.4. DATA ANALYSIS ........................................................................................................................................ 21 2.4.1. Statistical methods ..................................................................................................................... 21 2.4.2. Used measures ............................................................................................................................ 21 3. RESULTS ................................................................................................................................................. 25 3.1. BIODIVERSITY ........................................................................................................................................... 25 3.2. HERB LAYER COVER ................................................................................................................................... 26 3.3. HETEROGENEITY OF THE VEGETATION ........................................................................................................... 27 3.3.1. Patchiness ................................................................................................................................... 27 3.3.2. Similarity within plots ................................................................................................................. 28 3.4. SPECIES COMPOSITION ............................................................................................................................... 29 3.4.1. Similarity between post- and pre-burn species composition ...................................................... 29 3.4.2. Ecological groups ........................................................................................................................ 30 3.5. DOMINANT SPECIES .................................................................................................................................. 35 3.5.1. Dominance-diversity relation ...................................................................................................... 35 3.5.2. Species richness and Epilobium angustifolium cover .................................................................. 36 3.5.3. Effect of Epilobium angustifolium cover on the cover of other species ...................................... 37 3.5.4. Regeneration of trees and Epilobium angustifolium cover ......................................................... 37 3.5.5. Species richness and Rubus sp. cover .......................................................................................... 38 3.5.6. Effect of Rubus sp. cover on the cover of other species .............................................................. 38 3.5.7. Tree regeneration and Rubus sp. cover....................................................................................... 38 3.6. TREES BEFORE AND AFTER THE FIRE .............................................................................................................. 38 3.6.1. Tree layer before the fire in 1996 ................................................................................................ 38 3.6.2. Tree regeneration ....................................................................................................................... 39 3.7. ELEVATION .............................................................................................................................................. 42 3.7.1. Species richness ..........................................................................................................................