Dislich, C. (2012): <b>The role of life history traits for coexistence and forest recovery after disturbance ? a modelling perspective. Towards a better understanding of species-rich forests</b> University of Bayreuth, <i>phd thesis</i>
Resource Description
Title:
Über die Bedeutung von Arteigenschaften für Koexistenz und Waldregeneration nach Störungen ? Eine Modellierungsstudie zum besseren Verständnis artenreicher Wälder
Short Name:
The role of life history traits for coexistence and forest recovery after disturbance
FOR816dw ID:
1091
Publication Date:
2012-04-10
License and Usage Rights:
Resource Owner(s):
Individual:
Claudia Dislich
Contact:
email:
claudia.dislich <at> ufz.de
UFZ Centre for Environmental Research Leipzig-Halle
Department of Ecological Modelling
Permoserstrasse 15
04318 Leipzig
Germany
Abstract:
Tropical forests are well known for their exceptional species richness ? high diversity of<br/>
plant species constitute the basis for an equivalently rich fauna. An astonishing variety<br/>
of plant life strategies has evolved, manifesting itself also in different compositions of life<br/>
history traits in trees. This thesis investigates the role of tree life history traits (growth,<br/>
mortality and recruitment) on different processes structuring species-rich forests. Our<br/>
study system is a montane rainforest located in the Tropical Andes hotspot of biodiversity<br/>
in southern Ecuador. Here, we find a mosaic of steep ridges and deeply incised<br/>
valleys, covered with predominantly broadleaf forest. Forest structure and species composition<br/>
differ considerably depending on altitude and topographic position. The forest<br/>
cover is frequently interrupted by scars of landslides, which constitute an important type<br/>
of natural disturbance in this ecosystem.<br/>
We utilize ecological models as tools to gain deeper insights into key processes driving<br/>
the maintenance of tree species richness and affecting forest recovery after landslides.<br/>
The first part of this thesis concerns the question of species coexistence. We develop<br/>
a theoretical model to analyze how different trade-offs between life history traits (tree<br/>
growth, seed dispersal, tree mortality) affect tree species coexistence. We find that the<br/>
considered trade-offs alone are not sufficient to explain long-term species coexistence.<br/>
Additional ?stabilizing? mechanisms seem to be indispensable to facilitate coexistence in<br/>
species-rich forests. Such mechanisms could result from biotic interactions, that alter<br/>
the relation between inter- and intra-specific competition depending on (local) species<br/>
abundances (e.g. density-dependent mortality). Other possible coexistence mechanisms<br/>
likely to be relevant to our particular study system are driven by external, abiotic factors<br/>
like a complex topography resulting in locally differing habitat types (each supporting a<br/>
different set of species), or the character of a prevailing disturbance regime (e.g. shallow<br/>
landslides).<br/>
In the second part of the thesis, we investigate the growth dynamics of the ridge forest<br/>
in our study system. To this end, we utilize the process-based forest growth model<br/>
FORMIND. We show that after calibration, the model successfully reproduces forest<br/>
dynamics on different levels of complexity (e.g. basal area and stem size distribution).<br/>
We then use this forest model to investigate the influence of landslide disturbances on<br/>
forest dynamics both on the local scale of a single landslide and on the landscape scale.<br/>
On landslide sites, changes in environmental conditions might lead to changes in different<br/>
tree life history traits. We analyze scenarios with changes in different traits (tree recruitment,<br/>
tree growth, tree mortality) and find that while tree biomass can recover within the<br/>
first hundred years after a landslide, the time until forest structure and species composition<br/>
is restored is considerably longer (approximately 200 years). Changes in different<br/>
traits result in differing spatial distributions of tree biomass: reduced tree growth leads<br/>
to a more homogeneous distribution of biomass, whereas reduced recruitment and increased<br/>
mortality yield a more heterogeneous biomass distribution (?patchy? vegetation).<br/>
On the landscape level, overall forest biomass is substantially reduced by landslides (8 -<br/>
I<br/>
14%), compared to only 2 -3% of the area marked by visible traces of landslides. Thus<br/>
this particular type of disturbance considerably influences the total forest carbon balance.<br/>
In a complementary investigation we study abiotic and biotic factors that potentially<br/>
trigger landslide occurrence in our study system. For this, we develop an extension of<br/>
a standard physically-based model of slope stability. We find that due to the predominantly<br/>
shallow tree roots, some of the observed landslides might be triggered by the<br/>
vegetation itself.<br/>
This thesis demonstrates that ecological models are useful tools to gain deeper insights<br/>
into important processes shaping forest communities. They can be applied for theoretical<br/>
questions such as the question of species coexistence, as well as for more applied,<br/>
management related questions like predicting forest recovery after disturbances.
Literature type specific fields:
THESIS
Degree:
phd
Degree Institution:
University of Bayreuth
Total Pages:
129
Metadata Provider:
Individual:
Claudia Dislich
Contact:
email:
claudia.dislich <at> ufz.de
UFZ Centre for Environmental Research Leipzig-Halle
Department of Ecological Modelling
Permoserstrasse 15
04318 Leipzig
Germany
