Ecological effects of willow and poplar invasions at the Río Negro in northern Patagonia, Argentina

141 Pages·2015·3.09 MB·English

by  Lisa Thomas

Ecological effects of willow and poplar invasions
at the Río Negro in northern Patagonia, Argentina

Dissertation
zur
Erlangung des Doktorgrades
der Naturwissenschaften
(Dr. rer. nat.)

dem Fachbereich Biologie
der Philipps-Universität Marburg
vorgelegt von
Diplom-Forstwirtin Lisa Thomas
aus Freiburg i.Br.

Marburg/Lahn 2015
Vom Fachbereich Biologie der Philipps-Universität Marburg
als Dissertation am 10.06.2015 angenommen.

Erstgutachter: Prof. Dr. Ilona Leyer
Zweitgutachter: Prof. Dr. Gerhard Kost

Tag der mündlichen Prüfung: 06.07.2015
“The river [the Río Negro] is about two or three hundred yards wide, and is deep and rapid.
The many islands, with their willow-trees, and the flat headlands, seen one behind the other
on the northern boundary of the broad green valley, form, by the aid of a bright sun, a view
almost picturesque.”
Charles Darwin, The Voyage of the Beagle, 1839

List of papers

The main chapters of this thesis are based on two publications and two manuscripts with the
following authorships and titles. These papers are referred to in the text by the Roman
numerals I-IV.
I. Thomas L.K., Tölle L., Ziegenhagen B. & Leyer I. (2012) Are vegetative reproduction
capacities the cause of widespread invasion of Eurasian Salicaceae in Patagonian
river landscapes? PloS one 7, doi:10.1731/journal.pone.0050652.
II. Thomas L.K. & Leyer I. (2014) Age structure, growth performance and composition
of native and invasive Salicaceae in Patagonia. Plant Ecology 215, 1047–1056.
III. Thomas L.K., Mosner E. & Leyer I. (in press) River dynamics and invasion:
Distribution patterns of native and invasive woody vegetation at the Río Negro,
Argentina. Riparian Ecology and Conservation.
IV. Fettweis K., Thies B., Thomas L.K. & Leyer I. (manuscript) Detection of land cover
and vegetation change by invasive woody species spread at the Río Negro,
Argentina.

For paper I (Chapter 2), I assisted I. Leyer to develop the conceptual design of the study. I
sampled cutting material along the Río Negro. Together with L. Tölle I conducted the
greenhouse study and data analyses, and I had responsibility for the writing. For paper II
(Chapter 3), I created the general concept and the study design together with I. Leyer. I
conducted all the field work and analyses, and I was responsible for the writing. For paper III
(Chapter 4), I developed the concept of the study in collaboration with I. Leyer. I worked out
the study design, the statistical analyses and mainly wrote the manuscript. Regarding paper
IV (Chapter 5), I participated in developing the conceptual ideas, gave support during data
collection in Argentina and commented on the manuscript.

Table of Contents

Preface ............................................................................................................................. 1
Summary .......................................................................................................................... 3
Zusammenfassung ............................................................................................................ 7
Chapter 1 – Introduction ................................................................................................. 11
1.1 Riparian ecosystems and invasion .............................................................................. 11
1.2 Study area – the Río Negro ......................................................................................... 14
1.3 Woody vegetation along the Río Negro ..................................................................... 17
Chapter 2 – Paper I ......................................................................................................... 23
Are vegetative reproduction capacities the cause of widespread invasion of Eurasian
Salicaceae in Patagonian river landscapes?
Chapter 3 – Paper 2 ........................................................................................................ 41
Age structure, growth performance and composition of native and invasive
Salicaceae in Patagonia
Chapter 4 – Paper 3 ........................................................................................................ 61
River dynamics and invasion: Distribution patterns of native and invasive woody
vegetation at the Río Negro, Argentina
Chapter 5 – Paper 4 ........................................................................................................ 87
Detection of land cover and vegetation change by invasive woody species spread at
the Río Negro, Argentina
Chapter 6 – Synthesis ..................................................................................................... 117
6.1 Establishment of native and invasive Salicaceae ...................................................... 117
6.2 Interspecific competition processes ......................................................................... 119
6.3 Distribution patterns and invasion development ..................................................... 120
6.4 Perspectives and applications ................................................................................... 122
References ..................................................................................................................... 125
Dank .............................................................................................................................. 130
Erklärung ..................................................................................................................... 1333

Preface
Preface

This thesis was carried out within the German-Argentinean cooperation project
“Predicting the effects of invasion processes of Eurasian floodplain willows in Patagonia”
funded by the German Research Foundation (DFG grant LE 1364/4-1). To our knowledge, it is
the first study that deals with Salicaceae invasion and its consequences for a riparian
ecosystem in Patagonia and for Salix humboldtiana Willd., the only native willow species in
this region. Based mainly on field methods and modelling approaches I expected to gain
insights into ecologically related questions concerning invasion processes. This basic research
should provide a sound basis for understanding invasion of Salicaceae and for future
management and conservation strategies. Population genetic approaches (i.e. hybridization
and evolutionary processes) were conducted by the cooperation partner and compose a
different thesis.
A general framework of this thesis is given in the Introduction (Chapter 1) illustrating
the problem of invaded riparian ecosystems and, in particular, the invasion processes along
the Río Negro in Northern Patagonia. The thesis is subdivided into four main topics which are
represented each by a publication or manuscript. In Chapter 2 the vegetative reproduction
capacities of native and invasive Salicaceae were compared since the property to reproduce
vegetatively plays a main role for the establishment and invasion success. In an experimental
approach survival, growth performance and re-sprouting capacities were analysed for all
relevant taxa taking soil moisture and soil composition gradients into account. In the following
Chapter 3 age structure analyses were carried out to clarify establishment processes.
Measurements of growth performance in relation to the age of the trees of the four dominant
Salicaceae taxa in mixed forest stands were conducted. Therewith can be assessed whether
interspecific competition occur in older life stages in Salicaceae forests and, therefore,
whether the native species can co-exist in the future. Chapter 4 focuses on distribution
patterns and ecological niches of the dominant native and invasive woody species along the
Río Negro. Habitat distribution models were developed in order to relate abiotic factors (e.g.
flood duration, average water level, flow strength, soil texture) to the presence and absence
1
Preface
of different life stages of all target taxa. In the final paper (Chapter 5) land cover changes
during the last decades focussing on the spread of invasive species were analysed. Therefore,
remotely sensed Landsat satellite image data of the years 1986 and 2003 were compared in
order to identify vegetation changes at the upper Río Negro valley. Finally, the main results of
the chapters 2-5 are summarized and consequences for the conservation of S. humboldtiana
are pointed out in Chapter 6.

2