Download Wroc*aw, 05

To the Dean
of the Faculty of Science
Masaryk University
Prof. Dr. Jaromir Leichmann
Kotlářská 3
611 37 Brno
Wrocław 29.04.2016
REVIEW OF THE PHD THESIS
Candidate:
Topic:
Mgr. Dana Michalcová
Spatial distribution of small scale vegetation diversity in the landscape
Mrs. Mgr. Dana Michalcová has submitted a dissertation thesis consisting of a series
of four papers focused on grasslands diversity in a heterogonous landscape. Three papers
have already been published in high impact factor international journals and one has also
been submitted in a high good quality journal and I am convinced that this manuscript will
be accepted for publication. In three papers Mgr. Dana Michalcová is the first author.
The thesis is focused on the effect of landscape heterogeneity on species diversity in
grassland communities. First, the PhD candidate made an attempt to critically assess the
usability of vegetation-plot data gathered in phytosociological databases in the assessment
of species richness and other important vegetation attributes. The PhD candidate also
evaluated factors affecting the various levels of biodiversity, in particular, alpha diversity
with respect to the proportion of grassland areas and heterogeneity of the landscape. The
next stage of her research was to investigate the role of ecotones in influencing biological
diversity in a diverse landscape. In the manuscript, six goals were introduced. The main goals
of her study are well defined and concern many important ecological questions. The
structure of the manuscript is clear and well-thought-out and consists of two parts. The first
part includes an introduction to the problem, description of the methods, the results of the
study and a comprehensive discussion with proper citations. The latter part consists of a set
of papers.
The first paper highlights the importance of methodological aspects concerning the
use of data from electronic vegetation-plot databases in the assessment of species diversity
in forest vegetation. Preferentially collected historical data has been confronted with
a relatively complementary data set collected using stratified-random sampling. The results
of this study showed differences in the representation of certain pre-defined plant groups
and the tendency of phytosociologists to sample species-rich stands of vegetation. These
results are not, however, unambiguous because species richness was biased by preferential
sampling only in one of the two cases considered. The paper clearly pointed out that
historical vegetation-plot data does not bias all of the estimates of vegetation parameters.
Moreover, the subjective positioning of plots is important for the description of beta
diversity patterns. The scope of this research is very important for the ecological studies and
vegetation surveys carried out at different spatial scales. Mgr. Dana Michalcová clearly
showed that the inference based on data from phytosociological databases must be treated
with caution. This study stimulates discussion and reflection among vegetation scientists and
raises many questions. How to treat data stored in databases, particularly in relation to
changes in the concepts of species and methodological assumptions of data collection? Does
phytosociological data collected over many years, in a rather conservative and mainly
preferential way, require special treatment that would reduce bias? What are the
possibilities to reduce bias in the results and subsequent interpretation? Does a direct
comparison of historical and contemporary data, which was collected in different ways and
by different authors, can create another bias?
The two subsequent papers are devoted to the problem of the impact of various
environmental factors and the structure of the landscape on different levels of diversity
(particularly alpha diversity). The studies were carried out in the White Carpathians, several
other neighbouring areas and in Slovakia. The papers present very interesting results
explaining the relation between species diversity patterns and the landscape diversity. It has
been shown that gamma diversity of the White Carpathians at a regional scale is not
different from other areas studied. It has been proved, however, that extremely high alpha
diversity of grasslands in the White Carpathians is, to some extent, due to the presence of
a large mosaic of habitats with a relatively homogeneous geological structure. This creates
a specific and complex combination of species. Another important result demonstrated that
grassland vegetation found in a complex of semi-natural or natural vegetation is
characterized by high alpha diversity. It has also been shown that alpha diversity depends on
the vicinity and coverage of grasslands of a similar origin. Accordingly, species diversity of
grassland decreases with the increasing share of non-natural habitats in the closest
surroundings. The reverse pattern was found for beta and gamma diversity. Human-induced
landscape alterations have a strong impact on the alpha diversity of sub-xerophilous and
mesophilous grasslands, while xerophilous and wet grasslands are less affected. How to
explain this relationship? It has been demonstrated that the structure of landscape seems to
be one of the most important factors shaping a semi-natural vegetation, but not forest
vegetation. The results of this study are very interesting and are an essential part of the
research. What is the role of land use in this context, and abandonment in particular? My
attention was drawn by the sample size of data sets used for the analysis. Could a different
number of samples collected in each region affect the results?
The last part of the research is devoted to the role of ecotones in maintaining
biodiversity. This is a very well elaborated study with interesting information about
ecotones. Transition zones between different plant communities and their importance for
species persistence in the landscape have been poorly studied so far, or contradictory results
have been published. Generally, it is recognized that they are usually species-rich and some
species are considered to be specific to these ecosystems. According to the research of the
PhD candidate, there are no significant differences in species richness between ecotones and
adjacent homogenous ecosystems. Of particular interest is the result of questioning the role
of ecotones in the spread of alien species, especially in relation to the intensively managed
agricultural landscape. The results of this study did not confirm that ecotones may serve as
refugia for rare species or archaeophytes, nor do they increase species pool in the
landscape. Moreover, they are not a high diversity refugia and do not counteract the
negative effect of fragmentation in the agricultural landscape. In the light of these results,
we can learn more about these peculiar ecosystems. The submitted paper is of high scientific
value and, in my opinion, should successfully be published in a good quality journal with
a high impact factor. This topic is especially important for landscape ecology. Unclear,
however, is why it was decided to use a quite subjectively defined plot area in the transect?
Also, some other questions concerning sampling scheme arise. Did the authors consider
dividing the basic plot area, especially within a single ecotone, into smaller plots (e.g. 1m 2) to
determine the extent of ecotone community? How did the authors define ecotones between
similar communities? Was the distribution of species from homogenous communities
symmetric or asymmetric in ecotones? Can some of the ecotones in this study be distinct
syntaxonomical units?
The results of this study are of great practical importance because they show that
landscape fragmentation and the disappearance of natural and semi-natural habitats from
the landscape may result in the reduction of species diversity. It can therefore be argued
that the ecotones do not compensate the loss of valuable habitats because the persistence
of ecotones in the landscape is not enough to protect biodiversity and endangered species in
particular.
All papers included in the dissertation are kept in a single train of thought. They are
well-planned and methodologically sound. The methods used in the analyses are
appropriate and meet the standards of high-quality international journals. Of particular
attention is the R script of sample-based rarefaction curves. The manuscript itself is well
written and concise. The results are presented in a clear manner and references are
appropriately cited in the comprehensive discussion. Most importantly, all the results from
this research are essential for scientists working in the field of ecology, vegetation survey,
and agriculture and ecosystem restoration.
Mgr. Dana Michalcová is an ambitious young scientist contributing to the
development of the Czech National Phytosociological Database. Additionally, she is involved
in several projects, out of which Atlas of plants of the CZ for mobile devices is particularly
interesting. Moreover, several posters and oral presentations were given by the applicant at
international scientific conferences. In conclusion, Mgr. Dana Michalcová is a professional
scientific researcher. The results of her study are of great importance for the international
scientific community and also for nature conservation practitioners. I have no doubts that
Mgr. Dana Michalcová deserves to be awarded a doctoral degree.
dr hab. Zygmunt Kącki
Department of Vegetation Ecology
University of Wrocław