B O O K
R E V I E W
Applied Tree Biology Is a Must-Read
Reviewed by Steven Pregler
by Andrew Hirons, Ph.D., and Peter A. Thomas, Ph.D.
432 pages
Published by Wiley-Blackwell; first edition, January 9, 2018
Lots of book reviewers start by proclaiming that the book they
are reviewing is a must-read or a must-have reference. Well, this
review of Applied Tree Biology is no different! In fact, some of the
information presented in this book, in my opinion, is so fresh
and relevant to the practicing arborist that it should be included
in future ISA Certified Arborist study guides. That’s a powerful
statement to make, but I believe this information to be that rele-
vant to our basic understanding of trees.
This manual is technical in nature, just as the title indicates. But,
and this is a big “but,” it is written for arborists in a language I
think any Certified Arborist should be able to understand. Sev-
eral chapters contain information and explanations I have never
seen before. They made the proverbial lightbulb go on in my
head several times. I have gained a deeper understanding of
topics that apply to what we do as arborists every day. The
authors, in fact, have done an awesome job of summing up and
relating the information to what we do every day! By the time
I had completed reading Applied Tree Biology, it was filled with
yellow highlights and a dozen or so page markers.
Each chapter in the book is, more or less, theme-related, with
some of the best colored photos, drawings and tables I have seen
used to further the authors’ transfer of knowledge. A picture
truly is worth a thousand words.
One of my favorite chapters (Chapter 6) is on tree-water rela-
tions and describes water absorption and redistribution within
the tree. The diagrams of tree anatomy and descriptions of the
physiology involved painted a pretty clear picture. I found
hydraulic redistribution to be a new and very interesting facet
of tree biology. It explains how a tree moves water from moist,
deeper roots to dry, shallow roots. It also describes how a tree,
through foliar uptake, moves moisture from very humid air into
and through the trees crown and down to the root system in a
dry-soil environment. I now understand the circumstances or
variables that must exist for these survival mechanisms to work.
Do you understand the variables that influence stomata closure
and the slowing of transpirational pull? If you’re an arborist
injecting trees, this information is very useful. Have you heard of
cavitation and embolisms and how they will adversely affect
water distribution within the tree and to the tree’s upper crown?
The book describes how freeze-and-thaw cycles, drought condi-
tions and physical injury to the xylem, such as when we create
18 MAA NEWS / June 2019
Figure 6.6: Alternative types of hydraulic redistribution in trees
pruning wounds, are the three primary causes of cavitation.
When providing a diagnosis for the cause of decline symptoms
in a tree’s crown, this knowledge may be of value not only in for-
mulating a reasonable scenario, but also in explaining to a client
why or how it is happening.
Another favorite chapter was on tree nutrition (Chapter 8). The
authors do a great job of describing the 14 known essential nutri-
ents a tree needs to live, their functions within the tree and the
available forms that can be used by the tree and how they are
acquired. There is a great table to refer to showing this. There is
also a helpful chart to use when diagnosing nutritional deficien-
cies. For example, if you are looking at symptoms on old or
mature leaves, it describes a symptom and which nutrient may be
responsible for the disorder. It also describes symptoms and their
possible causes if symptoms are seen on the youngest leaves.
Two other chapters that captivated my attention were “Interac-
tions with Other Organisms” (Chapter 9) and “Environmental
Challenges for Trees” (Chapter 10).
At the end of each chapter, there is a “References” section allow-
ing readers to further research the works of other authors whose
work was quoted in this book. I purchased my copy of the book
on Amazon for $50. I wish the book had a hard cover, but it was
still worth the price!
Be forewarned, if you’re like me, you won’t be able to put Applied
Tree Biology down. Rest assured, when you’re finished with it,
you will have a much better understanding of trees, how they
grow and how to treat them.
Steven Pregler is an ISA Certified Arborist and retired city forester for the City
of Dubuque, Iowa. Reprinted with permission: Tree Care Industry magazine,
September 2018.