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New Phytol. (1999), 141, 369–371
Book reviews
Rothschild’s Reserves. Time and fragile nature. By
M ROTHSCHILD and P MARREN.
27±5¬21±5 cm. Pp. xv242 with 101 plates.
Rehovot, Israel : Balaban, 1997. Price p}b: £15.00,
ISBN 0 86689 048 3.
This book is a tribute to Charles Rothschild, who virtually
invented nature conservation in Britain. In the words of
the authors, his plan was to protect and preserve the varied
habitats of rare and dwindling species by setting up a
nationwide network of nature reserves. Two thirds of this
admirable book consist of descriptions of the fate of each
of the 182 English reserves which Charles Rothschild
listed for preservation. The initial chapters include a
biographical sketch of Charles Rothschild, who was clearly
a delightful person as well as a visionary naturalist. They
show how he set up the Society for the Promotion of
Nature Reserves in 1912 and with the help of its members
obtained the information he required to select his list of
282 sites in the British Isles worthy of preservation. His
great efforts to get support from Government, local
authorities and voluntary bodies are described. He was
largely thwarted by the exigencies of the First World War
and the excessive caution of all whom he approached. He
died in 1923, his dream unfulfilled.
The accounts of what has happened to Rothschild’s
Reserves and some of their rare species during the last 82
years make sad reading and show how the two destructive
forces of development and neglect have contributed to the
destruction or serious deterioration of over 40% of the
sites. I know many of the sites described, and a present-
day view supports nearly all the assessments. Perhaps
rather too little has been made of successful efforts by the
conservation organizations who now manage over half
Rothschild’s Reserves. Deterioration of habitats and hence
loss of species in the countryside surrounding most of the
Rothschild sites must indirectly have had deleterious
effects on the flora and fauna of the sites, as they
increasingly became islands in a sea of intensively farmed
land. This point needs to be emphasized. With these small
reservations, the assessment can be accepted as an
extremely valuable account of what happened between the
time Charles Rothschild and his helpers in the SPNR
made their survey and the time when his daughter Miriam,
and Peter Marren and their helpers made theirs. The
comparisons are particularly valuable because of the length
of time between the two surveys. While loss through
development is usually all too obvious, that through
neglect is insidious, because it is slow and can easily go
unrecognized, even by observers on the spot.
It took 35 years for Charles Rothschild’s scheme to be
put into action by the newly formed Nature Conservancy.
It is depressing how long it took for the British public,
which included numerous naturalists and biologists, to act.
There are signs that we are also being too slow in reacting
to the destruction of habitat which continues today.
Perhaps the main value of this book is to emphasize the
importance of nature reserves in today’s world. If only
Charles Rothschild’s advice had been taken 80 years ago
the situation today would be enormously better than it is.
So long as modern agriculture and forestry provide so few
habitats for our native flora and fauna, nature reserves are
absolutely crucial in maintaining populations of species
now largely banished from farm and forest land. They will
provide the sources from which the wider countryside can
be recolonized, if and when changed conditions allow.
Conservation agencies, both governmental and voluntary,
should be urged not to let up on acquiring and managing
new nature reserves. Regrettably, the pace seems to be
slackening; it should be increased. More nature reserves
would be the most fitting memorial to Charles Rothschild,
the pioneer.
Rothschild’s Reserves is beautifully illustrated with
photographs taken in the past and the present (in colour).
It should be read by all who are concerned with nature
conservation today.
N M
The phytogeography of northern Europe. By E
DAHL. 25 cm¬19 cm. Pp. xii297 with 82 text-
figures. Cambridge, UK: Cambridge Univeristy
Press, 1998. Price h}b: £60.00, ISBN 0 521 38358
7.
Eilif Dahl, who died in 1993, had a botanical carreer
spanning some 50 years. His wide-ranging interests
included floristics, lichens, ecophysiology, plant geogra-
phy, Quaternary history and climatology. When his
account of the mountain vegetation of Rondane in southern
Norway was published in 1957, it was rapidly recognized
as a classic. Many of his interests are apparent in The
phytogeography of northern Europe, which he wrote in the
last few years of his long life but did not quite complete. A
planned chapter on aquatic plants is missing. The
published version has been assembled by his widow Gro
Gulden, with assistance from John Birks. Inevitably, it
contains imperfections due to the author’s death, but is
presented to the public with the comment that an imperfect
work published is more valuable than a perfect work
unpublished.
Dahl was a champion of the nunatak hypothesis, the
theory that species survived the Pleistocene glaciations in
ice-free refugia, even in northern Europe. It is contrasted
by his editors with the alternative tabula rasa hypothesis,
that the flora of northern Europe is almost entirely
composed of immigrants from unglaciated areas from the
south, west and east of the ice. The theory of ice-free
refugia pervades Dahl’s treatment of endemism. Endemics
remain in their refugia because of ecological rigidity,
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370 Reviews
whereby populations surviving in limited refuges for long
periods ‘become ecologically specialized, show little mor-
phological variation, and are unable to invade new
territories as they become available’.
Evolution cannot fill gaps rapidly. Species are con-
strained by both primary factors (limits given the available
gene resource) and secondary factors (temporary limits
that can be overcome by microevolution). ‘There is no
known instance where it can be convincingly demonstrated
that a new amphimictic vascular plant species has evolved
by purely genetic processes other than alloploidy during
the last 18000 years’.
The book is full of interesting ideas. It is a reminder that
many fashionable notions are not new and that there are
alternatives to current fashion. The climatic requirements
of plants were seen by Dahl not so much as complex
multidimensional realized niches in climate space, but as
limits beyond which species may not transgress. In a
greenhouse world, limits might be more suitable than
realized niches for predicting effects of climate change,
because new climates might lack current analogues.
A major problem in interpreting climatic limits is that
much of the evidence is correlative. Only rarely can good
evidence of causality be established. It requires both a
strong correlation and a physiological mechanism. Dahl
studied the effect of high summer temperature on arctic
and alpine species, noting that both poor competitive
ability and a physiological intolerance of high temperatures
play a part. Another well studied limiting factor is the
requirement of trees for summer warmth. Most phyto-
geographers measure summer warmth by a simple heat
sum, for example, the annual sum of day-degrees with a
base of 0°C or 5°C. Dahl used a far more complicated
heat sum, based on the respiration of a theoretical spruce
tree with an Arrhenius response of Q"!
¯ 2±65 and a lower
temperature threshold of 2±8°C. This ‘respiration sum’
takes no account of the direct effects of solar radiation,
but does allow for diurnal variation in air temperature. It
will probably never be popular; but one is challenged to
ask why not.
Other geographical limits are less well understood.
According to Dahl, the apparent requirement of many
boreal species for a cold winter still lacks an obvious
physiological mechanism, but is probably related in some
way to the stability of the winter climate. The seeds of
Picea abies need snow cover to survive the winter. Many
other boreal plants are likely to be exhausted in an oceanic
climate by spring frosts or futile winter growth. This
limitation, however, is, at least partly, a secondary factor,
which can be overcome by the evolution of local races.
Plants of Kobresia simpliuscula from the relictual popu-
lation in England can be grown out of doors in Copenhagen
while those originating from Greenland require an arctic
glasshouse.
Dahl used four major limiting factors, winter cold,
maximum summer temperature, respiration sum and
summer drought, to define floristic elements in northern
Europe. While his definitions are interesting, they retain
some curious inconsistencies. It is puzzling to find a
‘British-Mediterranean’ sub-element of the Atlantic el-
ement but no Mediterranean–Atlantic component of the
Norwegian flora. The distribution map of the lichen
Degelia atlantica, extending from Norway to Tunisia and
southern Greece, shows just such a species.
Although phytogeography is a relatively slow-moving
subject, the book is somewhat dated, employing methods
from about 30 years ago. An account of the energy balance
of a wet surface is written mainly in units of calories per
square centimetre per minute – inconvenient for a modern
reader, who would prefer watts per square metre. Many of
the data used to estimate limiting climatic factors were
captured by manual methods, rather than from electronic
databases. Appendix 2, stretching to 73 pages, is dull. It
lists distributional data and limiting climatic factors for the
vascular plants of northern Europe. For many whole
genera, e.g. Koeleria and Alopecurus, the only information
given is whether the species are indigenous to the British
Isles or Fennoscandia or both.
Because of its high price, idiosyncrasies and inconsis-
tencies, The phytogeography of northern Europe cannot be
recommended as a standard text for undergraduate
courses. Brimming with original ideas and stimulating
theories, it is a valuable source for research workers, a
challenge for bright students and a fitting memorial to a
lifetime’s work. Those who brought the book to fruition
have done phytogeography a good service.
M H
Opportunities for biological nitrogen fixation in rice
and other non-legumes. Ed. by J. K. LADHA, F. J.
DE BRUIJN and M. A. MALIK. 26±5¬19±5 cm.
Pp. vii216 with numerous test-figures and
tables. Dordrecht, The Netherlands: Kluwer
Academic Publishers, 1997. Price h}b: £85.00,
ISBN 0 7923 414 2; p}b: ISBN 0 7923 4748 X.
This volume contains 20 chapters, varying in length from
four to 18 pages, based on papers given at a workshop held
in conjunction with the 7th International Symposium on
Nitrogen Fixation with Non-Legumes, in October 1996 in
Faisalabad, Pakistan. All contributors were invited and
given remits which had been agreed at a previous meeting
held at IRRI in the Philippines. They thus form a more
coherent whole than the proceedings of many conferences.
All have been published in a special volume of Plant and
Soil and subjected to a refereeing process.
The first chapter sets the scene and outlines four areas
identified in the first workshop as worthy of exploration.
These are: non-nodular associations, such as that between
sugar cane and Acetobacter diazotrophicus ; nodular asso-
ciations, such as the attempts to induce nodule like
structures on rice; transferring nif genes directly into
plants; increasing our understanding of N-use efficiency in
rice, and its relation with carbon dioxide fixation. Some of
the chapters include new information, others are es-
sentially reviews, and occasionally some new ideas emerge.
Overall, the amount of information not available elsewhere
is limited, but it is very useful to have it all included in one
volume.
The bulk of the chapters (14) are entirely or mainly on
the first two topics. Few specifically address rice, rather
they point to relevant aspects of other associations, most
notably that between Azoarcus and Kallar grass. Of those
that do address rice, Barraquio et al. report isolation inter
alia of the potential nitrogen fixing organism Herba-
spirillum seropedicae, but these workers were unable to find
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Reviews 371
evidence of nitrogen fixation. This particularly organism is
an interesting one as it can also be pathogenic, with the
borderline between pathogenesis and beneficial association
being very thin (Olivares et al., 1997). The subsequent
chapter (with the same title) by Stoltzfus et al. discusses
both natural isolates and experiments with artificial
inoculation. Again the results to date are not clear-cut.
Several papers report on studies of the mode of entry of
associative bacteria into plants, including rice. This subject
is very controversial, and at the most recent (1997)
International Nitrogen Fixing Conference, in Paris,
resulted in some extremely acrimonious debate. The
evidence presented in this volume is consistent with the
entry of bacteria via wounds where lateral roots emerge, a
route which rhizobia adopt in some legumes such as
groundnut. Some plant anatomists, most notably from
McCully’s group in Canada have claimed that this is not
possible, at least in healthy monocots. It is a pity that, in
the chapter of which she is an author, this topic was not
addressed. Otherwise, this particular chapter (Rolfe et al.)
gives a good account of the effects of bacteria on root
morphogenesis. They use the term ‘modified root out-
growths’, rather than ‘para-’ or ‘pseudo’ nodules to
describe structures induced by bacteria. Based on the
legume system, Hirsch discusses the role of phyto-
hormones in nodule morphogenesis. Since one of the ways
in which bacteria affect root growth is by production of
auxins and other plant growth promoters, this paper is
timely. Promotion of root growth per se is likely to lead to
better N uptake from soil sources, making unambiguous
determination of nitrogen fixation essential. Kennedy et al.
have developed an elegant method of demonstrating this,
by tagging the nifH gene in Azospirillum brasilense with
lacZ and following the invasion of wheat roots with this
construct. This has the added benefit of demonstrating
that low oxygen conditions are present, since nifH requires
low pO#
for its induction.
Apart from the method of entry by bacteria, there are
two other questions which currently bedevil workers in the
general area of nitrogen fixation associated with grasses.
The first of these is ‘can sufficient bacteria be housed in the
plant without causing damage?’. Whilst alluded to in a
number of chapters, this problem has still not been
rigorously tackled. The second is ‘how do the plants
obtain nitrogen fixed by the bacteria, presumably for their
own use?’. In the advanced legume symbiosis, ammonium
is transferred directly to the host for assimilation. Do
associative bacteria have to die before their fixed nitrogen
is released to the plant? This does not necessarily appear to
be the case, and two of the chapters in this volume report
work on ammonia excreting mutants of bacteria.
One of the aspects of the signalling systems in the
legume–rhizobial system which has received much at-
tention recently is the role of lipo-oligosaccharides. These
substances form part of an interesting discussion by Stacey
and Shibuya, whose main thrust is chitin recognition
systems. The authors argue that, while both rice and
legumes have sites with chitin-binding proteins, legumes
may have a second, more specific site, necessary for nodule
induction. This could be one of many fundamental
differences between legumes and monocots which chal-
lenge those trying to induce nodule-like structures on the
latter.
The final chapter, by Shantaram and Mattoo, attempts
(with a considerable degree of success) to put the previous
ones in perspective and to point the way ahead for future
work. They correctly point out that, in spite of much
effort, there has been very little recent success in improving
nitrogen fixation by legumes (e.g. by using genetically
modified rhizobia). They argue that a research programme
devoted to improving uptake and utilization of combined
N by plants in general has much to commend it.
I have not attempted to cover every single chapter in this
book. The most notable omission is the chapter of Dixon
et al. on the prospects and problems of introducing nif into
plants. I recommend readers to follow this well argued
account.
Taken overall, this volume contains a well balanced
assessment of the state-of-play on the possibilities of
exploiting nitrogen fixation in association with rice.
However, I can see no justification in Kluwer, yet again,
selling a hardback copy, at a high price, of material that has
already been published in their own journal, Plant and
Soil. Apart from the Preface, nothing is added. It would
have been relatively simple, with modern technology, to
have included an index and enhanced the value of a
separate volume.
Olivares FL, James EK, Baldani JI, Do$ bereiner J. 1997.Infection of mottled stripe disease-susceptible and resistant
sugar cane varieties by the endophytic diazotroph Herbaspiril-
lum. New Phytologist 135 : 723–737.
J. I. S