Stratification of tropical forests as seen in leaf structure

527 Pages·1984·23.843 MB·English

by  Ingrid Roth (auth.)

Stratification of tropical forests as seen in
leaf structure
Tasks for vegetation science 6
Series Editor
HELMUT LIETH
University oj OsnabrUck, F.R.G.
INGRID ROTH
Stratification of tropical forests
as seen in leaf structure
1984 DR W. JUNK PUBLISHERS
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Library of Congress Cataloging in Publication Data
Roth, Ingrid.
Stratification of tropical forests as seen in
leaf structure.
(Tasks for vegetation science ; 6)
Bibliography: p.
Includes index.
1. Leaves--Anatomy. 2. Rain forests.
I. Title. II. Series.
QK649.R83 198;" 581.4' 97 82-14055
ISBN-13: 978-94-009-6571-3 c-ISBN-13: 978-94-009-6569-0
DOl: 10.1007/978-94-009-6569-0
Cover design: Max Velthuijs
Copyright © 1984 by Dr W. Junk Publishers, The Hague, The Netherlands
Softcover reprint o/the hardcover 1st edition 1984
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or
transmitted in any form or by any means, mechanical, photocopying, recording, or otherwise,
without the prior written permission of Ihe publisher, Dr W. Junk Publishers, P. O. Box 13713,
2501 ES The Hague, The Netherlands.
PREFACE
The studies presented in this volume are meant to The reason why we know relatively little about
close some gaps in our knowledge of leaf anatomy inner leaf structure of trees from tropical humid
of trees in tropical humid forests. Although xero forests is that the leaf anatomy of only a few species
morphy of the foliage in tropical humid forests has or genera or - at the most - of an entire family has
been much discussed, the statements have generally been studied in detail up to the present. Most of
been based on sporadic anatomical studies of parti these studies are, therefore, of taxonomic interest.
cular species or genera, a complete area of the size They cannot be included in this study because they
of 155.5 ha has certainly never been considered. do not supply the same information or amount of
The present studies analyse an entire inventory of a data presented here. Anatomical studies are very
given region in which the number of species and the time consuiming because the material first has to be
number of individuals is very well known. This fact prepared and cut before observation can begin. In
allows the elaboration of many ecological aspects, vestigation of about 50 characteristics in 230 species
which was the main intention of the author. The consequently requires much work, which may only
species, genera, and families studied here represent fully be appreciated by those who work themselves
the most important ones considering their distribu with material of the same size.
tion in the humid forest of Venezualan Guiana, on The importance of these studies, therefore, not
the one hand, and the size of the trees, on the other, only lies in the quantity of species studied, but also
so that trees with less than 20 cm diameter at breast in the possibilities of comparing leaf structure in
height (DBH) are usually ignored. the different stories or levels of the forest. From
The unique opportunity to have an almost com there we may assume that leaf structure is adapted
plete collection of samples of a well-known area to the microclimate in the forest, whether herba
where even the height of the trees is known, con ceous species or trees of different height during
siderably facilitated a comparison of leaves coming their development are considered.
from different levels of the forest. In earlier Consequently, these studies may be judged by the
studies, the author has already noted that leaf con uniqueness of this collection which allows the con
sistency and structure in the undergrowth differs sideration of certain ecological viewpoints such as
greatly from that of leaves of the upper canopy. the well-known characteristic of xeromorphy in
This observation could be extended and more or leaves.
less generalized in the present investigation. A
further advantage of this collection is that not only
leaves of adult trees, but also those of juvenile trees Miinstertal, July 1983 Ingrid Roth
of different height categories were available. Only
those who repeatedly collect material in tropical
forests are able to appreciate the efforts of Dr B.
Rollet, to whom the author owes this collection.
CONTENTS
PREFACE v
1. INTRODUCTION
2. SOURCE OF THE MATERIAL AND SAMPLE COLLECTION 3
3. PREPARATION OF SLIDES 5
4. GENERAL OBSERVATIONS 6
Leaf morphology
Drip tip -Pulvini -Leaf size -Leaf shape -Juvenile and adult leaf forms -Venation
Innter leaf structure
Xero-, meso-, hygromorphy, and sun-, medium-, shade-leaf, alteruatively -Leaf consistency -Structural peculiarities
Structure in reletion to function
5. TABLES OF THE FAMILIES STUDIED INDICATING STRUCTURAL CHARACTERISTICS 19
Annonaceae -Capparidaceae -Violaceae -Flacourtiaceae -Vochysiaceae -Guttiferae -Quiinaceae -Sterculiaceae -
Tiliaceae -Elaeocarpaceae -Humiriaceae -Malpighiaceae -Rutaceae -Simaroubaceae -Ochnaceae -Burseraceae -
Meliaceae -Dichapetalaceae -Olacaceae -Opiliaceae -Celastraceae -Sapindaceae -Sabiaceae -Anacardiaceae -
Mimosaceae -Caesalpiniaceae -Papilionaceae -Rosaceae -Combretaceae -Myrtaceae -Lecythidaceae -Melastomaceae -
Araliaceae -Rubiaceae -Sapotaceae -Ebenaceae -Apocynaceae -Boraginaceae -Solanaceae -Bignoniaceae -
Verbenaceae -
Nyctaginaceae -Polygonaceae -Myristicaceae -Lauraceae -Euphorbiaceae -Moraceae -Lacistemaceae -Unidentified
(Nigua)
6. DESCRIPTION OF THE FAMILIES STUDIED CONCERNING LEAF STRUCTURE 341
Annonaceae -Capparidaceae -Violaceae -Flacourtiaceae -Vochysiaceae -Guttiferae -Sterculiaceae -Tiliaceae
Elaeocarpaceae -Malpighiaceae -Rutaceae -Simaroubaceae -Ochnaceae -Burseraceae -Meliaceae -Dichapetalaceae -
Opiliaceae -Celastraceae -Sapindaceae -Sabiaceae -Anacardiaceae -Mimosaceae -Caesalpiniaceae -Papilionaceae -
Rosaceae -Combretaceae -Myrtaceae -Lecythidaceae -Melastomaceae -Rubiaceae -Sapotaceae -Ebenaceae -
Apocynaceae -Boraginaceae -Solanaceae -Bignoniaceae -Verbenaceae -Nyctaginaceae -Polygonaceae -Myristicaceae -
Lauraceae -Euphorbiaceae -Nloraceae -Lacistemaceae
7. DEVELOPMENTAL ASPECTS 416
Development of crypts and "cornets" around the stomata -Formation of cork warts -Origin of the oblique position of
palisade cells
VIII
8. ECOLOGICAL ASPECTS 419
Xeromorphy, succulence, and hygromorphy
Criteria of xeromorphy -Criteria of hygromorphy
Sun and shade leaf type
Criteria of the sun leaf type -Criteria of the shade leaf type
The significance of the different structural features and their ecological importance
Blade thickness -Number of layers of the upper epidermis -Waxy layers -Cuticle -Thickness of the outer wall of the
upper epidermis -Cell size of the upper epidermis, as seen in transection -Cen size and form of the upper and lower
epidermis, as seen in surface view -Number of palisade layers -Length of palisade cells -Length/width index of the
palisade cells -Index palisade parenchyma/spongy parenchyma -Stomate density -Stomata length -Level of stoma
formation -Hair density -Papillas, wall excrescences and surface sculpturing -Density of vascular bundles -Secretory
cells -Secretory canals or cavities -Upper and lower hypodermis -Sclereids -Glands -Slimy walls -Stomata in the
upper epidermis -Upper epidermis as a water reservoir -Xero-, meso-, hygromorphic leaves and sun and shade leaf
type
The progressive transformation of the hygromorphic shade leaf into the xeromorphic sun leaf
Blade size and shape -Blade thickness -Width of outer wall of the upper epidermis -Upper epidermis as a water
storing tissue -Number of epidermis layers -Formation of a (upper or lower) hypodermis -Number of palisade layers
Length of paisade cells -Length/width index of the palisade cells -Chloroplasts -Proportions between palisade and
spongy parenchyma -Stomata size and density -Level of stoma formation -Development of "cornets" and crypts -
Hair density -Papillas, wall excrescences and surface sculpturing -Density of vascular bundles -Xero-, meso-,
hygromorphic leaves -Sun and shade leaf type -The increasing width of the leathery leaf -Comparison of juvenile and
adult leaves
Comparison with the cloud forest -The leathery leaf -Environmental conditions
Soil -Water supply -Illumination -Temperature
9. TAXONOMICAL ASPECTS 453
10. PHYLOGENETIC ASPECTS 456
11. DISCUSSION OF THE MOST IMPORTANT RESULTS 458
12. FIGURES TO THE TEXT 465
13. BIBLIOGRAPHY 509
14. INDEX OF SCIENTIFIC PLANT NAMES 515
15. INDEX OF VERNACULAR PLANT NAMES 519
16. GENERAL INDEX 522
CHAPTER 1
INTRODUCTION
It is generally agreed that tropical humid forests However, the decision whether an organ is
supply a relatively high percentage of coriaceous scleromorphic or not should be left to the plant
foliage (Richards 1952). However, the problem in anatomists. As cited above, Roth gave a series of
itself is still unsolved. We do not know which examples in which leathery texture is caused by very
structural peculiarities render the leaf texture different tissue peculiarities. In many cases, in
leathery nor do we know which factors are respon creased wall thickness of epidermis or hypodermis
sible for the development of this consistency. cells, or development of several epidermal or
The suggestion that a thick cuticle makes leaves hypodermal layers or an increase of the layers of
of tropical humid forests (e.g. rain forests) other tissues (such as the palisade parenchyma,
coriaceous (Walter 1968) was able to be disproved especially when the walls become thickened), or
by Roth (1977a). Other authors speak of sclero stronger development of the vascular tissue, have
morphy when referring to leathery foliage of all been mentioned as possibilities which may
tropical humid forests. This definition implies that induce a coriaceous texture (Roth 1977a). There is
sclerenchyma is present in larger amounts either in no specific type of leathery leaf in the humid
the form of sclereids or in the form of fibers. How tropical forest which is characterized by a very
ever, as was able to be shown by Roth (1977a), specific anatomical structure. On the contrary, a
many or even the majority of these so-called great variety of types is typically present in an
'scleromorphic' leaves develop very little or no environment which may be considered optimal.
sclerenchyma at all. The expression 'scleromor This is explained by the presence of a large variety
phic' is consequently misleading in these cases. of species all of which grow more or less in the same
On the other hand, certain authors believe that soil and develop under favorable environmental
the coriaceous texture is caused by a deficit in conditions. Roth emphasizes in this connection that
certain nutrients from which the leaves suffer, N in tropical humid forests the plants can afford to
and P in particular, and, therefore, speak of display such a luxury of different structures, while
'peinomorphy' in leaves. Soils of tropical humid in other less favorable environments only those
forests are commonly regarded as relatively poor, plants can survive which develop the necessary
especially in P, and a deficit in P should cause the co adaptations.
riaceous texture of the leaves, according to certain Another observation in tropical humid forests is
authors. Montfort first explained the xeromorphic that the tall trees mainly have coriaceous foliage,
leaf structure of plants growing in raised bogs by an while herbaceous plants usually develop more
N deficit. Since then, several authors have observed delicate leaves. In this connection, Bews (1927)
the development of a coriaceous texture by a deficit explains the xeromorphic type of leaf structure in
of certain elements. Herrera et al. (1978) insist very tropical rain forests by the low specific capacity of
strongly that 'sclerophylly' of tropical humid forest water conduction in the wood of the trees concern
trees is caused by a deficit of P. ed. More recent studies (Larcher 1973) showed that
2
the specific capacity of water conduction IS very tropical humid forest in order to come to definite
low in European evergreen trees, approaching the results concerning leaf structure and, supported by
values of conifers. this fundamental knowledge, to search for a
In the view of this whole problem, which has plausible explanation of the phenomenon of
been solved neither from the physiological nor leathery leaf consistency and other structural
from the structural point of view, it seems advanta peculiarities in leaves found in tropical humid
geous to use the collection of leaves of an entire forests.
CHAPTER 2
SOURCE OF THE MATERIAL AND SAMPLE COLLECTION
The material investigated mainly comes from the dated soils or permanently inundated river banks,
humid tropical forest in Venezuelan Guiana where rocky sites, etc., which may well be recognized by
an inventory was initiated by the Ministry of 'Agri their floristic composition. In its western part, the
cultura y Cria' (MAC) of Venezuela together with forest is in contact with a belt of semideciduous and
the Food and Agriculture Organization (F AO) and deciduous forests, bordering in their turn, sa
the UNO. In this inventory all arboreous species of vannas. Although the tropical humid forest is
this area were statistically covered. The total area called 'evergreen', Rollet (1964) was able to count
studied for the inventory amounted to about 67 km about 60 species which drop their leaves, mainly in
in length and approximately 25 m in width, April. However, the defoliation is somewhat
covering about 155.5 ha in total. A clearing of the ephemeral and irregular, even considering one and
above-mentioned length and width was cut through the same species so that the forest as a whole
the forest to collect trees, shrubs, and partly also preserves its evergreen aspect. Flowering and
lianas. In total, 67,777 individual trees (and shrubs) fructification are not very clearly limited to certain
with a diameter of not less than 10 cm at breast periods of the year, but a certain proportion of the
height were included. species does flower and fruit with more intensity
The tropical humid forest from which leaf four times a year, in February-June-August-De
samples were collected corresponds to a dense ever cember and in February-May-August-December,
green rain forest which Beard would call 'seasonal' respectively. For more details on the humid tropical
to indicate the incidence of distinct dry seasons. forest in the State of Bolivar, Venezuela, and its
Geographically it is situated on the shield of floristic composition, see Rollet (1964, 1969a, b),
Venezuelan Guiana at the so-called massif of from which publications the above data are taken.
Imataca (south of the Orinoco river and east of the Most of the species were identified by Dr Julian
junction with the Caron! river). This extreme Steyermark, Instituto Botanico, Caracas. Those
Northern part of the Guianan shield has an undu samples which could not be identified in Caracas
lated ground relief which fluctuates between 150 m were sent to specialists in the USA, England,
and 550 m in altitude. The shield of Guiana is com France, the Netherlands, Belgium, Sweden, Co
posed of rocks of the Precambrian Era, essentially lombia, and Brazil. Some of the samples, however,
of granites and gneisses. The soil corresponds to a are still in the 'process' of identification, although
red latosol. The annual precipitation is estimated at the inventory was finished approximately in 1967.
about 2000 mm or more, with a dry se·ason of Most difficulties in the identification arose among
varying length between January and April. Special the Burseraceae (the genus Protium), the Sapota
floristic studies were carried out around camps 'Rio ceae (Pouteria), Myrtaceae, and Rosaceae (Lica
Grande', 'El Paraiso', and 'El Dorado' . nia). In spite of all the efforts of taxonomists, we
In the interior of the forest, some special edaphic still expect some misinterpretations and uniden
formations are included such as periodically inun- tified species.