Download Field Methods in Landscape Analysis Geography 486

3.1
Field Methods in Landscape Analysis
Geography 486
Field Excursion #2:
Plant Identification and Sampling in the Chaparral
Location: Santa Monica Mountains
Geography 486/586
Laris
Splansky and
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EVALUATION
Field Session:_____Chaparral .
1.
Something I liked about this session was:
2.
Something I learned in this session was:
3.
Something I did not like about this session was:
4.
Comments on how to improve the session:
3.3
READING FOR WEEK 2: CHAPARRAL VEGETATION ASSOCIATION
BIOGEOGRAPHY
Biogeography is the study of past and present geographic distributions of plants and animals and other organisms
(MacDonald, 2003). More than most sciences, biogeography helps us to understand and appreciate the environment that
we experience every day. Southern California is a hotspot of biodiversity and many of the species found in our region are
found nowhere else. Yet, many of these species are threatened by development and other human actions. When cycling
or driving along the coast, in the foothills or to the mountains in southern California, many of the plants you see are exotic
species that were introduced by humans.
Biogeographers ask two kinds of questions related to the processes of species invasion. First, they ask questions from
the perspective of the invasive species such as: How did exotics get here? Why were (are) they able to outcompete the
native species? What kinds of human disturbances facilitate their take-over. Which micro-habitats do exotics prefer?
Second, they ask questions from the perspective of the native species. These questions often deal with issues of
restoration of degraded areas that have been colonized by exotics such as: Which native species were found where in the
landscape (what micro-habitats are preferable to particular native species)? What natural disturbance regime did the
native species evolve with and can we restore it? (How) Did the land use practices of Native Americans, such as burning,
hunting, and gathering modify the species composition in the landscape prior to European arrival? What are the best
active and passive approaches for restoring various native species habitats?
In studying the present, past and future distributions of life, biogeographers have two basic tasks: description and
explanation. Description of the vegetation in the landscape involves careful documentation of the numerous species at a
site. This will involve species identification and sampling techniques, and careful documentation of the geography of the
site such as location, slope, aspect, soil, and other pertinent factors. Scientific explanation usually requires hypothesis
testing and involves collecting and analyzing data. It is critical that the methods used to gather and analyze the data are
well stated in the report. Several field assignments deal with basic issues and concepts in a variety of different plant
communities and biomes including: coastal sage scrub, chaparral, desert and mountain.
FLORA (PLANTS )
The plant kingdom (Plantae) is of particular interest to geographers as plants are at the base of the food chain for most
animals including humans, are major components of ecosystems, reflect local and regional environmental conditions, are
natural resources that contribute materials to the economy, and are aesthetically pleasing to humans. Biogeographers
know that the physical forms of individual plants and of their assemblages vary in some systematic way with latitude,
elevation and continental position and participate in the research effort to explain why and where these species and
assemblages have become so well adapted as to become dominants in local and/or regional environments. Spatial
inequalities thus exist with respect to the spatial distribution of plant types and species.
Assemblages of dominant species in a local or regional area can be considered as a vegetation association or the core
elements of a particular ecosystem to be distinguished from other vegetation associations or ecosystems and may form an
identifiable unit for geographic study.
Plant Classification
Taxonomy is the science of grouping organisms according to their presumed natural relationships. All living things
are classified as belonging to one of three kingdoms, Monera (Bacterium), Animalia (animals) and Plantae (plants). The
common system of classification of organisms that is used today is called binomial nomenclature (often called the
Linnaen system) and is based on the work of the Swedish naturalist, Carolus Linnaeus. The Linnaen system is arranged
in a hierarchical format and contains seven levels of classification as identified in the example below which classifies the
bigleaf maple tree, common in coastal valleys and adjacent slopes in California.
3.4
Kingdom = Plantae
Division = Anthophyta (vascular, seed producing, flowering plants)
There are nine divisions of the plant kingdom .
Class = Dicotyledonae (Dicot)
Order = Sapindales (soapberry plants)
Family = Aceraceae (maple like family)
Genus = Acer (contains 150 species of maple trees and the box elder)
Species (Specific Epithet) = macrophyllum (bigleaf maple)
Rather than list all seven categories when naming an organism, Linnaeus chose to use only the genus and species
names. Linnaeus’ binomial nomenclature (“two names”) system continues to be in standard use for identifying the
scientific name of organisms thus Acer macrophyllum would be the correct taxonomic label for the bigleaf maple tree.
Taxonomists divide land plants into two groups based on whether or not they have vascular tissue. Members of the
nine divisions of vascular plants have water-conducting tissues and most have true roots, stems and leaves. Vascular
plants are divided into two groups, the seedless plants (including ferns) and the seed plants which are classified into four
divisions of Gymnosperms (non-flowering plants) and one division of Angiosperms (or flowering plants).
Gymnosperms
The Gymnosperms are plants that produce “naked” seeds (not carried in fruit) The four divisions of Gynosperms are
Cycadophyta, the Cycads; Ginkgophyta, the Ginkgos; Gnetophyta, the Gnetophytes; and the Coniferophyta, the Conifers.
The conifers, which are Gymnosperms of the Division, Coniferophyta, include pine trees, cedars, junipers, redwoods, firs
hemlocks, yews and spruces. Conifers are woody plants with needle-like or scale-like leaves. Each individual bears both
male and female cones. The small male cones appear in clusters, most of which release clouds of dust-like pollen and
then fall off their branches. After pollination, the complex, woody female cones close up tightly which protects the
developing seeds until they ripen and are subsequently released.
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Figure1: Monocots and Dicots
Angiosperms
Angiosperms (Division Anthophyta) are flowering, fruit bearing, seed plants characterized primarily by the presence
of seeds enclosed in fruits. There are about 275,000 species of the Angiosperm Division and they dominate the plant
world. Angiosperms grow in many forms; some are delicate herbs with showy blossoms such as orchids (an herb is a
non-woody plant); some, such as rosebushes, are woody shrubs; some, such as ivy are vines; oaks, alders and aspens are
flowering plants though the blossoms may not be easily noticed; grasses are also angiosperms with tiny highly modified
flowers.
As vascular, flowering plants, that carry seeds in fruit, angiosperms have been very successful at increasing their
geographic distribution, population and number of species. The fruits protect the seeds and aid in their dispersal. Seeds
increase the chances that a plant will have reproductive success. Inside the rough protective coat of a seed is an embryo
and a food supply. When the conditions are too hot or too cold, or too wet or too dry, the seed remains inactive. When
conditions favor growth, the seed germinates, that is the embryo begins to grow into a young plant called a seedling.
Angiosperms also have highly efficient vascular systems for transporting water and nutrients from roots to leaves and
food to storage organs. Another important factor in the success of angiosperms is that they evolved along with insects.
The fossil record indicates that this co-evolution, or mutual adaptation, of flowering plants and insects began more than 65
million years ago. Many angiosperms can reproduce only when insects carry pollen from one plant to another. The
insects visit the flowers for nourishing nectar and pollen. In doing so they pollinate plants and begin the process of
3.6
fertilization. Fertilization initiates the development of fruits and seeds. A seed is a fertilized ovule which was
produced and housed in an ovary. A mature ovary is called a fruit and fruits protect seeds, aid in their dispersal and may
provide a source of energy for the early growth of the seedling.
The Division Anthopyhta (Angiosprms) is divided into two classes, Monocotyledonae (Monocots) and Dicotyledonae
(Dicots) (see figure 1). One feature that distinguishes these two groups is the number of cotyledons, or seed leaves.
Monocots have a single cotyledon in their embryos, while dicots have two. Fortunately, other differences occur between
the two major groups, besides their seed types, so that dissecting a seed is not necessary to determine if a plant is a
monocot or a dicot. Mature monocot leaves have parallel venation (the arrangement of veins in the leaves), while dicot
leaves have net venation. Flowers of monocots have three or six petals, but never four or five. In Comparison most
dicots have flowers with four, five or more petals but rarely six. Dicots that have flowers with six petals have leaves that
are not parallel veined. There are approximately 90,000 monocot species including onions, orchids, corn, wheat, oats,
rye, rice, bamboo, and coconut trees. Dicots include the majority of the world’s flowering plants, about 185,000 species,
which include cactuses and most flowering forest trees.
Plant Structure and Function
The body of most vascular plants is divided into three principal organs: leaves, stem and root system. A stem and its
leaves, taken together, is called a shoot and the points where leaves attach to the stem are called nodes. Broadly speaking,
the leaves are the chief organs of photosynthesis whereas the roots anchor the plant in place and absorb water and mineral
nutrient elements from the soil. Roots also may store food made during photosynthesis. The stem holds and displays the
leaves to the sun, maximizing the photosynthetic yield, and provides transport connections between the roots and leaves.
The vascular tissue system of the stem is composed of xylem and phloem; xylem conducts water and minerals and forms
the wood of trees providing strength. Phloem transports or conducts food materials from one part of the plant to another.
Roots
Water and minerals usually enter the plant through the root system. There are two principal types of root systems, a
taproot system and a fibrous root system. Many dicots have a taproot system, in which a single, large, deep-growing root
is accompanied by less prominent secondary roots. The taproot itself may function as a food-storing organ, as in carrots.
In contrast, monocots and some dicots have a fibrous root system, which is composed of numerous thin roots. Fibrous
root systems often have an extensive surface area for the absorption of water and minerals. A fibrous root system holds
soil very well, giving grasses with such systems a protective role on slopes where runoff from rain could cause erosion.
Stems
Stems, unlike most roots, may be green and capable of photosynthesis. A stem bears leaves at its nodes, and where
each leaf meets the stem there is a lateral bud, which develops into a branch if it becomes active. A branch is also a stem.
Stems bear buds, which are embryonic shoots, of various types. At the tip of each stem or branch is an apical bud which
contains a shoot apical meristem which produces the cells for the growth and development of the stem. Also contained
within the apical bud is the leaf primordia, which will expand into mature leaves. The stem, at a point or points varying
from species to species, may also produce flowers.
Stems are adapted to different environments and have three functions; support, transport and storage. Water and
mineral nutrients are delivered from the roots to the leaves via the stem’s vascular system. Plant stems are also adapted
for food storage in some species. Succulents are plants that have particularly fleshy stems that retain water and nutrients
in areas where water is often unavailable.
Meristems, Growth and Life Cycles
Plants possess meristems, growing regions where cells divide and the plant thus grows. Plants grow in length by and
from apical meristems located at the tips of stems and roots. Stems grow in length only at their tips. Plants also have
lateral meristems which grow and increase their circumference. One such meristem is the vascular cambium which
produces additional vascular tissues. Adaptations occur in meristems that determine growth patterns and the life cycle of
plants.
3.7
Life cycles, including growth patterns of plants, fall into three categories: annual, biennial and perennial. Annual
plants live less than a year, are adapted for rapid growth and reproduction and include many food crops. Annuals are
classified as herbaceous plants as they do not have a vascular cambium and their tissues remain non-woody. Biennials,
such as carrots and cabbages, grow for all or part of one year and live on into a second year during which they flower, set
seed and die. They too are herbaceous plants. Trees and woody shrubs are perennials which means they are adapted for
growth year after year. They develop much secondary xylem and are called woody plants as opposed to herbaceous.
Leaves
Normally borne at the nodes of a stem, most leaves are thin, flat, absorb light energy and take in carbon dioxide from
the environment. Cells in leaves, using light energy, are responsible for most of the photosynthesis and metabolic
reactions that make nitrogen available to the plant for synthesis of proteins and nucleic acids and produce food for the
plant, and release oxygen gas. Photosynthesis employs solar energy, carbon dioxide and water to make sugars that can
then be used as an energy source for growth or be transported to roots or fruits and stored until needed. A less obvious
but often crucial function of leaves is to shade neighboring plants. Plants, like all organisms, compete and if a plant can
reduce the photosynthetic capability of its neighbors by intercepting sunlight, it can obtain a greater share of the available
water and mineral nutrients.
The temperature of a leaf increases when it absorbs light. Transpiration cools leaves while pulling water and
dissolved minerals from roots through stems. In some plants, 98% of the water that is absorbed by the roots is lost
through transpiration.
3.8
THE CONCEPT OF ECOLOGICAL SUCCESSION TO CLIMAX
The concept of ecological succession is nested within the discipline of ecology and biogeography. The word ecology
was coined in 1869 by Ernst Haeckle by joining "oikos" (meaning "dwelling place") and "logos" (meaning "study of”):
The study of ecology means examining "how plants and animals and their non-living (physical) environment interact and
influence each other.” Particular concern is addressed to the exchanges of energy and matter which influence and control
the population dynamics of a particular species.
Traditionally ecology has been concerned with finding equilibrium or stability points in the ecological systems under
study (at any scale be it global such as vegetation after a glacial retreat or at a smaller scale such as the dynamics of plants
and animals after a chaparral or prairie fire). Increasingly ecologists and biogeographers recognize the importance of
disturbance, and change in ecosystem dynamics. Scientists now believe that many ecosystems are unstable. Systems
may be in disequilibrium, meaning that they plant and animal communities are subject to constant flux based on both
external forces (such as climate fluctuations) and internal perturbations due to swings in population of various species in
the community. Or, they may have multiple steady states (or multiple equilibriums); depending on a particular
disturbance regime, an ecosystem may establish a particular steady state and remain in that state until a natural or humancaused disturbance causes the system to shift to a new state.
The changes in ecological and biogeographical thinking during the past 20 years or so have forced scientists to
reconsider many of the theories and underlying assumptions of classical ecological theory that developed early in the 20th
century. In addition to the shift in focus from equilibrium, stability, and climax formations to disequilibrium, disturbance,
multiple states, and even chaos, ecologists and biogeographers have focused on the heterogeneity in environments rather
than their homogeneity. Landscapes are increasingly recognized as heterogenous patch-works or patch-mosaics where
subtle, yet important, variations in soil conditions and topography interact with a disturbance regime to create a fine
mixture of different vegetation patches. An important theoretical advancement was made by landscape ecologists who
demonstrated that the mosaic pattern of the vegetation patches effect ecosystem processes. Biogegraphers, who have long
explored the underlying causes of vegetation patterns, now also seek to understand how the patterns impact ecosystem
structure and function. The shifts in thinking during the past couple of decades leave biogeographers with many
competing theories and many unanswered questions.
Ecosystems
Ecosystem is a term that was introduced in the 1930s and became popular in the 1960s. An ecosystem is a
functioning (interactive and dynamic) assemblage of the biological community (plants and animals), soils, water, humans,
meteorological factors and time, of whatever size or scale. Ecosystems are scale free; they range in size from a drop of
water to a pond, to a lake, to a river, to a tidal zone; from a tree limb, to the crown of a tree, to a grove of trees, to a local
woodland or forest; from a group of hills covered in chaparral, to a mountain slope or desert valley, from a back yard or
city block, to large regions even of continental size such as the taiga or boreal forests or prairies of Eurasia or North
America.
Succession and Climax
An understanding of the ecology of natural ecosystems has for decades rested on the notions of succession and
climax. Successions are of two types; 1) allogenic and, 2) autogenic
Allogenic successions are those driven by external or chemical events (disturbances) such as sea level changes, a
volcanic eruption or a glacial advance or retreat. Humans can be and are sources of allogenic succession as they extirpate
fauna, introduce exotic fauna, introduce exotic flora, build dams and reservoirs, start fires, fell forests, pave over surfaces
and plow land.
Autogenic successions occur where the biota (biological community in an area) themselves create the conditions for
environmental change. Different species in an ecosystem might displace others and flourish more fully as a result of such
changes as alterations in light reception by additional or diminished shading, root chemicals released into soil, increase or
decrease in the amount of available moisture required by a specific species, a changed food resource base for selected
animal species, animal species involvement in plant seed distribution, increases in the population of a species that change
the plant demand for selected soil nutrients, or changing micro habitats that in turn alter humidity or temperature
conditions. Humans can be and are sources of autogenic succession as they selectively add or remove plant or animal
3.9
species to or from an ecosystem, divert water away from an ecosystem, modify temperature or precipitation conditions
in an area or dump toxic chemicals into the ecosystem. In the chaparral ecosystem, fires are a common agent of change
that initiates the ecological succession process or “sere.”
Sere, Seral Stages and Climax
Environmental change processes create the "Sere" through the various seral stages that follow an allogenic event or a
human induced change to an existing ecosystem. Seral stages are the various recognizable phases of succession that
characterize the changing ecosystem as the dynamics and component living organisms (plants and animals) evolve toward
a "climax" stage (stability or equilibrium). In classic ecology, Clement argued that each sere facilitates the transition to
the next sere through miroscale changes to various factors such as soil and shade canopy. The "sere" is the complete
series of seral phases in an ecological succession and according to Clement, each successive stage is more stable than the
preceding stages. Stability refers to the efficiency with which materials and energy are used and consumed by the
organisms in the ecosystem or biome. A biome is the largest terrestrial ecosystem convenient to recognize.
The climax stage is the final seral phase in the sere. The floral and faunal assemblage is in balance under the
influence of all environmental conditions. According to Clement, the climax stage is characterized by equilibrium or a
"steady state". The species composition is diverse, usually with more diversity than in earlier seral stages. The biomass
(amount of living material per unit area) is the greatest in volume or weight that ecological and geological evolution
could produce under the climatic circumstances. The quantity of biomass is limited by temperature, day length (sunlight)
and water availability. This condition is the endpoint of succession; the climax community has replaced earlier
assemblages and represents the "mature" ecosystem.
3.10
THE CHAPARRAL VEGETATION ASSOCIATION
Most biogeographers and ecologists recognize that all the world’s natural land vegetation falls into four major
structural subdivisions or biochores; forest, savanna, grassland and desert. The forest biochore is subdivided into seven
classes including the class known as Evergreen Hardwood Forest or Sclerophyll Forest. The term sclerophyll is derived
from the Greek words sklero, meaning hard, and phyllo, meaning leaf. Sclerophyll thus refers to plants exhibiting
sclerophylly (the normal development of much sclerenchyma in the leaves of certain plants resulting in thickened
hardened foliage). Sclerenchyma refers to the supporting or protective tissue composed of thickened and hardened cells
from which the protoplasm has usually disappeared.
The sclerophyll forest consists of low trees with small hard, leathery leaves. Typically, the trees are low branched and
gnarled with thick bark. The sclerophyll forest includes much woodland, an open forest in which the canopy coverage is
only 25% to 60% and includes extensive areas of scrub, a plant formation type consisting of shrubs having a canopy
coverage of 25%-60%. The distinction between a shrub and small tree is imprecise; most observers label mature woody
plants, under ten to fifteen feet in height, as shrubs. The trees and shrubs are evergreen, their thickened leaves being
retained despite a severe annual drought. There is little stratification in the sclerophyll forest and scrub although there
may be a spring herbaceous layer.
Sclerophyll forest is closely associated with the Mediterranean climate and located on hill and lower mountain slopes.
Although the species compositions are different, the physical forms of sclerophyll forest trees and shrubs are similar in the
five world locations where the Mediterranean climate and topography are similar. In California’s coastal ranges,
including the Santa Ana Mountains, the sclerophyll forest is often a scrub or dwarf forest known as chaparral. Chaparral
varies in species composition with elevation and exposure. The dry summer of the Mediterranean climate is one of great
environmental stress because of the severe drought season that coincides with high air temperatures. A large water deficit
occurs in the summer. Many chaparral species are also high in resin and vegetable oil content creating the potential for
extreme flammability in the dry summer period. Summer fires of great intensity, generating extremely high temperatures,
are not uncommon in the chaparral and indeed, are necessary to facilitate release of seeds from certain chaparral species.
The mild wet winter is highly favorable to rapid plant growth.
Chaparral trees and shrubs have developed a variety of adaptations for surviving the stress of the hot dry summer
season. Plant moisture loss through evaporation is reduced by producing compact, small fleshy leaves, reduced leaf
surface area, leaf coverings of hair-like or whitish materials that may reflect light and hence avoid heat, resinous or waxy
leaf surface textures that will not give up its water content easily and long taproots to reach deeply for ground water.
A few unanswered questions
Given the prevenlence of chaparral vegetation in southen California and its volatility, it is surprising that several basic
questions about the relationships between fire regime, succession and fire hazard remain unanswered. A fire regime can
be defined as the extent, frequency, type and intensity of periodic fires. There are twotypes of fires: ground and canopy.
Mature chaparral burns in a canopy fire meaning that the flames of the fire spread through the canopy of the trees and
shrubs rather than along the ground. These fires tend to be intense—they burn hot—and are swept along by fierce, dry
Santa Anna winds. In the first few years following a fire, however, chaparral is often invaded by annual grasses, which if
burned again, burn as less intense ground fires. Thus it would seem that more frequent burning of the chaparral, perhaps
through the use of controlled burning in the spring months, would reduce the fire hazard at the urban wildlands interface
in southern California. By fragmenting the landscape using fire to create a landscape mosaic or patchwork, some
biogeographers believe that fire hazad can be reduced. Others argue that because even one or two years worth of grass
growth on previously burned sites are flammable, the spread of a fire—and thus fire hazard—are controlled by weather
systems. In essence they argue that the dry Santa Annas wins that blow in late summer and fall will govern how and
where a fire burns regardless of fuel load. A raging debate continues between advocates of these conflicting views.
Another question concerns whether chaparral goes through succession in the formal sense. After a fire the chaparral
site is invaded by grasses and other annuals (some of which sprout only after a hot fire). These are gradually displaced by
chaparral shrubs, however, for succession to occur in the “Clementian” sense a chaparral community should gradual
succeed towards a predictable climax state with a given species composition. In other words, if we were to track a
chaparral plot for a long enough period of time we should be able to track its progression towards a final climax and we
should be able to determine that climax in advance if we know the environmental conditions of the site. But chaparral
3.11
does not seem to follow the classical climax progression, indeed some argue that succession does not apply in
chaparral communities. Rather than proceeding through a regular series of seres, chaparral appears to be govered by the
“first come—first served” rule. That is to say, following an intense fire a race begins to colonize a burned site. The
individual that reach the site first and take hold (whether through shoots from established root systems or by seed) are the
ones that are likely to remain on the site. In summary, by studying the vegetation on sites with different, known fire
histories, we can draw some conclusions about the relationships between fire regime, succession and fire hazard.
Note on chaparral location.
3.12
LEAF STRUCTURE, FORM AND BEHAVIOR
Leaves are marvelously adapted to serve as light gathering, photosynthetic organs. They can be round, strap-like,
needle-like, or heart-shaped and their margins range from smooth to serrate. A complete leaf is composed of a blade,
petiole, and stipules, any one of which may be lacking or highly modified. The expanded, flattened and broad body of a
typical leaf is the blade which is the site of most of the photosynthesis in the plant. The blade of a leaf is held by its
supporting stalk, or petiole, at an angle almost perpendicular to the rays of the sun. A leaf blade without a petiole and
attached directly to the stem is said to be “sessile”. Some leaves “track” the sun, moving so that they constantly face it. If
leaves were thicker, the outer layers of cells would absorb so much of the light that the interior layers of cells would be
too dark and unable to photosynthesize.
The form or shape of a leaf results from a combination of genetic, environmental and developmental influences. A
plant species tends to bear leaves of some broadly defined type. The leaf is either simple, consisting of a single blade, or
compound, consisting of more than one blade, or leaflets. In some species the leaflets are divided and are called doubly
compound leafs. A compound leaf may bear its leaflets in either a: pinnate fashion---feather-like, with leaflets on either
side of an axis; or palmate fashion, like a palm or hand with leaflets radiating from a central point.
Venation is the arrangement or positioning of the veins (vascular bundles) in the leaf blade. Leaves of most
monocots, such as grasses, have parallel venation, meaning that their main veins are parallel to each other without
intersecting. Leaves of most dicots have net or reticulate venation, meaning that smaller veins branch out from a large
central midrib and intersect. There are two main patterns of net venation; 1) palmate with the main veins radiating from
the point where they join the petiole; and 2) pinnate with one central vein or midrib which has lateral veins arising along
its length and at angles from it.
DESCRIPTION AND CLASSIFICATION OF LEAF PARTS
Leaves are described and classified by their outlines, margins, tips, bases, plane of the blade, venation pattern, surface
texture, length and nature of the petiole (the leaf stem that connects the leaf base to the branch or stipule) and by how the
leaves are arranged on the plant. Plant taxonomists recognize and have named more than 20 types of leaf margins and
almost as many different outline forms. They recognize about a dozen shapes of leaf tips and another dozen of leaf bases.
3.13
Types of Leaves
Leaves are either simple or compound. A leaf with the blade in a single part (whole), although it may be variously
divided, is a simple leaf, while one with the blade divided into smaller, blade-like parts (leaflets or pinnae) is termed
compound. The main axis of the leaf to which the leaflets are attached is called the rachis. Leaflets may be sessile
(attached directly to the rachis) or may be attached to the rachis by stalks called petiolules. (See Figure 1)
To determine whether a leaf is simple or compound, follow it to the stem until an axillary bud is reached. Buds are
short, embryonic stem tips bearing leaves or flowers or both while axillary is the term applied to a bud located in the axil
of a leaf (the axil is the angle between the upper side of a leaf or stem and the supporting stem or branch). Buds occur
only in the axils of a complete leaf, not in the axils of the leaflets. In some plants, especially if immature, it may be
difficult to find the axillary bud. In such cases, it may be necessary to determine whether a leaf is a variously divided
simple leaf or if it is a compound leaf. Generally, if the leaflets are well-developed and separate from the rachis, the leaf
is regarded as compound.
3.14
Compound Leaves
To determine whether a leaf is simple or compound, follow it to the stem until an axillary bud is reached. Buds are
short, embryonic stem tips bearing leaves or flowers or both while axillary is the term applied to a bud located in the axil
of a leaf (the axil is the angle between the upper side of a leaf or stem and the supporting stem or branch). Buds occur
only in the axils of a complete leaf, not in the axils of the leaflets. In some plants, especially if immature, it may be
difficult to find the axillary bud. In such cases, it may be necessary to determine whether a leaf is a variously divided
simple leaf or if it is a compound leaf. Generally, if the leaflets are well-developed and separate from the rachis, the leaf
is regarded as compound.
If compound and the leaflets are attached to both sides of a central rachis, the leaf is once-pinately compound. If they
diverge from a common point at the end of the petiole, much like fingers from the palm of the hand, the leaf is palmately
compound. Leaflets come in up to eight general patterns (four to eight patterns can be recognized depending on the level
of detail and differentiation): 1) Palmately compound, 2) Palmately Trifoliate (Ternate), 3) Biternate, 4) Pinnately
Trifoliate, 5) Odd-Pinnately compound, 6) Even-Pinnately compound, 7) Bipinnately compound and 8) Tripinnate. (See
Figure 2)
3.15
Leaf Arrangements
The arrangement of leaves concerns the pattern by which they are positioned in relation to each other as they extend
from their attachment to a node on a branch. Leaf arrangements come in five possible forms: (See Figure 3)
1) Alternate: A single leaf at each node and thus not opposite each other.
2) Opposite: Two leaves attached to the same node and thus opposite each other.
3) Whorled: More than two leaves at each node.
4) Fascicled: Bundles of two to five leaves enclosed at their base by a sheath (common among most species of pine
trees)
5) Clustered: False whorls meeting at tips of spurs, without a sheath around them.
3.16
Leaf Shapes
Descriptive terms for leaf shapes attempt to identify the outline form of the leaf. Twenty-four leaf shapes are depicted
in the line drawings of Figure 4. (See glossary for definitions of leaf shapes)
3.17
Leaf Margins
Descriptive terms for leaf margins attempt to identify the shapes, forms and characteristics of leaf blade margins
(edges). Eighteen leaf margins are depicted in Figure 5. (See glossary for definitions of leaf margins)
3.18
Leaf Venation Patterns
Venation is the arrangement or positioning of the veins (vascular bundles) in the leaf blade. Leaves of most
monocots, such as grasses, have parallel venation, meaning that their main veins are parallel to each other without
intersecting. Leaves of most dicots have net or reticulate venation, meaning that smaller veins branch out from a large
central midrib and intersect. There are two main patterns of net venation; 1) palmate with the main veins radiating from
the point where they join the petiole; and 2) pinnate with one central vein or midrib which has lateral veins arising along
its length and at angles from it. Descriptive terms for leaf venation patterns attempt to identify the venation pattern of leaf
blades. Seven leaf venation patterns are depicted in the line drawings of Figure 6. (See glossary for definitions of
venation patterns)
3.19
Leaf Apex (plural is Apices)
Descriptive terms for leaf apex (tip farthest removed from the petiole) attempt to identify the shape of leaf tips.
Eleven apices shapes are depicted in the outline drawings of Figure 7. (See glossary for definitions of apices shapes)
3.20
Leaf Base
Descriptive terms for leaf bases attempt to identify the shape of the leaf blade at the base where the petiole is
attached. Twelve base shapes are depicted in the example diagrams of Figure 8. (See glossary for definitions of leaf base
shapes)
3.21
Leaf Surfaces, Surface Covering and Texture
The surface features of angiosperm leaves provide many valuable taxonomic characteristics. The terminology tends
to be somewhat subjective and in practice is difficult to apply. Fifteen descriptive terms for leaf surface covering and
texture attempt to distinguish among the different textural sensations or feel conveyed by the leaf top or bottom.
Arachnoid leaves have surfaces of entangled hairs giving a cobwebby appearance.
Ciliate leaves possess a marginal fringe of hairs.
Coriaceous leaves have surfaces with a tough and leathery texture.
Floccose leaves have a surface with irregular tufts of loosely tangled hairs; has a woolly appearance.
Glabrous leaves are without hairs and therefore have surfaces that are relatively smooth to very smooth.
Glandular leaves have a surface texture that is somewhat sticky resulting from a sticky substance being secreted by tiny
glands in the leaf.
Glaucous leaves have surface with a waxy appearance due to a bloom or powdery coating of wax.
Hirsute leaves possess long shaggy hairs, often stiff or bristly to the touch.
Hispid leaves possess a surface that is covered with stiff or bristly hairs.
Pilose leaves have a surface with scattered, long, slender, soft hairs.
Pubescent leaves have many fine, short hairs and an almost velvety feel.
Sericeous leaves are covered with soft, silky hairs, usually all pointing on one direction.
Strigose leaves possess stiff hairs often appressed (pressed next to the stem) and pointing on one direction.
Tomentose leaves have a surface with densely matted soft hairs forming a wool-like texture.
Villous leaves are covered with long, fine, soft hairs.
3.22
References and further reading
Collins, Barbara. Key to Coastal and Chaparral Flowering Plants of Southern California. California State University
Foundation, Northridge, CA. 1972.
Conrad, C.E. 1987. Common Shrubs of Chapparral and Associated Ecosystems of Southern California. USDA Forest
Service.
Keeley, J and Fotherington, C.J. 2003. Impact of Past, Present, and Future Fire Regimes on North American
Mediterranean Shrublands. In Veblen, T. et al. Fire and Climate Change in Temperate Ecosystems of the Western
Americas. New York: Springer.
Raven, Peter H. Native Shrubs of Southern California. University of California Press: Berkeley and Los Angeles. 1966.
MacDonald, G. 2003. Biogeography. Wiley.
3.23
GLOSSARY
Acute [Latin. acutus: meaning sharpened]. Leaf tip shape that is pointed and sharp ending in a point; not blunt or
obtuse. Ending in a point that is less than a right angle, but not acuminate. Distinct and sharp but not
elongated.
Acicular [Latin. aci: needle]. Needle-like or spine-like shape of leaf.
Acuminate [Latin. acuminatus: has the meaning of sharpness]. Leaf tip shape of a tapering tip that is an extension
from a broader and more blunt near end of leaf.
Angiosperm [Greek. angion: vessel and sperma (meaning seed)]. One of the flowering plants; literally, one whose
seed is carried in a “vessel” (the vessel is the fruit).
Annual A plant that completes its life cycle in one growing season (usually less than one year).
Apiculate [Latin. From apex or apiculus meaning tip or point]. Leaf tip shape where the leaf terminates with a
short, abrupt point.
Arcuate [Latin. arcuare meaning a bow]. Leaf venation pattern where the veins are disposed like curved or arced
bows extending away from the midrib.
Aristate [Latin. From arista meaning awned or bristled]. Leaf tip shape that is tipped with a sharp spine or bristle.
Auriculate [Latin. auricula meaning ear or ear lobe]. Leaf base shape that appears to have ear-like parts such as ear
lobes.
Biennial Referring to a plant whose life cycle includes vegetative growth in the first year and flowering and
senescence (death) in the second year. Contrast with annual and perennial.
Biochore Term introduced by Pierre Dansereau in his 1957 publication, Biogeography. The biochore is the
geographical environment where certain dominant life-forms appear to be adapted to a particular conjunction of
meteorological factors; each biochore is characterized by a major type of vegetation; within each biochore
there develops one or more formations and within each of these formations, climax areas can be distinguished.
Not
all
the space is taken up by climax vegetation, for the nature of the topography will allow a differentiation into many
habitats. A habitat may harbor one or more ecosystems which may themselves be comprised of one or more
communities.
Biomass The amount or volume of living material (weight of living plant and animal tissue) per unit of land area.
Biome A biome is the largest terrestrial ecosystem convenient to recognize.
Bud primordium (bud for short) In plants, a small mass of potentially meristematic tissue found in the angle
between the leaf stalk and the shoot apex. Will give rise to a lateral branch under appropriate conditions.
Cambium A layer of delicate meristematic tissue between the inner bark or phloem and the wood or xylem,
which produces new phloem on the inside in stems and roots. It produces all secondary growth in plants and
is responsible for the annual rings of wood. A meristem gives rise to radial rows of cells in stem and root
increasing them in girth; commonly applied to the vascular cambium which reproduces wood and phloem, and
the cork cambium, which produces bark.
Caudate [Latin. cauda has the meaning of tail]. Leaf tip shape that appears as a tail-like appendage.
Ciliate Leaf margin having an edge of fine cilia-like very short projections.
3.24
Cleft
Leaf margin having lobes or divisions extending halfway or more than halfway to the midrib or base.
Clasping Leaf base shape where the base of the leaf partly or wholly surrounds the stem.
Climax Stage The final seral phase in a sere.
Conifer [Greek konos: cone plus phero: carry]. One of the cone-bearing gymnosperms, mostly trees such as pines
and firs.
Cordate [Latin. cordatus meaning heart shaped]. Leaf shape that is heart-shaped in its outline with the notched end
at the base. Leaf base shape that is heart shaped with notch at center of base.
Crenate Leaf margin having the edge lowly notched or scalloped so as to form rounded or blunt teeth.
Cuneate [Latin. cuneatus meaning wedge shaped]. Leaf base shape that is triangular or wedge shaped and tapering
or gradually narrowing toward the point of attachment at the base.
Cuspidate [Latin. From cuspidatus meaning single point or projection]. Leaf tip shape that is furnished with a sharp
tip or cusp which may or may not be curved.
Cuticle [Latin. From cuticul meaning the skin]. A very thin hyaline (horny and somewhat transparent) film covering
the surface of plants, derived from the outer surface of the epidermal cells.
Deltoid [Greek. Delta from the triangular shape of the Greek letter delta]. Leaf shape with the outline form of a
delta (triangular).
Dentate Leaf margin having a toothed edge or tooth-like projections or processes that point outward.
Denticulate Leaf margin having a finely or minutely toothed edge or minute tooth-like projections or processes.
Dicot (short for dicoltyledon) [dis: two plus kotyledon: a cup-shaped hollow]. Any member of the angiosperm class
Dicotyledonae, flowerring plants in which the embryo produces two cotyledons prior to germination. Leaves
of most dicots have major veins arranged in a branched pattern.
Divided Leaf margin description where the margin is separated into distinct portions by incisions that extend to the
midrib or the base.
Doubly Serrate Leaf margin description where the margin has small serrations on larger serrations.
Ecology The word ecology was coined in 1869 by Ernst Haeckle by joining the Greek words "oikos" meaning dwelling
place and logos (meaning "study of." The study of ecology means examining how plants and animals and their nonliving (physical) environment interact and influence each other.
Ecosystem A term introduced in the 1930s which became popular in the 1960s. An ecosystem is a functioning
(interactive and dynamic) assemblage of the biological community (plants and animals), soils, water, humans,
meteorological factors and time, of whatever size.
Elliptic Leaf margin description where the leaf outline has the shape of an ellipse with the tip and base not rounded
but nearly or fully pointed. Usually more than twice as long as broad.
Emarginate [Latin. emarginatus meaning deprived of its edge or margin]. Leaf tip shape that is notched or indented
at the apex.
3.25
Embryo [Greek. em: in plus bryein: to grow] A young plant sporophyte while it is still contained within a protective
structure such as the seed.
Entire Leaf margin description where the margin is smooth without notches, indentations or lobes.
Ephemeral [Greek. ephemeros: short lived]. A short lived plant or plant that proceeds quickly through its life cycle.
Epidermis [Greek. epi: on, over, upper skin plus derma: skin]. A thin layer of cells forming the outer layer or
skin of seed plants and ferns.
Erose Leaf margin having an edge that is uneven or irregularly incised as if gnawed away.
Falcate [Latin. falcatus meaning sickle shaped]. Leaf shape there the leaf outline is curved or hooked like a sickle
or scythe.
Fascicled [from fascis, Latin for bundle or packet]. A cluster or tuft of leaves that are bundled together at the
petiole/stipule connection.
Fimbriate [Latin. from fimbriae meaning fringe or border]. Leaf margin having an edge or fringe of fine hairs or
filiform processes.
Fruit In angiosperms, a ripened and mature ovary (or group of ovaries) containing the seeds. A modified flower part
that encloses a seed or seeds.
Gall Any abnormal vegetable growth on a plant caused by various agents, e.g. insects, fungi, bacteria, virus,
chemicals. For oaks, stem galls (sometimes called gall apples) are somewhat common and are related to the
activity of Cynipid wasps.
Glabrous [Latin. glaber: smooth, hairless]. Leaf texture where the leaf surface and bottom is without hair and
therefore smooth.
Glandular Leaf texture where the leaf is somewhat sticky.
Gymnosperm [Greek. gymnos: naked plus sperma: seed]. A plant, such as a pine or other conifer, whose seeds
do not develop within an ovary (hence the seeds are “naked”).
Halophyte [Greek. hals: salt plus phyt(on): meaning plant]. A plant which grows in salty or alkaline soil.
Hastate [Latin. hastatus meaning armed with a spear]. Leaf shape where the outline of the leaf is triangular or
shaped like a halberd (weapon of an ax like blade on a shaft) but with two spreading lobes at the base. Leaf
base shape with two spreading lobes at the base.
Herbaceous Plant An annual plant that is non-woody.
Hispid [Latin. hispidus: rough or shaggy]. Leaf texture with the sensation of stiff or bristly hairs.
Hygrophyte [Greek. hygros: wet or moist: plus phyt(on): meaning plant]. A plant that thrives in wet or very moist
ground.
Incised Leaf margin sharply, deeply and somewhat irregularly notched.
Laciniate Leaf margin having an edge cut into narrow irregular pointed lobes that appear slashed and/or jagged.
Lanceolate A leaf shape characterized by a relatively narrow outline with a broadish base that that tapers toward the
tip. Much longer than wide.
3.26
Lobed Leaf margin having lobes or divisions extending less than halfway to the middle of the base or midrib.
Linear Leaf shape where the leaf outline is narrow, elongated and with nearly parallel sides.
Lyrate [Latin. From lyra: pertaining to a lyre shaped stringed instrument]. Leaf shape where the outline appears to
be pinnate and divided transversely into several lobes with the smallest lobes at the base of the leaf.
Meristem [Greek. meristos: divided]. Plant tissue made up of actively dividing cells. The growing regions of a
plant.
Mesophyte [Greek. mesos: middle plus plus phyt(on): meaning plant]. A plant growing under conditions of well
balanced moisture supply.
Monocot (short for monocotyledon) [Greek monos: one plus kotyledon: a cup shaped hollow]. Any member of the
angiosperm class Monocotyledonae, plants in which the embryo produces but a single cotyledon (seed leaf).
Leaves of most monocots have their major veins arranged parallel to each other.
Mucronate Leaf tip shape that is slightly rounded with one-half of the tip projecting slightly beyond the neighboring
half or abruptly tipped with a small point projecting from the midrib.
Nectar In flowers, a nourishing solution of sugars and amino acids.
Obcordate [Latin. ob: against with the sense of reversely; Latin: cordatus meaning heart shaped]. Leaf shape that is
heart-shaped in its outline with the notched end at the tip..
Oblanceolate [Latin: ob against with the sense of reversely]. A leaf shape that is inversely lanceolate (broadest part
near the apex).
Oblique [Latin. obliqu meaning slanted]. Leaf base shape that is uneven at the base; asymmetrical having one side
of the blade lower on the petiole than the other.
Oblong A leaf shape where the leaf outline is somewhat elongated from a square, rectangular or circular form.
Obovate [Latin. ob: against with the sense of reversely] A leaf shape that is inversely ovate (the broadest part near
the apex).
Obtuse [Latin. obtustus meaning dulled]. Leaf tip shape that is blunt or rounded at the extremity, not sharp or acute.
Orbicular [Latin. orbi meaning circular or rounded]. Leaf shape that is circular or rounded in outline.
Oval Leaf shape where the outline is elliptical with rounded tip and base.
Ovate
[Latin. ovat meaning egg]. Egg shaped leaf with the broader end at the base of the leaf.
Palmate [Latin. palmatus: shaped like a hand with the fingers spread]. Said of leaves or leaflets having veins or
lobes radiating from a common center
Parted Leaf margin description where the margin is separated into distinct portions by incisions that extend nearly to
the midrib or the base
Pedogenic [Greek. pedo: soil plus genic: stem ending meaning “producing or arising from”]. Soil producing.
3.27
Peltate [Latin. from peltatus or pelta which is a small light shield used by foot soldiers in ancient Greece]. Leaf
base that is somewhat roundish and shield shaped due to the stalk/support attached to the lower surface at a
distance from the margin.
Perfoliate [Latin. perfoliata meaning a plant with a stalk that seems to grow through or pierce its leafage]. Leaf
base shape having the stem apparently passing though the leaf, owing to congenital union of the basal edges of
the leaf around the stem.
Perrenial plant that has a life cycle of more than two years.
Phloem [Greek. phloos: bark]. In vascular plants the specialized food conducting tissue in the vascular system that
transports dissolved sugars.
Photosynthesis [Greek. Literally ‘synthesis out of light”]. Metabolic processes, carried out by green plants, by
which visible light is trapped and the energy used to convert the sunlight into the chemical energy of glucose.
Phreatophyte [Greek. Phreat meaning artificial well]. A long rooted plant that absorbs its water from the water
table or the soil above it. “Phreatic” notes or pertains to that layer of soil or rock through which water may
enter wells or from which springs and seeps may emerge.
Pinnate or Pinnately [Latin. pinna: a feather or fin]. In plants, the positioning of leaflets on each side of a common
stem in a feather-like arrangement. Also the leaf venation pattern where the veins are arranged parallel to each
other like the ribs of a feather extending at a near right angle from the midrib.
Pollen [Latin. Fine powder, dust]. The fertilizing element of seed plants, containing the male gametophyte and the
gamete, at the stage in which it is shed. The yellow, powder-like male sex cells on the stamens of a flower.
Pubescent
Leaf texture where the leaf surface possesses many fine, short hairs and an almost velvety feel.
Reniform [Latin. reni meaning kidney]. Kidney shaped leaf outline.
Repand Leaf margin where the shape is slightly wavy.
Reticulate [Latin. reticulum meaning net]. Leaf venation pattern where the veins are disposed like the threads of a net.
Rounded Leaf tip with a broad shaped arch at the apex. Leaf base with a broad-shaped arch.
Runcinate [Latin. from runcinatus meaning planed off]. Leaf shape having an outline that is pinnately incised with
the lobes or teeth curved backward.
Seed A fertilized , ripened ovule of a gymnosperm or angiosperm. Consists of the embryo, nutritive tissue and a
seed coat.
Sagittate [Latin. sagitta pertaining to arrow or arrowhead]. Leaf shape having the outline of an arrowhead; leaf
base shape similar to the rear portion of an arrowhead.
Scalelike Leaf shape formed by the arrangement of leafs or leaflets in tight scale-like pattern.
Seral Stage(s) The various recognizable phases of succession that characterize the changing ecosystem as the
dynamics and component living organism (plants and animals) evolve toward a "climax" stage (stability or
equilibrium).
Sere The various stages or phases of plant and animal succession that occur in an area following a substantial
alteration to the area’s ecosystem.
3.28
Serrate Leaf margin notched on the edge like a saw with the marginal teeth pointing toward the apex of the leaf.
Serrulate Leaf margin finely or minutely notched on the edge like a saw.
Sessile Leaf [Latin. sessilis: fit for sitting on, low enough to sit on, dwarfish]. Leaf without a petiole and the blade
seated directly on the stem.
Shrub A bushy, woody plant with several permanent stems instead of a single trunk. Shrubs generally are shorter
than trees.
Sinuate - Leaf margin having the edge strongly or distinctly wavy.
Spatulate [Latin. spatula meaning a broad place]. Leaf shape having an outline of a broad rounded end and a
narrow attenuated base.
Stipule One of a pair of lateral appendages, often leaf-like, at the base of a leaf petiole in many plants.
Stoma (plural stomata) An aperture (opening) in the epidermis of leaves that regulates the passage of gases into and
out of a plant.
Succulent [Latin. succus: juice plus lentus: a suffix meaning full of]. A plant having fleshy and juicy tissues.
Taproot The organ that results when the primary root grows downward and becomes the largest root.
Taxonomy The science of grouping organism according to their presumed natural relationships.
Tomentose [Latin. tomentum: stuffing of wool or hair for cushions]. Leaf texture where the surface is woolly;
covered by many wavy hairs forming a wool-like texture.
Transpiration [Latin. spirare: to breath]. The evaporation of water from plant leaves through the stomata and
from stems, driven by heat from the sun, and providing the motive force to raise water from the roots.
Truncate [Latin. truncatus meaning lopped]. Leaf tip shape that is broad or cut squarely at the end as if cut off
transversely or squarely.
Undulate Leaf margin having lobes or sections that are wavy or bending with successive curves in alternate
directions.
Vascular Cambium The lateral meristem in a plant that produces additional vascular tissue (wood if the xylem)
Vascular Plant A plant that has xylem and phloem.
Vascular Tissue The tissue that transports water and food from one part of a plant to another.
Venation The arrangement of veins in a leaf.
Woody Plant A perennial vascular plant containing xylon ltissue and adapted for growth year after year, such as a
tree.
Xerophyte (xerophytic) [Greek. xero: dry plus phyto: plant]. A plant adapted for growth under dry conditions.
Xylem [Greek. xylon: wood] In vascular plants, the woody tissue that transfers water and minerals from the roots
to the leaves.