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WEED INDICATOR KEY, DISCUSSION, AND NOTES
This is a discussion of terms used in the weed vignettes. Some of the terms are common
adjectives but have specific meanings when used in the context of plant indicators and
ecology. Numbers are used to show increasing level of the quality under consideration.
Not all of these characteristics are included in the vignettes. In the book these will
be noted if there is information available.
Elements There are different types of qualities that are important in different
situations:
indicator - the presence of this weed is often associated (but not always) with the
given level of the element.
tolerates - The weed can grow with a high or low level of this element.
ratio of base saturation - The percentage of the binding sites on the soil that are
occupied by this element.
indefinite or non-specific response - This weeds growth doesn't respond dramatically to
high or low levels of this element.
accumulator - An element is actively concentrated in the plant tissue, higher than is
usual for other plants growing in the same soil.
content indicates nutrient level - Some plants have nutrient levels in their tissues
that reflect the amount is the soil.
pulls up from subsoil - Deep roots mobilize minerals and bring to above ground parts,
which would be available to the next crop.
data - This is a small bit of data, not enough information to establish This plant as
an indicator. This information may be useful but is not verified by a lot of information
or experience.
reference - These notes are followed by a 4 digit number in parentheses that is the
code for the literature reference. Anything not referenced can be considered the opinion
of the author.
Nitrogen, N, nitrate, ammonia supply, description of levels:
1 only in soils very poor in mineral nitrogen
3 mostly in poor soil
5 mostly in intermediate soil
7 mostly in soil rich in mineral nitrogen
8 nitrogen indicator
9 only in soil very rich in mineral nitrogen, indicating pollution, manure deposits or
a similar situation
Salt, Na, sodium
millimhos 1880
0 very sensitive
1 sensitive 3-2
3 mildly tolerant 6-3
5 tolerant, but more freq in non saline soil 12-6 I
7 facultative halophyte, mostly in saline soil II
9 obligatory halophyte, only in saline soil III
Water, soil moisture or water level
1 extremely dry soil, e.g. bare rocks
3 in dry soil
5 in fresh soil, intermediate conditions
7 in moist soils that do not dry out
9 wet soil, often not well aerated
10 frequently inundated soil
pH, acid and base
range description C20,0460 pH phytosocial
X - indifferent - 4-8 no definite response
1 - only very acid A <5 moderate to strong acido freq
2 -
3 - mostly acid a <5.5 weak to strong acido freq
4 -
5 - weakly acid b 5.0-6.0 weak to moderate basi freq
6 -
7 - neutral, also A & B 7
8 - 7.5
9 - only neutral or B B 5.2-7.5 moderate to strong basi freq
0 - basic >7 only on basic
Organic Matter
relative amount for low to high
or % if data available
Compaction
Good soil is one part each rock particles, water and air. Soil life helps to maintain
this balance. There are several ways that this balance can be destroyed. There is
mechanical compaction, waterlogging, salt or alkali buildup, and poisons like herbicides.
surface compacted or crust
heavy machinery compaction
plow pan - A hard layer formed by the sole of the plow pushing down on the soil,
8 to 12 inches below the surface.
worked wet - causing clay soil plates to pack tightly together
dense - soil that for whatever reason is non-porous
loose, drains easily
Soil Classification
Verbal description of the soil textures and origins.
sand
sandy-loam
loam
clay-loam
clay
rocky
alluvial, glacial, etc
Habit and Control
Notes from ref. 4390, Weeds, unless otherwise indicated
Temp Average: average of monthly means in 'C (values below 0'C treated as 0) from
ref 1694 unless otherwise indicated.
Temperature Figure
Description Altitude Latitude Mean Ann Biotemp
0 - very cold nival polar <1.5'C
1 - only in cold climate alpine subpolar P 1.5-3
2 - subalpine boreal B 3-6
3 - mostly in cool climate montane cool temperate C 6-12
5 - intermediate submontane warm temperate W 12-24
7 - mostly in warm climate
8 - premontane subtropical S
9 - only very warm climate mediterranean
10- tropical tropical T
Humidity Provinces mean annual rainfall in mm
description humidity T S W C B P
x - desert superarid 125- 125- 125- 125- <125
t - thorn perarid 250- 250- 250-
s - steppe arid 250-
v - very dry semiarid 500-
d - dry subhumid 1000- 500- 500- 125- <125
m - moist humid 2000- 1000- 1000- 500- 250- 125-
w - wet perhumid 4000- 2000- 2000- 1000- 500- 250-
r - rain superhumid >8000 >4000 >4000 >2000 >1000 >500
Continentality Figure
1 - euoceanic
2 - oceanic
4 - suboceanic
6 - subcontinental
8 - continental
9 - eucontinental
Rainfall in decimeters (dm),
dm X 4 = in, in X 1/4 = dm, dm X 100 = mm
Life Form from Raunkiaer
- according to position of buds during winter
P Phanerophyte, tree normally growing more than 5 m tall
N Nanophanerophyte, shrub or small tree, 0.5 - 5 m tall
Z Woody Chamaephyte, dwarf shrub
C Herbaceous Chamaephyte, herb with buds above ground
Chr C. reptantia, creeping
Chv C. velantia, dwarf bush
Chn C. vine
H Hemicryptophyte, buds near the ground
Hr H. rosulata, basal rosette
Hs H. scaposa, shaft
G Geophyte, buds within the soil, often with storing organs
Gb G. bulbosa, ground bulb
Grh G. rhizomata, ground rhizome
Gr G. radicigemma, root bud
T Therophyte, short lived "annual" plant
Ta T. aestivalia, summer annual
Th T. hivernalia, winter annual
Tb T. biannuellia, biannual
Te T. epeteia, in summer drought, overwintering annual
A Hydrophyte, aquatic plant with normally submerged buds
ep Epiphyte, attached to living plants
li Liana, rooting in the soil, but leaning on other plants
hp Half-Parasite, feeding on other plants, but with green leaves
vp Full-Parasite
s Saprophyte, feeding upon dead organic material
Syntax: Life form; Distribution type
Distribution Types (Feekes, from Sissingh)
V anemochoor, wind
H hydrochoor, water
A anthropochoor, man
Z zoochoor, animal
Au autochoor, self
capital - effective distribution over large distances
lower-case - rather efficient distribution over little distances
(letter) - little efficient distribution over very little distances
Leaf Green
I evergreen
W overwinering green
S summer green
V spring to summer green
Leaf Water
0 hy, hd hydromorphic, water plant
2 he helomorphic, with aeration tissue mainly in the underground organs
4 hg hygromorphic, with soft shadow leaves
6 m mesomorphic,
8 sk scleromorphic, with hard leaves and roots
9 su leaf succulent
A he & sk
B _________
Social, Phytosociological behavior
vegetation units in which the taxon is considered as character species, expressed by
decimals. All info from ref 1880 unless otherwise indicated.
Gr group of classes (decimal because the number of classes is greater than 10)
K character species of a class or of a subordinate unit
O character species of an order or of a subordinate unit
V character species of an alliance
U character species of a suballiance
character species of associations have been omitted, because most of them are valid
only locally
Syntax: Gr. K O V. U
Light
1 full shadow plant, often receiving less than 1%, rarely greater than 30% of full
sunlight
3 shadow plant
5 half shadow plant, more than 10%, but mostly less than 100%
7 half light plant
9 full light plant, rarely receiving less than 50%
() tree seedling in the undergrowth of forests
References
cw Common weeds of the US, (6405)
w Weeds, (4390)
jw Just weeds, (5760)
www Worlds Worst Weeds, (2811)
Glossary
Spudding - digging out weeds with long tap roots with a long chistle like tool.
Harrowing - shallow surface cultivation with a spike-toothed harrow.
Disking - using a disk to cut and turn crops and weeds under the soil.
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