Chapter 13 Light and Photosynthesis in Seagrass Meadows
305
Table 1. List of model symbols, their definitions and dimensions. Parenthetic notation of λ and z indicates that the
quantity is wavelength (λ) and/or depth (z) dependent, respectively.
Symbol
Definition
Dimensions
Fundamental quantities
T
Daylength
s day –1
θ
Polar angle
deg
µ
Cosine of polar angle
Dimensionless
z
Depth within the canopy
m
z
Vertical thickness of canopy layers
m
Canopy architecture properties
B(z)
Biomass fraction in layer z
Dimensionless
β
Nadir bending angle of the seagrass canopy
degrees
h m
Maximum canopy height
m
h c
Realized canopy height
m
h(z)
Height above the seabed
m
I
Intermediate height of sigmoid biomass distribution
m
L
Canopy leaf area index
m
2 leaf m –2 seabed
L s
Leaf area per shoot
m
2 leaf shoot –1
l(z)
Leaf area index at depth z
m
2 leaf m –2 seabed
l p (z)
Horizontally projected leaf area at depth z
m
2 leaf m –2 seabed
t L
Leaf thickness
m
s
Shape factor for sigmoid biomass distribution
Dimensionless
ψ
Percent of canopy biomass at the seabed
Dimensionless
Radiometric quantities
E d (λ, z)
Downwelling plane irradiance transmitted through layer z
W (or quanta s –1 ) m –2 nm –1
E u (λ, z)
Upwelling plane irradiance transmitted through layer z
W (or quanta s –1 ) m –2 nm –1
i
Incident flux
W (or quanta s –1 )
t
Transmitted flux
W (or quanta s –1 )
a
Absorbed flux
W (or quanta s –1 )
r
Reflected flux
W (or quanta s –1 )
Inherent optical properties
a L (λ)
Leaf absorption coefficient
m –1 of leaf thickness
A L (λ)
Leaf-specific absorptance
Dimensionless
D(λ)
Leaf-specific absorbance
Dimensionless
R L (λ)
Leaf reflectance
Dimensionless
R b (λ)
Seabed reflectance
Dimensionless
R d (λ, z)
Canopy reflectance of downwelling irradiance
Dimensionless
R u (λ, z)
Canopy reflectance of upwelling irradiance
Dimensionless
Apparent optical properties
K d (λ)
Water column attenuation of downwelling irradiance
m –1
K u (λ)
Water column attenuation of upwelling irradiance
m –1
¯
µ d (z)
Average cosine of downwelling irradiance
Dimensionless
¯
µ u (z)
Average cosine of upwelling irradiance
Dimensionless
Photosynthetic properties
PUR(z)
Photosynthetically utilized irradiance in layer z
quanta absorbed m
−2 leaf s
−1
φ p
Quantum yield of photosynthesis
Mol C mol
−1 PUR
P max
Rate of light saturated photosynthesis
Mol C m
−2 leaf s
−1
P i (z)
Biomass-specific photosynthesis in layer z
Mol C m –2 leaf s –1
P c
Depth-integrated biomass-specific photosynthesis
Mol C m –2 leaf s –1
P d
Daily integrated biomass-specific photosynthesis
Mol C m –2 leaf day –1
Metabolic respiratory demand
Mol C m –2 leaf day –1
length-frequency distribution of leaves within a population. Most leaves in the population are of intermediate length, but the fact that all leaves emerge
from a basal sheath means that the fractional amount
of leaf biomass within the canopy is greatest near
the seafloor and decreases non-linearly toward the
top of the canopy (Fig. 1). This general relationship can be represented by a sigmoid function that
305
Table 1. List of model symbols, their definitions and dimensions. Parenthetic notation of λ and z indicates that the
quantity is wavelength (λ) and/or depth (z) dependent, respectively.
Symbol
Definition
Dimensions
Fundamental quantities
T
Daylength
s day –1
θ
Polar angle
deg
µ
Cosine of polar angle
Dimensionless
z
Depth within the canopy
m
z
Vertical thickness of canopy layers
m
Canopy architecture properties
B(z)
Biomass fraction in layer z
Dimensionless
β
Nadir bending angle of the seagrass canopy
degrees
h m
Maximum canopy height
m
h c
Realized canopy height
m
h(z)
Height above the seabed
m
I
Intermediate height of sigmoid biomass distribution
m
L
Canopy leaf area index
m
2 leaf m –2 seabed
L s
Leaf area per shoot
m
2 leaf shoot –1
l(z)
Leaf area index at depth z
m
2 leaf m –2 seabed
l p (z)
Horizontally projected leaf area at depth z
m
2 leaf m –2 seabed
t L
Leaf thickness
m
s
Shape factor for sigmoid biomass distribution
Dimensionless
ψ
Percent of canopy biomass at the seabed
Dimensionless
Radiometric quantities
E d (λ, z)
Downwelling plane irradiance transmitted through layer z
W (or quanta s –1 ) m –2 nm –1
E u (λ, z)
Upwelling plane irradiance transmitted through layer z
W (or quanta s –1 ) m –2 nm –1
i
Incident flux
W (or quanta s –1 )
t
Transmitted flux
W (or quanta s –1 )
a
Absorbed flux
W (or quanta s –1 )
r
Reflected flux
W (or quanta s –1 )
Inherent optical properties
a L (λ)
Leaf absorption coefficient
m –1 of leaf thickness
A L (λ)
Leaf-specific absorptance
Dimensionless
D(λ)
Leaf-specific absorbance
Dimensionless
R L (λ)
Leaf reflectance
Dimensionless
R b (λ)
Seabed reflectance
Dimensionless
R d (λ, z)
Canopy reflectance of downwelling irradiance
Dimensionless
R u (λ, z)
Canopy reflectance of upwelling irradiance
Dimensionless
Apparent optical properties
K d (λ)
Water column attenuation of downwelling irradiance
m –1
K u (λ)
Water column attenuation of upwelling irradiance
m –1
¯
µ d (z)
Average cosine of downwelling irradiance
Dimensionless
¯
µ u (z)
Average cosine of upwelling irradiance
Dimensionless
Photosynthetic properties
PUR(z)
Photosynthetically utilized irradiance in layer z
quanta absorbed m
−2 leaf s
−1
φ p
Quantum yield of photosynthesis
Mol C mol
−1 PUR
P max
Rate of light saturated photosynthesis
Mol C m
−2 leaf s
−1
P i (z)
Biomass-specific photosynthesis in layer z
Mol C m –2 leaf s –1
P c
Depth-integrated biomass-specific photosynthesis
Mol C m –2 leaf s –1
P d
Daily integrated biomass-specific photosynthesis
Mol C m –2 leaf day –1
Metabolic respiratory demand
Mol C m –2 leaf day –1
length-frequency distribution of leaves within a population. Most leaves in the population are of intermediate length, but the fact that all leaves emerge
from a basal sheath means that the fractional amount
of leaf biomass within the canopy is greatest near
the seafloor and decreases non-linearly toward the
top of the canopy (Fig. 1). This general relationship can be represented by a sigmoid function that