Leaf Mass Calculation

Some ecological models simulate the dynamics of leaf area for terrestrial ecosystem in which LAI is estimated from the biogeochemical process by

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Jan Feb Mar

Apr May Jun Jul

Aug Sep Oct Nov Dec

Figure 8 Monthly mean LAI values for different vegetation types derived from MODIS LAI product for North America in 2001. The standard deviation is also included. (a) Evergreen needleleaf tree; (b) evergreen broadleaf tree; (c) deciduous needleleaf tree; (d) deciduous broadleaf tree; (e) shrub; (f) grass; (g) cereal crop; (h) broadleaf crop.

Table 2 Observational requirements for leaf area index

Requirement

Horizontal resolution (km)

Observation cycle (day)

Accuracy (%)

Time lag (day)

Applications

WMO

0.01-10

5-7

5-10

1-5

Agricultural meteorology

WMO

10-50

7-30

5-20

1-7

Regional NWP

WMO

0.01-10

7-24

5-20

1-5

Hydrology

WMO

50-100

7-30

5-20

1-7

Global NWP

GCOS

0.1-1

10-30

20-100

10-30

Terrestrial climate

GTOS

0.1-1

10-30

20-100

10-30

Terrestrial climate

GCOS, Global Climate Observing System; GTOS, Global Terrestrial Observing System; NWP, Numerical Weather Prediction; WMO, World Meteorological Organization.

GCOS, Global Climate Observing System; GTOS, Global Terrestrial Observing System; NWP, Numerical Weather Prediction; WMO, World Meteorological Organization.

where S is the specific leaf area (m2 gC_1): projected leaf area per unit mass of leaf carbon. CL is the annual net primary production (NPP) allocated to leaves (gC m~2). Using a transformed eqn of [13], the leaf mass can be calculated with

LAI for different PFTs can be obtained from calculating NPP at a range of different leaf areas by iteration and finding the most suitable LAI. Correspondingly, LAI can be used to select the dominant PFT on the basis of modeled optimal NPP.

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