20 Photosynthesis of Vascular Plants:
Assessing Canopy Photosynthesis by Means
of Simulation Models
W. Beyschlag, R.l. Ryel, and M.M. Caldwell
20.1 Introduction
Since the pioneering work of Monsi and Saeki (1953), Davidson and Philip
(1958), and de Wit (1965), plant canopy models have been used to address
numerous ecological questions (Monteith 1965; Norman 1978; Wang and
Jarvis 1990). The level of detail of these models is largely dependent upon
the objectives of the studies for which the models were designed although all
contain routines to calculate net photosynthesis and light penetration into
the canopy. In this chapter we will focus on a series of models which have
been especially developed to address questions concerning competition for
light in plant canopies.
We will start with a rather general description of this modeling approach
and with the development of a family of canopy models for uniformly
structured monotypic plant stands. The presentation will then move to more
complex models for multispecies stands and canopies with nonhomogeneous
structure. Several case studies in which the respective models were employed
to address ecological questions pertaining to plant competition for light and
associated issues will be illustrated.
20.2 General Structure of Canopy Photosynthesis Models
Canopy photosynthesis models generally consist of two components: a
photosynthesis submodel and a microclimatic submodel. The photosynthesis
submodel relates the response of leaf photosynthesis for a plant species to
changes in micro climatic factors (e.g., light, air temperature, ambient CO2
partial pressure, air humidity). The microclimatic submodel is used to calculate micro climatic conditions at any point within the canopy. Calculations
of net photosynthesis are then made for representative portions of the
canopy and the whole plant or canopy rates are calculated by summing these
individual rates weighted by the distribution of foliage.
Assessing Canopy Photosynthesis by Means
of Simulation Models
W. Beyschlag, R.l. Ryel, and M.M. Caldwell
20.1 Introduction
Since the pioneering work of Monsi and Saeki (1953), Davidson and Philip
(1958), and de Wit (1965), plant canopy models have been used to address
numerous ecological questions (Monteith 1965; Norman 1978; Wang and
Jarvis 1990). The level of detail of these models is largely dependent upon
the objectives of the studies for which the models were designed although all
contain routines to calculate net photosynthesis and light penetration into
the canopy. In this chapter we will focus on a series of models which have
been especially developed to address questions concerning competition for
light in plant canopies.
We will start with a rather general description of this modeling approach
and with the development of a family of canopy models for uniformly
structured monotypic plant stands. The presentation will then move to more
complex models for multispecies stands and canopies with nonhomogeneous
structure. Several case studies in which the respective models were employed
to address ecological questions pertaining to plant competition for light and
associated issues will be illustrated.
20.2 General Structure of Canopy Photosynthesis Models
Canopy photosynthesis models generally consist of two components: a
photosynthesis submodel and a microclimatic submodel. The photosynthesis
submodel relates the response of leaf photosynthesis for a plant species to
changes in micro climatic factors (e.g., light, air temperature, ambient CO2
partial pressure, air humidity). The microclimatic submodel is used to calculate micro climatic conditions at any point within the canopy. Calculations
of net photosynthesis are then made for representative portions of the
canopy and the whole plant or canopy rates are calculated by summing these
individual rates weighted by the distribution of foliage.