Chapter 20
EXPERIMENTAL STUDY OF STATISTICAL
CHARACTERISTICS OF PLANT CANOPY
RADIATION REGIME
M. Sulev and J. Ross
Tartu Observatory, Toravere, Estonia.
1.
INTRODUCTION
During the last decades, Swedish scientists have studied different aspects
of willow forest growth. Some papers on radiation measurements,
concerning methods of measurements (Perttu, 1970; Lindroth, Perttu, 1981)
and light penetration in willow stand (Eckersten, 1984) have also been
published.
In the joint Swedish-Estonian fast growing forest research project, an
extensive study of the radiation regime of willow plantation was planned,
including global radiation, photosynthetically active radiation (PAR) and net
radiation measurements.
Radiation and phytometrical measurements were carried out during the
growing periods of 1994–1997 in the willow Salix viminalis (clone 78021)
plantation at Tartu Observatory
Estonia. For more
details see Ross, 1994 and Koppel et al., 1996.
Due to the great spatial variability of forest ecosystems, horizontal
averaging of radiation measurements inside the plant canopy constitutes an
important problem. Most radiative transfer approaches (e.g., Ross, 1981)
consider radiation characteristics as a function of height and suppose that
averaging over xy-plane has been made with the necessary accuracy.
However, measurements with one or two sensors at fixed points do not
guarantee this. Different methods of horizontal averaging have been used
187
M.M. Verstraete et al. (eds.), Observing Land from Space: Science, Customers and Technology, 187–200.
© 2000 Kluwer Academic Publishers. Printed in the Netherlands.
EXPERIMENTAL STUDY OF STATISTICAL
CHARACTERISTICS OF PLANT CANOPY
RADIATION REGIME
M. Sulev and J. Ross
Tartu Observatory, Toravere, Estonia.
1.
INTRODUCTION
During the last decades, Swedish scientists have studied different aspects
of willow forest growth. Some papers on radiation measurements,
concerning methods of measurements (Perttu, 1970; Lindroth, Perttu, 1981)
and light penetration in willow stand (Eckersten, 1984) have also been
published.
In the joint Swedish-Estonian fast growing forest research project, an
extensive study of the radiation regime of willow plantation was planned,
including global radiation, photosynthetically active radiation (PAR) and net
radiation measurements.
Radiation and phytometrical measurements were carried out during the
growing periods of 1994–1997 in the willow Salix viminalis (clone 78021)
plantation at Tartu Observatory
Estonia. For more
details see Ross, 1994 and Koppel et al., 1996.
Due to the great spatial variability of forest ecosystems, horizontal
averaging of radiation measurements inside the plant canopy constitutes an
important problem. Most radiative transfer approaches (e.g., Ross, 1981)
consider radiation characteristics as a function of height and suppose that
averaging over xy-plane has been made with the necessary accuracy.
However, measurements with one or two sensors at fixed points do not
guarantee this. Different methods of horizontal averaging have been used
187
M.M. Verstraete et al. (eds.), Observing Land from Space: Science, Customers and Technology, 187–200.
© 2000 Kluwer Academic Publishers. Printed in the Netherlands.