19.1 Introduction
Water is the most important environmental component for peatland formation and
ecosystem not only in tropical but also in temperate and boreal zones. Vegetation in
peatland grows using water from sky (rain) and upstream of peatland.
Peatland is generally formed in the flat land under wet climate with higher
precipitation and distributed in the world, except Antarctica. Hydrological aspects
of peatland differ between climate, topography, and vegetation.
Tropical peatland develops mainly behind coastal mangrove swamp and extended
to inland under swamp forest (Rieley and Page 1990). Peat is formed from the
decaying organic materials which originated from root, leaf, and trunk growing in
the peat. The main matrix of peat is originated in grass and sphagnum species in the
boreal peatland, but is mainly originated in woody plant species in the tropical
peatland.
Rain is the major water resource in the central area of tropical peatland, where the
oligotrophic peat develops. In the marginal area of the peatland, the major water is
supplied from the (1) rain, (2) outflow from the center of peatland, and (3) river/sea
with minerals/saline materials. The hydrology in the peatland is characterized by the
physical, chemical, and biological characters, which develop with the balance of the
vegetation in the peat and water supplied by the rain and river/sea; therefore,
peatland is very fragile one. Thus, a good understanding of hydrological system of
peatland is very important for peatland management.
The major components of peatland hydrology include the rain, evapotranspiration, soil moisture, groundwater, confined groundwater, and river/sea water. Rain is
the most important component for the formation of tropical peatland. Even in the
tropical wetland areas, the amount of monthly rainfall has seasonal changes in the
dry and wet seasons because of the effect of seasonal changes of the Intertropical
Convergence Zone (ITCZ). The drought level and length in the dry season are
strongly affected by El Niño events (Putra and Hayasaka 2011; Osaki et al.
2016a, b).
The peatland ecosystem is roughly divided into three portions, namely biosphere,
vertical geosphere, and horizontal geosphere (Fig. 19.1). The behavior of water and
material transfer in the peatland ecosystem of each portion is separately described
after the chapter.
19.2 Hydrology in the Biosphere
Rainfall role in the biosphere is divided into three elements as follows:
1. Interception, most of the water in the tropical peat swamp forest is supplied by
rainfall. In fact, some raindrops are caught by leaves and branches in the crown
and evaporate directly to atmosphere.
2. Stemflow, some raindrops reach the ground through the surface of tree trunks.
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H. Takahashi et al.
Water is the most important environmental component for peatland formation and
ecosystem not only in tropical but also in temperate and boreal zones. Vegetation in
peatland grows using water from sky (rain) and upstream of peatland.
Peatland is generally formed in the flat land under wet climate with higher
precipitation and distributed in the world, except Antarctica. Hydrological aspects
of peatland differ between climate, topography, and vegetation.
Tropical peatland develops mainly behind coastal mangrove swamp and extended
to inland under swamp forest (Rieley and Page 1990). Peat is formed from the
decaying organic materials which originated from root, leaf, and trunk growing in
the peat. The main matrix of peat is originated in grass and sphagnum species in the
boreal peatland, but is mainly originated in woody plant species in the tropical
peatland.
Rain is the major water resource in the central area of tropical peatland, where the
oligotrophic peat develops. In the marginal area of the peatland, the major water is
supplied from the (1) rain, (2) outflow from the center of peatland, and (3) river/sea
with minerals/saline materials. The hydrology in the peatland is characterized by the
physical, chemical, and biological characters, which develop with the balance of the
vegetation in the peat and water supplied by the rain and river/sea; therefore,
peatland is very fragile one. Thus, a good understanding of hydrological system of
peatland is very important for peatland management.
The major components of peatland hydrology include the rain, evapotranspiration, soil moisture, groundwater, confined groundwater, and river/sea water. Rain is
the most important component for the formation of tropical peatland. Even in the
tropical wetland areas, the amount of monthly rainfall has seasonal changes in the
dry and wet seasons because of the effect of seasonal changes of the Intertropical
Convergence Zone (ITCZ). The drought level and length in the dry season are
strongly affected by El Niño events (Putra and Hayasaka 2011; Osaki et al.
2016a, b).
The peatland ecosystem is roughly divided into three portions, namely biosphere,
vertical geosphere, and horizontal geosphere (Fig. 19.1). The behavior of water and
material transfer in the peatland ecosystem of each portion is separately described
after the chapter.
19.2 Hydrology in the Biosphere
Rainfall role in the biosphere is divided into three elements as follows:
1. Interception, most of the water in the tropical peat swamp forest is supplied by
rainfall. In fact, some raindrops are caught by leaves and branches in the crown
and evaporate directly to atmosphere.
2. Stemflow, some raindrops reach the ground through the surface of tree trunks.
538
H. Takahashi et al.