Agriculture Reference
In-Depth Information
loss, especially by volatilization of NH
3
from the floodwater, and how well the
decomposition matches the dynamics of plant growth. Recoveries seldom exceed
60% of the N and may be less than 25%.
5.2.5 FAUNA
Table 5.4 lists invertebrates commonly found in the soil and floodwater of differ-
ent wetland types. Insect larvae, molluscs and, particularly, oligochaete worms
of the order Tubificidae are abundant on and in the soil surface. Table 5.5 lists
invertebrates common in ricefields. In a survey of 32 ricefields in the Philippines,
Simpson
et al
. (1993a) found that oligochaetes were the only macro-invertebrates
present in significant numbers in all the fields. The dominant species were
Limnodrilus hoffmeisteri
(81% of the population on average) and
Branchiura
sowerbyi
(13%). Their distribution within fields was contagious and ranged from
0 to 35 000m
−
2
, averages 5000 to 10 000m
−
2
. The fresh weight ranged from 0 to
630 kg ha
−
1
. The average population at a site was positively correlated with soil
Table 5.4
Invertebrates commonly found in the soil and floodwater of different types
of wetland
Meiofauna
(63-500
µ
m diameter)
Macrofauna
(
>
500
µ
m diameter)
Freshwater
Marsh/fen
Amphipods, copepods
Chironomid insect larvae,
gastropods, isopods
Swamp forest
Deepwater
Nematodes, amphipods,
copepods, oligochaetes
Crayfish, clams, oligochaetes,
gastropods, isopods, midge
larvae
Alluvial
Nematodes, oligochaetes,
'terrestrial' invertebrates
(mitesacari, springtails-
collembola)
Oligochaetes including
earthworms, crayfish
Estuarine
Tidal marsh
Freshwater
Nematodes, amphipods,
oligochaetes
Oligochaetes, polychaetes, midge
larvae
Brackish
Nematodes, amphipods,
oligochaetes
Oligochaetes, fiddler crabs, snails,
mussels
Salt
Nematodes, amphipods,
oligochaetes
Oligochaetes, fiddler crabs, mud
crabs, periwinkles, snails,
mussels, oysters, clams
Mangrove forest
Nematodes, amphipods,
copepods, oligochaetes,
polychaetes
Fiddler crabs, oysters, barnacles
Source
: adapted from Craft (2001). Reproduced by permission of Lewis Publishers.
