Agriculture Reference
In-Depth Information
3.2.2.3
Spatial distribution
Horizontal distribution
Initial impressions often suggest that surface litter is evenly distributed in many ecosys-
tems. However, interactions between wind, microtopography, gravity and the distribution
patterns of such entities as trees and efficient liner consumers like termites and white-rot
fungi lead to the formation of accumulation and depletion zones in which decomposition
processes may proceed differently (see,
e.g.,
Garay, 1989; Hafidi, 1989).
As shown above for tropical forests, further spatial variability may result from
inter-specific differences in litter quality. This heterogeneity is likely to increase with
the number of species present and may therefore be lower in grasslands than in forests,
and in temperate or cold regions than in tropical regions.
Vertical distribution
In many forest environments, litter accumulates at the soil surface and forms relatively
compact layers of accumulated material in intimate contact with the underlying soil.
However, in certain grasslands the pattern may be quite different with dead leaves some-
times remaining attached to the plant for long periods leading to the formation of a more
diffuse 'duff' with poor soil contact.
Finally, in humid tropical environments, significant amounts of litter are intercepted
by ferns, orchids, Bromeliad and other epiphytes, large branches, or
Pandanus
and palm-
tree leaf axils. These form characteristic suspended liner systems with no soil contact
(Lavelle and Kohlmann, 1984).
3.2.2.4
Annual inputs and standing crop
As with primary production, leaf litter production is determined by a suite of hierar-
chically-organised factors. Climate is the predominating influence and is expressed
through temperature and rainfall conditions (Figure I.43). Meentemeyer
et al.
(1982)
used the close relationship between litter production and actual evapo-transpiration to
estimate world total fine linerfall (excluding large wood) and leaf litterfall production.
