Availability of Natural Forest Resources
It was found that the mean density of trees in paddy fields is
higher (14.3 trees/ha) in areas located close to natural forests
than in areas located far from forests (11.9 trees/ha) (Table 4).
The difference is highly significant (|p| B 0.01) according to
the Mann–Whitney U test. This difference may, at least in
part, reflect the fact that villagers living close to a forest can
easily collect timber and firewood there so have less need to
exploit the trees in their paddy fields, as was suggested by
Vityakon et al. (1996). However, the contrary observations by
Kosaka et al. (2006) that tree density in paddy fields in Laos
was much higher in a village without a nearby forest than it
was in a village with an adjacent forest suggest that other
factors in addition to mere physical proximity may be at work
in specific cases. In particular, the character of the forest
management regime and rules regulating exploitation of forest
resources might be expected to affect the extent to which
villagers are able to rely on forest trees as substitutes for their
own on-farm trees. For example, a detailed study in Bolivia
found that a strong package of common property forest
management practices provided the strongest incentives for
on-farm tree planting (Bluffstone et al. 2008). If laws protecting natural forests are only weakly enforced, as tends to be
the case in Northeastern Thailand, then villagers with ready
access to them are likely to exploit these common property
resources instead of cutting the trees on their own land. On the
other hand, in areas with more effective forest protection
systems, villagers will be forced to rely more heavily on the
trees growing on their own land. This can lead either to a
decrease in tree density if farmers over-exploit their tree
resources or to an increase in tree density if they begin to plant
more trees in their paddy fields to provide needed resources
that they can no longer obtain from natural forests.