Agroforestation of Grasslands in Southeast Asia: WaNuLCAS Model Scenarios for Shade-Based Imperata Control During Tree Establishment - Smallholder Tree Growing for Rural Development and Environmental Services - page 145

Table 6.4 Length of time available for food crops and Imperata regrowth (stage A and B, respec-
tively, in Fig. 6.1) and the stem basal area needed to reduce light at crop level to 50 percent and
at Imperata level to 15 percent as transition points for phase A and B (the measurements refer to
Purnomosidhi et al. 2005)
Tree species S = simula-

tion, M =
measure-
ment

Weeding Tree

spacing

Basal area
(m 2 ha −1 ) at

Time (years)

50% light
at Imperata
level

15% light
at Imperata
level

A B A + B

Acacia
mangium

S No weeding Narrow a - -

Wide b - -

Partial weeding Narrow 0.6 13 0.9 1.9 2.8

M Wide 0.7 10.6 1.4 2.2 3.6

- Narrow 2.1 10

Paraserianthes
falcataria

S No weeding Narrow 2.9 15.4 2.3 2.5 4.8

Wide 2 11 5.4 3.7 9.1

Partial weeding Narrow 1 12.1 0.7 2.0 2.7

Wide 1.7 9.4 1.9 3.2 5.1

M - Narrow 3.7 16.9

Hevea brasil-
iensis

S No weeding Narrow - -

Wide - -

Partial weeding Narrow 1.1 6.4 2.8 3.1 5.9

Wide 0.8 5.9 4.2 4.7 8.9

M - Narrow 2.1 8.4

Swietenia
macrophylla

S No weeding Narrow - -

Wide - -

Partial weeding Narrow 1.4 10.5 2.4 4.2 6.4

Wide 1.6 23.7 4.1 >10 >15

a narrow (timber trees: 4 × 2, 3 × 3, 4 × 4 m; rubber: 6 × 3, 5 × 3, 4 × 4 m)
b wide spacing (timber trees: 8 × 4, 8 × 8 m; rubber: 6 × 6, 12 × 6 m)

Fig. 6.8 Relationship between predicted length of the Imperata regrowth window (Phase B) in
relation to the predicted length of initial cropping period (Phase A, as in Fig. 6.1), across different
tree species, planting patterns and weeding regimes (data in Table 6.4)