Improving Productivity, Profitability and Sustainability of Degraded Grasslands Through Tree-Based Land Use Systems in the Philippines - Smallholder Tree Growing for Rural Development and Environmental Services - page 291

Annual soil erosion Cumulative soil erosion

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800

40

600

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400

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0 5 10 15 20

0 5 10 15 20

Ye ar

Year

IM P LUS FPLUS TIMP LUS

IM P LUS FPLUS TIMP LUS

TCLUS TCSFLUS TP LUS

TCLUS TCSFLUS TP LUS

Fig. 14.3 Predicted annual and cumulative soil erosion (t/ha) over time of alternative land use
systems, Claveria, Misamis Oriental, The Philippines

average soil loss observed from the IMPLUS and FPLUS systems. However,
land use systems with Imperata have relatively lower soil erosion than with the
FPLUS system. This may be due to some protection from topsoil loss afforded
in these systems because of the surface cover provided by the Imperata grass
throughout the period, since not all biomass in the model was consumed by the
grazing animals.
The cumulative soil loss under the FPLUS system in the 20th year of the
simulation period was about 953 t ha −1 compared to 241 t ha −1 under IMPLUS,
58 t ha −1 under TIMPLUS, 192 t ha −1 under TCLUS, 134 t ha −1 under TCSFLUS,
and 21 t ha −1 under the TPLUS systems (Appendix 3). The conversion of
Imperata grassland to tree-based land use systems reduced the rate of soil ero-
sion by between 20 percent and 91 percent. In contrast, the rate of soil loss
increased by 75 percent for land use change, from Imperata grassland to current
farmers practice of continuous maize cropping. The results strongly indicate
that tree-based land use systems were effective in minimizing soil erosion.
Incorporating timber species in any land use would help reduce soil erosion
even in the most erosive farming practice.

14.3.5.2 Changes in Biomass and Soil Carbon

The time-trajectory of above-ground biomass carbon and soil carbon are pre-
sented in Fig. 14.4. The predicted above-ground biomass carbon under tree-based
land use systems (TIMPLUS, TCLUS, TCSFLUS and TPLUS) increased and
accumulated during the growth period of timber trees (i.e., for the first nine years)
and then dropped to zero in the 10th year, which was a cut year or harvest time
of each rotation. Among the tree-based land use systems, the TPLUS system