Updates on our understanding of the impacts of land use and farming practices on biophysical outcomes in the tropical uplands of Mindanao, the Philippines. D.J. Midmore 1, A. Dano 2, T.M. Nissen 3, D.D. Poudel 4 and G. Zhu 1.

Objectives: to link plot and water-shed level data on erosion, land management, C sequestration and water quality. Major drawbacks: erosion data from 1 research location at 1 slope (c. 42%) and 12 farmer sites 20-62%, tree data from 3 locations all >1000 m asl TSS measured monthly and few one-off pesticide data sets at plot and stream level. No account for non-agricultural sources of erosion.

Approach (1) using Present data on land use at catchment scale (1994, 2002) Erosion mitigation at plot level Tree biomass Potential and actual farm incomes Adjacent stream water quality Quantify adoption of new practices Try to link together through models

Approach (2) Compare adjacent similar micro- watersheds with quantified land use and data-rich in water quality/quantity. Show obvious relationships between parameters. Scale up erosion, rainfall, flow, {evaporation/drainage?} pesticide, tree biomass. Watershed values for different land use scenarios

Land Use Forest29% Shrub/tree (buffer)10% Shrub/tree (other)7% Corn/vegetable35% Corn/cane14% Rivers/creeks3% Others2% Rainfall:c mm pa 1980:14,400 ha cropped – 50% “temporary”

Rainfall – Victory site

No relationship between TSS and monthly rainfall

Relationship between soil erosion and rainfall (same day)

Pic 23

Production technologies, crops and erosion over seven seasons (1995/8)

Slope effects on erosion

Agroforestry, liming and sunflower rotation – effects on erosion

Comparisons of crop yield (t/ha) with different tillage systems and lime treatments across project period ( )

Reduction in annual crop yield by tree intercrop

Comparison of competitiveness between tree species and annual crops 1 Nissen and Midmore, Current study, non-pruned, steeply sloping land.

Tree DBH, intercropped for five seasons

Comparisons of crop yield (t/ha) with different tillage systems and lime treatments across project period ( )

Comparison of soil chemical properties (0-15 cm) with different cropping systems (May 2001)

Infiltration rates according to liming and sunflower rotation

Stand basal area as affected by planting population and thinning

Analysis of variance of tree DBH, stand basal area and survival rate by three factorial treatments at Minas site (data collected in May 1999)

Analysis of variance of tree DBH, stand basal area and survival rate by three factorial treatments at Minas site (data collected December 2000)

Analysis of variance of tree DBH, stand basal area and survival rate by three factorial treatments at Minas site (data collected June 2002)

Analysis of variance of harvested board-foot by three factorial treatments at Minas site (data collected July 2003)

Relationship between harvest board foot and tree volume (per tree basis)

Average dry weights (kg) and root:shoot ratios for five-year Eucalyptus torreliana trees. 1Actual ratio 2Calculated according to Enquist and Niklas (2002) based upon above ground biomass.

Chemical analysis of Eucalyptus torrelliana (above and below ground) from Lantapan, Bukidnon.

Some conclusions: Quite marked differences for erosion rates due to crop management practices Need to incorporate into model scenarios Tree canopy cover not so good at erosion control, needs ground contact of understorey vegetation Early differences in tree population do not result in different harvestable timber, choosing best trees improves SBA at harvest Actual C sequestration above and below ground in line with model predictions Much data still to collate, share, incorporate, utilise for rounding off research activity. Thanks to all for past and future cooperation