Updates on our understanding of the impacts of land use and farming practices on biophysical outcome

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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. Midmore1, A. Dano2, T.M. Nissen3, D.D.
  Poudel4 and G. Zhu1.

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• 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 gt1000 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.

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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

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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

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Land Use 1994 2002

• Forest 29
• Shrub/tree (buffer) 10
• Shrub/tree (other) 7
• Corn/vegetable 35
• Corn/cane 14
• Rivers/creeks 3
• Others 2
• Rainfall c. 2500 mm pa
• 1980 14,400 ha cropped 50 temporary

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Rainfall Victory site 1998-2002
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No relationship between TSS and monthly rainfall
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Relationship between soil erosion and rainfall
(same day)
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Pic 23
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Production technologies, crops and erosion over
seven seasons (1995/8)
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Slope effects on erosion
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Agroforestry, liming and sunflower rotation
effects on erosion
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Comparisons of crop yield (t/ha) with different
tillage systems and lime treatments across
project period (1998-2002)
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Reduction in annual crop yield by tree intercrop
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Comparison of competitiveness between tree
species and annual crops
1Nissen and Midmore, 2002 2Current study,
non-pruned, steeply sloping land.
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Tree DBH, intercropped for five seasons
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Comparisons of crop yield (t/ha) with different
tillage systems and lime treatments across
project period (1998-2002)
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Comparison of soil chemical properties (0-15 cm)
with different cropping systems (May 2001)
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Infiltration rates according to liming and
sunflower rotation
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Stand basal area as affected by planting
population and thinning
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Analysis of variance of tree DBH, stand basal
area and survival rate by three factorial
treatments at Minas site (data collected in May
1999)


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Analysis of variance of tree DBH, stand basal
area and survival rate by three factorial
treatments at Minas site (data collected December
2000)
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Analysis of variance of tree DBH, stand basal
area and survival rate by three factorial
treatments at Minas site (data collected June
2002)
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Analysis of variance of harvested board-foot by
three factorial treatments at Minas site (data
collected July 2003)
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Relationship between harvest board foot and tree
volume (per tree basis)
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Average dry weights (kg) and rootshoot ratios
for five-year Eucalyptus torreliana trees.

• Actual ratio
• Calculated according to Enquist and Niklas (2002)
  based upon above ground biomass.

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

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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