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Evaluación del imapacto de faenas forestales mecanizadas el suelo. Resultados de un ensayo.

Evaluación del imapacto de faenas forestales mecanizadas el suelo. Resultados de un ensayo.

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  • 1. The effect of mechanical site preparation on water and soil protection in radiata pine plantations in the Basque Country Nahia Gartzia Bengoetxea Inazio Mart ínez de Arano Ander Gonzalez Arias
  • 2. Goods and services provided by forest in relation to soil function • Maintain or restore productivity • Protect other ecosystem compartments - Carbon sequestration - water quality/quantity Sediment outputs • Preserve soil ecosystem integrity Starting Point
  • 3. Forest play an important role in the protective functions of soil and water quality • Forest cover disappears • Understory and litter removals • Soil disturbance (logging, traffic, site preparation) Main difference between (commercial) Plantations & other Forests is the Inter-Rotation period. Starting Point time gap between harvest and the crown closure of the next rotation (Mead 1990).
  • 4. Pinus radiata High slopes increase disturbance risk Starting Point Mechanized operations have increased Since 1980s Are common on slopes under 40% Physical damage linked to machinery use in harvest, logging and soil preparation operations is one of the key factors of forest soil sustainability (Constantini et al. 1997 Aust. For. 60/4 )
  • 5. Objective To describe the effect of commercial site preparation on productivity, soil properties and sediment exports. To evaluate sustainability and the production of goods and services in relation to soil & water conservation
  • 6. TRIAL DESIGN 4 site preparation industrial treatments Manual Scalping Ripping Discontinuous ripping 3 repetitions 3.3 ha 30% slope
  • 7. Soil depth before site preparation
  • 8. Soil chemical properties before site preparation
  • 9.
    • Manual (M): Clearing harvest residues and existing vegetation by hand; planting holes were also manually made
    • Scalping (S): Harvest residues and existing vegetation were cleared with the front blade of a bulldozer and planting holes were done by hand
    • (iii) Ripping (R): Harvest residues and vegetation was cleared as in the S treatment and afterwards a ripper that dug a 40-50 cm deep trench in the line of maximum slope was used to facilitate plantation that was also made by hand
    Site preparations:
  • 10. Manual Scalping Ripping
  • 11. before site preparation after site preparation
  • 12. Soil fertility : OM, total N, C/N, pH, Ca, Mg, K, CEC, P-Olsen Soil Organic Matter dynamics : In situ seasonal N mineralization over 1 year Tree growth evolution : All trees were measured twice per year from 2002 to 2005
  • 13. Soil Erosion : At all Plots, 1.4 m long, 40 cm deep and 40 cm wide ditch was established to monitor soil loss and sediments were recovered once per year. years yr 1-3 Soil Physics : Resistance to penetration, bulk density, saturated hydraulic conductivity, water holding capacity at -33 KPa and -1500 Kpa yr2-tr4 Water run-off : water volume (ml) was determined over 1 year in1 m 2 run-off plots yr-1
  • 14. RESULTS
  • 15. No difference in height between manual and ripping Scalping clearly behind in first 4 years 20% loss in productivity? * differences in diameter are non significant Productivity
  • 16. • 36% of soil carbon loss (1st year) • C/N shows top soil removal Soil Carbon 4 6 8 10 12 14 16 18 20 22 C/N subsolado roza al aire manual FORSEE Project Changes in aggregate size distribution may Produce long term changes in soil carbon dynamics 40 yr old radiata stand Adjacent mechanized 1 yr old stand
  • 17. Soil Chemistry Olsen P ppm • P is the most liming element in radiata pine plantations
  • 18. Soil Chemistry a b c a b c a b c a b a a b b a b b For all treatments, nutrient contents are not outside of normal radiata pine soils in the Basque Country
  • 19. In situ N mineralization. 1st year after soil preparation
  • 20. * Values are means with standard errors in parentheses. Within each column, significantly different treatment means based on one-way analysis of variance and Bonferroni/Dunn test are indicated by different lowercase letter Soil Physical Properties yr 1 • 20% increase in Bulk density • x 2.5 increase in soil penetration resistance (10 cm) • Reduction to 26%-12% in Hydraulic conductivity • 12%-15% loss in water holding capacity
  • 21. • Soil moisture at root depth (yr 1) is afected • ripping treatment maintains more moisture in summer a a b b ab b b a
  • 22. Runoff during year 1 Water collected after every significant rain event • x 3 increase in runoff on bladed • x 2 increase in runoff in ripped treatment
  • 23. Soil Erosion yr 1-3 * Soil loss in kg/ha at constant weight ripping scalping manual X 89 1.642 X 60 1.105 0.018 Management induced Mean erosion Tons yr -1 ha -1
  • 24. • 12%-26% increase in soil strength Soil Strength yr 4 a b
  • 25. Conclusions
  • 26. • Mechanized site preparation has produced a significative Removal of topsoil, organic matter and nutrients • Soil compactation and deterioration of hydraulic properties are limiting growth in the scalping treatment • Ripping has alleviated compactation and improved water availability in the dry season. • Deterioration of soil physical properties is severe and Shows no recovery in the sort term (4 years).
  • 27. • Sustained productivity cannot be the only criteria for Forest Soil sustainability Two treatments show similar productivity but they differ in: + x 80 sediment exports - x 2 in hydraulic conductivity - 35% in carbon stock - 15% in Water holding capacity - 20% in bulk density • Genetically improved material and proper fertilization Could mask observed differences in subsequent rotations • Relevant in the long term? • Relevant at the land scape?
  • 28. One treatment minimizes soil disturbance, produces very low Sediment exports, maintains carbon stocks with no penalty in productivity. The good news ! Also it must be considered that there soil treatment is no homegeneous.
  • 29.  
  • 30. Finally , Plantation Forestry may provide good and services in relation to soil, carbon and water conservation, but it may not. Management at the interotation period is critical in this respect