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Photo: Antonin Kusbach. Improving longleaf pine mortality predictions in the Southern Variant of the Forest Vegetation Simulator. R. Justin DeRose 1 John D. Shaw 2 Giorgio Vacchiano 3 James N. Long 1 1 Utah State University, 2 Rocky Mountain Research Station,
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Photo: Antonin Kusbach Improving longleaf pine mortality predictions in the Southern Variant of the Forest Vegetation Simulator R. Justin DeRose 1 John D. Shaw 2 Giorgio Vacchiano 3 James N. Long 1 1 Utah State University, 2 Rocky Mountain Research Station, 3 Università di Torino
Outline • Size-density relationships • FVS-predicted mortality • Longleaf pine • Mortality in longleaf • Simulate natural mortality using FVS • Conclusions / Recommendations
Size-Density Relationships • Density management diagram • Trajectory through time
Phase 3 Phase 2 Phase 1 Mortality in SN variant 3 types… ρ = f(Dqx) • Background mortality • Density-dependent mortality, SDI > 55% & Dq < 10.0, x =1.6 • Density-dependent mortality, SDI > 55% Dq > 10.0, x = 2
MSB Shaw and Long, 2007, SJAF Longleaf pine DMD • Mature Stand Boundary (MSB) • LL range-wide dataset • Even-aged • Pure • ρ = f(Dqx) then, • Perhaps x > 2 Stand # 10001
MSB Red pine Shaw and Long, 2007, SJAF Mechanisms? • Increasing chance of density-independent mortality? • Less occupied growing space? • Zeide (1985), ‘self-intolerance’? • Assmann (1970) ‘crown disengagement’?
Ponderosa pine Douglas-fir MSB Dq Dq Dq Dq TPA TPA TPA TPA Aspen Utah juniper
Shaw and Long, 2007, SJAF Importance • Increasingly managing for large D trees • RCW (Shaw and Long, 2007, SJAF) (F & W Guidelines)
Simulate MSB • THIN… keyword every cycle? • Iteratively adjust BAMax / SDIMax? • Use MSB to constrain size-density relationship?
Results • Event Monitor, FixMort keyword • IF Dq approaches MSB THEN 10% mortality / cycle
Conclusions • FVS models background mortality fine at small diameters • Self-thinning mortality appears fine • BAMax mortality is unrealistic
Conclusions • We need a better approximation of natural mortality • We have a fix, albeit rough • Iterative FixMort simulates well but… • Must know MSB for your species
Dq Dq TPA TPA Recommendations • Replace BAMax mortality • Species-specific fitted relationships (like MSB)
Acknowledgements • Forestry Branch of the Fort Bragg Natural Resource Division • U.S. Army Environmental Center • P. Wefel and J. Stancar for their continuing support • D. Donnelly for early project support