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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 Universit di Torino Photo: Antonin Kusbach

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Outline Size-density relationships FVS-predicted mortality Longleaf pine Mortality in longleaf Simulate natural mortality using FVS Conclusions / Recommendations

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Size-Density Relationships Density management diagram Trajectory through time

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Mortality in SN variant 3 types = f(Dq x ) 1.Background mortality 2.Density-dependent mortality, SDI > 55% & Dq < 10.0, x =1.6 3.Density-dependent mortality, SDI > 55% Dq > 10.0, x = 2 Phase 1 Phase 2 Phase 3

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Longleaf pine DMD Mature Stand Boundary (MSB) LL range-wide dataset Even-aged Pure = f(Dq x ) then, Perhaps x > 2 MSB Shaw and Long, 2007, SJAF Stand # 10001

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MSB Shaw and Long, 2007, SJAF Mechanisms? Increasing chance of density-independent mortality? Less occupied growing space? Zeide (1985), self- intolerance? Assmann (1970) crown disengagement? Red pine

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MSB Dq TPA Ponderosa pine Dq TPA Utah juniper Dq TPA Douglas-fir Dq TPA Aspen

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Shaw and Long, 2007, SJAF Importance Increasingly managing for large D trees RCW (Shaw and Long, 2007, SJAF) (F & W Guidelines)

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Simulate MSB 1.THIN keyword every cycle? 2.Iteratively adjust BAMax / SDIMax? 3.Use MSB to constrain size- density relationship?

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Results Event Monitor, FixMort keyword IF Dq approaches MSB THEN 10% mortality / cycle

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Results

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Conclusions FVS models background mortality fine at small diameters Self-thinning mortality appears fine BAMax mortality is unrealistic

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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

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Recommendations Replace BAMax mortality Species-specific fitted relationships (like MSB) Dq TPA Dq TPA

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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