Predicting height growth of sugar pine regeneration using stand and individual tree characteristics

Abstract

Concern exists among managers and researchers that sugar pine (Pinus lambertiana), a valuable, moderately shade-tolerant timber species, regeneration appears to be declining. Management and restoration require understanding factors leading to sustained sugar pine regeneration growth and overstorey recruitment. The primary research objective was to identify factors influencing sugar pine regeneration height growth. Data were collected on sugar pine regeneration, including height growth and stand characteristics across six managed and eight unmanaged stands in the Lake Tahoe Basin, CA and NV, USA. Individual tree- and stand-level analyses were conducted using non-parametric statistical comparisons and regression. Results indicated low mean height growth rates and no relationship between canopy closure and either height growth or management history. Individual sugar pine seedlings grew significantly taller under unmanaged stand conditions with higher canopy closures while sapling growth did not differ statistically by management history. Individual tree-level height growth models never explained more than 35 per cent of the variation. Stand-level models explained over 50 per cent of the variation with fewer variables than the individual tree-level models. More research should be conducted to determine whether the regeneration that is persisting in the understorey would respond positively to more aggressive uneven-aged silvicultural treatments designed for enhancing understorey pine growth. © 2013 Institute of Chartered Foresters, All rights reserved.