Elemental Ratios in Foliage and Soil of a Jeffrey Pine Stand Subjected to Thinning and Burning Restoration Practices

Abstract

Forest thinnings accomplished through cut-to-length and whole-tree harvesting followed by a prescribed underburn were assessed for their influences on mineral nutrition in eastern Sierran Jeffrey pine (Pinus jeffreyi Grev. & Balf.). As derived from foliar elemental concentrations determined at six samplings distributed over three growing seasons, molar Ca/Al, Mg/Al, K/Al, Ca/Mn, Mg/Mn, and K/Mn were generally higher in the unthinned treatment and lower in burned stand portions. Conducted under drought conditions, the driest phase of the study resulted in lower Ca/Al, Mg/Al, and K/Al and higher Ca/Mn and Ca/Zn when averaged across treatments. Foliar K/Mn, K/Zn, and K/Cu were generally lower in the early portion of the growing season compared to the late portion. At mid growing season, Mg/Al, K/Al, Mg/Mn, K/Mn, K/Fe, K/Zn, and K/Cu were higher in young needles while Ca/Al, Ca/Fe, Mg/Fe, Ca/Zn, Ca/Cu, and Mg/Cu were so in older ones. At mid study, soil Ca/Fe was higher in the unthinned treatment generally and especially in its unburned portion while K/Cu was higher overall in burned stand portions, most especially in the unthinned treatment. These findings provide insight into the interrelationships of base cations and metallic elements in forest nutrition as influenced by restoration practices.