Deciduous conifers : High N deposition and O3 exposure effects on growth and biomass allocation in ponderosa pine

摘要: Ponderosa pines (Pinus ponderosa Dougl. ex. Laws) 21 to 60 yr old were used assess the relative importance of environmental stressors (O3, drought) versus an enhancer (N deposition) on foliar retention, components aboveground growth, and whole tree biomass allocation. Sites chosen across a well-described gradient in ozone exposure (40 80 ppb per h, 24 h basis, 6 month growing season) nitrogen deposition (5 40 kg ha-1 yr-1) San Bernardino Mountains east Los Angeles, California. A high level chlorotic mottle indicated O3 injury at sites closest pollution source, despite potential for mitigating effects N deposition. At least polluted site, was evenly distributed three five needle-age classes retained. most 95% found current year's growth. High combined shift allocation pine that deciduous with one overwintering needle age class. Based harvests, root lowest highest exposure, confirming previous chamber field studies. Aboveground growth responses high-pollution opposite those expected injury. Needle lateral branch elongation measures wood production increased increasing proximity source. An enhancement these attributes suggested dominated response exposure.