Category: Ecological Research
Title: Nitrogen and phosphorus status in a ponderosa pine forest after 20 years of interval burning
Author: Wright, R.J. , Hart, S.C.
Subject: Nutrient cycling, Ponderosa pine (Pinus ponderosa), Prescribed burns, Soil
Abstract: We examined the cumulative effects of 20 years of two-year interval prescription burning on available nitrogen (N) and total N and phosphorus (P) pools in the upper 15 cm of mineral soil of a southwestern ponderosa pine (Pinus ponderosa Dougl. ex Laws.) forest over a complete two-year burn cycle. Repeated burning reduced anaerobically mineralizable N up to 25(percent). However, burned and control plots had similar monthly ammonium and nitrate pool sizes in the mineral soil during both years of the two-year bum cycle. Mineral soil total N in the upper 15 cm was reduced by 110 kg N/ha (about a 7(percent) reduction) after 20 years of prescription burning at this site. This estimate, coupled with a calculated 470 kg/ha loss of N from the forest floor, indicates repeated burning has substantially depleted soil N stocks at this site. In contrast to N, mineral soil total P in burned plots was similar to control plots. Our results suggest that repeated prescription burning at two-year intervals may have deleterious long-term effects on N cycling in southwestern ponderosa pine forests.