No abstract

Undisturbed moist or dry soil slabs collected from beneath chaparral plants were burned at different intensities in the laboratory. Inorganic and organic nitrogen levels were measured before and after burning. An intense burn over dry soil slabs decreased KCl‐extractable NH4+‐N in the litter but increased it in the underlying soil. In contrast, NO3‐‐N was decreased in both soil and litter during an intense burn over dry soil. Little change in NO3‐‐ and NH4+‐N occurred when litter and soil were moist. About 67% of the total N in the litter and soil was lost during the intense burn over dry soil, but less than 25% was lost when the soil and litter were moist. Amino acids were particularly sensitive to heating and were almost destroyed in dry litter during the intense burn. Almost 75% of the hexosamines in the litter and soil were also destroyed by the intense burn over dry soil.

A survey was made in the United States to determine the extent of the infestations of leafy spurge (Euphorbia esula L.) and other weeds of economic importance in the Euphorbiaceae. From introductions about 100 yr ago, leafy spurge is now found in 458 counties in 26 states from coast to coast. The infestations are out of control in some states, and biological control is mentioned as a possible solution to the problem.

USDA Forest Service Gen. Tech. Rep. PSW-104. 1988 'Unless otherwise noted, available and unpublisheddata areon file in the SDEF archives at the Forest Fire Laboratory,4955 CanyonCrest Drive, Riverside, California 92507.

Undisturbed moist and dry soil slabs collected from beneath two species of chaparral plants were burned at varying intensities in the laboratory. Treatment by intense burning over dry soil destroyed 67% of the total N and produced large amounts of NH4+. Treatment by intense and moderate burning over moist soil slabs removed only 25% of the total N, and a large portion of the remaining organic N was quickly ammonified after the fire by reinvading heterotrophic bacteria and later by fungi. All three burning treatments resulted in high levels of NH4+ in the soil after the fire. Nitrosomonas group bacteria did not respond to these high levels of available NH4+, and the nitrification that occurred was attributed to heterotrophic nitrification.