Nitrogen Mineralization and Nitrification in Mineral Soils of Pinyon-Juniper Ecosystems1
- Jeffrey M. Klopatek2
The mineral soils in the interspaces and under canopy of three pinyon (Pinus edulis Engelm.)-juniper [Juniperus osteosperma (Torr.) Little] woodland communities were analyzed to determine their nutrient status and potential N mineralization and nitrification. A >400-yr-old ungrazed, a 300-yr-old grazed, and a 35-yr-old burned and grazed site were represented. Significant differences were noted in soil pH, texture, bulk density, total N, organic C, and NaHCO3 extractable P between the canopies and the respective interspaces of the mature sites. No differences were noted between the canopy soils of the ungrazed and grazed nature sites. The 35-yr-old canopy soils showed significantly less total N and organic C than the mature sites. Interspaces exhibited relatively few differences between sites. Both canopy and interspace soils exhibited linear rates of mineralization and nitrification over the 60-d incubation. On all sampling dates there were significant differences in mineralization and nitrification rates between the canopy and interspace soils. The proportion of total N mineralized was highest for the most disturbed (burned, grazed) canopy soils and lowest for the least disturbed (ungrazed). The results obtained indicate that nitrification is not inhibited in mature pinyon-juniper woodlands, but suggest that the rate of N mineralization and nitrification may be enhanced by disturbance.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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