Soil responses to management, increased precipitation, and added nitrogen in ponderosa pine forests

Bruce A Hungate, Stephen C. Hart, Paul C. Selmants, Sarah I. Boyle, Catherine A Gehring

Research output: Contribution to journalArticle

20 Citations (Scopus)

Abstract

Forest management, climatic change, and atmospheric N deposition can affect soil biogeochemistry, but their combined effects are not well understood. We examined the effects of water and N amendments and forest thinning and burning on soil N pools and fluxes in ponderosa pine forests near Flagstaff, Arizona (USA). Using a 15N-depleted fertilizer, we also documented the distribution of added N into soil N pools. Because thinning and burning can increase soil water content and N availability, we hypothesized that these changes would alleviate water and N limitation of soil processes, causing smaller responses to added N and water in the restored stand. We found little support for this hypothesis. Responses of fine root biomass, potential net N mineralization, and the soil microbial N to water and N amendments were mostly unaffected by stand management. Most of the soil processes we examined were limited by N and water, and the increased N and soil water availability caused by forest restoration was insufficient to alleviate these limitations. For example, N addition caused a larger increase in potential net nitrification in the restored stand, and at a given level of soil N availability, N addition had a larger effect on soil microbial N in the restored stand. Possibly, forest restoration increased the availability of some other limiting resource, amplifying responses to added N and water. Tracer N recoveries in roots and in the forest floor were lower in the restored stand. Natural abundance δ15N of labile soil N pools were higher in the restored stand, consistent with a more open N cycle. We conclude that thinning and burning open up the N cycle, at least in the short term, and that these changes are amplified by enhanced precipitation and N additions. Our results suggest that thinning and burning in ponderosa pine forests will not increase their resistance to changes in soil N dynamics resulting from increased atmospheric N deposition or increased precipitation due to climatic change. Restoration plans should consider the potential impact on long-term forest productivity of greater Nlosses from a more open N cycle, especially during the period immediately after thinning and burning.

Original languageEnglish (US)
Pages (from-to)1352-1365
Number of pages14
JournalEcological Applications
Volume17
Issue number5
DOIs
StatePublished - Jul 2007

Fingerprint

nitrogen
thinning
soil
water
soil water
climate change
fine root
biogeochemistry
forest floor
water availability
forest management
nitrification
tracer
water content
fertilizer
mineralization
productivity
biomass
resource
restoration

Keywords

  • δ N
  • Climatic change
  • Forest restoration
  • Microbial biomass
  • N isotope tracer
  • Nitrification
  • Nitrogen fertilization
  • Nitrogen mineralization
  • Precipitation

ASJC Scopus subject areas

  • Ecology

Cite this

Soil responses to management, increased precipitation, and added nitrogen in ponderosa pine forests. / Hungate, Bruce A; Hart, Stephen C.; Selmants, Paul C.; Boyle, Sarah I.; Gehring, Catherine A.

In: Ecological Applications, Vol. 17, No. 5, 07.2007, p. 1352-1365.

Research output: Contribution to journalArticle

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