Abstract

CORREA DIAZ, Arian; GOMEZ GUERRERO, Armando  and  HORWATH, William R.. Inorganic Nitrogen uptake in Pinus hartwegii Lindl. stands at different altitudes and exposures. Rev. mex. de cienc. forestales [online]. 2024, vol.15, n.86, pp.101-122.  Epub Mar 03, 2025. ISSN 2007-1132.  https://doi.org/10.29298/rmcf.v15i86.1447.

To understand the N cycle in Pinus hartwegii ecosystems, it is important to investigate the movement of this element in these forests to propose forest management strategies based on knowledge of biogeochemical processes. This paper shows results of an experiment with young Pinus harwtegii trees to study the uptake of two N forms, ammonium and nitrate. N uptake was measured using 15N sources of ammonium sulfate and potassium nitrate, with enrichments of 49.2 and 56.7%, respectively. The variation factors included two elevation levels (3 500 and 3 900 m) and two slope aspects (Northwest and Southwest), composing a 23 factorial experiment. In addition, surface soil N mineralization (10 cm) was evaluated over a year in the same sites. Results indicate that the percentage of Nitrogen derived from the labeled source (NDDF) in foliage was higher in the Southwest exposure. However, the net mass recovery of 15N was higher in the Northwest sites (P<0.05), due to higher foliar mass in this aspect. Nitrate uptake exceeded ammonium uptake by 63 % (P<0.05). The mineralization of soil nitrogen, in relation to altitude and aspects, did not schow a defined trend. P. hartwegii adapts to seasonal conditions for the acquisition of both forms of nitrogen, allowing it to colonize adverse high-mountain sites. P. hartwegii stands at low elevations (3 500 m) and with Southwestern exposure are more susceptible to alterations in the N cycle.

Keywords : Nitrogen absorption; high mountain forests; Nitrogen forms; Nitrogen mineralization; topography; use of ¹⁵N.

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