Plant effects on soil N pools and dynamics in the Patagonian Monte, Argentina

CARRERA, AL; BERTILLER, MB; SAIN, CL; MAZZARINO, MJ

Durban (South Africa)

Congreso; International Rangeland Congress, Durban (South Africa); 2003

Nitrogen conservation in plants is associated with N-poor litter and low soil N. We hypothesized that perennial grasses with high N-resorption efficiency would induce lower soil N than evergreen shrubs with low N-resorption efficiency. We assessed N and C concentration in green and senesced leaves of grasses and shrubs and in associated soils, and calculated plant N resorption efficiency and the C/N ratio in senesced leaves.  In grasses, we found lower N concentration, higher C/N ratio in senesced leaves and higher N-resorption efficiency (3.57 mg.g-1, 135.93 and 83.68%, respectively) than in shrubs (10.16 mg.g-1, 43.06 and 34.18% respectively). Soil N varied significantly depending on the associated plant group (0.61 vs.0.54 mg.g-1, beneath shrubs and grasses, respectively) but N concentration of senesced leaves accounted only for the 3.1% of its variance. Organic C and the C/N ratio in soil did not vary in relation to plant groups. We concluded that (i) shrubs produce N-rich litter while grasses N-poor litter, due to low and high N-resorption efficiency, respectively, and (ii) these mechanisms are not highly related to soil N, indicating that factors other than litter quality account for the largest variation in soil N.