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Nitrogen‐15 budget in model ecosystems of white clover and perennial ryegrass exposed for four years at elevated atmospheric pCO 2
Author(s) -
Hartwig Ueli A.,
Lüscher Andreas,
Nösberger Josef,
Van Kessel Chris
Publication year - 2002
Publication title -
global change biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.146
H-Index - 255
eISSN - 1365-2486
pISSN - 1354-1013
DOI - 10.1046/j.1354-1013.2001.00465.x
Subject(s) - lolium perenne , trifolium repens , perennial plant , repens , agronomy , nitrogen , biomass (ecology) , grassland , ecosystem , stolon , environmental science , chemistry , biology , ecology , organic chemistry
Although there are many indications that N cycling in grassland ecosystems changes under elevated atmospheric CO 2 partial pressure (pCO 2 ), most information has been obtained in short‐term studies. Thus, N budgets were established for four years under ambient and 60 Pa pCO 2 at two levels of N fertilization in two contrasting model ecosystems: Trifolium repens L. (white clover) and Lolium perenne L. (perennial ryegrass) were planted in soil in boxes in the Swiss FACE experiment. While T. repens showed an 80% increase in harvested biomass with no change in biomass allocation under elevated atmospheric pCO 2 compared to ambient conditions, L. perenne showed an increase only in the biomass of the roots. During the four years of the experiment, the systems gained N both from N retained in the soil and from stubble/stolon and roots left after the final harvest; in total between 11 and 86 gN m −2 . Nitrogen retention in the soil was between 4 and 64 g m 2 . The L. perenne system gained the most N and retained the most N in the soil at high N fertilization and elevated atmospheric pCO 2 . The input of new C and N into the soil correlated well in the L. perenne systems but not in the T. repens systems. Elevated atmospheric pCO 2 led neither to an increase in N retention in the soil nor did it reduce the loss of N from the soil. In the L. perenne systems, N fertilization played the main role in both the retention of N and the sequestration of C, while in the T. repens systems symbiotic N 2 fixation may have controlled N retention in the soil.