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Tropical pasture carbon cycling: relationships between C source/sink strength, above‐ground biomass and grazing
Author(s) -
Wilsey Brian J.,
Parent Gabrielle,
Roulet Nigel T.,
Moore Tim R.,
Potvin Catherine
Publication year - 2002
Publication title -
ecology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.852
H-Index - 265
eISSN - 1461-0248
pISSN - 1461-023X
DOI - 10.1046/j.1461-0248.2002.00322.x
Subject(s) - grazing , pasture , ecosystem , biomass (ecology) , environmental science , standing crop , ecosystem respiration , agronomy , cycling , canopy , carbon sink , carbon cycle , productivity , sink (geography) , ecology , zoology , biology , primary production , forestry , geography , cartography , macroeconomics , economics
Abstract We measured net ecosystem CO 2 exchange (NEE) in Panamá over C 4 pasture plots that varied in grazing intensity. After adjusting for variation in light, there were noticeable effects of grazing‐related variables on CO 2 exchange that were largely dependent on the developmental stage of the plant canopy. Above‐ground productivity was positively related to grazing intensity ( r 2 =0.30). Two experimentally grazed fields had significantly lower standing crop biomass but no significant difference in CO 2 uptake (24.2 μmol/m 2 /s) compared with two ungrazed fields (20.3 μmol/m 2 /s). Grazed fields had significantly lower ecosystem respiration rates (10.3 μmol/m 2 /s) than did ungrazed fields (17.6 μmol/m 2 /s). These results suggest that, although these pastures were possible sources of CO 2 during the time intervals sampled, the size of the sources tended to be dampened by cattle grazing through reductions in ecosystem respiration. Thus, it appears that disturbance caused by cattle grazing will not always result in an increase in CO 2 release from tropical pastures to the atmosphere.