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Title: Necromass production: studies in undisturbed and logged Amazon Forests


Date: 2008

Source: Ecological Applications, 18(4) :873–884

Publication Series: Miscellaneous Publication

Description: Necromass stocks account for up to 20% of carbon stored in tropical forests and have been estimated to be 14–19% of the annual aboveground carbon flux. Both stocks and fluxes of necromass are infrequently measured. In this study, we directly measured the production of fallen coarse necromass (>2 cm diameter) during 4.5 years using repeated surveys in undisturbed forest areas and in forests subjected to reduced-impact logging at the Tapajos National Forest, Belterra, Brazil(3.088 S, 54.948 W). We also measured fallen coarse necromass and standing dead stocks at two times during our study.The mean (SE) annual flux into the fallen coarse necromass pool in undisturbed forest of 6.7 (0.8) Mgha1yr1 was not significantly different from the flux under a reduced-impact logging of 8.5 (1.3) Mgha1yr1.With the assumption of steady state, the instantaneous decomposition constants for fallen necromass in undisturbed forests were 0.12 yr1 for large, 0.33 yr1 for medium, and 0.47 yr1 for small size classes. The mass weighted decomposition constant was 0.15 yr1 for all fallen coarse necromass. Standing dead wood had a residence time of 4.2 years, and ;0.9 Mgha1yr1 of this pool was respired annually to the atmosphere through decomposition. Coarse necromass decomposition at our study site accounted for 12% of total carbon remineralization, and total aboveground coarse necromass was 14% of the aboveground biomass. Use of mortality rates to calculate production of coarse necromass leads to an underestimation of coarse necromass production by 45%, suggesting that nonlethal disturbance such as branch fall contributes significantly to this flux. Coarse necromass production is an important component of the tropical forest carbon cycle that has been neglected in most previous studies or erroneously estimated.

Keywords: Amazon, coarse woody debris, dead wood, decay, decomposition, mortality, necromass, reduced-impact logging, standing dead, tropical forest.

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PALACE, MICHAEL; KELLER, MICHAEL; SILVA, HUDSON; 2008. Necromass production: studies in undisturbed and logged Amazon Forests. Ecological Applications, 18(4) :873–884


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