1 research outputs found
Stream carbon and nitrogen supplements during leaf litter decomposition: contrasting patterns for two foundation species
11 páginas, 3 figuras, 2 tablasLeaf litter decomposition plays a major role
in nutrient dynamics in forested streams. The chemical
composition of litter affects its processing by microorganisms,
which obtain nutrients from litter and from the water
column. The balance of these fluxes is not well known,
because they occur simultaneously and thus are difficult
to quantify separately. Here, we examined C and N flow
from streamwater and leaf litter to microbial biofilms during
decomposition. We used isotopically enriched leaves
(13C and 15N) from two riparian foundation tree species:
fast-decomposing Populus fremontii and slow-decomposing
Populus angustifolia, which differed in their concentration
of recalcitrant compounds. We adapted the isotope
pool dilution method to estimate gross elemental fluxes
into litter microbes. Three key findings emerged: litter type
strongly affected biomass and stoichiometry of microbial
assemblages growing on litter; the proportion of C and
N in microorganisms derived from the streamwater, as opposed to the litter, did not differ between litter types, but
increased throughout decomposition; gross immobilization
of N from the streamwater was higher for P. fremontii compared
to P. angustifolia, probably as a consequence of the
higher microbial biomass on P. fremontii. In contrast, gross
immobilization of C from the streamwater was higher for P.
angustifolia, suggesting that dissolved organic C in streamwater
was used as an additional energy source by microbial
assemblages growing on slow-decomposing litter. These
results indicate that biofilms on decomposing litter have
specific element requirements driven by litter characteristics,
which might have implications for whole-stream nutrient
retention.The National Science
Foundation provided funding through the Frontiers in Integrative
Biological Research (DEB-0425908), Integrative Graduate Education
and Research Traineeship (DGE-0549505), and Ecosystem Studies
(DEB-1120343) research programs. Funding was also provided by the
MED-FORESTSTREAMS (CGL2011-30590-C02-01) project. A. P.
was supported by a Formación de Personal Investigador Ph.D. fellowship
from the Spanish Ministry of Science and Innovation within the
context of ISONEF (CGL2008-05504-C02-01).Peer reviewe