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| The key role of tropical forest belowground carbon stocks and fluxes is well
recognised as one of the main components of the terrestrial ecosystem carbon cycle. This
study presents the first detailed investigation of spatial and temporal patterns of fine root
stocks and fluxes in tropical forests along an elevational gradient, ranging from the
Peruvian Andes (3020 m) to lowland Amazonia (194 m), with mean annual temperatures of
11.8C to 26.4 C and annual rainfall values of 1900 to 1560 mm yr-1, respectively.
Specifically, we analyse abiotic parameters controlling fine root dynamics, fine root growth
characteristics, and seasonality of net primary productivity along the elevation gradient. Root
and soil carbon stocks were measured by means of soil cores, and fine root productivity was
recorded using rhizotron chambers and ingrowth cores. We find that mean annual fine root
below ground net primary productivity in the montane forests (0–30 cm depth) ranged
between 4.270.56 Mg C ha-1 yr-1 (1855 m) and 1.720.87 Mg C ha-1 yr-1 (3020 m). These
values include a correction for finest roots (<0.6 mm diameter), which we suspect are under
sampled, resulting in an underestimation of fine roots by up to 31% in current ingrowth core
counting methods. We investigate the spatial and seasonal variation of fine root dynamics
using soil depth profiles and an analysis of seasonal amplitude along the elevation gradient.
We report a stronger seasonality of NPPFineRoot within the cloud immersion zone, most likely
synchronised to seasonality of solar radiation. Finally, we provide the first insights into root
growth characteristics along a tropical elevation transect: fine root area and fine root length
increase significantly in the montane cloud forest. These insights into belowground carbon
dynamics of tropical lowland and montane forests have significant implications for our
understanding of the global tropical forest carbon cycle. | |
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