Seasonal trends of Amazonian rainforest phenology, net primary productivity, and carbon allocation. Issue 5 (14th May 2016)

• Record Type: Journal Article
• Authors: Girardin, Cécile A. J.; Malhi, Yadvinder; Doughty, Christopher E.; Metcalfe, Daniel B.; Meir, Patrick; del Aguila‐Pasquel, Jhon; Araujo‐Murakami, Alejandro; da Costa, Antonio C. L.; Silva‐Espejo, Javier E.; Farfán Amézquita, Filio; Rowland, Lucy
• Is Part Of: Global biogeochemical cycles. Volume 30:Issue 5(2016:May)
• Page Start: 700
• Page End: 715
• Publication Date: 2016-05-14
• Subjects: seasonality -- net primary productivity -- phenology -- carbon allocation -- tropical forests -- ecosystem function; Biogeochemical cycles -- Periodicals; Electronic journals; 577.1405
• DOI: 10.1002/2015GB005270
• Languages: English
• ISSNs: 0886-6236

Abstract

Abstract: The seasonality of solar irradiance and precipitation may regulate seasonal variations in tropical forests carbon cycling. Controversy remains over their importance as drivers of seasonal dynamics of net primary productivity in tropical forests. We use ground data from nine lowland Amazonian forest plots collected over 3 years to quantify the monthly primary productivity ( NPP ) of leaves, reproductive material, woody material, and fine roots over an annual cycle. We distinguish between forests that do not experience substantial seasonal moisture stress ("humid sites") and forests that experience a stronger dry season ("dry sites"). We find that forests from both precipitation regimes maximize leaf NPP over the drier season, with a peak in production in August at both humid (mean 0.39 ± 0.03 Mg C ha −1 month −1 in July, n = 4) and dry sites (mean 0.49 ± 0.03 Mg C ha −1 month −1 in September, n = 8). We identify two distinct seasonal carbon allocation patterns (the allocation of NPP to a specific organ such as wood leaves or fine roots divided by total NPP ). The forests monitored in the present study show evidence of either (i) constant allocation to roots and a seasonal trade‐off between leaf and woody material or (ii) constant allocation to wood and a seasonal trade‐off between roots and leaves. Finally, we find strong evidence of synchronized flowering at the end of the dry season in both precipitation regimes. Flower production reaches a maximum of 0.047 ± 0.013 and 0.031 ± 0.004 Mg C ha −1 month −1 in November, in humid and dry sites, respectively. Fruitfall production was staggered throughout the year, probably reflecting the high variation in varying times to development and loss of fruit among species. Key Points: Field data confirm that Amazon forests maximize leaf production during dry season Trade‐offs in carbon allocation determine seasonality of NPP components Consistent reproductive seasonality across contrasting precipitation regimes