La Selva Researcher Publishes Article
Rapidly growing tropical trees mobilize remarkable amounts of nitrogen, in ways that differ surprisingly among speciesAnn E. Russell (a,1,2) and James W. Raich (b,1)
a - Department of Natural Resource Ecology and Management and b - Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA 50011
Edited* by Peter M. Vitousek, Stanford University, Stanford, CA, and approved May 16, 2012 (received for review March 13, 2012)
Abstract:Fast-growing forests, such as tropical secondary forests, can accumulate large amounts of carbon (C), and, thereby, play an
important role in the atmospheric CO2 balance. Because nitrogen
(N) cycling is inextricably linked with C cycling, the question
becomes: Where does the N come from to match high rates of C
accumulation? In unique experimental 16-y-old plantations established
in abandoned pasture in lowland Costa Rica, we used a mass-balance approach to quantify N accumulation in vegetation, identify sources of N, and evaluate differences among tree species in N cycling. The replicated design contained four broadleaved evergreen tree species growing under similar environmental conditions. Nitrogen uptake was rapid, reaching 409 (±30) kg·ha−1·y−1, double the rate reported from a Puerto Rican forest and greater than four times that observed at Hubbard Brook Forest (New Hampshire, USA). Nitrogen amassed in vegetation was 874 (±176) kg·ha−1, whereas net losses of soil N (0-100 cm) varied from 217 (±146) to 3,354 (±915) kg·ha−1 (P = 0.018) over 16 y. Soil C:N, δ13C values, and N budgets indicated that soil was the main source of biomass N. In Vochysia guatemalensis, however, N fixation contributed >60 kg·ha−1·y−1. All species apparently promoted soil N turnover, such that the soil N mean residence time was 32- 54 y, an order of magnitude lower than the global mean. High rates of N uptake were associated with substantial N losses in three of the species, in which an average of 1.6 g N was lost for every gram of N accumulated in biomass.
Save the date! This fall, OTS will be in New Orleans. Join us on October 19-21 for a wonderful weekend exploring the botanical side of the Big Easy! We promise a few evening and late night treats too. 
La Selva is in full swing now. Many researchers, graduate students, research assistants and courses are arriving daily. The staff at the station is working day and night while we await the onset of a real rainy season that seems to be slow in starting. It is a great time to be at La Selva!
In 2010, OTS was granted a Pan-American Advanced Studies Institutes (PASI) award, jointly supported by the NSF and the Department of Energy (DOE), to address the topic of expanding the frontier in tropical ecology through embedded sensors.
