Carbon, Nutrient, Light Interception and Soil Water Dynamics of Secondary Forests and Agroforestry Systems on Degraded Pastures
Steven
A.
Welch, Dept. Crop and Soil Sciences, Cornell University, Ithaca, NY 14853 USA, saw16@cornell.edu
(Presenting)
Karen
A.
McAffery, Dept. Crop and Soil Sciences, Cornell University, Ithaca, NY 14853 USA, kam26@cornell.edu
Erick
C.M.
Fernandes, Dept. Crop and Soil Sciences, Cornell University, Ithaca, NY 14853 USA, ecf3@cornell.edu
Susan
J.
Riha, Dept. Earth and Atmospheric Sciences, Cornell University, Ithaca, NY 14853 USA, sjr4@cornell.edu
Elisa
Wandelli, Embrapa-Amazonia Occidental, Manaus, Amazonas, Brazil, elisa@cpaa.embrapa.br
In the Brazilian Amazon, primary forest and degraded pastures represent polar extremes of carbon stocks, nutrient cycling, light interception, and deep soil water cycling. Plant succession on degraded pastures is expected to change these values, and the extent to which secondary forest (SF) restores these processes is a high priority research objective. This research quantifies Carbon (C) and nutrient stocks and accrual rates of 4 post-pasture landuses (LU) including 9 yr old SF and 3 agroforestry systems (AFS). All LU had carbon and nutrient stocks greater than values for recently abandoned pastures, but far less than nearby primary forest. Greatest C stocks were sequestered in aboveground biomass by SF (53.8 Mg C/ha) followed by the Palm AFS (41.7), Fruit AFS (34.3), and timber pasture (16). Light interception and soil water dynamics were monitored on these LU and on two additional SF of different ages (6- and 12-yr) and on traditional grazed pasture (GP). Light interception by SF of all ages (LAI 3.3) exceeded all other LU: Palm AFS (3), Fruit AFS (2.7), TP (2.5) and GP (2.2). Soil water content (SWC) dynamics follow the same trend as LAI with deepest SWC depletion by SF, followed by Palm, Fruit and TP AFS. SF 6-yr gained access to deeper SWC during the course of our study which corresponded with the closing of the upper canopy in this parcel. This suggests that in this environment, SF with closed upper canopies have a hydrology distinct from patchier tree canopies. This relationship might prove useful interpreting remotely sensed data.