This document describes a sabbatical grant to study controls on plant-soil stoichiometry in dryland agroecosystems. The objectives are to 1) quantify how human management impacts plant and soil carbon, nitrogen, and phosphorus in cork oak savannas and 2) assess effects of woody plant encroachment and UV radiation on litter decomposition. Samples have been collected from sites in Portugal with different land uses and a two-year litter decomposition experiment was conducted measuring effects of litter type, location, and UV exposure.

1. Controls on the Plant-Soil Stoichiometry of Dryland Agroecosystems:
A Sabbatical Strengthening Grant (Grant #2013-67020-21354)
Rebecca L. McCulley, Dept. of Plant & Soil Sciences, Univ. of Kentucky, USA
Catarina Moura, Centre for Functional Ecology, Dept. of Life Sciences, Univ. of Coimbra, Coimbra, PT
Maria Caldeira, Centro de Estudos Florestais, Instituto Superior de Agronomia, Lisbon, PT
Obj. 1: Quantify how human management of cork oak savannas impacts plant and soil C:N:P
Figure 2. Conceptual diagram illustrating how human use
alters the ecosystem services of cork oak savanna (from
Bugalho et al. 2011). PES – payment for ecosystem services.
References:
• Bugalho, MN, MC Caldeira, JS Pereira, J Aronson, and JG Pausas. 2011.
Meditteranean cork oak savannas require human use to sustain biodiversity
and ecosystem services. Frontiers in Ecology & the Environment 9(5):278-
286.
• Parisi A.V., P. Schouten, N.J. Downs, J. Turner. 2010. Solar UV exposures
measured simultaneously to all arbitrarily oriented leaves on a plant. Journal
of Photochemistry and Photobiology B: Biology 99:87-92.
Obj. 2: Assess interactive effects of woody plant encroachment and ultraviolet
(UV) radiation on litter decomposition in cork oak savannas.
Acknowledgements:
Future Work - Obj. 3: Evaluate the ability of a process-based model to capture
the effects of these controlling parameters on dryland biogeochemical cycling.
Figure 3. Photos of Cistus ladanifer shrub encroachment (left) and
Sown Biodiverse Pasture (right) in central and eastern Portugal field
sites.
What has been achieved?
• Plant & soil samples from two sites in central and eastern Portugal with adjacent,
paired land uses have been sampled (Vila Viçosa – shrub encroachment and
Herdade Machoqueria do Grou – sown biodiverse pasture).
• Samples have been received in my lab and are in various stages of processing.
• We will obtain δ15N data on the plant and soil material associated with the sown
biodiverse pasture project – to assess N-fixation from the legumes.
HMG
VV
Contact:
rebecca.mcculley@uky.edu
What has been achieved?
• We have completed a 2-yr litter decomposition experiment
at Vila Viçosa, which included: 3 litter types (oak, Cistus,
herbaceous); 3 incubation locations (oak canopy, Cistus
invaded, and herbaceous); 2 UV treatments (full and no UV);
and 4 replicates.
• Samples are in various stages of processing.
• We also measured the UV environment of each location
using polyphenylene oxide films (Parisi et al. 2010).
Photos of litter decomposition plots,
and a graph of estimated daily UV
doses measured in the three
incubation locations. The sun
illustrates the UV dose measured in
full sun conditions at the site.