This project uses manipulations of water and nitrogen input in nearby grassland and shrubland ecosystems to better understand the sensitivity of Southern California’s ecosystems to multiple environmental changes. The infrastructure is used to create three levels of water input: ambient, dry (-50%) and wet (+50%). The manipulations have been applied to the 8 grassland replicates since fall 2006 and the 8 coastal sage replicates since fall 2008. The first water year (2006-07) was extraordinary dry, 07-08 and 08-09 were drier than average, 09-10 and 10-11 were wetter than average, and 11-12, 12-13 and 13-14 were drier than average.

We monitor a large number of response variables, including the physical environment (temperature, soil water, etc) and biological response (species composition, production, etc). Several of these variables are measured with multiple complementary methods. For example, soil water is measured (1) in the upper 15 cm every two weeks by manual TDR at 384 locations, (2) in the upper 30 cm every 30 minutes by automated TDR at 96 locations, (3) along a vertical soil profile (5, 10, 25, 50, 100, 200 cm depth) every 30 minutes by thermal dissipation at 12 vertical profiles, and (4) along a soil profile at 30-cm intervals to 2-m depth every few weeks by manual neutron probe at 48 access tubes. Similarly, Vegetation Indices such as EVI and NDVI, which are well correlated with primary production, are measured manually at many locations with a spectroradiometer and continuously at a few locations using filtered photodiodes. The infrequent, manual observations have proven most useful for characterizing the treatments and spatial heterogeneity, while the automated, high frequency measurements have been especially useful for understanding physiological and physical processes.

Publications
Microbial abundance and composition influence litter decomposition response to environmental change Ecology (0012-9658) 94:3, 2013 Allison, Steven D; Lu, Ying; Weihe, Claudia; Goulden, Michael L; Martiny, Adam C; Treseder, Kathleen K et al.

Ecological effects of experimental drought and prescribed fire in a southern California coastal grassland Journal of Arid Environments (01401963) 81:., 2012 Potts, D.L.; Suding, K.N.; Winston, G.C.; Rocha, A.V.; Goulden, M.L.

Fertilization effects on the ecohydrology of a southern California annual grassland Geophysical Research Letters 39:8, 2012 Parolari, A. J.; Goulden, M. L.; Bras, R. L.