BAC: Biodiversity and Climate
Experiment Id

Climate changes forecast for our region by GCM’s and shifts in biodiversity and composition each have the potential to alter ecosystem functioning; their interactive effects are unknown. The "BAC" experiment was designed to determine the direct and interactive effects of plant species numbers, plant community composition, temperature, and precipitation on 11 productivity, C and N dynamics, stability, and plant, microbe, and insect species abundances in CDR grassland ecosystems.  BAC was established in 2009 and terminated at the end of 2015. 

Warming lamps deployed over a BAC plot, June 2014. 

Experiment Design

from: (E120) Tilman et al. (2001) Diversity and productivity in a long-term grassland experiment. Science 294, 843?845. doi:10.1126/science.1060391 
(BAC)Cowles, J. M., P. D. Wragg, A. J. Wright, J. S. Powers, and D. Tilman. 2016. Shifting grassland plant community structure drives positive interactive effects of warming and diversity on aboveground net primary productivity. Global Change Biology 22:741-749.


The BAC experiment used a subset of 38 plots from the Biodiversity II (e120) experiment which began in 1994. Biodiversity II is contained within a block of 342 plots laid out in a grid. Each plot was established as a 13 m x 13 m square, but only the central 9 m x 9 m is actively maintained to contain the specified species and level of plant diversity. BAC plots consist of fourteen monoculture plots, nine plots planted to 4 species, nine plots planted to 16 species and six plots planted to 32 species. Plant species are from 4 different functional groups (4 species, each, of C3 grasses, C4 grasses, legumes and non-legume forbs) that are likely to respond differently to changes in temperature and water availability. The diversity by warming treatments are a fully factorial split-plot design, with each of high, low, and control heat treatment subplots nested within each of 1, 4, 16 and 32 species diversity treatment whole-plots.

Warming Treatments

Warming treatments were applied to 2.5 x 3 m subplots via infrared lamps (Kalglo Electronics, Bethlehem, PA, USA). The three warming treatments are control (metal shade above plot to simulate shading effects of lamps), low heat (600 W lamp), and high heat (1200 W lamp). Pre-experiment bare-ground trials of the infrared lamps indicated that the low heat treatment would approximately warm the soil by +1.5C while the high heat treatment would exhibit an approximate warming of +3C. Lamps are turned on from March to November.

Heat Lamps

Kalglo Electronics, Bethlehem, PA, USA High Intensity: Model MRM-2412 240V w/ mod ref 1200W 5.0A 50/60Hz 1Ph 30’ cord Ser.#: 20071771 Low Intensity: Model MRM-2406 240V w/ mod ref 600W 2.5A 50/60Hz 1Ph 50’ cord Ser.#: 20071651

Treatment Tables

Download treatment tables (zip file)


View data in the Data Catalog

Select Publications

The influence of functional diversity and composition on ecosystem processes
D Tilman, J Knops, D Wedin, P Reich, M
1997 Science 277 (5330), 1300-1302

Shifting grassland plant community structure drives positive interactive effects of warming and diversity on aboveground net primary productivity
JM Cowles, PD Wragg, AJ Wright, JS Powers, D Tilman
2016 Global Change Biology 22 (2), 741-749

Community diversity outweighs effect of warming on plant colonization
JA Catford, JM Dwyer, E Palma, JM Cowles, D Tilman
2020 Global change biology 26 (5), 3079-3090

Identifying mechanisms that structure ecological communities by snapping model parameters to empirically observed tradeoffs
A Thomas Clark, C Lehman, D Tilman
2018 Ecology letters 21 (4), 494-505