PARENT SESSION
Poster Session 23: Soil Ecology
Wednesday, August 10, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal

Spatial aggregation of soil resources affects decomposition, plant growth, and root proliferation.

Loecke, Terrance^*,1, Robertson, G. Philip¹, ¹ Kellogg Biological Station, Hickory Corners, MI

ABSTRACT- Soil resource spatial heterogeneity at the landscape scale is known to influence many ecosystem processes; however, we want to know if heterogeneity at the scale of an individual plant can also be important. We conducted greenhouse experiments to determine the effect of spatial litter aggregation on decomposition, plant growth, and root proliferation. In the first set of experiments, 3.5 g of finely ground red clover litter was evenly distributed into 2, 8, 32, or 128 patches or uniformly in 3-L pot. Decomposition was dampen temporally as litter aggregation increased with uniform litter distributions decomposing faster than highly aggregated litter. Plant growth response to litter aggregation was assessed with this same experimental setup. Two domesticated annuals, Zea mays and Helianthus annuus, had the greatest growth at intermediate levels of litter aggregation, whereas the three other species tested (Bromus inermis, Setaria faberi, and Schizachyrium scoparium) showed inconsistent responses to litter aggregation. These results suggest that plant species characteristics control sensitivity to resource spatial distribution or that synchrony between resource supply rate and plant resource demand rate is important. Root proliferation selectivity for resource quality maybe one mechanism whereby plants increase their competitiveness with the decomposer community for heterogeneously distributed soil resources, thus a possible causal link to the increased plant productivity in heterogeneous soil environments. In a greenhouse experiment, we tested the selectivity of Avena sativa and B. inermis root placement into patches of varying qualities. Each plant had equal access to two types of decomposing litter patches placed into two of four quadrates. A. sativa root proliferation (root length density) was significantly influenced by the contrast between patch qualities; whereas, B. inermis root placement was random with respect to patch quality. We conclude that not all plant species behave the same in response to resource quality choices. These simple experiments demonstrate that spatial heterogeneity within the scale of an individual plant can influence ecosystem functions and potentially plant-microbe soil resource competition.

Key words: spatial heterogeneity, Nitrogen cycling, root proliferation