The dynamics of soil bacterial community structure in response to yearly repeated agricultural copper treatments.

The annual dynamics of soil bacterial community structure, including early, dose-dependent and transient modifications, was observed consecutively at different levels of copper contamination (high: 48 kg Cu ha(-1), low: 16 kg Cu ha(-1)) repeated yearly over a three-year field experiment. Repeated low-level Cu contamination led to an increase in community stability to metal stress without a long-term shift in the population structure, whereas repeated high-level Cu contamination induced a novel and stable bacterial community structure. Furthermore, field experimentation highlighted that episodic climatic stress can modulate copper impact by enhancing community stability.