Management history can cause irreversible changes in agroecosystems: an experimental demonstration

Abstract History-dependence plays a significant role in understanding how ecosystems can shift dramatically in response to environmental changes. Hysteresis is a special case where a shift from a desirable state to an undesirable change can only be reversed when an external driver of change (e.g. pollution) is brought down to a much lower level than at the level in which the unfavorable transition first occurred. Here we ask whether hysteresis or a different form of history-dependence can be observed in plant-soil interactions due to changing agricultural management, and determine the ecological causes. We show that history-dependence is more complex in a common garden experiment where we observe Zea Mays growing under different fertilization treatments. Of particular interest is the case where nitrite leaching decreases irreversibly when fertilization is shifted from inorganic to organic sources. We complement the experiment with a simple mathematical model of nutrient cycling, which shows that correlation between nutrient loss rate and recycling rate are sufficient to cause irreversible shifts in the plant-soil system. Overall, our results show that complex history-dependence due to past management occurs in an agricultural context and plant-soil interactions more broadly.