Soil functional resistance and stability are linked to different ecosystem properties

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Abstract

The functional resistance and resilience of soils from across the South Island of New Zealand were assessed. Soils were collected from under varying land-uses (pasture, pine forest, native forest) at each of four different locations (Hokitika, Craigieburn, Eyrewell, Orton Bradley Park). Soil function was measured using carbon utilization profiles (MicroResp technique), and responses to freeze-thaw disturbance assessed in a multivariate approach. Resistance was defined as the amount of change in functional profiles (multivariate distance) before, and then 10 h after, disturbance. Resilience was defined as the stability in ecosystem function over time (6 sample points spanning 17 days after initial freeze-thaw disturbance). The functional resistance of soils was not linked to land-use nor sampling location (permanova P > 0.05) but was negatively correlated with soil Olsen-P levels (biological-environmental matching (BIO-ENV test); ρ = 0.604, P = 0.04). Secondary factors associated with soil organic matter status were associated with functional resistance in soil of low Olsen-P. This was explicitly tested by repeating the experiment in soils collected from a long-term P fertilizer management trial; functional resistance remained linked to the underlying P status of the soils (P = 0.002). The functional stability of soil (post-disturbance) was associated with long-term rainfall (canonical analysis on principal coordinates – CAP analysis; P = 0.039); soils from high rainfall sites were more stable after disturbance. The results show that variables linked to functional resistance and resilience in soils are different. Furthermore, resilience was not correlated with resistance, or with measures of functional diversity (e.g. evenness of substrate mineralization). Alteration of the P status of soils is likely to impact on the capacity of soils to rapidly respond to disturbance, whereas drivers of climate, such as global warming, may impact soil functional resilience.

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