Species losses following persistent fertilisation increase grassland stability in response to temperature variation

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Submission Summary

Future climatic projections suggest greater and more variable temperature extremes. Grassland stability responses to climatic stress or anthropogenic eutrophication (both important global change drivers) are often influenced by the grassland's biodiversity. However, grassland responses to interacting global change drivers remain relatively unknown. Given that temperature can influence soil nutrient uptake by plants, understanding how grasslands respond to temperature stress together with changes in soil nutrient status may provide important insight for grassland management. This study explored how the diversity and mean, variability and stability of unfertilised and fertilised mesic grassland productivity responded to temperature stress at three-year scales. We modeled rain use efficiencies (RUE, an absolute measure of grassland productivity) collected from the long term Veld Fertiliser Trial (Ukulinga Research Farm, Pietermaritzburg, South Africa) using linear mixed modelling techniques to understand how RUE stability and its constituents (mean and standard deviation (SD)) changed across mean maximum temperature and maximum temperature SD. Fertilisation rapidly reduced species richness and diversity resulting in homogenous plots dominated primarily by grass species. Productivity analyses revealed that the SD rather than the mean of maximum temperature affected RUE. Mean RUE and RUE SD both increased with maximum temperature SD, however, RUE SD increased more rapidly in unfertilised grasslands than fertilised grasslands. Unfertilised grasslands, therefore, became destabilised during periods of high maximum temperature variability. Increased climatic variability thus appears to have positive impacts on fertilised mesic grasslands, however, we caution that the homogenous nature of these plots' diversity may impact their overall resilience to other disturbances.

Submission ID :
conservationsym20193323
Submission Type
Oral Presentation
Submission Topic
Understanding and managing ecological and evolutionary processes

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