Resilience of soil respiration to plant stress

Strong resilience of soil respiration as shown in two different studies by Barba et al. (2016) and Egan et al. (2011) in response to stress.

With shifting regional and global climates, understanding the response of ecosystems to drought-induced stress is becoming increasingly critical.

A paper published by Barba et al. (2016) in Oecologia yielded some unexpected results showing that drought-induced die-off of Scots pine (Pinus sylvestris) forest seemed to have no effect on the soil respiration from both heterotrophic and autotrophic contributors. However, when the successional species, holm oak (Quercus ilex), took hold both heterotrophic and total soil respiration dropped significantly,

The study highlights the resilience of the coniferous species to drought related damage and the potential for a shift in carbon balance as Scots pine begin to die off at the lower limit of their distribution in Europe.

Pinus-sylvestris-scots-pineeuropean-range

Range of Scots pine (Pinus sylvestris) showing southern-most limits at the 40th parallel north.

Here in Nova Scotia, a similar resilience to girdling-related stress was observed in Red pine, by Egan et al. (2011). When the bark was removed from the pine species to prevent the flow of carbohydrates to the roots, no significant change in total respiration was observed nor was there an observed shift is the balance between heterotopic and autotrophic respiration, as measured using natural abundance isotopic techniques.

girdled-trees-soil-respiration-study-egan-2011

Girdled Red pine trees (2010) near Heatherton, Nova Scotia.

 

co2-soil-respiration-girdling-experiment-egan

Relative CO2 flux from the girdled and control sites before and after girdling. Girdling seemed to have no effect on total soil respiration (Egan et al. 2011).

These findings are very intriguing and lead to a number of questions,  mainly “What is going on in there?”.  The authors believe that it might be due to mobilization of stored carbohydrates, by what mechanism, however, is definitely an avenue of future research.

 

References

Barba, J., Curiel Yuste, J., Poyatos, R., Janssens, I.A., Lloret, F., (2016). Strong resilience of soil respiration components to drought-induced die-off resulting in forest secondary succession. Oecologia (In Press)

Abstract: Globally increasing drought-induced forest die-off and its associated vegetation shifts may have direct impacts on soil respiration. Here, we found that soil respiration and its autotrophic and heterotrophic components remained unaffected 3-11 years following drought-induced Scots pine die-off. Despite this post-disturbance functional resilience, the replacement by holm oak was associated with a strong reduction in the heterotrophic respiration component, producing an important drop in total soil respiration.

Egan, J., Risk, D. and Nickerson N., High-resolution δ13CO2 soil efflux monitoring in tree girdling experiment exposes large temporal variability, AGU Fall Meeting, San Francisco, California (2011).