Data_Sheet_1_Terpenoid Emissions of Two Mediterranean Woody Species in Response to Drought Stress.pdf

<p>Drought is a major environmental constrain affecting plant performance and survival, particularly in Mediterranean ecosystems. Terpenoids may play a protective role under these conditions, however, observations of drought effects on plant terpenoid emissions are controversial ranging from decreased emissions to unaffected or increased release of terpenoids. In the present study we investigated terpenoid emissions of cork oak (Quercus suber) and gum rockrose (Cistus ladanifer) in response to summer drought stress in 2017. Pre-dawn leaf water potential (Ψ_PD) decreased from -0.64 to -1.72 MPa in Q. suber and from -1.69 to -4.05 MPa in C. ladanifer, indicating a transition from mild to severe drought along summer. Total terpenoid emissions decreased with drought, but differed significantly between species (p < 0.001) and in response to Ψ_PD, air temperature and assimilation rates. C. ladanifer emitted a large variety of >75 compounds comprising monoterpenes, sesquiterpenes and even diterpenes, which strongly decreased from 1.37 ± 0.23 μg g^-1h^-1 to 0.40 ± 0.08 μg g^-1h^-1 (p < 0.001) in response to drought. Total emission rates were positively correlated to air temperature (p < 0.001). C. ladanifer behavior points toward terpenoid leaf storage depletion and reduced substrate availability for terpenoid synthesis with increasing drought, most likely accelerated by high air temperatures. Q. suber emitted mainly monoterpenes and emissions declined significantly from June (0.50 ± 0.08 μg g^-1h^-1) to August (0.29 ± 0.02 μg g^-1h^-1) (p < 0.01). Emission rates were weakly correlated with net assimilation rates (R² = 0.19, p < 0.001), but did not respond strongly to Ψ_PD and air temperature. Early onset of drought in 2017 most likely reduced plant metabolism in Q. suber, resulting in diminished, but stable terpenoid fluxes. Calculation of standard emission factors (at 30°C) revealed contrasting emission patterns of decreasing, unaffected, or increasing fluxes of single terpenoid compounds. Unaffected or drought-enhanced emissions of compounds such as α-pinene, camphene or manoyl oxide may point toward a specific role of these terpenoids in abiotic stress adaptation. In conclusion, these results suggest a strong negative, but species- and compound-specific effect of severe drought on terpenoid fluxes in Mediterranean ecosystems.</p

Changes in <i>C</i>. <i>ladanifer</i> population density (shrubs per 8 m²) in 2007 and 2013 in the ungulate-excluded and ungulate-exposed plots.

<p>Because the interaction between ungulate exclusion and year was significant, we report the <i>P</i>-values of the tests for the four simple main effects involved in the interaction.</p

Change in abundance and richness of non-native and native species after nutrient treatments for sites included in the study

This file contains data on the change in abundance and richness of non-native and native species after nutrient enrichment (1-3 years) use for analyses. The change in abundance data was derived at the plot level. Metadata can be found in the ReadMe file

Information on sites included in this study

This file contains information on the name, location, type (experimental or observational) and name of persons in charge of setting and maintaining the NutNet sites which data was used for this study. Information on each of the variables included in this file can be found in the ReadMe file