Timing of Drought Triggers Distinct Growth Responses in Holm Oak: Implications to Predict Warming-Induced Forest Defoliation and Growth Decline

Forests

J. Julio Camarero¹  Magí Franquesa²  Gabriel Sang࿎sa-Barreda² 

[1] Pyrenean Institute of Ecology (IPE-CSIC), Avda. Montañana 1005, Apdo. 202, 50192 Zaragoza, Spain;

关键词: defoliation;    dendroecology;    die-off;    Quercus ilex;    phenology;    primary growth;    remote sensing;    secondary growth;    tree ring;    water deficit;   

DOI  :  10.3390/f6051576

来源: mdpi

【 摘 要 】

Droughts negatively impact forests by reducing growth and increasing defoliation leading to forest dieback as the climate becomes warmer and drier. However, the timing and severity of droughts determine how differently or intensively water shortage affects primary (shoot and leaf formation) and secondary growth (stem radial growth based on tree-ring widths). We compare the impact of two severe droughts (2005, 2012), showing different climatic characteristics on the growth responses of three Mediterranean holm oak stands in northeastern Spain. We also quantify climate trends and drought severity. Then, we use remote sensing data to infer how those droughts impacted forest productivity. Both droughts were characterized by warm and dry spring conditions leading to reduced budburst, low shoot production, asynchrony in primary growth and decreased productivity and scarce radial growth, particularly in 2005. However, defoliation peaked in 2012 when radial growth showed minimum values and early spring and late summer temperatures reached maximum values. We discuss how uncoupled and resilient are the responses of primary and secondary growth to drought. Finally, these findings are used to gain insight into the drought-related drivers of defoliation in Spanish holm oak forests.

【 授权许可】

CC BY   
© 2015 by the authors; licensee MDPI, Basel, Switzerland.