Assessing hyperdrought effects during the current megadrought in central
Chilean sclerophyll forest
Abstract
The sclerophyllous forest of Chile has experienced an unprecedented
14-year megadrought (2010-2022), in which, in addition, a period of
hyperdrought was recorded in 2019. In this paper, we assess the
following questions: 1) How has the megadrought affected the net primary
productivity of the Chilean Mediterranean sclerophyll forest in its
current distribution; 2) How have temperature and precipitation affected
this pattern of primary productivity over time; and 3) How did a
hyperdrought event affect the primary productivity of the sclerophyll
forest during the megadrought? The Chilean Mediterranean sclerophyll
forest was considered throughout its current distribution between 31 and
37°S. Net primary productivity was assessed using the Enhanced
Vegetation Index (EVI) for the megadrought (2010 and 2022), hyperdrought
(2019), and pre-megadrought (2000-2009) reference periods using Landsat
satellite imagery. Subsequently, extreme EVI anomalies above or below 90
% of the phenological reference frequency (RFD) were evaluated. To
assess the effect of climate on EVI, precipitation and temperature data
from the CHIRPS satellite were used. To explain the contribution of
precipitation and temperature on EVI, multiple linear regression models
were performed. The results indicate the following: i) the northern
range populations decreased EVI regardless of the period studied, ii)
during the megadrought period, the northern range populations decreased
EVI due to decreased precipitation. On the contrary, in the southern
range populations, EVI is affected by the increase in temperature, and
iii) during the hyperdrought event, a differential response of EVI was
observed, in which the northern distribution and the Andean foothills
populations were severely affected and maintained low EVI values in the
following years. Finally, further ecophysiological studies are needed to
understand the responses of these species to water and thermal stress,
as future climate models predict an increase in drought in the Chilean
Mediterranean, a biodiversity hotspot.