2 research outputs found
Drought legacies are short, prevail in dry conifer forests and depend on growth variability
1. The negative impacts of drought on forest growth and productivity last for several
years generating legacies, although the factors that determine why such legacies
vary across sites and tree species remain unclear.
2. We used an extensive network of tree-ring width (RWI, ring-width index) records
of 16 tree species from 567 forests, and high-resolution climate and normalized difference
vegetation index (NDVI) datasets across Spain during the common period
1982â2008 to test the hypothesis that climate conditions and growth features modulate
legacy effects of drought on forests. Legacy effects of drought were calculated
as the differences between detrended-only RWI and NDVI series (i.e. after removing
long-term growth trends) and pre-whitened RWI and NDVI series predicted by a
model including drought intensity. Superposed Epoch Analysis (SEA) was used to estimate
whether legacy effects differed from random. Finally, legacy effects were related
to water balance, growth persistence and variability, and tree species identity.
3. We found a widespread occurrence of drought legacy effects on both RWI and
NDVI, but they were seldom significant. According to SEA, first-year drought
legacies were negative and different from random in 9% and 5% of the RWI and NDVI series respectively. The number of significant second- and third-year legacies
was substantially lower. Differences between RWI and NDVI legacies indicate
that canopy greenness and radial growth responses to drought are decoupled. We
found variations in legacies between tree species with gymnosperms presenting
larger first-year drought legacies than angiosperms, which were exposed to less
severe droughts. Greater growth variability can explain the presence of first-year
RWI legacies in gymnosperms from dry sites despite that the relationship between
growth variability and legacies was complex.
4. Synthesis. Accounting for species and site responses to drought provides a better
understanding of the magnitude and duration of drought legacies on forest
growth and productivity. Despite the widespread occurrence of growth reductions
in the years during and after drought occurrence, significant legacies were
not very common, mostly lasted one year, and were more widespread in gymnosperms.
These are relevant factors to be considered in the future when studying
the consequences of drought on forest productivity and tree growth.This study was financially supported by: Xunta de Galicia, Grant/
Award Number: PGIDIT06PXIB502262PR, GRC GI-1809; INIA,
Grant/Award Number: RTA2006-00117; CANOPEE, 2014-2020-
FEDER funds; and Spanish Science Ministry: RTI2018-09688
4-
B-C31, RTI2018-096884-B-C33, AGL2017-83828-C2-2R and
ENV4-CT97-0641 projects. GSB was supported by a âJuan de la
Cierva FormaciĂłnâ grant from MINECO (FJCI 2016-30121). This
re
-
search was supported by the BERC 2018-2021 program, and by the
Spanish Ministry of Science, Innovation and Universities t
hrough
the BC3 MarĂa de Maeztu excellence accreditation (MDM-2017-
0714) and the IBERYCA (CGL2017-84723-P) project. R.S.S. was s
up
-
ported by VULBOS project (UPO-1263216, FEDER Funds, And
alusia
Regional Government, ConsejerĂa de EconomĂa, Conocimiento,
Empresas y Universidad 2014-2020), and A.H. by PinCaR pro
ject
(UHU-1266324, FEDER Funds, Andalusia Regional Government ConsejerĂa de EconomĂa, Conocimiento, Empresas y Universidad
2014-2020). K.N. was supported by the Ministry of Educatio
n,
Science and Sports (Republic of Slovenia, Raziskovalci-2.1-
UL-BF-
C3330-19-952011). We sincerely thank the in-depth analyse
s and
comments provided by the reviewers
Drought legacies are short, prevail in dry conifer forests and depend on growth variability
12 Pags.- 34Figs.- 3 Tabls.Abstract
The negative impacts of drought on forest growth and productivity last for several years generating legacies, although the factors that determine why such legacies vary across sites and tree species remain unclear.
We used an extensive network of treeâring width (RWI, ringâwidth index) records of 16 tree species from 567 forests, and highâresolution climate and normalized difference vegetation index (NDVI) datasets across Spain during the common period 1982â2008 to test the hypothesis that climate conditions and growth features modulate legacy effects of drought on forests. Legacy effects of drought were calculated as the differences between detrendedâonly RWI and NDVI series (i.e. after removing longâterm growth trends) and preâwhitened RWI and NDVI series predicted by a model including drought intensity. Superposed Epoch Analysis (SEA) was used to estimate whether legacy effects differed from random. Finally, legacy effects were related to water balance, growth persistence and variability, and tree species identity.
We found a widespread occurrence of drought legacy effects on both RWI and NDVI, but they were seldom significant. According to SEA, firstâyear drought legacies were negative and different from random in 9% and 5% of the RWI and NDVI series respectively. The number of significant secondâ and thirdâyear legacies was substantially lower. Differences between RWI and NDVI legacies indicate that canopy greenness and radial growth responses to drought are decoupled. We found variations in legacies between tree species with gymnosperms presenting larger firstâyear drought legacies than angiosperms, which were exposed to less severe droughts. Greater growth variability can explain the presence of firstâyear RWI legacies in gymnosperms from dry sites despite that the relationship between growth variability and legacies was complex.
Synthesis. Accounting for species and site responses to drought provides a better understanding of the magnitude and duration of drought legacies on forest growth and productivity. Despite the widespread occurrence of growth reductions in the years during and after drought occurrence, significant legacies were not very common, mostly lasted one year, and were more widespread in gymnosperms. These are relevant factors to be considered in the future when studying the consequences of drought on forest productivity and tree growth.This study was financially supported by: Xunta de Galicia, Grant/Award Number: PGIDIT06PXIB502262PR, GRC GIâ1809; INIA, Grant/Award Number: RTA2006â00117; CANOPEE, 2014â2020âFEDER funds; and Spanish Science Ministry: RTI2018â096884âBâC31, RTI2018â096884âBâC33, AGL2017â83828âC2â2R and ENV4âCT97â0641 projects. GSB was supported by a âJuan de la Cierva FormaciĂłnâ grant from MINECO (FJCI 2016â30121). This research was supported by the BERC 2018â2021 program, and by the Spanish Ministry of Science, Innovation and Universities through the BC3 MarĂa de Maeztu excellence accreditation (MDMâ2017â0714) and the IBERYCA (CGL2017â84723âP) project. R.S.S. was supported by VULBOS project (UPOâ1263216, FEDER Funds, Andalusia Regional Government, ConsejerĂa de EconomĂa, Conocimiento, Empresas y Universidad 2014â2020), and A.H. by PinCaR project (UHUâ1266324, FEDER Funds, Andalusia Regional Government, ConsejerĂa de EconomĂa, Conocimiento, Empresas y Universidad 2014â2020). K.N. was supported by the Ministry of Education, Science and Sports (Republic of Slovenia, Raziskovalciâ2.1âULâBFâ C3330â19â952011).Peer reviewe