10.5061/DRYAD.MSBCC2FVH
Guignabert, Arthur
0000-0002-1512-6760
National Research Institute for Agriculture, Food and Environment
Augusto, Laurent
National Research Institute for Agriculture, Food and Environment
Gonzalez, Maya
École Nationale Supérieure des Sciences Agronomiques de Bordeaux-Aquitaine
Chipeaux, Christophe
National Research Institute for Agriculture, Food and Environment
Delerue, Florian
Bordeaux INP - Univ. Bordeaux Montaigne
Complex biotic interactions mediated by shrubs: revisiting the
stress-gradient hypothesis and consequences for tree seedling survival
Dryad
dataset
2020
Water stress
plant-plant interactions
indirect effects
Stress-gradient hypothesis
associational resistance
associational susceptibility
tree regeneration
French National Institute for Agricultural Research
https://ror.org/01x3gbx83
2020-04-23T00:00:00Z
2020-04-23T00:00:00Z
en
https://doi.org/10.1111/1365-2664.13641
233116 bytes
3
CC0 1.0 Universal (CC0 1.0) Public Domain Dedication
1. Using nurse shrubs to improve tree seedling establishment in stressed
environments is a common practice in forestry. Recent refinements of the
stress-gradient hypothesis suggest that positive nurse effects occur under
intermediate stress and decline in the harshest conditions. Additionally,
indirect facilitation is expected in low-stressed/productive systems
according to the initial stress-gradient hypothesis. However, there have
been fewer investigations into the use of nurse shrubs to decrease
herbivore impacts in stressed systems compared with the role of nurses on
stress alleviation. This raises the need to clarify conditions in which
the use of nurse shrubs would be most appropriate. 2. We conducted a field
experiment in the sand dune forest of southwest France characterised by
severe summer water shortages and the presence of different types of wild
herbivores. In 2015 and 2016, Pinus pinaster seedlings were planted under
shrubs (Arbutus unedo) or in shrub-removed locations, in fenced/unfenced
areas. Survival, cause of mortality, and water stress were monitored for
one year after plantation. 3. Summer drought was the main cause of
mortality. Water stress increased in both years as summer progressed. We
found direct facilitation only in July 2016 at intermediate water stress,
due to a decrease in vapour pressure deficit under shrubs. These positive
effects declined in late summer when stress was at a maximum. Rodent
damage occurred under shrubs in spring whereas ungulate browsing was
observed in open areas in autumn/winter. Overall seedling survival was
equivalent under or outside shrubs during the first year, but was better
under shrubs in the second one. 4. Synthesis and applications: Our results
partially validate the refinement of the stress-gradient hypothesis, with
a decline of positive interactions in the most water-stressed conditions.
This draws attention to the difficulty of using shrubs as nurses to
improve tree regeneration in the most xeric systems. In addition, we show
that indirect associational effects, both positive and negative, could be
as important as abiotic stress alleviation in a stressful ecosystem, and
using shrubs to facilitate seedling survival could be efficient depending
on the type of herbivore involved. This highlights the fact that
considering plant-plant interactions can help in the design of management
options, providing that up-to-date ecological theories are considered and
that the different biotic and abiotic constraints are accurately
evaluated.