Abstract
PREMISE: Resilience to the interaction of multiple stress factors of drought, wildfire, and canker disease has been little studied. During the 2012 to 2016 megadrought in California, black walnut trees were observed to resprout from the base due to water stress-induced dieback. After monitoring plants for a year, wildfire burned all the plants at two of our study sites, which was followed by vegetative resprouting. Plants also expressed symptoms of canker disease. We thus had an opportunity to assess the impacts of water stress, wildfire, growth form, and canker disease on plant performance. METHODS: Water potentials and photosynthetic rates of drought-induced resprouts were monitored and compared to nearby adults that had not experienced drought-induced dieback, both inland (San Dimas, California) and at coastal exposures (Malibu, CA). We monitored the recovery of adults and drought-induced resprouts from 2017 to 2019, including fire-induced resprouts at coastal exposures following a 2018 wildfire. In addition, stem canker number and canker length were compared among irrigated and non-irrigated growth forms, including drought-induced resprouts, coppice-induced resprouts, adults, and resprouting adults. RESULTS: Drought-induced resprouts displayed higher water potentials and photosynthetic rates than adults, especially during dry periods, but had lower (more negative) values than fire-induced resprouts. Non-irrigated walnut trees displayed greater canker initiation and canker elongation rates than irrigated trees, with irrigated coppice-induced resprouts showing the least canker development. CONCLUSIONS: Resprouting can temporarily relieve water stress, but xylem water stress and canker disease agents feed off one another. Repeat stresses of drought, fire and disease compound to reduce the resilience of individuals and populations of walnut.
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Claims 9
Claim · model-written summary
Drought-induced resprouts had higher water potentials than adults, particularly in dry periods.
- Taxon
- Juglans californica
Juglans californicat0 - Material
- Drought-induced resproutse0
- Outcome
- water potentialse0
- Direction
- highere0
- Qualifier
- especially during dry periodse0
- Comparator
- adultse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Drought-induced resprouts displayed higher water potentials and photosynthetic rates than adults, especially during dry periods”
t0“Juglans californica”
Claim · model-written summary
Drought-induced resprouts had higher photosynthetic rates than adults, particularly in dry periods.
- Taxon
- Juglans californicaJuglans californicat0
- Material
- Drought-induced resproutse0
- Outcome
- photosynthetic ratese0
- Direction
- highere0
- Comparator
- adultse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Drought-induced resprouts displayed higher water potentials and photosynthetic rates than adults, especially during dry periods”
t0“Juglans californica”
Claim · model-written summary
Drought-induced resprouts had lower water potentials than fire-induced resprouts.
- Taxon
- Juglans californicaJuglans californicat0
- Material
- Drought-induced resproutse0
- Outcome
- valuese0
- Direction
- lowere0
- Comparator
- fire-induced resproutse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Drought-induced resprouts displayed higher water potentials and photosynthetic rates than adults, especially during dry periods, but had lower (more negative) values than fire-induced resprouts”
t0“Juglans californica”
Claim · model-written summary
Non-irrigated trees had greater canker initiation than irrigated trees.
Verbatim
e0“Non-irrigated walnut trees displayed greater canker initiation and canker elongation rates than irrigated trees”
Claim · model-written summary
Non-irrigated trees had greater canker elongation rates than irrigated trees.
Verbatim
e0“Non-irrigated walnut trees displayed greater canker initiation and canker elongation rates than irrigated trees”
Claim · model-written summary
Irrigated coppice-induced resprouts had the least canker development.
- Taxon
- Juglans californicaJuglans californicat0
- Material
- coppice-induced resproutse0
- Outcome
- canker developmente0
- Direction
- leaste0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“irrigated coppice-induced resprouts showing the least canker development”
t0“Juglans californica”
Claim · model-written summary
Resprouting can temporarily relieve water stress.
- Taxon
- Juglans californicaJuglans californicat0
- Outcome
- water stresse0
- Direction
- relievee0
- Qualifier
- Resproutinge0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Resprouting can temporarily relieve water stress”
t0“Juglans californica”
Claim · model-written summary
Xylem water stress and canker disease agents reinforce one another.
- Taxon
- Juglans californicaJuglans californicat0
- Outcome
- xylem water stress and canker disease agents feed off one anothere0
- Qualifier
- xylem water stresse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“xylem water stress and canker disease agents feed off one another”
t0“Juglans californica”
Claim · model-written summary
Repeated drought, fire and disease reduce walnut resilience.
Verbatim
e0“Repeat stresses of drought, fire and disease compound to reduce the resilience of individuals and populations of walnut”