Abstract
Abstract Deep soil water, defined here as the soil water below a certain depth and not recharged by precipitation in one growing season, plays a critical role in maintaining eco‐physiological functioning in thick‐vadose‐zone regions. However, science‐based evidence remains limited on how and the extent to which deep soil desiccation (DSD) affects the eco‐physiological features of apple trees. Here, we improve a process‐based model to disentangle trees' transpiration and photosynthesis responses to precipitation and DSD below 200 cm (DSD 200 ) on the semiarid Loess Plateau. We defined four DSD 200 scenarios: 60%–70% of field capacity (FC) as a control, 50%–60%, 40%–50%, and 30%–40% of FC representing mild (MID), moderate (MOD) and severe (SED) desiccation, respectively; and five precipitation scenarios: extremely dry (285.78 mm), dry (392 mm), normal (457.72 mm), wet (524.96 mm), and extremely wet years (630.44 mm). We found that the stomatal conductance, net photosynthetic rate and transpiration under MOD and SED decreased significantly ( p < 0.05), independent of precipitation years, indicating clear stomatal limitation induced by DSD 200 . This phenomenon was greatly enhanced in extremely dry years, with these variables decreasing on average by 29%, 36%, and 37%, respectively. Furthermore, SED resulted in non‐stomatal limitation with a great decrease in electron transport rates ( J max ) and maximum carboxylation rates ( V C max ). J max and V C max decreased by 40% and 26%, respectively, on average, in extremely dry years. These findings indicate that the combination of severe meteorological drought and deep soil drought resulted in non‐stomatal limitation for the apple trees. Persistent non‐stomatal limitation may be an important mechanism causing tree mortality in semiarid loess regions.
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Claims 6
Claim · model-written summary
Stomatal conductance under moderate and severe deep soil desiccation decreased in extremely dry years, by 29% on average.
- Taxon
- apple trees
Malus domesticae0 - Treatment
- DSD 200e1
- Outcome
- stomatal conductancee1
- Direction
- decreasede1
- Value
- 29%e2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“features of apple trees”
e1“the stomatal conductance, net photosynthetic rate and transpiration under MOD and SED decreased significantly ( p < 0.05), independent of precipitation years, indicating clear stomatal limitation induced by DSD 200”
e2“This phenomenon was greatly enhanced in extremely dry years, with these variables decreasing on average by 29%, 36%, and 37%, respectively”
Claim · model-written summary
Net photosynthetic rate under moderate and severe deep soil desiccation decreased in extremely dry years, by 36% on average.
- Taxon
- apple treesMalus domesticae0
- Treatment
- DSD 200e1
- Outcome
- net photosynthetic ratee1
- Direction
- decreasinge2
- Value
- 36%e2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“features of apple trees”
e1“the stomatal conductance, net photosynthetic rate and transpiration under MOD and SED decreased significantly ( p < 0.05), independent of precipitation years, indicating clear stomatal limitation induced by DSD 200”
e2“This phenomenon was greatly enhanced in extremely dry years, with these variables decreasing on average by 29%, 36%, and 37%, respectively”
Claim · model-written summary
Transpiration under moderate and severe deep soil desiccation decreased in extremely dry years, by 37% on average.
- Taxon
- apple treesMalus domesticae0
- Treatment
- DSD 200e1
- Outcome
- transpiratione1
- Direction
- decreasinge2
- Value
- 37%e2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“features of apple trees”
e1“the stomatal conductance, net photosynthetic rate and transpiration under MOD and SED decreased significantly ( p < 0.05), independent of precipitation years, indicating clear stomatal limitation induced by DSD 200”
e2“This phenomenon was greatly enhanced in extremely dry years, with these variables decreasing on average by 29%, 36%, and 37%, respectively”
Claim · model-written summary
Under severe desiccation, the maximum electron transport rate decreased by 40% on average in extremely dry years.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“features of apple trees”
e3“J max and V C max decreased by 40% and 26%, respectively, on average, in extremely dry years”
e4“Furthermore, SED resulted in non‐stomatal limitation with a great decrease in electron transport rates”
Claim · model-written summary
Under severe desiccation, the maximum carboxylation rate decreased by 26% on average in extremely dry years.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“features of apple trees”
e3“J max and V C max decreased by 40% and 26%, respectively, on average, in extremely dry years”
e4“Furthermore, SED resulted in non‐stomatal limitation with a great decrease in electron transport rates”
Claim · model-written summary
Persistent non-stomatal limitation may be an important mechanism causing tree mortality in semiarid loess regions.
- Taxon
- apple treesMalus domesticae0
- Outcome
- tree mortalitye5
- Qualifier
- non‐stomatal limitatione5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“features of apple trees”
e5“Persistent non‐stomatal limitation may be an important mechanism causing tree mortality in semiarid loess regions”
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