Abstract
Abstract Leaf hydraulic traits are considered the key determinants of gas exchange and therefore affect species distributions along environmental gradients, but the patterns of leaf hydraulic traits and their associations with gas exchange across altitudinal gradients remain largely unknown. Here, we measured leaf hydraulic traits, gas exchange, leaf anatomical traits and plant size traits in two dominant alpine shrubs ( Caragana jubata and Salix gilashanica ) across an altitudinal gradient from 3100 to 3700 m. The findings indicated that with increasing altitude, both shrub species exhibited an increase in leaf hydraulic safety (more negative K leaf P 50 ), a decrease in leaf hydraulic efficiency ( K leaf‐max ) and an increase in intrinsic water use efficiency (WUE i ), thus allowing them to adapt to higher altitude habitats. The more negative K leaf P 50 was associated with a greater ratio of major to minor vein density (VLA maj /VLA min ), the lower K leaf‐max was associated with a lower minor vein density (VLA min ) and greater increase in WUEi arose from the small decrease in the photosynthetic rate relative to the stomatal conductance. However, C. jubata was consistent with the ‘hydraulic safety strategy’ with a great decrease in K leaf P 50 , a small decrease in K leaf‐max and a small increase in WUE i along with decreasing plant height and leaf area with increasing altitude. Whereas S. gilashanica was consistent with the ‘photosynthetic efficiency strategy’ with a small decrease in K leaf P 50 , a greater decrease in K leaf‐max and a greater increase in WUE i along with an increasing plant height and unchanged leaf area with increasing altitude. Overall, these findings provide new insights to improve understanding how shift in leaf hydraulic traits and their associations with gas exchange and plant size allow plants to adapt to high‐altitude habitats. Read the free Plain Language Summary for this article on the Journal blog.
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Claims 11
Claim · model-written summary
Both shrubs increased leaf hydraulic safety with altitude.
Not reportedTaxon
Verbatim
e0“with increasing altitude, both shrub species exhibited an increase in leaf hydraulic safety (more negative K leaf P 50 )”
Claim · model-written summary
Both shrubs decreased leaf hydraulic efficiency with altitude.
Not reportedTaxon
Verbatim
e0“a decrease in leaf hydraulic efficiency ( K leaf‐max )”
Claim · model-written summary
Both shrubs increased intrinsic water use efficiency with altitude.
Not reportedTaxon
Verbatim
e0“an increase in intrinsic water use efficiency (WUE i )”
Claim · model-written summary
More negative hydraulic safety threshold was associated with a greater major to minor vein density ratio.
Not reportedTaxon
Verbatim
e0“The more negative K leaf P 50 was associated with a greater ratio of major to minor vein density (VLA maj /VLA min )”
Claim · model-written summary
Lower maximum leaf hydraulic conductance was associated with lower minor vein density.
Not reportedTaxon
Verbatim
e0“the lower K leaf‐max was associated with a lower minor vein density (VLA min )”
Claim · model-written summary
Greater water use efficiency increase arose from a smaller photosynthetic decline relative to stomatal conductance.
- Outcome
- increase in WUEie0
- Qualifier
- small decrease in the photosynthetic rate relative to the stomatal conductancee0
Not reportedTaxon
Verbatim
e0“greater increase in WUEi arose from the small decrease in the photosynthetic rate relative to the stomatal conductance”
Claim · model-written summary
Caragana had a large decrease in hydraulic safety threshold, a small decrease in efficiency and small water use efficiency increase.
- Taxon
- C. jubata
Caragana jubatae0 - Outcome
- ‘hydraulic safety strategy’e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“C. jubata was consistent with the ‘hydraulic safety strategy’ with a great decrease in K leaf P 50 , a small decrease in K leaf‐max and a small increase in WUE i”
Claim · model-written summary
Caragana height and leaf area declined with altitude.
Not reportedTaxon
Verbatim
e0“decreasing plant height and leaf area with increasing altitude”
Claim · model-written summary
Salix showed small safety threshold decline, greater hydraulic efficiency decline and greater water use efficiency increase.
- Taxon
- S. gilashanicaSalix gilashanicae0
- Outcome
- ‘photosynthetic efficiency strategy’e0
Verbatim
e0“S. gilashanica was consistent with the ‘photosynthetic efficiency strategy’ with a small decrease in K leaf P 50 , a greater decrease in K leaf‐max and a greater increase in WUE i”
Claim · model-written summary
Salix height increased with altitude.
Not reportedTaxon
Verbatim
e0“an increasing plant height and unchanged leaf area with increasing altitude”
Claim · model-written summary
Salix leaf area was unchanged with altitude.
Not reportedTaxon
Verbatim
e0“an increasing plant height and unchanged leaf area with increasing altitude”