Size-dependent enhancement of water relations during post-fire resprouting

作者：Schafer Jennifer L^*; Breslow Bradley P; Hollingsworth Stephanie N; Hohmann Matthew G; Hoffmann William A

来源：Tree Physiology, 2014, 34(4): 404-414.

DOI：10.1093/treephys/tpu015

• leaf area
• leaf-specific whole-plant hydraulic conductance
• mid-day leaf water potential
• root hydraulic conductance
• stem height
• stomatal conductance

In resprouting species, fire-induced topkill causes a reduction in height and leaf area without a comparable reduction in the size of the root system, which should lead to an increase in the efficiency of water transport after fire. However, large plants undergo a greater relative reduction in size, compared with small plants, so we hypothesized that this enhancement in hydraulic efficiency would be greatest among large growth forms. In the ecotone between long-leaf pine (Pinus palustris Mill.) savannas and wetlands, we measured stomatal conductance (g(s)), mid-day leaf water potential (Psi(leaf)), leaf-specific whole-plant hydraulic conductance (K-L.p), leaf area and height of 10 species covering a range of growth forms in burned and unburned sites. As predicted, K-L.p was higher in post-fire resprouts than in unburned plants, and the post-fire increase in K-L.p was positively related to plant size. Specifically, large-statured species tended to undergo the greatest relative reductions in leaf area and height, and correspondingly experienced the greatest increases in K-L.p. The post-fire increase in K-L.p was smaller than expected, however, due to a decrease in absolute root hydraulic conductance (i.e., not scaled to leaf area). The higher K-L.p in burned sites was manifested as an increase in gs rather than an increase in Psi(leaf). Post-fire increases in gs should promote high rates of photosynthesis for recovery of carbohydrate reserves and aboveground biomass, which is particularly important for large-statured species that require more time to recover their pre-fire size.

• 出版日期2014-4