Functional relationships between leaf hydraulics and leaf economics in response to nutrient addition in subtropical tree species

VILLAGRA M; CAMPANELLO PI; BUCCI SJ; GOLDSTEIN G

TREE PHYSIOLOGY

OXFORD UNIV PRESS

Lugar: Oxford; Año: 2013 p. 1 - 11

0829-318X

Leaves can be both an hydraulic bottleneck and a safety valve against hydraulic catastrophic dysfunctions, and thus changes in traits related to water movement in leaves and associated cost  may be critical for the success of plant growth. A four-year fertilization experiment with N and P addition was done in a semideciduous Atlantic forest in northeastern Argentina. Saplings of five dominant canopy species were grown in similar gaps inside the forests (five control and five N+P addition plots). Leaf lifespan (LL), specific leaf area (SLA), leaf and stem vulnerability to cavitation, leaf hydraulic conductance (Kleaf_area and Kleaf_mass) and leaf turgor loss point (TLP) were measured in the five species and in both treatments. Leaf life span (Mariana no empiezes con abreviaciones) in the studied species tended to decrease with the addition of fertilizers, and SLA was significantly lower in plants with nutrient addition compared to individuals in control plots, providing strong evidences that photosynthetic capacity of leaves across species increased with N+P fertilization. The vulnerability to cavitation of leaves (P50leaf) either increased or decreased with the nutrient treatment depending on the species, but the average P50leaf across species did not change with nutrient additions. The P50leaf increased linearly with SLA and decreased with LL across species and treatments. These tradeoffs have an important functional significance because more expensive (lower SLA) and less vulnerable leaves (lower P50leaf) are retained for a longer period of time. Osmotic potentials at turgor loss point and at full turgor became more negative across species with decreasing P50leaf regardless of nutrient treatment. Kleaf on a mass basis was a strong predictor of SLA, LL and TLP. An intriguing result of this study is that vulnerability to cavitation of stems and leaves were similar, particularly in fertilized plants. Leaves in the species studied may not function as safety valves at low water potentials to protect the water pathway from water stress-induced cavitation. The lack of rainfall seasonality in the subtropical forest studied probably does not act as a selective pressure to enhance hydraulic segmentation between leaves and stems.