Journal
EUROPEAN JOURNAL OF FOREST RESEARCH
Volume 133, Issue 1, Pages 153-164Publisher
SPRINGER
DOI: 10.1007/s10342-013-0754-6
Keywords
Chlorophyll degradation; Fertigation; Nitrogen use efficiency; Photosynthesis; Leaf senescence
Categories
Funding
- Fred M. van Eck Forest Foundation
- Hardwood Tree Improvement and Regeneration Center
- Department of Forestry and Natural Resources at Purdue University
- Foresta Capital
- Foresta Mantenimiento de Plantaciones
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Physiological mechanisms by which nitrogen (N) fertilization affects growth and development in temperate deciduous forest trees are not clearly understood, especially under intensive silvicultural systems. Grafted, Tippecanoe 1 cultivar black walnut (Juglans nigra L.) trees were grown in an intensively managed plantation in west-central Spain and subjected to six, fixed-nutrient-ratio complete fertilizer treatments (defined as 0, 25, 50, 75, 150, and 300 g N tree(-1)) delivered via daily fertigation. Leaf chemistry and morphology were evaluated from June to September, and gas exchange was measured in July. Specific leaf mass, leaflet nitrogen (N), and chlorophyll concentrations varied over the course of the growing season, yet consistently increased with increasing fertilization. Net photosynthesis at ambient (A (net)) and light-saturated (A (max)) conditions increased from the unfertilized control to lowest treatment (25 g N) but did not increase at higher fertilizer rates. Photosynthetic N and chlorophyll use efficiencies decreased with increasing fertilization, but photosynthetic phosphorus and water use efficiencies increased. Transpiration rates and dark respiration were not significantly affected by treatment. Overall, the lowest fertilizer treatment (25 g N) had the greatest photosynthetic efficiency. Interactions between N and other nutrients with increasing fertilizer application suggested potential for nutrient imbalances at high fertilization rates. Our results provide a physiological justification for the use of low-to-moderate fertilization as an efficient strategy to promote black walnut plantation establishment under intensive cultural systems.
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