Leaf resorption efficiency and proficiency in a Quercus robur population following forest harvest

Nutrient resorption is an important mechanism for nutrient preservation in plants. Variations in nutrient availability can interfere with resorption-regulating mechanisms. Disturbances (such as forest harvest) leading to a loss of organic matter and nutrients in the soil could therefore determine important changes in resorption rates. This paper examines the effect of pine forest harvest on N and P resorption in young common oaks (Quercus robur) living under pine cover over a 4-year study period. The results obtained show a decrease in N-NH4+ concentration in the soil in the 2 years following the forest harvest process. Forest harvest did not affect the edaphic concentration of NO3− and PO43−, which presented relatively low values in both areas. Foliar concentration of N was significantly lower in the areas affected by forest harvest, whereas the differences in the foliar concentration of P varied each year. The mean foliar N/P ratio was greater in the non-harvested areas, but showed possible limitation by P in both harvested and non-harvested sites.N and P resorption efficiency presented a lower range of mean values in the forest covered than felled areas. N resorption proficiency was significantly greater in felled areas, with no significant differences found in P resorption proficiency between treatments. P resorption proficiency was significantly greater than N resorption proficiency with terminal levels of P in leaves showing intermediate (<0.08%) or complete (<0.05%) resorption, whereas N resorption was incomplete throughout the 4 years of the study period, with N levels of over 1.0% in senescent leaves.The results obtained show that a disturbance such as forest harvest produces changes in foliar N and P resorption efficiency and proficiency, although differences between years represent the main source of variation.