Aboveground Net Primary Productivity and Nutrient Content of Fertilized Plantation Sweetgum
1995
Nelson, L. E. | Switzer, G. L. | Shelton, M. G.
Sweetgum (Liquidambar styraciflua L.) is a commercially desirable species that can be successfully established in plantations, and information is needed concerning its genotypic variation and response to fertilization. This study evaluates various aspects of productivity and nutrition for two half-sib seed sources in a 9-yr-old sweetgum plantation that was refertilized in 1981 with a total of 0, 100, 200, or 400 kg N ha⁻¹. Foliar and litter samples were collected in the year preceding and for 3 yr following N application, and tree diameter and height were measured annually. Aboveground net primary productivity (AGNPP) of the unfertilized controls averaged 6.7 Mg ha⁻¹ from 1981 to 1983. By contrast, maximum AGNPP for treatments receiving N were 11, 16, and 16 Mg ha⁻¹ in 1981, 1982, and 1983, respectively. Fertilization resulted in large increases in foliar biomass and leaf area index (LAI); values were highest in 1982, and then declined in 1983. Most responses peaked at the highest application rate, but differences between 200 and 400 kg N ha⁻¹ were generally small. Estimated apparent recovery of applied N in aboveground tissues was 75% for the 100 kg N ha⁻¹ rate in the first and second years; however, in the third year following fertilization only 47% was accounted for. The response of the two half-sib seed sources differed, especially in terms of woody biomass.
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