Soil and pine foliage nutrient responses 15 years after competing-vegetation control and their correlation with growth for 13 loblolly pine plantations in the southern United States

Abstract

Influences of competition-control treatments on long-term soil and foliar nutrition were examined using a regional data set (the Competition Omission Monitoring Project) that documents loblolly pine (Pinus taeda L.) plantation development for 15 years after early intensive woody and (or) herbaceous control. Examined were trends for macro nutrients in soils sampled at years 0 and 15 and in pine foliage at years 2, 6, and 15 and their correlations with one another and with pine growth. Early control treatments resulted in distinct plantation successional patterns with contrasting herbaceous and woody components, all under pine-dominated canopies. There was an overall decrease in soil nutrient concentrations after 15 years of pine-plantation management, while C, N, and Ca decreased most after vegetation control. Early herbaceous treatments resulted in significantly less foliar N and K at year 15 as well. Foliar nutrient contents and fascicle mass at year 2 tended to be better correlated with year-15 pine volume than values at year 6 or year 15. Year-15 P concentrations had the strongest correlations between soil and foliar nutrient levels (r = 0.71–0.77). By year 15, intensive pine culture and vegetation control had placed demands on soil nutrient supplies to support enhanced growth that have not yet been replaced.