Above- and below-ground biomass accumulation, production, and distribution of sweetgum and loblolly pine grown with irrigation and fertilization.

Abstract: Increased forest productivity has been obtained by improving resource availability through water and nutrient amendments. However, more stress-tolerant species that have robust site requirements do not respond consistently to irrigation. An important factor contributing to robust site requirements may be the distribution of biomass belowground, yet available information is limited. We examined the accumulation and distribution of above- and below-ground biomass in sweetgum (Liqrridambar sfyrac$lua L.) and loblolly pine (Pinus taeda L.) stands receiving irrigation and fertilization. Mean annual aboveground production after 4 years ranged from 2.4 to 5.1 ~g.ha-'.year' for sweetgum and from 5.0 to 6.9 ~g.ha-l.year-l for pine. Sweetgum responded positively to irrigation and fertilization with an additive response to irrigation + fertilization. Pine only responded to fertilization. Sweetgum root mass fraction (RME)in creased with fertilization at 2 years and decreased with fertilization at 4 years. There were no detectable treatment differences in loblolly pine RMF. Development explained from 67% to 98% of variation in shoot versus root allometry for ephemeral and perennial tissues, fertilization explained no more than 5% of the variation in for either species, and irrigation did not explain any. We conclude that shifts in allocation from roots to shoots do not explain nutrient-induced growth stimulations

Intensive Forest Management in the US South

Forest management profitability can be raised by increasing stand productivity, which comprises improving wood yields and quality. The United States of America provides a good example of intensive management techniques applied on large scale to substantially increase forest productivity. Experiences of the U.S. South's forestry sector provide evidence that research−based intensive growth technologies are the key factor in ensuring adequate wood supplies and in effectively promoting sustainable management of the region's forest resource. Management treatments such as applications of fertilizers and herbicides have yielded lard productivity increases to date. Genetic improvement also has yielded large productivity increases along with improving stem straightness, wood properties, and disease resistance. Modern timber growth technologies already make possible doubling or even tripling current pine growth rates, while research progress indicates that current growth technologies can be improved even further