Understory plant response to site preparation and fertiliza- tion of loblolly and shortleaf pine forests

In developing an improved understanding of the dynamics of understory plant composition and productivity in Coastal Plaii forest ecosystems, we examined the iniluence of s i te preparat ion and phosphorus fer t i l izat ion on the success ional t rends of shrubs and herbaceous p lants growing on lands of wide ly ranging subsoil texture in Arkansas, Louisiana, and Texas which are managed for southern pine production. Burn-inject, chop-burn, chop-burn-disk, double-chop, shear-burn, shear-windrow, and shear-windrow-di sk s i te preparat ion methods were appl ied in a completely randomized spl i t -plot des ign to s i tes with subsoi l textures cons i s t ing o f loam, grave l ly -c lay , s i l t , s i l ty -c lay , and c lay , both fertilized with 73.4 kg P/ha and unfertlliied. Site preparat ion method, subsoi l texture, and fertilixation iniluenced production of paspalums and other forbs the fmt growing season following treatment, but no treatment combination affected plant groups in subsequent years. Total herbaceous production increased 24 to 35fold over pretreatment levels the llrst growing season af ter treatment . While s i te preparat ion methods had l i t t le intluence on herbaceous biomass , subsoi l texture af fected herbaceous production the first year aDer treatment, with loam subsoils being most productive. Although annual composites were the most abundant herbaceous group the first year after treatment, they were largely replaced by perennial grasses by the third post-treatment growing season. By the seventh growing season fol lowing treatment, herbaceous product ion decl ined on all subsoil textures with composition and yield approximating pretreatment est imates. Subsoi l texture inf luenced shrub densi ty The authors express their appreciation to Boise Cascade, Cavenham Forest Industries, Inc., Georgia Pacific Corporation, International Paper Company, Manville Forest Products Corporation, T.L. James and Company, Inc., Willamette Industries, USDA Soil Conservation Service and Kisatchie National Forest for contributions of personnel, resources and services in support of this study. We are also grateful to three anonymous reviewers for comments quite useful in improving this manuscript. Commerc ia l P roduc t s Di sc l a imer : The use of trade or fum names in this publication is for reader information and does not imply endorsement by the U.S. Department of Agricultum of any product or service. Pes t i c ide P recau t iona ry S ta t emen t : Pesticides can be injurious to humans, domestic and wild animals, and desirable plants if they are not handled or applied properly. Use all pesticides selectively and carefully. Follow recommended practices for the disposal of surplus pesticides and pesticide containers. Manuscript accepted 12 Jan. 1997. only in the first and third growing seasons after treatment. During the fmt few years af ter s i te preparat ion, herbaceous product ion appeared inversely re lated to shrub dens i ty . In the f irs t and third post-treatment growing seasons, fertilization significantly increased total herbaceous production and biomass of composites and legumes. But 7 years after application, total herbaceous product ion and biomass of b luestems, other grasses , and sedges was greater on unfert i l ized areas . The absence of diiferences among treatments by the seventh post-treatment growing season indicates an overal l long-term s imi lar i ty in the degree of disturbance caused by application of each method in this