Stand dynamics over 18 years in a southern mixed hardwood forest, Texas, USA

Abstract

Summary1 Using 18 years of permanent-plot data from a 4-ha stand, we investigated whether stand dynamics is predictable, i.e. driven by competition (inferred from species shade tolerances), or unpredictable (driven by frequent exogenous disturbance or other factors). We also considered whether small disturbance might accelerate or retard succession. The study involved dynamics of stems ≥ 4.5 cm diameter at breast height (d.b.h.) for 10 important species in a southern mixed hardwood forest 80 years after selective removal of Pinus taeda. 4 Over 18 years, ingrowth exceeded mortality loss slightly, resulting in an increase in number of stems of about 1%, from 995 to 1029 stems ha − 1 ; average live basal area (BA; 35.9 m 2 ha − 1 ) varied by less than 2% over eight surveys spanning 18 years. Basal area increased substantially for three species ( Ilex opaca , Pinus taeda , Acer rubrum ), and declined strongly for three others ( Quercus nigra , Q. hemisphaerica and Fagus grandifolia ). 5 The stand d.b.h. distribution had a rotated sigmoid form which became flatter over time. Species d.b.h. distributions were mostly bell-shaped for intolerant species, and irregular-to-monotonic declining for shade-tolerant species. Over time, bell-shaped distributions moved to the right and irregular distributions remained irregular. 6 A hurricane in 1986 caused loss of 4.5% of standing BA. Compositional change was most rapid during the hurricane interval and ingrowth was highest in the two intervals following the hurricane. Effects on species trends in density, basal area, mortality or recruitment were minor. 7 Temporal trends in species abundances mostly supported the hypothesis of predictable successional change related to competition for light. However, d.b.h. distributions of shade-tolerant species and rapid declines in BA of Quercus nigra and Fagus indicated that other processes are also important and will limit predictability of change.

Mid-successional stand dynamics in a cool-temperate conifer-hardwood forest in northern Japan

“…The mortality of several shade-tolerant species was less than the recruitment (i.e., increase in density), and vice versa for shade-intolerant species (i.e., decrease in density) in a temperate hardwood forest . A similar pattern was also recognized in a southern temperate forest in Texas, USA, where tree densities of shade-tolerant and shade-intolerant species increased and decreased, respectively, during 18 years (Harcombe et al 2002). These long-term studies suggest that these stands were developing with the reduction of tree density, especially for shade-intolerant species.…”

Woody plant composition of forest layers: the importance of environmental conditions and spatial configuration

“…For each stand, we inventoried all woody individuals in a 400-m 2 square plot (Harcombe et al 2002), as this area corresponds to the optimal plot size established in these forests for woody species. The inventories were made for four forest layers: field layer (\1.30 m), shrub (1.30 B height \ 7 m), coppice (7 B height \ 15 m), and canopy (C15 m height).…”

Mortality, recruitment and growth of the tree communities in three forest formations at the Panga Ecological Station over ten years (1997-2007)

“…Such studies can contribute to the prediction of forest growth and productivity, facilitating the implementation of management programs, as well as promoting the rational use and recovery of tropical forests (Carey et al 1994). The changes that occur over time in tropical forests, in terms of their composition and structure, are the product of internal processes, such as competition for light (Harcombe et al 2002), and external processes, such as climatic, geological and anthropogenic changes (Condit et al 1992).…”