| Deciduous broad-leaved forest is the zonal vegetation type in the temperate zone of Northern-central China. Oak (Quercus liaotungensis Koidz.) forests or those where oaks were dominant species used to distribute in this region. Currently it is difficult to find patches of oak forests in low hills and mountains because of anthropogenic activities or clear-cutting for cultivation. In some regions,shrubland,grassland or farmland have replaced oak forests widely. Throughout the world,oaks (Quercus spp.) usually have poor natural regeneration in the forests where they occur,and begin to be replaced by long-lived and more shade-tolerant species in the absence of periodic disturbance. It is urgent and important to restore the oak forest in such areas for environmental improvement,sustainable development and biodiversity conservation. To develop effective and economic techniques for restoration also requires the full understanding of natural regeneration processes and their limiting factors. To develop effective and economic techniques for restoration and to know Quercus liaotungensis Koidz. forest dynamics and community stability,it requires the full understanding of natural regeneration processes and their limiting factors,and of ecophysiological attributes of the early-successional vs late-successional plants. By field measuring and experiments in 1998-2000,we found that:1). Habitat is open and sunny at early-succession stage,the environmental factors are temporal heterogeneous,contrasting to more closed and stable at late-successional stage with more spatial heterogeneous. Seasonal soil water content was significantly lower,CO2 concentration changed more rapidly,PAR and air temperature incident on measured species were higher in shrubland. Diurnal air humidity fluctuation in shrubland was similar to that on top and sub-canopy in mature forest.2). Acorn germination increased from 43.4% to 61.6%,that seedling recruitment increased from 33% to 47.6% in gaps relative to those in oak forest understory. They also showed strong positive correlation with openness (R2=0.659,P=0.001 and RO.477,/M).034,respectively).3). Seedlings grew faster,taller and larger,flushed more in the first growingseason (90% and 20%),allocated more dry mass to root and stem diameter increment,with more vertical angle,lower SLA and higher stomatal density leaves in large and small gaps. Direct and diffuse light showed different effects on growth and allocation of oak seedlings in the understory by canonical discriminate analysis. Stem base diameter is a better nondestructive index in response to light availability. No positive significant relation of growth and seedling survival was found in the first year,but the larger seedling survived better in the second year. Light compensation point (LCP) and saturation light point (LSP) of oak seedling increased with light,contrasting to decrease of respiration and quantum efficiency. While the highest A occurred in large gaps,A,was a little lower in open sites because of photoinhibition. Stomata density,inside aperture and stomatal index showed significant positive correlation to light availability.4). Both acorn germination and seedling recruitment were improved in order in burying treatments as:placed on litter |
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