A Study On Twig And Leaf Traits Of The Shrub Species In Secondary Forest Succession Process

Relationship between plant twig and leaf traits is an important aspect of understandingthe physiological activity of twigs, and is important for understanding morphological changeand adaptation mechanisms of twigs and leaves. Taking the community and traits surveys oftwig and leaf of woodland shrub species in Qilian of Northwest China from2007to2012inAugust, the method of standardized major axis (SAM) estimation was used to study the twigand leaf traits of shrub species, the biological characteristics, soil moisture, nutrient variationof different successional stages of forest communities, changes in the relationship of twigsand leaves traits of different successional stages were quantitatively studied, furtherunderstanding the adaptation mechanism of shrub species in secondary forest land, andprovide basic data and scientific basis for comprehensively understand the rapid succession ofspecies turnover. The results showed that:(1) shrub species and biological characteristics of different forest communities existedsignificant differences in the recovery phase, as the succession, the height of shrubs, cover,richness showed an increasing trend; community woodland soil bulk density at differentsuccessional stages showed decreasing trend, while soil moisture, organic carbon, totalnitrogen, and carbon and nitrogen ratio showed an increasing trend. With the succession, theaverage crown exposure index shrub species tended to decrease; shrub species gradualtransition from drought-tolerant species to wet shade species.(2) branch length of secondary forest shrub species increases faster than the increase inthe number of leaves, leaf area increased faster than the branch length and stem weightincrease speed. In the process of restoration succession, with increasing of the twig length ofshrub species, the increasing of leaves in small branches more slowly, but the rapid increase inleaf area compensated the lack of fewer leaf sprig, collaborative relationship between theformation of such a trait foliage complex configuration system provide the woodland shrubspecies a stronge phenotypic plasticity.(3) on each successional stages,both leaf area (single leaf dry weight) and the weight ofthe leaf stem-based strength, and a single leaf area based on small branches and leaves out theheavy intensity showed a significant negative correlation relationship, indicating that the lowintensity correspond a larger leaf, on the contrary, it is small.(4) Within each successional stage, shrub species of twig mass with leaves and leaf mass and leaf petioles and leaf mass showed a significant positive correlation; twig mass withleaves and leaf mass was constant relationship, and the petiole and leaf mass and twig masswere allometric relationship, and petiole mass of leaves and twig increased faster than theincrease of mass. Whether twig mass with leaves and leaf mass, or between the petiole andleaf mass and twig mass; the y-axis intercept slope of later stage upward than the previousstage along the spindle. Indicating petiole has a significant impact on the distribution of twigbiomass, but little impact on the distribution of leaf biomass.In summary, with the succession, the soil moisture content, physical and chemicalcharacteristics and nutrient status gradually improved, the improved forest soil productivityprovided material basis for each trait size, number of plants, and escalating stratification leadby light stress shrub canopy, shrub species adjust twig-trade-off between leaf traits to adaptto changes in light of habitat, which leaves as the main photosynthetic organs, in order tomaximize its energy, the rapid increase in leaf area, but also induced plasticity in response tofurther support and conducting structures, including the petiole and effectively increase thesize of twigs and other traits. Covariant relations within the twig and leaf sprig traits lead tostronger phenotypic plasticity and ecological adaptability of woodland shrub species, fromdrought-tolerant shrub species to wet shade shrub species gradually in alternative process,.