Effect Of The Forest Gap On Water Soluble And Organic Solvent Soluble Components During Foliar Litter Decomposition In An Alpine Forest

Litter decomposition play an important role in the cycling of nutrient and energy in the forest ecological system, Water soluble and organic solvent soluble components of foliar litter is one of the important parts of litter decomposition process. However, forest gaps could regulate water soluble and organic solvent soluble components dynamics during litter decomposition by changing the frequency of soil freeze-thaw cycles in winter and hydrothermal environment in growing season, but little information has been available on. Therefore, a field litterbag experiment was conduct in an alpine forest in western Sichuan, China from 15 November 2012 to 29 October 2014. Foliar litter of typical arbor species (birch:Betula albo-sinensis, cypress:Sabina saltuaria, larch:Larix mastersiana and fir:Abies faxoniana) and shrub species (willow:Salix paraplesia, azalea: Rhododendron lapponicum) were selected. Samples of air-dried foliar litter were filled in nylon litterbags and placed on the forest floor with 2 cm spacing between litterbags from gap center, canopy gap edge, extended gap edge to closed canopy in the alpine forest. The litterbags were sampled at snow formation stage, snow cover stage, snow melt stage and growing season in the two years of decomposition. The determination of water soluble and organic solvent soluble components from foliar litter will contribute to know the work of forest gap in the cycling of nutrient and energy in the forest ecological system at alpine forest.After two years litter decomposition, content of water soluble components of six foliar litters kept a continue decreasing tendency. Water soluble components as a easy decomposition components loss rapidly, changes of water soluble components is different between different species, and influence by litter quality significantly. The loss of cypress is biggest is 28.81%, birch is minimum loss species(25.06%). However, canopy gap edge and closed canopy promoted the decrease of water soluble components contents of six foliar litters, but show different characteristics under different seasons. The content of water soluble components from six foliar litters increased at snow cover stage, and decreased at snow formation stage, snow melt stage and growing season in the first year of litter decomposition. But the second of litter decomposition, the content of water soluble components from six foliar litters increased in the winter, and decreased in the growing season.Chemical characteristics of soluble matters is different between different species, but water soluble components of foliar litter show different characteristics under different seasons. The content of water soluble carbon and water soluble organic carbon from six species foliar litter showed a similar dynamical tendency in the two years of litter decomposition. Both contents of water soluble carbon and water soluble organic carbon increased in the winter, and decreased in growing season, although the content of water soluble inorganic carbon decreased in the two years of litter decomposition. Meanwhile, the content of water soluble carbon and water soluble organic carbon loss biggest under same forest gap habitat, and both degraded more at extended gap and closed canopy, but water soluble inorganic carbon loss biggest under canopy gap edge and closed canopy. Moreover, Water soluble carbon of willow loss biggest under extended gap edge is 96.21%, but birch is minimum loss species(65.59%). The content of water soluble nitrogen and water soluble phosphorus in six species foliar litter have different changed trend after two years of litter decomposition. The content of water soluble nitrogen in six species foliar litter was reduced in the winter, and increased in the growing season at first year of litter decomposition, but decreased at snow cover stage, snow melt stage and growing season, and increased at snow formation stage at second year of litter decomposition. The content of water soluble of nitrogen increased significant under extended gap edge and closed canopy at snow formation stage. Besides, willow loss biggest under extended gap edge is 86.83%, but the content of water soluble of nitrogen from cypress and birch increased slightly under canopy gap edge is 6.84% and 36.17%, respectively. The content of water soluble phosphorus continued to decreasing in the two years of litter decomposition. The content of water soluble phosphorus from larch had biggest loss under closed canopy 96.23%, but cypress decreased minimum under canopy gap edge is 30.69%.The content of organic solvent soluble components from six foliar litters kept a continue decreasing tendency in the two years of litter decomposition. The effects of forest gap on the contents of organic solvent soluble components during litter decomposition controlled by litter quality. The changes of organic solvent soluble components from different species is different, the content of organic solvent soluble component from birch had minimum loss is 38.95%, and azalea had biggest loss is 65.66%. Alpine forest can form different habitant by forest gap, it would affect the content of total phenols, In addition, correlation analysis indicated that the content of organic solvent soluble component was negative related to negative accumulated temperature and frequency of freeze-thaw cycle. The content of organic solvent soluble component from birch, azalea and larch had loss biggest at gap center, and willow, cypress and fir had loss biggest under closed canopy, canopy gap edge and extended gap edge, respectively. The content of total phenols continued to decreasing in the two years of litter decomposition. Relative to gap center and closed canopy, the content of total phenols from six foliar litter decreased significantly in canopy gap edge and extended gap edge. The content of total phenols from willow loss biggest under canopy gap edge is 89.08%, but birch had minimum loss at gap center is 61.42%.In summary, forest gap in alpine often change the pattern of the snow cover and form different thickness snow cover in the winter. While, will lead to hydrothermal environment different from gap center to closed canopy. This different habitat and litter quality could effect the content of water soluble and organic solvent soluble components. These results suggested that the ongoing winter warming would decrease the content of water soluble and organic solvent soluble components during foliar litter decomposition by decreasing the cover-time and thickness of snow in the winter, although the decrease degree could be controlled by litter quality. This study will provide the basis for the cycling of nutrient and energy in the forest ecological system, thus to further reveal the relationship between climate warming and water soluble and organic solvent soluble components during foliar litter decomposition.