Decomposition Characteristics In Decomposition Process Of Pinus Armandii Coniferous Litter At Erlangshan Mount, And Indoor Decomposition Experiment

Pinus armandii Franch. is an important constructive species of subalpine forest. It plays an important role in maintaining the richness and diversity of forest ecosystem. At present, the studies about the litter in subalpine forest are still lacking, especially no litter decomposition about P. armandii had been reported. In this study, the P. armandii litter was chosen as the object to conduct a decomposition test using in situ litterbags. The fungal community, nutrient return and the characteristics of enzymes in the process of decomposition were researched in subalpine region from September 2012 to August 2013. In addition, it was rare research on the saprophytic of the pathogen Lophodermium spp. in Pinus needles. Until now, at least 12 species of Lophodermium spp. had been reported. Their decomposition ability was explored by the artificial culture in the decomposition experiment. The main results of this study were as follows:(1) Fungis were isolated and identified using in situ litterbag in September 2012 (autumn), December 2012 (winter), March 2013 (spring) and June 2013 (summer), respectively. The results showed that 54 genera and 77 species were isolated from 4 sampling plots, including 15 genera and 35 species from autumn,17 genera and 33 species from winter,21 genera and 43 species from spring,37 genera and 54 species from summer. In addition, fungal community at each elevation showed obvious phenomenon of succession. Allantophomopsis sp., Penicillium sp. and Mucor sp. could be isolated from the litter at four sampling plots. It was worth mentioning that the relative frequency of Allantophomopsis sp. and Penicillium sp. were high. So the three genera existed widely in the litter layer under the P. armandii. Meanwhile, the fungal community in the decomposition of litter changed with the season and litter quality.(2) The decomposition characteristics and the nutrient release pattern were studied by situ litterbags from September 2012 to August 2013 at four elevations. The results showed that the final mass loss rate of litter differed as below:2650 m>2510 m>2460 m>2750 m. According to the Olson negative exponential attenuation model, the time that losing 95% of initial mass required as follow:2650 m<2510 m<2460 m<2750 m. In the decomposition, it was obvious enrichment on element N and net release on element P. However, element K changed as "release-enrichment-release" pattern. Organic carbon presented a release status on the whole. The content of nitrogen, phosphorus, cellulose, lignin and the ratio of C/N and L/N were the important indicators to the decompisiton rate of litter.(3) The seven kinds of enzymes measured in the decomposition showed obvious seasonal changes. The activity peak of endoglucanase appeared not only in the winter, but also in spring and summer, and it was relatively high in spring. The peak of catalase activity appeared in spring. Peroxidase’s peak appeared in autumn and winter. The peak of acid phosphatase activity appeared in autumn, winter and summer. And in autumn and winter, the activity was higher than summer. The peak of xylanase, sucrose and polyphenol oxidase activities appeared except winter. The activity of sucrose was higher in autumn. According to the correlation analysis, it existed a directive function of each enzyme on the nutrient release pattern. For example, xylanase, acid phosphatase and peroxidase had directive function on the release pattern of phosphorus. Xylanase also had function on element potassium. In addition, xylanase and acid phosphatase had directive function on the release pattern of element potassium and nitrogen, respectively. But there was no obvious difference about the activities of the enzyme among the elevations. In general, hydrolytic enzymes differed as follows:2750 m<2510m<2650 m<2460 m. And oxidordeuctase differed as follows:2750 m<2460 m<2510 m<2650 m.(4) Five species of Lophodermium were cultivated according to the vitro culture method while the needles were used as the sole carbon source. The results showed the mass loss rates caused by five species of Lophodermium spp. were between 8.5-11.8%, and declined in the following order:L. pinastri>L. sichuanicum> L. kumaunicum>L conigenum>L. erlangshanense. The correlation analysis showed that there was a certain synergistic effect among EG, CBH and BGL (except L. pinastri and L. erlangshanense), especially between CBH and EG. Cellulose decomposing was influenced by the enzyme activities, which showed that the litter needles were decomposed faster along with strong synergistic effect and high enzyme activity. The five species of Lophodermium spp. could produce cellulase, and there were different synergistic effect among EG, CBH and BGL during the degradation. The five strains had certain ability to decompose the needles, and they were facultative parasites, and had weak saprophytism.