Decomposition Of Leaf Litters Mixed Eucalyptus Grandis With Alnus Formosana

Litter decomposition is the most important process in material cycling. Plantation ecosystem often displays relative slower litter decomposition rate due to simple structure with lack of biodiversity. How to improve the process of material cycling is always the key issue in maintaining the structure and function of plantation. It is assumed that the mixed littler decomposition could show higher decomposition rate compared with the decomposition of signal species because of the changed litter quality and decomposer diversity. However, the previous results were confused, and the relative process was unclear. Therefore, Eucalyptus grandis plantation was selected for its rapid development and large area. Litterbag method was used to study the leaf-litter decomposition mixed Eucalyptus grandis and Alnus formosana with different mixed proportion (10:0,7:3,5:5,3:7 and 0:10). The decomposition rate and the release rate of carbon, nitrogen and phosphorus. The results could be expected to provide scientific data for the construction of Eucalyptus grandis plantation. The results are followed.(1) During the whole decomposition periods, the decomposition rate displayed the order as:Eucalyptus grandis 3:7 Alnus formosana> Eucalyptus grandis 5:5 Alnus formosana>Pure Alnus formosana> Eucalyptus grandis 7:3 Alnus formosana>Pure Eucalyptus grandis. In the frist 120days,the decomposition rate in pure Eucalyptus grandis is 30.00%,39.47% in Pure Alnus formosana,48.94% in Eucalyptus grandis 3:7 Alnus formosana,39.69% in Eucalyptus grandis 5:5 Alnus formosana,37.34% in Eucalyptus grandis 7:3 Alnus formosana. Correspondingly, the theory data was 36.63% in Eucalyptus grandis 3:7 Alnus formosana,34.73% in Eucalyptus grandis 5:5 Alnus formosana,32.84% in Eucalyptus grandis 7:3 Alnus formosana. The decomposition rate was significant higher than the theory data. We can get such a conclusion that mixed-decomposition was faster than Pure Eucalyptus grandis which accelerated the decomposition of Eucalyptus grandis in the course of mixed-decomposition. (2) Similar as decomposition rate, the release rate of C, N and P showed the same order as:Eucalyptus grandis 3:7 Alnus formosana> Eucalyptus grandis 5:5 Alnus formosana>Pure Alnus formosana> Eucalyptus grandis 7:3 Alnus formosana>Pure Eucalyptus grandis.The C, N, Prelease rate was 33.21%,45.75%,37.10% in Pure Eucalyptus grandis,42.03%,58.07%,44.99% in Pure Alnus formosana,54.49%, 71.06%,8.86% in Eucalyptus grandis 3:7 Alnus formosana,46.05%,64.09%,50.06% in Eucalyptus grandis 5:5 Alnus formosana,43.49%,57.88%,45.40% in Eucalyptus grandis 7:3 Alnus formosana. Correspondingly, the theory data was 39.38%,54.56%,42.52% in Eucalyptus grandis 3:7 Alnus formosana,37.62%,52.28%,40.91% in Eucalyptus grandis 5:5 Alnus formosana,35.85%,49.96%,39.34% in Eucalyptus grandis 7:3 Alnus formosana. The release rate of C, N and P was significant higher than the theory data. We can get such a conclusion that mixed-decomposition accelerated the release rate of C, N and P in Eucalyptus grandis leaf litter in the course of mixed-decomposition. Eucalyptus grandis 3:7 Alnus formosana was fastest in three mixed leaf litter which accelerated the decomposition of Eucalyptus grandis in the course of mixed-decomposition.(3)The C/N and C/P did not show significant changes in the decomposition process, so that we can know that there were not great correlation in the different proportions. The C/N was range from 50.05-83.26. The C/P was range from 282.03-697.91. The initial C/N in different proportions (Eucalyptus grandis, Alnus formosana, Eucalyptus grandis 7:3 Alnus formosana, pure Alnus formosana, and pure Alnus formosana) was 59.80,50.05, 52.94,54.89,56.84. Correspond, the initial C/P were 663.58,282.03,344.85,431.35, 482.96. In the first 120 days, The C/N was 73.63,69.20,83.26,82.46 and76.27. The C/P was 697.91,297.72,386.29,441.09 and 502.20.In conclusion, the rates of decomposition and elements (C, N and P) release were higher in mixed litter compared with pure Eucalyptus grandis litter. However, significant differences were detected in the litter with different mixed proportions. Compared with the other mixed proportions, Eucalyptus grandis 3:7 Alnus formosana showed the relative higher mass loss rate and elements release rate. In addition, the mass loss rate and element release rate was only higher in pure Alnus formosana than pure Eucalyptus grandis and Eucalyptus grandis 7:3 Alnus formosana. The results suggested that the litter mixed Eucalyptus grandis with Alnus formosana could improve the decomposition each other. According to the results from litter decomposition, the plantation mixed Eucalyptus grandis with Alnus formosana could be the potential reasonable modification.