Effects Of Tree Species Diversity On Litter Decomposition Rate And Nutrient Release

Litter decomposition plays an important role in forest ecosystems,and litter are usually decomposed in the form of mixtures in the natural environment;the importance of diversity to ecosystems is significant,but the study on the decomposition process of combination of different tree species in its corresponding stand environment and the role of species diversity and functional diversity in the process were rarely reported.The experimental plot is located in Longyan national modern forestry demonstration area(24°56′N,116°31′E)in Longyan City,Fujian Province.Based on the "Forest biodiversity,tree traits and ecosystem function experiment under global changes",established by our research team in 2019,this study selected 8 tree species: Liquidambar formosana Hance、Mytilaria laosensis Lec.、Hovenia acerba Lindl.、Acer palmatum Thunb.、Quercus variabilis Blume、(Lithocarpus glaber(Thunb.)Nakai)、Castanopsis sclerophylla(Lindl.et Paxton)Schottky、and Pinus massoniana Lamb.as the research objects and established three richness levels of tree species(1,4 and 8)including 8 pure forests with single tree species,4 mixed forests with different 4-tree-species combinations,and 1 mixed forest with an 8-tree-species combination with 4 replicates for each stand.The withered leaves in the bag in different decomposition periods were set up in 13 research plots of different stands using the litter bag method.By comparing the effects of the diversity of different tree species and the richness of different tree species on the decomposition rate and nutrient remaining rate,the rate change during the decomposition process could be assessed;it could be determined whether there is synergistic decomposition or antagonistic decomposition in the decomposition process;moreover the factors on the decomposition of litter could be identified in analysis of the different types of factors(soil factors,growth factors,litter quality factors,functional diversity index)in the sample plot.The main conclusions are as follows:(1)The litter decomposition rate of different tree species richness was significantly different after one year.By comparing the expected value with the observed value,the decomposition rate exhibited both inhibition and improvement in the process the decomposition;The average decomposition rate of litter of single tree species was the fastest,which was 8.6% faster than that of 4 tree species,3.5% faster than that of 8 tree species,and 4.7% faster than that of 4 tree species.In addition,there are also significant differences in decomposition rate after one year of decomposition of a single tree species.Among the litter of single tree species,the quality remaining rate of Hovenia acerba Lindl.was the lowest,significantly lower than that of other single tree species.The quality remaining rate of Quercus variabilis was the highest in the single tree species group,and the difference was over 30%.The actual decomposition rate of the two groups was significantly lower than the predicted value,which reflected the antagonistic non additive effect;the actual decomposition rate of the other two groups of four tree species was greater than the predicted value,but the difference was not significant.In the litter group of 8 species,the actual value was lower than the predicted value,but the difference was not significant.(2)The nutrient remaining rate of the litter of different tree species richness was different after one year’s decomposition.At the same time,there are difference between the expected value and observed value of the nutrient remaining rate after the mixed decomposition of multiple tree species.In terms of remaining rate of C,the combination of 4 tree species was the highest,which is 3.2% and 35.1% higher than the combination of single tree species and 8 tree species,respectively;in terms of remaining rate of N,the combination of single tree species was the highest,which is 6.5% and 1.8% higher than the combination of 4 tree species and 8 tree species,respectively;in terms of P remaining rate,the combination of 8 tree species was the highest,which was 4.3% and 21.1% higher than the combination of single tree species and 4 tree species,respectively;in terms of remaining rate of K,the combination of single tree species was the highest,which is30.9% and 18.1% higher than the combination of 4 tree species and 8 tree species,respectively;in terms of Ca remaining rate,the combination of 8 tree species was the highest,which is 15.1% and 9.1% higher than the combination of single tree species and4 tree species respectively;in terms of remaining rate of Mg,the single tree species is the highest,which was 16.7% and 36%,higher than the combination of 4 tree species and 8tree species;the result indicated that each nutrient had turnover in the process of mixed decomposition.In the litter of a single tree species,the remaining rate of each nutrient of Hovenia acerba Lindl.was the lowest,significantly lower than that of the other single tree species groups,which was consistent with the previous results of the decomposition rate;for trace elements such as Ca and Mg,retention process were observed.(3)In this study,the correlation between various factors on litter decomposition rate and nutrient remaining rate was analyzed,and the result showed that the initial quality of litter was significantly or extremely significantly related to the entire mixed decomposition experiment,and the functional diversity index,soil factors,growth factors had no significant effect on the decomposition,and the increase of tree species richness did not significantly accelerate the rate of litter decomposition significantly.The decomposition of litter in 2-3-year-old young forest was mainly affected by the quality of litter due to the growth of young trees and the opened canopy closure.