Effects Of Ground Mosses Removal On Soil Organic Carbon In Two Types Of Forest In Yunnan

Soil carbon pool is one of the most important carbon pools in terrestrial ecosystems.The minimal changes of soil carbon pool would strongly affect global climate.The cyclings of carbon and nitrogen interact with understory plants in forests,it is important to investigate effects of these interactions on soil carbon storage.Therefore,a subtropical evergreen broad-leaved forest and a cold-temperate coniferous forest were selected in this study.After removing the ground bryophytes,we studied the soil physical and chemical,soil organic carbon(SOC)and the characteristics of microbial phospholipid fatty acids(PLFAs),to provide a scientific basis for the carbon and nitrogen cycles of forests.The main results are as follows:(1)The removal of ground bryophytes resulted in a significant increase in soil bulk density(P<0.05),and soil bulk density increased with soil depth(P<0.01).After removing the moss,the soil water content of each soil layer of the broad-leaved forest decreased.The soil water content of each layer of coniferous forest increased(P>0.05).The soil water content decreased with the deepening of the soil layer(P>0.05).Removal of moss caused the temperature of the ground soil to rise,the soil temperature of the broad-leaved forest increased by 1.1 ?(P<0.01),and the soil temperature of the coniferous forest increased by 0.8 ?(P>0.05).After removal treatment,the pH value increased in the 0?10cm soil layer,but decreased in the 10-20cm soil layer(P>0.05),and the pH value increased as the soil layer deepened(P<0.01).(2)After removing the moss,in the broad-leaved forest,the total PLFAs,bacterial PLFAs,Gram-positive PLFAs,fungal PLFAs,anaerobic PLFAs,prokaryotic PLFAs,and bacterial/fungal ratios were reduced in each soil layer,and the AM fungi PLFAs content and G'/G+ ratios increased.But there has no significant effect(P>0.05).The total PLFAs,bacterial PLFAs,Gram-negative PLFAs,AM fungi PLFAs and G-/G+ ratios in coniferous forests decreased in all soil layers,and there was no significant effect(P>0.05).At the same time,Gram-positive bacteria PLFAs,anaerobic PLFAs,actinomycetes PLFAs,and protozoa PLFAs increased,and anaerobic PLFAs showed significant effect(P<0.05).The SOC contents of the two types of forest were significantly positively correlated with the contents of total PLFAs,bacterial PLFAs.Gram-negative PLFAs,fungal PLFAs,and AM fungi PLFAs.In the broad-leaved forest,TN content showed a very significant positive correlation with the total PLFAs.bacterial PLFAs,Gram-negative PLFAs,fungal PLFAs,and AM fungal PLFAs.The C/N ratio was significantly positively correlated with the content of total PLFAs and bacterial PLFAs,and was significantly positively correlated with the content of fungal PLFAs.The correlation between SOC content,C/N ratio and microbial PLFAs content is almost the same.However,there is a significant difference in the correlation between TN content and microbial PLFAs content.Therefore,if moss removal has different effects on the soils of the two types of forests,N element might be an important factor.(3)Moss removal reduced DOC content(P>0.05),and DOC content decreased with soil depth(P>0.05).The SOC content decreased by 13.74 g·kg-1 to 41.08 g·kg-1,and the SOC content decreased by 8.68%to 19.41%.Moreover,significant effects indicated by three-way ANOVA statistics.(P<0.05),but the SOC content of the 10-20 cm soil layer of broad-leaved forest increased by 0.53 g·kg-1.At the same time,the SOC content decreased with the increase of soil layer,and the 0?10 cm soil layer was 2.?2.68 times of the 10?20 cm soil layer(P<0.01).The soil TN content decreased by 0.03 g·kg-1?0.46 g·kg-1,which decreased by 1.48%?11.16%(P>0.05),but the TN content of 0-10 cm soil layer of coniferous forest increased by 1.48 g·kg-1.The TN content of broad-leaved forest decreased with the deepening of the soil layer,and the 0?10 cm soil layer was 113.57%?123.27%higher than the 10?20 cm soil layer(P<0.01).The TN content in the CK group of coniferous forest,0?10 cm soil layer is 55.25%of the 10?20 cm soil layer.The TN content of the MR group,0?10 cm soil layer is 106.01%(P<0.01)in the 10?20 cm soil layer,The C/N ratios decreased by 2.65%to 21.64%(P<0.01),but the C/N ratios of the 10-20 cm soil layer of broadleaf forest increased by 1.570/%.The C/N ratios decreased with the deepening of the soil layer,and the 0?10 cm soil layer was 1.16?3.60 times of the 10?20 cm soil layer(P<0.01)Pearson correlation analysis showed that the SOC content of broad-leaved forest was significantly positively correlated with TN content,and positively correlated with C/N ratio.The SOC content of coniferous forest was significantly positively correlated with C/N ratio.Therefore,the mosse removal of two types of forests is likely to improve the availability of soil N elements,promote the mineralization of SOC,and reduce SOC content.