Response Of Quantitative Properties Of Peatland Sphagnum Spore Banks To The Gradient Of Latitude In Eastern China

In natural ecosystems,plant sexual propagule banks play a role in maintaining population regeneration and community species diversity,and their quantitative characteristics are strongly affected by geographical factors such as temperature and precipitation.As the dominant plant in most peatlands,Sphagnum is widely distributed in China from the cold temperate zone to the subtropical zone,and can form long term persistent spore banks.However,up to now,the geographical differences of spore banks at the regional scale have not been reported.In this study,12 peatlands were selected to study the response of quantitative characteristics of Sphagnum spore banks in Eastern China to the latitudinal gradient across the cold temperate zone,middle temperate zone and subtropical zone.A peat corer was used to drill peat profiles of hummock habitats.The spore density,spore germinability and spore bank density were measured and cultured in the artificial climate chamber.Through the establishment of depth-age model,calculate burial time of each layer Sphagnum spore,and establish the Sphagnum spore germinability and burial time curve fitting prediction Sphagnum spore half-life(the burial time when 50%spores are viable)and longevity(the burial time when1%spores are viable).The results and conclusions are as follows:(1)A total of 411-45429 spores were observed in peat profiles of 12 peatlands.According to the comparison of different peatlands with the same burial time,the spore densities in the northern cold temperate Mangui peatland with the latitudinal gradient were the highest,which were 136�19.6 spores�cm^-3 and 238�12.4 spores�cm^-3,respectively,in the last 50 and 100 years of burial.The spore density in the subtropical Anji peat profile was the lowest,with 1�0.2 spores�cm^-3 and 2�0.1 spores�cm^-3,respectively.Statistical analysis showed that spore density increased with the increase of latitude.(2)At the same burial time,the Sphagnum spore accumulation rate in the Mangui peat profile in cold temperate region was the highest,44.6�6.6 spores�cm^-2�r^-1 and 92.6�29.9spores�cm^-2�r^-1,respectively.The Sphagnum spore accumulation rate in the Tangbei peat profile was the lowest,1.4�0.2 spores�cm^-2�r^-1 and 1.3�0.1 spores�cm^-2�r^-1,respectively.The Sphagnum spore accumulation also increased with latitude.(3)Sphagnum spore germination was observed in peat profiles of 12 peatlands,but the germinability varied greatly from 0.3�0.3%to 97.3�1.4%.Mangui peatland had the highest Sphagnum spore bank density which was 3571�551 spores�m^-2,and Anji peatland had the lowest spore bank density which was 24�5 spores�m^-2.On the whole,spore bank density increased significantly with the increase of latitude.The longest-lived spore exists in the peat profile of Leigongping,and the Sphagnum spore buried for about 1574 years can still germinate.The model predicts that the Sphagnum spore longevity in Tangbei,Nanniangshan and Leigongping peat profiles can exceed 1000 years.Simple regression model analysis showed that the Sphagnum spore longevity increased with the increase of latitude,but the half-life of spore did not change significantly.(4)The results of multiple stepwise regression model showed that ash,N,moisture content,p H and ash-free bulk density were significantly negatively correlated with spore germinability.Structural equation model(SEM)analysis showed that the spore density decreased significantly with the increase of MAT and increased significantly with the increase of MAP.Spore density increased with the increase of the continentality,but there was no significant relationship.There was a negative correlation between MAP and spore bank density,and a positive correlation between MAT and spore germinability,indicating that spore germination caused by increasing MAT could deplete spore bank.The increase of MAP increased spore germination,but had no significant effect on spore bank density.Taken together,the quantitative characteristics of spore bank in the peatlands of Eastern China showed an obvious response on the latitude gradient,and the geographical pattern of the quantitative characteristics of spore bank was mainly controlled by the MAT.The differences of spore density,spore accumulation rate,spore bank density and spore bank persistence in the latitudinal gradient may be the result of the response to the differences in ecosystem stability.As the ecological"engineer"of peatlands,Sphagnum holds the ability to form long-term persistent spore banks which may play an important role for Sphagnum to regenerate in its old stands or colonize new habitats.