| The Sphagnum wetland is a special wetland type formed by the swamping of Sphagnum and herbaceous plants.The amounts of carbon stored in Sphagnum wetland exceed the amounts of carbon fixed in all terrestrial plants each year,and The Sphagnum wetland play a key role in soil carbon accumulation.However,in the past half century,the rapid increase of atmospheric nitrogen deposition caused by industrial revolution and human activities has seriously changed the characteristics of nutrient-poor environment,the community composition,growth dynamics and litter decomposition of dominant plants in the Sphagnum wetland.Therefore,nitrogen deposition may have a profound impact on the Sphagnum wetland carbon sink function.At present,there are few reports on the effects of simulated nitrogen deposition on the growth and litter decomposition of dominant plants in a subtropical Sphagnum wetland.Therefore,Nylon bag method indoor analysis methods were used,two field decomposition and growth experiments of dominant plants after artificial nitrogen deposition was conducted in southwest of Hubei Province.and the Taishanmiao Sphagnum wetland is taken as the study area to answer the following scientific questions by observing and measuring the plant growth and decomposition indexes under different nitrogen treatments:How does simulated nitrogen deposition affect the growth of dominant plants and litter decomposition in the Sphagnum wetland in southwestern Hubei Province?The results showed that:1.Growing season,simulated nitrogen deposition has no effect on the increment of Enkianthus serrulatus base diameter and the plant height of Carex taliensis.Simulated nitrogen deposition has a certain effect on the plant height of Pteris wallichiana,but the effects of simulated nitrogen deposition on the plant height of Pteris wallichiana depend on the growth time.In May,plant height under N0 and N6treatments was significantly higher than that under N3 and N12 treatments.From June to September,plant height under N12 treatment was significantly lower than that under other treatments.In September,the plant height values among different nitrogen treatments were N3>,N0>N6>N12 in descending order.In addition,simulated nitrogen deposition can promote the aboveground biomass accumulation of vascular plants.The average aboveground biomass of CK was 27.75 g·m-2;aboveground biomass under N3 and N6 treatments was 3.7 and 3.4 times that of CK,respectively;and aboveground biomass of N12 was 1.7 times that of CK.The plants height of both Carex taliensis and Pteris wallichiana showed a trend of increasing first,then stable and then significantly decreasing with the growth time.2.Growing season,both simulated nitrogen deposition and decomposition time had significant effects on the growth height of Sphagnum palustre and Polytrichum commune,but the effect of simulated nitrogen deposition on the growth height of bryophytes depended on the growth time.At the same time,simulated nitrogen deposition had a significant effect on net production of Sphagnum palustre.At the end of the growth experiment,the average net production of sphagnum under N0,N3,N6and N12 treatments was 215.95 g·m–2?269.26 g·m–2?244.58 g·m–2?224.62 g·m–2respectively.Growth time had a significant effect on net production of Sphagnum palustre and Polytrichum commune.In brief,the growth time has a greater effect on the growth height of bryophytes.In addition,the growth pattern of Sphagnum palustre was different from that of Polytrichum commune.The growth height of Sphagnum palustre increased first and tended to be stable with time.The growth height of Polytrichum commune increased gradually with time.3.The initial chemical properties of the litter of the dominant plants in the Sphagnum wetland vary greatly.4.By the end 12-month period,simulated nitrogen deposition had no effect the mass remaining rate of vascular plant litter in wetland,and the decomposition rate of vascular plants litter varied significantly with different species.The average mass remaining rate of Pteris wallichiana was 79.59%,more than double that of 39.38%in Viburnum setigerum.Simulated nitrogen deposition has a certain effect on the decomposition of vascular plants litters,but it is not a simple promoting effect,and the decomposition time has a greater effect on the decomposition of vascular plants litters.5.After decomposition for one year,Simulated nitrogen deposition has a certain effect on the mass remaining rate of Sphagnum palustre and Polytrichum commune,but the degree of influence was different in different time periods.At the same time,simulated nitrogen deposition has a certain effect on ash content of litter,but the decomposition time has a greater effect and the relative ash content and absolute ash content of sphagnum litter increased significantly with the increase of decomposition time.In brief,simulated nitrogen deposition has some influence on the decomposition of vascular plants and bryophytes,but it not simply promote or inhibit the decomposition.The decomposition characteristics of litters of different species are determined by the genes of the species themselves.In conclusion,it was found that among the factors affecting the growth and litter decomposition of dominant plants in the sphagnum wetland,the degree of influence is as follows:species>(growth/decomposition)time>simulated nitrogen deposition. |
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