Consequences Of Deficiency Plant Species Functional Groups For Stoichiometry During Litter Decomposition Across An Alpine Forest-tundra Ecotone

Climate change affects the change of biodiversity in ecosystems,which may lead to the deficiency plant species functional groups and have far-reaching significance for ecosystem functions and services,especially in mountain ecosystems.Litter decomposition,as one of the important functions of the ecosystem,affects the productivity of plants,and the effect of studying the species diversity of plant stoichiometric values has also received sufficient attention.In the research,mixed litter was used as a means to explore the mechanism of the deficiency plant species functional groups.Traditional viewpoints that the change of species richness may have a significant impact on litter decomposition,whereas recently studies have found that the functional type of litter species composition may be greater than that of species diversity to decomposition,emphasizing the interrelationship between species functional traits and ecosystems.The treelines of alpine forest can sensitively monitor the change of the global thermocline and has the potential to capture the climatic change effect.Therefore,based on an alpine forest-tundra ecotone in western Sichuan,we chosen 6 kinds of typical local plant functional group?9 species?as the research object,used a litterbag method to the effects of the loss of a dominant plant functional group on litter decomposition from 2015to 2017.The decomposition rate,mass loss,stoichiometric eigenvalues and dynamic changes of carbon components at different decomposition stages were detected.The effects of global climate change on plant litter decomposition are predicted through different elevation gradients.The results showed that:?1?The Olson classical exponential decay model shows that different treatments significantly affect mixing-litter decomposition rate?k?,k value of single species varies from 0.14 to 0.75 yr^-1,after species loss leaded to k value from 0.26 to 0.36 yr^-1.Altitude gradient significantly regulates the non-additive effect of plant species functional groups loss for litter decomposition rate.For instance,loss of ferns significantly decreased the non-additive effect of its decomposition rate,and higher altitude accelerated the decomposition rate.?2?The mass loss rate of litter mixing significantly affected in different periods and the mass loss rates from 35.07-47.03%,which was significantly higher in the first year,simultaneously,the growing season was higher than that in the non-growing season.The loss of evergreen shrubs will significantly accelerate the decomposition of litter in the transitional area,which also significantly affected by ferns?accelerate?and grass?decrease?in treelines during the studied.Mass loss rates caused by the species loss showed an antagonistic non-additive effect in litter mixing,which may be related to the positive correlation of C and negative correlation of C/N.The non-additive effects of mass loss rates were significantly controlled P and the loss of ferns will change the non-additive effect of litter decomposition in treelines.?3?The loss of different species showed that the carbon element was released?40.86%-55.05%?and the species mixed showed the antagonistic effect,which may be because the release of C occurred mainly in the first year after species loss.Nitrogen element is accumulation?-18.23%-2.11%?,and its non-additive effects are determined by the different single specie,for example,the loss of evergreen shrubs and arbors will accelerate the non-additive effect.The elevation gradient significantly controls the release of phosphorus element?31.49%-49.29%?after the loss of species during litter decomposition.As coniferous and treelines forest showed a synergistic and antagonistic effect,respectively,the loss of arbors,evergreen shrubs,ferns,and grasses could significantly affect P release in the area.?4?In general,the mixed litter compents degraded,with water-soluble substances?WSS?ranging from 35.15%to 56.06%;organic-soluble substances?OSS?from 2.79%to55.27%,acid-soluble substances?ASS?from 11.81%to 73.83%,acid-unhydrolysable residues?AUR?from-5.38%to45.43%.The loss of species significantly affected the changes of WSS.Similar to OSS,the amount of decomposition was large in the firstly year and accumulated in the later decomposition stage,while the ASS and AUR all showed degradation,the accumulation of ASS in the following year non-growing season,but AUR of the decomposition appeared early.Elevation gradients significantly regulate the non-additive effects of organic and water-soluble components,lower elevations directly lead to a synergistic effect on OSS,whereas loss of arbors,evergreen shrubs,and ferns can lead to synergistic non-additive effect of ASS and AUR during mixing-litter decomposition.In summary,temporal dynamics significantly effected litter decomposition when deficiency plant species functional groups.The water-soluble substances and organic-soluble substances were regradation firstly and the acid-unhydrolysable residues accumulated.The continuation of the decomposition,and the ragradation of acid-soluble substances continued to increase,and the corresponding acid-unhydrolysable was degradated.Deficiency plant species functional groups directly affect the main regulatory factors were transition from C,P to N and acid-unhydrolysable residues during the mixed litter decomposition.Different plant species and mixed treatments are significantly regulated by elevation gradients during litter decomposition.The daily average temperature and accumulated temperature significantly change the litter decomposition process after deficiency plant species functional groups.The effect of positive accumulated temperature is particularly significantly.A two-year study found that deficiency plant species functional groups were caused by biological diversity was significantly regulated by environmental factors and plant functional traits,emphasizing the importance of plant stoichiometric eigenvalues on litter decomposition.This has important implications for maintaining the biogeochemical cycle of the alpine forest ecosystem.It also provides a more comprehensive understanding of the impact of climate change on litter decomposition.