Responses Of Decomposition Of Flaveria Bidentis Litters To Simulated Nitrogen Deposition

Nowadays,biological invasion and enhanced nitrogen(N)deposition are key components of global change,but their interactive effects on litter decomposition are largely unknown.The aims of present study are to test whether the interactive effects of the two environmental factors on litter decomposition and nutrient loss are stronger than that of each factor alone.A litter-bag method was used to examine effects of nitrogen additions and soil burring on mass remaining and dynamic of N,C,and C/N of-leaf litters of invasive plant Flaverica bictentis and co-occurred native Setaria viridis during decomposition.Experiment included four treatments:elevated N deposition(100%enhancement,28 kg N ha-1 year-1),soil management(buried in 10 cm deep soil),the combined treatment of the two factors(N enhancement + soil buried),and the control.Meanwhile,both species and litter type were important factors affecting litter decomposition,and their effects can be moderated by external nutrient availability.Therefore,we conducted further study to assess whether increased N levels influenced decomposition rates and litter nutrient dynamics of foliage,fine roots,and twigs of an invasive plant,Flaveria bidentis.Results showed that the E bidentis litter decomposition constant k under nitrogen enhancement was 1.68,significantly decreased compared with that of the control(2.26),while enhanced N did not significantly differ for S.viridis.In contrast,soil burying tended to enhance significantly the leaf decomposition of both test species.Negative effects of N additions alone on decomposition of F.bidentis leaf litter were partly offset when combined with soil burying.The combination of N deposition and soil burying on litter decomposition and nutrient loss was significantly different from that of each factor alone but without a general response pattern of decomposition,and was regulated by litter chemistry derived from different species.Meanwhile,N fertilization significantly altered decomposition of invasive plant by decreasing its foliage decomposition rates more than 25%relative to controls,but did not alter decomposition rates of other litters.These discrepancies lead to a convergence of the decomposition constant towards similar values between foliar litters of both invasive and native species over the course of decomposition with N addition.Our study showed that the variation in litter decomposition was much greater between litter types than between different plant species upon N-fertilization,highlighting the importance of considering how litter traits in mediating ecosystem function.On the other hand,even fertilization with N caused litter quality to change,but not resulting in a higher nitrogen release across all litters,indicating that the direct effects of this fertilization level on decomposition through decomposer nutrient availability was more significant than the indirect effects through modifying litter quality in this region.We concluded that the lower decomposition rate constant of F.bitdentis litter might result in a greater increase in the litter C pool along the N loading compared with the native community alone,and that the litter buildup in F.bidentis-invaded sites is expected to increase its invasion success.With increasing N loading in future,belowground C pools were expected to become more crucial in forming the positive feedback of invasions on N cycling.Considering the possible positive effect of soil burying on litter decomposition and N release,litter removal was suggested to manage this invader by disrupting plant-soil feedback in its invasion process.