How Physical Disturbance and Nitrogen Addition Affect the Soil Carbon Decomposition?

The decomposition of soil organic carbon(SOC)plays a critical role in regulating atmospheric CO_(2)concentrations and climate dynamics.However,the mechanisms and factors controlling SOC decomposition are still not fully understood.Here,we conducted a 60 days incubation experiment to test the effects of physical disturbance and nitrogen(N)addition on SOC decomposition.N addition increased the concentration of NO3-by 51%in the soil,but had little effect on the concentration of NH4+.N addition inhibited SOC decomposition,but such an effect differed between disturbed and undisturbed soils.In disturbed and undisturbed soils,application of N decreased SOC decomposition by 37%and 15%,respectively.One possible explanation is that extra N input suppressed microbial N mining and/or increased the stability of soil organic matter by promoting the formation of soil aggregates and incorporating part of the inorganic N into organic matter,and consequently decreased microbial mineralization of soil organic matter.Physical disturbance intensified the inhibition of N on SOC decomposition,likely because physical disturbance allowed the added N to be better exposed to soil microbes and consequently increased the availability of added N.We conclude that physical disturbance and N play important roles in modulating the stability of SOC.

Plant-soil feedback during biological invasions:effect of litter decomposition from an invasive plant(Sphagneticola trilobata)on its native congener(S.calendulacea)

Plant invasions can affect soil properties in the invaded habitat by altering the biotic and abiotic nature of soils through positive or negative plant–soil feedback.Litter decomposition from many invasive species enhanced soil nutrients,thereby decreasing native plant diversity and leading to further plant invasions.Here,we examined the impact of litter decomposition from an invasive plant(Sphagneticola trilobata)in a range of soils at varying depths on growth and physiology of its native congener(Sphagneticola calendulacea).We added litter from S.trilobata to each soil type at different depths(0,2,4 and 6 cm).Plants of S.calendulacea were grown in each treatment,and morphological and physiological parameters were measured at the end of the growing period.All soils treated with litter displayed increases in soil nutrients at depths of 2 and 4 cm;while most growth traits,leaf chlorophyll and leaf nitrogen of S.calendulacea decreased at the same soil depths.Therefore,litter decomposition from invasive S.trilobata resulted in a positive plant–soil feedback for soil nutrients,and a negative plant–soil feedback for growth in native S.calendulacea.Our findings also suggest that the effects of litter decomposition from an invasive plant on soils and native species can vary significantly depending on the soil depth at which the litter is deposited.Future studies should focus on plant–soil feedback for more native and invasive species in invaded habitats,and the effects of invasive litter in more soil types and at greater soil depths.