Element cycling in the dominant plant community in the Alpine tundra zone of Changbai Mountains, China

Element cycling in the dominant plant communities including Rh. aureum, Rh. redowskianum and Vaccinium uliginosum in the Alpine tundra zone of Changbai Mountains in northeast China was studied. The results indicate that the amount of elements from litter decomposition was less than that of the plant uptake from soil, but that from plant uptake was higher than that in soil with mineralization process released. On the other hand, in the open system including precipitation input and soil leaching output, because of great number of elements from precipitation into the open system, the element cycling(except N, P) in the Alpine tundra ecosystem was in a dynamic balance. In this study, it was also found that different organ of plants had significant difference in accumulating elements. Ca, Mg, P and N were accumulated more obviously in leaves, while Fe was in roots. The degree of concentration of elements in different tissues of the same organ of the plants also was different, a higher concentration of Ca, Mg, P and N in mesophyll than in nerve but Fe was in a reversed order. The phenomenon indicates (1) a variety of biochemical functions of different elements, (2) the elements in mesophyll were with a shorter turnover period than those in nerve or fibre, but higher utilization rate for plant. Therefore, this study implies the significance of keeping element dynamic balance in the alpine tundra ecosystem of Changbai Mountains.

Green manuring relocates microbiomes in driving the soil functionality of nitrogen cycling to obtain preferable grain yields in thirty years

Fertilizers are widely used to produce more food, inevitably altering the diversity and composition of soil organisms. The role of soil biodiversity in controlling multiple ecosystem services remains unclear, especially after decades of fertilization. Here, we assess the contribution of the soil functionalities of carbon(C), nitrogen(N), and phosphorus(P) cycling to crop production and explore how soil organisms control these functionalities in a 33-year field fertilization experiment. The long-term application of green manure or cow manure produced wheat yields equivalent to those obtained with chemical N, with the former providing higher soil functions and allowing the functionality of N cycling(especially soil N mineralization and biological N fixation) to control wheat production. The keystone phylotypes within the global network rather than the overall microbial community dominated the soil multifunctionality and functionality of C,N, and P cycling across the soil profile(0–100 cm). We further confirmed that these keystone phylotypes consisted of many metabolic pathways of nutrient cycling and essential microbes involved in organic C mineralization, N_(2)O release, and biological N fixation. The chemical N, green manure, and cow manure resulted in the highest abundances of amoB, nifH, and GH48 genes and Nitrosomonadaceae,Azospirillaceae, and Sphingomonadaceae within the keystone phylotypes, and these microbes were significantly and positively correlated with N_(2)O release, N fixation, and organic C mineralization, respectively. Moreover, our results demonstrated that organic fertilization increased the effects of the network size and keystone phylotypes on the subsoil functions by facilitating the migration of soil microorganisms across the soil profiles and green manure with the highest migration rates. This study highlights the importance of the functionality of N cycling in controlling crop production and keystone phylotypes in regulating soil functions, and provides selectable fertilization strategies for maintaining crop production and soil functions across soil profiles in agricultural ecosystems.

Metagenomic insights into the effects of submerged plants on functional potential of microbial communities in wetland sediments

Submerged plants in wetlands play important roles as ecosystem engineers to improve self-purification and promote elemental cycling.However,their effects on the functional capacity of microbial communities in wetland sediments remain poorly understood.Here,we provide detailed metagenomic insights into the biogeochemical potential of microbial communities in wetland sediments with and without submerged plants(i.e.,Vallisneria natans).A large number of functional genes involved in carbon(C),nitrogen(N)and sulfur(S)cycling were detected in the wetland sediments.However,most functional genes showed higher abundance in sediments with submerged plants than in those without plants.Based on the comparison of annotated functional genes in the N and S cycling databases(i.e.,NCycDB and SCycDB),we found that genes involved in nitrogen fixation(e.g.,nifD/H/K/W),assimilatory nitrate reduction(e.g.,nasA and nirA),denitrification(e.g.,nirK/S and nosZ),assimilatory sulfate reduction(e.g.,cysD/H/J/N/Q and sir),and sulfur oxidation(e.g.,glpE,soeA,sqr and sseA)were significantly higher(correctedp<0.05)in vegetated vs.unvegetated sediments.This could be mainly driven by environmental factors including total phosphorus,total nitrogen,and C:N ratio.The binning of metagenomes further revealed that some archaeal taxa could have the potential of methane metabolism including hydrogenotrophic,acetoclastic,and methylotrophic methanogenesis,which are crucial to the wetland methane budget and carbon cycling.This study opens a new avenue for linking submerged plants with microbial functions,and has further implications for understanding global carbon,nitrogen and sulfur cycling in wetland ecosystems.