title: Nitrogen deposition cancels out exotic earthworm effects on plant-feeding nematode communities.
abstract: The activity and spread of exotic earthworms often are spatially correlated with N deposition because both arise from human activities. Exotic earthworms, in turn, can also greatly affect soil abiotic and biotic properties, as well as related ecological processes. Previous studies showed, for example, that earthworms can counteract the detrimental effects of plant-feeding nematodes on plant growth. However, potential interactive effects of N deposition and exotic earthworms on ecosystems are poorly understood. We explored the changes in density of plant-feeding nematodes in response to the presence of exotic earthworms, and whether these changes are altered by elevated N deposition in a two-factorial field mesocosm experiment at the Heshan National Field Research Station of Forest Ecosystem, in southern China. Our results show that earthworm addition marginally significantly increased the density of exotic earthworms and significantly increased the mass of earthworm casts. The total density of plant-feeding nematodes was not significantly affected by exotic earthworms or N deposition. However, exotic earthworms tended to increase the density of plant-feeding nematode taxa that are less detrimental to plant growth (r-strategists), while they significantly reduced the density of more harmful plant-feeding nematodes (K-strategists). Importantly, these earthworm effects were restricted to the ambient N deposition treatment, and elevated N deposition cancelled out the earthworm effect. Although exotic earthworms and N deposition interactively altered foliar N : P ratio in the target tree species, this did not result in significant changes in shoot and root biomass in the short term. Overall, our study indicates that N deposition can cancel out exotic earthworm-induced reductions in the density of harmful plant-feeding nematodes. These results suggest that anthropogenic N deposition can alter biotic interactions between exotic and native soil organisms with potential implications for ecosystem functioning.
authors.affiliation: Key Laboratory of Geospatial Technology for the Middle and Lower Yellow River Regions (Henan University), Ministry of Education, College of Environment and Planning, Henan University, Kaifeng, 475004, China.|Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, 510650, China.
authors.forename: Yuanhu
authors.identifier: 0000-0001-7950-5834
authors.initials: Y
authors.lastname: Shao
authors.affiliation: Key Laboratory of Geospatial Technology for the Middle and Lower Yellow River Regions (Henan University), Ministry of Education, College of Environment and Planning, Henan University, Kaifeng, 475004, China.|Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, 510650, China.
authors.forename: Weixin
authors.initials: W
authors.lastname: Zhang
authors.affiliation: German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Deutscher Platz 5e, 04103, Leipzig, Germany.|Institute of Biology, Leipzig University, Johannisallee 21, 04103, Leipzig, Germany.
authors.forename: Nico
authors.initials: N
authors.lastname: Eisenhauer
authors.affiliation: Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, 510650, China.|University of the Chinese Academy of Sciences, Beijing, 100049, China.
authors.forename: Tao
authors.initials: T
authors.lastname: Liu
authors.affiliation: Research Institute of Tropical Forestry, Chinese Academy of Forestry, Guangzhou, 510520, China.
authors.forename: Yanmei
authors.initials: Y
authors.lastname: Xiong
authors.affiliation: Zhejiang Provincial Key Laboratory of Carbon Cycling in Forest Ecosystems and Carbon Sequestration, Zhejiang A & F University, Lin'an, 311300, China.
authors.forename: Chenfei
authors.initials: C
authors.lastname: Liang
authors.affiliation: Key Laboratory of Geospatial Technology for the Middle and Lower Yellow River Regions (Henan University), Ministry of Education, College of Environment and Planning, Henan University, Kaifeng, 475004, China.|Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, 510650, China.
authors.forename: Shenglei
authors.initials: S
authors.lastname: Fu
mesh_terms: D000818:Animals; D002681:China; D017753:Ecosystem; D009348:Nematoda; D009584:Nitrogen / Q000378:metabolism*; D009835:Oligochaeta; D012987:Soil
chemical_list: D012987:Soil; D009584:Nitrogen
keywords: above-ground-below-ground linkages; below-ground biotic interactions; earthworm invasion; nitrogen deposition; plant-feeding nematodes; soil nematodes