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Aims N deposition has become a major driver of a decline in species richness and biodiversity loss. We aim to discover whether N deposition could affect competitive relationships between poplars to predict threats posed by the introduction of exotic hybrids to native relative species.Methods Intra-and interspeci c competition was investigated for an introduced hybrid poplar (Populus beijingensis) and the native paternal species P. cathayana under two N deposition regimes (with and without N deposition).Results Under control conditions, P. cathayana grown under either of the competition modes showed consistently greater above-ground biomass, root-to-shoot ratio (R/S), photosynthetic capacity, higher activities of N-assimilation enzymes in leaves, and preference for N-NO 3 than corresponding P. beijingensis.Interspeci c competition increased the leaf area (LA), speci c leaf area (SLA), R/S, and photosynthetic nitrogen use e ciency (P NUE ) in P. cathayana, but decreased P NUE in P. beijingensis compared to the values under monoculture. Thus, P. cathayana can gain a competitive advantage over P. beijingensis at low N availability. In contrast, under N deposition, P. beijingensis grown in a mixture showed more positive responses in growth, higher plasticity in biomass allocation, more exible ne root traits, and the shift for N-NO 3 preference when compared with P. cathayana, which resulted in relatively higher values in LA, SLA, and biomass accumulation in P. beijingensis.Conclusions Our results suggest that N deposition could reverse competitive relationships between the poplars, and exotic P. beijingensis has the potential to outcompete and displace native P. cathayana under growing N deposition.

Aims N deposition has become a major driver of a decline in species richness and biodiversity loss. We aim to discover whether N deposition could affect competitive relationships between poplars to predict threats posed by the introduction of exotic hybrids to native relative species.Methods Intra- and interspecific competition was investigated for an introduced hybrid poplar (Populus beijingensis) and the native paternal species P. cathayana under two N deposition regimes (with and without N deposition). Results Under control conditions, P. cathayana grown under either of the competition modes showed consistently greater above-ground biomass, root-to-shoot ratio (R/S), photosynthetic capacity, higher activities of N-assimilation enzymes in leaves, and preference for N-NO3- than corresponding P. beijingensis. Interspecific competition increased the leaf area (LA), specific leaf area (SLA), R/S, and photosynthetic nitrogen use efficiency (PNUE) in P. cathayana, but decreased PNUE in P. beijingensis compared to the values under monoculture. Thus, P. cathayana can gain a competitive advantage over P. beijingensis at low N availability. In contrast, under N deposition, P. beijingensis grown in a mixture showed more positive responses in growth, higher plasticity in biomass allocation, more flexible fine root traits, and the shift for N-NO3- preference when compared with P. cathayana, which resulted in relatively higher values in LA, SLA, and biomass accumulation in P. beijingensis. Conclusions Our results suggest that N deposition could reverse competitive relationships between the poplars, and exotic P. beijingensis has the potential to outcompete and displace native P. cathayana under growing N deposition.

Abstract. For the development of fresh-keeping technology, strawberries were coated with different propolis concentrations of 1.5%, 2.0%, 2.5% and 3.0%. The effect and physiology on strawberries fresh-keeping was estimated by the decay index, weight loss rate, the soluble solid and titratable acid content. The result shows that propolis coating preservation treatment can significantly decrease the strawberries decay index and weight loss rate, and inhibit soluble solids and titratable acid content. It also delayed the aging process of postharvest strawberries notably, as well as prolonged strawberry fruits freshness. The preservation effect of strawberries coated with the propolis concentration of 2.5% and 3.0% are better, of which 3.0% is the best.