Abstract:Nitrogen deposition is serious in southern China and it has massively altered plant growth and root formation. Thus, we choose Schima superba, which is a wide spread and most resistant plant in southern China, to evaluate its responses to elevated nitrogen (N) deposition and disclose the root growth and nitrogen and phosphorus use efficiency is, or is not, affected by N addition.The experiment was set up in the glass house from March to November in 2011. Dissolved NH4NO3 was sprayed on one-year-old seedlings of three geographically diverse provenances of S.superba, which grow in the container with the forest barren soil. The three provenances were Hangzhou of Zhejiang, Jian'ou of Fujian and Xinfeng of Jiangxi. Four treatments of 0, 50, 100 and 200 kg N hm-2·a-1 were arranged. After five month treatment, the plant materials were harvest. The mineral composition was determined after analyzing the root morphological and architectural parameters. The data were analyzed using SAS statistical program. The results indicated that S.superba responded significantly to N addition and exhibited positive affection. The root biomass, total root length, average root diameter, root surface area and volume were increased by 33%-73%. At the same time, the length of root >0.5mm was increased most, and the root morphological changed into thicker and diastolic type. The correlation between nutrient absorption efficiency (NAE, PAE) and root total length, root volume, average root diameter and root surface area were increased with N concentration. In N100, the NAE was significant correlated with length of root >0.5 mm, whereas PAE was significant correlation with the length of root ≤0.5mm, 0.5-1.0mm and ≥1.0mm, respectively. NAE was significantly affected the PAE (r=0.8729, P<0.01), at the same time, the NAE and PAE was significantly correlated with the biomass of S. Superba (rNAE=0.4572, P<0.05; rPAE=0.4750, P<0.01). And they were finally affected by the growth of S. Superba. There were significant differences among provenances. Jian'ou of Fujian provenance had stronger developed root system and highest nitrogen and phosphors use efficiency. The root length, average root diameter, root surface area and volume were increased by 54% under low-level N addition. Low-level N addition increased root growth of Jian'ou, whereas it had more effect on the height and stem base diameter of Hangzhou of Zhejiang provenance, which increased 34% and 26%, respectively. And low-level N addition greatly promoted above-ground and root growth of Xinfeng of Jiangxi provenances, the seedling height, SBD and root biomass were increased by 44%, 33% and 49%. However, high level N addition inhibited the root growth of Xinfeng provenance. PAE and PUE of Hangzhou provenances were higher under N100 and N200 treatment, but they were increased under N50 and N100 in Jianou and Xinfeng provenance. NUE was decreased when N addition increased to middle-level. S. superba responded positively to N addition. The difference of root growth and morphological responsed to N suggest that N plays an important role on nutrient uptake. The seedling growth of S. superba is close related with soil nutrient availability and genotypes which is the adaptation of climate in provenance site.
