三峡水库消落区典型草本植物氮、磷养分计量特征

为明确消落区土壤养分对植物生长的影响,通过室内栽培试验,研究三峡库区秭归消落区土壤3种氮磷水平下4种草本植物—鬼针草(Bidens pilosa)、苍耳(Xanthium sibiricum)、水蓼(Polygonum hydropiper)、藜(Chenopodium album)长势及氮、磷计量特征.结果表明,消落区土壤中生长的植物氮含量为7.98~19.4 mg/g,磷含量为0.740~3.880 mg/g,氮磷比为3.48~13.70,判别植物生长受氮限制.外源氮磷的添加促进植物氮、磷含量明显升高,但氮磷比没有明显变化;外源氮磷添加解除植物受氮的限制作用.4种植物对消落区土壤低氮环境具有一定的适应能力.比较消落区土壤中4种植物长势,鬼针草生物量、相对生长率、根茎生物量比最高,氮磷养分丰富对鬼针草生长促进作用最明显,表明鬼针草更易于在氮、磷贫乏的三峡库区消落区形成优势群落.

Nitrogen and phosphorus stoichiometry characteristics of typical herb plants in the water-fluctuation-zone of Three Gorges Reservoir

Nitrogen (N) and phosphorus (P) availability limit plant growth in most terrestrial ecosystems. Plastic responses of plants to N and P supply cause variation in biomass and N/P ratios, associated with differences in root allocation, nutrient uptake, biomass turnover and reproductive output. We investigated the growth characteristics and nutrients acquirement of four dominant herb plant species (Bidens pilosa, Xanthium sibiricum, Polygonum hydropiper, and Chenopodium album) sampled from Zigui water-fluctuation-zone of Three Gorges Reservoir by pots cultivation at three N and P levels. In the process of plant growth, we determined plant biomass and nutrient contents of plant tissues. N contents of plant growing in soil ranged in 7.98-19.4 mg/g, and P, ranged in 0.740-3.880 mg/g, and N/P, ranged in 3.48-13.70, which indicated that plants were under N limitation. After N & P supply, N and P contents increased significantly, and plant growth were not limited by N. By comparing the growth characteristics of 4 plant species in soil, the following results were obtained. B. pilosa had significant higher biomass, relative growth rate and root/shoot biomass ratio. After N & P supply, B. pilosa growth were promoted significantly. B. pilosa would be dominant community in soil of poor nutrient level in water-fluctuation-zone of Three Gorges Reservoir.