三峡水库消落带优势草本植物对土壤氮磷的吸收富集特征

Nitrogen and Phosphorus Absorption from Soil by the Dominant Herbaceous Species in the Water-Level-Fluctuation Zone of the Three Gorges Reservoir

三峡水库消落带春夏出露,植物生长茂盛,可能拦蓄提取大量库区营养盐,研究消落带植物对氮磷养分的富集特征及其种间差异将为三峡消落带高效截污植被的筛选与重建提供重要基础数据。本文通过三峡水库消落带实地调研,采集典型草本植物,测定生物量和养分含量,计算富集系数和养分累积吸收量,从生态计量角度分析种间差异。结果表明,(1)三峡水库消落带优势植物主要为草本植物,优势草本植物有苍耳、青蒿、籽粒苋、铁线蕨、鬼针草、水蓼、稗草、空心莲子草、狗牙根、牛鞭草等。地上生物量的种间差异显著,苍耳和青蒿的地上生物量最高,铁线蕨地上生物量最低。(2)不同种类草本植物的氮磷吸收富集能力差异显著,苍耳和水蓼的氮富集系数最高;狗牙根和青蒿对磷的富集系数最高,苍耳和青蒿氮磷累积吸收量最高。另据植物对氮磷的富集系数、累积吸收量和其地上生物量,可将消落带草本植物分为5类:强氮磷富集型(苍耳和青蒿)、氮富集型(籽粒苋)、磷富集型(狗牙根)、弱磷富集型(水蓼和空心莲子草)、弱氮磷富集型(稗草、鬼针草、铁线蕨和牛鞭草)。(3)若仅考虑植物对消落带土壤(底泥)的养分吸收,强富集型和富集型植被具有更强的光合吸收提取效率,生态截污能力强,因此,消落带截污植被恢复草本可选苍耳、青蒿、籽粒苋、狗牙根等。

Grass grew vigorously and might retain large amount of nutrients during spring and summer in the exposed bottom of water-level-fluctuation zone (WLFZ) of the Three Gorges Reservoir (TGR). Research on plants species absorption capacity and their interspecific differences of soil nitrogen (N) and phosphorus (P) would provide important preliminary data for screening and rebuilding vegetation with high efficiency of pollutant interception in the TGR. In this study, ten dominant herbaceous plant species were collected for analysis of nutrients enrichment coefficient (EC) and absorption efficiencies. Influence factors of different absorption capacity among the species were analyzed by ecological stoichiometry methods. Results showed that, the dominant herbaceous plants were Xanthium sibiricum Patrin Widder, Herba Acroptili Repentis , Amaranthus tricolor L., Cynodon dactylon (L.) Pers., Echinochloa crusgalli (L.) Beauv ., Bidens pilosa L., Adiantum capillus-veneris L. and Hemarthria altissima ( Poir.) Stapfet C.E.Hubb in the WLFZ of the TGR. Aboveground biomass showed a significant difference among plants species while Xanthium sibiricum Patrin Widder s biomass was higher than other species. Moreover, there were significant differences of nutrients absorption ability among those dominant herbaceous plant species in the WLFZ. Xanthium sibiricum Patrin Widder was the specie with highest nitrogen EC, highest nitrogen and phosphorus cumulative uptake quantities. While Cynodon dactylon (L.) Pers got the highest phosphorus EC. The ten dominant plants were classified into five types by plants enrichment coefficient, cumulative uptake quantities and above-ground biomass. Xanthium sibiricum Patrin Widder and Herba Acroptili Repentis were classified into a strong nitrogen and phosphorus enrichment group;Amaranthus hypochondriacus L. was in strong nitrogen enrichment group;Cynodon dactylon (L.) Pers. belonged to high phosphorus enrichment type;Polygonum hydropiper , Alternanthera philoxeroides (Mart.) Griseb. fell a relatively weak nitrogen enrichment type;Echinochloa crusgalli (L.) Beauv ., Bidens pilosa L., Adiantum capillus-veneris L. and Hemarthria altissima ( Poir.) Stapfet C.E.Hubb were attached to low nitrogen and phosphorus enrichment group. Regarding to nutrients uptake capacity, Xanthium sibiricum Patrin Widder, Herba Acroptili Repentis , Amaranthus hypochondriacus L. and Cynodon dactylon (L.) Pers. might be recommended as species for the ecological restoration in the WLFZ due to their higher phytoextration efficiency.