水位变化对三峡库区消落带狗牙根种群营养特征的影响

Influence of water level on nutritional characteristics of Cynodon dactylon population in water-level-fluctuating zone of the Three Gorges Reservoir

为探讨三峡库区大尺度、反季节水位变化对消落带狗牙根种养元素吸收和分配特征的影响,分别测定了三个样带的营养元素含量。结果表明:根、茎、叶中大量元素含量顺序为N>K>P,中量元素含量顺序为Ca>S>Mg,微量元素为Fe>Zn>Cu>Mn。根系对K、Mg、S、Fe、Mn、Zn的吸收均被促进,而对P和Ca的吸收被显著抑制,低水位根系对N、Cu的吸收也被显著促进。高水位茎和叶中N、P、K、Mg、S、Cu的含量呈降低趋势,Ca、Fe、Mn含量呈显著增大趋势,且茎中Zn含量也呈增加趋势。随着水位的降低N、P、K、Mg、S、Zn含量显著增加,在叶片中的含量显著大于根、茎,而Fe、Mn、Cu表现出主要向茎分布的趋势,且Ca在叶中的分配显著被抑制,而在茎中的分配被促进。随着水位降低新叶中N、P、K、Mg、S的含量明显高于老叶,而Fe、Ca、Mn、Zn和Cu则相反。随着分枝级数增大N、P、K的含量呈递增趋势,Ca、Cu、Fe、Zn呈递减趋势,而Mg、S含量呈"∨"形变化。因此,库区水位已导致消落狗牙根种群营养特征发生显著的变化。

In order to discuss the influence of large scale and anti-season water level on nutrients absorption and distribution characteristics of Cynodon dactylon population in water-level-fluctuating zone of the Three Gorges Reservoir, nutrient element contents of three sample zones in low water level（150— 155 m）, high water level（165— 170 m） and the control（175— 180m） were determined in 2012. The contents of major elements in root, stem and leave were measured and N was the highest one, followed by K and P. Secondary elements and microelement also were analyzed and the content order was determined with Ca 〉S〉 Mg and Fe 〉zinc〉 Cu 〉Mn. The root absorption of K, Mg, S, Fe, Mn and Zn was promoted, while the absorption of P and Ca was significantly inhibited. Meanwhile, the root absorption of N and Cu was also observed to be significantly promoted in low-water-level-fluctuating zone. N, P, K, Mg, S, Cu contents of stem and leave in high water level showed a decreasing trend, while contents of Ca, Fe and Mn showed an opposite trend, as well as Zn. With the decrease of water level, the contents of N, P, K, Mg, S and Zn were increased significantly with lower contents in leave than those in root and stem. However, Fe, Mn, Cu mainly distributed in stem. Furthermore, Ca distribution in the leave was significantly inhibited, and its allocation in the stem was promoted. With the decreasing of water level, the contents of N, P, K, Mg, S in new leaves were observed to be larger than those in old leave, and Fe, Ca, Mn, Zn and Cu exhibited an opposite result. With the increase of branch series, the contents of N, P, K showed an increasing trend, but the contents of Ca, Cu, Fe, Zn were decreased significantly. Interestingly, the contents of Mg and S presented ＂∨＂ changes. This investigation indicates that water level had made nutritional characteristics of C. dactylon population incur significant changes in water-levelfluctuating zone of the Three Gorges Reservoir.