上海金泽水库典型挺水植物碳、氮、磷化学计量特征的季节变化

为探究不同水生植物碳(C)、氮(N)、磷(P)含量及其化学计量比随季节的变化特征,本研究以上海金泽水库库区四种典型挺水植物旱伞草(Cyperus alternifolius),芦苇(Phragmites australis),千屈菜(Lythrum salicaria),水葱(Scirpus validus)为例,开展了季节性取样及室内分析,结果显示:(1)四种植物碳氮磷含量的变化规律不同。其中,对于植物碳含量,旱伞草和芦苇均无显著差异,千屈菜和水葱仅在冬季显著降低。对于植物氮含量,除旱伞草外,其他植物均在春季生长初期显著降低,在夏季生长旺盛时期显著升高,而旱伞草四季无显著差异。对于植物磷含量,水葱在四季均无显著差异,芦苇和千屈菜在冬季植物休眠期显著降低,旱伞草和芦苇磷含量在夏季显著降低。(2)四种植物C/N/P的季节性变化特征不同。其中,旱伞草C/N四季间无显著差异,其他3种植物C/N在春季生长初期显著升高;在C/P方面,水葱四季间无显著差异,芦苇和千屈菜在春季显著降低,旱伞草和芦苇C/P在夏季显著升高;常绿植物旱伞草N/P在四季无显著差异,其他3种植物N/P均在冬季生物量低时显著升高,春季N/P显著降低,而夏季生物量增长时N/P显著升高。(3)季节变化对四种植物C、P、N/P的影响远大于物种差异的影响,而植物N、C/N、C/P受物种差异的影响程度略大于季节变化。(4)四种植物C/N和C/P分别与N和P呈显著负相关,表明植物C/N和C/P分别受N和P主导;植物C与N、P二者在夏、秋季均无显著相关性,表明起支撑作用的C元素在夏、秋季独立于起生化作用的N、P元素;而营养元素N、P二者含量仅在植物生长的春、夏季显著相关。综上所述,不同植物碳氮磷含量及其化学计量比的季节变化特征不尽相同。今后的研究,可结合相关的生境因子,更好地探究其变化的内在机理。

Seasonal variations of carbon, nitrogen, phosphorus stoichiometry of four emergent hydrophytes in Jinze Reservoir, Shanghai

In order to explore the seasonal variations of carbon(C), nitrogen(N) and phosphorus(P) content and their stoichiometric ratios of the hydrophytes, we chose four typical emergent hydrophytes, Cyperus alternifolius, Phragmites australis, Lythrum salicaria and Scirpus validus in Jinze Reservoir. The hydrophytes were collected and analyzed in the different seasons from October 2017 to June 2018. The results indicated that: (1) The C, N and P contents of the four hydrophytes varied in the different ways. The C content of C.alternifolius and P. australis didn''t show any significant variations among the four seasons, while that of L. salicaria and S. validus decreased significantly in the winter. The N content of the three plants except C.alternifolius decreased significantly in the early growing stage in spring and increased significantly in the summer, while that of C.alternifolius didn''t show any significant variations in four seasons. The P content of S. validus didn''t show any significant seasonal variations, while that of L. salicaria and P. australis decreased significantly in the winter, and that of C.alternifolius and P. australis decreased significantly in the summer. (2) The C/N/P ratio of the four hydrophytes had different seasonal variation characteristics. The C/N ratio of C.alternifolius didn''t show any significant seasonal variations, while that of the other three hydrophytes increased significantly in the spring. The C/P ratio of P. australis and L. salicaria decreased significantly in the spring, and that of C.alternifolius and P. australis increased significantly in the summer, while S. validus didn''t show such significant seasonal variations. To the N/P ratio, C.alternifolius appeared to have no significant seasonal variations, while the other three increased significantly in the winter when their biomass was lower and decreased significantly in the spring and then increased significantly in the summer as their biomass increasing. (3) The effects of the season on C, P content and N/P ratio of the four hydrophytes were much greater than those of the species. To the N content, C/N and C/P ratio, the effects of the species were slightly greater than those of the season. (4) The C/N and C/P ratio of the four hydrophytes shew the significant negative correlations with the N and P content respectively, which indicated that C/N and C/P ratio of the hydrophyte were determined by the N and P content respectively. There were no significant correlations between C and N content, and also C and P content of the hydrophytes in the autumn and summer, which indicated that the activity of C was independent of N and P in the summer and autumn. The N and P contents were significantly correlated only in the spring and summer. From above all, we got the conclusion that the different hydrophytes had the different seasonal variation characteristics in the C, N, P contents and corresponding stoichiometric ratios. Future studies need to synthesize the habitat factors to reveal the mechanisms laying behind this.