杭州湾滨海湿地3种草本植物叶片N、P化学计量学的季节变化

Seasonal variations of leaf nitrogen and phosphorus stoichiometry of three herbaceous species in Hangzhou Bay coastal wetlands, China

动态平衡理论是生态化学计量学的理论基础,各种有机体是否存在一个固定的化学计量比是生态学研究的热点问题。该文研究了杭州湾滨海湿地3种优势物种海三棱藨草(Scirpus mariqueter)、糙叶薹草(Carex scabrifolia)和芦苇(Phragmites australis)叶片N、P生态化学计量特征的季节变化。结果发现,3种植物叶片N含量范围分别是7.41–17.12、7.47–13.15和6.03–18.09mg·g–1,平均值(±标准差)分别为(11.69±2.66)、(10.17±1.53)和(11.56±3.19)mg·g–1;叶片P范围分别是0.34–2.60、0.41–1.10和0.35–2.04mg·g–1,平均值为(0.93±0.62)、(0.74±0.23)和(0.82±0.53)mg·g–1;N:P范围分别是7.19–30.63、11.58–16.81和8.62–21.86,平均值为16.83±8.31、14.53±3.91和16.49±5.51,可见不同植物其生态化学计量值范围存在一定差异,但经方差分析发现3种草本植物间生长季节内N、P元素含量差异并不显著(p>0.05)。各物种叶片N、P含量均表现出在生长初期显著大于其他生长季节(p<0.05),生长旺季(6、7月)随着叶片生物量的持续增加,N、P含量逐渐降低并达到最小值,随后8–9月叶片不再生长而N、P含量逐渐回升,在10月叶片衰老时N、P含量再次下降;叶片N:P则在生长初期较小,在生长旺季先升高后降低,随后叶片成熟不再生长时又逐渐增加并趋于稳定。

Aims Homeostasis constrains the elemental composition of individual species within narrow bounds no matter the chemical composition of the environment or the resource base. Our objective was to determine the dynamics of leaf stoichiometry during the growth period of plants and the optimum time for stoichiometry study. Methods We monitored leaf N, P stoichiometry of Seirpus mariqueter, Carex scabrifolia and Phragmites australis, the dominant species in Hangzhou Bay coastal wetlands, at different growth stages from May to October 2007. Important findings Leaf N, P stoichiometry of the Scirpus, Carex and Phragmites species showed differences： 7.41-17.12, 7.47-13.15 and 6.03-18.09 mg·g^-1 for N, 0.34-2.60, 0.41-1.10 and 0.35-2.04 mg·g^-1 for P, and 7.19-30.63, 11.58-16.81 and 8.62-21.86 for N：P ratios, respectively. The arithmetic means for the three species were （11.69 ± 2.66）, （10.17 ± 1.53） and （11.56 ± 3.19） mg·g^-1 for N, （0.93 ± 0.62）, （0.74 ± 0.23） and （0.82 ± 0.53） mg·g^-1 for P, and 16.83 ± 8.31, 14.53 ± 3.91 and 16.49 ± 5.51 for N：P, respectively, but there was no significant difference of N, P stoichiometry （p 〉 0.05）. It showed high N, P concentrations at the early stage of growth because of small biomass and then decreased greatly with leaf expansion during the fast growth period, increased as leaf growth became stable and decreased again with leaf senescence. Leaf N：P was low at the early stage of growth and then increased, decreased strongly at the fast growth period, and became stable after leaf maturation.