不同入侵程度两种菊科植物化学计量特征及其影响因素

Stoichiometric characteristics of two Asteraceae invasive plants at different invasive degrees and its influencing factors

关键词:  外来植物, 生态化学计量学, 氮磷分配, 营养策略, 入侵性

Key words:  alien species, ecological stoichiometry, allocation of nitrogen and phosphorus, nutrition strategy, invasiveness

摘要:

资源分配与养分策略是外来植物入侵性的重要体现。为探究入侵植物的资源分配格局、吸收利用策略以及与入侵性的关系,该研究以2种菊科入侵植物假臭草(Praxelis clematidea)和金腰箭(Synedrella nodiflora)为研究对象,测定了不同入侵程度的植物构件生物量以及各器官碳(C)、氮(N)、磷(P)含量,分析了植物各器官N、P分配格局和化学计量特征及其与土壤营养元素的关系。结果表明:(1)随假臭草入侵程度的加重,土壤速效氮(AN)含量显著降低; 随金腰箭入侵程度的加重,土壤N、P、AN含量显著降低; 假臭草入侵生境土壤N含量(0.696～2.701 g·kg^-1)显著大于金腰箭入侵生境(0.189～0.337 g·kg^-1),土壤C、P、AN、速效磷(AP)含量小于金腰箭入侵生境。(2)3种入侵程度的假臭草和金腰箭N分配为叶>茎>根; P较多地分配至茎(假臭草)、茎和叶(金腰箭); 轻度入侵的假臭草(根、茎)和金腰箭(叶)较重度入侵有低的C:P值和N:P值,2种植物入侵初期有较快的相对生长速率; 2种植物N:P值均为叶>根、茎,其根和茎具有较快的生长能力。(3)3种入侵程度的假臭草根、茎N:P值,根、茎C:P值均小于金腰箭,金腰箭叶N:P值、C:P值均显著小于假臭草,即假臭草根、茎具有较快的相对生长速率并增大入侵性,金腰箭则整体具有更快的相对生长速率,其入侵潜力更强。(4)假臭草和金腰箭各器官N、P分配及相对生长速率分别受土壤AN、AP含量和土壤N、P含量的影响,其相对生长速率分别随土壤AN、AP、N、P含量的增加而增大。该研究结果对深入了解外来植物对资源分配和利用策略以及入侵潜力的预测具有指导意义。

Abstract:

Alien invasive plants are commonly stated to pose a threat to populations of native plants, especially of endangered species. Resource allocation and nutrient strategies are important mechanism of invasion for alien plants. In order to investigate the distribution pattern, uptake and utilization strategies of invasive plants and their invasive, the carbon(C), nitrogen(N)and phosphorus(P)and biomass of the modules of invasive plants Praxelis clematidea and Synedrella nodiflora at different invasive degrees from eastern Guangdong were measured, and further the stoichiometric characteristics, allocation of nitrogen and phosphorus and relationship with soil factors were measured. The results were as follows:(1)Available nitrogen(AN)content in soil declined with increasing of invasive degree for Praxelis clematidea, and the N, P, AN contents in soil declined with increasing of the invasive degree for Synedrella nodiflora. The content of N(0.696 - 2.701 g·kg^-1)in soil of invasive habitat for Praxelis clematidea was greater than that for Synedrella nodiflora (0.189-0.337 g·kg^-1), and the mean contents of C, P, available nitrogen(AN), and available phosphorus(AP)for Praxelis clematidea were less than those for Synedrella nodiflora.(2)For two plants with different invasive degrees, the N distribution for leaves was more than that for stems, and than roots. The P for Praxelis clematidea was distributed more to the stems, and for Synedrella nodiflora to the stems and leaves. The roots and stems of Praxelis clematidea, and leaves of Synedrella nodiflora with mild invasion had low C:P and N:P values than severe invasive degree, indicating two plants with mild invasion may have fast relative growth rate, and strong expansion potential. The N:P values in leaves for two plants were greater than those in roots and stems, implicating that roots and stems may have fast relative growth rate to increase the competitiveness of underground and above-ground.(3)The C:P and N:P values in roots and stems of Praxelis clematidea at different invasive degrees were less than those of Synedrella nodiflora, while the C:P and N:P values in leaves of Synedrella nodiflora were less than that of Praxelis clematidea, showing that although the roots and stems of Praxelis clematidea may have faster relative growth rate, Synedrella nodiflora had faster relative growth rate and stronger invasion potential than Praxelis clematidea.(4)The allocation of nitrogen and phosphorus, and relative growth rate of alien plant Praxelis clematidea were mainly affected by AN, AP contents in soil, that relative growth rate of organs increased with increasing of AN, AP contents in soil. The allocation of nitrogen and phosphorus, and relative growth rate of alien plant Synedrella nodiflora were mainly affected by N, P contents in soil, that relative growth rate of organs increased with increasing of N, P contents in soil. In conclusion, the roots and stems of two Asteraceae alien species have fast relative growth rate, and further to increase the competitiveness of underground and above-ground, but their possible effect on N:P stoichiometry requires further study. The results of this study have guiding significance for further understanding of resource allocation and utilization strategies and prediction of invasive potential of alien plants.