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已有研究表明,土壤氮素增加可提高外来植物的入侵性,降低本地植物的竞争力。为揭示全球氮沉降对入侵种与本地种之间竞争关系的影响,我们于2010年5-8月在中国科学院北京森林生态系统定位研究站温室内,采用取代系列实验方法(standard replacement experiment),研究了3个氮素水平下入侵种豚草(Ambrosia artemisiifolia)与本地种黄花蒿(Artemisi a annua)、蒙古蒿(Artemisia mongolica)的生长特征及种内、种间竞争关系的变化。实验采用双因素-随机区组设计,设置了低氮、中氮和高氮3个氮素水平,每一氮素水平分别设置豚草和黄花蒿、豚草和蒙古蒿组成的竞争实验,生长90d后测量株高和生物量。结果表明:单栽情况下,随氮素水平的增加3个物种的株高均增加,而生物量均无显著变化;混栽情况下,3个物种株高和生物量随氮素水平的增加变化各异,豚草呈极显著增加趋势,而黄花蒿无明显变化,蒙古蒿则先增加后减少。豚草的快速生长使其在竞争中处于优势地位,对本地种黄花蒿和蒙古蒿产生明显的竞争效应。但不同氮素水平下,豚草对本地种的竞争力不同:低氮素水平下,豚草<两个本地种;中氮素水平下,黄花蒿<豚草<蒙古蒿;高氮素水平下,豚草>两个本地种。氮素添加显著提高了豚草的种间竞争力,改变了豚草与本地种之间的竞争关系,使竞争有利于入侵种。据此推测,在全球变化的背景下,氮沉降的增加将会促进外来种豚草的入侵,增加本地群落的可入侵性。
Studies have shown that increased soil nitrogen can increase the invasiveness of exotic plants and reduce the competitiveness of native plants. To reveal the impact of global nitrogen deposition on the competition between invasive species and native species, we used a standard replacement experiment in the greenhouse of the Beijing Forest Ecosystem Research Station at Chinese Academy of Sciences from May to August 2010, The growth characteristics of Artrosis artemisiifolia and native Artemisia a annua and Artemisia mongolica were studied under three levels of nitrogen stress. The relationships among species and interspecific competition were studied. A two-factor-randomized block design was adopted in the experiment. Three nitrogen levels of low nitrogen, medium nitrogen and high nitrogen were set. The competition experiments of ragweed and Artemisia annua, ragweed and Mongolia artemisia were set up for each nitrogen level. After 90 days, plant height and biomass were measured. The results showed that the plant height of three species increased with the increase of nitrogen level, but the biomass did not change significantly under single planting. The plant height and biomass of three species increased with the increase of nitrogen level Varies, ragweed showed a significant increase in trend, while no significant change in Artemisia annua, Artemisia annua first increased and then decreased. The rapid growth of ragweed has placed it in a dominant position in competition with a clear competitive effect on native Artemisia annua and Artemisia annua. However, under different levels of nitrogen, the competitiveness of native ragweed varied with different ragweeds. Under the low nitrogen level, ragweed two native species. Nitrogen addition significantly increased the interspecific competitiveness of ragweed and changed the competition between ragweed and native species, making competition favorable for invasive species. It is speculated that in the context of global change, increased nitrogen deposition will promote the invasion of exotic species of ragweed and increase the invasiveness of local communities.