Stinca Adriano, Chirico Giovanni Battista, Incerti Guido, Bonanomi Giuliano
Department of Agriculture, University of Naples Federico II, via Università 100, Portici (Naples), Italy.
PLoS One. 2015 Apr 2;10(4):e0123128. doi: 10.1371/journal.pone.0123128. eCollection 2015.
Ecosystem invasion by non-native, nitrogen-fixing species is a global phenomenon with serious ecological consequences. However, in the Mediterranean basin few studies addressed the impact of invasion by nitrogen-fixing shrubs on soil quality and hydrological properties at local scale, and the possible effects on succession dynamics and ecosystem invasibility by further species. In this multidisciplinary study we investigated the impact of Genista aetnensis (Biv.) DC., an exotic nitrogen-fixing shrub, on the Vesuvius Grand Cone (Southern Italy). Specifically, we tested the hypotheses that the invasion of G. aetnensis has a significant impact on soil quality, soil hydrological regime, local microclimate and plant community structure, and that its impact increases during the plant ontogenetic cycle. We showed that G. aetnensis, in a relatively short time-span (i.e. ~ 40 years), has been able to build-up an island of fertility under its canopy, by accumulating considerable stocks of C, N, and P in the soil, and by also improving the soil hydrological properties. Moreover, G. aetnensis mitigates the daily range of soil temperature, reducing the exposure of coexisting plants to extremely high temperatures and water loss by soil evaporation, particularly during the growing season. Such amelioration of soil quality, coupled with the mitigation of below-canopy microclimatic conditions, has enhanced plant colonization of the barren Grand Cone slopes, by both herbaceous and woody species. These results suggest that the invasion of G. aetnensis could eventually drive to the spread of other, more resource-demanding exotic species, promoting alternative successional trajectories that may dramatically affect the local landscape. Our study is the first record of the invasion of G. aetnensis, an additional example of the regime shifts driven by N-fixing shrubs in Mediterranean region. Further studies are needed to identity specific management practices that can limit the spread and impacts of this species.
非本地固氮物种对生态系统的入侵是一种具有严重生态后果的全球现象。然而，在地中海盆地，很少有研究探讨固氮灌木入侵对局部尺度土壤质量和水文特性的影响，以及对演替动态和其他物种生态系统可入侵性的可能影响。在这项多学科研究中，我们调查了外来固氮灌木艾氏鹰爪豆（Genista aetnensis (Biv.) DC.）对维苏威大火山锥（意大利南部）的影响。具体而言，我们检验了以下假设：艾氏鹰爪豆的入侵对土壤质量、土壤水文状况、局部小气候和植物群落结构有重大影响，并且其影响在植物个体发育周期中会增强。我们发现，艾氏鹰爪豆在相对较短的时间跨度（即约40年）内，通过在土壤中积累大量的碳、氮和磷，并改善土壤水文特性，能够在其树冠下形成一个肥沃的岛屿。此外，艾氏鹰爪豆减轻了土壤温度的日变化范围，减少了共存植物暴露于极高温度下的时间以及土壤蒸发导致的水分流失，特别是在生长季节。土壤质量的这种改善，再加上树冠下微气候条件的缓解，促进了草本和木本物种在贫瘠的大火山锥斜坡上的植物定居。这些结果表明，艾氏鹰爪豆的入侵最终可能导致其他对资源需求更高的外来物种的扩散，促进替代的演替轨迹，这可能会对当地景观产生巨大影响。我们的研究是艾氏鹰爪豆入侵的首次记录，是地中海地区固氮灌木驱动的生态系统转变的又一个例子。需要进一步的研究来确定能够限制该物种扩散和影响的具体管理措施。
