Table_2_A crop for a forest: Opuntia ficus-indica as a tool for the restoration of Mediterranean forests in areas at desertification risk.docx

IntroductionThe Mediterranean is the European region with the lowest woody cover and the highest level of habitat degradation, being highly susceptible to climate change effects and desertification risk. In such worrying conditions, increasing woody cover and restoring forests is a major goal established in several international commitments. However, recruitment limitation of woody species is rather frequent both within natural regeneration processes and active restoration programs, particularly due to drought, overgrazing, and a lack of post-planting tending operations. Therefore, finding suitable tools to improve the recruitment success of native woody species is of crucial importance.
MethodsWe assessed woody natural regeneration under abandoned prickly pear orchards, olive trees, and nearby open areas in three sites under high desertification risk in central Sicily (Italy). Then, we tested for differences in density, richness, diversity, height, and basal diameter of the woody recruiting species between these three habitats.
Results and discussionNatural regeneration was widespread under prickly pear, with 94.6% of the sampled plots showing at least one recruit, in comparison to 61.6% of plots under olive and 22.3% in open areas. Natural regeneration density under prickly pears (114 ± 99 individuals m−2) was significantly higher (p < 0.001) than under olive trees (60.4 ± 76.4) and open areas (4.6 ± 9.3). Recruits’ diversity, basal diameter, and height were also significantly higher under prickly pear, concentrating 94.4% of the individuals higher than 100 cm and all late successional species. Our results indicate a great potential for prickly pears to accelerate the natural regeneration of Mediterranean woody species in areas under desertification. However, a site-specific evaluation must be made taking into account prickly pear’s historical presence, temporary income as a crop, management capacity and, especially, its invasive potential.

引言
地中海区域是欧洲木本植被覆盖率最低、生境退化程度最高的区域，极易受到气候变化影响且面临荒漠化风险。在此严峻形势下，提升木本植被覆盖率与森林恢复已成为多项国际共识中的核心目标。然而，无论是自然更新过程还是人工恢复项目中，木本物种的补充限制都相当普遍，这主要由干旱、过度放牧以及缺乏种植后抚育操作所致。因此，寻找适宜的手段以提升本土木本物种的更新成活率，具有至关重要的意义。

研究方法
我们在意大利西西里岛中部3个高荒漠化风险样地中，调查了废弃梨果仙人掌（prickly pear）种植园、油橄榄林及邻近开阔区域内的木本自然更新状况。随后，我们对比了这三类生境中木本更新植株的密度、物种丰富度、多样性、株高及基径的差异。

结果与讨论
梨果仙人掌种植园内自然更新现象普遍，94.6%的样方至少存在1株更新植株，而油橄榄林样方的这一比例为61.6%，开阔区域仅为22.3%。梨果仙人掌种植园内的自然更新密度为（114±99）株·m⁻²，显著高于油橄榄林（60.4±76.4）株·m⁻²与开阔区域（4.6±9.3）株·m⁻²（p<0.001）。更新植株的多样性、基径与株高同样在梨果仙人掌种植园内显著更高，该生境集中了94.4%的株高超过100cm的个体，以及所有晚演替物种。本研究结果表明，梨果仙人掌在荒漠化区域中，具备加速地中海区域木本物种自然更新的巨大潜力。但需针对具体样地开展评估，综合考量梨果仙人掌的历史分布、作为经济作物的短期收益、管护能力，尤其需关注其入侵风险。