基于胁迫梯度假说和互惠理论的海三棱藨草种群恢复技术

滨海湿地生态修复已成为阻止海岸带生态系统退化、保护生物多样性以及提供生态服务的关键措施。以长江口原生盐沼植物海三棱藨草(Scirpus mariqueter)为研究对象,选取崇明东滩新生滩涂湿地为研究区域,通过沿潮滩高程梯度的海三棱藨草植株斑块的移植实验,探究胁迫梯度假说和互惠理论(即种内的正相互作用)对长江口海三棱藨草种群恢复的指导意义。研究结果显示:(1)在一定的胁迫梯度范围内(潮滩高程2.0 m以上),增大种植斑块可以促进海三棱藨草的种内正相互作用,显著提高种植斑块的存活率和植株密度(P0.05);(2)潮滩水文动力沉积条件与潮滩高程梯度密切相关(P0.05),水文动力沉积作用对海三棱藨草定居和生长的胁迫随高程梯度下降而增强。潮滩高程2.0 m以下处强烈的水文动力条件干扰限制了生物-物理因素的正反馈作用。滨海湿地盐沼植被修复工作的成功率可以通过改进种植方式,增强种内的正相互作用得到极大的提高。研究可为开展大规模滨海湿地盐沼植被修复工程和提高生态修复效率提供科学依据和技术支持。

The stress-gradient hypothesis and facilitation theory-based restoration technique for Scirpus mariqueter population

Ecological restoration is an important strategy to recover the degradation of coastal wetlands, to protect the biodiversity, and to enhance its ecological services. Over the past twenty years, the exotic species Spartina alterniflora has rapidly invaded the salt marshes in the Yangtze Estuary, which was formerly covered by the native species Scirpus mariqueter. A large-scale restoration project was launched to annihilate the invasive species and restore the native salt marsh vegetation in the nature reserve of Chongming Dongtan. In this study, we carried out a transplantation experiment with different sizes of the S. mariqueter patches along a tidal elevation gradient. We aimed to test the value of facilitation theory (positive intraspecific interactions to facilitate organism survival success) and stress-gradient hypothesis on salt marsh restoration for the newly formed tidal flats in Chongming Dongtan. The results showed that under a certain range of intertidal stress-gradient (above flat elevation 2.0 m), increasing size of the transplanted patches significantly enhances the survival rate and shoot density of S. mariqueter (P < 0.05). The hydrodynamic conditions on the intertidal flats were closely related to the elevation of tidal flat (P < 0.05), where the stronger hydrodynamic stress at the flat elevation below 2.0 m minimizes the positive bio-physical interactions. Our results indicated that improvement in the transplantation design of the target species might motivate the positive intraspecific interactions in coastal salt marsh restoration, resulting in a significantly higher restoration success. This study highlighted the value of the facilitation theory in coastal salt marsh restoration, provided the scientific basis and technical support to the large-scale restoration projects, and enhanced the restoration efficiency of the coastal salt marshes in the Yangtze Estuary.