Salt pan landscape and halophyte re-establishment

International research on disturbed landscapes has shown that active erosion of soil-free bare ground can maintain distinctive local geological features and biodiversity by preventing incursion of a robust vegetation cover. In this study, we have tested this approach by removing exotic vegetation and associated proto-soil that had encroached over evaporative salt pans in inland southern South Island. The ten study sites were all on clay-altered Otago Schist basement and talus. All the sites rapidly (months) re-developed high salinity (EC >1 mS/cm) and alkaline pH 8-10. Sloping sites (10-30°) rapidly developed surficial erosion regimes that involved scouring and runnel formation (cm scale), with regular sediment reworking downslope on the cm-dm scale during rain events. The combination of active surface remobilisation, high salinity and alkaline pH was effective at limiting recolonisation of exotic vegetation. In contrast, rare New Zealand endemic salt-tolerant plants (halophytes) colonised parts of the dynamic bare surfaces from relict nearby patches, initially within months, and some sites had almost complete halophyte cover after four years. The results show that with suitable intervention it is possible to prevent disappearance of these unique geological, geochemical, and biodiverse landscape features.

针对受干扰景观的国际研究表明，通过抑制茂密植被的入侵，无土裸地的活跃侵蚀作用可维持独特的本地地质特征与生物多样性。本研究通过清除入侵内陆南岛南部蒸发盐盘的外来植被及其伴随的雏形土壤（proto-soil），对该思路开展了验证。本次研究的10个样地均位于经黏土蚀变的奥塔哥片岩（Otago Schist）基底与倒石堆（talus）之上。所有样地均在数月内快速重建出高盐度环境（电导率EC>1 mS/cm）与8~10的碱性pH值。坡度介于10°~30°的样地快速形成了以冲刷与厘米级尺度细沟形成为特征的地表侵蚀模式，降雨事件期间沉积物会以厘米至分米级的尺度沿坡向下被频繁扰动。活跃的地表物质再移动、高盐度与碱性pH三者共同作用，可有效抑制外来植被的再次定植。与之相反，新西兰特有珍稀耐盐植物（halophytes）会从附近的残存斑块定植到部分动态裸地表面，初期仅需数月时间；部分样地在四年后几乎完全被盐生植物覆盖。研究结果表明，通过合理的人工干预，可有效保护这些独特的地质、地球化学与生物多样性景观特征免于消失。