The effect of soil and climate on the growth and survival of A. saligna and A. cyclops seedlings on a mountain gradient in Villiersdorp, South Africa.

Very few studies have simultaneously considered the effect of climate change and invasive species on ecosystems, and there is a great need for research in this field. Considered in isolation, climate change, invasive species and habitat destruction are the greatest threats to ecosystem functioning. It is believed that by causing disturbances in ecosystems (i.e. creating niches and lowering community resistance), climate change may increase the invasive ability of alien species. To determine the possible success of invasive alien species, we need to determine which factors (i.e. soil; climate; dispersal ability) could work together to facilitate or hinder their spread in a changing climate. Using two invasive alien species, Acacia cyclops and Acacia saligna, this study attempts to determine which factors (i.e. soil and climate) affect their survival and growth. This was done by means of reciprocal transplants using an environmental gradient as a proxy for different climatic conditions. A. saligna showed no significant response to soil type, whilst A. cyclops showed increased survival and growth on fynbos soil. Survival of A. saligna was affected by its position on the gradient, i.e. climate, but its growth once established was not affected. A. cyclops showed significant differences in both survival and growth due to climate. It is suggested that A. saligna is more likely to invade mountain Fynbos under future climate change scenarios: soil type will not be a barrier to its spread, and decreased rainfall may cause lowland conditions to become too dry. A. cyclops is more drought tolerant and will most likely be able to maintain its range in the lowlands. Since many other factors not included in this study are likely to be synergistic with climate change, further studies of this nature are encouraged.

为数不多的研究同时考虑了气候变化和入侵物种对生态系统的影响，该领域的研究需求极为迫切。将气候变化、入侵物种以及栖息地破坏单独考虑，它们已成为生态系统功能运作的最大威胁。据信，气候变化通过在生态系统中引起扰动（即创造生态位并降低群落抵抗力），可能会增强外来物种的入侵能力。为了确定入侵外来物种可能的成功率，我们需要确定哪些因素（例如土壤、气候；扩散能力）能够协同作用，促进或阻碍它们在变化气候中的传播。本研究以两种入侵外来物种——刺槐（Acacia cyclops）和刺槐（Acacia saligna）为对象，试图确定哪些因素（例如土壤和气候）影响它们的生存和生长。通过使用环境梯度作为不同气候条件的替代品，采用相互移植的方法进行研究。A. saligna对土壤类型没有显示出显著的响应，而A. cyclops在芬布士土壤上显示出更高的生存和生长。A. saligna的生存受到其在梯度上的位置，即气候的影响，但其一旦建立后，生长则不受影响。A. cyclops在生存和生长方面都显示出由于气候引起的显著差异。有观点认为，在未来的气候变化情景下，A. saligna更有可能入侵山地芬布士：土壤类型不会成为其传播的障碍，而减少的降雨量可能导致低地条件变得过于干燥。A. cyclops更耐旱，很可能能够在低地维持其分布范围。鉴于许多未包括在本研究中的其他因素可能与气候变化产生协同效应，因此鼓励进行更多此类研究。