Keppel Gunnar, Robinson Todd P, Wardell-Johnson Grant W, Yates Colin J, Van Niel Kimberly P, Byrne Margaret, Schut Antonius G T
School of Natural and Built Environments, University of South Australia, GPO Box 2471, Adelaide, SA 5001, Australia
Spatial Sciences, Curtin University, Kent St., Bentley, Western Australia.
Ann Bot. 2017 Jan;119(2):289-300. doi: 10.1093/aob/mcw182. Epub 2016 Sep 15.
Low-altitude mountains constitute important centres of diversity in landscapes with little topographic variation, such as the Southwest Australian Floristic Region (SWAFR). They also provide unique climatic and edaphic conditions that may allow them to function as refugia. We investigate whether the Porongurups (altitude 655 m) in the SWAFR will provide a refugium for the endemic Ornduffia calthifolia and O. marchantii under forecast climate change.
We used species distribution modelling based on WorldClim climatic data, 30-m elevation data and a 2-m-resolution LiDAR-derived digital elevation model (DEM) to predict current and future distributions of the Ornduffia species at local and regional scales based on 605 field-based abundance estimates. Future distributions were forecast using RCP2.6 and RCP4.5 projections. To determine whether local edaphic and biotic factors impact these forecasts, we tested whether soil depth and vegetation height were significant predictors of abundance using generalized additive models (GAMs).
Species distribution modelling revealed the importance of elevation and topographic variables at the local scale for determining distributions of both species, which also preferred shadier locations and higher slopes. However, O. calthifolia occurred at higher (cooler) elevations with rugged, concave topography, while O. marchantii occurred in disturbed sites at lower locations with less rugged, convex topography. Under future climates both species are likely to severely contract under the milder RCP2.6 projection (approx. 2 °C of global warming), but are unlikely to persist if warming is more severe (RCP4.5). GAMs showed that soil depth and vegetation height are important predictors of O. calthifolia and O. marchantii distributions, respectively.
The Porongurups constitute an important refugium for O. calthifolia and O. marchantii, but limits to this capacity may be reached if global warming exceeds 2 °C. This capacity is moderated at local scales by biotic and edaphic factors.
在地形变化较小的景观中，如澳大利亚西南部植物区（SWAFR），低海拔山脉是重要的生物多样性中心。它们还提供了独特的气候和土壤条件，使其有可能作为避难所。我们研究了在预测的气候变化下，SWAFR的波龙古拉普斯山脉（海拔655米）是否会为特有物种卡氏欧氏苔草（Ornduffia calthifolia）和马尔尚氏欧氏苔草（O. marchantii）提供避难所。
我们基于WorldClim气候数据、30米高程数据和2米分辨率的激光雷达衍生数字高程模型（DEM），利用物种分布模型，根据605个实地丰度估计值，在局部和区域尺度上预测欧氏苔草属物种的当前和未来分布。使用代表性浓度路径（RCP）2.6和RCP4.5预测来预测未来分布。为了确定局部土壤和生物因素是否影响这些预测，我们使用广义相加模型（GAMs）测试土壤深度和植被高度是否是丰度的显著预测因子。
物种分布模型显示，在局部尺度上，海拔和地形变量对于确定两种物种的分布很重要，这两种物种也更喜欢较阴凉的地方和较高的坡度。然而，卡氏欧氏苔草出现在海拔较高（较凉爽）、地形崎岖且呈凹形的地方，而马尔尚氏欧氏苔草出现在海拔较低、受干扰、地形不太崎岖且呈凸形的地方。在未来气候条件下，在较为温和的RCP2.6预测（全球变暖约2°C）下，两种物种的分布范围都可能严重缩小，但如果变暖更严重（RCP4.5），它们不太可能持续存在。广义相加模型表明，土壤深度和植被高度分别是卡氏欧氏苔草和马尔尚氏欧氏苔草分布的重要预测因子。
波龙古拉普斯山脉是卡氏欧氏苔草和马尔尚氏欧氏苔草的重要避难所，但如果全球变暖超过2°C，这种避难能力可能会达到极限。这种能力在局部尺度上受到生物和土壤因素的调节。
