Yelenik Stephanie, Rose Eli, Cordell Susan, Victoria Michelle, Kellner James R
U.S. Geological Survey, Pacific Island Ecosystem Research Station, Hawai'i National Park, Hawai'i, USA.
Institute of Pacific Islands Forestry, USDA Forest Service, Hilo, Hawai'i, USA.
Ecol Appl. 2022 Dec;32(8):e2690. doi: 10.1002/eap.2690. Epub 2022 Aug 4.
Habitat-suitability indices (HSI) have been employed in restoration to identify optimal sites for planting native species. Often, HSI are based on abiotic variables and do not include biotic interactions, even though similar abiotic conditions can favor both native and nonnative species. Biotic interactions such as competition may be especially important in invader-dominated habitats because invasive species often have fast growth rates and can exploit resources quickly. In this study, we test the utility of an HSI of microtopography derived from airborne LiDAR to predict post-disturbance recovery and native planting success in native shrub-dominated and nonnative, invasive grass-dominated dryland habitats in Hawai'i. The HSI uses high-resolution digital terrain models to classify sites' microtopography as high, medium, or low suitability, based on wind exposure and topographic position. We used a split-plot before-after-control-impact design to implement a disturbance experiment within native shrub (Dodonaea viscosa) and nonnative, invasive grass (Cenchrus clandestinus)-dominated ecosystems across three microtopography categories. In contrast to previous studies using the same HSI, we found that microtopography was a poor predictor of pre-disturbance conditions for soil nutrients, organic matter content, or foliar C:N, within both Dodonaea and Cenchrus vegetation types. In invader-dominated Cenchrus plots, microtopography helped predict cover, but not as expected (i.e., highest cover would be in high-suitability plots): D. viscosa had the greatest cover in low-suitability and C. clandestinus had the greatest cover in medium-suitability plots. Similarly, in native-dominated Dodonaea plots, microtopography was a poor predictor of D. viscosa, C. clandestinus, and total plant cover. Although we found some evidence that microtopography helped inform post-disturbance plant recovery of D. viscosa and total plant cover, vegetation type was a more important predictor. Important for considering the success of plantings, percent cover of D. viscosa decreased while percent cover of C. clandestinus increased within both vegetation types 20 months after disturbance. Our results are evidence that HSIs based on topographic features may prove most useful for choosing planting sites in harsh habitats or those already dominated by native species. In more productive habitats, competition from resident species may offset any benefits gained from "better" suitability sites.
栖息地适宜性指数（HSI）已被用于生态恢复，以确定种植本地物种的最佳地点。通常，HSI基于非生物变量，不包括生物相互作用，尽管相似的非生物条件可能对本地和非本地物种都有利。在入侵物种占主导的栖息地中，竞争等生物相互作用可能尤为重要，因为入侵物种通常生长速度快，能迅速利用资源。在本研究中，我们测试了一种基于机载激光雷达的微地形HSI在预测夏威夷本地灌木主导和非本地入侵草主导的旱地栖息地干扰后恢复及本地植物种植成功率方面的效用。该HSI利用高分辨率数字地形模型，根据风暴露和地形位置将地点的微地形分类为高、中、低适宜性。我们采用了一种前后对照影响的裂区设计，在三种微地形类别下的本地灌木（粘毛山龙眼）和非本地入侵草（隐花草）主导的生态系统中进行干扰实验。与之前使用相同HSI的研究不同，我们发现，在粘毛山龙眼和隐花草植被类型中，微地形对干扰前土壤养分、有机质含量或叶片碳氮比的预测效果较差。在入侵物种主导的隐花草地块中，微地形有助于预测植被覆盖，但并非如预期那样（即高适宜性地块的植被覆盖最高）：粘毛山龙眼在低适宜性地块中覆盖度最大，隐花草在中等适宜性地块中覆盖度最大。同样，在本地物种主导的粘毛山龙地块中，微地形对粘毛山龙眼、隐花草和总植物覆盖度的预测效果也较差。尽管我们发现一些证据表明微地形有助于了解干扰后粘毛山龙眼的植物恢复和总植物覆盖度，但植被类型是更重要的预测因素。对于考虑种植成功率很重要的一点是，干扰20个月后，两种植被类型中粘毛山龙眼的覆盖度百分比下降，而隐花草的覆盖度百分比增加。我们的结果表明，基于地形特征的HSI可能在选择恶劣栖息地或已由本地物种主导的栖息地的种植地点时最为有用。在生产力更高的栖息地中，本地物种的竞争可能会抵消从“更好”适宜性地点获得的任何益处。
