Univ. Bordeaux, CNRS, Bordeaux INP, EPOC, UMR 5805, F-33600 Pessac, France.
Univ. Bordeaux, CNRS, Bordeaux INP, EPOC, UMR 5805, F-33600 Pessac, France.
Sci Total Environ. 2023 Dec 15;904:166905. doi: 10.1016/j.scitotenv.2023.166905. Epub 2023 Sep 10.
Multiple effects, operating either on the long-term (soil-engineering effects) or on the short-term during plant life (microclimate modification or resources pre-emption), can act simultaneously and determine the outcome of plant-plant interactions. These diverse effects have not been disentangled along a gradient of metal/metalloid pollution, although this is crucial for understanding the dominant species turnover along the gradient, and thus the driving processes of facilitation recurrently found in metalliferous ecosystems, which could help improving ecological restoration of these degraded ecosystems. Here, we experimentally assessed different short-term effects of two dominant forbs of highly polluted habitats (Hutchinsia alpina and Arenaria multicaulis, tolerant to metal stress) and two grasses of less polluted habitats (Agrostis capillaris and Festuca rubra, less tolerant to metal stress) on target plant species (the same as the dominant species mentioned above) transplanted along a large metal pollution gradient. Additionally, in highly polluted environments, we differentiated short- from long-term effects of the two metallicolous forbs, which had different abilities to concentrate metals in their leaves. In line with other studies along metal gradients, variation of short-term interactions appeared to follow the Stress Gradient Hypothesis for plants less adapted to metal pollution (p = 0.030), with positive interactions dominating in most severe areas. Regarding long-term effects, the species with highest leaf metal-accumulation showed no negative effect contrary to the Elemental allelopathy Hypothesis. Long-term effects of the species with lower leaf-metal accumulation could not be determined because of the occurrence of an unexpected difference in micro-habitat conditions (soil depth and humidity) for this species along the metal pollution gradient. Increasing short-term facilitation along metal pollution gradients, which confirmed previous studies, is promising for improving conditions and restoring the most polluted environments. However, long-term results stressed the difficulty to quantify these effects given that these areas are highly fragmented and heterogeneous.
多种效应，无论是长期（土壤工程效应）还是植物生命期内的短期（微气候改变或资源抢占），都可以同时发生并决定植物-植物相互作用的结果。尽管沿着金属/类金属污染梯度来区分这些不同的效应对于理解主导物种沿梯度的转换至关重要，从而理解在富含金属的生态系统中反复出现的促进作用的驱动过程，这可能有助于改善这些退化生态系统的生态恢复，但这些效应尚未在重金属/类金属污染梯度上被区分开来。在这里，我们通过实验评估了两种高度污染生境中的优势草本植物（对金属胁迫具有耐受性的 Hutchinsia alpina 和 Arenaria multicaulis）和两种污染程度较低生境中的草本植物（对金属胁迫的耐受性较低的 Agrostis capillaris 和 Festuca rubra）对目标植物物种（与上述优势物种相同）的不同短期效应，这些目标植物物种沿一个大的金属污染梯度进行了移栽。此外，在高度污染的环境中，我们区分了两种富金属草本植物的短期和长期效应，这两种植物具有不同的在叶片中积累金属的能力。与沿着金属梯度的其他研究一致，短期相互作用的变化似乎遵循了对金属污染适应能力较低的植物的“胁迫梯度假说”（p=0.030），在最严重的地区，正相互作用占主导地位。关于长期效应，具有最高叶片金属积累的物种没有表现出负效应，这与“元素化感假说”相反。对于叶片金属积累较低的物种的长期效应，由于该物种在金属污染梯度上的微生境条件（土壤深度和湿度）出现了意外差异，因此无法确定。沿着金属污染梯度增加短期促进作用，这与以前的研究一致，有望改善条件并恢复最污染的环境。然而，长期结果强调了量化这些效应的难度，因为这些地区高度破碎化和异质化。
