Hischier Chantal M, Hille Ris Lambers Janneke, Iseli Evelin, Alexander Jake M
Institute of Integrative Biology, ETH Zürich, 8092 Zürich, Switzerland.
Alp Bot. 2024;134(1):15-27. doi: 10.1007/s00035-023-00302-8. Epub 2023 Nov 24.
Deciphering how plants interact with each other across environmental gradients is important to understand plant community assembly, as well as potential future plant responses to environmental change. Plantplant interactions are expected to shift from predominantly negative (i.e. competition) to predominantly positive (i.e. facilitation) along gradients of environmental severity. However, most experiments examine the net effects of interactions by growing plants in either the presence or absence of neighbours, thereby neglecting the interplay of both negative and positive effects acting simultaneously within communities. To partially unravel these effects, we tested how the seedling establishment of 10 mountain grassland plants varied in the presence versus absence of plant communities at two sites along an elevation gradient. We created a third experimental treatment (using plastic plant mats to mimic surrounding vegetation) that retained the main hypothesised benefits of plant neighbours (microsite amelioration), while reducing a key negative effect (competition for soil resources). In contrast to our expectations, we found evidence for net positive effects of vegetation at the low elevation site, and net negative effects at the high elevation site. Interestingly, the negative effects of plant neighbours at high elevation were driven by high establishment rates of low elevation grasses in bare soil plots. At both sites, establishment rates were highest in artificial vegetation (after excluding two low elevation grasses at the high elevation site), indicating that positive effects of above-ground vegetation are partially offset by their negative effects. Our results demonstrate that both competition and facilitation act jointly to affect community structure across environmental gradients, while emphasising that competition can be strong also at higher elevations in temperate mountain regions. Consequently, plantplant interactions are likely to influence the establishment of new, and persistence of resident, species in mountain plant communities as environments change.
The online version contains supplementary material available at 10.1007/s00035-023-00302-8.
解读植物如何在环境梯度上相互作用对于理解植物群落组装以及未来植物对环境变化的潜在反应至关重要。沿着环境严峻程度的梯度，植物间相互作用预计会从主要为负（即竞争）转变为主要为正（即促进）。然而，大多数实验通过在有或没有邻居植物的情况下种植植物来检验相互作用的净效应，从而忽略了群落中同时起作用的正负效应的相互作用。为了部分揭示这些效应，我们测试了沿着海拔梯度的两个地点，10种山地草原植物的幼苗建立在有植物群落和没有植物群落的情况下如何变化。我们创建了第三种实验处理（使用塑料植物垫来模拟周围植被），该处理保留了植物邻居的主要假设益处（微生境改善），同时减少了一个关键的负面影响（对土壤资源的竞争）。与我们的预期相反，我们发现在低海拔地点植被有净正效应的证据，而在高海拔地点有净负效应。有趣的是，高海拔地区植物邻居的负面影响是由裸土地块中低海拔草的高建立率驱动的。在两个地点，人工植被中的建立率最高（在排除高海拔地点的两种低海拔草之后），这表明地上植被的正效应部分被其负效应抵消。我们的结果表明，竞争和促进共同作用以影响跨环境梯度的群落结构，同时强调在温带山区较高海拔处竞争也可能很强。因此，随着环境变化，植物间相互作用可能会影响山地植物群落中新物种的建立和现有物种的持续存在。
在线版本包含可在10.1007/s00035-023-00302-8获取的补充材料。
