Data from: Competition is a strong driving factor in wetlands, peaking during drying out periods

The aim of the study is to investigate the relative importance of plant-plant interactions with regard to flooding and drought effect on perennial plant performances in wetlands. Flooding is expected to be the major driver and, accordingly, the importance of drought is hardly if ever taken into account. Focusing on five widespread species, the growth, the survival and the competitive ability of plants were monitored on permanent plots spread along two elevation gradients. Flooding duration and drought intensity were found to vary substantially along the ~ 0.5 meter range elevation gradient. Flooding and drought alternate over the hydrological year and the pin-point surveys were thus conducted over the course of one year. The data were modeled taking into account survival, recruitment and competitive growth throughout flooding and drying out periods. Flooding and drought both directly impacted the plant performances and their competitive effect, with the effect of drought being much more general among species and of higher magnitude than flooding. The importance of competition was found to be high for all species, particularly during the drying out period. It varied more along the flooding gradient than along the drought gradient. The higher flooding tolerance shown by the studied species compared to drought may be related to species specific growth timing together with efficient response traits. These results offer new insights into the filters operating over the species pools. This suggests that the drying out period and drought conditions may be even more important for species’ relative success and the importance of competition than the flooding pattern. The general applicability of this result, obtained in mild Atlantic climate and fertile wetlands, remains to be studied.

本研究旨在探究植物间相互作用在湿地多年生植物表现受淹水与干旱影响时的相对重要性。以往研究通常将淹水视为主要驱动因子，因此几乎从未考量干旱的重要性。本研究聚焦5个广布物种，在沿两条海拔梯度布设的永久样地中监测植物的生长、存活与竞争能力。研究发现，在约0.5米的海拔梯度范围内，淹水时长与干旱强度存在显著差异。淹水与干旱在水文年内交替出现，因此本研究在为期一年的周期内开展了针测法调查。研究在建模过程中纳入了淹水与干涸期内的植物存活、种群补充与竞争生长过程。结果表明，淹水与干旱均直接影响植物表现及其竞争效应，且干旱对不同物种的影响更为普遍，强度也高于淹水。竞争对所有物种均具有显著重要性，尤其在干涸期更为突出；其重要性沿淹水梯度的变化幅度大于干旱梯度。相较于干旱，供试物种表现出更强的淹水耐受性，这可能与物种特有的生长时序以及高效的响应性状相关。本研究结果为解析物种库所经历的筛选机制提供了全新视角。研究结果显示，相较于淹水模式，干涸期与干旱条件对物种的相对存续表现及竞争的重要性可能更为关键。本研究在温和大西洋气候与肥沃湿地中得到的上述结果，其普遍适用性仍有待进一步探究。