Prolonged flow intermittency undermines the habitat potential of forested landscapes for a stream-dwelling dragonfly

Understanding how land use and variability of the hydrological regime
jointly shape species distributions is essential for the conservation of
aquatic insects in increasingly intermittent streams. We investigated how
flow intermittency influences the relationship between land use and the
occurrence probability of Cordulegaster heros in a drying river
network. Field surveys were conducted at 42 stream sites in southwestern
Hungary over a two-year period. We combined species presence–absence data
with land use variables and hydrological proxies. Statistical analyses
included decision tree modeling and binomial generalized linear
models. C. heros was associated with forested landscapes and
absent from sites with prolonged zero-flow periods or high agricultural
land use. Occurrence probability declined markedly when forest cover was
low or when dry periods were extended in duration. Although C.
heros larvae can tolerate short-term drying by burrowing into sediments,
prolonged flow intermittency and reduced landscape connectivity may limit
both survival and recolonization. Our findings underscore the need for
conservation strategies that jointly address land use and hydrological
conditions to counter the rising flow intermittency expected with ongoing
climate change.

明晰土地利用方式与水文情势（hydrological regime）变异如何共同塑造物种分布格局，对于日益断流化溪流中的水生昆虫保护至关重要。本研究以渐趋干涸的河网为研究对象，探究了水流间歇性如何影响土地利用与赫氏弓蜓（Cordulegaster heros）出现概率之间的关联。研究团队于匈牙利西南部的42处溪流样点开展了为期两年的野外调查，将物种出现-缺失数据与土地利用变量、水文替代指标相结合。统计分析方法涵盖决策树建模与二项式广义线性模型。结果显示，赫氏弓蜓与森林覆盖的景观呈显著正相关，且不会出现在长期零流量时段或农业用地占比过高的样点中；当森林覆盖率较低或枯水期持续时长增加时，其出现概率会显著下降。尽管赫氏弓蜓的幼虫可通过潜入沉积物来耐受短期枯水，但长期水流间歇性与景观连通性的降低，可能会同时限制其生存与重新定殖能力。本研究结果表明，需制定兼顾土地利用与水文条件的保护策略，以应对气候变化下日益加剧的水流间歇性问题。