Abstract The oomycete plant pathogen, Phytophthora austrocedri, is an aggressive killer of cypress trees causing severe mortality of Chilean cedar (Austrocedrus chilensis) in Argentina since the 1940 s and now of common juniper (Juniperus communis s.l.) in the UK. Rapid mortality of key UK juniper populations was first observed in the early 2000 s. The causal agent of mortality was confirmed as P. austrocedri in 2012 and the pathogen has now been widely detected - but is not ubiquitous - in juniper populations across Scotland and England. Although juniper has a broad distribution across the northern hemisphere, the UK incidence of P. austrocedri remains the only confirmed infection of juniper populations globally. Juniper is an important species for biodiversity, so it is imperative to understand the abiotic and biotic drivers of emergent P. austrocedri infection to inform detection, containment and conservation strategies to manage juniper populations across the full extent of its range. As management of UK juniper populations is primarily conducted at a local level, we investigated field scale drivers of disease – in three, geographically separate populations with different infection histories. Variation in the proportion of juniper showing symptoms - discoloured or dead foliage – was measured using stratified sampling across along key environmental gradients within each 100-hectare population. Potential predictors of infection included altitude, slope, distance to nearest watercourse, soil moisture (mean percentage volumetric water content), area of red deer browsing damage and area of commonly associated vascular plant species. We assessed support in the data for alternative models explaining the spatial distribution of P. austrocedri symptoms using full subset covariate selection and Deviance Information Criteria (DIC). Despite differences in environmental gradients and infection histories between populations, area of juniper symptomatic for P. austrocedri increased with waterlogging, increasing with soil moisture in sites where soils had higher peat or clay contents, and decreasing with proximity to watercourses where sites had shallower, sandier soils. Furthermore, we identified common taxa in the associated plant community that correlated with increased area of symptoms and could be used by land managers as indicators to identify microsites at high risk of infection, enabling site-specific tailoring of disease management strategies. Such strategies could include prioritising detection inspections in microsites with high water tables and high grazing pressure (guided by indicator taxa), limiting soil disturbance in wet microsites and creating sites for natural regeneration in drier microsites, to minimise pathogen spread and maximise the resilience of existing juniper populations.

中文翻译：

---

土壤水分的小规模变化导致入侵森林病原体感染脆弱的杜松种群

摘要 卵菌植物病原体 Phytophthora austrocedri 是一种侵略性的桧树杀手，自 1940 年代以来，阿根廷的智利雪松 (Austrocedrus chilensis) 和现在的英国普通杜松 (Juniperus community sl) 造成严重死亡。在 2000 年代初期首次观察到英国主要杜松种群的快速死亡。2012 年，导致死亡的病原体被确认为 P. austrocedri，现在已在苏格兰和英格兰的杜松种群中广泛检测到该病原体——但并非无处不在。尽管杜松在北半球广泛分布，但英国的南方松的发病率仍然是全球杜松种群中唯一确诊的感染。杜松是生物多样性的重要物种，因此必须了解紧急 P. 的非生物和生物驱动因素。austrocedri 感染以告知检测、遏制和保护策略，以管理其整个范围内的杜松种群。由于英国杜松种群的管理主要在地方层面进行，我们调查了疾病的田间规模驱动因素 - 在三个具有不同感染历史的地理上不同的种群中。使用分层抽样沿每 100 公顷种群内的关键环境梯度，测量出现症状（变色或枯叶）的杜松比例的变化。感染的潜在预测因素包括海拔高度、坡度、到最近河道的距离、土壤湿度（平均体积含水量）、马鹿食害面积和通常相关的维管植物物种面积。我们使用完整子集协变量选择和偏差信息标准 (DIC) 评估了替代模型对解释 P. austrocedri 症状空间分布的数据支持。尽管种群之间的环境梯度和感染历史存在差异，但对 P. austrocedri 有症状的杜松面积随着水涝而增加，在泥炭或粘土含量较高的地方随着土壤湿度增加，并随着靠近水道而减少，那里的水道较浅、沙质较多土壤。此外，我们在相关植物群落中确定了与症状面积增加相关的常见分类群，土地管理者可以将其用作指标来识别高感染风险的微型地点，从而能够针对特定地点定制疾病管理策略。