Epiphytes improve host plant water use by microenvironment modification

1. Epiphytes have the potential to modify the canopy environments in which they grow. Accurately evaluating the impact of epiphytes can be challenging, since plants without epiphytes may also otherwise differ from host plants, and experimental removal is impractical and difficult to replicate in many forests. 2. We studied the impacts of epiphytes (primarily fruticose lichens and Tillandsia spp.) on host plants (Eulychnia saint-pieana and Caesalpinia spinosa) in two fog ecosystems in Chile (Pan de Azucar) and Peru (Atiquipa). These desert ecosystems sustain very high epiphyte loads and depend heavily on fog-water inputs. Using a combination of artificial substrates and epiphyte removals we show significant impacts of epiphytes on their host plants. 3. The presence of epiphytes reduced throughfall volumes, reducing fog and rainfall inputs to the soil beneath host plant canopies. 4. Soil moisture loss rate was increased below cacti after removal of epiphytes from sun-facing but not shade-...1. 附生植物（epiphyte）能够改变其生长所在的冠层环境。精准评估附生植物的影响颇具挑战：一方面无附生植物的植株与宿主植物本身可能存在固有差异，另一方面在多数森林生态系统中，实验性移除附生植物既不可行，也难以重复开展。 2. 我们针对智利阿苏卡潘（Pan de Azucar）与秘鲁阿提基帕（Atiquipa）两处雾生荒漠生态系统中的附生植物（主要为枝状地衣（fruticose lichen）和铁兰属（Tillandsia spp.）植物）及其宿主植物（智利柱属*Eulychnia saint-pieana*与刺云实*Caesalpinia spinosa*）的相互影响展开研究。这些荒漠生态系统承载着极高的附生植物生物量，且高度依赖雾水输入以维持生态功能。我们结合人工基质布设与附生植物移除实验，证实了附生植物对宿主植物存在显著影响。 3. 附生植物的存在会降低穿透雨（throughfall）总量，从而减少输入至宿主植物冠层下方土壤的雾水与降雨量。 4. 从向阳面的仙人掌宿主植株上移除附生植物后，其下方土壤的水分流失速率显著升高，但该效应并未在荫蔽环境下的植株中观测到……