{"title":"Transpiration in a sub-tropical ridge-top cloud forest","authors":"G. García-Santos","doi":"10.1016/j.jhydrol.2011.08.069","DOIUrl":null,"url":null,"abstract":"<div><p><span>Laurel forests in the Canary Islands (Spain) survive where humid conditions are guaranteed throughout the year. On peaks and ridges, laurel forest gives way to mixed evergreen tree-heath/beech forest of low stature (“</span><em>fayal</em>–<em>brezal</em><span>”) that has to cope with rapidly changing light, temperature and humidity conditions due to the occurrence of intermittent sunny and foggy periods during the mostly rainless summer. These conditions are poorly understood and there is a lack of information on the interrelations between tree physiological behavior and ambient climatic and soil water conditions in </span><em>fayal</em>–<em>brezal</em>. In this study sap velocities were measured for 2<!--> <!-->years in two dominant tree species (<span><em>Myrica faya</em></span> and <span><em>Erica arborea</em></span>) in a ridge-top forest in the National Park of Garajonay on the island of La Gomera. The resulted average daily stand transpiration was 1.2<!--> <!-->±<!--> <!-->0.12<!--> <!-->mm (416<!--> <!-->mm<!--> <!-->year<sup>−1</sup>). However, the narrow-leaved <em>E. arborea</em> exhibited higher sap velocities than the broad-leaved <em>M. faya</em>. Also, sap velocity increased with stem diameter in <em>E. arborea</em> but not in <em>M. faya</em><span>. Nocturnal flow activity was observed throughout the year and reflected ambient conditions on some occasions, and stem water storage recovery on others. Strong stomatal control in response to increases in vapor pressure deficit was seen in both species. Fog reduced sap velocity from 10% up to 90% but no consistent pattern was found. Soil water uptake during the dry summer (246</span> <!-->mm) was much larger than atmospheric water inputs (41<!--> <!-->mm, rain and fog). The low moisture levels in the top 0.3<!--> <!-->m of the soil had limited influence on transpiration rates indicating that vegetation must have had access to moisture in deeper layers.</p></div>","PeriodicalId":362,"journal":{"name":"Journal of Hydrology","volume":"462 ","pages":"Pages 42-52"},"PeriodicalIF":5.9000,"publicationDate":"2012-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.jhydrol.2011.08.069","citationCount":"17","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Hydrology","FirstCategoryId":"89","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0022169411007335","RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"ENGINEERING, CIVIL","Score":null,"Total":0}
引用次数: 17
Abstract
Laurel forests in the Canary Islands (Spain) survive where humid conditions are guaranteed throughout the year. On peaks and ridges, laurel forest gives way to mixed evergreen tree-heath/beech forest of low stature (“fayal–brezal”) that has to cope with rapidly changing light, temperature and humidity conditions due to the occurrence of intermittent sunny and foggy periods during the mostly rainless summer. These conditions are poorly understood and there is a lack of information on the interrelations between tree physiological behavior and ambient climatic and soil water conditions in fayal–brezal. In this study sap velocities were measured for 2 years in two dominant tree species (Myrica faya and Erica arborea) in a ridge-top forest in the National Park of Garajonay on the island of La Gomera. The resulted average daily stand transpiration was 1.2 ± 0.12 mm (416 mm year−1). However, the narrow-leaved E. arborea exhibited higher sap velocities than the broad-leaved M. faya. Also, sap velocity increased with stem diameter in E. arborea but not in M. faya. Nocturnal flow activity was observed throughout the year and reflected ambient conditions on some occasions, and stem water storage recovery on others. Strong stomatal control in response to increases in vapor pressure deficit was seen in both species. Fog reduced sap velocity from 10% up to 90% but no consistent pattern was found. Soil water uptake during the dry summer (246 mm) was much larger than atmospheric water inputs (41 mm, rain and fog). The low moisture levels in the top 0.3 m of the soil had limited influence on transpiration rates indicating that vegetation must have had access to moisture in deeper layers.
加那利群岛(西班牙)的月桂林全年都能在潮湿的环境中生存。在山峰和山脊上,月桂林让位给低矮的常绿石南/山毛榉混合林(“fayal-brezal”),由于在几乎无雨的夏季出现间歇性的晴天和雾天,这些森林必须应对快速变化的光线、温度和湿度条件。人们对这些条件了解甚少,并且缺乏关于fayal-brezal树木生理行为与环境气候和土壤水分条件之间相互关系的信息。本研究在戈梅拉岛加拉霍内国家公园的一个山脊上的森林中,对两种优势树种(杨梅和埃里卡)进行了为期2年的树液速度测量。平均日林分蒸腾量为1.2±0.12 mm (416 mm - 1)。然而,窄叶杉木的树液速度高于阔叶杉木。树液流速随茎粗的增加而增加,而不随茎粗的增加而增加。全年都观察到夜间水流活动,在某些情况下反映了环境条件,而在其他情况下则反映了茎储水恢复。在这两个物种中,气孔控制对蒸汽压赤字增加的响应都很强。雾将树液速度从10%降低到90%,但没有发现一致的模式。干旱夏季土壤水分吸收量(246 mm)远大于大气水分输入量(41 mm,雨和雾)。土壤顶部0.3米的低水分水平对蒸腾速率的影响有限,这表明植被一定能接触到更深层的水分。
期刊介绍:
The Journal of Hydrology publishes original research papers and comprehensive reviews in all the subfields of the hydrological sciences including water based management and policy issues that impact on economics and society. These comprise, but are not limited to the physical, chemical, biogeochemical, stochastic and systems aspects of surface and groundwater hydrology, hydrometeorology and hydrogeology. Relevant topics incorporating the insights and methodologies of disciplines such as climatology, water resource systems, hydraulics, agrohydrology, geomorphology, soil science, instrumentation and remote sensing, civil and environmental engineering are included. Social science perspectives on hydrological problems such as resource and ecological economics, environmental sociology, psychology and behavioural science, management and policy analysis are also invited. Multi-and interdisciplinary analyses of hydrological problems are within scope. The science published in the Journal of Hydrology is relevant to catchment scales rather than exclusively to a local scale or site.