Understanding the role of fog in forest hydrology: stable isotopes as tools for determining input and partitioning of cloud water in montane forests

Understanding the hydrology of tropical montane cloud forests (TMCF) has become essential as deforestation of mountain areas proceeds at an increased rate worldwide. Passive and active cloud-water collectors, throughfall and stemflow collectors, visibility or droplet size measurements, and micrometeorological sensors are typically used to measure the fog water inputs to ecosystems. In addition, stable isotopes may be used as a natural tracer for fog and rain. Previous studies have shown that the isotopic signature of fog tends to be more enriched in the heavier isotopes 2 Ha nd 18 O than that of rain, due to differences in condensation temperature and history. Differences between fog and rain isotopes are largest when rain is from synoptic-scale storms, and fog or orographic cloud water is generated locally. Smaller isotopic differences have been observed between rain and fog on mountains with orographic clouds, but only a few studies have been conducted. Quantifying fog deposition using isotope methods is more difficult in forests receiving mixed precipitation, because of limitations in the ability of sampling equipment to separate fog from rain, and because fog and rain may, under some conditions, have similar isotopic composition. This article describes the various types of fog most relevant to montane cloud forests and the importance of fog water deposition in the hydrologic budget. A brief overview of isotope hydrology provides the background needed to understand isotope applications in cloud forests. A summary of previous work explains isotopic differences between rain and fog in different environments, and how monitoring the isotopic signature of surface water, soil water and tree xylem water can yield estimates of the contribution of fog water to streamflow, groundwater recharge and transpiration. Next, instrumentation to measure fog and rain, and methods to determine isotopic concentrations in plant and soil water are discussed. The article concludes with the identification of some of the more pressing research questions in this field and offers various suggestions for future research. Published in 2010 by John Wiley & Sons, Ltd.

[1]  R. Matthews,et al.  Fog drip as a source of groundwater recharge in northern Kenya , 1988 .

[2]  Coastal fog and its relation to groundwater in the IV region of northern Chile , 1989 .

[3]  M. K. Landon,et al.  Comparison of the stable-isotopic composition of soil water collected from suction lysimeters, wick samplers, and cores in a sandy unsaturated zone , 1999 .

[4]  L. A. Bruijnzeel,et al.  Comparison of passive fog gauges for determining fog duration and fog interception by a Puerto Rican elfin cloud forest , 2011 .

[5]  J. McDonnell,et al.  Deuterium variations in storm rainfall: Implications for stream hydrograph separation , 1990 .

[6]  Edward R. Cook,et al.  The D/H ratios of sap in trees: implications for water sources and tree ring D/H ratios , 1985 .

[7]  G. Goldstein,et al.  Partitioning of soil water among canopy trees in a seasonally dry tropical forest , 1999, Oecologia.

[8]  M. V. Marzol-Jaén.  Tropical Montane Cloud Forests: Historical background of fog water collection studies in the Canary Islands , 2011 .

[9]  S. Gingerich,et al.  The influence of microclimates and fog on stable isotope signatures used in interpretation of regional hydrology: East Maui, Hawaii , 2002 .

[10]  M. Sklash,et al.  A conceptual model of watershed response to rainfall, developed through the use of oxygen-18 as a natural tracer , 1976 .

[11]  K. Révész,et al.  A method to extract soil water for stable isotope analysis , 1990 .

[12]  S. Ingebritsen,et al.  An isotope hydrology study of the Kilauea volcano area, Hawaii , 1993 .

[13]  Stable isotopes in rainfall and fog in the Luquillo Mountains, eastern Puerto Rico: a preliminary study. , 2001 .

[14]  I. Clark,et al.  Environmental Isotopes in Hydrogeology , 1997 .

[15]  Todd E. Dawson,et al.  Foliar water uptake: a common water acquisition strategy for plants of the redwood forest , 2009, Oecologia.

[16]  T. Giambelluca,et al.  Canopy water balance of windward and leeward Hawaiian cloud forests on Haleakalā, Maui, Hawai'i , 2011 .

[17]  Patrick Bützberger,et al.  Vertical fogwater flux measurements above an elevated forest canopy at the Lägeren research site, Switzerland , 2003 .

[18]  I. Fung,et al.  “Amount effect” of water isotopes and quantitative analysis of post‐condensation processes , 2008 .

[19]  J. Nagel.  Fog precipitation on table mountain , 1956 .

[20]  G. B. Allison,et al.  The distribution of deuterium and 18O in dry soils: 1. Theory , 1983 .

[21]  N. Ingraham,et al.  Effects of surface area and volume on the rate of isotopic exchange between water and water vapor , 1993 .

[22]  R. Saxena.  Estimation of Canopy Reservoir Capacity and Oxygen-18 Fractionation in Throughfall in a Pine Forest , 1986 .

[23]  N. Ingraham,et al.  Isotopic assessment of the hydrologic importance of fog deposition on tall snow tussock grass on southern New Zealand uplands. , 2000 .

[24]  S. Gedzelman,et al.  Modeling the isotopic composition of precipitation , 1994 .

[25]  A. Longinelli,et al.  Oxygen isotopic composition of fogs and rains from the North Atlantic , 2005, Experientia.

[26]  L. Bruijnzeel.  Hydrology of tropical montane cloud forests: A Reassessment , 2001 .

[27]  L. Bruijnzeel,et al.  Hydrometeorology of tropical montane cloud forests: emerging patterns , 2011 .

[28]  W. Dansgaard.  Stable isotopes in precipitation , 1964 .

[29]  T. Glickman,et al.  Glossary of Meteorology , 2000 .

[30]  T. Dawson.  Water sources of plants as determined from xylem-water isotopic composition: perspectives on plant competition, distribution, and water relations. , 1993 .

[31]  C. D’Antonio,et al.  Summer water use by California coastal prairie grasses: fog, drought, and community composition , 2005, Oecologia.

[32]  A. P. Williams,et al.  Significance of summer fog and overcast for drought stress and ecological functioning of coastal California endemic plant species , 2009 .

[33]  A. Meesters,et al.  Estimating fog deposition at a Puerto Rican elfin cloud forest site: comparison of the water budget and eddy covariance methods , 2006 .

[34]  J. Calvo-Alvarado,et al.  A comparison of the performance of three types of passive fog gauges under conditions of wind‐driven fog and precipitation , 2011 .

[35]  J. Gat,et al.  Recycling of water in the Amazon Basin: An isotopic study , 1979 .

[36]  R. Gonfiantini.  Chapter 3 – ENVIRONMENTAL ISOTOPES IN LAKE STUDIES , 1986 .

[37]  Matthias Steiner,et al.  Challenges in obtaining reliable measurements of point rainfall , 2007 .

[38]  L. Sternberg,et al.  Using stable isotopes to determine sources of evaporated water to the atmosphere in the Amazon basin , 1996 .

[39]  Frederick N. Scatena,et al.  Tropical montane cloud forests : science for conservation and management , 2011 .

[40]  T. Dawson,et al.  WATER SOURCES USED BY DIDYMOPANAX PITTIERI AT DIFFERENT LIFE STAGES IN A TROPICAL CLOUD FOREST , 1998 .

[41]  R. Burkard,et al.  Ion fluxes from fog and rain to an agricultural and a forest ecosystem in Europe , 2002 .

[42]  J. Wallace,et al.  Measurements of transpiration in four tropical rainforest types of north Queensland, Australia , 2007 .

[43]  Douglas T. Fischer,et al.  Evaluating patterns of fog water deposition and isotopic composition on the California Channel Islands , 2007 .

[44]  G. Walker,et al.  Extraction of water from Eucalyptus trees for analysis of deuterium and oxygen‐18: laboratory and field techniques , 1993 .

[45]  J. Jouzel,et al.  Isotopic study of hail , 1975 .

[46]  M. Scholl,et al.  The stable isotope amount effect: New insights from NEXRAD echo tops, Luquillo Mountains, Puerto Rico , 2009 .

[47]  H. Craig.  Isotopic Variations in Meteoric Waters , 1961, Science.

[48]  T. Giambelluca,et al.  Cloud water in windward and leeward mountain forests: The stable isotope signature of orographic cloud water , 2007 .

[49]  G. Lovett,et al.  Cloud Droplet Deposition in Subalpine Balsam Fir Forests: Hydrological and Chemical Inputs , 1982, Science.

[50]  C. Leibundgut,et al.  Influence of vegetation structure on isotope content of throughfall and soil water , 2000 .

[51]  Yiping Zhang,et al.  Using stable isotopes to determine sources of fog drip in a tropical seasonal rain forest of Xishuangbanna, SW China , 2007 .

[52]  Faculteit der Aard en Levenswetenschappen,et al.  An ecohydrological and soils study in a montane cloud forest in the National Park of Garajonay, La Gomera (Canary Islands, Spain) , 2007 .

[53]  Boris Sevruk,et al.  Estimation of Wind-Induced Error of Rainfall Gauge Measurements Using a Numerical Simulation , 1999 .

[54]  James M. Buttle,et al.  Fundamentals of Small Catchment Hydrology , 1998 .

[55]  G. Gerold,et al.  Tropical Montane Cloud Forests: Hydrometeorological patterns in relation to montane forest types along an elevational gradient in the Yungas of Bolivia , 2011 .

[56]  P. Maloszewski,et al.  DETERMINING THE TURNOVER TIME OF GROUNDWATER SYSTEMS WITH THE AID OF ENVIRONMENTAL TRACERS 1. Models and Their Applicability , 1982 .

[57]  Donald L. Phillips,et al.  Uncertainty in source partitioning using stable isotopes , 2017, Oecologia.

[58]  J. Ehleringer,et al.  Water extraction times for plant and soil materials used in stable isotope analysis. , 2006, Rapid communications in mass spectrometry : RCM.

[59]  M. Sklash,et al.  The Role Of Groundwater In Storm Runoff , 1979 .

[60]  R. Matthews,et al.  The importance of fog-drip water to vegetation: point Reyes Peninsula , 1995 .

[61]  W. Gburek,et al.  Evaluation of mean residence time in subsurface waters using oxygen-18 fluctuations during drought conditions in the mid-Appalachians , 2002 .

[62]  K. Weathers,et al.  Two new ground-level cloud water sampler designs which reduce rain contamination , 1987 .

[63]  M. Leng,et al.  Tracing water paths through small catchments under a tropical montane rain forest in south Ecuador by an oxygen isotope approach , 2005 .

[64]  The Relevance of Fog for the Vegetation: is it the Water or the Nutrients That Matter? , 2007 .

[65]  Silvia E. Newell,et al.  Seasonal variation in the stable isotopic composition of precipitation in the tropical montane forests of Monteverde, Costa Rica , 2005 .

[66]  H. Oeschger,et al.  Correlation of 18O in precipitation with temperature and altitude , 1980, Nature.

[67]  W. Eugster,et al.  Using eddy covariance and stable isotope mass balance techniques to estimate fog water contributions to a Costa Rican cloud forest during the dry season , 2011 .

[68]  J. Gat.  Atmospheric water balance : the isotopic perspective , 2000 .

[69]  L. Araguás‐Araguás,et al.  Isotopic Patterns in Modern Global Precipitation , 2013 .

[70]  Dan Yakir,et al.  Using stable isotopes of water in evapotranspiration studies , 2000 .

[71]  J. Wallace,et al.  Precipitation interception in Australian tropical rainforests: II. Altitudinal gradients of cloud interception, stemflow, throughfall and interception , 2007 .

[72]  J. Jouzel,et al.  Stable Isotopes in Hailstones. Part I: The Isotopic Cloud Model , 1982 .

[73]  C. Tobón,et al.  Precipitation measurement and derivation of precipitation inclination in a windy mountainous area in northern Costa Rica , 2011 .

[74]  J. Turner,et al.  Isotopic exchange in soil water , 1998 .

[75]  T. Dawson.  Fog in the California redwood forest: ecosystem inputs and use by plants , 1998, Oecologia.

[76]  R. Matthews,et al.  A stable isotopic study of fog: the Point Reyes Peninsula, California, U.S.A. , 1990 .

[77]  G. B. Allison,et al.  The distribution of deuterium and 18O in dry soils 2. Experimental , 1983 .

[78]  J. Ehleringer,et al.  Plants, Isotopes and Water Use: A Catchment-Scale Perspective , 1998 .

[79]  Peter J. Thorburn,et al.  Combining measurements of transpiration and stable isotopes of water to determine groundwater discharge from forests , 1993 .