International Hydrology Series (13)
31 - The wet-canopy water balance of a Costa Rican cloud forest during the dry season
from Part III - Hydrometeorology of tropical montane cloud forest
By S. Schmid, University of Bern, Switzerland, R. Burkard, University of Bern, Switzerland, K. F. A. Frumau, VU University, Netherlands, C. Tobón, Universidad Nacional de Colombia, Colombia, L.A. Bruijnzeel, VU University, Netherlands, R. Siegwolf, Paul Scherrer Institute, Switzerland, W. Eugster, ETH Zurich, Switzerland
Edited by L. A. Bruijnzeel, Vrije Universiteit, Amsterdam, F. N. Scatena, University of Pennsylvania, L. S. Hamilton, Cornell University, New York
Book: Tropical Montane Cloud Forests
Print publication: 06 January 2011, pp 302-308
Fog deposition, precipitation, throughfall, and stemflow were measured in a windward tropical montane cloud forest near Monteverde, Costa Rica, for a 65-day period during the dry season of 2003. Net fog deposition was measured directly with the eddy covariance method and amounted to 1.2 ± 0.1 mm day−1 (mean ± standard error). Fog water deposition was 4–7% of incident rainfall for the entire period. Stable isotope concentrations (δ18O and δ 2H) were determined in a large number of samples of each water component. Comparisons between direct fog deposition measurements and the results of a mass-balance model using the stable isotopes as tracers indicated that the latter might be a good tool to estimate fog deposition in the absence of direct measurement under many (but not all) conditions. At 506 mm, measured water inputs over the 65 days (fog plus rain) fell short by 46 mm compared to the canopy output of 552 mm (throughfall, stemflow, and evaporation). The discrepancy is attributed to underestimation of rainfall during conditions of high wind.
Montane cloud forests are widely believed to receive significant extra amounts of water to the water budget by the capture of water from passing fog and low cloud.
51 - Effects of forest disturbance and regeneration on net precipitation and soil water dynamics in tropical montane rain forest on Mount Kilimanjaro, Tanzania
from Part V - Cloud forest water use, photosynthesis, and effects of forest conversion
By M. Schrumpf, Max Planck Institute for Biogeochemistry, Germany, H. V. M. Lyaruu, University of Dar es Salaam, Tanzania, J. C. Axmacher, University College London, UK, W. Zech, University of Bayreuth, Germany, L.A. Bruijnzeel, VU University, Netherlands
The montane rain forest belt on Mt. Kilimanjaro forms an important water source for northern Tanzania that is threatened by both logging and fire. The aim of this study was to investigate consequences of forest fragmentation on various aspects of the water cycle. Soil properties, rainfall, throughfall, and soil water suction were analyzed for mature forest, secondary forest patches, and large clearings. A total of 10 plots located on the south-western slopes of the mountain between 2100 and 2300 m.a.s.l. were monitored from May 2000 until June 2002. Annual rainfall amounts ranged from 2000–2600 mm and showed high spatial and inter-annual variability. Rainfall interception ranged from 3% to 9% of incident rainfall in clearings to a maximum of 32% in forests. In general, soils under mature forest were wettest and showed only minor moisture fluctuations through the year. Soils of secondary forest sites were driest and soil water suction exhibited the largest fluctuations. The difference between the two forest types may reflect a combination of differences in interception, evaporation from the forest floor, and transpiration, because ventilation and radiation penetration can be expected to be enhanced in fragmented secondary forest. In clearings the higher throughfall and presumably lower transpiration rates led to moister conditions compared to adjacent secondary forest sites. Top-soil sand contents of the Andisols differed between sites, with disturbed sites having higher sand contents and consequently lower water contents at similar soil water suctions than did mature forest sites. […]
72 - Tropical montane cloud forests: state of knowledge and sustainability perspectives in a changing world
from Part VII - Cloud forest conservation, restoration, and management issues
By L.A. Bruijnzeel, VU University, Netherlands, M. Kappelle, University of Tennessee, Costa Rica, M. Mulligan, King's College London, UK, F.N. Scatena, University of Pennsylvania, USA
As indicated in the introductory chapter to this book, knowledge of tropical montane cloud forest (TMCF) occurrence, biodiversity, hydrology, and ecological functioning has increased considerably since the ground-breaking publications of Zadroga (1981), Stadtmüller (1987), and the proceedings of the first international symposium on TMCF held in 1993 in Puerto Rico (Hamilton et al., 1995a). Cloud forests continue to be threatened in several ways, notably by their conversion to pasture and various forms of agriculture, as well as by climatic drying – the numerous hydrological and ecological consequences of which are only poorly understood as yet (Bubb et al., 2004; Mulligan and Burke, 2005a; Pounds et al., 2006; Zotz and Bader, 2009).
The collection of chapters in the present volume further advances our knowledge in the three broad and interrelated areas that were defined in the introduction, viz. (i) cloud forest biogeography and biodiversity, (ii) biophysical and ecological processes, and (iii) management and conservation strategies.
As the recognition of the value of TMCFs as treasure houses of biodiversity and as providers of high-quality water continues to increase, an array of initiatives aimed at their conservation has emerged in recent years, often within a Payment for Ecosystem Services (PES) context (Asquith and Wunder, 2008; Muñoz-Piña et al., 2008; Porras et al., 2008; Garriguata and Balvanera, 2009; Tognetti et al., this volume). Such PES schemes, but also land and forest managers and policy-makers in general, need to determine (amongst others) which forests under their jurisdiction are the most diverse and valuable biologically, which ones provide the best water supplies, which forests are the most vulnerable to climate change or most threatened by encroachment, and which degraded TMCFs have the best chances for rehabilitation.
6 - Global and local variations in tropical montane cloud forest soils
from Part I - General perspectives
By L. Roman, University of Pennsylvania, USA, F.N. Scatena, University of Pennsylvania, USA, L.A. Bruijnzeel, VU University, the Netherlands
Print publication: 06 January 2011, pp 77-89
Although soil resources are widely considered as a major factor that reduces the productivity, stature, and diversity of tropical montane cloud forests (TMCF), systematic comparisons of soil resources within and between TMCF are lacking. This study combines published reports on TMCF soils with new data on the soils and forest structure of the Luquillo Mountains in Puerto Rico to assess the current state of knowledge regarding global and local-scale variation in TMCF soils. At the global scale, soils from 33 TMCF sites and over 150 pedons are reviewed. Compared to soils in humid lowland tropical forests, TMCF soils are relatively acidic, have higher organic matter content, and are relatively high in total nitrogen and extractable phosphorus. Across all sites, significant correlations also exist between mean annual precipitation and soil pH and base saturation, but not between any soil chemical factor and canopy height, site elevation, or air temperature. Although comparisons between TMCF are limited by inconsistent sampling protocols, analysis of available data does indicates that lower montane cloud forests (LMCF) have taller canopies, higher soil pH, lower soil nitrogen, and higher C/N ratios than upper montane cloud forests (UMCF). Within an UMCF in NE Puerto Rico, the abundance of soil nitrogen, carbon, and potassium accounted for 25% to 54% of the variation in canopy height. However, as much as 68% of the variation in stand height could be accounted for when site exposure, slope gradient, and the percent coverage of surface roots were also included in the analysis. […]
25 - Using "biosensors" to elucidate rates and mechanisms of cloud water interception by epiphytes, leaves, and branches in a sheltered Colombian cloud forest
By M. Mulligan, King's College London, UK, A. Jarvis, International Centre for Tropical Agriculture, Colombia, J. González, King's College London, UK, L.A. Bruijnzeel, VU University, the Netherlands
Cloud water interception (CWI) by vegetation is a characteristic hydrological process in tropical montane cloud forests (TMCF). Its magnitude is difficult to measure directly and so artificial collectors tend to be used for comparisons between sites. However, artificial collectors say little about the actual inputs of cloud water (fog) to the vegetation. Scaling inputs via CWI from point measurements up to the watershed scale remains an important challenge. This chapter uses a combination of novel field monitoring techniques and epiphyte biomass measurements to quantify the magnitude and better understand the mechanisms of CWI in a sheltered, continental TMCF in south-western Colombia. Relationships were sought between amounts of fog water captured by complex vegetation structures including branches, leaves, and bryophytic epiphytes, for use in scaling up point measurements of fog water to the watershed scale using a simple GIS-based extrapolation.
Tropical montane cloud forests (TMCF) often occur in hydrologically important headwater areas, and there is a growing recognition of their significance as reliable suppliers of high-quality water to downstream areas, particularly during prolonged rainless periods or where those areas are (seasonally) dry (Zadroga, 1981; Brown et al., 1996; Mulligan and Burke, 2005a,b). Nevertheless, TMCF are, hydrologically speaking, amongst the least known of tropical forest ecosystems and the precise hydrological role of the ubiquitous ground-level cloud (fog) has remained elusive (Bruijnzeel and Proctor, 1995; Bruijnzeel, 2005; cf. Part III, this volume).
49 - Environmental controls on photosynthetic rates of lower montane cloud forest vegetation in south-western Colombia
By M. G. Letts, University of Lethbridge, Canada, M. Mulligan, King's College London, UK, M. E. Rincón-Romero, Universidad del Valle, Colombia, L.A. Bruijnzeel, VU University, Netherlands
A variety of microclimatic and edaphic factors have been shown to limit photosynthetic productivity in tropical montane cloud forest (TMCF) ecosystems. It is now understood that multiple controls may limit photosynthesis within individual TMCFs, and that the relative importance of each control varies between sites. This chapter describes the nutrient status, micro-climate, leaf structural traits and photosynthetic gas-exchange characteristics of lower montane cloud forest (LMCF) vegetation at the Centro de Estudios Ambientales Tambito site, a wet LMCF reserve located on the Pacific slopes of Colombia's Western Cordillera. Neither periodic water shortage nor prolonged waterlogging was observed at Tambito. Total soil nitrogen and available phosphorus were above the range typically observed in lowland evergreen rain forests (LERF), while exchangeable calcium levels were lower. In terms of soil nutrient status, total nitrogen and available phosphorus at Tambito were above the range typically observed in more productive LERF, while exchangeable calcium levels were lower. Leaf nutrient contents observed at Tambito were broadly similar to values observed in LERF. Photosynthetic photon flux density (PPFD) remained well below the light-saturation level for leaf-scale photosynthesis (A) throughout the day during the wet season and for 21 hours day−1 during the dry season. Cloudiness may reduce the competitive advantage of high Amax in canopy leaves, thereby increasing the fitness of alternative traits conferred by low specific leaf area, including nutrient-use efficiency and leaf longevity. Therefore, it was concluded that persistent PPFD limitation of photosynthesis may help to explain the prevalence of sclerophylly in tropical montane cloud forests.
42 - Spatial heterogeneity of throughfall quantity and quality in tropical montane forests in southern Ecuador
from Part IV - Nutrient dynamics in tropical montane cloud forests
By M. Oesker, University of Hohenheim, Germany, J. Homeier, University of Göttingen, Germany, H. Dalitz, University of Hohenheim, Germany, L.A. Bruijnzeel, VU University, Netherlands
Canopy structure and throughfall (TF) were determined in three different forest types within the tropical montane rain forest belt in southern Ecuador. Heterogeneity of TF amounts and selected nutrient concentrations were compared to heterogeneity of canopy structure and tree species diversity. Canopy structure was characterized using hemispheric images and software calculating radiation beneath the canopy, mean leaf angle, and canopy openness. TF was sampled over a 1-year period (November 2001–November 2002), and analyzed for pH, electric conductivity, potassium, calcium, and magnesium. Radiation penetrating through the canopy ranged between 9.7% and 17.2% and gap fractions between 6.1% and 9.5% in the respective forests. At 71%, 85%, and 91% of incident precipitation, TF differed significantly between the three forest types, although standard deviations (SD) were high. The highest heterogeneity in TF (as represented by SD) was found for the forest type with the greatest heterogeneity in canopy structure, and vice versa. Heterogeneity of element concentrations in TF (again represented by their SD) exhibited strong correlations (r2 = 0.912–0.987) with tree species diversity per forest as expressed by the Shannon–Wiener diversity index. Rates of nutrient leaching from seven tree species were determined experimentally. Amounts of elements leached differed between species, and specific patterns were observed per species. These findings suggest that higher tree diversity leads to greater complexity in leaching patterns and to greater heterogeneity in TF nutrient composition. […]
9 - Tropical montane cloud forests in Malaysia: current state of knowledge
from Part II - Regional floristic and animal diversity
By S. Kumaran, WWF-Malaysia, Petaling Jaya, Malaysia, B. Perumal, Wetlands International, Malaysia, G. Davison, WWF-Malaysia, Malaysia, A. N. Ainuddin, Universiti Putra Malaysia, Malaysia, M. S. Lee, WWF-Malaysia, Malaysia, L.A. Bruijnzeel, VU University, the Netherlands
Taking 1500 m elevation as the approximate lower limit of upper montane cloud forest occurrence in Malaysia, 0.72% of the total land area of the country may be considered to be potentially covered by tropical montane cloud forests (TMCF). Delineation of TMCF is not easy due to the interplay of climatic and topographic features (including the "mass-elevation" effect). Some studies have shown that the lifting condensation level (cloud base) occurs around 1200 m.a.s.l. in Peninsular Malaysia, at c. 1800–2000 m on large mountains like Mt. Kinabalu (Borneo), and as low as c. 700 m on small, outlying coastal mountains (e.g. Gunung Silam, Sabah). Published information on the biodiversity of TMCF in Malaysia is scattered. Important tree families in montane forests include Ericaceae, Myrtaceae, Coniferae, Fagaceae, and Lauraceae, which are often blanketed with epiphytes, ferns, bryophytes, and liverworts. About 3000–4000 vascular plant species are found in the montane forests of Peninsular Malaysia and Borneo. There is a distinct montane community amongst most classes of vertebrates and some invertebrates, but the fauna of TCMF is mostly a small sub-set of the overall montane fauna. About 18 mammal species in Borneo and 10 in Peninsular Malaysia are strictly montane but none are truly restricted to cloud forests. Bird diversity is well studied but limited information is available on the number of species that are cloud forest specialists. Patchy records are available for butterflies, moths, mollusks, and herpetofauna. Studies on the capture of cloud water in Malaysian cloud forests are rare. […]
70 - Assessment needs to support the development of arrangements for Payments for Ecosystem Services from tropical montane cloud forests
By S. S. Tognetti, Environmental Science and Policy Consultant, USA, B. Aylward, Ecosystem Economics LLC, USA, L.A. Bruijnzeel, VU University, Netherlands
The willingness of beneficiaries to pay for "ecosystem services" will ultimately depend on confidence in the effectiveness of actions taken to ensure their continued delivery at the watershed scale. Key aspects of effectiveness include: (i) the integrity of ecosystem functioning or processes that support service provision, (ii) whether the impacts or benefits are economically significant at the relevant (watershed) scale, and (iii) the effectiveness of institutional arrangements needed to ensure access to benefits by those who pay for them. The biophysical characteristics of the relevant watershed/ecosystem also have implications for the types of institutional arrangements that are possible or necessary to control access to services. Given the dynamic nature of ecosystems, and the potentially long lag time between multiple causes and effects over large spatial areas, the outcomes of management actions are inherently variable, uncertain, and site-specific. In the absence of adequate site-specific assessment, Payments for Ecosystem Services (PES) initiatives are often based on inappropriate generalizations or even myth regarding the hydrological impact of certain types of land-cover changes. Cloud forests in particular are generally assumed to increase the supply of water because they capture water from clouds, beyond that provided by precipitation. However, there is a need for further site-specific assessments, to better define and quantify the extent to which cloud forests account for additional supplies of water compared to other land-cover types that might replace them (e.g. pasture) under various climatic conditions. […]
30 - Fog gage performance under conditions of fog and wind-driven rain
By K. F. A. Frumau, VU University, Netherlands, R. Burkard, University of Bern, Switzerland, S. Schmid, University of Bern, Switzerland, L.A. Bruijnzeel, VU University, Netherlands, C. Tobón, Universidad Nacional de Colombia, Colombia, J. C. Calvo-Alvarado, Instituto Tecnológico de Costa Rica, Costa Rica
Fog and wind-driven rain (WDR) are difficult to measure separately and reported measurements of "fog" often represent a combination of fog and WDR. In this chapter the term "horizontal precipitation" (HP) is used instead. Understanding of "typical" amounts of HP intercepted by different types of cloud forest is hampered by a lack of comparative information on local fog climatology. Usually some kind of "fog gage" is used to characterize fog occurrence and amounts. Collection efficiencies of three passive fog gages, viz. a wire harp, a modified cylindrical gage (Juvik-type), and a tunnel gage (Daube-type), were derived by comparing the volumes of water collected by the respective gages with cloud water fluxes derived from fog liquid water content (LWC) as measured by a cloud particle spectrometer during conditions of fog at a windward cloud forest site in northern Costa Rica. The collection efficiency of the three gages proved linearly related to the horizontal cloud water flux as measured by the gages themselves. Therefore, no additional information on wind speed, droplet size, and fog LWC was needed. During conditions of HP, relative collection efficiencies were derived by comparing the volumes collected by the respective gages. The modified Juvik gage had an efficiency close to 100%, independently of wind speed and direction. The efficiency of the wire harp depended critically on wind speed, whereas the tunnel gage collected additional precipitation at small precipitation angles and low wind speeds. […]
52 - Changes in soil physical properties after conversion of tropical montane cloud forest to pasture in northern Costa Rica
By C. Tobón, Universidad Nacional de Colombia, Colombia, L.A. Bruijnzeel, VU University, Netherlands, K. F. A. Frumau, VU University, Netherlands, J. C. Calvo-Alvarado, Instituto Tecnológico de Costa Rica, Costa Rica
Within the framework of a larger project studying the hydrological impacts of converting tropical montane cloud forest to pasture in the Tilarán range of northern Costa Rica, physical and hydraulic properties of various volcanic soils were compared in two small watersheds covered with mature lower montane cloud forest and pasture, respectively. In situ and laboratory experiments were conducted to determine trends in soil texture, bulk density, porosity, water retention characteristics, infiltration, and (un)saturated hydraulic conductivities with depth under the two types of land cover. Despite their predominantly sandy texture, the soils were rich in organic matter and non-crystalline material such as allophane. Bulk densities were very low and similar between sites for corresponding soil horizons, except for the pasture top-soil which was more compacted, particularly on cow trails. Soil porosity was very high throughout the profile and dominated by macro- and mesopores, again with the exception of the pasture top-soil and the cow trails. Water retention at a suction of 1500 kPa (permanent wilting point) was very high, except in gravelly C-horizons which had low retention capacity. Amounts of plant-available water (i.e. held at suctions between 10 and 1500 kPa) were also high. Surface infiltration rates were relatively high and dominated by "bypass" flow via macropores in the gravelly horizon (at 20–30 cm depth). Spatial variability in infiltration rates was high in the pasture but less in the forest. Saturated hydraulic conductivity at the soil surface was high in general but considerably reduced in the pasture. […]
54 - Meso-scale climate change due to lowland deforestation in the maritime tropics
from Part VI - Effects of climate variability and climate change
By M. K. Van Der Molen, VU University, Netherlands, H. F. Vugts, VU University, Netherlands, L.A. Bruijnzeel, VU University, Netherlands, F.N. Scatena, University of Pennsylvania, USA, R. A. Pielke, CIRES, University of Colorado, USA, L. J. M. Kroon, Wageningen University and Research Centre, Netherlands
Annual precipitation on the Caribbean island of Puerto Rico has decreased steadily during the twentieth century, on average by 16%. The reduced rainfall manifested itself in the form of regular water rationings for millions of inhabitants during the 1990s. This chapter examines the link between the reduction in precipitation and the land-cover change using a combination of energy balance measurements and meso-scale atmospheric modeling. The explanation of the reduction in precipitation proved to be different than expected. Based on measurements made earlier over rain forest and pasture in Amazonia, a forest-covered island was expected to be cooler because of the higher transpiration of forest compared to grassland. The opposite proved to be the case: transpiration by a coastal wetland forest was less than that of an adjacent, well-watered grassland. In addition, the forest's albedo was 8% lower than that for the grassland. Together, these two factors caused the sensible heat flux over the forest to be twice that over the grassland. The surface energy balance observations over forest and grassland were used in a meso-scale atmospheric circulation model (RAMS) to simulate the meteorological effects of island-wide deforestation. The simulations indicated that the development of a sea breeze during the day dominates the climate on the island. In model runs in which the island was assumed to be completely covered with forest, the sea breeze was considerably stronger than when the vegetation had been transformed to grassland. Along the sea breeze front, convergence caused upward air motions. […]
1 - Setting the stage
By F.N. Scatena, University of Pennsylvania, USA, L.A. Bruijnzeel, VU University, the Netherlands, P. Bubb, UNEP – World Conservation Monitoring Centre, UK, S. Das, UNEP – World Conservation Monitoring Centre, UK
Print publication: 06 January 2011, pp 3-13
The cloudy, wet, and generally difficult terrain of the world's Tropical Montane Cloud Forests (TMCF) has not only made them hydrologically and ecologically unique, but has historically given them some de facto protection compared to other tropical forests. In the late 1970s and early 1980s it became apparent that this de facto protection was diminishing and that TMCF in many parts of the world were rapidly becoming converted or fragmented and in need of protection (LaBastille and Pool, 1978; White, 1983; Stadtmüller, 1987). Indeed, by the early 1990s it was clear that TMCF were high on the list of the world's most threatened terrestrial ecosystems. Moreover, during the period 1981–1990, montane forests were being lost at a rate considerably greater than that estimated for lowland tropical forests (1.1% year−1 vs. 0.8% year−1, respectively; Doumenge et al., 1995). It was also being recognized that the scientific information needed to manage and protect these unique but vulnerable ecosystems was generally lacking (Stadtmüller, 1987).
In response to this information need, an international Symposium on TMCF was held in San Juan, Puerto Rico between 31 May and 5 June 1993. The meeting resulted in a 27-chapter book on the world's TMCFs (Hamilton et al., 1995), which included overview chapters on the hydrology and nutrient dynamics of TMCF (Bruijnzeel and Proctor, 1995) and the importance of TMCF for endemic and threatened birds (Long, 1995), as well as the first in-depth description of guidelines for managing and valuing an especially vulnerable type of TMCF – elfin cloud forest (Scatena, 1995) – and useful summary descriptions of the biogeography of TMCF in widely different settings, including a host of Pacific islands, Sri Lanka, NE Borneo, Mexico, SE Brazil, NW Argentina, and Perú.