Tropical Mountain Areas Research Articles

Andes mountains and human dimensions of global change, an overview

As the international community is gearing towards shifting values andattitudes making adjustments in trending environmental protectioncampaigns, the accepted paradigm points towards the need to minimize theimpacts on mountain landscapes subjected to climate change due to globalwarming. Hitherto, research policy and the subsequent funding for proposalsdealing with climate change have emphasized the physical dimension,mainly on the cryosphere with glacial retreat and glacier ablation, and on thehydrosphere with lack or rain-fed snow, erratic precipitation, diminishingwater bodies and minimized aquifers. It is just recently, however, that thehuman dimension has been incorporated as a major pillar for ourunderstanding of landscape change and the recent emphasis for fundedresearch.In the tropical mountain areas of the Americas, this social sciencesapproach to study climate change is particularly important, because of theancient imprint on the land has often taken as an anecdotal outcome of sorts,whereby the use of different strategies, Andean communities have copedwith changes in the land for many reasons, including climate change. Theneoliberal policies that facilitated the opening of free market economies intoonce isolated mountain systems are been tested in scenarios of poverty,marginality and neglect. Andean communities are facing major changes, notonly due to global climate change, but particularly because of the impact ofglobalization in their ways of life. Entire livelihoods are threatened with the

Topographic and spatial controls of palm species distributions in a montane rain forest, southern Ecuador

The northern Andes harbour a flora that is as species-rich or even richer than the 18-times larger lowland Amazon basin. Gaining an understanding of how the high species richness of the Andean region is generated and maintained is therefore of particular interest. Environmental sorting due to elevational gradients in climate has been emphasized as a driver of vegetation distribution and plant community assembly in tropical mountain areas such as the Andes for two centuries, while alternative mechanisms have been little studied. Here, we investigated the importance of topography and spatial location as factors controlling species distributions in a palm community in a montane rain forest landscape in the Andes of southern Ecuador (1900–2150 m above sea level). Eleven species were present: Aiphanes verrucosa, Ceroxylon parvifrons, Chamaedorea pinnatifrons, Dictyocaryum lamarckianum, Euterpe precatoria, Geonoma densa, Geonoma orbignyana, Geonoma paradoxa, Prestoea acuminata and Wettinia aequatorialis. To study their spatial distribution, forty 250 m2 (5 × 50 m2) plots were laid out perpendicular to four paths that were categorized into three areas and two topographic units (ridges and gullies). Mantel tests and indicator species analysis showed that both topography and spatial location imposed strong controls on palm species distributions at the study site. Our results suggest that species distributions in the studied montane forest landscape were partly determined by the species’ habitat requirements, but also by unknown spatial effects. Although a number of possible explanations exist for the latter, such as unmeasured environmental variables and historical disturbance events, we believe dispersal limitation is likely to be involved. Furthermore, although the gully- or ridge-association of some species corresponded to their general elevational ranges in southern Ecuador, this was not the case for other species. Based on such considerations, we conclude that elevational climatic gradients are likely to only form part of the explanation for the topographic effects on palm species distributions at the study site. Other factors must also be involved, notably wind-exposure and hydrology, as discussed for lowland palm communities. Our results show that to understand plant community assembly in the tropical montane forests of the Andes it is too simple to focus just on environmental sorting by elevational climatic gradients.

Land degradation and soil and water conservation in tropical highlands

Land degradation is not uniform, even in the same landscape, but nevertheless an overall consensus seems to grow on the fact that many areas are under way of rehabilitation. It is a debateable question whether the improving areas are improving because of interventions—or whether this has more to do with processes of innovation and adaptation. The international symposium ‘HighLand2006’ on land degradation and land rehabilitation, held in Mekelle (Ethiopia), from 21 to 25 September 2006, created a forum for those conducting research in East African Highlands as well as in similar regions around the globe to discuss findings. Tropical highlands (>1000 m a.s.l.) cover 4.5 million km 2 with an average population density of 33 inhabitants km −2. Nearly all tropical highlands suffer from land degradation, especially medium to very high water erosion. Exchange of experiences during in-door sessions and excursions led to results which are condensed in this special issue. Studies presented tend to invalidate hypotheses on irreversibility of land degradation in tropical mountain areas. Circumstances are that in highly degraded environments, with high pressure on the land, no other alternatives are left open but to improve land husbandry; and that this is particularly successful in places where decision making processes at different levels in society give the highest priority to the implementation of soil and water conservation and other land rehabilitation, in situ and at catchment level.

Environmental change, geomorphic processes and land degradation in tropical highlands

Abstract The international symposium ‘HighLand2006’, held in Mekelle (Ethiopia), from 21 to 25 September 2006, was the second time that Ethiopia could host a major international scientific event on geomorphological processes. HighLand2006 created a forum for those conducting research on the impacts of environmental change on geomorphic processes and land degradation in East African highlands as well as in similar regions around the globe. Discussions of results and exchange of experiences during indoor sessions as well as excursions have resulted in this distinctive set of scientific papers. The two main questions addressed in this special issue, through case studies in tropical mountain areas on all continents are: 1. How have environmental changes impacted the type and intensity of geomorphic processes in tropical mountains since late Pleistocene times? The answer to this question is strongly linked to our knowledge on changes in climate, vegetation cover, human activities, hydrology, hillslope and fluvial processes for such environments. 2. Which factors control the intensity of land degradation, its on-site and off-site impacts in tropical mountains? This question addresses the role of natural and anthropogenic factors in the degradation of the vegetation cover and in controlling the intensity of hydrological processes, soil erosion, landsliding, reservoir sedimentation and flooding. In parallel with this special Catena issue, a number of selected papers on land degradation and its mitigation in tropical highlands are presented in a special issue of Soil & Tillage Research.

Restoring dense vegetation can slow mountain erosion to near natural benchmark levels

Tropical mountain areas may undergo rapid land degradation as demographic growth and intensified agriculture cause more people to migrate to fragile ecosystems. To assess the extent of the resulting damage, an erosion rate benchmark against which changes in erosion can be evaluated is required. Benchmarks reflecting natural erosion rates are usually not provided by conventional sediment fluxes, which are often biased due to modern land use change, and also miss large, episodic events within the measuring period. To overcome this, we combined three independent assessment tools in the southern Ecuadorian Andes, an area that is severely affected by soil erosion. First, denudation rates from cosmogenic nuclides in river sediment average over time periods of 1–100 k.y. and establish a natural benchmark of only 150 ± 100 t km −2 yr −1 . Second, we find that land use practices have increased modern sediment yields as derived from reservoir sedimentation rates, which average over periods of 10–100 yr to as much as 15 × 10 3 t km −2 yr −1 . Third, our land cover analysis has shown us that vegetation cover exerts first-order control over present-day erosion rates at the catchment scale. Areas with high vegetation density erode at rates that are characteristically similar to those of the natural benchmark, regardless of whether the type of vegetation is native or anthropogenic. Therefore, our data suggest that even in steep mountain environments sediment fluxes can slow to near their natural benchmark levels with suitable revegetation programs. A set of techniques is now in place to evaluate the effectiveness of erosion mitigation strategies.

Tracer tests, hydrochemical and microbiological investigations as a basis for groundwater protection in a remote tropical mountainous karst area, Vietnam

The Tam Duong karst area in NW Vietnam is among the poorest and remotest regions in the country. The local population largely depends on water from two main karst springs. Due to agricultural activity and untreated domestic wastewaters, the spring water is often microbiologically contaminated. In order to provide a scientific basis for groundwater protection in the area, different field methods have been applied including hydrogeological framework investigations, tracer tests, and hydrochemical and microbiological sampling and analyses. All methods had to be adapted to the conditions of a poor and remote area. These adaptations included, amongst other measures, the use of a portable microbiological water_testing kit and the involvement of the local population in the sampling campaign. The tracer tests showed simple and direct connections between two important swallow holes and the two main springs, and made it possible to determine the linear groundwater flow velocities, which are extremely high (up to 875 m/h). The hydrochemical and microbiological data confirmed the strong impact of the streams sinking into the swallow holes on the spring water quality. Future groundwater source protection strategies should consequently focus on the reduction of polluting activities near the sinking streams and within their catchment areas.

Cloud detection in the Tropics--a suitable tool for climate-ecological studies in the high mountains of Ecuador

The detection of clouds and the analysis of cloud frequency play an important role for operational weather prediction as well as for climate-ecological studies. A threshold technique for cloud detection in the tropical mountainous area of Ecuador is presented which is based on National Oceanic and Atmospheric Administration Advanced Very High Resolution Radiometer (NOAA-AVHRR) data. Cloud classification is performed for both day and night overpasses by applying several threshold tests which also include ancillary terrain information. From a set of 155 images, maps of relative cloud frequency are calculated for Ecuador and adjacent areas as well as the central study area of an ecological project in southern Ecuador (Loja). Results show a clear relation between topography, main airflow and cloudiness due to barrage and lee-effects. The spatial extension of high mountain ecosystems such as the Ecuadorian Páramo has been proven to be significantly influenced by the spatial pattern of cloud frequency.

Assessment of shoreline changes in the western side of Zanzibar channel using satellite remote sensing

The present study uses a satellite remote sensing approach for assessing coastal sediment dynamics in the western side of the Zanzibar channel, Tanzania. Four Landsat images (1986, 1998, 1999 and 2000) were used for the study. Investigation of the four images revealed that the Ruvu delta north of the river mouth has been growing rapidly, especially between 1986 and 1998, with an annual northward linear growth rate of about 133 m year−1 and an annual areal growth rate of about 1 km2 every 3 years. The study identified a palaeo-shoreline feature that is parallel to the present shoreline and located about 1.9 km inland from the present shoreline. An important sediment contributor to river Ruvu is derived from the Uluguru Mountains, a tropical mountainous area located about 200 km from the coastline of the Tanzania mainland. The working hypothesis is that either the observed growth of the delta occurred at a gradual rate between 1986 and 1998 or it was mainly an episodic event related to the extreme rainfall events such as the 1997/98 El Niño–Southern Oscillation (ENSO) event, which was associated with extreme rainfall and widespread landslides.

The use of caesium-137 to estimate agricultural erosion on steep slopes in a tropical watershed

The estimation of erosion and sediment delivery rates in tropical mountain watersheds is difficult and most of the methods widely used for estimating soil erosion over large areas have serious limitations. The 137 Cs approach has potential for quantifying soil erosion because it can provide retrospective estimates of long-term (since 1963) net sediment redistribution relatively quickly. Despite its great potential, 137 Cs has not yet been used in an extensive, reconnaissance level survey of erosion in complex tropical mountain environments. The objective of this study was to examine the applicability of the 137 Cs method to estimate erosion on steep tropical agricultural lands (23 to 80% slopes) in the Nizao watershed, a humid, tropical mountain area of the Dominican Republic. In this study we (i) examine the variation of 137 Cs in ten reference sites - eight coffee groves and two forested sites - and (ii) estimate erosion from 14 cultivated fields. The soil pool of 137 Cs ranged from to 150 to 192 mBq cm -2 on reference sites with minimal erosion. Variability among reference sites was less than expected for such complex mountain terrain. The variability within coffee and forested reference (average CV = 28%) sites was similar to the variability found on grassland and forested reference sites in the temperate zone. The estimated annual soil loss from 14 sampled fields ranged from 6 to 61 t ha -1 year -1 with an overall mean of 26 t ha -1 year -1 . Overall, the soil erosion estimates found using the 137 Cs method were much lower than those often assumed for such steep tropical hillsides. These erosion estimates account for soil loss since 1963 only and it seems likely that soil losses may have been much higher in earlier decades immediately after initial forest clearing earlier in the 20th century.

Late Quaternary glaciation of the Cordillera Real, Bolivia

AbstractGlacial geological studies in tropical mountain areas of the Southern Hemisphere can be used to address two issues of late Pleistocene climate change: the global synchroneity of deglaciation and the magnitude of temperature reduction in the tropics. Radiocarbon dates from the Cordillera Real and from other areas in Perú and Bolivia suggest that late Pleistocene glaciation culminated between 14 000 and 12 000 yr BP, followed by rapid deglaciation. Because deglaciation was apparently synchronous with that in Northern Hemisphere regions, insolation change at high latitudes may not have been the only factor that produced global deglaciation at this time. Late Pleistocene glaciation in the Cordillera Real culminated when precipitation was 200 mm yr−1 higher and temperatures were 3.5° ±1.6°C lower than today; this produced an equilibrium‐line altitude depression of about 300 ± 100 m on the western side of the cordillera. Prior to this, conditions were drier and probably at least as cold. However, the lack of moraines in the Cordillera Real dated to the Last Glacial Maximum (ca. 18000 yr BP) precludes using the equilibrium‐line altitude method to quantitatively evaluate the discrepancy between warm sea‐surface temperatures and cold terrestrial conditions reconstructed with other proxies for this time period.

Changes in Mountain Climate and Glacio-Hydrological Responses

Paleoclimatological and historical evidence shows that mountain areas undergo major changes in glacio-hydrological and ecological conditions in response to changes in climate. The question of the relative intensity of these changes, compared with conditions in adjacent lowlands has received little attention, yet this issue is crucial to appropriate interpretations at regional and local scales of global climate model simulations of possible future climates. Global models necessarily represent the orography of mountain areas in a highly simplified manner and model outputs reflect this in the generalized nature of the results. Accordingly, a review has been undertaken of the evidence for past changes in mountain climatic conditions. The physical basis of high-altitude effects is briefly considered in the altitudinal variations of temperature lapse rates, solar radiation, and precipitation amounts, especially snowfall and snow cover. Observational and proxy evidence of climatic change is discussed for three time scales. Long-term evidence of shifts of vegetation and snowline boundaries during the Last Glacial Maximum ca. 18,000 B.P. shows a significant discrepancy between the inferred 5-60C cooling of tropical mountain areas based on glaciological and vege- tational evidence, versus sea-surface temperature reduction of only 20C inferred from planktonic foraminifera. Possible reasons for this paradox are discussed. Historical records of glaciological conditions during the Little Ice Age interval in Europe (ca. A.D. 1550-1850) are summarized and recent instrumental records of meteorological-hydrological conditions are discussed using examples from the Rocky Mountains of Colorado and the European Alps. These comparisons are briefly discussed in the context of model simulations for the climatic effects of increased concentrations of atmospheric greenhouse gases. Modeling studies are urgently required for impact assessment of potential hydro-meteorological changes in mountain areas.

Some effects of giant Andean stem-rosettes on ground microclimate, and their ecological significance

The effect of giant Andean stem-rosettes (Coespeletia lutescens) on air and soil temperatures was studied in the Paramo de Piedras Blancas (Venezuela) at 4265 and 4385 m altitude during the dry season, which is the coldest season in this tropical mountain area. Maximum air temperatures beneath a plant canopy were only slightly higher than in the open. Minimum temperatures below the stem-rosettes were 4.7° to 7.0°C higher than in the open. This substantially reduced the intensity of nightly freezing. Soil temperature minima at 20 cm depth were 2.4° to 4.2°C higher below plants, but maxima were somewhat lower than in bare soil. These microclimatic alterations are ecologically significant for stemprosette seedlings, which should have a higher probability of survival due to the reduced frequency of frost and needle ice formation below large plants. Warmer soils at night should also result in greater water uptake by seedlings during the early morning hours, thus reducing dry-season mortality.

A comparison of birds inhabiting pine plantation and indigenous forest patches in a tropical mountain area

Extensive changes in land use of afromontane woodlands are currently taking place, where indigenous forests are cleared for plantations of exotic conifers. The consequent impact on the avifauna was assessed in a mountain forest area in Kenya. The native bird fauna was severely depauperated where changes in forestry had taken place in terms of both number of species and densities. Forest specialist species fared worse than forest generalist species. Species with special habitat requirements were unaffected, probably because their habitat had not been changed. The results also suggest that pine plantations in Africa may extend the wintering range for some Palearctic migrant species.

International Symposium on Ecology of the Development of Tropical and Subtropical Mountain Areas, held in Chengdu, China, during 21–24 October 1985

International Symposium on Ecology of the Development of Tropical and Subtropical Mountain Areas, held in Chengdu, China, during 21–24 October 1985

A study of pulmonary function among Indians and assessment of the Wright peak flow meter in relation to spirometry for field use.

The use of the Wright peak flow meter is becoming increasingly popular for a quick assessment of pulmonary function in the field (1-5). The instrument is portable, simple to use, and fairly accurate. Various difficulties in its use in hot humid environments and at high altitudes have been reported elsewhere (6). Nevertheless, the instrument has been found to be reliable and consistent in assessing over-all respiratory function. With the intention of introducing a small portable instrument for measuring respiratory function under difficult field conditions in developing tropical countries and mountainous areas, the present writers have tried to assess the value of the Wright instrument. Under such field conditions, its performance has been studied in 602 subjects (normal and diseased) of both sexes. The inter-relationship of the expiratory peak flow (EPF) has been compared with an accepted test, maximal breathing capacity (MBC). Correlation coefficients between 0.81 and 0.86 in male subjects have been reported by various workers (1-5) and a coefficient of 0.62 in 22 female subjects has been reported by Lockhart and associates ( 4). It is considered necessary to establish the closeness of correlation of EPF with other respiratory tests in Indian subjects who have varying levels of pulmonary function. Using these data an attempt has also been made to predict MBC from EPF and the reverse, for various age groups.