Holdridge Life Zone System Research Articles

Predicting global terrestrial biomes with the LeNet convolutional neural network

Abstract. A biome is a major regional ecological community characterized by distinctive life forms and principal plants. Many empirical schemes such as the Holdridge life zone (HLZ) system have been proposed and implemented to predict the global distribution of terrestrial biomes. Knowledge of physiological climatic limits has been employed to predict biomes, resulting in more precise simulation; however, this requires different sets of physiological limits for different vegetation classification schemes. Here, we demonstrate an accurate and practical method to construct empirical models for biome mapping: a convolutional neural network (CNN) was trained by an observation-based biome map, as well as images depicting air temperature and precipitation. Unlike previous approaches, which require assumption(s) of environmental constrain for each biome, this method automatically extracts non-linear seasonal patterns of climatic variables that are relevant in biome classification. The trained model accurately simulated a global map of current terrestrial biome distribution. Then, the trained model was applied to climate scenarios toward the end of the 21st century, predicting a significant shift in global biome distribution with rapid warming trends. Our results demonstrate that the proposed CNN approach can provide an efficient and objective method to generate preliminary estimations of the impact of climate change on biome distribution. Moreover, we anticipate that our approach could provide a basis for more general implementations to build empirical models of other climate-driven categorical phenomena.

Assessing the Vulnerability of Military Installations in the Coterminous United States to Potential Biome Shifts Resulting from Rapid Climate Change.

Climate-change impacts to Department of Defense (DoD) installations will challenge military mission and natural resource stewardship efforts by increasing vulnerability to flooding, drought, altered fire regimes, and invasive species. We developed biome classifications based on current climate for the coterminous United States using the Holdridge Life Zone system to assess potential change on DoD lands. We validated classifications using comparisons to existing ecoregional classifications, the distribution of major forest types, and tree species in eastern North America. We projected future life zones for mid- and late-century time periods under three greenhouse gas emission scenarios (low-B1, moderate-A1B, and high-A2) using an ensemble of global climate models. To assess installation vulnerability (n = 529), we analyzed biome shifts using spatial cluster analysis to characterize interregional variation, and identified representative installations for subsequent landscape-level analyses. Although mean annual temperatures are expected to increase, installations located in the Northeast, Lake States, and western Great Plains are likely to experience the largest proportional increases in temperature. Accordingly, forest and grassland communities at these installations managed to support a wide range of training, and environmental objectives may be adversely affected by altered disturbance regimes, heat, and moisture stress. However, precipitation is projected to increase in the Northeast and Lake States mitigating some effects of increased temperatures on biological communities. Given the uncertain response to climate change in different ecoregions, additional environmental and stewardship attributes are needed within a decision-support framework to understand vulnerabilities and provide appropriate responses.

Classificação climática para o estado do Amazonas segundo as zonas de vida de Holdridge

Holdridge life zones are based on the relationships among precipitation, temperature, altitude levels and latitude, and they are useful in ecological applications, particularly in tropical areas. This study aimed to perform a climate classification of the Amazonas State cities according to Holdridge’s life zones and compare it with Koppen classification and original vegetation cover of the state. The comparisons were made using confusion matrices elaborated with spatial analysis tools. The results indicate biotemperatures ranging from 22.9 °C to 26.5 °C, increasing from West to East of the state. Five Holdridge life zones were found, tropical moist forest and tropical moist forest / wet forest, occupying about 85% of the state area. Three life zones corresponded 100% with the climate classification Af according to Koppen, and the other life zones reached correspondences of more than 75% with the same climate type. All life zones were found to be in open ombrophilous, dense ombrophilous and campinarana vegetation. In this way, Holdridge life zone system proved to be an important tool for climate classification in the state, corresponding to vegetation maps and to the Koppen climate classification.

CLASSIFICAÇÃO DO ESTADO DO RIO GRANDE DO SUL SEGUNDO O SISTEMA DE ZONAS DE VIDA DE HOLDRIDGE

O clima é a síntese de elementos meteorológicos observados durante um longo período de tempo e possui estreita relação com a vegetação. A classificação climática de Holdridge define zonas de vida representativas para as diferentes regiões da Terra, que refletem a conjuntura destes elementos meteorológicos. Este trabalho objetivou a classificação do estado do Rio Grande do Sul segundo este sistema, visando comparar com a classificação climática de Köppen, bem como as fitogeografias do estado. Com base em uma série histórica não contínua mínima de 25 anos, de 1950 a 1990, de dados pluviométricos e de temperatura, associados às variáveis de latitude e altitude, foi possível calcular e determinar as zonas de vida individualmente para os 496 municípios do estado. Oito zonas de vida foram encontradas, das quais se destacaram: floresta úmida temperada basal (74,0%); floresta muito úmida/floresta úmida temperada basal (13,8%); e floresta úmida/floresta muito úmida temperada basal (8,0%). A relação entre Holdridge e Köppen apresentou correspondência acima de 90% em sete das oito zonas de vida encontradas (87,5% do território do estado), predominantemente com o tipo climático Cfa (clima temperado, com chuva o ano todo e verão quente). Regiões de Estepe e Savana-estépica obtiveram 100% de correspondência com as zonas de vida floresta muito úmida temperada basal e com as respectivas transições com floresta úmida temperada basal. O sistema de zonas de vida de Holdridge mostrou-se uma importante ferramenta para o zoneamento agrossilvicultural do estado, uma vez que houve uma interação satisfatória quando comparado com o sistema de classificação climática de Köppen e com algumas fitogeografias.

Distribution of Costa Rican epiphytic bromeliads and the Holdridge Life Zone System

Detailed distribution maps for the major bromeliad genera native to Costa Rica were prepared bases on the collections in the three largest herbaria of the country and on citations from the literature. Most records are from the montane habitats, probably reflecting the frequent need for moisture by these plants. Vriesea ans Guzmania have been collected mostly in moist lowland habitats. In 1975, Burt-Utley and Utley had hypothesized that the Holdridge Life Zone System should fit the distribution of epiphytic bromeliads because soil (a factor not considered in the System) is not important in their occurrence. However, on average, species were absent in about half of the Life Zones where they were expected to occur according to the Holdridge classification. It is hypothesized that the System failed because epiphytic bromeliad distribution reflects factor interactions rather than humidity, light or temperature individually.

Assessment of projected climate change in the Carpathian Region using the Holdridge life zone system

In this paper, expected changes in the spatial and altitudinal distribution patterns of Holdridge life zone (HLZ) types are analysed to assess the possible ecological impacts of future climate change for the Carpathian Region, by using 11 bias-corrected regional climate model simulations of temperature and precipitation. The distribution patterns of HLZ types are characterized by the relative extent, the mean centre and the altitudinal range. According to the applied projections, the following conclusions can be drawn: (a) the altitudinal ranges are likely to expand in the future, (b) the lower and upper altitudinal limits as well as the altitudinal midpoints may move to higher altitudes, (c) a northward shift is expected for most HLZ types and (d) the magnitudes of these shifts can even be multiples of those observed in the last century. Related to the northward shifts, the HLZ types warm temperate thorn steppe and subtropical dry forest can also appear in the southern segment of the target area. However, a large uncertainty in the estimated changes of precipitation patterns was indicated by the following: (a) the expected change in the coverage of the HLZ type cool temperate steppe is extremely uncertain because there is no consensus among the projections even in terms of the sign of the change (high inter-model variability) and (b) a significant trend in the westward/eastward shift is simulated just for some HLZ types (high temporal variability). Finally, it is important to emphasize that the uncertainty of our results is further enhanced by the fact that some important aspects (e.g. seasonality of climate variables, direct CO2 effect, etc.) cannot be considered in the estimating process.

Comparison and effects of different climate-vegetation models in areas of complex terrain under climate change

Identifying the impacts of climate change is important for conservation of ecosystems under climate change, particularly in mountain regions. Holdridge life zone system and Koppen classification provide two effective methods to assess impacts of climate change on ecosystems, as typical climate-vegetation models. Meanwhile, these previous studies are insufficient to assess the complex terrain as well as there are some uncertainties in results while using the given methods. Analysis of the impacts of the prevailing climate conditions in an area on shifts of ecosystems may reduce uncertainties in projecting climate change. In this study, we used different models to depict changes in ecosystems at 1 km × 1 km resolution in Sichuan Province, China during 1961–2010. The results indicate that changes in climate data during the past 50 years were sufficient to cause shifts in the spatial distribution of ecosystems. The trend of shift was from low temperature ecosystems to high temperature ecosystems. Compared with Koppen classification, the Holdridge system has better adaptation to assess the impacts of climate change on ecosystems in low elevation (0–1000 m). Moreover, we found that changed areas in ecosystems were easily affected by climate change than unchanged areas by calculating current climate condition.

The climate of Carpathian Region in the 20th century based on the original and modified Holdridge life zone system

AbstractThe Holdridge life zone system has already been used a number of times for analysing the effects of climate change on vegetation. But a criticism against the method was formulated that it cannot interpret the ecotones (e.g. forest steppe). Thus, in this paper transitional life zones were also determined in the model. Then, both the original and modified life zone systems were applied for the climatic fields of database CRU TS 1.2. Life zone maps were defined in the Carpathian Region (43.5–50.5° N, 15.5–28° E) for each of five 20-year periods between 1901 and 2000. We estimated correctness of the result maps with another vegetation map using Cohen’s Kappa statistic. Finally, temporal changes in horizontal and vertical distribution of life zones were investigated. The coverage of boreal region decreased with 59.46% during the last century, while the warm temperate region became almost two and a half larger (257.36%). The mean centres of those life zones, which were not related to mountains, shifted northward during the investigation period. In case of the most abundant life zone types, the average distribution elevation increased. Using the modified model, the potential distribution of forest steppe could be also identified.

The Melting Himalayas: Cascading Effects of Climate Change on Water, Biodiversity, and Livelihoods

The Greater Himalayas hold the largest mass of ice outside polar regions and are the source of the 10 largest rivers in Asia. Rapid reduction in the volume of Himalayan glaciers due to climate change is occurring. The cascading effects of rising temperatures and loss of ice and snow in the region are affecting, for example, water availability (amounts, seasonality), biodiversity (endemic species, predator-prey relations), ecosystem boundary shifts (tree-line movements, high-elevation ecosystem changes), and global feedbacks (monsoonal shifts, loss of soil carbon). Climate change will also have environmental and social impacts that will likely increase uncertainty in water supplies and agricultural production for human populations across Asia. A common understanding of climate change needs to be developed through regional and local-scale research so that mitigation and adaptation strategies can be identified and implemented. The challenges brought about by climate change in the Greater Himalayas can only be addressed through increased regional collaboration in scientific research and policy making.

A new statistical dynamic analysis on vegetation patterns in land ecosystems

As complex self-adaptive systems, land ecosystems usually tend to produce intricate vegetation patterns under specific environmental constraints, which have ever puzzled us for decades. In this paper, a universal principle on pattern formation of land ecosystems is highlighted as: a land ecosystem always tries to find an optimal process to acquire maximized flux under a certain constraint or price. The underlying microscopic dynamic mechanism that induces complex vegetation patterns in land ecosystems is then revealed. Based on the Holdridge life zone system, evolutionary dynamic processes and structural classifications of several typical vegetation patterns are then simulated and discussed. Good agreements between theoretical analyses and numerical results are found. This paper demonstrates that the new theoretical analyses and simulation technique can be possibly applied to the whole land ecosystem, not only benefiting academic study on the formation and dynamics of vegetation patterns, but also providing implications for vegetation classification, vegetation protection and soil erosion control.

Biome mapping in India using vegetation type map derived using temporal satellite data and environmental parameters

Development of regional biome models represents a new stage of earth systems modeling. By translating simulated climate variables and actual vegetation boundaries into maps of biomes, these models explicitly link the vegetation and climate patterns together, enabling the determination of trajectories of climate change. Through this research, a new one million scale biome map of India is prepared, based on actual vegetation cover type map derived from wide field sensor onboard Indian remote sensing satellite (IRS WiFS—spatial resolution 200 m) and Holdridge life zone (HLZ) system. A biome level characterization (BLC) model has been developed wherein, temporal satellite data helps to define the phenologically discriminant vegetation cover type, climatic parameters viz., biotemperature, mean annual precipitation and potential evapotranspiration ratio have been used to identify potential life zones and finally describe the biome boundaries based on the vegetation cover type and life zones. The study identifies 35 cover classes and describes 17 vegetation cover types. This is close to the type description given by Champion and Seth [Champion, H.G., Seth, S.K., 1968. A Revised Survey of Forest Types of India. New Delhi Government Publication, New Delhi.] in their forest cover type map. The geographical analysis identifies 19 HLZs seven biomes and 19 sub-biomes in the Indian sub-continent. The dataset is now available for diverse application studies in ecosystem modeling, land cover dynamics and global change.

Valuing the impacts of climate change on protected areas in Africa

This study quantifies the economic costs of climate change impacts on protected areas in Africa. Downscaled results from four Global Circulation Models (GCMs) are used to classify different ecosystems in accordance with the Holdridge Life Zone (HLZ) system. A benefits transfer approach is then used to place an economic value on the predicted ecosystem shifts resulting from climate change in protected areas. The results provide approximations for the impacts on biodiversity in Africa under the “business-as-usual” scenario established by the Intergovernmental Panel on Climate Change (IPCC) for the middle and end of the 21st century. The geographical analysis shows that there are twenty HLZs in Africa and all of them are represented in the protected area network. Three of these HLZs do not change in extent as a result of climate change. Assuming initially that the willingness to pay (WTP) values and the preferences for different ecosystem services remain constant, three of the GCM models show an (undiscounted) negative economic impact of climate change for protected areas in Africa for the year 2100. The worst-case damage scenario totals USD 74.5 million by 2100. However, the model for the year 2065 shows a higher undiscounted value than the present. The finding of positive net impacts from warming is consistent with the predictions of other macro models that show potential gains from warming scenarios.

The possible response of life zones in China under global climate change

The response of natural vegetation to climate change is of global concern. In this research, an aggregated Holdridge Life Zone System was used to study the possible response of life zones in China under doubled atmospheric CO 2 concentration with the input climatic parameters at 0.5×0.5° resolution of longitude and latitude from NCAR regional climate model 2 (RegCM2) coupled with the CSIRO global climate model. The results indicate that the latitudinal distribution of life zones would become irregular because of the complicated climate change. In particular, new life zones, such as subtropical desert (SD), tropical desert (TDE) and tropical thorn woodland (TTW), would appear. Subtropical evergreen broadleaved forest (SEBF), tropical rainforest and monsoon forest (TRF), SD, TDE and TTW zones would appear in the northeastern China. Cool-temperate mixed coniferous and broadleaved forest (CMC) and warm-temperate deciduous broadleaved forest (WDBF) zones would appear at latitudes 25–35°N. The temperate desert (TD) in the western China would become Tibetan high-cold plateau (THP), SEBF, WDBF and temperate steppe (TS), and a large part of THP would be replaced by TRF, TDE, SEBF, TS and TTW. The relative area (distribution area/total terrestrial area) of CMC, TRF, TDE and TTW zone would increase about 3%, 21%, 3% and 6%, respectively. However, the relative area of SEBF, TS, TD and THP would decrease about 5%, 3%, 19% and 4%, respectively. In all, the relative area of forests (CCF, CMC, WDBF, SEBF, TRF) would increase about 15%, but the relative area of desert (TD, SD, TDE, and TTW) and THP would decrease about 9% and 4%, respectively. Therefore, responses of different life zones in China to climate change would be dramatic, and nationwide corridors should be considered for the conservation of migrating species under climate change.

An integrative classification of vegetation in China based on NOAA AVHRR and vegetation-climate indices of the Holdridge life zone

We developed a method for integrated analysis of multi-source data for vegetation classification at the continental scale, and applied it to China. Multi-temporal 1 km NOAA Advanced Very High Resolution Radiometer (AVHRR) Holdridge's life zone system and its vegetation-climate classification indices such as bio-temperature (BT), potential evapotranspiration rate (PER) and precipitation ( P ) correspond better with undisturbed vegetation types all over the world. We generated 1 km images of BT, PER and P using the quantitative model of Holdridge's life zone system with climate data of China. They were processed with principal component analysis (PCA) to produce an ancillary image. This image and 12 monthly images of maximum Normalized Difference Vegetation Index (NDVI) values at 1 km resolution were input into an ISODATA clustering algorithm to carry out a vegetation classification. As a result, 47 information classes were obtained. Seasonal NDVI parameters derived through time series analysis (TSA) of the NDVI temporal profile and a set of quantitative vegetation-climate parameters of Holdrige's life zone model were synthetically utilized to label information classes. In this method, climate, terrain and spectral data were integrated; separability between vegetation types and classification accuracy were improved. A total of 47 land cover classes were obtained. Validation data collected in the field using GPS indicated that an overall classification accuracy of 71.4% was reached, an 8.1% improvement to the map derived only from multi-temporal NDVI images. To compare our results with the International Geosphere-Biosphere Programme (IGBP) DISCover land cover dataset, we aggregated our land cover classes according to the IGBP classification system. The overall classification accuracy for the aggregated vegetation map from our classification results improved IGBP land cover map from 75.5% to 86.3%.

The Holdridge life zones of the conterminous United States in relation to ecosystem mapping

Summary Aim Our main goals were to develop a map of the life zones for the conterminous United States, based on the Holdridge Life Zone system, as a tool for ecosystem mapping, and to compare the map of Holdridge life zones with other global vegetation classification and mapping efforts. Location The area of interest is the forty‐eight contiguous states of the United States. Methods We wrote a PERL program for determining life zones from climatic data and linked it to the image processing workbench (IPW). The inputs were annual precipitation (Pann), biotemperature (Tbio), sea‐level biotemperature (T0bio), and the frost line. The spatial resolution chosen for this study (2.5 arc‐minute for classification, 4‐km for mapping) was driven by the availability of current state‐of‐the‐art, accurate and reliable precipitation data. We used the Precipitation‐elevation Regressions on Independent Slopes Model, or PRISM, output for the contiguous United States downloaded from the Internet. The accepted standard data for air temperature surfaces were obtained from the Vegetation/Ecosystem Modelling and Analysis Project (VEMAP). This data set along with station data obtained from the National Climatic Data Center for the US, were used to develop all temperature surfaces at the same resolution as the Pann. Results The US contains thirty‐eight life zones (34% of the world's life zones and 85% of the temperate ones) including one boreal, twelve cool temperate, twenty warm temperate, four subtropical, and one tropical. Seventy‐four percent of the US falls in the ‘basal belt’, 18% is montane, 8% is subalpine, 1% is alpine, and < 0.1% is nival. The US ranges from superarid to superhumid, and the humid province is the largest (45% of the US). The most extensive life zone is the warm temperate moist forest, which covers 23% of the country. We compared the Holdridge life zone map with output from the BIOME model, Bailey's ecoregions, Küchler potential vegetation, and land cover, all aggregated to four cover classes. Despite differences in the goals and methods for all these classification systems, there was a very good to excellent agreement among them for forests but poor for grasslands, shrublands, and nonvegetated lands. Main conclusions We consider the life zone approach to have many strengths for ecosystem mapping because it is based on climatic driving factors of ecosystem processes and recognizes ecophysiological responses of plants; it is hierarchical and allows for the use of other mapping criteria at the association and successional levels of analysis; it can be expanded or contracted without losing functional continuity among levels of ecological complexity; it is a relatively simple system based on few empirical data; and it uses objective mapping criteria.

Diversity and Conservation of Understory Birds in the Tilarán Mountains, Costa Rica

-Using data from 10,726 captures of birds in mist nets, we document the high alpha and beta diversity of the understory avifauna in the Tilaran mountains of north-central Costa Rica. We grouped the capture data from 20 sampling sites into five Holdridge life zones that represent a gradient in elevation and seasonality of precipitation. Despite the limited size of the study area (200 kM2) and the relatively small differences in elevation (700 to 1,700 m), major differences were found among each of the five life zones. We recorded a total of 235 species, with species richness increasing downslope on both the Pacific and Caribbean sides of the range. Rarefaction curves showed that the elevational zone of 650 to 750 m on the Caribbean side (Wet Premontane Transition Forest) was the most diverse per unit of mistnetting effort and that the Lower Montane Rain Forest on the continental divide (1,500 to 1,700 m) was the least diverse. Adjacent life zones had similarity indices ranging from 0.30 to 0.47; beta diversity for the region was 0.45. These measures are indicative of a high species turnover among our samples as delimited by Holdridge's life zone system, suggesting a concordance between the life zone system and the distribution of the region's diverse understory avifauna. Elevational migrants made up similar proportions of the avifauna in all five zones, whereas the diversity of long-distance migrants was inversely related to elevation. The distribution of species of conservation concern did not track the pattern of overall diversity. Our results provide several lessons for land managers and present a strong case for the need to preserve large areas with elevational diversity in mountainous regions of the tropics. Received 22 September 1997, accepted 2 April 1998. ALTHOUGH ORNITHOLOGISTS have long been aware of the rapid turnover of bird species across elevational gradients in the Neotropics, quantitative studies of fine-scale distributional patterns are available for very few geographic regions (Terborgh and Weske 1975). Such studies allow us to examine the faunistic composition of communities in different elevational habitats, turnover in species composition among habitats (or beta diversity, sensu Whittaker 1972), and to evaluate the conservation status and determine area requirements for conserving montane biodiversity. The ongoing and projected crisis status of tropical forest conservation demands that we gather this information as rapidly as possible (Diamond 1985, Stotz et al. 1996). 4Present address: Latin America and Caribbean Division, The Nature Conservancy, 1815 North Lynn Street, Arlington, Virginia 22209, USA. E-mail: byoung@tnc.org 5Present address: Monteverde Conservation League, Apartado 10581-1000, San Jose, Costa Rica. We compiled data from a series of mist-netting projects to produce estimates of bird diversity in the Monteverde reserve complex, a composite of private reserves in the Tilaran mountains of north-central Costa Rica. The reserve complex has a rich history of ornithological investigation over the last 25 years, but few studies have addressed the distribution of species across an elevational gradient (Young and McDonald 1998). Previous distributional studies of birds have focused on individual species or restricted guilds (Feinsinger 1977; Tramer 1979; Tramer and Kemp 1980, 1982; Stiles and Smith 1980). Treatments of the entire Monteverde avifauna are currently restricted to observation check-lists (Stiles 1983, Fogden 1993). Our goal was to use a compilation of capture data to describe and characterize the diversity and distribution of the understory avifauna between 700 and 1,700 m on both slopes and the crest of the Tilaran range. We analyzed the distributions of the entire understory avifauna and a subset that included only threatened spe-

Folivory in the Big Fruit-eating Bat, Artibeus lituratus (Chiroptera: Phyllostomidae) in eastern Brazil

Information about the consumption of leaves by Neotropical bats is scarce and incomplete. Greenhall (1957) mentions leaves of Ficus religiosa in the diet of Artibeuis lituri-atuis, Tuttle (1968) found remains of chewed leaves under the roosting places of Artibeusjamaicensis, and Wilson (1971) found leaves under night feeding roosts of Allicronycteris hirsuta, which he believed had been chewed and swallowed accidentally while the bats fed on insects. Marshall (1985) reviews the occurrence of folivory amongst Old World phytophagous bats (Megachiroptera). In this note, we present the results of a study of folivory in Artibeus lituratus, a common Neotropical bat, whose frugivorous diet also includes insects, pollen and leaves (Gardner 1977). The study was carried out from August 1988 to August 1989 in the park of the Museu de Biologia Mello Leitao in Santa Teresa, Espirito Santo, eastern Brazil (19?50'S, 40?22'W). Following the Holdridge Life Zone System (Holdridge 1967), the region is dominated by Subtropical Lower Montane Moist Forest; the mean annual precipitation is about 1500 mm, with a wet season between October and March, and a mean monthly precipitation below 100 mm from April to September (Jackson 1978). The study area has mainly secondary arboreal vegetation mixed with shrubs and many introduced plants. We mapped all the night resting and feeding roosts of A. lituiratuis in an area of 4 ha. Every 15 days, feeding remains, composed of dry oral pellets, seeds, faeces and partially eaten foods, were collected in nylon nets which were stretched on the grounid under the roosts in the evening and retrieved the following morning. Pellets of leaves and fruit were dried in an oven at 80?C for 24 h, and weighed separately. The night roosts were inspected frequently and only A. lituratus was observed. Voucher specimens of A. litiuratuis were deposited in the Museu de Biologia Mello Leitao (mammal collection, MBML 1686). Throughout the observation period A. lititratuts fed on leaves of at least six

Growth Habits, Host Tree Species, and Density of Hemiepiphytes on Barro Colorado Island, Panama

Hemiepiphytes in a moist lowland forest were studied to ascertain their relative abundance, host specificity, growth habits, and spatial patterning. Ten percent of the trees support hemiepiphytes which translates to a density of 11.1 hemiepiphyte individuals per hectare. Host tree microhabitats, hemiepiphyte establishment requirements and the behavior of dispersal agents may influence spatial patterning and host specificity. Two classes of hemiepiphytes are recognized: strangling hemiepiphytes which can become free-standing, and permanent hemiepiphytes which cannot. HEMIEPIPHYTES ARE PLANTS THAT GERMINATE ON BRANCHES or trunks of trees and with age send roots to the ground. Though not parasitic, they are dependent on host trees for establishment and support. Some species eventually form extensive coalescing root systems that are capable of self-support. Although these plants are conspicuous components of both lowland and montane forests throughout the tropics (Richards 1952, Dobzhansky & Murca-Pires, 1954), little is known about their density, spatial patterning, or host specificity. To date, only two brief descriptive studies on host specificity of hemiepiphytes exist (Guy 1977, Troth 1979). This paper attempts to answer the following questions: 1) what is the relative abundance of woody hemiepiphytes in a particular moist lowland tropical forest? 2) do hemiepiphytes preferentially grow on different parts of their host trees or on different species of host trees, which have particular morphological characteristics or dispersal mechanisms? 3) do hemiepiphytes which become freestanding differ in habit from those that do not? STUDY AREA AND METHODS Field work was conducted during February and March, 1980, on Barro Colorado Island (BCI), a 15 km2 biological preserve located in Gatun Lake, Republic of Panama, Central America. In the Holdridge Life Zone System (Holdridge et al. 1971), the forest is classified as a tropical moist forest. Mean annual rainfall is approximately 2600 mm with a sharp dry season, usually from mid-December to May, during which the total rainfall is only 18-26 cm (Croat 1978). Due to past disturbances, the forest of Barro Colorado Island is composed of two areas of different ages. The younger forest is between 50 and 80 years old, while the older is at least twice that age (Knight 1975). Further description of the vegetation and climate of BCI is provided in Croat (1978) and Foster and Brokaw (1982). In this study two different sampling regimes were used. At the center of the island in the old forest plots 150 contiguous quadrats (each 20 x 20 m) totalling six hectares were used to answer questions concerning hemiepiphyte abundance and host preferences. Additionally, all hemiepiphytes on an eight meter wide path along both sides of the 37 km trail system on the island were sampled. In analyzing for differences in growth habit and spatial patterning among the various hemiepiphyte species, the two samples were pooled. The present study focused on 20 species of woody hemiepiphytes: Coussapoa magnifolia Trec., C. panamensis Pitt., Ficus bullenei I. M. Johnston, F. citriifolia P. Mill., F. colubrinae Standl., F. costaricana (Liebm.) Miq., F. dugandii Standl., F. nymphizfolia P. Mill., F. obtusifolia HBK, F. paraensis (Miq.) Miq., F. perforata L., F. pertusa L., F. popenoei Standl., F. trigonata L., Clusia odorata Seem., Havetiopsis flexilis Spruce ex Planch. and Tr., Topobea praecox Gleason, Cosmibuena skinneri (Oerst.) Hemsl., Oreopanax capitatus (Jacq.) Decne. and Planch., and Souroubea sympetala. All individuals greater than 25 cm in height were examined from the ground with binoculars (7 x 35). Hemiepiphytic species in the Araceae and Cyclanthaceae were excluded from this survey because they are not woody and because they often lose connection with the ground. Data collected for each hemiepiphyte individual induded species of the host tree, position on host tree, DBH of each individual root, and estimate of the percent of the host canopy shaded by the hemiepiphyte. To determine possible host preferences, the most common tree species were censused within the old forest plots: Hura crepitans L. (Euphorbiaceae), Quararibea asterolepis Pitt. (Bombacaceae), Apeiba membranacea Benth. (Tiliaceae), Platypodium elegans J. Vogel (Leguminosae), and Trichilia cipo (Adr. Juss.) C.DC (Meliaceae). Among these species there is a range of morphologies, from smooth to I Received 24 May 1984, revision accepted 11 October 1984. 22 BIOTROPICA 18(1): 22-27 1986 This content downloaded from 157.55.39.127 on Mon, 27 Jun 2016 07:16:33 UTC All use subject to http://about.jstor.org/terms TABLE 1. Relative abundance and density of hemiepiphyte species on BC!. Mean no. of No. of % of total individuals/ Capable of Species individuals individualsa hectareb independence

The Storage and Production of Organic Matter in Tropical Forests and Their Role in the Global Carbon Cycle

To investigate the storage relationships between and production of organic matter in tropical forests and climate, data on forest biomass, soil organic matter, litter storage, primary production, and litterfall were surveyed from the literature and organized using the Holdridge Life Zone system of classification. Ordinary least squares regressions were applied to all the data sets using the ratio of temperature to precipitation (T/P) as an index to climate and the independent variable. Total forest biomass (40-538 t/ha) gave a significant inverted U-shaped relationship with T/P, with peak values in the tropical moist forest life zone and lower ones in wetter and drier forest life zones. Soil carbon content (24-599 t C/ ha) decreased exponentially and significantly with increasing T/P (i.e., from wet to dry forest life zones). No significant relationship was found between litter storage and T/P. Gross primary production (19-120 t/ha yr) decreased curvilinearly and significantly with increasing T/P. Neither net primary production (11-21 t/ha yr) nor wood production (1-11 t/ha yr) were related to T/P. The ratio of leaf litter production to net primary production (0.25-0.65) was inversely related to T/P, suggesting different strategies of allocation of the net primary production in different life zones. The relationship between total litterfall (1.0-15.3 t/ha yr, excluding large wood) and T/P was significant and its shape similar to that obtained for biomass versus T/P; litterfall was highest in tropical moist forest life zones and lower in wetter or drier ones. The linear relationship between biomass and litterfall suggested that the turnover time of biomass in mature tropical forests is similar for all life zones, and is of the order of 34 yr. To determine the role of tropical forests in the global carbon cycle, literature estimates of areas of tropical forests were placed into six life zone groupings. The total tropical and subtropical basal and altitudinal forest area of 1838 million ha was comprised of 42 percent dry forest, 33 percent moist forest, and 25 percent wet and rain forest life zone groups. Organic-matter storage data were also combined into the six life zone groups and the means for each group calculated. The product of forest areas in the six groups and the mean organic matter per unit area in the groups yielded a total storage of 787 billion t organic matter, with vegetation accounting for 58, soils 41, and litter 1 percent. About half of the total storage was located in the tropical basal wet, moist, and dry forest life zone groups. Litterfall data were treated in the same way as organic-matter storage, resulting in a total litter production in tropical forests of 12.3 billion t organic matter/yr. Most litter was produced in the tropical basal moist forest group (30%) and least in the tropical basal dry forest group (10%). Turnover time of litter in tropical forests was less than 1 yr. Lowest turnover times were in very wet (1 yr) and in dry (0.9-1.9 yr) life zone groups. Tropical forests play an important role in the global carbon cycle because they store 46 percent of the world's living terrestrial carbon pool and 11 percent of the world's soil carbon pool.

Preliminary Report on the Flora Project of La Selva Field Station, Costa Rica

Finca La Selva is an intensively studied biological field station with a poorly known flora. Presently we can account for about 1,500 species of vascular plants but the flora may contain as many as 2,000. Although collecting has been nearly continuous since the beginning of the project in the summer of 1979, we are still finding novelties. Experience at La Selva has driven home the fact that certain genera of both bulky and inaccessible plants have been habitually ignored by botanical collectors in the tropics. The wet Caribbean lowlands of Central America have themselves been relatively inaccessible and ignored. General collecting throughout the region is urgently needed. HISTORY Finca La Selva is a 730 hectare4 biological field station owned and operated by the Organization for Tropical Studies (OTS), which is a consortium of North and Central American universities. The station is located near the confluence of the Puerto Viejo and Sarapiqui rivers in the province of Heredia in the Caribbean lowlands of northeastern Costa Rica. The property encompasses about 650 hectares of primary forest in addition to 80 hectares of disturbed land, including old pasture, abandoned cacao and pejibaye (peach palm) plantations, 25-year-old successional woods, and regularly maintained one- through five-year-old successional plots. In the Holdridge Life Zone system, the vegetation is classified as Tropical Premontane Wet Forest (Holdridge et al., 1971). The average annual rainfall is about 3,900 mm. The elevation varies from 100 m along the Rio Puerto Viejo on the north edge of the property to 220 m in the ridge-dissected southern section (Petriceks, 1956). Thus, the altitudinal range from one end of the property to the other, a distance of about 3.4 km, exceeds that from the Caribbean coast to the La Selva field station, a distance of about 55 km. For the last 12 years the station has been the annual site of as many as three OTS courses in tropical ecology as well as a number of courses offered by other institutions. The site has served almost continuously for the last 25 years as base for many researchers and has been particularly attractive to plant ecologists. A bibliography of published papers based on work done at La Selva contained about 200 entries by fall of 1981. Nevertheless, until recently fewer than half the species of vascular plants now known to occur at the station had been even tentatively identified or otherwise accounted for. The need for a means to identify plants at La Selva has been ever-present. Standley's Flora of Costa Rica (1937-1938) is much out of date and provides only