Moist Forest Life Zones Research Articles

Myxomycetes associated with three different types of Neotropical urban landscapes

Urban ecology is a research field gaining momentum due to contextual pressures to study macroecological effects on biodiversity. Herein, we evaluated the occurrence of myxomycetes in three urban Neotropical environments representing different levels of conurbation within different life zones. We used the moist chamber technique set up with ground litter collected by public roads for such evaluation. Results showed that 79% of the 420 moist chambers yielded myxomycetes and the same number of samples generated 570 records. The highest number of records and species were found in the cornurbated widespread city of the premontane moist forest life zone; and fewer records and species were recorded in the two non-conurbated compact cities. The lowest number of records was associated with the lowland dry forest life zone, whereas the lowest number of species was recorded in the desertic context. In general, more records and more species were observed in the outer zones relative to the urban centre but no significant differences were observed in either case. It is unlikely that the life zone characteristics could have primarily determined the results and highly likely played a secondary role. Also, previous geographical analyses in cities have reported no differences in myxomycete abundance or species richness in relation to the central parts of the urban landscape. The results presented herein support the latter idea, but also suggest that the presence of inter-conurbated green spaces and availability of substrates might play a role in the occurrence of sporocarps of myxomycetes in urban environments.

Preliminary Evaluation of Butterfly Diversity and Rural Agriculture in Montane Costa Rica

Agriculture continues to expand in the tropics, capturing a subset of original biodiversity. Here, butterfly diversity was sampled in four land uses resulting from montane Neotropical agriculture: a forest fragment, a coffee plantation, a banana grove, and a cattle pasture. Butterflies were sampled in both traps baited with rotting fruit and visual transects during the dry season in the tropical premontane moist forest life zone near Monteverde, Costa Rica. The samples were dominated by Cissia spp., overshadowing the diversity and evenness, therefore statistical analyses were run with and without the species. Diversity was highest in the coffee, followed by the forest, then pasture, and banana. Excluding Cissia spp., diversity increased in all sites but remained highest in the coffee, then banana grove, followed by the forest fragment, with the pasture the least diverse. Coffee displayed the highest diversity presumably because it had the highest structural diversity that still allowed abundant light. The pasture may have the lowest diversity because of low structural diversity and high winds. Forest-dwelling butterfly species were less common as habitats lost structural diversity, indicating that while highest local diversity can occur with agriculture, regional species diversity may suffer.

Contribution of Dead Wood to Biomass and Carbon Stocks in the Caribbean: St. John, U.S. Virgin Islands

ABSTRACTDead wood is a substantial carbon stock in terrestrial forest ecosystems and hence a critical component of global carbon cycles. Given the limited amounts of dead wood biomass and carbon stock information for Caribbean forests, our objectives were to: (1) describe the relative contribution of down woody materials (DWM) to carbon stocks on the island of St. John; (2) compare these contributions among differing stand characteristics in subtropical moist and dry forests; and (3) compare down woody material carbon stocks on St. John to those observed in other tropical and temperate forests. Our results indicate that dead wood and litter comprise an average of 20 percent of total carbon stocks on St. John in both moist and dry forest life zones. Island‐wide, dead wood biomass on the ground ranged from 4.55 to 28.11 Mg/ha. Coarse woody material biomass and carbon content were higher in moist forests than in dry forests. No other down woody material components differed between life zones or among vegetation categories (P > 0.05). Live tree density was positively correlated with fine woody material and litter in the moist forest life zone (R= 0.57 and 0.84, respectively) and snag basal area was positively correlated with total down woody material amounts (R= 0.50) in dry forest. Our study indicates that DWM are important contributors to the total biomass and, therefore, carbon budgets in subtropical systems, and that contributions of DWM on St. John appear to be comparable to values given for similar dry forest systems.

Can we manage tropical landscapes? – an answer from the Caribbean perspective

Humans have used Caribbean island landscapes for millennia. Theconversion of wild lands to built-up lands or to agricultural lands in thesetropical countries follows predictable patterns. Conversion of moist forestlifezones and fertile flatlands is faster than conversion of wet and rain forestlife zones and low fertility steep lands. In Puerto Rico, these trends areleading to increased built-up areas, environmental surprises, and increaseddependence on external subsidies. Changes over the past 50 yr alsoinclude a reversal in deforestation and increase in forest patch size in spiteof increasing human population density. Present forests have different speciescomposition than the original ones but are indistinguishable in physiognomy andbasic function. The reversal of deforestation and forest fragmentation trends,if accompanied by an understanding of the forces that cause the reversal, canresult in the development of tools for landscape management. Tropical landscapemanagement requires understanding and application of natural resiliencemechanisms of ecosystems, greater use of ecological engineering approaches toinfrastructure development, enforcement of zoning laws, enlightened economicdevelopment policies, and an understanding and agreement of a conservationvision among all sectors of society. Mixing species in new combinations to formnew ecosystems is a necessary step in the development of future landscapes.“Landscapes have always changed over time, but we sense,somewhat uneasily, that the processes now at work are more powerfully focusedand possibly irreversible.”“Our present assumption is that generally tropical lands aremuch more sensitive and less resilient than those in the temperatezones.”“...the long-term world trend in land uses is a cascadingloss in capacity (i.e., degradation) in every broad category of landuse.” J.F. Richards 1990, p 176 and 177.

Deforestation in Costa Rica: A Quantitative Analysis Using Remote Sensing Imagery1

Accurate estimates of forest cover and forest fragmentation are critical for developing countries such as Costa Rica, which holds four to five percent of the world's plant and bird species. We estimated forest cover for Costa Rica using Landsat 5 Thematic Mapper satellite scenes acquired between 1986 and 1991. In 1991, 29 percent (ca 14,000 km2) of the land cover of Costa Rica was closed forest cover; of that forested area, ca 30 percent is protected by national conservation policies. Forest loss in a study area representing ca 50 percent of Costa Rica's territory during a five-year period (1986–1991) was 2250 km2, and the estimated deforestation rate was ca 450 km2/yr, or ca 4.2 percent/yr, of remaining forest cover. Forests are almost completely eliminated from the Tropical Moist Forest and Premontane Moist Forest life zones, and the level of fragmentation of remaining forests may be more advanced than previously thought.

Phanerochaete flava in Puerto Rico

Phanerochaete flava is a conspicuous, bright yellow, resupinate, wood-inhabiting basidiomycete encountered in the subtropical wet and subtropical moist forest life zones in Puerto Rico. Characterized by abundant, white to yellow hyphal cords with numerous hyaline crystals, this species appears to be involved in the immobilization of nutrients following disturbances, such as hurricanes and logging, that leave woody debris on the forest floor. Basidiomata are redescribed and illustrated. In addition, Peniophora subiculosa is placed in synonymy under P. flava, and a combination, Phanerochaete exigua, is proposed.

Forest Recovery in Abandoned Cattle Pastures Along an Elevational Gradient in Northeastern Puerto Rico

A major cause of tropical deforestation has been the conversion of lowland forest into pastures for cattle grazing. We studied forest structure and species composition following abandonment of cattle pastures in 23 abandoned pastures 9.5-60 yr old and seven forested sites > 60 yr old. Sites were chosen along an elevational gradient from 10-450 m and represented subtropical wet and moist forest life zones. Age since abandonment was the best predictor of stand characteristics. Woody plant density, basal area, species number, and diversity were low 10 yr after abandonment, but increased rapidly after 10 to 15 yr post-abandonment. Although distance to nearest seed source and hurricane exposure are factors that could affect forest recovery, there was little variation among sites and no effects were detected. Elevation and age were significant determinants of species composition. At higher elevations (> 100 m), the shrub Miconia prasina (Melastomataceae) was the dominant pioneer species, but in the low elevation, a larger group of shrubs and small trees colonized abandoned pastures. At higher elevations, the species composition of recovering sites did not include many mature forest species. After 40 yr of recovery, secondary forest stands cannot be distinguished from undisturbed sites in terms of density, basal area, species number, or diversity, but it appears that it will require centuries for these sites to return to a species composition similar to undisturbed forests.

Tree Mortality in Mature Lowland Tropical Moist and Tropical Lower Montane Moist Forests of Venezuela

We examined patterns of mortality from long-term (up to 25 yr) forest inventory data collected from 17 0.25-ha plots representing mature tropical lowland moist forest and tropical lower montane moist forest life zones in Venezuela. Annual mortality rates varied greatly among plots and differed when mortality was calculated on a frequency basis (% stems dying annually) versus a biomass (% total aboveground biomass dying annually) basis. Mortality rates ranged from 0.5 to 3.3 percent (stems) and 0. 1 to 3.9 percent (biomass). Annual mortality rate of stems versus mortality rate of biomass differed by as much as 20 percent within a plot; greater mortality rate of biomass on a yearly basis was attributable to the death of large trees. Annual percent mortality was independent of life zone, diameter class within life zone, and crown class. The majority of trees died standing (64%) followed by fallen (17%), snapped (11%), and other unknown causes (11%). Estimates of the mean half-life of all plots were 36.9 and 42.5 yr based on stems and biomass, respectively, in the tropical moist forest, and 39.3 and 36.3 yr, respectively, in the tropical lower montane moist forest. Large diameter classes had the longest half-lives. Similarity in stem and biomass based half-lives within a life zone suggests that although there is great variability at the individual plot scale, stems and biomass yield similar estimates of mortality at the larger life zone scale.

Observations on the nesting biology of three Brazilian centridine bees:Melanocentris dorsata(Lepeletier 1841),Ptilotopus sponsa(Smith 1854) andEpicharitides obscura(Friese 1899) (Hymenoptera Anthophoridae)

Nests of three neotropical species of centridine bees: Melanocentris dorsata (Lepeletier 1841), Ptilotopus sponsa (Smith 1854) and Epicharitides obscura (Friese 1899) were studied. Information about M. dorsata was obtained from a relatively large aggregation of nests found in a suburb of the city of Curitiba (low montane subtropical moist forest life zone), Parana State (South Brazil), while the data about P. sponsa were gathered from a brief observation of a single nest constructed in an arboreal nest of a termite (possibly a Microcerotermes species) in Porto Nacional (premontane tropical dry forest), Goias State (Central Brazil). Information about E. obscura was also obtained from the examination of a single nest in an initial stage of construction found on flat ground in the forest in Alexandra, Paranagua (premontane subtropical wet forest), Parana State. Information concerning nesting sites and nest structure is presented. For Ptilotopus sponsa there is a relatively extensive paper written by PICKEL (...

Soil Organic Matter in Secondary Forests of Puerto Rico

Soil organic matter content and loose litter were studied in secondary forests of the subtropical moistand wet-forest life zones of Puerto Rico to observe patterns due to life zone (climate), type of forest cover, soil group, and topography. Soil organic matter content in the top 23 cm ranged from 8.99 kg/m) in the moist-forest life zone to 7.30 kg/m' in the wet-forest life zone, a highly significant difference. Greater amounts of soil organic matter were found under higher timber volumes, but the trend was less pronounced in the wet forest. Significant interactions with life zone were found for organic matter among soil groups (deep volcanic, shallow volcanic, granitic, and limestone) and among forest classes (young secondary, late secondary, abandoned coffee, and active coffee shade). In secondary forests on granitic soils, highly significant differences of 12.98 and 7.32 kg/m2 of organic matter were found in wet and moist forests, respectively. Moreover, highly significant differences were observed by landform and slope in active coffee shade in wet forests, with the lowest values on convex land forms and slopes >45 percent. Mean loose litter storages in moist and wet forests were not significantly different, nor was there a significant interaction with life zone. Significant differences, however, were detected by timber volume class, soil group, and forest class. Within these highly disturbed wet and moist forests, greater timber volumes tended to be associated with greater loose litter accumulation. AFTER DISCOVERY OF THE ISLAND, the forests of Puerto Rico were cut for timber, cropland, and fuelwood, and by the mid1940s, undisturbed forests accounted for < 1 percent of the land area. Loss of soil organic matter and exposure of subsoils occurred under the widespread practice of slash and burn agriculture (Smith et al. 195 1). In the late 1940s, industrialization and the accompanying rural-tourban migration left much abandoned cropland and pasture in the mountainous interior. Today, a little over 30 percent of the island is covered by forest, much of it on these abandoned sites. Organic matter influences the physical and chemical properties of soil, commonly accounting for much of the cation-exchange capacity. It also influences the stability of soil aggregates, provides sustenance for soil microorganisms, and is a critical factor in soil fertility (Buckman & Brady 1960). In undisturbed conditions, soil organic matter in moistand wet-forest life zones (that is, with the temperature-to-precipitation ratio approaching unity) is roughly 40 kg/m2 (Brown & Lugo 1982). Clearing for agriculture leads to a decline in soil organic carbon, particularly in soils developed on highly weathered parent I Received 22 October 1984, revision accepted 15 October 1985. ma erials (Allen 1985). Although forest clearing continues at a rapid pace (Sommer 1976; Lanley & Clement 1979) and nearly 1.1 million km2 in the Caribbean, Central, and South America have been classified as forest fallow (Lanley & Gillis 1980), the dynamics of organic matter recovery in tropical soils have not been well documented on a regional basis. The initiation of a secondary forest inventory provided a unique opportunity to sample soils throughout the central part of Puerto Rico to relate loose litter and soil organic matter content to climate, vegetation cover, soil type, and topography. This information is needed for comparison with undisturbed soils under natural cover and to provide insights on soil organic matter dynamics after abandonment of farming in tropical regions.

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.