Protozoa from aboveground and ground soils of a tropical rain forest in Puerto Rico

Decomposition occurs in the aboveground and ground litter and soils of tropical rain forests, but little is known about the protozoa that stimulate bacterial activity and turnover. I examined litter and ground soils, epiphytic bryophyte soils on tree trunks and branches, and adventitious roots of lianas attached to tree trunks, within 2 m above ground in the Luquillo Experimental Forest, within the Caribbean National Forest, Puerto Rico. Amoebae numbered 69,000–170,000, ciliates 1000–25,000, and testate amoebae 58,000–190,000 g⁻¹ dry wt. of litter, but were reduced by 0.25–0.5 of these abundances in the underlying soils. In the aboveground soils, amoebae numbered 64,000–145,000, ciliates 1000–8000, and testate amoebae 84,000–367,000 g⁻¹ dry wt. of soil. Eighty species of ciliates and 104 species of testate amoebae were found. About 50% of the individuals in ciliate and 33% in testate amoebae populations were small r-selected species, illustrating that functional differences between species determine community composition. Although protozoan numbers are best described as “protozoan potential” because many individuals may be dormant, the high moisture content of tropical rain forest litter and soils suggest almost continually connected soil water films (necessary for protozoan transport), and together with the large numbers and biodiversity of protozoa, suggest that a major proportion of these protozoa contribute to the bacterial decomposition channel of organic matter.     

Correlation between earthworms and plant litter decomposition in a tropical wet forest of Puerto Rico

Earthworms are recognized to play an important role in the decomposition of organic materials. To test the use of earthworms as an indicator of plant litter decomposition, we examined the abundance and biomass of earthworms in relation to plant litter decomposition in a tropical wet forest of Puerto Rico. We collected earthworms at 0–0.1 m and 0.1–0.25 m soil depths from upland and riparian sites that represent the natural variation in soils and decomposition rates within the forest. Earthworms were hand-sorted and weighed for both fresh and dry biomass. Earthworms were dominated by the exotic endogeic species Pontoscolex corethrurus Müller; they were more abundant, and had higher biomasses in the upland than in riparian sites of the forest. Plant leaf litter decomposed faster in the upland than riparian sites. We found that earthworm abundance in the upper 0.1 m of the soil profile positively correlated with decomposition rate of plant leaf litter. Ground litter removal had no effect on the abundance or biomass of endogeic earthworms. Our data suggest that earthworms can be used to predict decomposition rates of plant litter in the tropical wet forest, and that the decomposition of aboveground plant litter has little influence on the abundance and biomass of endogeic earthworms.     

Selenium Fertilization of Guinea Grass Pastures in Central Puerto Rico

Abstract

Five levels of selenium (Se) fertilization and a control were tested in a Guinea grass paddock. All treatments followed the same trend: an initial Se concentration increment up to week 6 and then a slow decrease toward initial values or less. No significant differences among treatments or interactions were observed during the 22 weeks of the experiment. The study suggests that soils and forages adequate in Se will not respond to subsequent levels of Se fertilization as Selcote Ultra.     

Interactive effects of native and exotic earthworms on resource use and nutrient mineralization in a tropical wet forest soil of Puerto Rico

Investigation of single or mixed assemblages of native Estherella sp. and exotic Pontoscolex corethrurus from a rain forest in Puerto Rico was undertaken to understand resource use patterns, and linkages with C and N mineralization in a 19-day incubation. Resource use was explored with addition of ¹⁵N-enriched leaf litter and ¹³C-enriched glucose to reconstructed organic and mineral soil horizons. Juvenile Estherella sp. became at least 6.06‰ more enriched in ¹³C than sub-adult Estherella sp. or adult P. corethrurus. Sub-adult Estherella sp. became >3.6‰ enriched in ¹³C over P. corethrurus. '¹⁵N acquired by P. corethrurus was greater by 0.83-1.56‰ in the mixed-species than the single-species assemblages. '¹⁵N of sub-adult Estherella sp. was enriched by 0.73-0.81‰ over juvenile Estherella sp. in the single-species assemblage. Net N immobilization occurred in the organic layer of all ¹⁵N-enriched treatments. Net N mineralization in mineral soil layers was significantly greater in microcosms with P. corethrurus than in those containing only Estherella sp.. Cumulative respiration was greatest in P. corethrurus assemblages, however, assemblages with only Estherella sp. released more ¹³C in respiration. P. corethrurus assimilated different N resources when incubated with, as compared to without, native Estherella sp.. '¹³C and '¹⁵N signatures acquired by assimilation of ¹³C and ¹⁵N differed by species, developmental stage, and competitive interactions. The results showed that alone, exotic P. corethrurus induced higher mineralization rates than native Estherella sp., but that the interaction of exotic and native species impinged on resource use by P. corethrurus, reducing the effect of the exotic species on C and N mineralization. Invasion of exotic P. corethrurus may change the mineralization potentials of C and N and their biogeochemical cycling in soils.     

Nitrogenase activity associated with three tropical grasses growing in undisturbed soil cores

Nitrogenase activity associated with the root system of three tropical grasses Axonopus compressus, Digitaria decumbens var. pangolaand Paspalum notatum was measured by C₂H₂ reduction assay of soil-plant cores. The cores were incubated in perspex chambers in which 10% of the air was replaced with C₂H₂. Gas samples were taken at 7, 24, 31, 48, 55 and 72 h. No lag before onset of C₂H₄ production was evident and good agreement was obtained between replicates. Cumulative C₂H₄ production maintained a linear trend during the 72 h incubation.The largest increase in N₂-ase activity was detected in the A. compressus—gleyed podzolic system while D. decumbens (lateritic podzolic) and P. notatum (sandy yellow podzolic) had smaller activities. Variation between sampling sites in the second year of sampling of the experiment was associated with large variations in soil moisture.N₂ fixation estimated from N₂-ase activity in soil-plant cores was similar to the amount of N accumulated in the above-ground herbage in the field during 12 weeks.Response curves relating N₂-ase activity to soil moisture and soil temperature were established for all species. P. notatum and D. decumbens responded similarly to changes in both soil temperature and soil moisture while A. compressus contrasted sharply to the other two species in its reaction to both.     

Organochlorine pesticides and polychlorinated biphenyls in sediment and fish from Wetlands in the north central United States

Sediment samples collected in 1980-1982 from riverine and pothole wetlands at 17 locations in the north central United States were analyzed for organochlorine pesticides, certain of their metabolites, and polychlorinated biphenyls (PCBs). Concentrations were above minimum detection levels (5 ng/g of organochlorines and 20 ng/g of PCBs) in less than 4% of the samples taken. Fish samples taken at 9 of these 17 locations, and analyzed for the same compounds, showed a higher frequency of detectable contaminants. The most common compound found in fish was DDE, which was found in 51% of the samples at levels up to 512 ng/g. alpha-BHC was present at concentrations of 5 to 27 ng/g in 36% of the fish samples, and DDD was found at levels of 5 to 60 ng/g in 14%. Four other compounds, DDT, dieldrin, PCB, and trans-nonachlor, were detected in fish at relatively low concentrations in less than 10% of the samples. This survey, thus, indicated little contamination by organochlorine pesticides or PCBs in the wetland habitats of this region.     

Concentrations of benzo(a)pyrene in the sediments of six western United States lakes

Sections of sediment cores from 6 western United States lakes were analyzed for benzo(a)pyrene by thin layer chromatography (TLC) fluorescence and gas chromatography-mass spectrometry (GCMS). The highest concentration, 305 μg kg^?1 dry weight, was found in a Los Angeles reservoir. The concentrations of benzo(a)pyrene in the sediment from all the lakes were found to be lower than expected when compared to other values reported in the literature.     

In Vitro digestibility,crude protein content,and mineral concentrations of cynodon,brachiarin, and digitaria accessions in a humid tropical region of Puerto Rico

Abstract

The in vitro organic matter digestibility (IVOMD), crude protein (CP) content, and mineral composition of 11 grasses were compared between seasons in Puerto Rico and evaluated in relation to grazing ruminant requirements. Digitaria eriantha was the highest in IVOMD for both seasons, being higher (P<0.05) than 6 of 10 forages in the long‐day season and 4 of 10 in the shortday season. No differences (P>0.05) in CP content were observed among accessions at both seasons. Mean macroelement content of the accessions was generally adequate in relation to grazing ruminant requirements with the exception of sodium (Na) and magnesium (Mg). Forage microelement concentrations of cobalt (Co), copper (Cu), and zinc (Zn) were generally under the grazing ruminant requirements for the accessions evaluated during both seasons. Iron (Fe) and manganese (Mn) content were high in relation to requirements, especially during the short‐day season. Molybdenum (Mo) was not in excess for the accessions evaluated. The Zn concentrations were similar to the results reported from other experiments with higher fertilization levels. The selenium (Se) concentrations presented an apparent seasonal variation higher in the short‐day season, which is similar to other experiments with high fertilization levels.     

A comparison of carotenoid content and total antioxidant activity in catsup from several commercial sources in the United States

Samples of catsup from 13 commercial sources, representing at least 10 U.S. manufacturers, were analyzed for carotenoid content, antioxidant activity, and percentage solids. The solids content of these catsup brand samples varied from 26.31 to 38.06% solids. The lycopene content ranged from 59.42 to 183.36 microg, and total carotenoids were as high as 216.6 microg/g fresh weight, respectively. In addition, both hydrophilic and lipophilic antioxidant activities were measured using the Trolox equivalent antioxidant capacity (TEAC) assay. These measurements of samples of the various catsup brands ranged from 176.5 to 356.8 total TEAC units.     

Effect of several production factors on two varieties of rapeseed in the central United States

Two varieties of winter rapeseed (Brassica napus) (Cobra and Liborius) were planted at Brownstown, IL to evaluate the effect of planting date, nitrogen (N) rate, N application timing, and tillage on grain yield and oil content of the grain, grain moisture, plant lodging, winter survival, and plant N content. Results indicated that planting rapeseed approximately one to two weeks prior to winter wheat in this region is preferable to planting earlier. Grain yield showed a significant linear increase with delayed planting date from 25 August to 24 September. Grain yield also increased quadratically with increasing N rate (with an optimum of about 250 kg N/ha) and increased (0.15 Mg/ha) due to splitting the N fertilizer into two even applications. An increase in grain yield was accompanied by an increase in grain moisture with Liborius (late maturing) having significantly greater grain moisture than Cobra. Winter survival increased linearly with delayed planting date but, was accompanied by a significant quadratic increase in plant lodging. Chisel, as compared to disk tillage, increased plant lodging slightly, but decreased winter survival slightly. Neither delayed planting, N rate, nor splitting of spring N affected oil content. Liborius produced significantly more oil than did Cobra.     

Inter-regional comparison of patterns and trends in surface water acidification across the United States

Temporal trends in acid-base chemistry are reported for surface waters in 6 regions of the United States. The lakes and streams are low ANC, dilute systems, selected to represent acid-sensitive aquatic resources in the 6 regions. The predominant trends observed were decreases in lake and stream SO₄ ^2? concentrations in sites east of the Mississippi River, and increases in NO₃ ^? in the Adirondack lake and Catskill stream sites (both located in eastern New York State). Correlations of trend results from all sites with other factors indicated that trends in precipitation volume were highly correlated with the observed trend patterns. From the surface water trend results, three distinct clusters were identified that corresponded to three trend patterns: ‘dilution,’ ‘recovery,’ and ‘acidification.’ These were distributed across the LTM regions, with no particular geographic patterns.     

Relations between El Nino/Southern Oscillation anomalies and wildland fire activity in the United States

The 1982–1983 El Nino resulted in climatic anomalies on a global scale, including record high wildland fire activity in Indonesia and record low activity in the United States. This paper describes the El Nino/Southern Oscillation phenomena and possible teleconnections to United States weather. Because precursors of an El Nino may be evident several months before the onset of an event, the phenomena has potential for long-range fire activity predictions.Using 53 years of data, we tested the hypothesis that El Nino events affect annual fire occurrence and area burned in the United States. We found a statistically significant relation between El Nino events and decreased fire activity in the South. Results for the North-Central and Eastern states are weak or inconsistent. There is no evidence for any relation with the Pacific Coast or Rocky Mountain states. Despite the coarse, exploratory nature of this study, the results are sufficiently encouraging to warrant more detailed examination.     

Non-symbiotic nitrogen fixation in the rhizospheres of rice,maize and different tropical grasses

Nitrogenase activity estimated in the rhizospheres of rice, maize and different tropical grasses grown under controlled laboratory conditions was shown to depend upon plant species. High nitrogenase activity (2000–6000 nmoles C₂H₄ h^?1 g^?1 dry root) occurred in rice rhizosphere, this activity being only 10 times lower than that of symbiotic systems; in the rhizosphere of many other grasses grown in a similar way nitrogenase activity was as low as 10 nmoles C₂H₄ h^?1 g^?1 dry root. The influence of soil type on nitrogenase activity was impressive; but the exact nature of the factors implicated could not be established. A rather weak flush of nitrogenase activity in the rhizosphere occurred in the early stage of the plant growth; it was probably due to the exudation of compounds from the seed and lasted 2 or 4 days according to the size of the seed. When the plant entered into its intense photosynthetic phase, the nitrogenase activity gradually increased. When the shoots were severed, nitrogenase activity in the rhizosphere ceased. Nitrogenase activity in the rhizosphere responded greatly to light intensity. Extrapolation of these laboratory findings to the field is discussed.     

Towards Excellence in Environmental Education A View from the United States

Within the United States, a nationwide debate has been raging over how to best provide quality education for all learners. Much of this debate, spurred by poor test scores and other measures of achievement, has centered on the development of national, state and local standards and assessments for the core disciplines (e.g., mathematics, science, geography). For the most part, environmental education has been left out of this debate and out of the various standards development initiatives. Whether one agrees philosophically with academic standards or not, these standards are determining what is being taught in the classroom. By 1993, environmental education in the United States found itself in a conundrum. It has always been argued that environmental education should be interdisciplinary, infused throughout the curriculum. However, with the new standards, environmental education was in real danger of becoming marginalized. To address this situation, the North American Association for Environmental Education (NAAEE) initiated the National Project for Excellence in Environmental Education.     

Conservation of Lepidoptera in the United States

The need to conserve United States populations of Lepidoptera has been recognised for a century, but intensive programmes to do so have only recently come into being. The evolution of the butterfly and moth conservation movement in the United States is followed from the earliest instances to the present state of progress. The origin and growth of the Xerces Society as the chief body for terrestrial arthropod conservation in America are described. Currently, ecological research and political action aimed at specific lepidopteran protection issues are under way. Several of these are examined and the most acute needs for further study and action indicated. Habitat alteration emerges dramatically as the chief problem in the decline of butterfly and moth populations. The relative importance of pesticides and overcollecting is discussed and reinforces the conclusion that the habitat is paramount. Introductions of organisms for purposes of conservation likewise receive consideration, showing this strategy to be problematical and subject to careful review prior to its use. The various levels of government as well as private bodies and individuals have distinct roles in insect conservation. Greater public awareness of beneficial insects must precede optimal effectiveness of conservation schemes. The appointment of an official federal insect conservator is announced along with his initial proposal for endangered species listings for certain North American butterflies. The prognosis for a national programme is suggested. Lepidoptera conservation in the United States has become a fully fledged movement with numerous successes and with many difficult problems to face. The situation is viewed with immediate alarm but cautious long-term optimism as well.     

Organochlorine residues in brook trout from remote lakes in the Northeastern United States

Organochlorine residues were analyzed in brook trout (Salvelinus fontinalis) collected from six undisturbed lakes in Maine, New Hampshire and Vermont. The residues (whole body) were compared among age groups of fish and were correlated by regression analyses with water chemistry factors that might be affected by acid precipitation. There were significant differences in the organochlorine content of fish from different lakes but not among age groups of fish within each lake or among all lakes. There were no significant correlations between the water chemistry values measured and organochlorine content of the fish. Inasmuch as no organochlorine pesticides have been used within the lake watersheds, the compounds must have reached these lakes by atmospheric transport.