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PubMed2003

Biodiversity meets the atmosphere: a global view of forest canopies.

The forest canopy is the functional interface between 90% of Earth's terrestrial biomass and the atmosphere. Multidisciplinary research in the canopy has expanded concepts of global species richness, physiological processes, and the provision of ecosystem services. Trees respond in a species-specific manner to elevated carbon dioxide levels, while climate change threatens plant-animal interactions in the canopy and will likely alter the production of biogenic aerosols that affect cloud formation and atmospheric chemistry.

Animals↗

PubMed1983

Use of the forest canopy by the agile gibbon.

Brachiation was the main form of locomotion and took place along branches and boughs in the upper canopy. The posture during feeding depended on the substrate, with the gibbons sitting on branches but hanging in twigs. During foraging the gibbons hung more, even on branches, but as only short stops were made this is probably to increase mobility. Feeding on fruit took place mainly in the middle canopy on small trees; feeding on leaves and foraging occurred evenly throughout the middle and upper canopies. Gibbons are light mobile animals with a rapid and direct form of locomotion that enables them to exploit dispersed food sources and to defend a large territory.

Animals↗

PubMedDate not supplied

Measurement reliability and reactivity using repeated measurements of resting energy expenditure with a face mask, mouthpiece, and ventilated canopy.

This investigation evaluated the measurement reliability and reactivity of repeated measurements of resting energy expenditure using different methods of data collection. Thirty subjects were randomly assigned to either face mask, mouthpiece/nose clip, or ventilated canopy collection systems for 45 min a day over 3 days. Results indicated that there were no significant differences among data collection systems nor were there any differences either within or between systems over time. Across all three days of measurement, the first 5 min of data collection on all systems were reactive compared to the subsequent 40 min of assessment. Analyses indicated that acceptable reliability coefficients were obtained after 20 min of continuous data collection in the ventilated canopy and after 40 min with the face mask after a 5-min acclimation period. The results suggest that, following an acclimation period, a single 20-min assessment of resting energy expenditure in both a face mask and ventilated canopy are stable and reliable.

Adult↗

PubMed2000

Oak canopy effects on the distribution patterns of two annual grasses: the role of competition and soil nutrients.

Within the oak woodlands of California there is often a distinct shift in the botanical composition between the open grassland and the herbaceous understory beneath oak canopy. Botanical sampling at two woodland sites indicated that the annual grass Bromus diandrus was dominant under deciduous blue oak canopy, while a congener, Bromus hordeaceus, was dominant in open grassland. We examined the relative importance of congeneric competition and edaphic factors in creating these differences in species distribution in two separate field experiments that manipulated both congeneric and intraspecific competition, as well as soil type. We used the demographic measure of relative reproductive rate as an index of population growth. In general, demographic performance correctly predicted the distribution of the two annual grasses in the field. Our results indicate that reduced abundance of B. hordeaceus under canopy reflects the negative effects of competition with B. diandrus. In contrast, B. diandrus is little affected by competition from B. hordeaceus. The reduced abundance of B. diandrus in open grassland may result, in part, from its inability to adapt as well as B. hordeaceus to lower nutrient availability in soils of the open grassland.

Journal Article↗

PubMed2000

[Distribution patterns of shoots, flowers and seeds in Ginkgo biloba canopy and their relationships].

The distribution patterns of shoots, flowers and seeds in the canopy of 14 years old engrafted Ginkgo biloba and their relationships were investigated with stratification method. The result shows that long shoots, short shoots, bearing-shoots and flowers uniformly distributed in the central section of canopy. From the top to the bottom, the average age and the divaricating angle of long shoots increase 51.3% of the seeds distributed in 180-320 cm layer from the ground. The number of shoots, flowers and seeds in different canopy layers was closely correlated.

Ginkgo biloba↗

PubMed2003

[Digital modeling of light distribution within the crop canopy in jujube-wheat interplanting system].

On the basis of field observation and with the principles and methods of agricultural meteorology, the daily variations of the shadow width of jujube tree belts and the relative light intensity were analyzed in the jujube-wheat interplanting system, and the characteristics of vertical distribution of the light within the wheat canopy inside and outside the shadow were studied. The sunshine vertical distribution curves in the wheat canopy inside and outside the shadow were simulated by mathematical methods. The results showed that the shadow area of the south-north planting jujube tree belts was fairly wider, but the relative light illuminance was larger in early morning and late afternoon than at about noon. Although the sunshine vertical distribution in the wheat canopy inside and outside the shadow was obviously different, they both observed the decreasing law for Gauss Curve.

Crops, Agricultural↗

PubMed2004

[Characteristics of canopy plant substratum in a low land humid tropical forest (Upper Orinoco, Venezuela)].

By international agreement (Austria-Venezuela) a tower crane was installed near Surumoni river, Upper Orinoco, for canopy research in a tropical rain forest. From the 1.5 ha crane-accessible area of the forest, an experimental plot was selected for assessment of the canopy plants' aerial substrates and to determine their relationship with spatial distribution, presence or absence of vascular plants, and some of the strategies used in their ecological space. In the middle and lower canopy strata myrmecophytic associations appear, where the conformation of the aerial substrates determines the establishment and maintenance of these associations. The high content of nutrients of these aerial substrata represents a reservoir for the forest, where the mirmecophytic activity is determining. A higher fertility of aerial substrates of the ants gardens can be related to a higher number of vascular epiphytes present in these gardens.

Animals↗

PubMed2006

[Quantitative relationships between leaf area index and canopy reflectance spectra of wheat].

Based on the change patterns of leaf area index (LAI) and canopy spectral reflectance of wheat at different growth stages and nitrogen application rates, this paper investigated the relationships of LAI with canopy reflectance and spectral parameters, and brought forward the sensitive spectral parameters and quantitative equation for predicting wheat LAI. The results showed that with increasing nitrogen application rate, wheat LAI and its canopy reflectance at near infrared (760 to approximately 1220 nm) increased, whereas the reflectance at visible band (460 to approximately 710 nm) decreased. From jointing to maturity, the LAI and the reflectance of short bands in near infrared increased initially and decreased then, whereas the reflectance of visible light and long bands in near infrared was in adverse, with the lowest value appeared at booting stage. Wheat LAI was negatively correlated with the reflectance of visible light, but positively with that of short bands in near infrared, with the highest correlation coefficient at 810 nm. It was proposed that wheat LAI could be well monitored by vegetation indices RVI (810, 510) and DVI (810, 560). PVI and TSAVI were proved to be the spectral indices in monitoring wheat LAI, and higher accuracy was obtained with combined RVI (810, 510), DVI (810, 560) and PVI.

Ecosystem↗

PubMed1993

Field evaluations in malaise and canopy traps of selected targets as attractants for tabanid species (Diptera: Tabanidae).

Various configurations of an inflated vinyl beach ball covered with black fabric were evaluated in Malaise and canopy (modified Manitoba) traps for possible use as an insecticide-impregnated visual target (T) for Tabanidae. In Malaise traps, T attracted 2x more flies than no T. When inflated with carbon dioxide, T was not significantly different from T filled with air, no matter which type of trap it was in. In canopy traps, 2 or 4 white spots applied to T did not increase its attractiveness to tabanids. When treated with octenol, T was 2-5x more attractive than an untreated T in canopy traps. However, when an octenol treatment was aged for 48 h, it was less effective than a fresh treatment. Overall, the 3 most frequently collected species, in order of abundance, were: Tabanus lineola hinellus, Hybomitra vicina and Chrysops atlanticus. Significantly more T. l. hinellus and H. vicina were collected at T with octenol than at T without octenol. Attempts to detect an insecticidal effect on flies captured in both types of trap that had been baited with Ts treated with permethrin were unsuccessful.

Animals↗

PubMed1998

Canopy computing: using the Web in clinical practice.

The rain forest canopy is a seamless web through which arboreal creatures efficiently move to reach the edible fruits without any attention to the individual trees. Individual health care computer systems are rich with patient data, but rather than a canopy linking all the trees in the forest, the data "fruit" come from a diverse forest of individual computer "trees"-laboratory systems, word processing systems, pharmacy systems, and the like. These different sources of patient information are difficult or impossible to reach by individual physicians, especially from their offices. The World Wide Web and other standardization technology provide physicians and their institutions the tools needed for seamless and secure access to their patients' data and to medical information, when and where they need it. We and others have adopted these tools to combine independent sources of clinical data. Physicians who assist in the purchase of clinical information systems should demand products in their practice settings that are Web enabled, use standard coding systems, and communicate with other computer systems via broadly accepted protocols.

Clinical Medicine↗

PubMed1995

Dust accumulation in the canopy: a potential cause of dental microwear in primates.

Dental microwear researchers consider exogenous grit or dust to be an important cause of microscopic wear on primate teeth. No study to date has examined the accumulation of such abrasives on foods eaten by primates in the forest. This investigation introduces a method to collect dust at various heights in the canopy. Results from dust collection studies conducted at the primate research stations at Ketambe in Indonesia, and Hacienda La Pacifica in Costa Rica indicate that 1) grit collects throughout the canopy in both open country and tropical rain forest environments; and 2) the sizes and concentrations of dust particles accumulated over a fixed period of time differ depending on site location and season of investigation. These results may hold important implications for the interpretation of microwear on primate teeth.

Alouatta↗

PubMed1997

Behavioural and pharmacological characterisation of the canopy stretched attend posture test as a model of anxiety in mice and rats.

The behavioural element, stretched attend posture (SAP), is an important component of the "risk-assessment" repertoire of defensive behaviour in rodents. The present experimental paradigm was devised as a novel and simple method of eliciting high levels of SAP in mice and rats. The SAP test apparatus comprised an elevated black Perspex circular platform. A smaller clear red Perspex circular "Canopy" was supported directly above the platform by a central pillar, thus dividing the platform into an inner, dimly lit covered zone and an outer, brightly lit exposed zone. In both the rat and mouse version of this model, vehicle-treated animals exhibited a marked preference for exploring the covered zone and also exhibited high baseline levels of SAP, particularly at the covered zone boundary whilst they investigated the exposed zone. In the mouse SAP test, the benzodiazepine receptor agonists, diazepam (0.5 mg/kg s.c.) and chlordiazepoxide (2 mg/kg s.c.), and the 5-HT1A receptor agonists, buspirone (1 and 3 mg/kg s.c.), ipsapirone (3 mg/kg s.c.) and 8-OH-DPAT (0.2 mg/kg s.c.), all significantly decreased the frequency of SAP without impairing motor activity. In the rat SAP test, diazepam (0.5 mg/kg s.c.) significantly decreased, whilst the anxiogenic 5-HT2C/1B receptor agonist, mCPP (0.25 and 0.5 mg/kg s.c.), significantly increased, the frequency of SAP. Ipsapirone (3 mg/kg s.c.) induced a non-specific behavioural inhibition. These data suggest that the "Canopy" SAP test is a useful paradigm to investigate risk assessment behaviour in both rats and mice, and may provide a sensitive novel rodent model of anxiety.

8-Hydroxy-2-(di-n-propylamino)tetralin↗

PubMed2007

Soil fungal communities underneath willow canopies on a primary successional glacier forefront: rDNA sequence results can be affected by primer selection and chimeric data.

Soil fungal communities underneath willow canopies that had established on the forefront of a receding glacier were analyzed by cloning the polymerase chain reaction (PCR)-amplified partial small subunit (18S) of the ribosomal (rRNA) genes. Congruence between two sets of fungus-specific primers targeting the same gene region was analyzed by comparisons of inferred neighbor-joining topologies. The importance of chimeric sequences was evaluated by Chimera Check (Ribosomal Database Project) and by data reanalyses after omission of potentially chimeric regions at the 5'- and 3'-ends of the cloned amplicons. Diverse communities of fungi representing Ascomycota, Basidiomycota, Chytridiomycota, and Zygomycota were detected. Ectomycorrhizal fungi comprised a major component in the early plant communities in primary successional ecosystems, as both primer sets frequently detected basidiomycetes (Russulaceae and Thelephoraceae) forming mycorrhizal symbioses. Various ascomycetes (Ophiostomatales, Pezizales, and Sordariales) of uncertain function dominated the clone libraries amplified from the willow canopy soil with one set of primers, whereas the clone libraries of the amplicons generated with the second primer set were dominated by basidiomycetes. Accordingly, primer bias is an important factor in fungal community analyses using DNA extracted from environmental samples. A large proportion (>30%) of the cloned sequences were concluded to be chimeric based on their changing positions in inferred phylogenies after omission of possibly chimeric data. Many chimeric sequences were positioned basal to existing classes of fungi, suggesting that PCR artifacts may cause frequent discovery of new, higher level taxa (order, class) in direct PCR analyses. Longer extension times during the PCR amplification and a smaller number of PCR cycles are necessary precautions to allow collection of reliable environmental sequence data.

Artifacts↗

PubMed2006

Seasonal dynamics of microbial community composition and function in oak canopy and open grassland soils.

Soil microbial communities are closely associated with aboveground plant communities, with multiple potential drivers of this relationship. Plants can affect available soil carbon, temperature, and water content, which each have the potential to affect microbial community composition and function. These same variables change seasonally, and thus plant control on microbial community composition may be modulated or overshadowed by annual climatic patterns. We examined microbial community composition, C cycling processes, and environmental data in California annual grassland soils from beneath oak canopies and in open grassland areas to distinguish factors controlling microbial community composition and function seasonally and in association with the two plant overstory communities. Every 3 months for up to 2 years, we monitored microbial community composition using phospholipid fatty acid (PLFA) analysis, microbial biomass, respiration rates, microbial enzyme activities, and the activity of microbial groups using isotope labeling of PLFA biomarkers (13C-PLFA). Distinct microbial communities were associated with oak canopy soils and open grassland soils and microbial communities displayed seasonal patterns from year to year. The effects of plant species and seasonal climate on microbial community composition were similar in magnitude. In this Mediterranean ecosystem, plant control of microbial community composition was primarily due to effects on soil water content, whereas the changes in microbial community composition seasonally appeared to be due, in large part, to soil temperature. Available soil carbon was not a significant control on microbial community composition. Microbial community composition (PLFA) and 13C-PLFA ordination values were strongly related to intra-annual variability in soil enzyme activities and soil respiration, but microbial biomass was not. In this Mediterranean climate, soil microclimate appeared to be the master variable controlling microbial community composition and function.

Bacteria↗

PubMed1999

A Simple Model for Estimating Mean Monthly Stream Temperatures After Riparian Canopy Removal.

/ The removal of riparian vegetation along small streams affects the thermal regime of the stream and consequently the biota within it. A simple regression model for mean monthly temperature after riparian canopy removal, based on conditions prior to removal, is presented. The model is determined to have an accuracy of +/-2 degrees C 95% of the time over the temperature range 0.7-17 degrees C. The regression also predicts a switching point at 3 degrees C, below which postharvesting temperatures are colder than prior to harvest. The ability to predict postharvest stream temperatures based on preharvest air temperatures is also evaluated. Management implications of thermal effects due to riparian removal are discussed.KEY WORDS: Stream temperature; Temperature model; Prediction; Air temperature; Thermal change; Riparian canopy removalhttp://link.springer-ny.com/link/service/journals/00267/bibs/24n1p77.html

Journal Article↗

PubMed2003

Leaf dynamics of a deciduous forest canopy: no response to elevated CO2.

Leaf area index (LAI) and its seasonal dynamics are key determinants of terrestrial productivity and, therefore, of the response of ecosystems to a rising atmospheric CO(2) concentration. Despite the central importance of LAI, there is very little evidence from which to assess how forest LAI will respond to increasing [CO(2)]. We assessed LAI and related leaf indices of a closed-canopy deciduous forest for 4 years in 25-m-diameter plots that were exposed to ambient or elevated CO(2) (542 ppm) in a free-air CO(2) enrichment (FACE) experiment. LAI of this Liquidambar styraciflua (sweetgum) stand was about 6 and was relatively constant year-to-year, including the 2 years prior to the onset of CO(2) treatment. LAI throughout the 1999-2002 growing seasons was assessed through a combination of data on photosynthetically active radiation (PAR) transmittance, mass of litter collected in traps, and leaf mass per unit area (LMA). There was no effect of [CO(2)] on any expression of leaf area, including peak LAI, average LAI, or leaf area duration. Canopy mass and LMA, however, were significantly increased by CO(2) enrichment. The hypothesized connection between light compensation point (LCP) and LAI was rejected because LCP was reduced by [CO(2)] enrichment only in leaves under full sun, but not in shaded leaves. Data on PAR interception also permitted calculation of absorbed PAR (APAR) and light use efficiency (LUE), which are key parameters connecting satellite assessments of terrestrial productivity with ecosystem models of future productivity. There was no effect of [CO(2)] on APAR, and the observed increase in net primary productivity in elevated [CO(2)] was ascribed to an increase in LUE, which ranged from 1.4 to 2.4 g MJ(-1). The current evidence seems convincing that LAI of non-expanding forest stands will not be different in a future CO(2)-enriched atmosphere and that increases in LUE and productivity in elevated [CO(2)] are driven primarily by functional responses rather than by structural changes. Ecosystem or regional models that incorporate feedbacks on resource use through LAI should not assume that LAI will increase with CO(2) enrichment of the atmosphere.

Adaptation, Physiological↗

PubMed2003

Extensive summer water pulses do not necessarily lead to canopy growth of Great Basin and northern Mojave Desert shrubs.

Plant species and functionally related species groups from arid and semi-arid habitats vary in their capacity to take up summer precipitation, acquire nitrogen quickly after summer precipitation, and subsequently respond with ecophysiological changes (e.g. water and nitrogen relations, gas exchange). For species that respond ecophysiologically, the use of summer precipitation is generally assumed to affect long-term plant growth and thus alter competitive interactions that structure plant communities and determine potential responses to climate change. We assessed ecophysiological and growth responses to large short-term irrigation pulses over one to three growing seasons for several widespread Great Basin and northern Mojave Desert shrub species: Chrysothamnus nauseosus, Sarcobatus vermiculatus, Atriplex confertifolia, and A. parryi. We compared control and watered plants in nine case studies that encompassed adults of all four species, juveniles for three of the species, and two sites for two of the species. In every comparison, plants used summer water pulses to improve plant water status or increase rates of functioning as indicated by other ecophysiological characters. Species and life history stage responses of ecophysiological parameters (leaf N, delta15N, delta13C, gas exchange, sap flow) were consistent with several previous short-term studies. However, use of summer water pulses did not affect canopy growth in eight out of nine comparisons, despite the range of species, growth stages, and site conditions. Summer water pulses affected canopy growth only for C. nauseosus adults. The general lack of growth effects for these species might be due to close proximity of groundwater at these sites, co-limitation by nutrients, or inability to respond due to phenological canalization. An understanding of the connections between short-term ecophysiological responses and growth, for different habitats and species, is critical for determining the significance of summer precipitation for desert community dynamics.

Analysis of Variance↗

PubMed2002

Changes in mass and energy transfer between the canopy and the atmosphere: model development and testing with a free-air CO2 enrichment (FACE) experiment.

The rationale for this study is found in the probable higher temperatures and changes in rainfall patterns that are expected in the future as a result of increasing levels of CO2 in the atmosphere. In particular, higher air temperatures may cause an increase in evapotranspiration demand while a reduction in rainfall could increase the severity and duration of drought in arid and semi-arid regions. Representation of the water transfer scheme includes water uptake by roots and the interaction between evapotranspiration and CO2 enrichment. The predicted response of a spring wheat (Triticum aestivum L. cv. Yecora rojo) canopy in terms of energy exchange processes to elevated atmospheric CO2 level was tested against measurements collected at the FACE (Free Air Enrichment Experiment) site in 1994. Simulated and measured canopy conductances were reduced by about 30% under elevated [CO2] under optimum conditions of water supply. Reductions in latent heat fluxes under elevated instead of ambient [CO2] caused reductions in both simulated and measured seasonal water use of 6% under optimum and 2% under suboptimum irrigation. The soil-plant-atmosphere water transfer scheme proposed here offers several advances in the simulation of land surface interactions. First, the stomatal resistance model minimizes assumptions in existing land surface schemes about the effects of interactions among environmental conditions (radiation, temperature, CO2) upon stomatal behavior. These interactions are resolved in the calculation of CO2 in which processes are already well understood.

Air↗