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PubMed2003

[Seedling establishment of Fagus engleriana, a dominant in mountain deciduous forests].

The survival and growth of Fagus engleriana seedlings in three light levels, and with and without supplying additional fertilizer (F1 and F0, respectively) for each light level were studied. The three light levels were to simulate the light regimes in the understorey, small gaps and clearings (L1, L2 and L3 about 1%, 18% and 100% of full sunlight, respectively). The seedling development in L1 was severely inhibited by low light intensity. Seedling mortality was remarkably higher in L1 than in L2 and L3, and in F1 than in F0. The death of the seedlings seemed to result from attack of fungal pathogens. Although seedling survival and growth were significantly improved as light intensities increased from L1 to L2, seedlings in L3 developed similarly as those in L2. It is suggested that the young seedlings could not tolerate the shade of closed forest canopy, and fertile patches on the forest floor might not improve seedling establishment. Successful regeneration of the species in the forests needs better light conditions such as those in gaps than those under the closed forest canopy, at least during the phase of seedling establishment.

Biomass↗
PubMed2003

[Analysis on factors affecting net primary productivity distribution in Changbai Mountain based on process model for landscape scale].

Based on the data received from remote sensing images, the spatial distribution of annual net primary productivity (NPP) was simulated by the process model (EPPML), and the relationships between annual NPP and environmental conditions were analyzed. The results showed that NPP in 1995 was 0.680 kg C.m-2.yr.-1, mostly ranging from 0.105 to 1.241 kg C.m-2.yr.-1, accounting for 82.1%. The highest NPP (1.084 kg C.m-2.yr.-1) appears in mixed broad-leaved and Korean pine forest. Environmental conditions decide the main trend of the spatial distribution of annual NPP (Carbon) in Changbai Mountain. Soil water content had a negative correlativity with NPP, and the correlation coefficient (R) was -0.65. Therefore, water was sufficient for the growth of plants in Changbai Mountain. NPP was highly correlated with LAI (R = 0.81). When LAI was greater than 4-5 m2.m-2, NPP became saturated. NPP was also highly correlated with canopy transpiration (R = 0.77). The response of NPP on environmental conditions, LAI and canopy transpiration in Betula ermanii and broad-leaved forests were different from those in other vegetation.

Conservation of Natural Resources↗
PubMed2003

[Forest gap characteristic in a coniferous-Picea likiangensis forest in the Yulong Snow Mountain Natural Reserve, Yunnan Province, China].

In this paper, some important parameters related to the gap disturbance regimes in a coniferous-Picea likiangensis forest in the Yulong Snow Mountain Natural Reserve, Yunnan Province were described. The results showed that expanded gaps occupied 42.5%, and canopy gaps occupied 28.8% of the land area in the forest. The frequency of gap disturbance was 35 gaps per hectares. There were 25% of small (gap area < 50 m2), 41% of middle (gap area 50-100 m2), and 34% of large (gap area > 100 m2) forest gaps. The most important manner of gap formation was the breakage at trunk base and its middle, and the secondly important manner was rotten. Gap maker in the forest was more than 80% of Picea likiangensis. The probability of making gaps was the greatest, when the big trees in the canopy layer got DBH 40-50 cm and height 15-25 m. Gaps formed by 1-2 gap makers was of 68.8%, and by 5 gap makers was seldom. The most of gap makers were 6 in a gap of the forest. The density of the seedlings in gap gradually increased with the forest gap from large to small.

Conservation of Natural Resources↗
PubMed2003

[A preliminary study on the chemical properties of precipitation, throughfall, stemflow and surface run-off in major forest types at Dinghushan under acid deposition].

Studies on the chemical properties of precipitation, throughfall, stemflow and surface run-off in major forest types at Dinghushan under acid deposition showed that the pH value of precipitation was about 4.90, and the frequency of acid rain was over 62%. In broad-leaved forest, the pH value of precipitation was lower than that of throughfall, but higher than that of stemflow and especially the surface run-off, indicating that the soil was naturally acidified. In mixed forest, both throughfall and surface run-off had a higher pH value, but stemflow had a lower pH value than precipitation. The throughfall and stemflow were more acidified than precipitation in coniferous pine forest, but the surface run-off had a higher pH value than precipitation. These results suggested that among the three major forest types at Dinghushan, the canopy of broad-leaved forest had the highest buffering ability, whereas for the soil, the coniferous forest had the highest soil buffering capacity. The concentrations of nutrient elements, such as P, K, Ca, Na and Mg in the throughfall, stemflow and surface run-off were higher than those in bulk precipitation in all forests at Dinghushan, some even 10 times higher, indicating that a large amount of nutrients were leached from the canopy. The concentrations of nutrient elements in stemflow were higher than those in throughfall in all forests, and the concentration of nutrient elements in surface water was higher than those in atmospheric rainfall. Coniferous forest had a higher concentration of nutrients in the throughfall and stemflow and a lower nutrient concentration in the surface run-off than other forest types, which implied that nutrient loss was more serious in broad-leaved and mixed forests than in coniferous forests.

Calcium↗
PubMed2004

[Effect of forest litter on microenvironment conditions of forestland].

Litter is a very important component in forest ecosystem. This paper made a systematic review on the previous studies about the effects of litter on forestland microsites. Litter significantly reduced the light on the soil surface of forestlands, and the light transmittance was varied with the type, water content and weight of litter. The spectral composition of the light was dramatically shifted to longer wavelengths after transmitted through forest capony, especially through moist litter leaves, intact forest litter, and even the thinner soil layer, which greatly reduced the R/FR ratio and PPFD (photosynthetic photo flux density) beneath litter and surface soil (2 mm depth), and resulted in a stronginhibitory effect on the germination of photoblastic seeds, and on the growth of seedling and sapling. It was the reason why the appearance of massive numbers of pioneer plants and their successful establishment required relatively large gaps of the forest canopy. Many references concerned the effects of litter on soil nutrient cycling and water and soil conservation. The previous studies indicated that litter could create a moist micro-site above soil, and make soil more moist and fertile. Furthermore, litter could also increase the numbers of arthropods such as Carabidae adults and larvae, crickets, millipedes, spiders, ants and others. An increase in the activity of herbivorous arthropods might produce the negative effects on the establishment of individual seedlings. Although the mechanical barrier of litter was neglected in the paper, litter might act as a mechanical impediment to the emergence of the seedlings of pioneer species with small seeds. The effects of litter on micro-sites were of complexity because it varied greatly with the density, age, structure and species composition of the canopy, sunfleck frequency, presence of gaps, as well as litter thickness, moisture, and species composition, and also with climate and topography factors. The effects of litter were comprehensive, including positive and negative effects on seed germination and seedling growth. Each effect of litter on regeneration was dependent on species physiology, litter physical properties and environmental conditions. Therefore, it should be encouraged to integrate the physical properties (such as changing light, temperature and moisture) of litter with the physiological ecology (including seed, germination and growth natures) of species, and with environment (vegeneration, climate and topography propersities) on the basis of combination of regeneration patterns of litter, understory and gap scales.

Animals↗
PubMed2003

[Structural characterization of a Podocarpus parlatorei and Juglans australis forest in Salta, Argentina].

Stands of Subtropical Montane Cloud Forest were studied in areas under different land use regimes near Los Toldos (NW Argentina). Circular plots were used to calculate density and basal area of trees with dbh > 10 cm; and density of trees with dbh < 10 cm. The stands were classified and grouped as a function of basal area. Five structures were recognized, with different proportions of Juglans australis, Podocarpus parlatorei and shade-tolerant species like Blepharocalyx salicifolius, Allophylus edulis and Myrcianthes sp. Less disturbed area stands had a higher basal area and greater dbh for all species, and shade-tolerant species in the canopy. In the most disturbed area, all canopy species were shade intolerant and regeneration was dominated by shade-tolerant species. The differences in composition, basal area, stem diameter class distribution and regeneration indicate that the structure types corresponded to different stages of the successional process, and the regeneration of the most disturbed areas suggest a tendency towards the composition of mature forest.

Argentina↗
PubMed2004

[Light energy utilization and dissipation in seedlings of three tropical rain forest tree species with different ecological habits].

In this study, the light energy allocations between photochemical reactions and heat dissipation in the seedlings of three tropical rain forest tree species were investigated under three light regimes (100%, 25% and 8% of full sunlight) by using chlorophyll fluorescence technique. These tree species are Anthocephalus chinensis (Rubiacease), a pioneer species, Pometia tomentosa (Sapindaceae), a canopy climax species, and Horsfieldia tetratepala (Myristicaceae), a sub-canopy climax species. Under the same light levels, A. chinensis had a higher maximum photosynthetic rate (Pmax) and maximum electron transport rate (ETRmax) than P. tomentosa and H. tetratepala. From the light response curves of light energy allocations, all test species had a decreased fraction of light energy allocated to photochemical reactions, while the fraction of light energy allocated to heat dissipation was increased with light intensity. The fractions of light energy allocated to photochemical reactions and heat dissipation were negatively correlated with very high significance. Compared to other two species, A. chinensis allocated more light energy to fractions of photochemical reactions, and had weaker and unsaturated heat dissipation. But, when growing under 100% sunlight, this species had less excess light energy to be used for photosynthesis, so that, it did not suffer from photoinhibition. In contrast, more light energy was allocated to fractions of heat dissipation in both P. tomentosa and H. tetratepala seedlings. Growing under 100% sunlight, these two species received more excess light energy, which caused photoinhibition. Our results support the idea that light requirements for the regeneration of three tropical tree species under different ecological habits are related to their characteristics of light energy utilization and dissipation.

Ecology↗
PubMed2004

[Response of photosynthesis and antioxygenic enzymes in seedlings of three tropical forest tree species to different light environments].

This paper studied the response of photosynthesis, chlorophyll a fluorescence and 3 antioxygenic enzyme activities in the seedlings of a pioneer species (Mallotus barbatus) and two endangered sub-canopy tree species (Litsea pierrei var. szemaois and L. dilleniifolia) in Xishuangbanna tropical rain forest to different light environments. Three light regimes (50%, 25% and 8% full sunlight) were designed for the seedlings. The largest values of maximum photosynthetic rates (Pmax) of L. pierrei var. szemaois and L. dilleniifolia were documented at 25% and 8% sunlight, respectively, which showed that the two sub-canopy species had poor ability in photosynthetic acclimation to high light. In contrast, the Pmax of M. barbatus increased with light level. During a day, the maximum photochemical efficiency (Fv/Fm) of the photosystem II in all the three species grown under three light levels showed minimum values at noon, and the lowest Fv/Fm values were shown in seedlings at 50% sunlight. Under 50% sunlight, the Fv/Fm values at dawn were lower in L. dilleniifolia than in the same species under other two light levels, indicating that sustained photoinhibition occurred in this case. The contents of malondialdehyde (MDA), H2O2, and activities of ascorbate peroxidase (APX), superoxid dismutase (SOD), catalase (CAT) of both L. pierrei var. szemaois and M. barbatus increased with stronger irradiance, which revealed that these two species were able to alleviate photodamage under high light stress by increasing their antioxigenic activities. But, high content of MDA revealed that L. dilleniifolia was probably suffered from membrane damage. In conclusion, our data revealed that the pioneer species M. barbatus had a high capacity to acclimate to different light environments, particularly high light, while the two subcanopy Litsea species had poor ability in acclimation to high light. Based on the findings of the present study, we suggest that the small populations and endangered status of both L. pierrei var. szemaois and L. dilleniifolia in natural environment could be partially due to their poor flexibility in response to changed light environment resulted from habitat fragmentation.

Catalase↗
PubMed1992

Comparison of parachute landing injury incidence between standard and low porosity parachutes.

Deployment of personnel by parachute is a common practice in many types of operations, both in and out of the military. Such operations are not without hazard and are associated with injuries which commonly occur during the landing phase of deployment. Environmental factors (i.e., wind and terrain) together with parachute sink rate are thought to influence the incidence of landing injuries. This study compared the incidence of overall landing injury and landing injury by parachute type in 8,706 jumps over 3 years between 1988 and 1990 between a standard porosity round canopy and a lower sink rate low porosity round canopy. In all cases the low porosity parachute group experienced significantly (p = 0.007) fewer overall injuries and fewer injuries of every type (reductions of 77% in 1988, 81% in 1989, and 94% in 1990). Reduction of sink rate by even small amounts correlates with significant (p less than 0.001) injury incidence reductions on the basis of reduced kinetic energy dissipation. Low porosity parachutes should be adopted where appropriate to reduce sink rate and hence landing injuries. Flight surgeons associated with airborne operations and who are familiar with these data can play a significant role in reducing parachute landing injuries.

Aerospace Medicine↗
PubMed2001

Planktonic primary production in a tidally influenced mangrove forest on the Pacific coast of Costa Rica.

The seasonal variation of planktonic primary productivity was measured during one year in the main channel in the interior part of the mangrove forest of the Estero de Morales (Estero de Punta Morales), a mangrove system located in the Golfo de Nicoya at the Pacific coast of Costa Rica. Samples were incubated at the surface, 0.5 m and 1.0 m depth and the "light and dark bottle technique" was employed. The annual gross primary productivity (PPg) was 457 and the net primary productivity (PPn) was 278 g C m(-2) a(-1). Daily PPg ranged from 0.29 to 3.88 and PPn from 0.12 to 2.76 g C m(-2) d(-1). The highest rates observed in May and September were due to red tide blooms. The seasonal variation of primary productivity inside the mangrove forest depends closely on the PP in the adjacent area of the upper Golfo de Nicoya. Obviously the PP was light-limited since the compensation depth in the ebb current was found at only 1 m depth. In the flood current it was somewhat deeper. The planktonic primary productivity inside the mangrove forest was completely restricted to the open channels. A simultaneous measurement demonstrated that PPn of the phytoplankton could not take place under the canopy of the mangroves. Additional studies on the time course of the oxygen concentration in the mouth of the main channel over 24 hrs demonstrated a relation between the O2 and the tidal curves. The ebb current had always lower O2 concentrations than the flood current, regardless of the time of the day. The difference to the foregoing high tide, however, was much smaller when the low tide occurred during the day. This indicates that under the canopy the net primary production and hence O2 liberation of the attached macro- and microalgae, together with the high PPn of the phytoplankton in the channels, helped the oxygen concentration not to decrease as far as during the night. Nevertheless it shows that the consumtion of organic material in the submersed part of the mangrove forest exceeds always its production.

Animals↗
PubMed2004

[Principle of "multiple ecological niche of one-species (variety)" and its application in high yield cotton cultivation].

The multiple ecological niche of one-species (variety) (MENOS) population is formed by one species (variety), but the ecological units have different temporal, spatial, nutritional, temperature, or water ecological niche. The formation of MENOS population is characterized by its specific object, one species (variety), multiple layer canopy, human being's active adjustment, specific niche breadth, and overlap and separation of ecological units. This paper analyzed the characteristics of the super high yield cotton population with dual ecological niche of one-species (variety) (DENOS). As for the yield components, MENOS has the characteristics of high yield canopy and different yield plants.

Adaptation, Biological↗
PubMed1992

Resting energy expenditure in patients with thermal injuries.

Resting energy expenditures (REE) were measured using indirect calorimetric techniques in 62 patients with burn injuries admitted during 1987 to 1989 and compared with similar measurements made during 1972 to 1973. Energy requirements were related to burn size in both populations, but were greater in the earlier population. In the present study, data from some patients were obtained using a canopy system and from others during mechanical ventilation and were analyzed separately. The regression of REE on burn size was linear for the canopy measurements (r = 0.724) and for the ventilator measurements (r = 0.579). REE data were corrected for the expected basal metabolic rate (BMR) for each patient, with appropriate adjustment for age and sex. The regression of REE per BMR on burn size was linear (r = 0.724), differing from the curvilinear relationship found during 1972 to 1973. These data suggest a change in postburn energy requirements, probably related to differences in patient management. Predictive equations based on older data can be expected to overestimate energy requirements in patients receiving modern burn therapy.

Adolescent↗
PubMed2004

[Diurnal variation of winter wheat water and heat fluxes of a simulation with photosynthesis-evapotranspiration coupled model].

A coupled model of winter wheat photosynthesis-evapotranspiration was established based on SPAC theory. Sensible heat and latent heat fluxes were calculated by two-layer model proposed by Shuttleworth and Wallace, and photosynthesis and evapotranspiration were coupled by the parameterization of canopy resistance. The model was validated with the data measured by eddy covariance method. The results showed that the simulated and observed values were accordant, and the model could simulate the diurnal variation of sensible heat and latent heat fluxes very well. Sensitivity analysis indicated that the sensitive parameters of canopy transpiration were wilting point, stomata conductance, reflectivity of leaves to infrared radiation, and convexity of photosynthesis response to light, while the sensitive parameter of soil evaporation was soil resistance. The model could be used to study the interactions between water and heat fluxes and environmental factors, and to instruct the irrigation scheme in the field.

Energy Metabolism↗
PubMed2004

Green-light supplementation for enhanced lettuce growth under red- and blue-light-emitting diodes.

Plants will be an important component of future long-term space missions. Lighting systems for growing plants will need to be lightweight, reliable, and durable, and light-emitting diodes (LEDs) have these characteristics. Previous studies demonstrated that the combination of red and blue light was an effective light source for several crops. Yet the appearance of plants under red and blue lighting is purplish gray making visual assessment of any problems difficult. The addition of green light would make the plant leave appear green and normal similar to a natural setting under white light and may also offer a psychological benefit to the crew. Green supplemental lighting could also offer benefits, since green light can better penetrate the plant canopy and potentially increase plant growth by increasing photosynthesis from the leaves in the lower canopy. In this study, four light sources were tested: 1) red and blue LEDs (RB), 2) red and blue LEDs with green fluorescent lamps (RGB), 3) green fluorescent lamps (GF), and 4) cool-white fluorescent lamps (CWF), that provided 0%, 24%, 86%, and 51% of the total PPF in the green region of the spectrum, respectively. The addition of 24% green light (500 to 600 nm) to red and blue LEDs (RGB treatment) enhanced plant growth. The RGB treatment plants produced more biomass than the plants grown under the cool-white fluorescent lamps (CWF treatment), a commonly tested light source used as a broad-spectrum control.

Biomass↗
PubMed2005

[Correlation analysis on the damage of Mikania micrantha to plant communities in Neilingdind Island of Guandong Province, China].

The analysis showed that 58 species of trees, short-trees and shrubs in Neilingding Island of Guangdong Province were damaged by M. micrantha, of which, woody trees accounted for 67%. Short-trees and sunny shrubs were damaged most seriously, followed by the communities with low canopy density consisted of only 2 dominant species, and those with high canopy density consisted of 5 or 6 dominant species. The coverage of M. micrantha mainly related to the vertical structure of plant communities. The taller the community height and the more the synusia, the lesser was the coverage of M. micrantha. The damaging ratio mainly related to species diversity and community density. The higher the species diversity and community density, the lower the damaging ratio was. The damaging degree mainly related to the coverage of other liana. The more the coverage of other liana, the higher was the damaging degree of M. micrantha.

China↗
PubMed2005

[CO2 concentration character in broad-leaved Korean pine forest of Changbai Mountains].

The CO2 concentration in broad-leaved Korean pine forest of Changbai Mountains was measured continuously with a CO2 infra-red analyzer in 2003. The results showed that the CO2 concentration in the forest had striking characteristics of temporal-spatial variations, which were mainly influenced by the physiological processes of plants, soil respiration, and intensity of turbulence exchange. In growing season, the daily maximum and minimum CO2 concentration appeared mostly on the surface floor at about 5:00 in the early morning and at canopy location at about 15:00 in the afternoon, respectively. There was an obviously process of forest CO2 emission when the inversion broke at dawn. The average CO2 concentration in forest was 377 micromol x mol(-1) in 2003, the maximum of monthly average appeared in January as 388 micromol x mol(-1), and the minimum of monthly average appeared in August as 352 micromol x mol(-1). The forest acted as CO2 source in night time and turned to sink in daytime, during growing season. In non-growing season, the forest acted as CO2 source in both daytime and night time, but still had a clear evidence of CO2 assimilation at noon, with canopy location during non-growing season.

Air↗
PubMed2005

Lead accumulation in surface soils and components of Balenites aegyptica specie in a Katsina urban area, Nigeria.

OBJECTIVE: The main objective of this paper is to assess the impact of various vehicular traffic densities on lead (Pb) accumulations in some environmental components in Katsina, a semi-arid urban area of Nigeria. METHODS: This was achieved by collecting and analyzing samples of surface soils, fruits, kernels, leaves, and barks of Balanites aegyptica from locations of different vehicular traffic densities in the area, and analyzing them for lead, using atomic absorption spectrophotometry. RESULTS: The results obtained revealed that the Pb concentration in the high, medium, low, and zero traffic density areas are, 75, 53, 35, and 12 microg x g(-1) respectively for the fruit pulp. They are also16, 13, 8, and 6 microg x g(-1) for fruit kernel and 44, 28, 17, and 9 microg x g(-1) respectively for leaves. For tree barks, the values are 138, 97, 64, and 18 microg x g(-1) respectively while for under-tree-canopy soil samples the mean values are 99, 74, 44, and 17 microg x g(-1). In the case of outside-canopy soil samples, the mean values are 113, 91, 50, and 18 microg x g(-1) respectively for the various classes of vehicular traffic density. CONCLUSION: These results indicate a strong influence of vehicular traffic density on Pb emission into surrounding atmosphere and its subsequent precipitation on soil and components of B. aegyptica specie in the area. Of all the samples, tree bark should be the best index of assessing Pb pollution in the area, as it maintains the closest contact with the surrounding atmosphere. Since Pb has no known lower limit for human tolerance, there is an urgent need for Pb pollution control in the area to be effectively enforced.

Balanites↗
PubMed2005

Spatial distribution of anopheline larval habitats in Western Kenyan highlands: effects of land cover types and topography.

The distributions of anopheline larval habitats were aggregated in valley bottoms in Kenya in both the rainy and dry seasons, although the degree of aggregation was higher in the dry season than in the rainy season. Larvae of the Anopheles gambiae complex larvae were found more frequently in habitats in farmlands and pastures. However, An. funestus larvae were found more frequently in natural swamps and pastures. Canopy cover was the only variable significantly associated with the occurrence of the An. gambiae complex and An. funestus. The average canopy cover was significantly less in the habitats with the An. gambiae complex and An. funestus larvae than those without the anopheline larvae. Thus, land cover types and topographic features showed important effects on the distribution of anopheline larval habitats. These results suggest that clearing riparian forests would improve growing conditions of the An. gambiae complex and An. funestus larvae in Kenyan highlands.

Animals↗