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151.
Takashi Yamanaka 《Mycoscience》1995,36(1):17-23
Organic matter composition (lignin, holocellulose, 50% (v/v) methanol extract, water-soluble carbohydrate (WSC) and phenolics (WSP), petroleum ether extract, and ash) of A0 layer soil treated with 700 g/m2 of urea to promote ammonia fungi was investigated in a Japanese red pine (Pinus densiflora) forest. Nine species of fungi were found during the study period of 18 months after the treatment. Of these, seven species belong to the ammonia fungi. WSC content of the treated soil was lower than that of the control. Methanol extract content increased initially after the treatment, then decreased to below the control level. There were no consistent differences in other components between the treated plot and the control. The abilities to decompose cellulose, lignin, chitin, protein and lipid in 18 strains in 10 species of the ammonia fungi were also screened. Cellulose was not lysed byPseudombrophila deerata, Hebeloma spp. andLaccaria bicolor. Strong lignolytic activity was shown byLyophyllum tylicolor, Coprinus echinosporus andP. deerata. Chitin was decomposed byAmblyosporium botrytis, L. tylicolor, C. echinosporus andHebeloma vinosophyllum. All strains possessed proteolytic and lipolytic activities. Supply of glucose to the culture media resulted in weaker enzyme activities except for lignolytic ability. 相似文献
152.
N. Visalakshi 《Journal of biosciences》1994,19(1):103-116
Seasonality in fine root standing crop and production was studied in two tropical dry evergreen forests viz., Marakkanam reserve
forest (MRF) and Puthupet sacred grove (PSG) in the Coromandel coast of India. The study extended from December 89 to December
91 in MRF and from August 90 to December 91 in PSG with sampling at every 2 months. Total fine interval. Mean fine root standing
crop was 134 g m−2 in MRF and 234 g m−2 in PSG. root production was 104 g m−2 yr−1 in MRF and 117 g m−2 yr−1 in PSG. These estimates lie within the range for fine roots reported for various tropical forests. Rootmass showed a pronounced
seasonal pattern with unimodal peaks obtained during December in the first year and from October–December in the second year
in MRF. In PSG greater rootmass was noticed from June–October than other times of sampling. The total root mass in MRF ranged
from 114 to 145 g m−2 at the 13 sampling dates in the three sites.
The live biomass fraction of fine roots in MRF ranged from 46 to 203 g m−2 and in PSG it ranged from 141 to 359 g mm−2 during the study periods. The dead necromass fraction of fine roots ranged from 6 to 37 g m−2 in MRF and from 12 to 66 g m−2 in PSG. Fine root production peaked during December in both the forest sites. The necromass fraction of newly produced roots
was negligible.
Total N was slightly greater in PSG than in MRF. Whereas total P level was almost similar in both the sites. The study revealed
that season and site characteristics influenced fine root system. 相似文献
153.
Yu. A. Kuznetsov M. Ya. Antonovsky V. N. Biktashev E. A. Aponina 《Journal of mathematical biology》1994,32(3):219-232
A simple mathematical model of mono-species forest with two age classes which takes into account seed production and dispersal is presented in the paper. This reaction — diffusion type model is then reduced by means of an asymptotic procedure to a lower dimensional reaction — cross-diffusion model. The existence of standing and travelling wave front solutions corresponding to the forest boundary is shown for the later model. On the basis of the analysis, possible changes in forest boundary dynamics caused by antropogenic impacts are discussed. 相似文献
154.
The seasonal dynamics of epilithic algae in a third order pristine forest stream were analyzed over a period of 2 years. Stream water was slightly acidic and nutrient poor. Encrusting, filamentous flocs, and filaments were found. Algal standing crop was high (mean concentration of Chl a 16–43 mg m–2) in spring. Filamentous algae contributed most to standing crop. Diatoms made up over 85% by number of the epilithon. Blue-greens were abundant upstream, and chlorophytes downstream. This shift was ascribed to greater light availability downstream. The community was more diverse during spring. Water current was the most important variable regulating epilithon structure. Total phosphorus (TP), orthophosphate (O-PO
inf4
su3–
), silica (Si4+), nitrate (NO
inf3
su–
) and conductance correlated negatively with flow rate. Green algae showed a positive correlation to phosphorus during low and stable flow. During rapid runoff, diatoms were the most resistant forms. Seasonal change in the epilithic community was mainly regulated by fluctuations in flow rate. 相似文献
155.
Summary The composition of the ant community was assessed along standardized 100 m transects in annually flooded Varzea forest and in terra firme forests on sandy soil (Flanco forest) and on claytopped mesas (Planalto forest). Standardized samples were taken by unit-time hand collecting (day and night times), sweeping, beating, baiting and by Winkler sacks. A total of 156 species, representing 49 genera were found, of which 98, 88 and 55 were respectively found in the Planalto, Flanco and Varzea forests. Species lists are presented and the ant community composition and species richness are compared between the three forests. By considering the nesting and foraging habits of the various species, the differences in overall community composition are related to the forest type and susceptibility to inundation of the three forests which were surveyed.The data confirm the view that tropical rain forests support an extremely diverse ant fauna and comparisons with other forested areas suggest that ant species richness declines in subtropical and temperate rain forests. Although alpha diversity is high, species turnover between forests is lower than expected, suggesting that ant species richness in this forested region is not as great as is implied in some published estimates of global arthropod diversity. 相似文献
156.
Abstract: Recent evidence suggests that platelet-activating factor plays a role in ischemia-induced neural injury. The Pulsinelli-Brierley four-vessel occlusion model was used to study the effect of a synthetic platelet-activating factor antagonist, BN 50739, and its solvents, either dimethyl sulfoxide or hydroxypropyl-β-cyclodextrin, on cerebral ischemia-reperfusion. Rats were subjected to either 30 min of ischemia or 30 min of ischemia followed by 60 min of recirculation. Changes in the brain mitochondrial free fatty acid pool size, fatty acyl composition of phospholipids, and respiratory function were monitored. When the BN 50739 (2 mg of BN 50739/kg of body weight i.v.) was administered at the onset of recirculation, it significantly reversed the ischemia-induced accumulation of mitochondrial free fatty acids and loss of polyunsaturated fatty acyl chains from phosphatidylcholine and phosphatidylethanolamine while simultaneously improving mitochondrial respiration. Dimethyl sulfoxide alone decreased the mitochondrial level of malonyldialdehyde and total free fatty acid pool size, but there was no improvement in mitochondrial respiration. Hydroxypropyl-β-cyclodextrin was reported to be pharmacologically inactive and capable of dissolving BN 50739. However, hydroxypropyl-β-cyclodextrin alone also caused a significant increase in content of cerebral mitochondrial membrane free fatty acids and hydrolysis of phosphatidylcholine in normoxic control animals. The overall effect of BN 50739 on mitochondrial structure and energy metabolism supports the hypothesis that platelet-activating factor may play a key role in ischemia-induced cerebral injury. 相似文献
157.
Diet of the brown howler monkeyAlouatta fusca in a semi-deciduous forest fragment of southeastern Brazil 总被引:1,自引:1,他引:0
Adriano Garcia Chiarello 《Primates; journal of primatology》1994,35(1):25-34
The diet of a group of six brown howlers was studied weekly during 12 months in a reserve of 250 ha of secondary, mesophytic,
semi-deciduous forest. The phenology of 186 trees of 72 species and 29 families was monitored simultaneously. Scan sampling
was used to record the diet from dawn until dusk on a total of 60 days of observation, yielding 718 hr of animal-observer
contact and 2,943 feeding scans. The diet was composed of leaves (73%), flowers (12%), and fruits (5%), from 68 identified
plant species.Celtis iguanae, Cassia ferruginea, andInga spp. were the main food sources, accounting for approximately 50% of the diet. Young leaves (59%) were preferred to mature
leaves (31%), trees contributing 56% and lianas 41% of the leaf diet. The ingestion of young leaves was correlated to the
availability of these items, however, the correlations were not significant for flowers and fruits. The diet was poorer in
fruits and richer in young leaves of lianas in comparison to other howler monkey species studies, probably as a consequence
of the liana abundance in this forest fragment. 相似文献
158.
Zagrodzki Paweł Mietelski Jerzy W. Krośniak Mirosław Petelenz Barbara 《Biological trace element research》1994,(1):273-277
The aim of this work was to check whether the stable cesium content in forest litter affects the value of radiocesium from
litter-to-mushroom transfer factorTf or not. Total cesium in litter, measured by AAS, varied from 0.1–2.7 μg/g. These data, combined with earlier results for
mushrooms, showed no simple correlation forTf. More complex relationships provided very high correlation coefficients, but their validity needs further investigation. 相似文献
159.
Analysis of nitrogen saturation potential in Rocky Mountain tundra and forest: implications for aquatic systems 总被引:3,自引:1,他引:2
Jill S. Baron Dennis S. Ojima Elisabeth A. Holland William J. Parton 《Biogeochemistry》1994,27(1):61-82
We employed grass and forest versions of the CENTURY model under a range of N deposition values (0.02–1.60 g N m–2 y–1) to explore the possibility that high observed lake and stream N was due to terrestrial N saturation of alpine tundra and subalpine forest in Loch Vale Watershed, Rocky Mountain National Park, Colorado. Model results suggest that N is limiting to subalpine forest productivity, but that excess leachate from alpine tundra is sufficient to account for the current observed stream N. Tundra leachate, combined with N leached from exposed rock surfaces, produce high N loads in aquatic ecosystems above treeline in the Colorado Front Range. A combination of terrestrial leaching, large N inputs from snowmelt, high watershed gradients, rapid hydrologic flushing and lake turnover times, and possibly other nutrient limitations of aquatic organisms constrain high elevation lakes and streams from assimilating even small increases in atmospheric N. CENTURY model simulations further suggest that, while increased N deposition will worsen the situation, nitrogen saturation is an ongoing phenomenon. 相似文献
160.
Nitrogen fixation by periphyton and plankton on the Amazon floodplain at Lake Calado 总被引:2,自引:1,他引:1
Nitrogen fixation by periphyton and plankton was measured on the Amazon flood-plain using the acetylene reduction method calibrated with15N-N2. The average ratio (± SD) of moles C2H4 reduced per mole N2-N fixed was 3.4 ± 0.7, similar to other studies. Periphyton and plankton had high rates of light-dependent nitrogen fixation, with dark nitrogen fixation averaging 26% of the average rates in the light. The average daily (24 h) rates for periphyton nitrogen fixation in 1989 and 1990 were 1.79 and 0.51 mmol N2-N·m–2·d–1 respectively, which are comparable to summer rates in many temperate cyanobacterial assemblages. Nitrogen fixation was depressed at N03
– concentrations as low as 0.5 M, and was below detection limits at concentrations of 4 M, which occurred during periods of river flooding. Planktonic nitrogen fixation rates were high (0.5–0.8 mmol N2-N·m–2·d–1) during the high-water and drainage phases of the annual hydrograph when the floodplain waters were draining towards the river (low NO3
–), but rates were undetectable (< 0.05 mmol N2-N·m–2·d–1) when there was river flooding (high NO3
–). Nitrogen fixation by periphyton and plankton in 1989–1990 accounted for approximately 8% of previously reported total annual nitrogen inputs to the floodplain at Lake Calado. 相似文献