Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “SEASONS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 937 records · Page 52Linked to original sources
PubMed1995

Liver and kidney concentrations of zinc, copper and cadmium in channel catfish (Ictalurus punctatus): variations due to size, season and health status.

Significant differences in liver and kidney concentrations of zinc (Zn), copper (Cu) and cadmium (Cd) were detected in normal Mississippi farm-raised channel catfish (Ictalurus punctatus) collected at different times of the year. These seasonal differences were not solely due to variation in fish size. Comparing the concentration of each metal in liver vs kidney indicated that Cd was lower in liver for all seasons studied, Cu was higher in liver for all seasons studied, and Zn was higher in the liver in the winter-killed (winter mortality syndrome) and the spring fish groups. Metal concentration was associated with body weight, as indicated by significant Pearson correlation coefficients for kidney Cd (all seasons and fall), liver Cu (summer), liver Zn (all seasons and winter), and kidney Zn (all seasons and winter). The adjusted means were not dramatically changed as compared to the raw data. Differences were noted when seasonal values obtained from normal fish were compared to tissues of moribund fish afflicted with winter mortality syndrome. Zinc was reduced in liver and kidney of these moribund fish.

Animals↗
PubMed1993

Seasonal variation of blood pressure and its relationship to ambient temperature in an elderly population.

OBJECTIVE: To measure the magnitude and timing of seasonal variation of blood pressure and related factors in the elderly living in the community, and to assess their potential impact on cardiovascular risk. DESIGN: Prospective study; from January 1991 to February 1992 blood pressure and other variables were measured at 2-monthly intervals in each subject in their own homes. SUBJECTS: Ninety-six men and women, age range 65-74 years, recruited from a single group general practice in Cambridge. MAIN OUTCOME MEASURES: Seasonal variation of blood pressure, seasonal variation of prevalence of hypertension, seasonal variation of ambient temperature and body mass index. RESULTS: Both systolic (SBP) and diastolic blood pressure (DBP) were greatest during the winter across the whole distribution of blood pressure. There was a fourfold increase in the proportion of subjects with blood pressures > 160/90 mmHg in winter compared with in summer. Regression analysis revealed highly significant seasonal differences in both SBP and DBP. After adjustment for confounding seasonal effects, a 1 degree C decrease in living-room temperature was associated with rises of 1.3 mmHg in SBP and 0.6 mmHg in DBP. CONCLUSIONS: Seasonal variation of blood pressure is heightened in older adults and may partly explain the greater cardiovascular disease mortality of elderly subjects during the winter. The blood pressures of elderly people may be inversely related to the ambient temperature. The public health implications of these findings deserve further investigation.

Aged↗
PubMed1993

[Seasonal variations in estrus behavior and ovulatory activity in Chios and Serres ewes in Greece].

Sheep are seasonal breeders, but a lower seasonality has been reported for sheep breeds from the Mediterranean countries enabling spring matings. To further substantiate this, the present study compared seasonal variation in oestrus behaviour and ovulation in two Greek breeds (Chios and Serres) maintained in the same environment. In 27 adult ewes of each breed, oestrus behaviour, the occurrence of ovulation and ovulation rate were monitored during 2 successive years by daily inspection by rams, weekly progesterone assay in circulating blood plasma and monthly ovarian laparoscopy. The periods of anoestrus (109 +/- 8 (wk) vs 178 +/- 5 d) and anovulation (63 +/- 8 vs 149 +/- 6 d) were significantly shorter (P < 0.001 and P < 0.001) and more variable in Chios than in Serres ewes. Furthermore, the percentage of ewes exhibiting oestrus at least once monthly was significantly higher from March to July in Chios than in Serres ewes. Continuous ovulation throughout the year was noted in 5 and 2 Chios ewes during year 1 and 2, respectively. Ovulation rate (3.25 +/- 0.15 vs 1.45 +/- 0.04) was higher in Chios than in Serres ewes (P < 0.001) while duration of oestrus was also longer in Chios ewes (1.8 +/- 0.05 vs 1.5 +/- 0.06 d; P = 0.002). There were significant correlations between the duration of anovulatory periods of the 2 successive years in Chios (r = 0.43) but not Serres ewes. Ovulation rate was positively related to the onset of the sexual season in Serres but not in Chios ewes. The present data suggest that: i) the efficiency of Serres but not in Chios ewes. The present data suggest that: i) the efficiency of spring mating in these breeds is suboptimal since it is a period when the percentage of ewes exhibiting oestrus and ovulation as well as ovulation rate are limited, ii) owing to the large variation in seasonality within Chios ewes and to the good between year correlation in features of seasonality, selection against seasonality in Chios ewes could be worthwhile.

Animals↗
PubMed1993

[Seasonal variation of sudden death based on analysis of death certificate information].

Seasonal variation of sudden death (SD) was studied based on analysis of death certificates of all 8,519 SD patients, aged 15 years or older, who died during 1984 to 1986 in Niigata prefecture, Japan. SD was defined as death within 24 hours of onset of the underlying cause. SD showed a significantly high incidence during the cold season. When analyzed by underlying cause, the high incidence during cold season was shown for SD by circulatory diseases such as acute myocardial infarction (AMI; n = 1,446), other cardiovascular diseases (OCD; n = 4,375) and cerebrovascular accident (CVA; n = 1,725). However, no significant seasonal variation was observed for SD by non-circulatory diseases. By age group, the incidence of SD due to circulatory diseases was high during the cold season in the elderly (61 to 75 years) and the old age (76 years or older) groups, irrespective of kinds of the diseases, whereas the pattern varied by disease type in the young to middle age group (15 to 60 years). The highest incidence of SD due to AMI in the young to middle age group occurred in January with a second peak in July to August. Thus, not only low temperatures but high temperatures seemed to also contribute to the occurrence of SD by AMI in this age group. While SD due to OCD in this age group did not show a significant seasonal variation, that due to CVA showed a high incidence during cold season similar to the older age groups. These results suggest that factors affecting the occurrence of SD differed according to underlying cause and age of victims.

Age Factors↗
PubMed1996

[Chemotactic serum activity for neutrophils and eosinophils and spontaneous production of histamine releasing factor in patients with seasonal bronchial asthma treated with nedocromil sodium].

Nedocromil sodium (NS- Tilade) is an effective therapeutic agent against asthma and has been shown to exhibit antiinflammatory activity in vitro. The aim of this study was to assess the effect of NS on the serum neutrophil (NCA) and eosinophil (ECA) chemotactic activity and mononuclear cells-derived histamine releasing factor (HRF) activity in 14 patients with seasonal allergic asthma. The chemotactic activities, HRF and bronchial reactivity to histamine (PC20H in mg/ml) were determined before the grass-pollen season and at the end of the 14-day placebo treatment and 21-day NS treatment during the pollen-season. NCA and ECA were assessed using of the Boyden chamber methods. Blood samples for mononuclear cells culture were collected during the trial. The supernatants were assayed for HRF activity with basophils from a single donor. The NCA index was unaltered during the trial. There was a significant (p < 0.05) increase in the ECA after the NS treatment period (ECA index--2.5) compared with out of season and after placebo treatment (ECA index, 1.88 and 1.82). HRF activity increased after placebo compared with out of season (HRF % activity--38.62 before season, 47.61 after placebo p < 0.05) but NS did not revealed the further effect on HRF activity (49.81 p > 0.05). During placebo the significant decrease in PC20H from 1.81 mg/ml to 0.54 mg/ml (p < 0.05) was observed. NS did not have the effect on nonspecific bronchial reactivity--PC20H--0.74 mg/ml (p > 0.05). The correlation between PC20H and spontaneous production of HRF activity was not found. The results indicate that NS has some effect on inflammatory process which takes place in seasonal asthmatic patients during the natural allergic exposure.

Adolescent↗
PubMed1996

Seasonal variation in the correlation of testicular and epididymal weight-dimensions in the red Sokoto goat and white Yankassa ram.

A correlative study of testicular weight (TW), length (TL), diameter (TD), epididymal weight (EW) and cauda epididymal weight (CEW) in adult red Sokoto goat and white Yankassa ram during the dry and wet seasons in Kano City, Nigeria was undertaken. The data was analyzed by Pearson's product of moment correlation coefficient and the results showed that TW maintained a highly significant correlation with TL, TD, TW and CEW in the ram, and goat during the wet season (p < 0.01), but non-significant correlation with TL and TD during the dry season (p > 0.05). This suggests that there is a seasonal variation in the dimensions of the reproductive organs of the animals and that during the breeding season (wet season) testicular size and weight are intimately correlated. During the wet season, the reproductive performance of these animals may be assessed by measuring their testicular size and will be very useful in animal husbandry.

Animals↗
PubMed2006

The sensitivity of ecosystem carbon exchange to seasonal precipitation and woody plant encroachment.

Ongoing, widespread increases in woody plant abundance in historical grasslands and savannas (woody encroachment) likely will interact with future precipitation variability to influence seasonal patterns of carbon cycling in water-limited regions. To characterize the effects of woody encroachment on the sensitivity of ecosystem carbon exchange to seasonal rainfall in a semi-arid riparian setting we used flux-duration analysis to compare 2003-growing season NEE data from a riparian grassland and shrubland. Though less seasonally variable than the grassland, shrubland NEE was more responsive to monsoon rains than anticipated. During the 2004-growing season we measured leaf gas exchange and collected leaf tissue for delta(13)C and nitrogen content analysis periodically among three size classes of the dominant woody-plant, Prosopis velutina and the dominant understory species, Sporobolus wrightii, a C(4) bunchgrass, present at the shrubland. We observed size-class and plant functional type independent patterns of seasonal plant performance consistent with greater-than-anticipated sensitivity of NEE in the shrubland. This research highlights the complex interaction between growing-season precipitation, plant-available alluvial groundwater and woody plant abundance governing ecosystem carbon balance in this semi-arid watershed.

Analysis of Variance↗
PubMed1987

Influence of season on estrous and luteinizing hormone responses to estradiol benzoate in ovariectomized sows.

The objective of this experiment was to determine whether seasonal differences existed in estrous and LH responses to estradiol benzoate (EB) in ovariectomized sows. Sows were ovariectomized after weaning their first litter, and treatment was begun 120 d after ovariectomy. Sows were given 400 mug EB intramuscularly (i.m.) on July 24, 1982 (summer), October 24, 1984 (fall), January 29, 1985 (winter), and March 27, 1985 (spring). Beginning 24 h after EB, sows were checked for estrus four times daily. Proportion in estrus was affected by season, with all sows exhibiting estrus within 5 d after EB in summer, winter, and spring. Only three of five sows exhibited estrus within 5 d after EB in fall. Interval (h) to estrus was delayed in fall (80 h) compared to other seasons (62.6 h; SEM = 4.5). Concentrations of LH were suppressed within 6 h after EB in all seasons but rebounded to pre-injection levels more slowly in fall and spring than in winter and summer. Frequency of LH peaks (3.2 +/- .4 4 h ) was not affected by season, but amplitude (1.9 vs 0.9 ng/ml) and baseline (2.7 vs 1.6 ng/ml) were greater (P < 0.05) for summer than for the other seasons combined. At 6 h after injection, concentrations of estradiol-17beta (pg/ml) were greater in summer (58.3) than in fall (19.0), winter (32.4), or spring (16.6; SEM = 10.4). We conclude that environmental factors associated with season alter responsiveness of the brain to estradiol, thereby controlling sexual behavior and LH secretion.

Journal Article↗
PubMed1990

Time of ovulations in dairy goats induced to superovulate with porcine follicle stimulating hormone during and out of the breeding season.

Alpine dairy goats were induced to superovulate at the end of a progestagen treatment with porcine follicle stimulating hormone (pFSH) during the breeding season (n = 10 goats) and out of the breeding season (n = 10 goats). Occurrence of estrus and of the luteinizing hormone (LH) peak were checked every 4 h. Ovulations were determined every 6 h by ovarian laparoscopic examination. Among the parameters studied, the mean interval from sponge removal to the onset of estrus did not differ whatever the season of treatment, but the variability was higher for females treated out of the breeding season. Ovulations began during the laparoscopic control period for nine of ten goats during the breeding season vs seven of ten goats out of the breeding season. For these 16 females, on which the LH peak and beginning of ovulation were known, the season did not affect the intervals between the onset of estrus and the LH peak and between the LH peak and the beginning of ovulation. When ovulations are observed by laparoscopy every 6 h, for any given goat 54.9% of total ovulations (counted 7 d after estrus) occurs in less than 6 h, and 87.1% in less than 12 h. Although the interval between the LH peak and the ovulation is quite constant, the additive variabilities of the intervals between the sponge removal and the onset of estrus and between the onset of estrus and the LH peak precluded the determination of an optimal time for artificial insemination (AI) by timing sponge removal or onset of estrus.

Journal Article↗
PubMed2006

Aortic responsiveness to nitric oxide is affected by seasonal variation.

Cardiac attacks and sudden cardiac deaths are more common in cold seasons. Up to now the underlying pathophysiologic mechanism of the seasonal variation in cardiovascular accidents is scarcely known. There are many physiological mechanisms which exhibit seasonal variation (e.g. blood pressure). Nitric oxide (NO) is a potent vasodilator, and impaired responsiveness to its physiological effects has been reported in many pathological situations including cardiovascular accidents. The aim of the present study was to evaluate the role of NO-dependent mechanisms on seasonal variation in aortic relaxation in vitro in rats. Male Sprague-Dawley rats grown up in different seasons in natural light/dark situation were used in the study, while the temperature and humidity were kept constant throughout the study (22+/-1 degrees C). The in vitro aortic ring responsiveness to an NO donor was studied in different seasons. Intact and denuded rings were pre-contracted with phenylephrine and vaso-relaxatory response to sodium isosorbide dinitrate (10(-8) to 10(-4)M) was recorded in vitro. The vaso-relaxatory response to isosorbide dinitrate (10(-6)M) was higher in aortic rings obtained in summer compared with those in winter and fall. There was a significant difference in EC(50) of sodium isosorbide dinitrate-induced vaso-relaxation of rings obtained from rats which were grown up in summer and winter (EC(50): 2.23+/-0.069 versus 4.31+/-0.088, P<0.05). The maximum response (R(max)) to isosorbide dinitrate was, however, identical in rings obtained from these rats. In conclusion, the in vitro responsiveness of aorta to NO is affected by seasonal light/dark periods the rats are exposed. This might be one of the reasons why more sudden cardiac deaths occur also in humans during winter.

Journal Article↗
PubMed2003

Maternal morbidity and perinatal outcomes among pregnant women with respiratory hospitalizations during influenza season.

OBJECTIVES: A population-based assessment of maternal and perinatal morbidity related to respiratory illness during influenza season among pregnant women has not been published. The objectives of this investigation were to describe and quantify the impact of respiratory hospitalization during pregnancy on serious maternal and perinatal morbidity. STUDY DESIGN: A matched cohort study using an administrative database of pregnant women enrolled in the Tennessee Medicaid population to determine pregnancy outcomes associated with respiratory hospitalizations during influenza season. Pregnant women aged 15 to 44 years with a respiratory hospitalization during influenza seasons 1985-1993 were matched by gestational age and presence of comorbidity with pregnant control subjects without a respiratory hospitalization. RESULTS: During the eight influenza seasons studied, 293 women with singleton pregnancies had respiratory disease hospitalizations (5.1:1000). Women with asthma had high rates of such hospitalization (59.7:1000). Compared with matched controls, women with respiratory hospitalizations had similar modes of delivery, delivery length of stay, and episodes of preterm labor. The prevalence of prematurity and low birth weight among infants born to such women was likewise similar between the two groups. CONCLUSION: In this population of pregnant women, those with asthma accounted for half of all respiratory-related hospitalizations during influenza seasons, with 6% of pregnant women with asthma requiring respiratory hospitalization during influenza season, (odds ratio 10.63, 95% CI, 8.18-13.83, compared with women without a medical comorbidity). We detected no significant increase in adverse perinatal outcomes associated with respiratory hospitalizations during influenza season.

Adult↗
PubMed2001

Seasonal changes in circadian grazing patterns of Kerry cows (Bos Taurus) in semi-feral conditions in Killarney National Park, Co. Kerry, Ireland.

Domestic cattle generally graze during the day although some night-time grazing also occurs. However, questions remain as to the effect of management on circadian grazing patterns. This study provides for the first time a quantification of seasonal, circadian and animal variation in grazing behaviour and grazing time in cattle in semi-wild conditions.The objectives of the study were to examine how daily grazing times and the temporal distribution of grazing activity changed with season and to examine the extent to which grazing patterns were influenced by day-length. A group of 12 heifers of the Kerry breed continuously grazed a lowland field of 4.7ha. The old permanent pasture sward was dominated by Holcus spp. and Agrostis spp. Feed availability was never limiting. Length and periodicity of grazing were recorded using vibracorders attached to the necks of seven animals.Results showed that daily grazing times remained constant over most of the grazing season (circa 10-11h per day), however, some variation occurred late in the season. The temporal distribution of grazing activity changed as the season advanced so that by October grazing patterns became significantly different to those of July. The time interval between grazing bouts at dawn and dusk decreased with decreasing day-length. An increased percentage of night-time grazing occurred at shorter day-lengths.It is concluded that there is a significant seasonal effect of day-length on temporal distribution of grazing activity with night-time grazing featuring more as day-length decreases. The maintenance of similar total daily grazing times in the face of changing day-length (with the exception of late in the season) suggests that daily grazing times are a function of the attainment of a relatively constant nutritional requirement by the animal.

Journal Article↗
PubMed1997

A cross-sectional study of helminths in rural scavenging poultry in Tanzania in relation to season and climate.

A cross-sectional study on the prevalence of helminths in rural scavenging poultry on six hundred adult chickens selected randomly from six villages in the Morogoro Region, Tanzania during the wet and the dry seasons, was conducted. The trachea and gastrointestinal tract of each bird were examined for the presence of parasites. All chickens were infected with one or several species of helminths, the average being 4.8 +/- 1.7 helminths per chicken during the wet season and 5.1 +/- 1.8 during the dry season. A total of 29 different helminth species were shown in the trachea or the gastrointestinal tract. The following species were identified: Syngamus trachea (0.7% (wet season), 2% (dry season)); Gongylonema ingluvicola (6.3%, 17.7%); Tetrameres americana (54.3%, 60.3%); Dispharynx nasuta (0%, 2.7%); Acuaria hamulosa (8.3%, 19.3%); Ascaridia galli (28.3%, 32.3%); Heterakis gallinarum (74.0%, 78.7%); H. isolonche (18.7%, 5.0%); H. dispar (25.7%, 6.3%); Allodapa suctoria (40.0%, 52.0%); Subulura strongylina (3.3%, 1.0%); Strongyloides avium (0.3%, 3.0%); Capillaria annulata (2.0%, 0.0%); C. contorta (9.0%, 1.0%); C. caudinflata (2.0%, 4.3%); C. obsignata (8.7%, 25.0%); C. anatis (4.0%, 9.0%); C. bursata (1.0%, 2.7%); Raillietina echinobothrida (41.3%, 46.3%); R. tetragona (25.3%, 21. 3%); R. cesticillus (8.7%, 2.7%); Choanotaenia infundibulum (0.0%, 3. 7%); Hymenolepis carioca (9.0%, 18.0%); H. cantaniana (48.0%, 43. 0%); Amoebotaenia cuneata (39.3%, 36.0%); Metroliasthes lucida (1.0%, 0.3%); Davainea proglottina (5.7%, 0.3%) and Polymorphus boschadis (0.3%, 0.0%). No trematodes were found. No correlation was found between season and prevalence, or season and mean worm burdens. Twelve helminths of the species recovered represent new local records.

Animals↗
PubMed1988

Photoperiodic and melatonin treatments for the control of seasonal reproduction in sheep and goats.

The control of seasonal reproductive activity in sheep and goats in open sheds, needs extra-light (E) during the photosensitive phase (equivalent to long days, LD), followed by treatment with melatonin (equivalent to short days, SD). In autumn-born Ile-de-France or Lacaune ram lambs, 2 months of E followed by decreasing daylength for 90 days, advanced onset of the first breeding season by allowing males to reach their maximum testis volume and sperm production earlier than for untreated ram lambs. Substitution of decreasing daylength with melatonin implants allowed a transient increase in testis volume. Adult Ile-de-France rams maintained under short light rhythms with 2 month-period, demonstrated, during at least 2 consecutive years, a testis volume equivalent to that observed during the normal breeding season. These light-treated rams produced, during non-breeding season, spermatozoa in the same quantity and quality as during the normal breeding season. In anovulatory out-of-season dairy goats, E treatment was demonstrated to be necessary before melatonin treatment and melatonin to be necessary after E treatment to stimulate oestrous and ovulatory activities. Stimulation of the anovulatory females by the introduction of treated males ("male effect"), appeared to be necessary to obtain maximum stimulation of the treated females. Two months of E, followed by melatonin treatment (daily injection or drenching or subcutaneous implants) allowed cycles with ovulation to be maintained for more than 2 months. Although effective for control of out-of-season reproductive activity, melatonin slightly decreased milk production when applied soon after kidding. So, total control of reproduction in sheep and goats by manipulation of photoperiod in open sheds and melatonin treatments appears feasible in both sexes.

Animals↗
PubMed1992

Contrasting leaf phenotypes control seasonal variation in water loss in a tropical forest shrub.

Psychotria marginata, a shrub common to humid tropical forests in Central America, produces leaves in two seasonal flushes with contrasting morphology and physiology. Leaf production is bimodal with a major peak at the beginning of the annual wet season and a secondary peak at the end of the wet season. Together these peaks account for 75-87% of annual leaf production. Leaves produced just prior to the dry season have higher specific mass and, during drought, have lower stomatal conductances and higher water-use efficiencies. Plants irrigated during two consecutive dry seasons continued to produce leaves with these morphological and physiological differences, indicating that this feature has been strongly canalized by some factor other than water availability in this highly predictable yet seasonal habitat. The bimodal leaf production results in acclimation to changing conditions through co-occurring leaves that lack the physiological plasticity usually associated with acclimation. Heterophylly of this form suggests that the moderate drought of the dry season has been a significant selective factor for understory plants.

Journal Article↗
PubMed1998

Seasonal trends in the birth of sinistrals.

This study examined the proposition that hand preference may change with season of birth in a group of 523 students born in southern Australia. Hand preference and performance measures revealed a higher incidence of sinistrality or weak dextrality for individuals born in winter and autumn compared to summer and spring. These seasonal effects tended to be more pronounced for females compared to males. Similar seasonal patterns have been observed in the northern hemisphere. Previous research has accounted for seasonal changes in hand preference in terms of changes in the frequency of viral infections. It is proposed that seasonal variations in hand preference can also be accounted for by seasonal variations in hormone levels. Higher levels of testosterone in spring compared to autumn have been reported in females. Exposure to higher levels of testosterone during the first trimester of foetal development is thought to promote the development of the right hemisphere. Individuals born in winter would have been exposed to the high testosterone levels associated with spring during the first critical trimester of foetal brain development. The lack of seasonal effect observed for males may be related to endocrinological differences between the male and female foetus.

Journal Article↗
PubMed2002

Parametric and semiparametric approaches to testing for seasonal trend in serial count data.

We present two tests for seasonal trend in monthly incidence data. The first approach uses a penalized likelihood to choose the number of harmonic terms to include in a parametric harmonic model (which includes time trends and autogression as well as seasonal harmonic terms) and then tests for seasonality using a parametric bootstrap test. The second approach uses a semiparametric regression model to test for seasonal trend. In the semiparametric model, the seasonal pattern is modeled nonparametrically, parametric terms are included for autoregressive effects and a linear time trend, and a parametric bootstrap test is used to test for seasonality. For both procedures, a null distribution is generated under a null Poisson model with time trends and autoregression parameters. We apply the methods to skin melanoma incidence rates collected by the surveillance, epidemiology, and end results (SEER) program of the National Cancer Institute, and perform simulation studies to evaluate the type I error rate and power for the two procedures. These simulations suggest that both procedures are alpha-level procedures. In addition, the harmonic model/bootstrap test had similar or larger power than the semiparametric model/bootstrap test for a wide range of alternatives, and the harmonic model/bootstrap test is much easier to implement. Thus, we recommend the harmonic model/bootstrap test for the analysis of seasonal incidence data.

Journal Article↗
PubMed1999

Transpiration increases during the dry season: patterns of tree water use in eucalypt open-forests of northern Australia.

Australian savannas exhibit marked seasonality in precipitation, with more than 90% of the annual total falling between October and May. The dry season is characterized by declining soil water availability and high vapor pressure deficits (up to 2.5 kPa). We used heat pulse technology to measure whole-tree transpiration rates on a daily and seasonal basis for the two dominant eucalypts at a site near Darwin, Australia. Contrary to expectations, transpiration rates were higher during the dry season than during the wet season, largely because of increased evaporative demand and the exploitation of groundwater reserves by the trees. Transpiration rates exhibited a marked hysteresis in relation to vapor pressure deficit, which was more marked in the dry season than in the wet season. This result may be attributable to low soil hydraulic conductivity, or the use of stored stem water, or both. Tree water use was strongly correlated with leaf area and diameter at breast height and there were no differences in transpiration between the species studied. These results are discussed in relation to scaling tree water use to stand water use.

Journal Article↗