Seasonal Changes in Leaf Water Characteristics of Eucalyptus tetrodonta and Terminalia ferdinandiana Saplings in a Northern Australian Savanna

1999 ◽  
Vol 47 (4) ◽  
pp. 587 ◽  
Author(s):  
D. Eamus ◽  
L. D. Prior
Keyword(s):  
Osmotic Potential ◽  
Seasonal Changes ◽  
Tree Height ◽  
Dry Weight ◽  
Dry Season ◽  
Leaf Water ◽  
Wet Season ◽  
Mature Trees ◽  
Turgor Loss Point ◽  
Terminalia Ferdinandiana

The monsoonal areas of northern Australia experience extreme seasonal variations in rainfall, with an annual dry season of 7 months or more. Seasonal changes in leaf water relations were investigated for saplings of two tree species common in northern Australian savannas: Eucalyptus tetrodonta F.Muell, an evergreen, and Terminalia ferdinandiana Excell, which is deciduous. Saplings may experience more severe water stress than mature trees because their root systems are less extensive. This study found a positive correlation between pre-dawn leaf water potential and tree height during the dry season, but not during the wet season, for both E. tetrodonta and T. ferdinandiana trees. Pressure–volume curves were constructed for leaves of E. tetrodonta saplings at 2-monthly intervals throughout the year. Osmotic potential at full turgor decreased from a maximum of −1.33 MPa in February (wet season) to −2.25 MPa in October (late dry season), then increased to an intermediate value of −1.71 MPa in December (early wet season). Leaves of T. ferdinandiana saplings were compared in February (wet season) and April (end of wet season; before leaf senescence). Osmotic potential at full turgor decreased from −1.18 MPa in February to −1.39 MPa in April. The capacity for turgor maintenance was larger for E. tetrodonta than for T. ferdinandiana, with osmotic potential at full turgor and the turgor loss point, relative water content at the turgor loss point and the ratio of turgid weight to dry weight all lower in E. tetrodonta.

scholarly journals The seasonal changes of the gut microbiome of the population living in traditional lifestyles are represented by characteristic species-level and functional-level SNP enrichment patterns

BMC Genomics ◽  
2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Xue Zhu ◽  
Jiyue Qin ◽  
Chongyang Tan ◽  
Kang Ning
Keyword(s):  
Gut Microbiome ◽  
Seasonal Changes ◽  
Dry Season ◽  
Urban Setting ◽  
Snp Analysis ◽  
Wet Season ◽  
Human Gut ◽  
Human Gut Microbiome ◽  
Genome Level ◽  
Prevalent Species

Abstract Background Most studies investigating human gut microbiome dynamics are conducted on humans living in an urban setting. However, few studies have researched the gut microbiome of the populations living traditional lifestyles. These understudied populations are arguably better subjects in answering human-gut microbiome evolution because of their lower exposure to antibiotics and higher dependence on natural resources. Hadza hunter-gatherers in Tanzania have exhibited high biodiversity and seasonal patterns in their gut microbiome composition at the family level, where some taxa disappear in one season and reappear later. Such seasonal changes have been profiled, but the nucleotide changes remain unexplored at the genome level. Thus, it is still elusive how microbial communities change with seasonal changes at the genome level. Results In this study, we performed a strain-level single nucleotide polymorphism (SNP) analysis on 40 Hadza fecal metagenome samples spanning three seasons. With more SNP presented in the wet season, eight prevalent species have significant SNP enrichment with the increasing number of SNP calling by VarScan2, among which only three species have relatively high abundances. Eighty-three genes have the most SNP distributions between the wet season and dry season. Many of these genes are derived from Ruminococcus obeum, and mainly participated in metabolic pathways including carbon metabolism, pyruvate metabolism, and glycolysis. Conclusions Eight prevalent species have significant SNP enrichments with the increasing number of SNP, among which only Eubacterium biforme, Eubacterium hallii and Ruminococcus obeum have relatively high species abundances. Many genes in the microbiomes also presented characteristic SNP distributions between the wet season and the dry season. This implies that the seasonal changes might indirectly impact the mutation patterns for specific species and functions for the gut microbiome of the population that lives in traditional lifestyles through changing the diet in wet and dry seasons, indicating the role of these variants in these species’ adaptation to the changing environment and diets.

scholarly journals Seasonal changes in water quality and macrophytes and the impact of cattle on tropical floodplain waterholes

2012 ◽  
Vol 63 (9) ◽  
pp. 788 ◽  
Author(s):  
N. E. Pettit ◽  
T. D. Jardine ◽  
S. K. Hamilton ◽  
V. Sinnamon ◽  
D. Valdez ◽  
...  
Keyword(s):  
Water Quality ◽  
Seasonal Changes ◽  
Aquatic Macrophyte ◽  
Plant Cover ◽  
Critical Role ◽  
Dry Season ◽  
Nutrient Concentrations ◽  
Wet Season ◽  
Dry Tropics ◽  
The Impact

The present study indicates the critical role of hydrologic connectivity in floodplain waterholes in the wet–dry tropics of northern Australia. These waterbodies provide dry-season refugia for plants and animals, are a hotspot of productivity, and are a critical part in the subsistence economy of many remote Aboriginal communities. We examined seasonal changes in water quality and aquatic plant cover of floodplain waterholes, and related changes to variation of waterhole depth and visitation by livestock. The waterholes showed declining water quality through the dry season, which was exacerbated by more frequent cattle usage as conditions became progressively drier, which also increased turbidity and nutrient concentrations. Aquatic macrophyte biomass was highest in the early dry season, and declined as the dry season progressed. Remaining macrophytes were flushed out by the first wet-season flows, although they quickly re-establish later during the wet season. Waterholes of greater depth were more resistant to the effects of cattle disturbance, and seasonal flushing of the waterholes with wet-season flooding homogenised the water quality and increased plant cover of previously disparate waterholes. Therefore, maintaining high levels of connectivity between the river and its floodplain is vital for the persistence of these waterholes.

Seasonal Distribution and Abundance of Dugongs in the Western-Gulf-of-Carpentaria

1989 ◽  
Vol 16 (2) ◽  
pp. 141 ◽  
Author(s):  
P Bayliss ◽  
WJ Freeland
Keyword(s):  
Relative Density ◽  
Relative Abundance ◽  
Coastal Waters ◽  
Seasonal Changes ◽  
Aboriginal People ◽  
Dry Season ◽  
Seasonal Distribution ◽  
Wet Season ◽  
Aerial Surveys ◽  
The 1960S

Aerial surveys of coastal waters (27 216 km2) in the western Gulf of Carpentaria during the dry season of 1984 and wet season of 1985 indicated no major seasonal changes in distribution and relative abundance of dugongs. Minimum population size in the dry season was estimated as 16 816 � 2946 (standard error), with a relative density of 0.62 k 0.11 km-2, and that for the wet season 16 846 + 3257, with a relative density of 0.62 � 0.12 km-2. The estimates exclude 5% of observations which could have been either dugongs or Irrawaddy dolphins, and were corrected for submerged dugongs and those missed on the surface. Dugongs were unevenly distributed over the study area, and neither mean group size nor proportion of calves varied between seasons. Dugong abundance was correlated with area of available seagrass. The catch rate of dugongs by Aboriginal people off Numbulwar decreased six-fold between the 1960s and 1985 (60 to 10 p.a.), possibly due to excessive hunting.

scholarly journals Contrasting patterns of litterfall seasonality and seasonal changes in litter decomposability in a tropical rainforest region

2014 ◽  
Vol 11 (6) ◽  
pp. 7901-7929
Author(s):  
S. A. Parsons ◽  
V. Valdez-Ramirez ◽  
R. A. Congdon ◽  
S. E. Williams
Keyword(s):  
Seasonal Changes ◽  
Biogeochemical Cycles ◽  
Dry Season ◽  
Tropical Region ◽  
Soil N ◽  
Wet Season ◽  
Evergreen Forests ◽  
P Limitation ◽  
Global Trend ◽  
The Difference

Abstract. The seasonality of litter inputs in forests has important implications for understanding ecosystem processes and biogeochemical cycles. We quantified the drivers of seasonality in litterfall and leaf decomposability, using plots throughout the Australian wet tropical region. Litter fell mostly in the summer (wet, warm) months in the region, but other peaks occurred throughout the year. Litterfall seasonality was modelled well with the level of deciduousness of the site (plots with more deciduous species had lower seasonality than evergreen plots), temperature (higher seasonality in the uplands), disturbance (lower seasonality with more early secondary species) and soil fertility (higher seasonality with higher N : P/P limitation) (SL total litterfall model 1 = deciduousness + soil N : P + early secondary sp: r2 = 0.63, n = 30 plots; model 2 = temperature + early secondary sp. + soil N : P: r2 = 0.54, n = 30; SL leaf = temperature + early secondary sp. + rainfall seasonality: r2 = 0.39, n = 30). Leaf litter decomposability was lower in the dry season than in the wet season, driven by higher phenolic concentrations in the dry, with the difference exacerbated particularly by lower dry season moisture. Our results are contrary to the global trend for tropical rainforests; in that seasonality of litterfall inputs were generally higher in wetter, cooler, evergreen forests, compared to generally drier, warmer, semi-deciduous sites that had more uniform monthly inputs. We consider this due to more diverse litter shedding patterns in semi-deciduous and raingreen rainforest sites, and an important consideration for ecosystem modellers. Seasonal changes in litter quality are likely to have impacts on decomposition and biogeochemical cycles in these forests due to the litter that falls in the dry being more recalcitrant to decay.

scholarly journals Temporal Variations of Submarine Groundwater Discharge into a Tide-Dominated Coastal Wetland (Gaomei Wetland, Western Taiwan) Indicated by Radon and Radium Isotopes

Water ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1806 ◽  
Author(s):  
Feng-Hsin Hsu ◽  
Chih-Chieh Su ◽  
Pei-Ling Wang ◽  
In-Tian Lin
Keyword(s):  
Coastal Waters ◽  
Seasonal Changes ◽  
Submarine Groundwater Discharge ◽  
Coastal Wetland ◽  
Groundwater Discharge ◽  
High Tide ◽  
Dry Season ◽  
Wet Season ◽  
Submarine Groundwater ◽  
Δd And Δ18o

Submarine groundwater discharge (SGD) is evidenced around Taiwan, but the seasonal/temporal changes of SGD have not been fully examined. Here, we report a time-series investigation of SGD into a tide-dominated coastal wetland, the Gaomei Wetland, located to the south of the Da-Chia River’s mouth, western Taiwan, by using environmental tracers (222Rn, 224Raex, 228Ra, δD, and δ18O). Our results showed that regardless of dry and wet seasons, the 222Rn activities in coastal waters were high at low tide but low at high tide. It represents the continuous input of 222Rn-enriched groundwater. However, the 224Raex and 228Ra activities showed seasonal changes with tide conditions. In the dry season, the 224Raex and 228Ra activities in coastal waters were low at low tide but high at high tide; whereas in the wet season, an opposite relation was observed with quite high 224Raex and 228Ra activities in the low-tide waters. Coupled with the lower δD and δ18O values of coastal and pore waters in the dry season, in comparison to those in the wet season, it is suggested that these phenomena probably reflected a seasonal difference in the main SGD component with fresh SGD in the dry season, but saline ones in the wet season. Based on a 222Rn mass balance model, the estimated SGD fluxes into the Gaomei Wetland varied with tidal fluctuations and ranged from 0.2 to 25 cm d−1 and from 0.1 to 47 cm d−1 for the dry and wet seasons, respectively. A slightly high SGD flux occurring during the wet season at spring tide, implied a stronger tidal pumping coupled with a larger hydraulic gradient between land and sea. In this study, we demonstrated that the variation of SGD into the Gaomei Wetland is not only controlled by the seasonal changes of groundwater recharge, but also by the tidal pumping process.

The ecology of small mammals in Ogba Forest Reserve, Nigeria

1989 ◽  
Vol 5 (1) ◽  
pp. 51-64 ◽  
Author(s):  
John Giobaguan Iyawe
Keyword(s):  
Small Mammals ◽  
Seasonal Changes ◽  
Common Species ◽  
Dry Season ◽  
Small Rodents ◽  
Wet Season ◽  
Forest Reserve ◽  
Percentage Composition ◽  
Monthly Variations ◽  
Arvicanthis Niloticus

ABSTRACTA total of 392 small mammals belonging to five species of small rodents and four species of shrews were caught. The small mammals and their percentage composition were Crocidura nigeriae (20.9%), Crocidura grandiceps (11.7%), Crocidura crossei (9.7%), Crocidura flavescens manni (20.4%), Mus musculoides (39.0%), Praomys tullbergi (11.5%), Lophuromys sikapusi (3.6%), Lemniscomys striatus (1.3%), and Arvicanthis niloticus (0.3%).There were monthly variations in the number of Mus musculoides and Crocidura nigeriae.In Mus musculoides breeding was at a maximum at the beginning and towards the end of the wet season and early dry season. In Crocidura nigeriae breeding was maximal during the wet season and low in the dry season.The seasonal changes in the age structure of the two most common species: Mus musculoides and Crocidura nigeriae, are described.

scholarly journals Seasonal leaf gas exchange and water potential in a woody cerrado species community

2004 ◽  
Vol 16 (1) ◽  
pp. 7-16 ◽  
Author(s):  
Carlos Henrique Britto de Assis Prado ◽  
Zhang Wenhui ◽  
Manuel Humberto Cardoza Rojas ◽  
Gustavo Maia Souza
Keyword(s):  
Gas Exchange ◽  
Water Potential ◽  
Leaf Water Potential ◽  
Leaf Gas Exchange ◽  
Water Status ◽  
Dry Season ◽  
Leaf Water ◽  
Wet Season ◽  
Leaf Water Status ◽  
Mean Values

Predawn leaf water potential (psipd) and morning values of leaf gas exchange, as net photosynthesis (A), stomatal conductance (gs), transpiration (E), and morning leaf water potential (psimn) were determined seasonally in 22 woody cerrado species growing under natural conditions. Despite the lower mean values of psipd in the dry season (-0.35 ± 0.23 MPa) compared to the wet season (-0.08 ± 0.03 MPa), the lowest psipd in the dry season (-0.90 ± 0.00 MPa) still showed a good nocturnal leaf water status recovery for all species studied through out the year. Mean gs values dropped 78 % in the dry season, when the vapor pressure of the air was 80% greater than in the wet season. This reduction in gs led to an average reduction of 33% in both A and E, enabling the maintainance of water use efficiency (WUE) during the dry season. Network connectance analysis detected a change in the relationship between leaf gas exchange and psimn in the dry season, mainly between gs-E and E-WUE. A slight global connectance value increase (7.25 %) suggested there was no severe water stress during the dry season. Multivariate analysis showed no link between seasonal response and species deciduousness, suggesting similar behavior in remaining leaves for most of the studied species concerning leaf gas exchange and psimn under natural drought.

Shoot phenology and water relations of Piceaglauca

1989 ◽  
Vol 19 (10) ◽  
pp. 1287-1290 ◽  
Author(s):  
Steven C. Grossnickle
Keyword(s):  
Osmotic Potential ◽  
Dry Weight ◽  
Shoot Elongation ◽  
Water Relation ◽  
Day Length ◽  
Late Winter ◽  
Turgor Loss Point ◽  
Shoot Dry Weight ◽  
Length Changes ◽  
Shoot Phenology

Piceaglauca var. albertiana (S. Brown) Sarg. shoot phenology and water relation parameters were monitored monthly for 1 year. Seedlings were kept outdoors, well watered, and exposed to seasonal changes in temperature and day length. Changes in shoot water relation parameters corresponded with changes in phenology. During spring, shoot elongation, osmotic potential at saturation, and turgor loss point were least negative, −1.30 and −1.56 MPa, respectively, whereas bulk modulus of elasticity at full turgor was at its highest, 22 MPa. Both osmotic potential at saturation and turgor loss point were most negative, −2.01 and −2.73 MPa, respectively, during late winter just before bud break. Shoot dry weight fraction was at its lowest, 0.33 g dry wt./g shoot weight and maximum symplastic water per unit weight of shoot tissue was at its highest, 3.99 g H2O/g dry wt., during spring shoot elongation. Number of osmoles of solute per kilogram shoot dry weight was highest during spring and late summer shoot elongation phases, 1.03 and 0.91 osmol/kg dry wt., respectively. These data suggest that P. glauca seedlings do not adjust well to dry site conditions.

Seasonal changes in leaf water relations and cell membrane stability in orchardgrass (Dactylis glomerata)

1993 ◽  
Vol 121 (2) ◽  
pp. 169-175 ◽  
Author(s):  
G. S. Premachandra ◽  
H. Saneoka ◽  
K. Fujita ◽  
S. Ogata
Keyword(s):  
Cell Membrane ◽  
Water Potential ◽  
Leaf Water Potential ◽  
Osmotic Potential ◽  
Seasonal Changes ◽  
Membrane Stability ◽  
Leaf Water ◽  
Leaf Water Relations ◽  
Cold Temperatures ◽  
Cell Membrane Stability

SUMMARYFifteen cultivars of orchardgrass (Dactylis glomerata L.) were grown in the field at Hiroshima University, Japan, to investigate seasonal changes in leaf water relations and cell membrane stability (CMS) measured by the polyethylene glycol (PEG) test. Leaf water potential and osmotic potential were measured from August 1988 to August 1989. Solute concentration in leaf cell sap was also estimated.Cell membrane stability increased, leaf water potential and osmotic potential decreased and turgor potential increased with decreasing environmental temperatures during autumn and winter. The significant increases observed in CMS may enable plants to tolerate freezing temperatures during winter. Decrease in leaf water potential may be a result of water-deficit effects due to soil freezing at low temperatures and the decrease in osmotic potential may help plants to maintain turgor and tolerate freezing conditions. Plants maintained higher turgor as the osmotic potential decreased to values as low as – 3·98 MPa during winter; the maintenance of turgor helps to maintain water uptake under water deficit conditions at low temperatures.Sugar and K were the major osmotic contributors in orchardgrass leaves. Sugar and Ca concentrations increased and Mg and P concentrations decreased at cold temperatures. K concentration increased in six cultivars and decreased in nine others at cold temperatures. Sugar concentration in cell sap was negatively correlated with osmotic potential. It was concluded that seasonal changes in CMS may be mainly associated with the osmotic potential of the leaf tissues.

Osmotic Adjustment, Induced by Drought, in Seedlings of Three Eucalyptus Species

1986 ◽  
Vol 13 (5) ◽  
pp. 597 ◽  
Author(s):  
BA Myers ◽  
TF Neales
Keyword(s):  
Water Potential ◽  
Osmotic Adjustment ◽  
Osmotic Potential ◽  
Dry Weight ◽  
Eucalyptus Species ◽  
Plant Water ◽  
Mature Trees ◽  
Mean Values ◽  
Turgor Maintenance ◽  
Plant Water Potential

Osmotic adjustment was observed in pot-grown seedlings of Eucalyptus behriana, E. microcarpa and E. polyanthemos that had been subjected to one and two periods of drought. The osmotic potential of sap expressed from rehydrated leaves was significantly lower in seedlings which had wilted twice (-2.02 � 0.05 MPa) compared with those which had wilted once (-1.86 � 0.05 MPa) and those which had been watered daily (-1.66 � 0.05 MPa). After two drought cycles, seedlings began to wilt at lower mean values of plant water potential (- 3.51 � 0.22 MPa) than those which had not wilted previously (-3.14 � 0.22 MPa). Thus drought-induced osmotic adjustment apparently enhanced turgor maintenance. The ratio of turgid weight to dry weight was slightly, but significantly, smaller in the seedlings subjected to two drought cycles (3.83 � 0.04 MPa) compared with those subjected to one drought cycle (4.05 � 0.04). The osmotic adjustment that was induced by two drought cycles in these seedlings was about one third of the observed seasonal osmotic adjustment in mature trees of E. behriana and E. microcarpa in the field.

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