Germination and establishment of the weeds Sida acuta and Pennisetum pedicellatum in the Northern Territory

1980 ◽  
Vol 20 (105) ◽  
pp. 463 ◽  
Author(s):  
JJ Mott
Keyword(s):  
Northern Territory ◽  
Dry Season ◽  
Dormant Seed ◽  
Weed Species ◽  
Wet Season ◽  
Perennial Weed ◽  
Hard Seed ◽  
Sida Acuta ◽  
Seed Fall ◽  
Almost All

Two serious weed species in the Northern Territory are Sida acuta, a perennial weed of improved pastures, and Pennisetum pedicellatum, an annual grass that infests grain sorghum crops. In P. pedicellatum the customary successive ploughing carried out to kill seedlings in the early wet season may not give satisfactory control of the weed, while with S. acuta there appears to be a long-term dormant seed pool which can give rise to new generations of seedlings, Investigation into the germination requirements of the 2 species showed that both are dormant at seed fall and require high alternating temperatures to remove an after-ripening requirement. In addition S. acuta needs a further period at high temperature to fracture its impermeable seed coat. Almost all P. pedicellatum seed is non-dormant at the end of the dry season, but that of S. acuta still retains 30% hard seed after one dry season. In the field P. pedicellatum germinated faster than S. acuta, with 80% of the total wet season germination occurring with the first rain. In S. acuta germination was spread over the first 2 months of the season. Ploughing immediately after the break of the wet season killed seedlings of P. pedicellatum, but could bury viable dormant seed. Once buried, this store of dormant seed could remain viable and germinate when disturbed at crop planting. At the end of the wet season no viable seed of P. pedicellatum remained in the soil, but there could be a considerable amount of hard S. acuta seed. The results suggest that control of P. pedicellatum could be best accomplished by the use of minimum tillage procedures, with little ground disturbance to bury the seed, while oversowing with a vigorous perennial pasture species such as calopo (Calopognium mucunoides) could lead to suppression of S. acuta.

Thinking honeyeater: nectar maps for the Northern Territory, Australia

2000 ◽  
Vol 6 (1) ◽  
pp. 61 ◽  
Author(s):  
John C. Z. Woinarski ◽  
Greg Connors ◽  
Don C. Franklin
Keyword(s):  
Northern Territory ◽  
Dry Season ◽  
Spatial And Temporal Variation ◽  
Wet Season ◽  
Nectar Production ◽  
The World ◽  
Eucalypt Forests ◽  
The Times ◽  
Species Specific ◽  
Nectar Availability

We create monthly maps of nectar availability for the 1.4 x 106 km2 jurisdiction of the Northern Territory, Australia. These are based on a combination of vegetation mapping and a series of indices of plant species specific nectar scoring. The maps reveal complex spatial and temporal variation in nectar availability, but most notably a greater nectar resource in the monsoon-influenced north than in the arid south, and a peak in nectar availability in the dry season. The latter is associated with the extensive tropical eucalypt forests (especially those co-dominated by Eucalyptus miniata and E. tetrodonta). In contrast, wet season nectar availability in these forests is limited, but riparian and swampland forests, typically dominated by Melaleuca species, provide rich but spatially restricted nectar resources. The extensive and rich nectar resources available in eucalypt forests in the dry season supplement the diets of many species which are not primarily nectarivorous. This resource helps shape the singularity of northern Australian eucalypt forests relative to other extensive forests elsewhere in the world. Nectarivores remain in the system through a combination of movements across a number of scales, habitat shifting, and diet shifting. The latter is aided by the peaking of invertebrate and fruit resources at the times of minimum nectar production; a shuffling in resource availability brought about by the extreme climatic seasonality.

Fate of urea-nitrogen from cattle urine in a pasture-crop sequence in a seasonally dry tropical environment

1985 ◽  
Vol 36 (6) ◽  
pp. 809 ◽  
Author(s):  
I Vallis ◽  
DCI Peake ◽  
RK Jones ◽  
RL McCown
Keyword(s):  
Soil Depth ◽  
Soil Surface ◽  
Dry Season ◽  
Wet Season ◽  
Mineral N ◽  
Seasonally Dry ◽  
15N Urea ◽  
Almost All ◽  
Crop Sequence

The fate of urea-N in cattle urine applied during the dry season (in August) to the pasture phase of a pasture-crop sequence at Katherine, N.T., was investigated. Cattle urine labelled with 15N-urea was applied to three sets of microplots to measure the following parameters: (a) amount and distribution of 15N remaining in the microplots during the remainder of the dry season with 0, 0.5, 1.0 and 5.0 t ha-1 of pasture residues present initially; (b) the effect of placing the urine 5 cm below the soil surface on the amount of 15N remaining during the dry season; (c) uptake of 15N by the pasture during the early part of the wet season (October to December) and uptake by sorghum sown directly into the killed pasture in January. Residual 15N in the surface soil (0-15 cm) after the sorghum crop was also measured. Of the applied 15N, 26% was lost after 1 day, 32% after 7 days and 46% after 63 days. Losses were not affected by the amount of pasture residues on the microplots when the urine was applied. Almost all of the I5N remaining in the microplots was in the 0-7.5-cm layer of soil, and 65-75% of this was mineral N. The dry-season losses of 15N were presumably through volatilization of ammonia, because leaching was absent and no loss of 15N occurred when the urine was placed 5 cm below the soil surface. Pasture growth killed at the end of December contained 6.2% of the applied 15N, the sorghum crop recovered only a further 2.1%, and after harvest of the sorghum crop the 0-15.0-cm layer of soil contained 23%. Thus about half of the 15N remaining in the soil-plant system to the 15.0 cm soil depth at the end of the dry season disappeared during the following wet season, either as a gaseous loss or by leaching deeper into the soil.

Fire and survival of Stylosanthes spp. in the dry savanna woodlands of the Northern Territory

1982 ◽  
Vol 33 (2) ◽  
pp. 203 ◽  
Author(s):  
JJ Mott
Keyword(s):  
Dry Matter ◽  
Northern Territory ◽  
The Other ◽  
Dry Matter Yield ◽  
Stocking Rate ◽  
Wet Season ◽  
Native Grass ◽  
Hard Seed ◽  
Stylosanthes Humilis ◽  
Good Germination

A series of burns was carried out during the early and late, dry season and early wet season, in mixed native grass-legume plots containing Stylosanthes humilis, S. hamata, S, scabra and S. viscosa as the legume component. The least mortality was shown by S. scabra, but its survival was poor in any sward more than 3 years old. After burning the other species relied solely on seedling regeneration for subsequent season's growth. Fire killed a considerable quantity of seed, but its heat softened hard seed in the soil and good germination occurred with summer rains. However, the presence of a large proportion of soft seed through the winter months could lead to out-of-season germination and subsequent death of seedlings after unseasonal winter rains. Although the total dry matter yield of swards was reduced by all fires, burning could play an important part in increasing yields of S. hamata in swards overgrown by dense native grass, since it increases the amount of soft seed in the soil. If burning causes a high mortality of mature plants of the perennials S. scabra and S. viscosa, a reduction in stocking rate may be needed to ensure regeneration of a productive sward, as these species have slow seedling growth rates.

Distribution and Abundance of Ducks in the Alligator Rivers Region, Northern Territory

1990 ◽  
Vol 17 (6) ◽  
pp. 573 ◽  
Author(s):  
SR Morton ◽  
KG Brennan ◽  
MD Armstrong
Keyword(s):  
Northern Territory ◽  
Dry Season ◽  
Correction Factors ◽  
The South ◽  
Wet Season ◽  
Aerial Surveys ◽  
Black Duck

Aerial surveys between 1981 and 1984 were used to identify monthly trends in the abundance of wandering whistling-duck Dendrocygna arcuata, plumed whistling-duck D. eytoni, radjah shelduck Tadorna radjah, Pacific black duck Anas superciliosa, and grey teal A. gibberifrons on five floodplains of the Alligator Rivers region, 250 km east of Darwin in the monsoonal north of the Northern Territory. Ground surveys were conducted during the same period on one of the floodplains, the Magela plain, to provide more detailed information. The Magela floodplain was inhabited by few ducks during the wet season (November to March), but numbers then increased to dramatic peaks in the late dry season. The Nourlangie floodplain and Boggy Plain (a large backswamp of the South Alligator floodplain) showed similar patterns, but the numbers of ducks were usually fewer. Ducks were uncommon on the shallower East Alligator and Cooper floodplains except for relatively brief periods in the wet season. The ground surveys suggested that ducks sought out the persistent swamps that characterise the Magela floodplain in the dry season. Ground surveys also indicated that aerial surveys underestimated densities; on the basis of correction factors calculated from the ground surveys, peak numbers on the five floodplains were roughly estimated to be 400 000 wandering whistling-ducks, 70 000 plumed whistling-ducks, 20 000 radjah shelducks, 50 000 Pacific black ducks, and 50 000 grey teal. Pink-eared ducks Malacorhynchus membranaceus and hardhead Aythya australis were recorded sporadically in low numbers. The Alligator Rivers region acted as a dry season refuge for large concentrations of ducks because of the atypical persistence of freshwaters on the Magela and Nourlangie floodplains and some of the backswamps of the South Alligator, such as Boggy Plain. The large aggregations appear to be unique in Australia.

Reproduction in the northern brown bandicoot (Isoodon macrourus) in the Australian Wet Tropics

2009 ◽  
Vol 57 (2) ◽  
pp. 105 ◽  
Author(s):  
Karl Vernes ◽  
Lisa Claire Pope
Keyword(s):  
Environmental Factors ◽  
Wild Population ◽  
Dry Season ◽  
Adult Males ◽  
Wet Season ◽  
Timing Of Reproduction ◽  
Adult Females ◽  
Wet Tropics ◽  
Almost All ◽  
The Tropics

We investigated timing of reproduction in a wild population of northern brown bandicoots (Isoodon macrourus) in the Australian Wet Tropics. Almost all births occurred during the late dry season and early wet season, and most adult females (78–96%) were carrying pouch young during those times. Litter sizes ranged from 1 to 6 pouch young (mean = 3.1) and was not influenced by season. Adult males had significantly larger testes in the late dry and early wet seasons, corresponding with the peak in births. Daylength was the only environmental factor that predicted the presence of a litter; when daylength exceeded 12 h, more than 70% of captured females were carrying pouch young, and most (94%) births were estimated to have occurred on days with >12 h of daylight. Various environmental factors have been proposed as a cue for breeding in I. macrourus, with daylength though to be the primary cue initiating breeding in temperate Australia, but temperature and rainfall thought to be more important in the tropics. Our data suggest that in the Australian Wet Tropics, increasing daylength in the late dry season acts as the primary cue for breeding.

scholarly journals Dry season and soil texture affect the chemical control of monocotyledonous in sugarcane

2018 ◽  
Vol 8 (3) ◽  
pp. 477-485
Author(s):  
Hudson Kagueyama Takano ◽  
Denis Fernando Biffe ◽  
Jamil Constantin ◽  
Rubem Silvério de Oliveira Junior ◽  
Guilherme Braga Pereira Braz ◽  
...  
Keyword(s):  
Soil Texture ◽  
Rainy Season ◽  
Clayey Soil ◽  
Dry Season ◽  
Weed Species ◽  
Wet Season ◽  
Sugarcane Crop ◽  
Dry Conditions ◽  
Loam Soil ◽  
Great Complexity

The chemical weed control in sugarcane during the wet season is more effective than the control carried out during the dry season. The objective of this study was to evaluate the efficacy of herbicides in the rainy season and in the dry season in sugarcane crop, and in different soil textural classes. The experiments simulated dry season and rainy season basing on periods of days in which experiment was submitted to irrigation restriction. In each experiment, it was tested 50 and 100% of the dose of the main herbicides commonly used in sugarcane to control B. decumbens, B. plantaginea, P. maximum and D. horizontalis. In general, in dry conditions, as well as varying the soil texture, there are restrictions in the choice of herbicide to be used due to the reduced effectiveness of some treatments in certain situations. In the very-clayey soil, especially in the dry season, the efficacy of herbicides is better, whereas, for the sandy-clay-loam soil in dry conditions, the effectiveness of herbicides is restricted. Thus, this study, despite the great complexity of the variables to be analyzed, permitted to establish guidelines for decision making on the most appropriate herbicide to be applied in each studied condition, in order to control these weed species.

scholarly journals Non-structural carbohydrates mediate seasonal water stress across Amazon forests

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Caroline Signori-Müller ◽  
Rafael S. Oliveira ◽  
Fernanda de Vasconcellos Barros ◽  
Julia Valentim Tavares ◽  
Martin Gilpin ◽  
...  
Keyword(s):  
Water Stress ◽  
Tree Species ◽  
Tree Mortality ◽  
Soluble Sugar ◽  
Dry Season ◽  
Future Climate Change ◽  
Wet Season ◽  
Dry Conditions ◽  
Almost All

AbstractNon-structural carbohydrates (NSC) are major substrates for plant metabolism and have been implicated in mediating drought-induced tree mortality. Despite their significance, NSC dynamics in tropical forests remain little studied. We present leaf and branch NSC data for 82 Amazon canopy tree species in six sites spanning a broad precipitation gradient. During the wet season, total NSC (NSCT) concentrations in both organs were remarkably similar across communities. However, NSCT and its soluble sugar (SS) and starch components varied much more across sites during the dry season. Notably, the proportion of leaf NSCT in the form of SS (SS:NSCT) increased greatly in the dry season in almost all species in the driest sites, implying an important role of SS in mediating water stress in these sites. This adjustment of leaf NSC balance was not observed in tree species less-adapted to water deficit, even under exceptionally dry conditions. Thus, leaf carbon metabolism may help to explain floristic sorting across water availability gradients in Amazonia and enable better prediction of forest responses to future climate change.

Seasonal use of savanna landscapes by the Gouldian finch, Erythrura gouldiae, in the Yinberrie Hills area, Northern Territory

2001 ◽  
Vol 28 (4) ◽  
pp. 445 ◽  
Author(s):  
P. L. Dostine ◽  
G. C. Johnson ◽  
D. C. Franklin ◽  
Y. Zhang ◽  
C. Hempel
Keyword(s):  
Full Range ◽  
Northern Territory ◽  
Dry Season ◽  
Perennial Grasses ◽  
Grass Species ◽  
Wet Season ◽  
Themeda Triandra ◽  
Annual Grasses ◽  
Gouldian Finch ◽  
Hills Area

The diet, attributes of feeding sites and patterns of seasonal movements of a population of the Gouldian finch, Erythrura gouldiae, were studied in the Yinberrie Hills area north of Katherine in the Northern Territory. In the dry season (April–November) Gouldian finches foraged mostly on burnt ground and fed on exposed seed of annual grasses, especially seed of spear-grass, Sorghum spp. In the wet season (December–March) Gouldian finches fed on seed of a sequence of perennial grass species, including Themeda triandra, Alloteropsis semialata, Chrysopogon fallax and Heteropogon triticeus. Gouldian finches undertake regular seasonal shifts in habitat, from breeding areas in hill woodland in the dry season to adjacent lowlands throughout much of the wet season, in response to seasonal changes in food availability. There is an annual pulse in abundance of fallen seed in the early dry season that is depleted to near zero levels by germination of annual grasses early in the wet season. Thereafter, finches depend on seed from other sources, principally ripe and ripening seed of perennial grasses. Observations over three successive wet seasons suggest that Gouldian finches track seed resources provided by seeding perennial grasses over an extensive area of lowland grassy woodland adjacent to the breeding area, favouring small patches of grassy woodland for brief periods until seed fall. There were subtle differences between years in the types of resources used. Management of Gouldian finch populations will entail protection and management of the full range of grassland habitats used throughout the annual cycle, and will require predictive knowledge of the causes of patterning of seed resources and probably an ability to exert control over the timing and extent of fires in fire-prone seasonal savanna landscapes.

Seasonal variations in the macroinvertebrate fauna of billabongs along Magela Creek, Northern Territory

1982 ◽  
Vol 33 (2) ◽  
pp. 329 ◽  
Author(s):  
R Marchant
Keyword(s):  
Seasonal Variations ◽  
Littoral Zone ◽  
Northern Territory ◽  
Dry Season ◽  
Wet Season ◽  
The Mean ◽  
Macroinvertebrate Fauna

The littoral zone of five permanent billabongs along Magela Creek was sampled monthly over 1 year for macroinvertebrates. In three shallow billabongs, greatest numbers of taxa (about 45) and of individuals (about 1000 individuals per minute) were caught in the late wet season and early dry season (April-July); by the end of the dry season (December) these values had decreased to about 18 taxa and about 200 individuals per minute. Fluctuations were not so marked in two deep (or channel) billabongs: rarely were there fewer than 30 taxa and 400 individuals per minute present, and maximal values were similar to those in the shallow billabongs. These changes appeared to be associated with the growth of macrophytes, which occurred during the wet season in all billabongs. There was little variation between billabongs in the mean composition of the fauna.

Distribution and abundance of herons, egrets, ibises and spoonbills in the Alligator Rivers Region, Northern Territory

1993 ◽  
Vol 20 (1) ◽  
pp. 23 ◽  
Author(s):  
SR Morton ◽  
KG Brennan ◽  
MD Armstrong
Keyword(s):  
Northern Territory ◽  
Dry Season ◽  
Correction Factors ◽  
The South ◽  
Wet Season ◽  
Fresh Waters ◽  
Aerial Surveys ◽  
Sacred Ibis ◽  
Egretta Garzetta

Aerial surveys between 1981 and 1984 were used to identify monthly trends in the abundance of Pacific herons (Ardea pacifica), pied herons (Ardea picata), cattle egrets (Ardeola ibis), great egrets (Egretta alba), little egrets (Egretta garzetta), intermediate egrets (Egretta intermedia), glossy ibis (Plegadis falcinellus), sacred ibis (Threskiornis aethiopica), straw-necked ibis (Threskiornis spinicollis) and royal spoonbills (Platalea regia) on five floodplains of the Alligator Rivers region, 250 km east of Darwin in the monsoonal Northern Territory. Ground surveys were conducted during the same period on one of the floodplains, the Magela. The aerial surveys indicated that the Magela floodplain was inhabited by few of these birds during the wet season (November-March), but that numbers then increased substantially in the dry season. The Nourlangie floodplain and Boggy Plain (a large backswamp of the South Alligator floodplain) showed similar patterns, but the numbers of birds tended to be lower. Birds were generally uncommon on the shallower East Alligator and Cooper floodplains, except for egrets in the wet season. Ground surveys suggested that the birds sought out the persistent swamps that characterise the Magela foodplain in the dry season. Ground surveys also indicated that aerial surveys underestimated densities. On the basis of correction factors calculated from ground surveys, peak numbers on the five floodplains were roughly estimated to be about 4000 pacific herons, 50 000 pied herons, 300 000 egrets (primarily intermediate egrets), 60 000 glossy ibis, 16 000 sacred ibis, 80 000 straw-necked ibis and 35 000 royal spoonbills. Great-billed herons (Ardea sumatrana), white-faced herons (Ardea novaehollandiae), striated herons (Butorides striata), rufous night herons (Nycticorax caledonicus), black bitterns (Dupetor flavicollis) and yellow-billed spoonbills (Platalea flavipes) were recorded sporadically in low numbers. The Alligator Rivers region acted as a dry-season refuge for herons, egrets, ibises and spoonbills because of the unusually persistent fresh waters of the Magela and Nourlangie floodplains and some of the backswamps of the South Alligator, such as Boggy Plain.

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