scholarly journals Tree growth rates in north Australian savanna habitats: seasonal patterns and correlations with leaf attributes

2004 ◽  
Vol 52 (3) ◽  
pp. 303 ◽  
Author(s):  
L. D. Prior ◽  
D. Eamus ◽  
D. M. J. S. Bowman
Keyword(s):  
Growth Rates ◽  
Fire Regime ◽  
Leaf Mass Per Area ◽  
Northern Australia ◽  
Wet Season ◽  
Nitrogen And Phosphorus ◽  
Mature Trees ◽  
Open Forest ◽  
Eucalypt Woodland ◽  
Monsoon Rainforest

We demonstrate a significant relationship between leaf attributes and growth rates of mature trees under natural conditions in northern Australia, a pattern that has not been widely reported before in the literature. Increase in diameter at breast height (DBH) was measured every 3 months for 2 years for 21 tree species from four habitats near Darwin: Eucalyptus open forest, mixed eucalypt woodland, Melaleuca swamp and dry monsoon rainforest. Assimilation rates and foliar chlorophyll, nitrogen and phosphorus concentrations were positively correlated with growth rate and negatively correlated with leaf mass per area. For most species, increases in DBH were confined to the wet-season (summer) period between November and May. Average annual increases in DBH were larger in the dry monsoon rainforest (0.87 cm) and the Melaleuca swamp (0.65 cm) than in the woodland (0.20 cm) and the open forest (0.16 cm), and were larger in non-Myrtaceous species (0.53 cm) than in Myrtaceous species (0.25 cm). These results are discussed in relation to the frequent fire regime prevailing over much of northern Australia which causes the marked contrast between the small pockets of fire-tender closed monsoon rainforest and large expanses of fire-tolerant savanna.

The formation of degraded areas in the dry savanna woodlands of northern Australia

Soil Research ◽  
1983 ◽  
Vol 21 (1) ◽  
pp. 91 ◽  
Author(s):  
NK Bridge ◽  
JJ Mott ◽  
RJ Hartigan
Keyword(s):  
Hydraulic Conductivity ◽  
Organic Carbon ◽  
Surface Soil ◽  
Structural Rearrangement ◽  
Northern Australia ◽  
Wet Season ◽  
Structural Collapse ◽  
Tall Grass ◽  
Eucalypt Woodland ◽  
Almost All

The perennial tall grass understory of a eucalypt woodland on a commonly occurring red earth (Northcote Principal Profile Form Gn2.11) in northern Australia was burnt during the dry season and subjected to weekly clipping during the following two wet seasons to simulate overgrazing. Clipping killed many plants during the first wet season and almost all of them during the second. Infiltration measurements showed that sorptivity and hydraulic conductivity were greatly reduced after the first wet season following burning only, and micromorphological examination showed surface sealing and structural collapse. There was recovery of sorptivity after the second wet season, but not of hydraulic conductivity, and this was accompanied by an increase in the macropore space of the upper 5 mm of surface soil. With burning plus clipping, structural rearrangement formed a vesicular porous layer during the second wet season and infiltration rates remained low. Since no organic carbon was lost from the surface soil following burning only, the structural collapse was attributed to raindrop impact rather than loss of structural bonds in the oil. In the burn+clip treatment, organic carbon was lost only during the second wet season when most of the grass tussocks had died. Respiration measurements showed that there was little difference in biological activity between the burnt and unburnt grassland during the first wet season and that an estimated 600 g m-2 year-1 of carbon was respired. Overgrazing pastures on these soils results in complete degradation within two set seasons and the formation of bare areas with surface seals.

Phosphorus repletion of cattle previously exposed to dietary nitrogen and phosphorus deficiencies

1999 ◽  
Vol 50 (1) ◽  
pp. 93 ◽  
Author(s):  
G. Bortolussi ◽  
J. H. Ternouth ◽  
N. P. McMeniman
Keyword(s):  
Growth Rates ◽  
Barley Straw ◽  
Plasma Metabolites ◽  
Bone Thickness ◽  
Wet Season ◽  
Nitrogen And Phosphorus ◽  
Lower Growth ◽  
P Deficiency ◽  
Dietary Nitrogen ◽  
Significant Difference

This work reports the effects on growth and metabolic performance of steers fed 2 levels of phosphorus (P) during their repletion from a 15-week depletion period when they were fed diets containing various levels of nitrogen (N) and P. The repletion diets containing either 5·6 g P/day (marginal) or 8·3 g P/day (high) were fed to steers for a period of 12 weeks and were based on barley straw, molasses, sorghum grain, urea, and formaldehyde-treated gluten [mean dry matter (DM) digestibility of 0·62 and 14·6 g N/kg DM]. These repletion diets were formulated to simulate the dietary regimens of cattle grazing wet-season pastures in northern Australia and other tropical and subtropical regions. Food intake, liveweight gain, plasma metabolites, and P kinetics were measured. There was no significant difference between the repletion marginal- and high-P treatments in the mean liveweight (LW) gains and DM intakes (g/kg LW) of the steers. However, for both P treatments, the steers that had been fed a suboptimal level of N during depletion had marked increases (>60%) in feed intake throughout the repletion period. Within the marginal-P treatment, the growth rates of steers that had been fed a suboptimal level of N during depletion were higher than for those that had been fed higher N levels, and were similar to those of the high-P groups. Plasma inorganic P, bone thickness, and bone P concentration remained lower for the marginal-P treatment at the end of the repletion period. Furthermore, within the marginal-P treatment, steers that had been fed the high-N diet during depletion were unable to increase bone thickness and had lower growth rates than anticipated for the quality of the diet. Although N balance was positive and similar for both P treatments, the apparent P balance for the marginal-P treatment of 7·6 mg/kg LW was only about half that of the high-P treatment. It was concluded that the requirement for dietary P in steers that had been exposed to a dietary P deficiency, particularly when in association with high N, was higher than the 5·6 g/day provided.

The Ecophysiology of Allosyncarpia ternata (Myrtaceae) in Northern Australia: Tree Physiognomy, Leaf Characteristics and Assimilation at Contrasting Sites

1995 ◽  
Vol 43 (4) ◽  
pp. 367 ◽  
Author(s):  
IR Fordyce ◽  
GA Duff ◽  
D Eamus
Keyword(s):  
National Park ◽  
Light Flux ◽  
Dry Weight ◽  
Chlorophyll B ◽  
Northern Australia ◽  
Apparent Quantum Yield ◽  
Leaf Characteristics ◽  
Open Forest ◽  
Open Woodland ◽  
Monsoon Rainforest

Allosyncarpia ternata S.T.Blake, a large, evergreen tree endemic to the northern part of the Northern Territory, Australia, dominates the canopy in a wide variety of habitats, including monsoon rainforest on ravine floors, open forest and woodland on cliffs, screes and sandsheets, and open woodland on ridges and hilltops. This study examines tree physiognomy, leaf characteristics and leaf assimilation rates of A. ternata growing at sites with strongly contrasting micro-climates near Baroalba Springs, Kakadu National Park. By comparison with trees growing on the ravine floor, cliff and hilltop trees are generally shorter, they branch lower, are more frequently multi stemmed and have higher ratios of canopy width to height, while their leaves are generally smaller and thicker and contain less chlorophyll a and chlorophyll b per unit dry weight. They have lower mean specific leaf areas and higher mean stomatal densities. Assimilation measurements on leaves at a cliff site showed significantly higher rates of light-saturated assimilation during the morning than in the afternoon. On the ravine floor, by contrast, assimilation responses to changes in light flux density did not vary significantly through the day. Leaves of trees growing on the ravine floor had lower values oi light-saturated assimilation and light compensation point, and higher values of apparent quantum yield than cliffside leaves.

Vegetation of the Wessel and English Company Islands, North-eastern Arnhem Land, Northern Territory, Australia

2000 ◽  
Vol 48 (1) ◽  
pp. 115 ◽  
Author(s):  
J. C. Z. Woinarski ◽  
K. Brennan ◽  
I. Cowie ◽  
A. Fisher ◽  
P. K. Latz ◽  
...  
Keyword(s):  
Species Richness ◽  
Plant Species ◽  
Fire Regime ◽  
Plant Species Richness ◽  
Wet Season ◽  
Island Size ◽  
Open Forest ◽  
North Eastern ◽  
Arnhem Land

Vegetation patterning is described for two neighbouring continental island chains off Arnhem Land, Australia. A total of 684 species was recorded from 57 islands, with reasonably comprehensive lists for 36 of these islands. Almost 90% of the deviance in plant species richness was associated with island size. The richness of plants dispersed by sea and/or vertebrates was proportionally greater on small islands; that of relatively poor dispersers was greater on larger islands. Twelve vegetation communities were defined by classification of plant species composition in 226 50 × 50-m quadrats. There was no relationship between island size and species richness at the quadrat level, at least for the most extensive vegetation types. The vegetation of the islands is now composed of two main elements—an original set of communities (mostly of heath, tussock grassland and eucalypt open forest) whose species have poor inter-island dispersal, and a set of more recent colonists (mostly of strand, mangrove and coastal thicket communities). The former group is allied to the sandstone flora of western Arnhem Land, but is species-poor in comparison, as the islands lack the deep gorges which drive much of the species richness of western Arnhem Land. The latter group comprises many species with a broad geographic range across tropical coastal areas, including many species which have been shown elsewhere to be highly vagile. Many species of the former set appear to have been lost from the smaller islands. The island flora has been influenced by three sets of human managers. Aboriginal use of the islands has been long-standing and probably resulted in a fire regime which may have accentuated environmental patchiness. Centuries of wet-season use of some islands by Macassan trepang-harvesters, ending early this century, has apparently left few effects other than the persistence of occasional small populations of an introduced food tree. In contrast, European use of these islands has been minimal and fleeting, but is associated with the introduction of most weeds.

Occupancy of two forest specialist birds in the Southern Mistbelt Forests of KwaZulu-Natal and Eastern Cape, South Africa

2020 ◽  
pp. 1-16
Author(s):  
S. THOBEKA GUMEDE ◽  
DAVID A. EHLERS SMITH ◽  
YVETTE C. EHLERS SMITH ◽  
SAMUKELISIWE P. NGCOBO ◽  
MBALENHLE T. SOSIBO ◽  
...  
Keyword(s):  
South Africa ◽  
Camera Trap ◽  
Habitat Requirements ◽  
Stem Density ◽  
Grass Cover ◽  
Eastern Cape ◽  
Wet Season ◽  
Mature Trees ◽  
Natural Habitats ◽  
Kwazulu Natal

Summary Establishing the specific habitat requirements of forest specialists in fragmented natural habitats is vital for their conservation. We used camera-trap surveys and microhabitat-scale covariates to assess the habitat requirements, probability of occupancy and detection of two terrestrial forest specialist species, the Orange Ground-thrush Geokichla gurneyi and the Lemon Dove Aplopelia larvata during the breeding and non-breeding seasons of 2018–2019 in selected Southern Mistbelt Forests of KwaZulu-Natal and the Eastern Cape, South Africa. A series of camera-trap surveys over 21 days were conducted in conjunction with surveys of microhabitat structural covariates. During the wet season, percentage of leaf litter cover, short grass cover, short herb cover, tall herb cover and saplings 0–2 m, stem density of trees 6–10 m and trees 16–20 m were significant structural covariates for influencing Lemon Dove occupancy. In the dry season, stem density of 2–5 m and 10–15 m trees, percentage tall herb cover, short herb cover and 0–2 m saplings were significant covariates influencing Lemon Dove occupancy. Stem density of trees 2–5 m and 11–15 m, percentage of short grass cover and short herb cover were important site covariates influencing Orange Ground-thrush occupancy in the wet season. Our study highlighted the importance of a diverse habitat structure for both forest species. A high density of tall/mature trees was an essential microhabitat covariate, particularly for sufficient cover and food for these ground-dwelling birds. Avian forest specialists play a vital role in providing ecosystem services perpetuating forest habitat functioning. Conservation of the natural heterogeneity of their habitat is integral to management plans to prevent the decline of such species.

scholarly journals Evidence of Phosphate Mining and Agriculture Influence on Concentrations, Forms, and Ratios of Nitrogen and Phosphorus in a Florida River

Water ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1064
Author(s):  
Shuiwang Duan ◽  
Kamaljit Banger ◽  
Gurpal S. Toor
Keyword(s):  
Agricultural Land ◽  
Water Discharge ◽  
Mining Area ◽  
Specific Conductance ◽  
Organic N ◽  
Wet Season ◽  
Nitrogen And Phosphorus ◽  
Total N ◽  
Phosphate Mining ◽  
Molar Ratios

Florida has a long history of phosphate-mining, but less is known about how mining affects nutrient exports to coastal waters. Here, we investigated the transport of inorganic and organic forms of nitrogen (N) and phosphorus (P) over 23 sampling events during a wet season (June–September) in primary tributaries and mainstem of Alafia River that drains into the Tampa Bay Estuary. Results showed that a tributary draining the largest phosphate-mining area (South Prong) had less flashy peaks, and nutrients were more evenly exported relative to an adjacent tributary (North Prong), highlighting the effectiveness of the mining reclamation on stream hydrology. Tributaries draining > 10% phosphate-mining area had significantly higher specific conductance (SC), pH, dissolved reactive P (DRP), and total P (TP) than tributaries without phosphate-mining. Further, mean SC, pH, and particulate reactive P were positively correlated with the percent phosphate-mining area. As phosphate-mining occurred in the upper part of the watershed, the SC, pH, DRP, and TP concentrations increased downstream along the mainstem. For example, the upper watershed contributed 91% of TP compared to 59% water discharge to the Alafia River. In contrast to P, the highest concentrations of total N (TN), especially nitrate + nitrite (NOx–N) occurred in agricultural tributaries, where the mean NOx–N was positively correlated with the percent agricultural land. Dissolved organic N was dominant in all streamwaters and showed minor variability across sites. As a result of N depletion and P enrichment, the phosphate-mining tributaries had significantly lower molar ratios of TN:TP and NOx–N:DRP than other tributaries. Bi-weekly monitoring data showed consistent increases in SC and DRP and a decrease in NOx–N at the South Prong tributary (highest phosphate-mining area) throughout the wet season, and different responses of dissolved inorganic nutrients (negative) and particulate nutrients (positive) to water discharge. We conclude that (1) watersheds with active and reclaimed phosphate-mining and agriculture lands are important sources of streamwater P and N, respectively, and (2) elevated P inputs from the phosphate-mining areas altered the N:P ratios in streamwaters of the Alafia River.

Threats to monsoon rainforest habitat in northern Australia: The case of Ptychosperma bleeseri Burret (Arecaceae)

1993 ◽  
Vol 18 (4) ◽  
pp. 463-471 ◽  
Author(s):  
PIERS BARROW ◽  
GORDON DUFF ◽  
DAVE LIDDLE ◽  
JEREMY RUSSELL-SMITH
Keyword(s):  
Northern Australia ◽  
Monsoon Rainforest

scholarly journals Varied Diazotrophies, Morphologies, and Toxicities of Genetically Similar Isolates of Cylindrospermopsis raciborskii(Nostocales, Cyanophyceae) from Northern Australia

2001 ◽  
Vol 67 (4) ◽  
pp. 1839-1845 ◽  
Author(s):  
Martin L. Saker ◽  
Brett A. Neilan
Keyword(s):  
Nitrogen Source ◽  
Growth Rates ◽  
Vegetative Cell ◽  
Nitrogen Sources ◽  
Water Bodies ◽  
Cylindrospermopsis Raciborskii ◽  
Rrna Gene ◽  
Northern Australia ◽  
Fixed Nitrogen ◽  
Freeze Dried

ABSTRACT The potentially toxic freshwater cyanobacteriumCylindrospermopsis raciborskii has become increasingly prevalent in tropical and temperate water bodies worldwide. This paper investigates the effects of different nitrogen sources (NO3 −, NH4 +, and omission of a fixed form of nitrogen) on the growth rates, morphologies, and cylindrospermopsin (CYL) concentrations (expressed as a percentage of the freeze-dried weight) of seven C. raciborskii isolates obtained from a range of water bodies in northern Australia and grown in batch culture. In general, growth rates were lowest in the absence of a fixed-nitrogen source and highest with NH4 + as the nitrogen source. Conversely, the highest concentrations of CYL were recorded in cultures grown in the absence of a fixed-nitrogen source and the lowest were found in cultures supplied with NH4 +. Cultures supplied with NO3 − were intermediate with respect to both CYL concentration and growth rate. Different nitrogen sources resulted in significant differences in the morphology of C. raciborskii trichomes. Most notable were the loss of heterocysts and the tapering of end cells in cultures supplied with NH4 + and the statistically significant increase in vegetative cell length (nitrogen depleted < NO3 − < NH4 +). The morphological changes induced by different nitrogen sources were consistent for all isolates, despite measurable differences in vegetative-cell and heterocyst dimensions among isolates. Such induced morphological variation has implications forCylindrospermopsis taxonomy, given that distinctions between species are based on minor and overlapping differences in cell lengths and widths. The close phylogenetic association among all seven isolates was confirmed by the high level (>99.8%) of similarity of their 16S rRNA gene sequences. Another genetic technique, analysis of the HIP1 octameric-palindrome repeated sequence, showed greater heterogeneity among the isolates and appears to be a useful method for distinguishing among isolates of C. raciborskii.

Fire regimes and vegetation sensitivity analysis: an example from Bradshaw Station, monsoonal northern Australia

2003 ◽  
Vol 12 (4) ◽  
pp. 349 ◽  
Author(s):  
Cameron Yates ◽  
Jeremy Russell-Smith
Keyword(s):  
Fire History ◽  
Fire Regime ◽  
Landscape Scale ◽  
Fire Season ◽  
Individual Species ◽  
Northern Australia ◽  
Sensitive Species ◽  
Obligate Seeder ◽  
Return Interval ◽  
Noaa Avhrr

The fire-prone savannas of northern Australia comprise a matrix of mostly fire-resilient vegetation types, with embedded fire-sensitive species and communities particularly in rugged sandstone habitats. This paper addresses the assessment of fire-sensitivity at the landscape scale, drawing on detailed fire history and vegetation data assembled for one large property of 9100�km2, Bradshaw Station in the Top End of the Northern Territory, Australia. We describe (1) the contemporary fire regime for Bradshaw Station for a 10 year period; (2) the distribution and status of 'fire sensitive' vegetation; and (3) an assessment of fire-sensitivity at the landscape scale. Fire-sensitive species (FSS) were defined as obligate seeder species with minimum maturation periods of at least 3 years. The recent fire history for Bradshaw Station was derived from the interpretation of fine resolution Landsat MSS and Landsat TM imagery, supplemented with mapping from coarse resolution NOAA-AVHRR imagery where cloud had obstructed the use of Landsat images late in the fire season (typically October–November). Validation assessments of fire mapping accuracy were conducted in 1998 and 1999. On average 40% of Bradshaw burnt annually with about half of this, 22%, occurring after August (Late Dry Season LDS), and 65% of the property burnt 4 or more times, over the 10 year period; 89% of Bradshaw Station had a minimum fire return interval of less than 3 years in the study period. The derived fire seasonality, frequency and return interval data were assessed with respect to landscape units (landsystems). The largest landsystem, Pinkerton (51%, mostly sandstone) was burnt 41% on average, with about 70% burnt four times or more, over the 10 year period. Assessment of the fire-sensitivity of individual species was undertaken with reference to data assembled for 345 vegetation plots, herbarium records, and an aerial survey of the distribution of the long-lived obligate-seeder tree species Callitris intratropica. A unique list of 1310 plant species was attributed with regenerative characteristics (i.e. habit, perenniality, resprouting capability, time to seed maturation). The great majority of FSS species were restricted to rugged sandstone landforms. The approach has wider application for assessing landscape fire-sensitivity and associated landscape health in savanna landscapes in northern Australia, and elsewhere.

scholarly journals Growth, leaf and stomatal traits of crabwood (Carapa guianensis Aubl.) in central Amazonia

2012 ◽  
Vol 36 (1) ◽  
pp. 07-16 ◽  
Author(s):  
Miguel Angelo Branco Camargo ◽  
Ricardo Antonio Marenco
Keyword(s):  
Growth Rates ◽  
Stomatal Density ◽  
Leaf Gas Exchange ◽  
Carbon Assimilation ◽  
Leaf Traits ◽  
Leaf Thickness ◽  
Diurnal Changes ◽  
Wet Season ◽  
Carapa Guianensis ◽  
Rainfall Seasonality

Crabwood (Carapa guianensis Aubl.) is a fast growing tree species with many uses among Amazonian local communities. The main objective of this study was to assess the effect of seasonal rainfall pattern on growth rates, and seasonal and diurnal changes in leaf gas exchange and leaf water potential (ΨL) in crabwood. To assess the effect of rainfall seasonality on growth and physiological leaf traits an experiment was conducted in Manaus, AM (03º 05' 30" S, 59º 59' 35" S). In this experiment, six 6-m tall plants were used to assess photosynthetic traits and ΨL. In a second experiment the effect of growth irradiance on stomatal density (S D), size (S S) and leaf thickness was assessed in 0.8-m tall saplings. Stomatal conductance (g s) and light-saturated photosynthesis (Amax) were higher in the wet season, and between 09:00 and 15:00 h. However, no effect of rainfall seasonality was found on ΨL and potential photosynthesis (CO2-saturated). ΨL declined from -0.3 MPa early in the morning to -0.75 MPa after midday. It increased in the afternoon but did not reach full recovery at sunset. Growth rates of crabwood were high, and similar in both seasons (2 mm month-1). Leaf thickness and S D were 19% and 47% higher in sun than in shade plants, whereas the opposite was true for S S. We conclude that ΨL greatly affects carbon assimilation of crabwood by reducing g s at noon, although this effect is not reflected on growth rates indicating that other factors offset the effect of g s on Amax.

Sign in / Sign up

Export Citation Format

Share Document