Vegetation change in the grasslands and grassy woodlands of east-central Cape York Peninsula, Australia

1998 ◽  
Vol 4 (2) ◽  
pp. 132 ◽  
Author(s):  
Gabriel M. Crowley ◽  
Stephen T. Garnett
Keyword(s):  
Vegetation Change ◽  
Perennial Grass ◽  
Aerial Photographs ◽  
Management Tool ◽  
East Central ◽  
Themeda Triandra ◽  
Species Dominance ◽  
Heteropogon Contortus ◽  
European Settlement ◽  
Cape York

The vegetation of 64 grassland and grassy woodland sites in east-central Cape York Peninsula, surveyed by CSIRO in 1966, was re-surveyed in 1995. While the original vegetation communities had persisted at most sites, a change in species dominance was recorded at 14% of sites. Melaleuca viridiflora (ti-tree) had invaded eight sites, and increased in abundance in at least 16 of the 35 sites in which it had occurred in 1966. This had led to four out of 13 grassland sites, and three out of four mixed evergreen sites being re-classified as ti-tree woodlands. Analysis of aerial photographs covering 415 km2 showed a 10% net loss of grasslands between 1969 and 1988. These changes are attributed to a reduction in the use of fire as a management tool since European settlement. Changes were also found in perennial grass composition consistent with grazing or over-grazing, particularly in the eucalypt/ironwood communities. A shift from Themeda triandra to Heteropogon contortus parallels earlier, grazing-related changes in southern Queensland. Evidence of a decline in Heteropogon triticeus and isolated losses of Sorghum plumosum are more suggestive of localized, unsustainable overgrazing. An increase in Sorghum plumosum in wet habitats appears to be associated with recent lack of burning. These changes suggest that further intensification of cattle grazing in the area may not be possible without significantly reducing both conservation values and pasture condition.

Native plant diversity in tropical savannas decreases when exotic pasture grass cover increases

2012 ◽  
Vol 34 (2) ◽  
pp. 183 ◽  
Author(s):  
A. S. Kutt ◽  
J. E. Kemp
Keyword(s):  
Species Richness ◽  
Plant Diversity ◽  
Native Species ◽  
Perennial Grass ◽  
Native Plant ◽  
Pasture Grass ◽  
Grazing Land ◽  
Themeda Triandra ◽  
Heteropogon Contortus ◽  
Native Plant Diversity

The invasion of exotic plants into savanna ecosystems can disrupt the natural pattern of vegetation. Indian couch Bothriochloa pertusa was introduced into Australia as a species for rehabilitation of degraded grazing land. In this study the effect of increasing B. pertusa cover on native plant diversity and possible mechanisms of its spread were examined. Forty sites were sampled in uncleared Queensland rangelands with a range of B. pertusa and Bothriochloa ewartiana (a native species) cover. The mean number of native species per quadrat declined with increasing B. pertusa cover but remained stable over sites with increasing B. ewartiana cover. Mean species richness accumulated at a significantly lower rate for sites with B. pertusa present. Canonical analysis of principle coordinates suggested that three groups of sites, ranging from low to high species richness and cover of native plants, were correlated along gradients of B. pertusa cover, grazing intensity and basal area of dead trees. Generalised linear modelling indicated significant negative relationships between B. pertusa cover and total ground cover, forbs and perennial grass richness and cover, and cover of nine native perennial tussock grasses (Aristida leptopoda, B. decipiens, B. ewartiana, Chrysopogon fallax, Dichanthium fecundum, D. sericeum, Heteropogon contortus, H. triticeus and Themeda triandra). This study suggests that an increase in B. pertusa is associated with a substantial change in the cover and species richness of native plant communities. This was considered to occur via competitive effects as well as a result of cattle grazing, rainfall deficit and tree death. Regardless of the mechanism, continued spread of exotic pasture species has the potential to cause significant changes to rangeland biodiversity.

Eighty years of change: vegetation in the montane ecoregion of Jasper National Park, Alberta, Canada

2002 ◽  
Vol 32 (11) ◽  
pp. 2010-2021 ◽  
Author(s):  
Jeanine M Rhemtulla ◽  
Ronald J Hall ◽  
Eric S Higgs ◽  
S Ellen Macdonald
Keyword(s):  
National Park ◽  
Vegetation Change ◽  
Fire Regime ◽  
Reference Conditions ◽  
Habitat Diversity ◽  
Climatic Conditions ◽  
Aerial Photographs ◽  
Contributing Factors ◽  
Jasper National Park ◽  
Closed Canopy

Repeat ground photographs (taken in 1915 and 1997) from a series of topographical survey stations and repeat aerial photographs (flown in 1949 and 1991) were analysed to assess changes in vegetation composition and distribution in the montane ecoregion of Jasper National Park, in the Rocky Mountains of Alberta, Canada. A quantitative approach for assessing relative vegetation change in repeat ground photographs was developed and tested. The results indicated a shift towards late-successional vegetation types and an increase in crown closure in coniferous stands. Grasslands, shrub, juvenile forest, and open forests decreased in extent, and closed-canopy forests became more prevalent. The majority of forest stands succeeded to dominance by coniferous species. Changes in vegetation patterns were likely largely attributable to shifts in the fire regime over the last century, although climatic conditions and human activity may also have been contributing factors. Implications of observed changes include decreased habitat diversity, increased possibility of insect outbreaks, and potential for future high-intensity fire events. Results of the study increase knowledge of historical reference conditions and may help to establish restoration goals for the montane ecoregion of the park.

Effects of moisture supply in the dry season and subsequent defoliation on persistence of the savanna grasses Themeda triandra, Heteropogon contortus and Panicum maximum

1992 ◽  
Vol 43 (2) ◽  
pp. 241 ◽  
Author(s):  
JJ Mott ◽  
MM Ludlow ◽  
JH Richards ◽  
AD Parsons
Keyword(s):  
Growing Season ◽  
Close Correlation ◽  
Dry Season ◽  
Carbon Gain ◽  
Panicum Maximum ◽  
Wet Season ◽  
Themeda Triandra ◽  
Heteropogon Contortus ◽  
Moisture Conditions ◽  
Sheath Material

The close correlation between grazing-induced mortality and major climatic patterns in Australian savannas, led us to the hypothesis that moisture conditions during the dry, non-growing season could affect sensitivity to grazing in the subsequent growing season. Using three widespread savanna species (Themeda triandra, Heteropogon contortus and Panicum maximum), this hypothesis was tested experimentally and the mechanisms controlling this response examined and quantified. In T. triandra drought during the dry season led to major mortality in defoliated plants in the next growing season. This mortality was caused by a synchrony of tillering at the commencement of the wet season, leaving few buds for replacement once parent tillers were killed by defoliation. T. triandra was also the most sensitive species to defoliation. This sensitivity was due to the poor ability of the plant to maintain positive carbon gain after defoliation. Several factors contributed to this poor ability, including: low total photosynthetic rate, low specific leaf area, and a large proportion of sheath material with poor photosynthetic capacity remaining after cutting. Both H. contortus and P. maximum growing under irrigated and fertilized conditions did not display any effects of previous moisture treatments when defoliated during the next wet season and were much less sensitive to defoliation than T. triandra.

Growth, seed production and effect of defoliation in an early flowering perennial grass, Alloteropsis semialata (Poaceae), on Cape York Peninsula, Australia

2001 ◽  
Vol 49 (6) ◽  
pp. 735 ◽  
Author(s):  
Gabriel M. Crowley ◽  
Stephen T. Garnett
Keyword(s):  
Plant Growth ◽  
Seed Production ◽  
Perennial Grass ◽  
Soil Surface ◽  
Plant Size ◽  
Perennial Grasses ◽  
Wet Season ◽  
Cape York ◽  
Seed Dynamics

Alloteropsis semialata (R.Br.) A.Hitchc. is one of the first perennial grasses in monsoonal Australia to produce seed at the start of the wet season. Patterns of growth and seed production and seed dynamics of Alloteropsis semialata were examined in this study, along with the effects of partial defoliation. Growth of Alloteropsis semialata tussocks started with the first pre-wet-season rains, and was then interrupted during a period with little rain. Growth ceased before the end of the wet season, indicating that factors other than moisture availability were limiting. Seeds of Alloteropsis semialata were germinable on production, but did not remain viable or persist on the soil surface through the dry season. Most seeds and young seedlings were harvested and no seedlings were recruited. Inflorescence production increased with plant size. Moderate defoliation in the early wet season had no impact on plant growth, but reduced inflorescence and seed production for at least 2 years. Absence of a seed bank and early wet-season flowering mean that Alloteropsis semialata is likely to be sensitive to long-term over-grazing.

Challenging the concept of Aboriginal mosaic fire practices in the Lake Eyre Basin

2015 ◽  
Vol 37 (6) ◽  
pp. 623 ◽  
Author(s):  
R. G. Kimber ◽  
M. H. Friedel
Keyword(s):  
Aboriginal People ◽  
Fire Hazard ◽  
Management Tool ◽  
Desert Region ◽  
Fuel Loads ◽  
European Settlement ◽  
Natural Landscapes ◽  
Large Fires ◽  
Feral Animals ◽  
Simpson Desert

Mosaic burning is the deliberate creation of a mosaic of patches representing different fire histories. It is often recommended for management of Australia’s natural landscapes, on the assumption that it enhances biodiversity and reduces fire hazard through increased spatial and temporal diversity of fuel loads and species composition. It is also suggested that such fire practices were used throughout Australia by traditionally living Aboriginal people. Although the creation of a patchwork of different fire histories may be an effective management tool in modern land management, the evidence for universal mosaic burning before European settlement deserves scrutiny. The records of explorers, early settlers and anthropologists relating to a large portion of the Lake Eyre Basin, particularly the Channel country and the Simpson Desert region, were examined. It is concluded that extensive gaps in the records of smokes and large fires are important and meaningful, and do not represent a failure to record fires. The case for universal mosaic burning in the region is not supported by the evidence although mosaic burning did occur in specific circumstances. Fire practices were shaped by complex and interacting factors including the vegetation and terrain type, for example the occurrence of spinifex-dominated sandhills or stony deserts; seasonal conditions and the presence or not of adequate fuel loads; how readily Aboriginal people could access country and their reasons for using or not using fire; the stocking of the pastoral country and spread of feral animals; and government policies about fire.

Assessing techniques for estimating the extent of mangroves: topographic maps, aerial photographs and Landsat TM images

2001 ◽  
Vol 52 (5) ◽  
pp. 787 ◽  
Author(s):  
F. J. Manson ◽  
N. R. Loneragan ◽  
I. M. McLeod ◽  
R. A. Kenyon
Keyword(s):  
Thematic Mapper ◽  
Aerial Photographs ◽  
Landsat Thematic Mapper ◽  
Pixel Resolution ◽  
Topographic Data ◽  
Linear Extent ◽  
Cape York ◽  
Ground Truthing ◽  
Remote Sensing Techniques ◽  
Thematic Mapper Imagery

Coastal habitats are critical to the sustained production of many fisheries. It is important, therefore, that fishery managers obtain accurate estimates of the extent of these habitats. This study investigated three methods of estimating the linear extent and area of mangroves (commercially available topographic data, aerial photographs and Landsat Thematic Mapper satellite imagery) in two regions in northern Australia: the Joseph Bonaparte Gulf (in particular, the Berkeley and Lyne Rivers) with typically narrow fringes of mangroves (<50 m wide), and the Embley River on Cape York Peninsula,with much broader mangrove stands (50–1000 m wide). Ground-truthing verified that aerial photographs provided the most accurate estimates of extents of mangroves in all rivers,because of their high spatial resolution (2 m). Landsat Thematic Mapper imagery gave good estimates of the area of habitats, but, because of the 30 m pixel resolution, it underestimated the linear extent in places where the mangrove fringe was narrow. Topographic data gave good estimates of the extent of mangroves where the forests were more extensive and less linear in shape, but were very poor otherwise at this scale. These findings have implications for the use of remote sensing techniques in ecological studies in these regions.

Fire regime and vegetation change in the transition from Aboriginal to European land management in a Tasmanian eucalypt savanna

2016 ◽  
Vol 64 (5) ◽  
pp. 427 ◽  
Author(s):  
Louise M. Romanin ◽  
Feli Hopf ◽  
Simon G. Haberle ◽  
David M. J. S. Bowman
Keyword(s):  
Vegetation Change ◽  
Fire Regime ◽  
Plantago Lanceolata ◽  
Sediment Cores ◽  
Open Water ◽  
Fire Regimes ◽  
Ecological Impacts ◽  
14C Dating ◽  
Early 19Th Century ◽  
European Settlement

Using pollen and charcoal analysis we examined how vegetation and fire regimes have changed over the last 600 years in the Midlands of Tasmania. Sediment cores from seven lagoons were sampled, with a chronology developed at one site (Diprose Lagoon) using 210Pb and 14C dating. Statistical contrasts of six cores where Pinus served as a marker of European settlement in the early 19th Century and showed significant changes in pollen composition following settlement with (a) influx of ruderal exotic taxa including Plantago lanceolata L., Brassicaceae, Asteraceae (Liguliflorae) and Rumex, (b) increase in pollen of the aquatics Myriophyllum spp. and Cyperaceae, (c) a decline in native herbaceous pollen taxa, including Chenopodiaceae and Asteraceae (Tubuliflorae) and (d) a decline in Allocasuarina and an initial decline and then increase of Poaceae. The presence of Asteraceae (Liguliflorae) in the pre-European period suggests that an important root vegetable Microseris lanceolata (Walp.) Sch.Bip. may have been abundant. Charcoal deposition was low in the pre-European period and significantly increased immediately after European arrival. Collectively, these changes suggest substantial ecological impacts following European settlement including cessation of Aboriginal traditions of fire management, a shift in hydrological conditions from open water lagoons to more ephemeral herb covered lagoons, and increased diversity of alien herbaceous species following pasture establishment.

Ruminal degradation characteristics of some African rangeland grasses

1995 ◽  
Vol 125 (2) ◽  
pp. 189-197 ◽  
Author(s):  
P. J. O'Reagain ◽  
B. C. Goetsch ◽  
R. N. Owen-Smith
Keyword(s):  
Cell Wall ◽  
Dry Matter ◽  
Agricultural Development ◽  
Cynodon Dactylon ◽  
Themeda Triandra ◽  
Heteropogon Contortus ◽  
Degradation Rates ◽  
Ruminal Degradation ◽  
The Mean ◽  
Species Being

SUMMARYThe seasonal rate and extent of dry matter (DM) and neutral detergent fibre (NDF) degradation of the African sourveld grasses Alloteropsis semialata, Andropogon appendiculatus, Cynodon dactylon, Elionurus muticus, Eragrostis plana, Harpochloa falx, Heteropogon contortus, Hyparrhenia hirta, Microchloa caffra, Themeda triandra and Tristachya leucothrix in the rumen were measured using the nylon bag technique at the Döhne Agricultural Development Institute, South Africa, in 1993. The size of the soluble fraction (SF) was markedly different (P < 0·05) between species, being largest in A. semialata (22·6%) and smallest in E. plana (13%). Over all species, the mean SF was highest (P < 0·01) in spring (21·6%) and lowest in winter (11·8%). Species differed (P < 0·05) in the size of the potentially digestible fraction (PDF), with H. contortus and T. leucothrix having the largest (71%) and M. caffra the smallest (53%) PDF. Mean PDF declined (P < 0·01) from spring (77·3%) through to winter (55·8 %). The rate of DM degradation (kd) in the rumen also differed (P < 0·01) between species, with C. dactylon and A. semialata having the fastest (0·054) and E. plana and A. appendiculatus the slowest (0·039) degradation rates. Mean kd values were lower (P < 0·05) in winter (0·039) than in the other seasons (0·048).Neutral detergent soluble (NDS) content was highest in A. semialata (29%) and lowest in E. plana (21·5%). Species similarly varied in the amount of potentially digestible cell wall (PDCW), with E. plana having the highest (57%) and C. dactylon the lowest (45·1%) PDCW content. Mean PDCW content was highest in spring (59·5 %) and lowest in winter (44·6%). Cell wall degradation (kc) rates were fastest (0·04) in C. dactylon and slowest in M. caffra (0·03). Overall, kc declined from spring (0·039) through to winter (0·029). In general, A. semialata, T. triandra and H. hirta appeared to have the most favourable, and E. plana, A. appendiculatusand M. caffra the least favourable, ruminal degradation characteristics. These differences suggest that species composition is likely to have a major impact on potential animal production on these low quality grasslands.

scholarly journals Suppression of annual grass weeds by AR542 endophyte infection in dryland tall fescue pastures

2007 ◽  
Vol 60 ◽  
pp. 164-167 ◽  
Author(s):  
K.N. Tozer ◽  
R.J. Lucas ◽  
G.R. Edwards
Keyword(s):  
Tall Fescue ◽  
Plant Competition ◽  
Perennial Grass ◽  
Subterranean Clover ◽  
Management Tool ◽  
Stocking Rate ◽  
Annual Grass ◽  
Endophyte Infection ◽  
Weed Cover ◽  
Grass Weed

The effect of endophyte infection of tall fescue (with and without AR542 endophyte Neotyphodium coenophialum) plant competition (white versus Caucasian clover with and without subterranean clover overdrilled) and spring stocking rate (10 versus 20 ewes/ha) on the population size of annual grass weeds was monitored in a pasture on dry stony soils in Canterbury Barley grass (Critesion murinum) cover and seedhead production were lower in AR542 than endophyte free pastures and where subterranean clover was overdrilled than where it was not Vulpia hair grass (Vulpia spp) seedhead production and cover were lower where subterranean clover was overdrilled and where Caucasian rather than white clover was sown Ewe stocking rate did not affect annual grass weed cover or seedhead density The results indicate that sowing tall fescue with AR542 endophyte may be a useful management tool to enhance growth of the perennial grass and reduce invasion of barley grass into dryland pastures

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