Effects of perennial species on the demography of annual grass weeds in pastures subject to seasonal drought and grazing

2009 ◽  
Vol 60 (11) ◽  
pp. 1088 ◽  
Author(s):  
K. N. Tozer ◽  
D. F. Chapman ◽  
R. D. Cousens ◽  
P. E. Quigley ◽  
P. M. Dowling ◽  
...  

A field experiment was established in a southern Australian temperate pasture to investigate the effects of identity and proximity of perennial grasses on the demography of the annual grasses Vulpia spp. (V. myuros, V. bromoides) and Hordeum leporinum (barley grass). Annual grasses were grown either alone or in mixtures, at different distances from rows of Dactylis glomerata (cocksfoot) and Phalaris aquatica (phalaris). Dactylis had a greater suppressive effect than Phalaris on Vulpia and Hordeum. Biomass, tiller production, and panicle production of annual grasses increased linearly with increasing distance from the perennial row. Tiller and panicle production were greater for Vulpia than Hordeum. The estimated rate of population growth (λ) for annual grasses was greater in Phalaris than in Dactylis and in Vulpia than in Hordeum, and increased with sowing distance from perennial grass rows. It was estimated that λ, when seeds were sown directly adjacent to a row of perennial grasses, was 1 and 0.4 for Vulpia and Hordeum, respectively, within Dactylis stands, and 7 and 3, respectively, within Phalaris stands. However, 15 cm from the row, λ reached 50 and 39 for Vulpia and Hordeum, respectively, within Phalaris stands, and 39 and 16, respectively, within Dactylis stands. In grazed, dryland pastures, perennial competition alone is therefore unlikely to prevent population growth of annual grasses, especially in systems heavily disturbed by grazing or drought. However, Dactylis showed more promise than Phalaris in limiting the abundance of these weeds.

2009 ◽  
Vol 62 ◽  
pp. 211-216 ◽  
Author(s):  
K.N. Tozer ◽  
T.K. James ◽  
C.A. Cameron

Yellow bristle grass (YBG) which is a summeractive annual grass reduces pasture quality and becomes unpalatable to stock as panicles mature Farmers are concerned that an extreme drought from November 2007 to March 2008 may have facilitated the spread of YBG and other summeractive annual grass weeds Botanical composition was assessed on 12 Waikato dairy farms in February 2009 and YBG abundance was related to key management factors These findings were compared with data collected from the same farms (February 2008) during the drought Between years ryegrass cover and the proportion of bare ground decreased These components were replaced by two summeractive annual grasses YBG and summer grass and to a lesser extent summeractive perennial grasses clovers and dicots In 2009 YBG cover was negatively associated with summeractive perennial grass cover and pH and positively associated with YBG cover in the previous summer and soil calcium levels


2016 ◽  
Vol 30 (1) ◽  
pp. 297-302 ◽  
Author(s):  
Christo Morris ◽  
Lesley R. Morris ◽  
Cheryl Surface

Downy brome has converted millions of hectares of Great Basin rangelands from shrubland to annual grass-dominated systems. Methods for removing downy brome from sites that already have perennial grasses established are especially needed because of the difficulty in re-establishing perennial species. In this study, early spring applications of glyphosate alone and glyphosate plus imazapic were monitored for 2 yr. Cover of downy brome was reduced from 45 to 10% by spring application of glyphosate alone and to approximately 1% with the addition of imazapic. Perennial grass cover was not affected by the spring application of glyphosate. The addition of imazapic reduced perennial grass cover in the first year; however, it recovered by the second year. The selective response to glyphosate may be due to differences in growth stage or dormancy characteristics between annual and perennial species. Our findings suggest spring application of glyphosate may provide an alternative approach for managing annual grasses on Great Basin rangelands.


2016 ◽  
Vol 16 ◽  
pp. 275-279
Author(s):  
E.J. Hall ◽  
R. Reid ◽  
B. Clark ◽  
R. Dent

In response to the need to find better adapted and more persistent perennial pasture plants for the dryland pastures in the cool-temperate low to medium rainfall (500-700 mm) regions, over 1000 accessions representing 24 species of perennial legumes and 64 species of perennial grasses, were introduced, characterised and evaluated for production and persistence under sheep grazing at sites throughout Tasmania. The work has identified four alternative legume species in Talish Clover (Trifolium tumens). Caucasian Clover (T. ambiguum), Stoloniferous Red Clover (T. pratense var. stoloniferum), Lucerne x Yellow Lucerne Hybrid (Medicago sativa x M.sativa subsp. falcata); and two grass species in Coloured Brome (Bromus coloratus) and Hispanic Cocksfoot (Dactylis glomerata var hispanica). Keywords: persistence, perennial grass, perennial legume


2014 ◽  
Vol 7 (2) ◽  
pp. 247-256 ◽  
Author(s):  
Kirk W. Davies ◽  
Dustin D. Johnson ◽  
Aleta M. Nafus

AbstractRestoration of exotic annual grass-invaded rangelands is needed to improve ecosystem function and services. Increasing plant species richness is generally believed to increase resistance to invasion and increase desired vegetation. However, the effects of species richness and individual plant life forms in seed mixes used to restore rangelands invaded by exotic annual grasses have not been investigated. We evaluated the effects of seeding different life forms and increasing species richness in seed mixes seeded after exotic annual grass control to restore desirable vegetation (perennial herbaceous vegetation) and limit exotic annual grasses at two sites in southeastern Oregon. We also investigated the effects of seeding two commonly used perennial grasses individually and together on plant community characteristics. Large perennial grasses, the dominant herbaceous plant life form, were the most important group to seed for increasing perennial herbaceous vegetation cover and density. We did not find evidence that greater seed mix species richness increased perennial herbaceous vegetation or decreased exotic annual grass dominance more than seeding only the dominant species. None of the seed mixes had a significant effect on exotic annual grass cover or density, but the lack of a measured effect may have been caused by low annual grass propagule pressure in the first couple of years after annual grass control and an unusually wet-cool spring in the third year post-seeding. Although our results suggest that seeding only the dominant plant life form will likely maximize plant community productivity and resistance to invasion in exotic annual grass-invaded northern Great Basin arid rangelands, seeding a species rich seed mix may have benefits to higher tropic levels and community stability. Clearly the dominant species are the most prudent to include in seed mixes to restore exotic annual grass-invaded plant communities, especially with finite resources and an increasingly large area in need of restoration.


2006 ◽  
Vol 54 (7) ◽  
pp. 655 ◽  
Author(s):  
Tanja I. Lenz ◽  
José M. Facelli

The species composition of temperate grasslands in the mid-north of South Australia has been radically altered from a system dominated by native perennial grasses to a system dominated by Mediterranean annual grasses. This study investigated the importance of chemical and physical soil characteristics, topographical features and climatic variables on the abundance of native and exotic grass species in nine ungrazed grasslands. Overall, climatic and other abiotic factors were highly variable. In addition, past management practices and original species composition are generally unknown, leading to further unexplained variation in the data. On a large spatial scale (among sites), the abundance of exotic annual grasses was positively correlated with mean annual rainfall, and on any scale, with finer soil textures and higher soil organic carbon levels. The most abundant annual grass, Avena barbata (Pott ex Link), was generally associated with soil factors denoting higher soil fertility. The abundance of native perennial grass species was not correlated with any environmental variables at any scale. The various native perennial grass species did not show clear associations with soil factors, although they tended to be associated with factors denoting lower soil fertility. However, at small spatial scales (within some sites) and among sites, the abundances of exotic annual and native perennial grasses were strongly negatively correlated. The results suggest that at the present time, rainfall and soil properties are important variables determining the abundance of annual grasses. The driving variables for the abundance of perennial grasses are less clear. They may be controlled by other factors or extreme rainfall events, which were not surveyed. In addition, they are likely to be controlled by competitive interactions with the annual grasses.


1994 ◽  
Vol 45 (5) ◽  
pp. 1077 ◽  
Author(s):  
AM Ridley ◽  
RJ Simpson

Studies in the field and in a rhizotron were conducted to examine the root growth of Phalaris aquatica L. (phalaris), Dactylis glomerata L. (cocksfoot) and Lolium rigidum Gaudin (annual ryegrass). Root and tiller development of the perennial grasses in autumn was also studied. In the field, annual ryegrass developed a more extensive surface rooting system than phalaris and cocksfoot by spring in a favourable season. Early root development of annual ryegrass was poor where the first rains of the season did not occur until winter. Growth rates of annual ryegrass roots at depth were similar to phalaris in mid spring in the rhizotron. Phalaris had a higher proportion of live roots than cocksfoot prior to the first autumn rain. Cocksfoot did not regenerate a substantial new root system until it developed secondary tillers, about a month after initial rains. Collectively, these studies indicated that the seasonal development and extent of the root systems of cocksfoot and phalaris were different.


1996 ◽  
Vol 18 (1) ◽  
pp. 3 ◽  
Author(s):  
VJ Anderson ◽  
KC Hodgkinson ◽  
AC Grice

This study examined the effects of previous grazing pressure, position in the landscape and apparent seed trapping capability of soil surface micro-sites on recruitment of the perennial grass Monachather paradoxa (mulga oats) in a semi-arid woodland. Seedling emergence was counted on small plots which had been kept moist for one month. The plots were on bare ground, or at grass tussocks, or at log mounds, sited in the run-off, interception and run-on zones of paddocks that had been grazed for six years at 0.3 and 0.8 sheep equivalent/ha. Few naturally occurring perennial grass seedlings emerged on any of the sites. The level of previous grazing pressure influenced the recruitment of grasses from natural sources as well as from seed of M. paradoxa broadcast on the soil surface; significantly more grass seedlings recruited in paddocks stocked at 0.3 than at 0.8 sheep/ha. Emergence of the sown grass did not differ significantly between the three zones in the landscape, but trends in the data suggest the interception zone may have been the most favourable. Recruitment from in situ grass seed was highest in the mulga grove (run-on) zone. Most seedlings of the sown grass emerged around the bases of existing perennial grass tussocks, but recruitment of volunteer perennial and annual grasses was more evenly distributed between the mulga log-mounds and perennial grass tussocks. It is concluded that very low levels of readily germinable seed of perennial grasses remained in the soil at the end of the drought and that areas with a history of high grazing pressure have less probability of grass recruitment when suitable rain occurs.


1963 ◽  
Vol 41 (8) ◽  
pp. 1171-1185 ◽  
Author(s):  
J. T. Slykhuis

Wheat striate mosaic virus from wheat in southeastern Saskatchewan was acquired and transmitted by both nymphs and adults of the leafhopper Endria inimica (Say) collected in Ontario. The preinfective period of leafhoppers varied from 4–6 to 22–24 days after they first fed on diseased plants. Records of serial transmission by individual insects varied greatly. Some insects infected most test plants on which they were given 2-day feeds during 20 to 30 days after the preinfective period, but subsequently they transmitted irregularly. Some transmitted virus for only a few days. Others transmitted intermittently for several weeks. None of the insects infected any plants on which they fed later than 72 days after feeding on diseased plants even though some lived another 10 to 20 days. Two of 25 insects became infective after feeds as short as 30 seconds on diseased plants, but the percentages of infective insects increased to more than 90% as acquisition access times were increased to 2 or more days. All insects from some inbred lines became infective after 3 days on diseased plants, but 45% of the descendants of one non-transmitting female failed to become infective. The inoculation threshold period on Ramsey wheat test plants was 15 minutes, but the percentage of test plants infected increased from 15% to 88.8% as the test access times were increased to 4 days. The incubation period of the virus in Ramsey wheat seedlings varied from 6 to more than 28 days.In tests of host reactions, all durum wheat varieties were highly susceptible to the virus. Several of the hard red spring and winter wheat varieties were highly susceptible and a few others were highly resistant or immune, but most were mildly to moderately susceptible. Most varieties of oats and barley and 10 species of wild annual grasses were moderately susceptible. Mild to moderate symptoms also developed on some of the plants in one or more varieties of Zea mays L., Lolium multiflorum Lam., L. perenne L., and Bromus inermis Leyss. Four varieties of rye tested did not develop symptoms, nor did any plants in 13 species of perennial grasses, including Chloris gayana Kunth, which is susceptible to the Australian wheat striate mosaic virus. E. inimica multiplied on wheat and 14 other annual and 21 perennial grass species, many of which are common on the prairies. There was considerable variation in the reactions to the virus of different plants in the variety Ramsey, but there were no inherent variations detected between the virus isolates used for the experiments. The wheat varieties Cappelle-Desprez and Rescue which are highly susceptible to the European type of wheat striate mosaic virus did not become infected with the Canadian isolates tested.Attempts to transmit the European type of wheat striate mosaic virus with E. inimica failed.


2010 ◽  
Vol 3 (1) ◽  
pp. 40-47 ◽  
Author(s):  
Sophie S. Parker ◽  
Joshua P. Schimel

AbstractAs Europeans colonized California, they introduced annual grasses from the Mediterranean Basin. These exotic annual grasses eventually invaded grasslands throughout the state, some of which were once dominated by native perennial grass species. Annual grasses differ from perennials in their phenology, longevity, rooting depth, litter chemistry, and interaction with the microbial community. As these traits may influence plant nitrogen (N) use, it is likely that the invasion by annual species resulted in changes in the availability and cycling of N in California grassland systems. We addressed the question of how invasive annual grasses influence rates of N cycling by measuring N pool sizes and rates of net and gross mineralization and nitrification, gross immobilization, and the denitrification potential of soils from experimentally planted annual and perennial-dominated grasslands. With an increase in annual grass cover, we saw increases in ammonium (NH4+) pool sizes and rates of N mineralization, nitrification, and denitrification in soils. These differences in N status suggest that N cycling in California grasslands was altered at sites where native perennial bunchgrasses were invaded by nonnative annual grasses. One consequence of annual grass invasion may be a legacy of NH4+-enriched soils that hinder the reestablishment of native perennial grass species.


1981 ◽  
Vol 29 (5) ◽  
pp. 533 ◽  
Author(s):  
DM Orr

Seasonal changes in the quantitative floristics at a wide range of Astrebla grassland sites in south-western Queensland were monitored between 1972 and 1980 with a wheel point apparatus. Changes in the floristics were measured in terms of both relative abundance and basal cover. A large increase in the relative abundance of perennial grasses, particularly Aristida latifolia, Astrebla spp. and Dichanthium sericeum, occurred between 1972 and 1976. This increase was at the expense of annual grasses and forbs which declined in both relative abundance and number of genera present. The relative abundance of perennial grasses declined between 1978 and 1980 and this was associated with a large increase in the forbs such as Daucus glochidiatus and Plantago spp., particularly at southern sites. The contribution of annual grasses to botanical composition remained low throughout the period. Total basal cover differed between years although these differences were not significant. As perennial grass, particularly Astrebla spp., was the major vegetation component of total basal cover, changes in the latter were associated mainly with changes in the basal cover of Astrebla spp. Changes in the contribution of individual species to total basal cover were related to changes in the relative abundance of those species. Changes in botanical composition in Astrebla grassland may be influenced more by trends in seasonal rainfall than by grazing pressure.


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