Tall Tussock Research Articles

Floristic composition, biomass, and aboveground net plant production in grazed and protected sites in a mountain grassland of central Argentina

Changes in plant community composition, diversity, aboveground biomass, and aboveground net primary production (ANPP) of different plant growth-forms were assessed in sites protected from livestock grazing for 2, 4, and 15 years, and in a heavily-grazed site. Species richness was maximum at the grazed site and decreased significantly after 4 years of protection. Diversity decreased significantly only after 15 years of protection. No alien or weedy species were found at grazed or protected sites. Grazing exclusion produced a shift from grazing-tolerant or grazing-avoiding species with a graminoid or prostrate growth-form to taller species with a tall tussock growth-form. Grazing produced a 33% decrease in standing biomass but little change in ANPP when compared to the site protected from grazing for 2 years, but important changes in both biomass and ANPP respect to the sites protected for 4 and 15 years. Consumption was near 35% of ANPP.

Fog deposition in tall tussock grassland, South Island, New Zealand

Hill cloud microphysics was examined with a forward scattering spectrometer probe over tall tussock grassland at Swampy Summit near Dunedin, New Zealand. In a 4-month period, cloud water drop diameter spectra were obtained for 17 cloud–ground intersection events that varied from 1 to 61 h in duration. Rain fell in most events. Easterly conditions made up 60% of the events and had a median cloud drop diameter of 13.9 μm and 0.14 g m−3 liquid water content. For southwest winds, median drop diameter and liquid water content were significantly smaller at 9.8 μm and 0.05 g m−3.Aerodynamic conductance for momentum transfer, measured with a three-dimensional sonic anemometer, varied linearly with wind speed (R2=0.7) between 50 and 70 mm s−1 for wind speeds from 4 to 9 m s−1. Combining this relation with the cloud liquid water content measurements, cloud water deposition rates were estimated onto the 0.8-m-tall tussock canopy of one-sided leaf area index=3. These estimates were in the range 0.02–0.26 mm h−1 with a median of 0.05 mm h−1 which is the same as the median rate derived from the water balance of a large weighing lysimeter containing eight tussock plants. However, the water balance included a number of small quantities with determination of evaporation and rainfall being particularly difficult. Consequently, the lowest cloud water deposition rates for the water balance were sometimes negative. Nevertheless, even the maximum estimated rates incorporated into an annual calculation suggest cloud water deposition is unlikely to be a significant component of the water balance of a tall tussock grassland catchment. In the uplands of southern New Zealand, changing land use from tall tussock to pastoral agriculture with short vegetation is unlikely to alter streamflows via the cloud water deposition process.

Post-Fire Changes in Community Structure of Tall Tussock Grasslands: A Test of Alternative Models of Succession

Post-Fire Changes in Community Structure of Tall Tussock Grasslands: A Test of Alternative Models of Succession

North Island seral tussock grasslands 1. Origins and land-use history

Abstract A review of the history of seral tussock grasslands in the North Island reveals no evidence for their presence below treeline in pre-human times. Tussock grasses were confined to natural non-forest sites, which, below treeline, were dominated not by tussocks, but by low trees, shrubs, and, on oligo-trophic bogs, by Empodisma minus and Gleichenia dicarpa. Non-forest sites below treeline result from cold-air inversion, high water tables, and frequent geomorphic disturbance. Forest clearance by early Maori fires and subsequent recurrent burning of secondary vegetation induced 660 000 ha of seral tussock grassland in three areas of the central North Island: short tussock (Poa cita and Festuca novae-zelandiae) grasslands on the Volcanic Plateau surrounding Lake Taupo; tall tussock (Chionochloa rubra) grasslands on northern and eastern flanks of the Tongariro volcanoes; and tall tussock (Chionochloa rubra) on the Moawhango plateaus. The pattern of deforestation and spread of tussock grasses in a region of low economic value to Maori is correlated with extensive undulating topography at montane-subalpine altitudes, summer-dry climates in rain-shadow areas, and free-draining volcanic ash soils. Of the 660 000 ha in grassland in c. 1840, almost half (310 000 ha) had disappeared by c. 1940, and only 10% (64 000 ha) remains today, mostly in Moawhango Ecological District. Conservation status, reserve design, and the renewable resource value of the grasslands are discussed.

Species diversity and resource relationships of South Georgian fungi

The occurrence and distribution of the South Georgia fungal flora, particularly Ascomycotina and Basidiomycotina, is assessed in terms of habitat and substrate preference. The 113 taxa reported comprise 37 basidiomycetes, 49 ascomycetes, six myxomycetes and at least 21 lower fungi. Peat and litter substrata associated with tall tussock grassland have a rich macro-fungal flora, and numerous species occur in bog and mire communities, some in abundance from mid to late summer. Many micro-fungi and ascomycetes colonize dying leaves and inflorescences of specific vascular plants, and a few colonize bryophytes and lichens. At least a dozen species, probably non-indigenous, are associated with rotting timber and other imported materials at former whaling stations. An intensive survey of the South Georgia mycoflora is necessary to gain better understanding of their role in decomposition and nutrient cycling processes in the principal plant communities.

A study of the abundance and patchiness of cicada nymphs (Homoptera: Tibicinidae) in a New Zealand subalpine shrub-grassland

Abstract Cicada emergence skins in a subalpine shrub grassland have been sampled during 1969–75 to determine the abundance and spatial distributions of nymphs feeding on plant roots. A guild of six cicada species is primarily associated with two forms of vegetation: shrubs (Dracophyllum and Cassinia) and tall tussock (Chionochloa). Skin locations were mapped relative to dominant vegetation species, litter zones, and soil and rock pavements over a range of aspects, altitudes, and vegetation types, and sampling methods were scaled at four levels: the locality, plot, quadrat, and individual plant. There were significant differences in skin counts over four years, and different measures of mean skin densities are given for the four sampling scales. The two primary vegetation types had cumulative 1969–72 mean densities of 5.2 ± 4.0 and 12.9 ± 10.0 skins/quadrat (2.3 m2) , and the 1969–72 mean productivities of the upper 25% of quadrats (adjusted for percent ground cover) were, respectively, 5.5 and 35.5 skins/...

Survival of Seeds of Tropical Grassland Species Subjected to Bovine Digestion

The survival and digestion of seeds of 47 tropical and subtropical legume and grass species were studied by placing the seeds in nylon bags in the rumen of fistulated cattle, followed by acid-pepsin digestion, to identify any differences likely to affect dissemination by grazing cattle. Seeds of only four of the 23 grass species survived in appreciable numbers. Digestion for short periods actually increased germination of Digitaria ciliaris, Axonopus affinis and Paspalum notatum while seeds of Pennisetum clandestinum survived up to 10 days in the rumen. All four are creeping, sward-forming species adapted to heavy grazing. Few seeds of the tall tussock grasses survived the digestive processes. Survival of legume seeds was closely related to the hard seed content of the sample (...)

Fire, succession and reserve management in a New Zealand snow tussock grassland

The aftermath of fire was examined in a New Zealand grassland reserve, dominated by the tall tussock Chionochloa rigida. Deliberate fire has not previously been used in reserve management in New Zealand. Following an accidental fire in part of the reserve in autumn 1976, part of the remainder was deliberately burnt in the following spring for an experimental comparison. Vegetation changes were monitored until 1988. After both fires, the exotic grass Agrostis capillaris was abundant. Shoot frequency of Chionochloa rigida was low after fire due to the loss of the canopy, but generally increased. Twelve years after the fire, the vegetation was still different between areas of different burning history. In the unburnt area, the shrub Leptospermum scoparium was replacing Chionochloa. Species frequencies were used to classify the vegetation by Cluster Analysis. A transition matrix was calculated for the communities so derived, and a Markovian model used to predict future vegetation changes. Medium-term replacement of exotic grassland by native tussock grassland was predicted, with replacement by native Leptospermum scrub after several decades. Native forest species, some now present in small amounts, could eventually replace the Leptospermum. It is recommended that Chionochloa grassland at this altitude should be burnt every 15–40 years to maintain the community. Chionochloa rigida is expected to tolerate this regime. Burning would prevent loss of the tussock grassland by scrub invasion and consequential scrub fires. Such fires would probably result in the replacement of most native vegetation by aggressive exotic shrubs, or, if they were controlled, by exotic grassland.

RECENT CHANGES IN THE ALPINE GRASSLANDS OF THE WEST COAST

A full range of both tall and short snowgrass communities are present within the alpine grassland region of the West Coast; Many of the intertussock, fleshy herbs were removed with the initial grazing by wild animals, while the stature of many of the tall tussock communities was reduced with continual heavy grazing. Once major animal control operations were undertaken, a dramatic recovery in stature was recorded on the most favourable sites. This initial response could be very rapid as the tussocks required only a reduction in grazing pressure to attain their full stature.

Response of four species of chionochloa and two introduced grasses to soil amendment

Summary Four species of Chionochloa common in the pastoral sector of the tussock grasslands of South Island, New Zealand, were found to have diverging growth responses to lime and superphosphate when grown in a potted high country yellow-brown earth. The probable reasons for this divergence were considered with respect to nitrogen and phosphorus availability. The responses of these species were related to their pattern of occurrence in natural conditions. The comparative behaviour of two introduced grasses was also studied. It is inferred that tolerance of acid conditions, if not an actual preference for such conditions, may be an important factor in the distribution of some of these tall tussock species as well as in successful grass introduction.

GROWTH AND SEASONAL COMPOSITION OF NATURAL GRASSLAND IN ZAMBIA

There was a marked increase in basal cover of veld grasses after the first 2 to 3 years of cutting, and this effect continued over a period of 9 years. Short grasses, such as Cynodon dactylon and Heteropogon contortus, increased at the expense of tall tussock grasses, such as Hyparrhenia dissoluta.

Tussock grasslands in the Middle Rakaia Valley, Canterbury, New Zealand

Summary Phytosociological analyses are presented of the three major tussock grassland communities found today in the middle Rakaia valley: (1) snow-tussock grassland dominated by either the tall tussock Chionochloaoa flavencens or the tall tussock C. rigida. (2) red-tussock grassland where the taU tussock C. rubra is abundant and (3) fescue-tussock grassland where Festuca novae-zelandiae is characteristic. Floristic data are also presented for Bome severely degraded grassland communities. The zonation and history of these grasslands arc discussed, in particular the recent origin of fescue-tussock grassland from former tall-tussock communities.

Temperature and light micro-climate within a tall tussock community

Abstract Temperature and light measurements were made within a tall tussock community. They show the extent to which the maximum, minimum, mean, and range of temperatures are higher near the north (sunny) side of a tussock and decrease outwards towards the inter-tussock spaces and towards the southern (shady) side. The decrease in amount of light reaching the ground with increasing density of tussocks and with closer proximity to the tussock base is more marked on sunny than on cloudy days.