Rank Grass Research Articles

Invasive alien species disrupt spatial and temporal ecology and threaten extinction in an insular, small mammal community

The impact of invasive bank vole (Myodes glareolus) and greater white-toothed shrew (Crocidura russula) on indigenous Irish small mammals, varies with season and habitat. We caught bank voles in deciduous woodland, young coniferous plantations and open habitats such as rank grass. The greater white-toothed shrew was absent from deciduous woods and plantations but did use open habitats with low level cover in addition to field margins. Numbers of both invasive species in field margins during summer were higher than in the previous spring. The indigenous wood mouse (Apodemus sylvaticus) and pygmy shrew (Sorex minutus), differed in degrees of negative response to invasive species. Wood mice with bank voles in hedgerows had reduced recruitment and lower peak abundance. This effect was less extreme where both invasive species were present. Wood mice numbers along field margins and open habitats were significantly depressed by the presence of the bank vole with no such effect in deciduous woodland or coniferous plantations. Summer recruitment in pygmy shrews was reduced in hedgerows with bank voles. Where greater white-toothed shrew was present, the pygmy shrew was entirely absent from field margins. Species replacement due to invasive small mammals is occurring in their major habitat i.e. field margins and open habitats where there is good ground cover. Pygmy shrew will probably disappear from these habitats throughout Ireland. Wood mice and possibly pygmy shrew may survive in deciduous woodland and conifer plantations. Mitigation of impacts of invasive species should include expansion of woodland in which native species can survive.

青海三江源区果洛藏族自治州草地退化成因分析

PDF HTML阅读 XML下载 导出引用 引用提醒 青海三江源区果洛藏族自治州草地退化成因分析 DOI: 10.5846/stxb201212201833 作者: 作者单位: 中国环境科学研究院,中国环境科学研究院,中国环境科学研究院 作者简介: 通讯作者: 中图分类号: 基金项目: 环保公益性行业科研专项项目(201209031) The cause of grassland degradation in Golog Tibetan Autonomous Prefecture in the Three Rivers Headwaters Region of Qinghai Province Author: Affiliation: Chinese Research Academy of Environmental Sciences,Chinese Research Academy of Environmental Sciences,Chinese Research Academy of Environmental Sciences Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:利用长期历史资料,分析了气候变化和人类放牧活动对草地生产力的影响,探讨20世纪60年代以来青海三江源区果洛藏族自治州草地退化主要原因,结果显示:研究区是全球变暖的敏感地区,1961-2010年研究区气温升高、年降水略有下降、湿润程度下降,Miami模型、Thornthwaite Memorial模型和综合自然植被净第一性生产力模型(综合模型)模拟的该区植被净初级生产力(NPP)均具有上升趋势,近50年来研究区气候变化总体上有利于该区草地生产力改善;研究区家畜年末存栏数60年代剧烈上升,至70年代达到顶峰,家畜年末存栏数与植被NDVI呈极显著负相关关系(P < 0.01),草地实际载畜量过大造成牲畜对草地过度啃食,导致草地退化。研究区退化草地恢复治理的重点应放在减轻载畜压力、控制草地现实载畜量方面。 Abstract:Grassland degradation was the deterioration of the grassland ecosystem function, such as structure, energy flow and material circulation, during its evolution process. This result is due to grassland coverage declining, yield of grass decrease and poison rank grass overgrowing, caused by human activities interference or adverse natural factors. Since the grim situation, the quality of grassland decline, Grassland productivity, economic potential and service function deteriorate, biodiversity complexity level descend, recovery function weaken or disappear, which threat region ecological security. Therefore, grassland degradation and its ecological impact have been an important research area of ecology. Located at the east of Tibet Plateau, the three rivers headwater region is the source region of Yangtze River, Yellow River and lancang River, and regard as the water tower of China. Under the influences of climate change and human activities,the grassland degradation presented a general situation in the Three Rivers Headwaters Region of Qinghai Province in last decades. Mainly located in the source region of Yellow River,the alpine meadow degradation and alpine steppe desertification were common phenomena. Grassland degradation was the result under joint action of long-term climate change and unreasonable grazing. By using long-term historical data,this paper investigated the cause of grassland degradation in the aspects of climate change effect and grazing influence to grassland productivity in Golog Tibetan Autonomous Prefecture since 1960s. The result showed that this region was sensitive to global warming. From 1961 to 2010,the annual average temperature ascending,annual precipitation slightly decreasing and moisture condition descending were the general trend. Nevertheless,the net primary productivity (NPP) was in the upward trend by the simulation of Miami Model,Thornthwaite Memorial Model and Synthetic Natural Vegetation Net Primary Productivity Model (Synthetic Model). The climate change improved the grassland productivity in generally. Hence,from macro point of view,climate change was not the cause of grassland degradation in the research area. The livestock amount at the end of year increased sharply in 1960s and reached the peak in 1970s. Large grassland current carrying capacity meant grassland overload and overgrazing. After that, the grassland deteriorated. The livestock amount at the end of year had extremely significant correlation (P < 0.01) with NDVI condition. Therefore,long-term grassland overload and overgrazing was the cause of grassland degradation. The key points of degraded grassland recover and governance were controlling grassland current carrying capacity and relieving grassland livestock carrying pressure. Since 2000,with the declining of grassland current carrying capacity,degraded grassland began to recover. 参考文献 相似文献 引证文献

Direct and Indirect Effects of Grazing by Introduced Mammals on a Native, Arboreal Gecko (Naultinus gemmeus)

We examined relationships between livestock grazing and the activity of introduced rodents and population density of Jewelled Geckos, Naultinus gemmeus (Diplodactylidae) on the Otago Peninsula, South Island, New Zealand. We expected livestock grazing to prevent the proliferation of rank grass (which is often associated with high rodent densities) and thereby reduce the frequency of predation by rodents on Jewelled Geckos. Thus, we predicted activity of rodents to be lower, and density of Jewelled Geckos higher, at sites grazed by livestock. We tested this for two habitats: Coprosma spp. shrubland and regenerating kānuka (Kunzea ericoides) forest. We quantified density of Jewelled Geckos using visual searches, photography and mark–recapture (POPAN formulation). We used tracking tunnel surveys to estimate the activity of introduced rodents. The activity of rodents (Rattus spp. and Mus musculus) was significantly higher at ungrazed compared to grazed sites in both habitats. Density of Jewelled Geckos in Coprosma was over four times higher at grazed sites and decreased with increasing rodent activity; however, in kānuka, we found a contrasting result with density being significantly higher at the ungrazed sites. We infer that in ungrazed Coprosma, rank grasses support high rodent densities and, consequently, high predation of Jewelled Geckos. Thus, grazing by introduced livestock may promote the survival of Jewelled Geckos and the persistence of high density populations in Coprosma shrubland. In contrast, grazing in regenerating kānuka may impact on Jewelled Geckos negatively, possibly by removing thermal refugia.

Is the Papuan Harrier Circus spilonotus spilothorax a globally threatened species? Ecology, climate change threats and first population estimates from Papua New Guinea

We undertook a 3-week expedition to Papua New Guinea in April-May 2007 to assess the breeding, threats and population densities of the Papuan Harrier Circus spilonotus spilothorax and to determine a first global population estimate for this almost entirely unknown species. Two of the first nests known were discovered in April 2007 with three chicks each, in the eastern lowlands, in rank grass and reeds. The melanistic form of this subspecies was more common in the lowlands (< 1,500 m a.s.l) than in the highlands, but interbreeding of this and the typical form occurred in the lowlands. Movements of identifiable individuals through two highland grasslands indicated up to eight birds per day on passage, corroborating local knowledge that other raptors move into the highlands at the start of the dry season (April). Linear road counts indicated no harriers in the wooded highlands but up to 2.9 harriers 10 km−1 in lowland grasslands. Area counts gave an average of 6.5 harriers 100 km−2 in the grasslands and a breeding density of 1.21 nests 100 km−2. Given that preferred grassland and swamp habitat comprises c. 7% of the forest-dominated island of New Guinea, the global Papuan Harrier population can be no more than c. 3,600 birds and c. 740 breeding pairs. Wildfires peaked at 38 per month in the study area, occur throughout the dry season, and led to the loss of both nests. This suggests that many nests and prey may be lost at critical times and burning may be ultimately detrimental for the species. Grassland fires throughout Indonesia and Papua New Guinea are increasing with climatic warming and ENSO events, so we suggest that the Papuan Harrier may warrant a ‘Vulnerable’ conservation ranking due to small total population size and an accelerated reduction in habitat quality due to ongoing climate change.

Relevance of Plant Functional Types based on Leaf Dry Matter Content for Assessing Digestibility of Native Grass Species and Species‐Rich Grassland Communities in Spring

Little research has been done on the nutritive value of species‐rich permanent grasslands in spite of their recognized ecological value. We proposed a new method based on the concept of plant functional type (PFT) to rank grass species and grasslands according to the organic matter digestibility (OMD) of the plant material. The PFTs are based on leaf dry matter content (LDMC). The objectives of this study were: (i) to see if there were significant differences between PFTs for the three components of plant OMD (leaf and stem digestibility and leaf proportion [L%]) in a set of 19 grasses growing in pure stand under two contrasting levels of N supply (Exp. 1); (ii) to see whether grassland vegetation types (GVT) differing in their PFT composition have different digestibility values; investigations being made on the leaf, stem, and whole plant OMD of five and eight plant communities (Exp. 2 and 3, respectively). In pure grass stands (Exp. 1) as well as in grassland communities (Exp. 2 and 3), there was a significant effect of PFT or GVT on leaf and stem OMD. The greatest differences in L% were observed when there were large differences in nutrient availability. At the leafy stage, the whole plant digestibility was higher for GVTs composed of PFTs with a low LDMC. However around the time of flowering there was a convergence in whole‐plant OMD between all grassland communities because L% decreased faster for those composed of PFTs having the lowest LDMC. At this stage, plots with low LDMC had higher plant component digestibility but lower L%. Our results show that the decrease in plant digestibility over time is the result of two processes, an ontogenic one, due to a decrease in leaf proportion, and an ageing one. For the latter, we show that PFT had an effect of leaf and stem digestibility at an early stage of plant development, then they decreased at a rate depending on plant development. Both processes explained the convergence between GVTs in plant digestibility at flowering time.

Soil nitrogen mineralisation changes rapidly when pine is planted into herbicide-treated pasture—the first two years of growth

The conversion of hill country pastures to exotic forest plantations has occurred rapidly in New Zealand over the last 10 years. This land-use change affects properties of the mineral soil, especially nitrogen (N) cycling. Here we studied the changes in soil in situ N mineralisation, in leaching, and microbial biomass, when Pinus radiata D. Don is planted into pasture; sheep were used to reduce pasture herbage before planting, and then herbicide was used to control the rank growth of grass around the trees. Total net N mineralisation in soil (0–100 mm) under pasture was 325 kg/ha.year. Net N mineralisation in the herbicide-treated areas was about double that under pasture or rank grass in the first 2 months. The concentration of nitrate-N in soil solution in the herbicide-treated areas was then 81 mg/L, compared with &lt;2 mg/L under pasture. During this time, the pH under the pine trees decreased very rapidly as nitrification increased. Soil nitrification and nitrate leaching were enhanced for 15 months after application of herbicide. After this 15-month period, soil total carbon (C) was slightly lower (P &lt; 0.10) under trees than rank grass, whereas microbial C and N were markedly lowest (P &lt; 0.05) under the trees. Over this period, about 18 kg N/ha was leached to 250 mm in the tree-planted area. The data also give additional insights into processes that occur when soil cores in buried bags are used to estimate N mineralisation.

Breeding biology of the Redwing Francolin in the highland grasslands of Mpumalanga Province, South Africa

We studied the breeding biology of the Redwing Francolin, Francolinus levaillantii, in the highland grasslands of Mpumalanga Province, South Africa, from 1995–1996. The breeding season is from August to March. Clutches were incubated by hens only and all nests were located in rank grass close to surface water. Mean clutch size was 4.3 eggs (S.D. = 0.78, n = 10) and mean egg dimensions were 40.1 × 32.3 mm (S.D. = 1.07 and 0.81, n = 44). Hatching success was 83.7% and clutch survival rate to 22 days of incubation was 82.8%. A mean of 3 chicks was produced per clutch; observed mean production (counts of hens with chicks) was 2.6 chicks per brood (n = 24 clutches; 62 chicks). The hunting season for Redwing Francolin in Mpumalanga should be from 15 April to 15 July.

Movements by stoats (Mustela erminea) and ferrets (M. furo) through rank grass of yellow‐eyed penguin (Megadyptes antipodes) breeding areas

Predation by introduced stoats (Mustela erminea) and ferrets (M. furo) may be contributing to the decline of yellow‐eyed penguins (Megadyptes antipodes) on the South Island of New Zealand. Areas of rank grass were established in the hope of reducing predation by physically excluding predators from penguin breeding areas. This paper describes a foot‐print tracking study which showed that stoats and ferrets were recorded twice and ten times respectively more often in rank grass than in grazed pasture. Stoats moved evenly throughout the rank grass, but ferrets restricted their movements to tracks through the rank grass. Ferrets approached penguin nests over 12 times more often than randomly selected sites in grazed pasture, particularly in spring when the penguin chicks are vulnerable to predation. Stoats appeared to avoid areas with high ferret abundance. Mice (Mus musculus)s, an important prey of these predators, were recorded 5–17 times more often in the ungrazed areas than in grazed areas. The concentration of stoats, ferrets and mice in the penguin breeding areas surrounded by rank grass increases the number of encounters between penguin chicks and predators, and so may increase rather than decrease the risk of predation of yellow‐eyed penguins and other ground nesting birds.

Effects of summer grazing and fertiliser on the clover content of hill country swards in the Gisborne region

Preliminary results are presented from an investigation to identify reasons for the low clover content of hill country pastures in the Gisborne-East Coast region. Four experiments were established near Gisbome. Treatments included: fertiliser versus no fertiliser; summer grazing versus no summer grazing; and clover cultivars (transpanted into swards). Summer rainfall had the major influence on the clover content of swards. With a reliable high summer rainfall the clover content averaged 16% of herbage. By contrast, with less reliable and lower summer rainfall, the clover content averaged 4-5% and subterranean clover was more important, Summer spelling of pasture, which allowed rank grass growth, reduced both white and subterranean clover content of swards. Fertiliser inputs increased the clover content of swards. Performance of cultivars was affected by grazing, differences between cultivars being greatest with summer grazing. The small-leaved cultivars of white clover ('Grasslands Tahora' and 'Whatawhata') initially performed better than larger-leaved cultivars at the high summer rainfall site, but failed to sustain any advantage. 'Tallarook' subterranean clover increased the clover content of swards with summer grazing. Keywords white clover, subterranean clover, East Coast, hill country, fertiliser, grazing management

Rediscovery of the Sooty Rail (Porzana tabuensis) in American Samoa

The Sooty Rail (Porzana tabuensis) is widely distributed in the Pacific, but in American Samoa has been found only on the island of Ta'i. This population was discovered in 1923 when 10 specimens were taken (Murphy 1924), but it has not been recorded since (Banks 1984). No Sooty Rails were found on Ta'ui during a survey conducted in 1975-1976 (Amerson et al. 1982: 64), and, as a result, it was believed to be extirpated (Muse and Muse 1982: 83). United States Fish and Wildlife Service biologists rediscovered this bird in 1985-1986, when they spent 8 days surveying birds on Ta'fu. On 27 June 1985 Engbring found a fresh, roadkilled Sooty Rail on a dirt side road about 1 km east of Ta'ii Village on the northwest side of the island. We heard or saw at least three more individuals in July 1986, all near the main road within 2 km of where the specimen was found. The birds were located by their soft but rather distinctive chattering calls. One was viewed briefly as it scooted across a small path, but only after we made considerable effort to flush it. The 1985 specimen was deposited at the Bernice P. Bishop Museum (BPBM 161855). Its external measurements (mm) were: tail, 39; wing chord, 74; exposed culmen, 16.9; and tarsus, 24.6. After comparing its plumage with other specimens in the collection, we determined the bird was an adult. The skull was fully ossified. The bird was crushed when killed, and it was impossible to determine the sex internally. Culmen and tarsus measurements, when compared with those of other P. tabuensis collected in Samoa (Amadon 1942), suggest it is a female. The short chord measurement indicates that the specimen belongs to the short-winged population, P. t. tabuensis, found in Tonga, Fiji, Niue, and Samoa (Banks 1984). Biologists with. the Whitney South Sea Expedition found the Sooty Rail on Ta'ui in marshy habitat on the northwest side of the island (Banks 1984). The rails that we found in 1985-1986 were also in the northwest portion of the island; they occupied rank grass and weed patches in semi-open agricultural forest. We did not find any marsh or reeds here, though there were densely vegetated swales where puddles formed after rains. The population of Sooty Rails on Ta'u has evidently never been large and may be confined to the northwest portion of the island. Residents of Ta'u did not recognize the bird we salvaged and thought it was a young Purple Swamphen (Porphyrio porphyrio), a relatively common and well-known bird on Ta'ui. The rails that we found were associated with habitat created by subsistence agriculture, an activity that has diminished over the last several decades on Ta'u. The decrease in subsistence agriculture, along with a possible loss of wetland habitat, probably has decreased Sooty Rail numbers on Ta'u. We thank staff from the Office of Marine and Wildlife Resources, American Samoa, especially R. Tulafono, B. Emsley, K. So'oto, and F. Niumata. U.S. Fish and Wildlife Service biologists who collected field data were C. Aguon, P. Ashman, and P. Pyle. M. LeCroy looked up museum numbers and remeasured specimens at the American Museum of Natural History. R. Banks and R. Clapp reviewed the manuscript.