Tempo and mode of vegetation dynamics over 50 years in a New Zealand alpine cushion / tussock community

Abstract. Question: What are the tempo and mode of long‐term succession and of demographic processes in an alpine community, especially: tenacity, transition patterns, predictions, growth of individual cushion plants, cyclic succession, spatial patterns? Location: A low‐alpine mixed cushion /turf /snow‐tussock / shrub community in southeastern New Zealand. Methods: The distribution of seven plant cover‐types was recorded at 1024 fixed points in an 8 m × 8 m plot at approximately decade intervals for 50 years. The diameters of eight Donatia novae‐zelandiae cushions were monitored. Results: The process was essentially first‐order Markovian. There was a change in transition frequencies about 1980. The tenacity of the two major cover types — cushion and turf — was high, but that of cushion decreased about 1980 as some of its area was taken over by turf. The original informal prediction of 1955 that the cushion/turf would increase proved to be correct, probably because of paludification of the site. A prediction of 1987 made from observed transitions that cushion would dominate over turf has proved untrue because of a change in the transition probabilities in the 1980s, of unknown cause. There is a ten‐fold range in diameter growth rates among the eight cushions measured, but the mean rate of 5.3 mm.a^‐1 is similar to that reported from other alpine and arctic sites. As cushions aged, turf colonized their centres, and in two cases new cushions colonized into this turf: consistent with cyclic succession. The pattern of transitions was compatible with a general interpretation of cyclic succession, but not definitive. Conclusions: Change is slow in this alpine community, and tenacity high. The change in transition frequencies about 1980, the invasion of individual cushions, and the decrease in spatial autocorrelation all suggest that cushions established on the site as a result of the clearance of woody vegetation after 1400 AD. Paludification may be causing some loss of tussock grass. A tendency for the cushions to break up, and the shallow peat accumulated below them, may indicate that they are the first generation of cushions on the site. Though these cushions are breaking up, other cushions are establishing, and cushions will continue to be an important part of the vegetation dynamics which may be part of a cyclic succession.     

Succession in a New Zealand alpine cushion community: a Markovian model

A permanent plot in a low-alpine cushion/tussock/shrub community was mapped at ca. decade intervals from 1953 to 1984. Transition probabilities between vegetation types were calculated, and a Markovian model was fitted.In spite of non-stationarity a Markov model was consistent with the observations, and produced reasonable predictions, especially for the major components of the vegetation. The model predictions were conservative in terms of future changes, in that future changes would be smaller than those observed, but such predictions could be supported by independent evidence, such as the nature of the non-stationarity, plant counts and seedling numbers.The general pattern was of a decrease in the cover of both Chionochloa rigida tussocks and mixed turf, and an increase in the cover of cushion bog species, especially Donatia novae-zelandiae. Shrubs, the suggested climax, showed no tendency to increase. Known climatic changes cannot explain the trend, which therefore seems to be a local retrogressive succession. There may be a cycle of alternating cushion and turf.     

Application of palynology to describe vegetation succession in estuarine wetlands on Great Barrier Island,northern New Zealand

Question: This paper compares published palynological studies from coastal swamps containing the same suite of species. We ask the following questions: (1) does succession follow the same pathways in different swamp systems, or (2) at different times? If not, (3) how variable are the patterns and (4) what are the likely driving factors? Location: Great Barrier Island, Northern New Zealand. Methods: Eighteen pollen profile diagrams were studied from four estuarine wetlands, ranging from mangroves to swamp forest. Recognition of a transition between vegetation stages was by subjective consideration of the relative abundances of pollen of key indicator species at different depths in the sedimentary sequence. Results: A linear sequence of vegetation communities beginning with mangroves and followed by estuarine marsh communities composed of Juncus kraussii, Leptocarpus similis and Baumea juncea was recognised in almost all pollen diagrams. Further transitions, from Baumea to a terrestrial system of Leptospermum shrubland or Cordyline/Dacry‐carpus swamp forest, followed two main pathways associated with autogenic accumulation of peat and terrigenous sediment input respectively. At Kaitoke and Awana the marine/freshwater transition occurred before the arrival of humans on Great Barrier Island. At Whangapoua, increased sedimentation followed anthropogenic burning of adjacent forest, and this transition was faster and is still in progress. Conclusion: Palynology and current vegetation zonation patterns concur to demonstrate that the marine sedimentation phase of estuarine succession is predictable and linear. Baumea marks the transition to the freshwater phase, in which varied successional patterns are determined by interactions between hydrology, sediment input, and peat accumulation. Natural and human disturbances drive sedimentation rates, and interact with autogenic factors, to dictate vegetation transitions in these later stages. The intensive impact (mainly burning) during Polynesian times had a much greater effect on estuaries and swamps than the pre‐Polynesian natural processes, greatly accelerating plant succession.     

Two centuries of vegetation succession in an inland sand dune area,central Netherlands

Questions: (a) What are the rates and directions of vegetation succession in an inland sand‐dune system? (b) What are the differences in successional trajectories in different relief types? and (c) Is it possible to preserve the last areas of still active dunes and under what circumstances? Location: The study sites were located in the northern part of the Veluwe Region, central Netherlands; longitude 5°44′ E, latitude 52°20′ N, altitude 9 to 24 m a.s.l. Methods: Vegetation and relief mapping was conducted in three permanent plots, 200 m × 200 m in size, in 1988 and 2003. Phytosociological relevés (2400) were recorded in each 10 m × 10 m subplots. Age of woody species was determined by wood coring. Geographic Information System, ordination analyses, and TWINSPAN were used for data exploration and elaboration. Results: A total of 70 vascular plants and 19 bryophytes were recorded over successional stages spanning approximately190 years. The following dominant species formed the sequence of successional stages, but not all participated in all relief types: Ammophila arenaria, Festuca arenaria, Corynephorus canescens, Festuca ovina and Agrostis capillaris, and pine forest dominated in its herb layer at first by Deschampsia flexuosa and later by either Empetrum nigrum, Vaccinium myrtillus or Vaccinium vitis‐idaea. Conclusions: The successional trajectory is basically unidirectional for more than 100 years; no clear multiple successional pathways were observed, as is frequent in coastal dunes. Successional divergence was observed after approximately 130 years in the composition of the herb layer in the closed pine forest. The obvious vegetation heterogeneity in the still active sand‐blown area is related to differences in timing of vegetation establishment on particular relief types, thus the succession exhibits a terrain‐dependent asynchronous character. We conclude that the last patches of still‐active sand dunes can be preserved only by repeated strong artificial disturbances.     

干旱区高寒湿地逆行演替下土壤微生物群落结构的研究

【目的】探究高寒湿地逆行演替对土壤性质与微生物群落结构的影响。【方法】以新疆巴音布鲁克天鹅湖高寒湿地为研究对象,依托逆行演替典型样带(沼泽-沼泽化草甸-草甸),利用高通量测序技术分析各演替区土壤微生物群落结构。【结果】高寒湿地逆行演替改变了土壤微生物在分类操作单元(operational taxonomic unit,OTU)水平上的物种组成,致使草甸区的微生物ACE、Chao1、Simpson、Shannon多样性指数显著低于沼泽区和沼泽化草甸区(P<0.05);随着演替发生,变形菌门(Proteobacteria)、酸杆菌门(Acidobacteria)、拟杆菌门(Bacteroidetes)、子囊菌门(Ascomycota)的相对丰度均减少,放线菌门(Actinobacteria)、芽单胞菌门(Gemmatimonadetes)、担子菌门(Basidiomycota)、被孢霉门(Mortierellomycota)的相对丰度增加;主坐标法分析(principal coordinates analysis,PCoA)排序分析显示,土壤微生物群落在各逆行演替都出现不同程度的离散...     

Cold tolerance of New Zealand alpine insects

New Zealand has extensive alpine and subalpine habitats where, together with some lowland sites, insects are exposed to subzero temperatures. Studies of cold tolerance in New Zealand insects have centred on an alpine weta (Hemideina maori), which is the world's largest freezing tolerant insect, and an alpine cockroach (Celatoblatta quinquemaculata). Both of these insects are moderately freezing tolerant and have ice nucleating agents in their haemolymph and guts. There is some evidence for the survival of intracellular ice formation in the isolated gut tissue of C. quinquemaculata. Trehalose is a suggested cryoprotectant in both H. maori and C. quinquemaculata whilst proline also provides this role in H. maori. Cells and tissues of both insects maintain viability and physiological function during freezing to moderately low temperatures but viability declines at lower temperatures, the most vulnerable tissue presumably setting the limit to the survival of the animal. Antifreeze proteins are found in the gut tissue of C. quinquemaculata and may protect this tissue when freezing occurs in the gut. Several other New Zealand insects are also moderately freezing tolerant and the apparent dominance of this cold tolerance strategy in the New Zealand fauna may reflect the relatively mild climate but unpredictable exposure to subzero temperatures that is typical of many Southern Hemisphere environments.     

Selected temperatures of an alpine weta Hemideina maori from southern New Zealand

Abstract

We examined the relationship between thermal preference (selected body temperature or “T_sel") and microhabitat temperature of a nocturnal, alpine weta Hemideina maori (Orthoptera: Anostostomatidae), in the southern part of New Zealand. To examine diel variation in thermal preference, we measured T_sel five times over a 24‐h period in the laboratory and compared these temperatures to weta microhabitat temperatures in the wild. T_sel ranged from 4.3 to 29.3°C, but the distribution of temperatures was skewed, towards the cooler end of the thermal gradient, with an overall median and mean of c. 13°C. The frequency of T_sel values was bimodal, with peaks at a relatively narrow range of cool temperatures between 5 and 8°C (33%) and at a slightly broader range of warmer temperatures between 13 and 21 °C (52%). T_sel values did not vary with time of day, but differed significantly between individuals. Comparisons with microhabitat temperature showed that weta at 1250 m a.s.l. on the Rock and Pillar Range, Otago, had only limited opportunity to achieve T_sel and this was only possible during daylight hours, when weta are normally inactive.     

Floristic composition and macroenvironmental relationships of Tasmanian vegetation containing bolster plants

Communities containing bolster (hard cushion) plants are widespread in alpine and subalpine treeless plant communities in Tasmania. Numerical analysis of species presence/absence data from 227 quadrats defined thirteen communities, the distributions of which proved strongly related to a southwest to northeast edaphic gradient and altitude. The high altitude communities and those on oligotrophic soils are most likely to be dominated by bolster species, whereas the eastern communities are more frequently dominated by shrubs or graminoids.Nomenclature follows Curtis (1963, 1967), Curtis & Morris (1975), Curtis & Stones (1978) and Willis (1970) except where authorities are given at first mention. Structural nomenclature follows Kirkpatrick (1983).     

高寒牧区中华羊茅人工草地退化演替的数量特征研究

对中华羊茅人工草地退化演替数量特征的研究表明,植物群落组分种的数量、丰富度指数、多样性指数和均匀度指数均随演替的进程而增加,生态优势度指数呈下降趋势。对25个组分种的重要值、生态位宽度及生态位重叠值计测的结果表明,一些阔叶杂草（如细叶亚菊、西伯利亚蓼等）是退化演替过程中入侵人工草地的先锋植物,比其他杂类草具有较大的生态位宽度值,其重要值在演替过程中呈逐年上升趋势。以中华羊茅为其中一个组分种的植物种对间的生态位重叠值,在大多数情况下小于两种阔叶杂草种对间的生态位重叠值。阔叶杂草入侵是导致人工草地退化的一个重要影响因素。     

Restoration of alpine spoil heaps: Successional rates predict vegetation recovery in 50 years

Human disturbances in the alpine region can have long-lasting ecosystem effects because biological recovery in harsh environments proceeds slowly. As a by-product of the exploitation of hydroelectricity, surplus masses from tunnel excavations are deposited as spoil heaps in the alpine landscape. The typical management goal for such spoil heaps is that their species composition converges towards that of their undisturbed surroundings. At present we lack knowledge of the rate as well as the direction of these successions. We examined the species composition of five alpine spoil heaps in western Norway at two points in time, after 6-16, and 24-34 years of succession, with regard to vegetation cover, species richness, species composition and soil conditions. We also compared the vegetation of spoil heaps with that of their surroundings. After ca. 30 years, bryophyte and lichen cover and species richness were similar to those of their surroundings, while cover of vascular plants and species richness recovered more slowly. The vegetation development of spoil heaps appears safe-site limited rather than dispersal limited. Topsoil development was slow, but some accumulation of organic matter was observed. The species composition followed a successional trajectory in direction of the vegetation of the surroundings. Estimated linear successional rates indicate that 35-48 years are needed from construction of spoil heaps till a species composition more or less similar to their surroundings has been reached. However, these estimates are likely to be over-optimistic because successional rates tend to decrease with time. Based on our results we propose three changes to the current spoil-heap construction practice that will improve their restoration: (1) to increase surface unevenness, by which the number of safe sites will increase and germination and establishment success will be enhanced; (2) to increase substrate variability, by adding more of fine-grained materials more species will establish in shorter time; and (3) to use seed from local sources or to let the spoil heaps regenerate naturally.     

Seed bed treatment effects on vegetation and seedling establishment in a New Zealand pasture one year after seeding with native woody species

Summary Efforts to re‐establish indigenous forests in pastoral New Zealand have increased as the value of native biodiversity has been realized. Direct seeding of woody species is preferable to transplanting, as labour and material costs are less. However, the success rate of direct seeding in pasture has been variable due to intense competition from adventive species. We initiated an experiment in pasture plots adjacent to a forest fragment where seed bed treatments (increasing in degree of disturbance from herbicide application to turf removal and topsoil removal) in combination with mulch treatments (wood chip shavings with and without forest floor organic material) were seeded with a mixture of New Zealand lowland forest species. The objective of the study was to determine if early successional plant communities, and ultimately seedling establishment, differed as a result of seed bed preparation after 1 year. Coprosma robusta (Karamu) and Kunzea ericoides (Kanuka) seedlings established on plots in significant numbers: both species were most abundant on topsoil‐removed plots where bare substrate was greatest and plant cover least. Both seed bed treatments and mulching treatments led to measurable differences in overall composition of early successional plant communities. However, absence of plant cover and low soil fertility (both associated with the topsoil‐removed treatment) were the most important factors in seedling success.     

Disturbance‐induced changes in a high‐alpine cushionfield community,south‐central New Zealand

Long‐term effects of two nearby disturbances, mechanical blading 34 years ago and an approximately century‐old sheep graveyard, in high‐alpine cushionfield share certain vegetation features despite their contrasting soil nutrient status. Secondary succession following blading has continued beyond that recorded over the first 24 years with continued trends towards the adjacent undisturbed cushionfield: increased cover of several cushion species and the lichen Cetraria islandica ssp. antarctica. Several mid‐seral species remain prominent while bare soil and stone pavement continue to decrease. Additional shelter, facilitated by tall snow tussocks planted locally at near‐natural density on part of the bladed site, allowed establishment of some larger, thin‐leaved species. Soil factors remain little affected by the mechanical disturbance compared with the general enrichment persisting at the graveyard. Here three small indigenous grasses, which dominated 50 years earlier (Trisetum spicatum, Agrostis muelleriana, Poa colensoi), remain prominent among the relatively diverse community (50 species, including several calciphilic lichens on the degrading bones). By contrast, frequency of the cushionfield dominant, Dracophyllum muscoides and the lichen Alectoria nigricans, are negatively correlated with the presence of bones. The post‐disturbance temporal community changes are assessed in the context of the initial productivity of the habitat, competitive exclusion and the intermediate disturbance hypothesis.     

Dynamics of a Tasmanian bolster heath string fen

The string fen at Newdegate Pass, Mt. Field, Tasmania consists of dams composed of bolster heath and peat derived from bolster heath, and flark ponds with concave sides and usually rocky floors. The bolster heath has a smooth surface which consists of a complex mosaic dominated byDonatia novae-zelandiae, Carpha rodwayi andDracophyllum minimum. The floors of the ponds usually support no macrophytes. The ponds situated on strong flow lines have shallower dams which are more often breached than those where flow is more diffuse. The ponds ultimately drain by tunnelling through the humified peat below the live roots of the bolster heath, and the exposed floors are colonized by bolster heath species. The underlying block stream has a topography partly independent from that of the string and flark features, which shift in both time and space.Species nomenclature follows Curtis (1963, 1967) and Curtis & Morris (1975) for gymnosperms and dicotyledons and Willis (1970) for monocotyledons except where authorities are given. Structural nomenclature follows Kirkpatrick (1983).     

土壤-牧草氮素供需状况变化对高寒草甸植被演替与草地退化的影响

在中国科学院海北高寒草甸生态系统定位站 ,选取处于不同退化阶段的具有典型代表意义的草甸草场为研究对象 ,通过对其土壤氮素矿化补给能力、牧草对氮素的需求量的研究 ,探讨土壤 牧草氮素供需状况变化对高寒草甸植被演替与草地退化的影响。结果表明 ,在牧草生长季 5～ 8月 ,高寒草甸土壤的氮素矿化补给量为 15 86 g·m-2 ,而随着高寒草甸退化程度的加重 ,植物群落中优势种群由禾草演替为禾草 苔草 嵩草、嵩草至杂类草 ,其牧草生长需要的总氮量分别为 2 2 86、2 4 87、37 3、14 96g·m-2 ,只有在杂类草草甸阶段 ,其牧草生长对氮素的需求才与其土壤氮素供求相适配 ,可见养分是高寒草甸植被演替与草场退化的重要驱动因子之一。     

中国干旱半干旱区潜在植被演替

研究中国干旱半干旱区植被背景,成为其生态环境建设方面的基础性和指导性的工作。潜在植被作为一种与所处立地达到平衡的演替终态,反映的是无人类干扰的情况下,立地所能发育形成的最稳定成熟的一种顶极植被类型,是一个地区现状植被的发展趋势,对本地区植被生态的恢复和重建具有重要的指导意义。以综合顺序分类法为基本理论方法,在GIS研究方法支持下,采用中国干旱半干旱区119个气象观测站1961-2005年的年降水数据与115个气象观测站1961-2005的>0℃年积温数据,以15a的年平均数据为时间周期,对中国干旱半干旱区潜在植被的演替进行了分析,得出了以下结论:在中国干旱半干旱区,潜在植被类型之间发生了复杂的演替过程。1961-1975年间,分布在中国干旱半干旱区的潜在植被有10种类型,由于气候变化,到20世纪90年代后期仅剩6种类型。在潜在植被类型之间的转化特征与数量方面,表现出3种特点,稳定减少、稳定增加与波动性变化。在潜在植被类型地理分布格局变化与发展方向方面,演替明显的地区主要有:吐鲁番盆地、锡林郭勒高原北部、呼伦贝尔高原、太平岭地区;在发展方向上,潜在植被的空间变化方向(演替方向)均异。潜在植被类型演替的驱动因素主要是气候变化条件下,影响植被分布的水热条件发生了改变。     

The vegetation of a New Zealand dune slack

The vegetation of a dune slack at Mason Bay, Stewart Island, New Zealand was found to comprise a mosaic of communities. Although the broad vegetational patterns could be correlated with the depth of the water table, the patterns were far from simple. Species diversity over the whole slack was lower than values reported from European dune slacks; even the most diverse communities did not reach European mean values.For nomenclature see Wilson in press. Vascular plants of Stewart Island. D.S.I.R., Wellington, New Zealand; Sainsbury (1955). A handbook of the New Zealand mosses. N.Z. R. Soc. 5: 1–490 & Hamlin (1972). Hepaticae of New Zealand, Dominion Museum, Wellington.     

沙坡头人工固沙植被土壤水分空间异质性

利用传统统计学和地统计学相结合的方法对沙坡头人工固沙植被区0～200 cm 之间的各层土壤水分的空间变异性进行研究.结果表明,1）土壤水分相对变异较大的层是在160～180 cm层和180～200 cm层,变异系数分别为0.72和0.73.表层0～5 cm层的相对变异也较大,变异系数为0.662）半方差函数分析结果表明,各层土壤水分均具有明显的空间变异性,各层土壤水分自相关部分的空间异质性占总空间异质性的程度很高,所占比例在87.7%～99.9%范围内.各层土壤水分的有效变程大小有较大差异,最小值出现在60～80 cm层(7.04 m),最大值出现在20～40 cm层(19.71 m),土壤水分有效变程从表层到深层没有明显的变化规律;3）土壤水分插值图反映出0～140 cm之间相邻各层土壤水分变化较大,140～200 cm各层土壤水分变化较小;4）土壤水分在0°、45°、90°、135°四个方向的半方差函数基本上是一条直线,表明在这四个方向上半方差和距离的相关性较低,土壤水分变化是独立、随机的,是同质性的.     

The vegetation of roadside verges with respect to environmental gradients in southern New Zealand

Abstract. A survey of the vegetation of roadside verges was made across the southern part of the South Island of New Zealand. Samples were taken at 10-km intervals along selected roads providing a climatic range from the suboceanic conditions of the east coast into semi-arid Central Otago, and from Central Otago through the Southern Alps to the hyper-oceanic areas of high rainfall on the west Coast. The variation in the floristic composition is associated mainly with variation in rainfall, continentality, altitude, soil acidity, soil organic matter, and presence of forest. Sites in the arable and pastoral regions on the eastern side of the Southern Alps support a herbaceous vegetation consisting mostly of exotic species of European origin, with a few native grasses scattered through the drier and less fertile sites. A greater proportion of native species is found at higher altitudes. Roadside vegetation in the area of high rainfall to the west is characterized by indigenous ferns and woody species, although vegetation adjacent to cleared areas is more similar to that on roadsides adjacent to farmland on the east coast. The pattern of distribution of both native and exotic species is strongly related to altitudinal and climatic gradients, and the environmental responses of the exotic species are similar to those recorded in Europe. This suggests a colonization of all available sites by the exotic species, despite the relatively short time since their introduction to New Zealand, rather than an incomplete invasion.