Application of QuickBird and aerial imagery to detect Pinus radiata in remnant vegetation

The invasion of Pinus radiata from long‐term established plantations is contributing to the degradation of fragmented and isolated remnants of native vegetation. Within the south‐east of South Australia, the 20 vegetation communities that occur within 500 m of a plantation edge are at risk, including nine state threatened communities. To plan effective mitigation strategies, the current extent and distribution of P. radiata needs to be ascertained. High spatial resolution, multispectral QuickBird imagery and aerial photography were used to classify P. radiata within eucalypt and acacia woodlands, melaleuca shrubland, modified pasture and an Eucalyptus globulus plantation. Unsupervised classification of aerial photography gave the best result showing reasonable conformity with the observed distribution of P. radiata at the site scale. However, the 9.4 ± 13.5 (SD) cover classified in the quadrats sampled for the accuracy assessment exceeded the 1.4 ± 2.4 (SD) P. radiata cover determined from an independent dataset. Only 30.1 ± 37.9% (SD) of trees within the quadrats and 9.40 ± 13.49% (SD) of their foliage cover were classified. Trees detected by partial classification of canopy were positively correlated with both tree height and canopy diameter. Overall, the low detection rates were attributed to insufficient spectral resolution. Using higher resolution imagery, together with an object‐based image analysis or combination of multispectral and airborne digital image classification, restricted to large emergent adult trees using LiDAR analysis, is likely to improve adult P. radiata detection accuracy.     

Aquatic and terrestrial vegetation of the Prespa area

We studied the vegetation of the aquatic ecosystems ofLake Mikri Prespa. The lacustrine vegetationcomprises three distinct forms: floating plants,benthic hydrophytes and helophytes, which aredescribed and classified from the phytosociologicalpoint of view, as follows: (a) the vegetation of thefloating plants belong to the Lemnetea class and isrepresented by two plant communities; (b) thevegetation of the benthic hydrophytes, belongs to thePotametea class consisting of two differentcategories, namely the submersed formations and theemergent formations of the hydrophytes. Various plantcommunities were recognised in this type of vegetationand three among them are considered as the mostrepresentative; (c) the vegetation of helophytes, theprevailing life form in this wetland, belongs to thePhragmitetea class and is represented mainly by sevenwell organised plant communities. The respectivevegetation of two of the five more important wetlandsites is described.The terrestrial vegetation is composed of forestand meadow vegetation. The forest vegetation of theNational Park belongs to the class Querco-Fagetea andshows the following zonation: (a) in the vicinity ofthe lake, at the elevation of 860–1000 m, twoassociations have been found: the mixed deciduous andevergreen forests of Ostryo-Carpinion orientalis andthe evergreen forests of Ostryo-Carpinion adriaticum;(b) the deciduous oak forests surround the previouszone at the altitude of 900–1300 m with two principalassociations, namely the Quercetum frainetto and theQuercetum petraeae; (c) in the upper forest layerbetween 1200–1800 m asl, dominate beech forests of theassociation Fagion moesiacum and the less extensiveoccurrence of the mixed beech-fir stands (Ass.Abieti-Fagetum moesiacum).The zone above the tree limit is distinguished by itssubalpine character semi-shrub vegetation extendinghigher than the forest (1800–2000 m), whereas alpine meadowscover the vegetation at higheraltitudes. On the plains and in the forest clearingsexist herbaceous meadow formations of variablestructure, in parallel with the vegetation of specifichabitats, such as nitrophilous and ammophilousplants.     

Assessing the future global impacts of ozone on vegetation

Ozone is a major secondary air pollutant, the current concentrations of which have been shown to have significant adverse effects on crop yields, forest growth and species composition. In North America and Europe, emissions of ozone precursors are decreasing but in other regions of the world, especially Asia, where much less is known about its impacts, they are increasing rapidly. There is also evidence of an increase in global background ozone concentrations, which will lead to significant changes in global ozone exposure over this century, during which direct and indirect effects of other changes in the global atmosphere will also modify plant responses to ozone. This paper considers how far our current understanding of the mechanisms of ozone impacts, and the tools currently used for ozone risk assessment, are capable of evaluating the consequences of these changing global patterns of exposure to ozone. Risk assessment based on relationships between external concentration and plant response is inadequate for these new challenges. New models linking stomatal flux, and detoxification and repair processes, to carbon assimilation and allocation provide a more mechanistic basis for future risk assessments. However, there are a range of more complex secondary effects of ozone that are not considered in current risk assessment, and there is an urgent need to develop more holistic approaches linking the effects of ozone, climate, and nutrient and water availability, on individual plants, species interactions and ecosystem function.     

Reconstructing pre-impact vegetation cover in modified landscapes using environmental modelling, historical surveys and remnant vegetation data: a case study in the Fleurieu Peninsula, South Australia

Aim To investigate the application of environmental modelling to reconstructive mapping of pre‐impact vegetation using historical survey records and remnant vegetation data. Location The higher elevation regions of the Fleurieu Peninsula region in South Australia were selected as a case study. The Fleurieu Peninsula is an area typical of many agricultural regions in temperate Australia that have undergone massive environmental transformation since European settlement. Around 9% of the present land cover is remnant vegetation and historical survey records from the ad 1880s exist. It is a region with strong gradients in climate and topography. Methods Records of pre‐impact vegetation distribution made in surveyors’ field notebooks were transcribed into a geographical information system and the spatial and classificatory accuracy of these records was assessed. Maps of remnant vegetation distribution were obtained. Analysis was undertaken to quantify the environmental domains of historical survey record and remnant vegetation data to selected meso‐scaled climatic parameters and topo‐scaled terrain‐related indices at a 20 m resolution. An exploratory analytical procedure was used to quantify the probability of occurrence of vegetation types in environmental domains. Probability models spatially extended to geographical space produce maps of the probability of occurrence of vegetation types. Individual probability maps were combined to produce a pre‐impact vegetation map of the region. Results Surveyors’ field notebook records provide reliable information that is accurately locatable to levels of resolution such that the vegetation data can be spatially correlated with environmental variables generated on 20 m resolution environmental data sets. Historical survey records of vegetation were weakly correlated with the topo‐scaled environmental variables but were correlated with meso‐scaled climate. Remnant vegetation records similarly not only correlated to climate but also displayed stronger relationships with the topo‐scaled environmental variables, particularly slope. Main conclusions A major conclusion of this study is that multiple sources of evidence are required to reconstruct past vegetation patterns in heavily transformed region. Neither the remnant vegetation data nor historical survey records provided adequate data sets on their own to reconstruct the pre‐impact vegetation of the Fleurieu Peninsula. Multiple sources of evidence provide the only means of assessing the environmental and historical representativeness of data sets. The spatial distribution of historical survey records was more environmentally representative than remnant vegetation data, which reflect biases due to land clearance. Historical survey records were also shown to be classificatory and spatially accurate, thus are suitable for quantitative spatial analyses. Analysis of different spatial vegetation data sets in an environmental modelling framework provided a rigorous means of assessing and comparing respective data sets as well as mapping their predicted distributions based on quantitative correlations. The method could be usefully applied to other regions where predictions of pre‐impact vegetation cover are required.     

The impacts of rising CO2 concentrations on Australian terrestrial species and ecosystems

The increasing atmospheric concentration of carbon dioxide ([CO₂]) contributes to global warming and the accompanying shifts in climate. However, [CO₂] itself has the potential to impact on Australia's terrestrial biodiversity, due to its importance in the photosynthetic process, which underlies all terrestrial food webs. Here, we review our knowledge regarding the impacts of elevated [CO₂] on native terrestrial species and ecosystems, and suggest key areas in which we have little information on this topic. Experimental information exists for 70 (or less than 0.05%) of Australia's native terrestrial plant and animal species. Of these, 68 are vascular plants. The growth of Australian woody species is more reliably increased by elevated [CO₂] than it is in grasses. At the species level, the most overwhelming responses to increased [CO₂] are a reduction in plant nitrogen concentration and an increase in the production of secondary metabolites. This is of particular concern for Australia's unique herbivorous and granivorous marsupials, for which no information is available. While many plant species also displayed increased growth rates at higher [CO₂], this was far from universal, indicating that changes in community structure and function are likely, leading to alterations of habitat quality. Future research should be directed to key knowledge gaps including the relationship between [CO₂], fire frequency and fire tolerance and the impacts of increasing [CO₂] for Australia's iconic browsing mammals. We also know virtually nothing of the impacts of the increasing [CO₂] on Australia's unique shrublands and semi‐arid/arid rangelands. In conclusion, there is sufficient information available to be certain that the increasing [CO₂] will affect Australia's native biodiversity. However, the information required to formulate predictions concerning the long‐term future of almost all organisms is far in excess of that currently available.     

准噶尔盆地植被与土壤盐渍化关联性变化趋势分析

准噶尔盆地作为北疆地区主要的气候单元其环境变化会影响北疆地区整体的的生态环境变化。植被作为衡量区域生态环境的重要指标直接反映了准噶尔盆地的生态状况,近年来受到全球气候变化的影响准噶尔盆地地区气候格局发生改变,盆地相比于往年降水和气温明显升高,这种改变影响了盆地的植被变化同时也会在部分地区诱发土壤盐渍化灾害。土壤盐渍化是我国西北地区常见的导致植被退化的因素,其生成原因与地形和气候因素有关。为了探究准噶尔盆地植被变化与土壤盐渍化的关联性,基于2002-2019年生长季MOD09A1遥感影像数据,利用最大值合成法、Mann-Kendall趋势分析,Hurst趋势分析法、相关性分析等方法对准噶尔盆地植被和土壤盐渍化变化趋势以及两者的关联性进行了分析。结果表明,受区域降水和气温升高的影响,近20年来准噶尔盆地生长季植被整体呈增加趋势,各季节增加区域面积占比为63.50%-90.93%,平均为77.98%。土壤盐渍化呈减少趋势,各季减少区域面积占比为46.50%-86.78%,平均为70.68%。在地形低洼、排水不畅的区域土壤盐渍化程度加重,植被因盐分胁迫导致衰退,植被减少及巨大的蒸发降水比使得该地区土壤进一步变干,湿度降低。关联性分析结果表明各季植被与土壤盐渍化的变化中呈显著负相关的区域面积占比为37.36%-57.83%,平均为51.75%。Hurst趋势预测结果表明,当前植被和土壤盐渍化两者呈显著性变化的区域未来预测与当前变化方向相同,两者呈一般性变化的区域未来预测与当前相反。研究有助于在全球气候变化背景下了解准噶尔盆地近年来生态环境变化,结果为区域生态环境的可持续发展提供参考。     

古尔班通古特沙漠西部地下水位和水质变化对植被的影响

通过对比分析古尔班通古特沙漠西部3a地下水位和水质的变化特点,研究了地下水位和水质变化对地表土壤理化性质、植物多样性、及建群种梭梭种群生长与更新的影响。发现地下水位和土壤理化性质空间变异较大,最浅地下水位为3.3 m,最深可达24.2 m,主要集中在6-8 m;土壤电导率、pH值、Cl^-和SO₄^2-均在表层0-40 cm含量较高,变异系数随土层深度的增加而减小。在时间上地下水位受准噶尔盆地上游农田用水的影响,水位呈季节性波动。一年中最高水位出现在4月,最低水位在7月。玛纳斯河向下游输水对提高盆地地下水位具有明显作用,地下水位平均可升高4.3 cm,地下水矿化度平均增幅1 g/L。地下水位对退化区物种多样性影响不大,但对梭梭生长产生显著影响。梭梭生长的适宜地下水位为5-8 m,且地下水矿化度小于4 g/L。地下水位大于8 m导致梭梭种群衰退,而地下水位小于4 m时,地下水矿化度影响土壤表层积盐,进而显著地降低物种多样性,阻碍梭梭幼苗更新,导致梭梭种群衰败。总结认为准噶尔盆地上游的玛纳斯河断流和农业灌溉对古尔班通古特沙漠西部平原地区的地下水位和水质产生显著影响,梭梭退化与地下水位变化显著相关,必须引起高度重视。     

Assessing the quality of native vegetation: The 'habitat hectares' approach

Summary Assessments of the 'quality', condition or status of stands of native vegetation or habitat are now commonplace and are often an essential component of ecological studies and planning processes. Even when soundly based upon ecological principles, these assessments are usually highly subjective and involve implicit value judgements. The present paper describes a novel approach to vegetation or habitat quality assessment (habitat hectares approach) that can be used in almost all types of terrestrial vegetation. It is based on explicit comparisons between existing vegetation features and those of 'benchmarks' representing the average characteristics of mature stands of native vegetation of the same community type in a 'natural' or 'undisturbed' condition. Components of the index incorporate vegetation physiognomy and critical aspects of viability (e.g. degree of regeneration, impact of weeds) and spatial considerations (e.g. area, distribution and connectivity of remnant vegetation in the broader landscape). The approach has been developed to assist in making more objective and explicit decisions about where scarce conservation resources are allocated. Although the approach does not require an intimate botanical knowledge, it is believed to be ecologically valid and useful in many contexts. Importantly, the index does not provide a definitive statement on conservation status nor habitat suitability for individual species. It purposefully takes a 'broad-brush' approach and is primarily intended for use by people involved with making environmentally sensitive planning and management decisions, but may be useful within environmental research programmes. The 'habitat hectares' approach is subject to further research and ongoing refinement and constructive feedback is sought from practitioners.     

Climate change impacts on Mediterranean vegetation are amplified at low altitudes

Aim

In the face of ongoing climate warming, we wanted to quantify impacts on vegetation at one of the major climatic and biogeographical boundaries of Europe, the limit between the Mediterranean and Eurosiberian biogeographical regions. We analyse temperature and moisture requirements of plants along altitudinal gradients at regional scale in the period 1980–2020 and we explore if changes coincide with observed changes in the same regions in terms of measured climatic data.

Location

Southern France.

Time period

1980–2020.

Taxa

Vascular plants.

Methods

We calculated shifts in plants’ temperature and moisture requirements for a large floristic database from south-eastern France (SIMETHIS) during the period 1980–2020 along altitudinal gradients by using ecological indicator values (EIV). Additionally, we analysed standardized weather station data from the same area and period, to investigate whether floristic changes are synchronized with climate changes.

Results

Vegetation data suggest a linear increase in temperature requirements of plant communities from 1980 to 2020 with a greater change at low altitudes. Upward shifts in temperature requirements coincided with observed climate change although warming did not show a general trend towards greater increases at low altitudes. Data on vegetation and climate suggest an upward shift of respectively 150 and 300 m for the boundary between Mediterranean and temperate belts. Moisture requirements of vegetation indicate an increase of the frequency of dry adapted species at low altitudes but an increase towards higher moisture requirements at high altitudes. Comparing vegetation responses with climate data suggests that responses are faster at low altitudes.

Main conclusions

Our analyses show that strong general changes in vegetation are underway and highlight faster responses of vegetation to warming in low altitudes compared to high altitudes and demonstrate the need for reliable data on vegetation and climate changes, especially on water balance.     

An overview of methods used to assess vegetation condition at the scale of the site

Summary   Rapid, on-ground assessments of vegetation condition are frequently used as a basis for landholder education, development applications, distributing incentive funds, prescribing restoration treatments and monitoring change. We provide an overview of methods used to rapidly assess vegetation condition for these purposes. We encourage those developing new approaches to work through the steps we have presented here, namely define management objectives and operational constraints; develop an appropriate conceptual framework for the ecosystems under consideration; select an appropriate suite of indicators; and consider the options available for combining these into an index. We argue that information must be gained from broader scales to make decisions about the condition of individual sites. Remote sensing and spatial modelling might be more appropriate methods than on-ground assessments for obtaining this information. However, we believe that spatial prediction of vegetation condition will only add value to on-ground assessments rather than replace them. This is because the current techniques for spatially predicting vegetation condition cannot capture all of the information in a site assessment or at the required level of accuracy, and maps cannot replace the exchange of information between assessors and land managers that is an important component of on-ground assessment. There is scope for more sophistication in the way on-ground assessments of vegetation condition are undertaken, but the challenge will be to maintain the simplicity that makes rapid on-ground assessment a popular vehicle for informing natural resource management. We encourage greater peer review and publishing in this field to facilitate greater exchange of ideas and experiences.     

草地生态系统植被变化的自然与人为因素定量区分方法

定量区分导致草地生态系统植被变化的自然和人为因素,是生态系统科学管理和保育的关键。因此,综述当前应用较为广泛的定量区分方法,包括主成分分析法、层次分析法、残差趋势法和模型差值法等,比较不同方法的计算原理、优势及误差来源,进而结合典型区域或典型生态系统,对不同方法进行对比和分析。总体而言,每种方法各有其优势和缺点,当前采用同一方法在不同区域或生态系统类型应用的研究较多,但针对方法本身改进或优化的研究较少。此外,针对同一区域开展的不同区分方法间的结果也存在差异。定量区分的结果除受方法本身算法的局限外,也受数据源的时空连续性及分辨率的影响。未来定量区分方法将强调：(1)在指标的选取上,要兼顾全面、多角度、不冗余等原则;(2)进行多源数据与多时空尺度融合,在更高时空分辨率定量区分自然与人为因素,从单一因子的贡献率区分到更多综合性指标的贡献率区分;(3)对定量区分方法本身的改进,这是当前的重点与难点。以期为生态系统适应性管理与关键生态功能的针对性保育提供科学依据和政策导向。     

Zonation in the marsh vegetation of the Blackwood River Estuary in south-western Australia

There is little published information about coastal salt marshes in south-western Australia, which are prominent in estuaries but absent from the high energy coastline. The zonation of the marshes of the Blackwood estuary resemble those in other parts of the world, in that Sarcocornia marsh occurs near the mouth, followed by rush marsh, with sedges further upstream, suggesting that salinity is a prime determining factor. Spartina and Phragmites are absent. The most exensive marsh is the Juncus kraussii rush community which is invaded by the paperbark tree, Melaleuca cuticularis. The sedge Baumea juncea forms a marsh community on the shores of the lower tidal river and a progression of species occurs with distance along the tidal river. A number of dynamic processes observed in these marshes are described and related to observations elsewhere     

汉江上游金水河流域森林植被对水环境的影响

以汉江上游金水河流域为研究区域,分析了流域森林植被对水环境的影响。利用年降水量、林冠截留率和不同森林类型面积的数据,计算了金水河流域森林生态系统的水源涵养量,分析了流域森林植被对水量的影响;采用监测的方法,分别对金水河流域阔叶林森林生态系统的大气降水、枯落物层、土壤层和出口河水的水质进行了比较分析,探讨流域森林植被对水质的影响。结果表明,(1)金水河流域森林生态系统的水源年涵养总量为466.79×106m3,(2)流域阔叶林森林生态系统能够调节pH值,缓解大气降水的酸性环境;降低了大气降水中TDS、CODMn、HCO3、SO4、Cl、NO3、NH4-N、NO3-N、PO4-P、TDP、As、Ba、Cr、Na、Pb、Fe、K、Mn、V和Zn的含量,净化了水质。(3)根据各贮水层的水质分析,推断了河水中各物质的不同来源。研究为南水北调中线工程水源地的管理和建设提供了参考。     

石羊河流域自然植被对生态系统服务的约束效应

石羊河流域生态环境退化,生态屏障功能减弱,提高该地区生态系统的服务功能具有重要意义。植被的生长状况是影响生态系统服务供给的重要因素,定量的探讨分析植被与生态系统服务之间的关系十分必要。以石羊河流域为研究区,采用约束线法,分析了植被对产水量、土壤保持及固碳3个生态系统服务的约束效应;同时,计算了2015年这3个生态系统服务潜力的空间分布及石羊河流域综合潜力分布格局。结果表明:(1)植被覆盖度与产水量、土壤保持之间的约束线呈开口向下抛物线型,即随着植被覆盖度的增加,约束效应逐渐减小,后逐渐增大;与固碳服务呈正凸型,即:植被覆盖度能有效的约束固碳,且成比例增加约束效应;(2)植被覆盖度对产水量、土壤保持及固碳服务的约束效应存在时空异质性;(3)石羊河流域三种服务的提升潜力均呈西南高东北低、高服务值与高潜力值并存的分布特征,其中东大河、西大河、西营河及古浪河是流域生态服务的主要供给者和服务潜力提升的主要贡献者。     

The influence of local elevation on soil properties and tree health in remnant eucalypt woodlands affected by secondary salinity

More than 2 M ha of remnant vegetation in Australia is predicted to be at risk from shallow water tables by 2050. Currently, vegetation is considered to be at risk where the water table is predicted to be less than 2 m below the soil surface, yet casual observation of areas affected by secondary salinity in the Western Australian wheatbelt has suggested that small differences in elevation (< 0.5 m) are important in determining plant health. In this study, we investigated how small changes in elevation (and hence depth to the water table) affected soil Cl concentrations and water contents, and whether small changes in elevation were associated with major changes in tree health in two remnants of Eucalyptus wandoo Blakely woodland with secondary salinity. At one site there were strong dissimilarities between soil samples collected above or below relative elevations of 0.5 m in areas with a shallow (0.3 m deep in September 2001) and saline water table. This was reflected in almost complete tree mortality at relative elevations below 0.5 m. However, low rainfall in 2001 meant that it was unlikely that current soil conditions had caused tree death. When water table data for 1999 was overlaid over plots of tree health and transect topography, high levels of tree mortality corresponded with areas where the water table was at or above the ground surface. At the other site, there was no clear relationship between elevation, soil characteristics and tree health. Localised variation in abiotic conditions and ecosystem processes at a fine-scale may buffer, to some extent, the spatial impact of soil salinity and waterlogging in remnant vegetation. Collapses in tree health at some sites are likely to be related to extreme and episodic events, which we may have limited ability to predict.     

植被(植物群落)稳定性研究评述

稳定性是植物群落结构与功能的一个综合特征。本文对影响植被稳定性的主要干扰因索、群落多样性(复杂性)与稳定性的关系、植被稳定性的判定与测度指标、稳定性的机制等方面的研究进展进行了阐述。指出应加强干扰对植被稳定性影响及提高干旱区人工植被稳定性的技术措施的的研究,以指导自然植被的保护利用和人工植被的建设,对植被稳定性机制的认识需要从植物群落内部的生物学生态学过程方面进行深入研究。     

Modelling the vegetation of China using the process-based equilibrium terrestrial biosphere model BIOME3

1 We model the potential vegetation and annual net primary production (NPP) of China on a 10′ grid under the present climate using the processed‐based equilibrium terrestrial biosphere model BIOME3. The simulated distribution of the vegetation was in general in good agreement with the potential natural vegetation based on a numerical comparison between the two maps using the ΔV statistic (ΔV = 0.23). Predicted and measured NPP were also similar, especially in terms of biome‐averages. 2 A coupled ocean–atmosphere general circulation model including sulphate aerosols was used to drive a double greenhouse gas scenario for 2070–2099. Simulated vegetation maps from two different CO₂ scenarios (340 and 500 p.p.m.v.) were compared to the baseline biome map using ΔV. Climate change alone produced a large reduction in desert, alpine tundra and ice/polar desert, and a general pole‐ward shift of the boreal, temperate deciduous, warm–temperate evergreen and tropical forest belts, a decline in boreal deciduous forest and the appearance of tropical deciduous forest. The inclusion of CO₂ physiological effects led to a marked decrease in moist savannas and desert, a general decrease for grasslands and steppe, and disappearance of xeric woodland/scrub. Temperate deciduous broadleaved forest, however, shifted north to occupy nearly half the area of previously temperate mixed forest. 3 The impact of climate change and increasing CO₂ is not only on biogeography, but also on potential NPP. The NPP values for most of the biomes in the scenarios with CO₂ set at 340 p.p.m.v. and 500 p.p.m.v. are greater than those under the current climate, except for the temperate deciduous forest, temperate evergreen broadleaved forest, tropical rain forest, tropical seasonal forest, and xeric woodland/scrub biomes. Total vegetation and total carbon is simulated to increase significantly in the future climate scenario, both with and without the CO₂ direct physiological effect. 4 Our results show that the global process‐based equilibrium terrestrial biosphere model BIOME3 can be used successfully at a regional scale.     

怒江-萨尔温江流域植被覆盖时空变化趋势及驱动力

植被作为陆地生态系统的主要组成部分,对区域生态系统环境变化、全球碳循环和气候调节具有非常重要的作用。怒江-萨尔温江流域是东南亚最重要的跨境河流之一,其植被变化会影响区域生态系统和气候。研究以怒江-萨尔温江流域为研究区,基于2000—2021年MODIS NDVI数据,利用BFAST模型、Hurst指数以及地理探测器研究了其植被覆盖时空演变趋势和未来可持续性以及驱动因子。结果表明：(1)2000—2021年,怒江-萨尔温江流域植被覆盖总体呈波动上升趋势,多年平均植被覆盖度FVC(Fractional Vegetation Cover)为0.73,以高植被覆盖和较高植被覆盖为主。植被分布具有明显的空间异质性,下游和中游植被覆盖明显优于上游。(2)BFAST趋势表明,近22年怒江-萨尔温江流域植被覆盖改善和退化的区域面积占比分别为71.24%、28.76%,改善的区域远大于退化的区域,说明研究区植被得到较好的保护。Hurst指数显示,未来植被将持续改善和退化的区域占比分别为94.89%、2.76%。BFAST与Hurst二者叠加共耦合了17种植被覆盖的未来趋势情形,整体上未来植被呈持续改善为...     

Ecological consequences of altered hydrological regimes in fragmented ecosystems in southern Australia: Impacts and possible management responses

Abstract Although the potential impacts of rising water tables and secondary salinization on agricultural land in southern Australia have been recognized for some time, it is only recently that the impacts on native vegetation have been considered. Despite the likely extent and severity of the problem, no comprehensive approach to assessing the impact of salinity upon native vegetation has been attempted to date. In the present paper, we discuss the causes and impacts of rising water tables and dryland salinity, assess the levels of risk in different ecosystem types and consider the possibilities for the maintenance of biodiversity and ecosystem function in vegetation at risk. We examine the salinity risk to woodland vegetation in the Western Australian (WA) wheatbelt, and consider both broad‐scale context and finer‐scale variation within individual patches of vegetation. From this information, we develop a set of conceptual models of the potential impacts of shallow saline water tables on ecosystem structure and processes in remnant vegetation in agricultural areas, particularly in the WA wheatbelt. First, we suggest that fine‐scale variability in surface topography and soil characteristics may play an important role in limiting the impacts of rising saline water tables. The outcome will depend on the interaction of the heterogeneity of the impact, species distribution in relation to small‐scale environmental heterogeneity and variation in species response to hydrological change. Second, we suggest that shallow saline water tables can be considered to cause an ‘edge effect’, which moves inwards from the edge of remnants of native vegetation. Finally, we consider how saline surface flows exacerbate the effects of shallow saline water tables and hasten vegetation decline in remnant areas. We put these models forward as hypotheses to be tested in different situations. We contrast the situation of secondary salinization in Australian vegetation with that of naturally saline systems in Australia and elsewhere, and suggest that these systems may provide important signposts toward developing management approaches for vegetation at risk. In conclusion, we consider the need to set priorities for the protection and restoration of natural vegetation at risk from altered hydrology, based on an assessment of relative threat and probability of persistence or recovery. We highlight the urgency for action that protects native vegetation from the increasing risks of rising water tables.     

长江流域农作物起源及其与生物多样性特征的关联

长江流域的农耕文明是中华文明的重要组成部分。作为世界著名的农作物起源中心之一, 长江流域拥有丰富的生物多样性, 孕育了大量的栽培植物。本文梳理了起源于长江流域的农作物的资料以及新石器时代文化遗址的植物遗存信息; 结合对长江流域的自然环境特征与全新世以来植被变化的总结, 尝试厘清长江流域对植物资源利用的动态变化, 探讨本地栽培植物与生物多样性的关联。结果表明长江流域农耕文明以稻作为最主要的生产方式, 驯化了大量果树与水生蔬菜, 反映出对本地亚热带常绿阔叶林与湿地的依赖与适应。与其他流域相比, 长江流域具有相对优越的生态要素配置, 其驯化作物类型表现出典型的亚热带湿润森林植被区特征。研究长江流域农作物驯化相关的自然与人类因素, 有助于我们更好地把握长江流域农耕文明的起源。本文不但可为长江流域植物遗传资源的保护与开发提供参考, 而且对于推进长江流域的生态文明建设和可持续发展具有指导作用。