Assessing the impact of ecological and economic factors on land degradation vulnerability through multiway analysis

Land degradation (LD) is a global problem which involves climate, soil, vegetation, economic, and population conditions. In Mediterranean Europe climatic variability and human pressure combine to produce soil sealing, erosion, salinisation, fire risk, and landscape fragmentation, all regarded as important factors to start LD. The aim of this paper is to introduce a time-series evaluation of land vulnerability to degradation based on nine ecological and economic variables. The analysis was carried out over 1970–2000 at the municipality level in Latium (central Italy), a region which has shown increasing land vulnerability in the last years. A multiway data analysis (MDA) was applied in order to explore the relationship among indicators over the study period. Their importance in determining LD vulnerability was estimated through a weighting system based on MDA results. A composite index of land vulnerability (LVI) was obtained as the weighted average of the nine variables transformed into single indicators, according to their relationship with LD. Considerable increases in LVI were observed in dry coastal and lowland municipalities close to Rome, thus indicating that climate aridity, population growth, and land use changes are important determinants of land vulnerability in Latium. LVI was positively correlated to the environmental sensitive area index (ESAI) measured on the same spatial and time scales, thus suggesting that a sound evaluation of land vulnerability is possible through LVI score.     

Towards a process-based evaluation of land vulnerability to soil degradation in Italy

This paper illustrates a process-based approach aimed at classifying large areas into different classes of vulnerability to Mediterranean land and soil degradation (LD and SD). A wide set of environmental and socio-economic variables was used to describe five soil degradation processes (soil erosion, salinisation, sealing, contamination, and compaction) and climate taken together as the final determinants of LD in Italy. The elementary variables contributed to generate six thematic indicators which depict the level of vulnerability of the country to each degradation process. The Multivariate Soil Degradation Vulnerability Index (MSDVI) provided an estimation of the level of land vulnerability by aggregating the six indicators. Multidimensional analyses and Geographic Information System tools were used to derive the thematic indicators and the synthetic index. Results demonstrated that in Italy, climate, soil erosion, and soil compaction/agricultural intensification represent the soil degradation processes with a potentially higher role in determining vulnerability to LD, even if with different spatial configuration patterns. On average, the most vulnerable area was insular Italy, followed by southern Italy; northern and central Italy were found less vulnerable to LD, however the MSDVI was found locally high also in northern Italy. The validation tests performed on MSDVI by field assessment and comparison with ancillary data indicated that the index is a reliable proxy of land vulnerability to soil degradation. Advantages of this approach compared to other procedures aimed at assessing LD were finally discussed.     

Validation of MEDALUS Fire Risk Index using Forest Fires Statistics through a multivariate approach

A Fire Risk Index (FIRISK) based on an original land cover/land use nomenclature has been developed in the framework of EU-funded MEDALUS projects and integrated into a composite index of sensitivity to desertification (the so called environmentally sensitive area index: ESAI). The objective of the present study is to introduce a validation approach assessing the correlation between the FIRISK and seven independent fire indicators and quantifying the similarity in their spatial distribution in a study area (Attica, Greece) characterized by high fire risk and fragmented land-use structure. The FIRISK correlated positively with four out of seven fire indicators (average fire size, percentage of burnt area on the total municipal area, percentage of cropland and pastures burnt in each fire) in a non-linear fashion. Cluster analysis indicates that FIRISK spatial distribution was coherent with variables describing both fire size and the use of land endangered by fire. Results of the present study demonstrate that the FIRISK is a reliable indicator of fire risk within the ESAI framework. Moreover, the index is considered a key component of multi-criteria decision support systems classifying land according to the level of fire sensitivity.     

Assessing trends in climate aridity and vulnerability to soil degradation in Italy

The present study illustrates a framework to analyze changes in climate aridity and soil degradation on a country scale in Italy. The spatial distribution of an indicator of soil vulnerability to degradation (the SQI, soil quality index) was compared with an aridity index (the ratio of annual rainfall to annual reference evapotranspiration) estimated on a decadal basis during 1951–2010. The aridity index decreased by 0.38% per year indicating increased aridity and a non-uniform spatial distribution of soil vulnerability to degradation. Changes in the aridity index were found associated with the lowest SQI classes, suggesting that the largest increase in climate aridity affects land with high-quality soils. Territorial disparities in the aridity index between high-quality and low-quality soils decreased over time indicating a more homogeneous and dry climate regime prevailing in the more recent decades. Results may inform sustainable land management policies and National Action Plans to combat desertification in the Mediterranean region. Areas classified at increased aridity and high vulnerability to soil degradation should be identified as a key target for climate change mitigation policies. Sustainable land management strategies are required to address the dependency between climate variations, land-use changes and soil degradation processes.     

Agro-ecological field vulnerability evaluation and climate change impacts in Souma area (Iran), using MicroLEIS DSS

Soil erosion and contamination are two main desertification indices or land degradation agents in agricultural areas. Global climate change consequence is a priority to predict global environmental change impacts on these degradation risks. This agro-ecological approach can be especially useful when formulating soil specific agricultural practices based on the spatial variability of soils and related resources to reverse environmental degradation. Raizal and Pantanal models within the new MicroLEIS framework, the Ero&Con package, are database/expert system evaluation approach for assessing limitations to land use, or vulnerability of the land to specified agricultural degradation risks. This study was performed in Souma area with approximately 4100 ha extension in the North-West of Iran (west Azarbaijan). Based on 35 sampling soils, Typic Xerofluvents, Typic Calcixerepts, Fluventic Haploxerepts and Fluventic Endaquepts were classified as main subgroups. Climatological data, referred to temperature and precipitation of more than 36 consecutive years were collected from Urmieh station reports and stored in monthly Climate Database CDBm, as a major component of MicroLEIS DSS (CDBm) program. Climate data for a hypothetical future scenario were collected from the Intergovernmental Panel on Climate Change (IPCC) reports for the 2080s period. The evaluation approach predicts that attainable water erosion vulnerability classes were none (V1) very low (V2) and moderately low (V4) in the total of 72%, 13% and 15% of the Souma area, respectively and they will not affected by climate change. On contrary, attainable wind erosion vulnerability classes will increase. Also, phosphorous and heavy metal contamination vulnerability risks will not differ in two compared scenarios while nitrogen and pesticides vulnerability classes will be improved.     

色林错-普若岗日国家公园潜在建设区生态环境脆弱性格局评估

西藏色林错及周边区域是高原高寒草原生态系统中珍稀濒危生物物种最多的地区,也是高品质自然景观和文化遗产集中分布区,建立色林错-普若岗日国家公园(以下简称"色-普国家公园")首要考虑当地脆弱的生态环境问题。本研究遵循"因素识别-指标构建-单因子评估-综合评估"的基本思路,识别色-普国家公园潜在建设区的生态环境脆弱性因素,开展冻融侵蚀、水土流失、土地沙化、土壤风蚀、生境环境敏感性单因子评估,结合海拔、坡度、重要生态系统等限定因子,实现对国家公园潜在建设区生态环境脆弱性综合评估,以期为未来国家公园空间范围的确定、功能分区以及适度开展生态旅游等空间布局提供基础支撑。研究表明:(1)潜在建设区存在较严重的冻融侵蚀、水土流失、草地退化、生物多样性减少等生态环境问题。(2)单因子评估显示,潜在建设区主要属于生态环境的中度和高度敏感区、水土流失的中度敏感区、冻融侵蚀的轻度和中度敏感区,土壤风蚀的不敏感和轻度敏感区、土壤沙化的不敏感区。(3)综合评估显示,潜在建设区生态环境脆弱性高,高度脆弱区面积比例达57.60%,主要分布在色林错的西部和北部;低度脆弱区仅占7.38%,主要分布在色林错东部;尼玛县低度脆弱区分布面积最小,安多县分布最多;双湖县高度脆弱区面积分布最广。(4)建议未来国家公园建设把以生态旅游为主的人类活动范围集中在低度脆弱区,并重点加强对高度脆弱区的生态系统完整性与原真性保护。     

土壤保持服务:概念、评估与展望

土壤保持服务作为一项重要的生态系统调节服务,是防止区域土地退化、降低洪涝灾害风险的重要保障。针对在全球范围内影响最大的土壤水蚀,基于土壤侵蚀、运移和输出过程,对土壤保持服务的概念、评估方法进行了梳理总结。土壤保持服务是指生态系统防止土壤流失的侵蚀调控能力及对泥沙的储积保持能力。土壤保持服务的评估往往是基于通用土壤流失方程RUSLE(Revised Universal Soil Loss Equation),以潜在土壤侵蚀量(裸地时土壤侵蚀量)与实际土壤侵蚀量之差,作为指标衡量。由于生态过程具有尺度依赖性,对土壤保持服务的有效评估,需要采用多尺度方法。土壤保持服务与人类需求紧密相关,在未来土壤保持服务研究中应强调连接土壤保持服务与人类福祉,对土壤保持服务产生、流动、使用的全过程及土壤保持服务时空动态与人类福祉变化的关系进行探究。     

An integrated risk assessment for climate change: analysing the vulnerability of sharks and rays on Australia's Great Barrier Reef

An Integrated Risk Assessment for Climate Change (IRACC) is developed and applied to assess the vulnerability of sharks and rays on Australia's Great Barrier Reef (GBR) to climate change. The IRACC merges a traditional climate change vulnerability framework with approaches from fisheries ecological risk assessments. This semi‐quantitative assessment accommodates uncertainty and can be applied at different spatial and temporal scales to identify exposure factors, at‐risk species and their key biological and ecological attributes, critical habitats a`nd ecological processes, and major knowledge gaps. Consequently, the IRACC can provide a foundation upon which to develop climate change response strategies. Here, we describe the assessment process, demonstrate its application to GBR shark and ray species, and explore the issues affecting their vulnerability to climate change. The assessment indicates that for the GBR, freshwater/estuarine and reef associated sharks and rays are most vulnerable to climate change, and that vulnerability is driven by case‐specific interactions of multiple factors and species attributes. Changes in temperature, freshwater input and ocean circulation will have the most widespread effects on these species. Although relatively few GBR sharks and rays were assessed as highly vulnerable, their vulnerability increases when synergies with other factors are considered. This is especially true for freshwater/estuarine and coastal/inshore sharks and rays. Reducing the impacts of climate change on the GBR's sharks and rays requires a range of approaches including mitigating climate change and addressing habitat degradation and sustainability issues. Species‐specific conservation actions may be required for higher risk species (e.g. the freshwater whipray, porcupine ray, speartooth shark and sawfishes) including reducing mortality, preserving coastal catchments and estuarine habitats, and addressing fisheries sustainability. The assessment identified many knowledge gaps concerning GBR habitats and processes, and highlights the need for improved understanding of the biology and ecology of the sharks and rays of the GBR.     

Assessment of soil and vegetation changes due to hydrologically driven desalinization process in an alkaline wetland,Hungary

This study investigates a soil–water–vegetation system in a drying-out alkaline sodic wetland altered by climate change and artificial drainage by evaluating the habitat pattern and the physical and chemical attributes of the upper soil. The spatial and temporal alteration of the vegetation was monitored by detailed coenological investigations and habitat mapping during a 13-year period (2002–2014) to analyse the succession trend of the habitat in the changing environment. The spatial structures of the physical and chemical attributes of the soil were surveyed by topsoil sampling along a regular network to detect the desalinization process and to reveal the discrepancies between the soil attributes and the typical habitats because anomalies between the habitat and its optimal soil properties can project a possible vegetation change in a dynamically changing sodic ecosystem. The micro-topography was investigated to detect the effect of the elevation difference on the hydrologic conditions, soil and vegetation attributes. Statistical analyses were performed to describe the characteristic pedological processes and the spatial structures of the soil parameters. An overlapping analysis was conducted to compare the soil, vegetation pattern and topography to explore the relationships in the altering soil–water–vegetation system.Rapid alterations of the habitats, species composition, and soil desalinization processes were clearly recognised. The rate of change reflects degradation beyond the natural dynamics of vegetation processes. The desalinization process was extremely rapid due to the sandy sediment. The significant changes in the vegetation and soil pattern led to the loss of diversity in the short term; annual salt pioneer swards and Puccinellia swards became highly threatened. The main driving factors in the desalinization process are water shortage caused by artificial drainage and climate change, furthermore extreme high precipitation which intensifies leaching. The degradation process can be mitigated by adequate water management because habitats have a high naturalness reflecting good regeneration potential.     

Aquatic degradation in shallow coastal plain lakes: Gradients or thresholds?

The establishment of introduced species in aquatic and wetland habitats is often associated with human-related environmental degradation. In the blackwater streams of the New Jersey Pinelands, the presence of nonnative species drives the relationship between community composition and watershed disturbance associated with developed land and upland agriculture. Most Pinelands lakes are shallow, artificial stream impoundments. In this study, we determined if land-use gradients or thresholds were associated with the presence of nonnative-herbaceous-plant, woody-plant, fish, and anuran species in 30 Pinelands stream impoundments. Correlation and regression analyses indicated that the response of all four taxonomic groups to watershed disturbance was an increase in the number of nonnative species and the proportion of total species richness represented by nonnative species. Native-anuran richness decreased along the watershed-disturbance gradient. We found both linear and nonlinear responses when relating species-richness attributes to the percentage of altered land (combined percentage of upland agriculture and developed land) in the associated watersheds, but the nonlinear responses cannot be considered land-use-related degradation-threshold responses. The breaks in the regression lines describing the relationship between the percentage of total species richness represented by nonnative plants and fish and altered land in our Pinelands watersheds did not represent a degradation threshold because, with the exception of the percentage of total species richness represented by nonnative-anuran species, a progressive decline in aquatic integrity was observed before the break points. Kruskal–Wallis ANOVA revealed significant differences in species-richness attributes only among stream impoundments with contrasting altered-land profiles, providing further evidence that aquatic degradation was progressive. Logistic regression identified the point along the watershed-disturbance gradient at which the probability of encountering nonnative bullfrogs was greater than that for native carpenter frogs.     

Influence of macroclimate and local conservation measures on taxonomic,functional, and phylogenetic diversities of saproxylic beetles and wood-inhabiting fungi

Wood-inhabiting fungi and saproxylic beetles are threatened by habitat degradation. Our understanding of the importance of macroclimate and local factors determining their taxonomic diversity has increased, but determinants of functional and phylogenetic diversity are poorly understood. We investigated assemblages of wood-inhabiting fungi and saproxylic beetles along a 1000 m elevational gradient of a temperate low mountain range. We (i) tested the relative importance of macroclimate (i.e. elevation) and local variables (microclimate, i.e. canopy closure, amount and diversity of dead wood) in determining observed and rarefied diversities and (ii) explored whether determinants of observed functional and phylogenetic diversities match those of taxonomic diversity. For both taxa, the determinants of observed phylogenetic and functional diversities largely matched those of taxonomic diversity. The diversity of wood-inhabiting fungi was predominantly determined by local variables, whereas that of saproxylic beetles was determined by both local variables and elevation. Taxonomic and phylogenetic diversities of saproxylic beetles decreased with increasing elevation, but standardized functional richness and entropy of both groups increased with increasing elevation. Diversities of wood-inhabiting fungi increased with canopy closure, while diversities of saproxylic beetles decreased with increasing canopy closure. Microclimate and dead-wood amount and diversity affected the observed and rarefied diversity of both saproxylic taxa, which justifies conservation actions that focus on attributes of dead wood and canopy cover. The contrasting responses of fungi and beetles highlight the need for amounts of diverse dead wood in the various microclimates to preserve functional and phylogenetic diversities of saproxylic organisms.     

Habitat filtering and adult dispersal determine the taxonomic composition of stream insects in an urbanizing landscape

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Climate Variation and Soil Carbon and Nitrogen Cycling Processes in a Northern Hardwood Forest

We exploited the natural climate gradient in the northern hardwood forest at the Hubbard Brook Experimental Forest (HBEF) to evaluate the effects of climate variation similar to what is predicted to occur with global warming over the next 50–100 years for northeastern North America on soil carbon (C) and nitrogen (N) cycle processes. Our objectives were to (1) characterize differences in soil temperature, moisture and frost associated with elevation at the HBEF and (2) evaluate variation in total soil (TSR) and microbial respiration, N mineralization, nitrification, denitrification, nitrous oxide (N₂O) flux, and methane (CH₄) uptake along this gradient. Low elevation sites were consistently warmer (1.5–2.5°C) and drier than high elevation sites. Despite higher temperatures, low elevation plots had less snow and more soil frost than high elevation plots. Net N mineralization and nitrification were slower in warmer, low elevation plots, in both summer and winter. In summer, this pattern was driven by lower soil moisture in warmer soils and in winter the pattern was linked to less snow and more soil freezing in warmer soils. These data suggest that N cycling and supply to plants in northern hardwood ecosystems will be reduced in a warmer climate due to changes in both winter and summer conditions. TSR was consistently faster in the warmer, low elevation plots. N cycling processes appeared to be more sensitive to variation in soil moisture induced by climate variation, whereas C cycling processes appeared to be more strongly influenced by temperature.     

Introduced earthworms in agricultural and reclaimed land: their ecology and influences on soil properties, plant production and other soil biota

Accidental and deliberate introductions of earthworms into agricultural and reclaimed land are natural experiments that provide opportunities to understand the attributes of successful invaders and their impacts on local biota and ecosystem processes. We consider various case studies (e.g., earthworm invasions in agricultural soils in Australia and Brazil) and deliberate introductions of earthworms into reclaimed mine sites, landfills and cutaway peat in the U.K. and Ireland. Invasions of exotic earthworms, such as European Lumbricidae in Australia, have been geographically extensive, but remain very patchy at regional and field scales. Their impacts on soil properties, plant production and other biota are therefore also likely to be patchy. Various methods have been developed to deliberately inoculate exotic earthworms into disturbed lands, with varying degrees of success. The factors controlling success are, in general, poorly understood. A broad range of impacts of invasive earthworms on soil properties (e.g., soil structure, nutrient availability, burial of surface materials, incidence of root diseases) and plant yield and quality have been reported. Less is known of the impacts of invasive earthworms on other soil fauna, but they are likely to occur due to alterations in food availability and habitat structure. Influences on other biota are likely to extend to aboveground communities as well as those belowground. Introductions of earthworms to disturbed lands can yield substantial benefits in agricultural productivity and amelioration of soil degradation. However, the potential impact of the promotion or control of such introductions on non-target biota and ecosystem processes in pristine ecosystems nearby should be considered.     

Soil textural class plays a major role in evaluating the effects of land use on soil quality indicators

Inappropriate land use that negatively affects ecological processes and soil quality is generally considered to be the primary cause of soil degradation in tropical agroecosystems. We hypothesized that in addition to land use, soil textural class also has an important effect on ecological processes and soil quality. To test our hypothesis, effects of land use change on soil organic fractions as well as microbial and biochemical indicators were quantified for clayey and sandy-clay-loam soils within the native Cerrado biome, pasture (Brachiaria brizantha) and sugarcane (Saccharum officinarum) agroecosystems in southwestern Brazil (Minas Gerais state). Labile carbon, humic substances, soil microbial respiration (SMR), microbial biomass carbon (MBC), metabolic quotient (qCO₂), hydrolysis of fluorescein diacetate (FDA), beta-glucosidase, urease, phosphatase and arylsulphatase activities were measured for each sample. Labile carbon concentrations were not affected by land use but were lower in sandy-clay-loam soil than clayey soil. Humic substances were at the highest concentrations in the native Cerrado and the lowest in sugarcane agroecosystems. Sandy-clay-loam soil had lower humic acid concentrations than clayey soil. Soil microbial indicators (SMR, MBC and FDA) showed lower values in pasture and sugarcane agroecosystems than in the native Cerrado. FDA was a more sensitive microbial indicator than SMR and MBC for detecting land use and textural class differences. The qCO₂ indices were greater in sugarcane systems than in either pasture or native Cerrado systems. The activity of exocellular hydrolytic enzymes, such as beta-glucosidase, urease, phosphatase and arylsulphatase, was smaller in sugarcane and pasture agroecosystems than in native Cerrado ecosystems. Within the same land use, the activity of these enzymes was always greater in clayey soil than in sandy-clay-loam soil, indicating a higher impact of land uses on enzyme activities in clayey soils. Results for the measured indicators support the hypothesis that soil textural class plays a major role in assessing differences between land use systems in the Brazilian Cerrado biome.     

海南岛生态环境脆弱性评价

基于SOPAC和UNEP所建立的环境脆弱性评价方法,从风险、抵抗力、损害与退化3个方面构建了指标体系和综合指数,对海南岛生态环境脆弱性进行了评价.结果表明：海南岛的生态环境风险处于中等水平,其风险主要源于高强度的人类活动,包括强化农业、大众旅游业、采矿业以及岛上居民和游客所排放的大量固体废弃物等;较大的土地面积、较大的海拔变化幅度、完整的地理板块及丰富的生境类型等自然地理特征,赋予了海南岛较强的生态环境风险抵抗力,但受历史上人为和自然风险的累积影响,海南岛生态系统的损害与退化已较为严重,主要体现在土地退化和生物多样性的丧失等方面;综合考虑风险、抵抗力和损害与退化三方面因素,海南岛生态环境综合脆弱性处于中等水平,部分指标表现出很低的脆弱性,但另一些指标却表现出很高的脆弱性.     

Vegetation Cover,Tidal Amplitude and Land Area Predict Short-Term Marsh Vulnerability in Coastal Louisiana

The loss of coastal marshes is a topic of great concern, because these habitats provide tangible ecosystem services and are at risk from sea-level rise and human activities. In recent years, a significant effort has gone into understanding and modeling the relationships between the biological and physical factors that contribute to marsh stability. Simulation-based process models suggest that marsh stability is the product of a complex feedback between sediment supply, flooding regime and vegetation response, resulting in elevation gains sufficient to match the combination of relative sea-level rise and losses from erosion. However, there have been few direct, empirical tests of these models, because long-term datasets that have captured sufficient numbers of marsh loss events in the context of a rigorous monitoring program are rare. We use a multi-year dataset collected by the Coastwide Reference Monitoring System that includes transitions of monitored vegetation plots to open water to build and test a predictive model of near-term marsh vulnerability. We found that despite the conclusions of previous process models, elevation change had no ability to predict the transition of vegetated marsh to open water. However, we found that the processes that drive elevation change were significant predictors of transitions. Specifically, vegetation cover in prior year, land area in the surrounding 1 km² (an estimate of marsh fragmentation) and the interaction of tidal amplitude and position in tidal frame were all significant factors predicting marsh loss. This suggests that (1) elevation change is likely better a predictor of marsh loss at timescales longer than we consider in this study and (2) the significant predictive factors affect marsh vulnerability through pathways other than elevation change, such as resistance to erosion. In addition, we found that, while sensitivity of marsh vulnerability to the predictive factors varied spatially across coastal Louisiana, vegetation cover in prior year was the best single predictor of subsequent loss in most sites followed by changes in percent land and tidal amplitude. The model’s predicted land loss rates correlated well with land loss rates derived from satellite data, although agreement was spatially variable. These results indicate (1) monitoring the loss of small-scale vegetation plots can inform patterns of land loss at larger scales, (2) the drivers of land loss vary spatially across coastal Louisiana, and (3) relatively simple models have potential as highly informative tools for bioassessment, directing future research and management planning.     

Landscape structure and land use history influence changes in island plant composition after 100 years

Aim We investigated how current and historical land use and landscape structure affect species richness and the processes of extinction, immigration and species turnover. Location The northern part of the Stockholm archipelago, Baltic Sea, Sweden. We resurveyed 27 islands ranging from 0.3 to 33 ha in area. Methods We compared current plant survey data, cadastral maps and aerial photographs with records obtained from a survey in 1908, using databases and a digital elevation model to examine changes in plant community dynamics in space and time. We examined the effects of local and landscape structure and land use changes on plant species dynamics by using stepwise regression in relation to eight local and three landscape variables. The eight local variables were area, relative age, shape, soil heterogeneity, bedrock ratio, number of houses, forest cover change, and grazing 100 years ago. The three landscape variables were distance to mainland, distance to closest island with a farm 100 years ago, and structural connectivity. Hanski’s connectivity measure was modified to incorporate both connectivity and fragmentation. Results The investigated islands have undergone drastic changes, with increasing forest cover, habitation, and abandonment of grassland management. Although the total species richness increased by 31% and mean island area by 23%, we found no significant increase in species richness per unit area. Local variables explain past species richness (100 years ago), whereas both local and landscape variables explain current species richness, extinctions, immigrations and species turnover. Grazing that occurred 100 years ago still influences species richness, even though grazing management was abandoned several decades ago. The evidence clearly shows an increase in nitrophilous plant species, particularly among immigrant species. Main conclusions This study highlights the importance of including land use history when interpreting current patterns of species richness. Furthermore, local environment and landscape patterns affect important ecological processes such as immigration, extinction and species turnover, and hence should be included when assessing the impact of habitat fragmentation and land use change. We suggest that our modified structural connectivity measure can be applied to other types of landscapes to investigate the effects of fragmentation and habitat loss.     

Prediction of soil property distribution in paddy soil landscapes using terrain data and satellite information as indicators

Sustainable land management and land use planning require reliable information about the spatial distribution of the physical and chemical soil properties affecting both landscape processes and services. Although many studies have been conducted to identify the spatial patterns of soil property distribution on various scales and in various landscapes, only little is known about the relationships underlying the spatial distribution of soil properties in intensively used, finely structured paddy soil landscapes in the southeastern part of China. In order to provide adequate soil information for the modelling of landscape processes, such as soil water movement, nutrient leaching, soil erosion and plant growth, this study investigates to what extent cheap and readily available ancillary information derived from digital elevation models and remote sensing data can be used to support soil mapping and to indicate soil characteristics on the landscape scale. This article focuses on the spatial prediction of the total carbon and nitrogen content and of physical soil properties such as topsoil silt, sand and clay content, topsoil depth and plough pan thickness. Correlation analyses indicate that, on the one side, the distribution of C, N and silt contents is quite closely related to the NDVI of vegetated surfaces and that, on the other side, it corresponds significantly to terrain attributes such as relative elevation, elevation above nearest drainage channel and topographical wetness index. Geostatistical analyses furthermore reflect a moderately structured spatial correlation of these soil variables. The combined use of the above mentioned terrain variables and the NDVI in a multiple linear regression accounted for 29% (silt) to 41% (total C) of the variance of these soil properties. In order to select the best prediction method to accurately map soil property distribution, we compared the performance of different regionalization techniques, such as multi-linear regression, simple kriging, inverse distance to a power, ordinary kriging and regression kriging. Except for the prediction of topsoil clay content, in all cases regression kriging model “C” performed best. Compared to simple kriging, the spatial prediction was improved by up to 14% (total C), 13% (total N) and 10% (silt). Since the autocorrelation lengths of these spatially well correlated soil variables range between three and five times the soil sampling density, we consider regression kriging model “C” to be a suitable method for reducing the soil sampling density. It should help to save time and costs when doing soil mapping on the landscape scale, even in intensively used paddy soil landscapes.     

Staying in situ or shifting range under ongoing climate change: A case of an endemic herb in the Himalaya-Hengduan Mountains across elevational gradients

Aim

How species respond to ongoing climate change has been a hot research topic, especially with the controversy in shifting range (movement) or persisting in local habitat (in situ) as the primary response. Assessing the relative roles of range shifts, phenotypic plasticity and genetic adaptation helps us predict the evolutionary fate of species. We aim to explore the evolutionary strategies of plants under climate change from a keystone herb in alpine ecosystems, Mirabilis himalaica, along its elevational gradient.

Location

Himalaya-Hengduan Mountains, China.

Methods

We combined evidence from population genomics and ecological data in both space and time to investigate the state of “staying” or “moving”. We identified migration events by assessing historical and contemporary gene flow and changes in species distribution. Morphological variation was compared by measuring five traits using specimen data. Moreover, we explored climate-driven genetic variation and local selection regimes acting on populations in the alpine landscape along an elevational gradient.

Results

Our results argue that staying in situ by morphological variation and local genetic evolution rather than range shifting plays an important role in M. himalaica response to climate change. We first found trace evidence of upward or climatic-driven shifting along an elevational gradient, although asymmetric gene flow was restricted within microenvironments of mid-elevational populations. Furthermore, morphological variation comparisons revealed clinal variation, as resource allocation showed a declining pattern in vegetative growth but increased reproductive growth with increasing elevation. Outlier tests and environment association analyses indicated adaptative loci primarily related to thermal-driven selection and continuous adaptations to high elevation in the Himalaya-Hengduan Mountains.

Main Conclusions

Our findings show M. himalaica may persist in local habitats rather than shifting range under climate change, exhibiting a low risk of genomic vulnerability in current habitats. This study has important implications in improving our understanding of the evolutionary response in alpine plants to climate change.