Ulrike Tappeiner

Impact of land use changes on mountain vegetation

Abstract In this study the impact of land use changes on vegetation in the sub-alpine-alpine belt is analysed. The study sites (4.7 km2) are located in the Passeier Valley (South Tyrol, Italy), at an elevation of 1500–2300 m a.s.l. The whole study area was used for hay-making ca. 60 yr ago. Today, part of the meadows are more intensively used, while other parts have been converted to pasture or have been abandoned. We analysed the reasons for these land use changes and the effects on vegetation with a Geographical Information System and geostatistical analysis. The result of these analyses are: (1) Current land use is mainly controlled by the degree of accessibility for vehicles. Accessible areas are being used more and more intensively, while poorly accessible areas are being abandoned or used as pasture. (2) Current vegetation is highly determined by current land use. Particular vegetation units can be assigned to each form of land use. (3) Succession starts immediately after abandonment. Depending on altitude, succession proceeds at different speeds and with different numbers of stages. Hence the type of vegetation indicates the time passed since abandonment. (4) Land use changes lead to characteristic changes in vegetation; they are considered to be the most important driving force for vegetation change. (5) Measures of intensification and abandonment of extensively used areas both lead to a decrease in the number of species. Nomenclature: Adler et al. (1994).

Seasonal and inter-annual variability of the net ecosystem CO2 exchange of a temperate mountain grassland : Effects of weather and management

The role and relative importance of climate and cutting for the seasonal and inter-annual variability of the net ecosystem CO2 (NEE) of a temperate mountain grassland was investigated. Eddy covariance CO2 flux data and associated measurements of the green area index and the major environmental driving forces acquired during 2001-2006 at the study site Neustift (Austria) were analyzed. Driven by three cutting events per year which kept the investigated grassland in a stage of vigorous growth, the seasonal variability of NEE was primarily modulated by gross primary productivity (GPP). The role of environmental parameters in modulating the seasonal variability of NEE was obscured by the strong response of GPP to changes in the amount of green area, as well as the cutting-mediated decoupling of phenological development and the seasonal course of climate drivers. None of the climate and management metrics examined was able to explain the inter-annual variability of annual NEE. This is thought to result from (1) a high covariance between GPP and ecosystem respiration (Reco) at the annual time scale which results in a comparatively small inter-annual variation of NEE, (2) compensating effects between carbon exchange during and outside the management period, and (3) changes in the biotic response to rather than the climate variables per se. GPP was more important in modulating inter-annual variations in NEE in spring and before the first and second cut, while Reco explained a larger fraction of the inter-annual variability of NEE during the remaining, in particular the post-cut, periods.

Relative contributions of plant traits and soil microbial properties to mountain grassland ecosystem services.

Summary 1. Plant functional diversity and soil microbial community composition are tightly coupled. Changes in these interactions may influence ecosystem functioning. Links between plant functional diversity, soil microbial communities and ecosystem functioning have been demonstrated in experiments using plant monocultures and mixtures, using broad plant and microbial functional groups, but have not been examined in diverse natural plant communities. 2. We quantified the relative effects of plant and microbial functional properties on key ecosystem functions. We measured plant functional diversity, soil microbial community composition and parameters associated with nitrogen (N) cycling and key nutrient cycling processes at three grassland sites in different parts of Europe. Because plant structure and function strongly influence soil microbial communities, we determined relationships between ecosystem properties, plant traits and soil community characteristics following a sequential approach in which plant traits were fitted first, followed by the additional effects of soil micro-organisms. 3. We identified a continuum from standing green biomass and standing litter, linked mostly with plant traits, to potential N mineralization and potential leaching of soil inorganic N, linked mostly with microbial properties. Plant and microbial functional parameters were equally important in explaining % organic matter content in soil. A parallel continuum ran from plant height, linked with above-ground biomass, to plant quality effects captured by the leaf economics spectrum, which were linked with the recycling of carbon (C) and N. 4. More exploitative species (higher specific leaf area, leaf N concentrations and lower leaf dry matter content) and taller swards, along with soil microbial communities dominated by bacteria, with rapid microbial activities, were linked with greater fodder production, but poor C and N retention. Conversely, dominance by conservative species (with opposite traits) and soil microbial communities dominated by fungi, and bacteria with slow activities, were usually linked with low production, but greater soil C storage and N retention. 5. Synthesis – Grassland production, C sequestration and soil N retention are jointly related to plant and microbial functional traits. Managing grasslands for selected, or multiple, ecosystem services will thus require a consideration of the joint effects of plant and soil communities. Further understanding of the mechanisms that link plant and microbial functional traits is essential to achieve this.

Site and management effects on soil microbial properties of subalpine meadows : a study of land abandonment along a north-south gradient in the European Alps

We studied the factors which regulate microbial community organization in soils of managed ecosystems. Soil microbial biomass C and N (SMBC, SMBN), EC/ENIN ratio, ergosterol, and phospholipid fatty acids (PLFA) were determined in organically fertilised meadows and grasslands with abandoned management at three sites (Stubai Valley, Passeier Valley, and Monte Bondone) to study the relative importance of the factors site and management in governing the variability of soil microbial biomass and community structure in subalpine grasslands of the European Alps. Our data provide evidence that management abandonment has important effects on the structure of the soil microbial biomass, namely an increase in the fungal biomass. SMBC, SMBN, EC/ENIN ratio and ergosterol contents differed significantly between sites. SMBC was similar in abandoned and managed grasslands, whereas SMBN was lower and ergosterol contents were higher in abandoned grasslands as compared to managed meadows. We concluded that the impact of management abandonment on soil microbial biomass was of relatively less importance than effects of site and sampling time, and the effect of abandonment may be better detected at the community scale of resolution.

Effects of land use in alpine grasslands on the probability of landslides

Abstract Landslides in topsoils, locally known as ‘Blaiken’, are caused by a set of factors which determine the probability of such slides. Apart from bedrock, relief and climate, the geomorphological changes in connection with land use, as well as vegetation and soil changes may influence landslides in alpine cultural landscapes. Within the framework of the EU project INTEGRALP (INTERREG II), the risk of erosion due to changes in land use within subalpine-alpine study sites was investigated (Passeier Valley, South Tyrol, Italy; Stubai Valley, North Tyrol, Austria). 42 potential factors were analysed in eroded and also in non-eroded areas. The factors included geomorphological, pedological, phytosociological and land-use characters. The statistical evaluation of the data was carried out via step-wise logistical regression. Twelve factors made a statistically significant contribution to the probability of landslides, and about 97% of the samples could be correctly categorised by using these factors. Apart from exposition, inclination and soil depth, land use was an important factor to landslides in topsoils. Managed meadows and pastures were significantly less erodible than abandoned grasslands. However, not the land-use activities themselves lead to changes in erosion risks, but rather the direct or indirect effects on vegetation and soil properties. They include relative cover of grasses, herbs and dwarf shrubs as well as the total root length and the rooting density in main fracture depth. Translationsbodenrutschungen, allgemein unter dem Begriff “Blaiken” zusammengefasst, werden wie alle Erosionsformen von einem Ursachenkomplex gesteuert. Neben der Geologie, der Gelandemorphologie und dem Klima tragen in der alpinen Kulturlandschaft hauptsachlich die mit der Bewirtschaftung zusammenhangenden geomorphologischen Veranderungen, sowie Vegetations- und Bodenveranderungen entscheidend bei. Im Rahmen des EU-Projektes INTEGRALP (INTERREG II) wurde die Modifikation des Erosionsrisikos infolge von Bewirtschaftungsanderungen in zwei subalpin-alpinen Untersuchungsgebieten (Passeiertal, Sudtirol, Italien; Stubaital, Nordtirol, Osterreich) analysiert. Fur die Bestimmung der Zusammenhange wurden in erosionsgefahrdeten und nicht erosionsgefahrdeten Bereichen insgesamt 42 mogliche Einflussfaktoren erhoben. Unter diesen waren gelandemorphologische, bodenkundliche, vegetationskundliche Faktoren sowie mehrere Bewirtschaftungsfaktoren. Die statistische Auswertung der Daten erfolgte uber die schrittweise logistische Regression. Von den 23 unabhangigen Einflussgrosen erwiesen sich 12 Faktoren als statistisch signifikant, wobei durch diese Grosen insgesamt 97% der Stichproben richtig zugeordnet werden konnten. Das Ergebnis zeigt, dass fur das Entstehen von Translationsbodenrutschungen neben der Exposition, der Hangneigung und der Bodentiefe hauptsachlich die Bewirtschaftung ausschlaggebend ist. Sowohl Mahwiesen als auch Weideflachen sind deutlich weniger erosionsgefahrdet als Brachen. Es sind jedoch nicht die Nutzungsaktivitaten an sich, die zu einer Veranderung des Erosionsrisikos fuhren, sondern vielmehr die damit direkt oder indirekt verbundenen Vegetations- bzw. Bodenveranderungen. Zu diesen zahlen die relative Deckung der Graser, der Zwergstraucher, die Gesamtdurchwurzelung des Bodens sowie die mittlere Durchwurzelungsdichte in der Hauptanbruchstiefe.

Plant diversity declines with recent land use changes in European Alps

Against a background of increasing land use intensification on favorable agricultural areas and land abandonment on less arable areas in the Alps, the aim of this investigation was to detect whether and how 10 differently used types of grassland can be distinguished by site factors, plant species composition, and biodiversity. By using a very large number of vegetation surveys (936) that were widely distributed in the Central Alps, site parameters and species composition of the different land use types were compared by discriminant analyses and various biodiversity indices. Results showed that land use is a significant factor affecting the development of different grassland communities with site factors playing a subordinate, yet important role. The 10 land use types studied can be clearly differentiated from one another by single species as well as by species composition. Our study found that the number of plant communities along with the number of species decreases constantly and significantly with increasing land use intensity and on abandoned land. For example, on average, extensively used meadows have more than three times as many species as intensively used meadows. Further, the most even distribution of species (Evenness index) is reached in intensively used meadows, whereas on pastures and abandoned land, some species become dominant forcing other species to recede. The results confirm that due to current trends in agriculture, such as land abandonment and land use intensification, plant diversity in the Alps is decreasing considerably.

Modelling vegetation patterns using natural and anthropogenic influence factors: preliminary experience with a GIS based model applied to an Alpine area

A modelling approach based on discriminant analysis and the GIS (geographical information system) is presented with the aim of identifying the influence of environmental parameters and human impact on the Alpine cultural landscape. For testing the model we used the vegetation patterns of an area of 5 km2 between 1300 and 2300 m above sea level in the Central Alps (Passeier Valley, Italy). The overall prediction for the highly heterogeneous vegetation (a total of 21 different vegetation units characterized by high biodiversity) is in the order of 78% (pixel to pixel correspondence), the probability of correct classification by chance is only 21%. Only two vegetation units were totally misclassified, whereas six were classified correctly at almost 100%, a further seven at 60–80% and the remaining six at 20–50%. The proportion of unexplained variability in the research area may to some degree be attributed to the snow distribution pattern and to the use of a more detailed scale of spatial grazing habits. The most important lack of information, however, concerns land use history. Simulation analysis shows that human impact and elevation exert a major influence on the vegetation, whereas hydrological parameters and radiation do not greatly affect biodiversity and vegetation patterns in the study area.

Impact of land-use change on nitrogen mineralization in subalpine grasslands in the Southern Alps

Abstract A field study was conducted to investigate the effect of abandonment of management on net N mineralization (NNM) in subalpine meadows. NNM, soil microbial biomass N (SMBN), fungal biomass and physicochemical characteristics (total C, total N, dissolved organic carbon (DOC) and pH) were determined in surface (0–10 cm) soil from May to October 1997 in an intensively managed and an abandoned meadow at 1770 m a.s.l.. The cumulative NNM was lower in the abandoned area and ranged from 150 to 373 and from 25 to 85 μg N g–1 soil in the intensively managed and the abandoned areas, respectively. The total organic C increased in the abandoned area, while total N showed no difference between abandoned and managed meadow. SMBN showed no difference between the investigated sites, whereas ergosterol, a measure of fungal biomass, increased significantly at the abandoned site. The cumulative NNM was negatively correlated with total organic C, C : N ratio, DOC and ergosterol content, and positively correlated with the NH4+-N content of soil. The decrease in NNM at the abandoned site may be explained by the lower availability of N in substrates characterized by a high C : N ratio which, together with a decrease in pH in the litter layer, may have increased fungal biomass.

GIS-based modelling of spatial pattern of snow cover duration in an alpine area

Snow cover duration patterns of an alpine hillslope (approximately 2 km 2 ) were derived using daily terrestrial photographic remote sensing. We have developed a suite of quantitative models in order to investigate the relative controls of topographic factors, the degree of non-linearity, the effect of seasonal differences and a possible influence of further systematic influences. We have only used data that are relatively easily available to ensure applicability beyond the site. Elevation, slope angle and aspect, and potential irradiation for the winter period can be directly derived from a digital elevation model. The number of days with temperature 0°C was included using a regression with elevation. Furthermore, a coarse vegetation classification (forested/not forested) was included. To estimate the necessary degree of non-linearity for such modelling without forming exact assumption about the functional interrelations, results from a linear regression analysis are compared with an artificial neural network (ANN). The results show that a R 2 of 71% can be achieved by means of a linear approach, whereas a non-linear approach (ANN) leads to 81%. An indirect estimation demonstrates that a further 6% can be explained without considering data on annually specific weather conditions. The analysis of the residuals shows a clear spatial pattern. This indicates that additional spatial variables may allow a further improvement of the model.

On the Effects of Scale for Ecosystem Services Mapping

Ecosystems provide life-sustaining services upon which human civilization depends, but their degradation largely continues unabated. Spatially explicit information on ecosystem services (ES) provision is required to better guide decision making, particularly for mountain systems, which are characterized by vertical gradients and isolation with high topographic complexity, making them particularly sensitive to global change. But while spatially explicit ES quantification and valuation allows the identification of areas of abundant or limited supply of and demand for ES, the accuracy and usefulness of the information varies considerably depending on the scale and methods used. Using four case studies from mountainous regions in Europe and the U.S., we quantify information gains and losses when mapping five ES - carbon sequestration, flood regulation, agricultural production, timber harvest, and scenic beauty - at coarse and fine resolution (250 m vs. 25 m in Europe and 300 m vs. 30 m in the U.S.). We analyze the effects of scale on ES estimates and their spatial pattern and show how these effects are related to different ES, terrain structure and model properties. ES estimates differ substantially between the fine and coarse resolution analyses in all case studies and across all services. This scale effect is not equally strong for all ES. We show that spatially explicit information about non-clustered, isolated ES tends to be lost at coarse resolution and against expectation, mainly in less rugged terrain, which calls for finer resolution assessments in such contexts. The effect of terrain ruggedness is also related to model properties such as dependency on land use-land cover data. We close with recommendations for mapping ES to make the resulting maps more comparable, and suggest a four-step approach to address the issue of scale when mapping ES that can deliver information to support ES-based decision making with greater accuracy and reliability.