Floristic diversity in the transition from traditional to modern land-use in southern Sweden A.D. 1800-2008

International audienceWe aim to provide a long-term ecological analysis of land-use and floristic diversity in the transition from traditional to modern land-use management in the time A.D. 1800-2008 in southern Sweden. We use the Regional Estimates of Vegetation Abundance from Large Sites (REVEALS) model to quantify land-cover changes on a regional scale at 20-year intervals, based on the fossil pollen record. Floristic richness and evenness are estimated using palynological richness and the Shannon index applied to the REVEALS output, respectively. We identified a transition period of 60 years between 1880 and 1940 when the total tree cover increased and the tree composition changed from deciduous to coniferous dominance. Within the shrinking area of open land, arable land taxa expanded, while the number and coverage of herbs in the remaining grasslands decreased. The succession from open grasslands to more tree-covered habitats initially favoured palynological richness, which reached its highest values during the first 40 years of the transition period. The highest REVEALS-based evenness was recorded in the time of traditional land-use and at the beginning of the transition period, reflecting higher habitat diversity at these time intervals. Our results support a more dynamic ecosystem management that changes between traditional land-use and phases of succession (\40 years) to promote floristic diversity. We have developed and applied a palaeoecological methodology that contributes realistic estimates to be used in ecosystem management

The impact of land-use change on floristic diversity at regional scale in southern Sweden 600 BC-AD 2008

International audienceThis study explores the relationship between landuse and floristic diversity between 600BC and AD2008 in the uplands of southern Sweden. We use fossil pollen assemblages and the Regional Estimates of Vegetation Abundance from Large Sites (REVEALS) model to quantitatively reconstruct land cover at a regional scale. Floristic richness and evenness are estimated using palynological richness and REVEALS-based evenness, respectively. We focus on the period AD350 to 750 to investigate the impact of an inferred, short-lived (<200 yr) period of land-use expansion and subsequent land abandonment on vegetation composition and floristic diversity. The observed vegetation response is compared to that recorded during the transition from traditional to modern land-use management at the end of the 19th century. Our results suggest that agricultural land use was most widespread between AD350 and 1850, which correlates broadly with high values of palynological richness. REVEALS-based evenness was highest between AD500 and 1600 which indicates a more equal cover among taxa during this time interval. Palynological richness increased during the inferred land-use expansion after AD350 and decreased during the subsequent regression AD550-750, while REVEALS-based evenness increased throughout this period. The values of palynological richness during the last few decades are within the range observed during the last 1650 yr. However, REVEALS-based evenness shows much lower values during the last century compared to the previous ca. 2600 yr, which indicates that the composition of presentday vegetation is unusual in a millennial perspective. Our results show that regional scale changes in land use have had clear impacts on floristic diversity in southern Sweden, with a vegetation response time of less than 20 to 50 yr. We show the importance of traditional land use to attain high biodiversity and suggest that ecosystem management should include a regional landscape perspective

Random-time processes governed by differential equations of fractional distributed order

We analyze here different types of fractional differential equations, under the assumption that their fractional order $\nu \in (0,1]$ is random\ with probability density $n(\nu).$ We start by considering the fractional extension of the recursive equation governing the homogeneous Poisson process $N(t),t>0.$\ We prove that, for a particular (discrete) choice of $n(\nu)$, it leads to a process with random time, defined as $N(\widetilde{\mathcal{T}}_{\nu_{1,}\nu_{2}}(t)),t>0.$ The distribution of the random time argument $\widetilde{\mathcal{T}}_{\nu_{1,}\nu_{2}}(t)$ can be expressed, for any fixed $t$, in terms of convolutions of stable-laws. The new process $N(\widetilde{\mathcal{T}}_{\nu_{1,}\nu_{2}})$ is itself a renewal and can be shown to be a Cox process. Moreover we prove that the survival probability of $N(\widetilde{\mathcal{T}}_{\nu_{1,}\nu_{2}})$, as well as its probability generating function, are solution to the so-called fractional relaxation equation of distributed order (see \cite{Vib}%). In view of the previous results it is natural to consider diffusion-type fractional equations of distributed order. We present here an approach to their solutions in terms of composition of the Brownian motion $B(t),t>0$ with the random time $\widetilde{\mathcal{T}}_{\nu_{1,}\nu_{2}}$. We thus provide an alternative to the constructions presented in Mainardi and Pagnini \cite{mapagn} and in Chechkin et al. \cite{che1}, at least in the double-order case.Comment: 26 page

Pollen-based quantitative reconstructions of Holocene regional vegetation cover (plant-functional types and land-cover types) in Europe suitable for climate modelling

We present quantitative reconstructions of regional vegetation cover in north-western Europe, western Europe north of the Alps, and eastern Europe for five time windows in the Holocene [around 6k, 3k, 0.5k, 0.2k, and 0.05k calendar years before present (bp)] at a 1 degrees x1 degrees spatial scale with the objective of producing vegetation descriptions suitable for climate modelling. The REVEALS model was applied on 636 pollen records from lakes and bogs to reconstruct the past cover of 25 plant taxa grouped into 10 plant-functional types and three land-cover types [evergreen trees, summer-green (deciduous) trees, and open land]. The model corrects for some of the biases in pollen percentages by using pollen productivity estimates and fall speeds of pollen, and by applying simple but robust models of pollen dispersal and deposition. The emerging patterns of tree migration and deforestation between 6k bp and modern time in the REVEALS estimates agree with our general understanding of the vegetation history of Europe based on pollen percentages. However, the degree of anthropogenic deforestation (i.e. cover of cultivated and grazing land) at 3k, 0.5k, and 0.2k bp is significantly higher than deduced from pollen percentages. This is also the case at 6k in some parts of Europe, in particular Britain and Ireland. Furthermore, the relationship between summer-green and evergreen trees, and between individual tree taxa, differs significantly when expressed as pollen percentages or as REVEALS estimates of tree cover. For instance, when Pinus is dominant over Picea as pollen percentages, Picea is dominant over Pinus as REVEALS estimates. These differences play a major role in the reconstruction of European landscapes and for the study of land cover-climate interactions, biodiversity and human resources.Peer reviewe

Holocene land-cover reconstructions for studies on land cover-climate feedbacks

Peer reviewe

Exploring the patterns and causes of land use changes in south-west Sweden

To study the causes of agricultural declines in south-west Sweden, a multi-proxy study including pollen analysis, bog surface wetness indicators and aeolian sediment influx reconstructions was carried out on the Store Mosse Bog, situated on the coastal plain of Halland. Patterns of agricultural changes during the past 6,000 years from this study were compared to one additional site on the coastal plain (Undarsmosse Bog) and to four sites in the forested upland region. First, we compared land use activity on the coastal plain and in upland regions of south-west Sweden. Three periods with reduced agricultural activities were observed, primarily in records from the coastal plain. Next, the causes for these declines were studied by comparing land use indicators in the pollen records from the Store Mosse and Undarsmosse peat bogs to independent climatic reconstructions based on the same core material (past storm activity based on aeolian sediment influx onto the peat bogs; bog surface wetness reconstructed from organic bulk density measurements). Since the climatic reconstructions and pollen analysis were carried out on the same peat cores, a direct comparison between the timing of climatic events and land use changes was possible. Results indicate that climatic perturbations prior to ca. 1,000 years ago contributed to or possibly caused agricultural declines. The agricultural expansions near the Store Mosse and Undarsmosse bogs from 3000 to 2600 cal. yrs b.p. ended at the time when climatic proxy indicators recorded climatic instability (from ca 2600 to 2200 cal. yrs b.p.). The same sequence of events was recorded around 1500 cal. yrs b.p. and from 1200 to 1000 cal. yrs b.p., suggesting a climatic cause for these agricultural declines as well. The well-known climatic perturbations associated with the Little Ice Age, however, did not have a visible impact on agricultural activities. By this time, advances in land use knowledge and technology may have drastically diminished society's sensitivity to climatic changes

Temporal cultural landscape dynamics in a marginal upland area: agricultural expansions and contractions inferred from palynological evidence at Yttra Berg, southern Sweden

Agrarian history and local cultural landscape dynamics have been documented through pollen analysis of a peat core within the hamlet of Yttra Berg, which is situated in an upland area of southwest Sweden. The sequence covers the last 5,000 years, from Neolithic to modern time. Wood pasturing started at 2000 b.c., followed by grazing and small-scale cultivation with 500 year cycles from 650 b.c., and permanent fields of agriculture from a.d. 1150. The area was abandoned during the period a.d. 1350-1550. Three cycles of succession related to land-use have been identified for the period 650 b.c. to a.d. 1550. Correlation with frequent clearance cairns in the area is discussed. Recessions of agriculture/settlement during the late Middle Ages and late modern time are documented. Pollen data indicate increased landscape and plant diversity since the Neolithic, closely linked to openness of the agrarian landscape. These results are important for landscape restoration

Regional and local vegetation reconstructions-applications for revealing biodiversity dynamics

International audienceHow has land use and land cover changed on different temporal and spatial scales, and how have these changes influenced biodiversity during the last 3000 years? Our working hypothesis is that biodiversity is favoured by variations in intensity and frequency of human activities such as clearing of forests, increased grazing and abandonment caused by population reduction due to e.g. epidemics or wars. To test the hypothesis, itis crucial to obtain records of vegetation changes with detailed time resolution and, moreover, to be able to set the spatial scale.Our study area is located in Småland in southern Sweden, and high resolution pollen analyses of sediment cores from large and small lakes are used for quantitative reconstruction of past land cover. Here we present our project and the primary methods that will be used. We also present some preliminary results and the following steps in the project

Farm establishment, abandonment and agricultural practices during the last 1,300 years: a case study from southern Sweden based on pollen records and the LOVE model

International audienc