Ralf Jahn - Academia.edu (original) (raw)

Papers by Ralf Jahn

Research paper thumbnail of Euro+Med-Checklist Notulae, 3

Willdenowia, 2014

Raab-Straube E. von & Raus Th. (ed.

Research paper thumbnail of An inventory of the vascular plants and bryophytes of Gavdopoula island (S Aegean, Greece) and its phytogeographical significance

Willdenowia, 2011

BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access t... more BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses.

Research paper thumbnail of New and validated high-rank syntaxa from Europe

In the course of the compilation of a checklist of the high-rank syntaxa of Europe, it turned out... more In the course of the compilation of a checklist of the high-rank syntaxa of Europe, it turned out that for several syntaxa no valid and le-gitimate names were available. With this contribution, we aim to solve some of the problems by publishing or validating seven syntaxon names (1 order, 5 alliances, 1 association) and by proposing a nomen novum for one illegitimate alliance name. The validations concern the Artemisio albi-Brometalia erecti (Festuco-Brometea; xerophytic basiphilous grasslands in subatlantic-submediterranean Europe), Dictamno albi-Ferulagion galbaniferae (Antherico ramosi-Geranietalia sanguinei, Trifolio-Geranietea sanguinei; xerophytic basiphilous forest-edge communities of the Balkans and the SE Alps), Euphorbio taurinensis-Geranion lucidi (Geranio-Cardaminetalia hirsutae, Stellarietea mediae; short-lived nitrophilous forest-edge communities of Macedonia), and Gentianello amarellae-Helictotrichion pratensis (Brometalia erecti, Festuco-Brometea; meso-xerophytic bas...

Research paper thumbnail of The vascular flora of Crete and adjacent islets has been tbe object of many floristic studies during the last decades. The currently known numbers of taxa are given in Table I

Research paper thumbnail of Quantified ecology and co-occurrence of Mediterranean woody species in a landscape context

Research paper thumbnail of Reciprocal extrapolation of species distribution models between two islands – Specialists perform better than generalists and geological data reduces prediction accuracy

Ecological Indicators

Abstract This study aims to test the extrapolation effects of species distribution models (SDM) u... more Abstract This study aims to test the extrapolation effects of species distribution models (SDM) using three groups of predictor variables: climate, relief and geology (bedrock type). We highlight potential ecological differences for selected taxa, regarding both generalists and specialists in terms of edaphic conditions. We used distributional data of 12 woody species shared by two large Mediterranean islands (Crete and Sicily) to calibrate Maxent models of their potential distribution. We trained models with data from Crete and extrapolated to Sicily and vice versa. We tested ten proxies for the three variable groups and compared AUC values as a measure of model performance. Extrapolation of SDMs worked fairly well across species and islands for those models including climatic and relief data, while those including geological information performed worse for the tested species. Edaphic generalists performed less well compared to edaphic specialists. The latter performed best with climate data included in models and more poorly with only geological data. This may be due to differences in bedrock type affinities of species between the two islands.

Research paper thumbnail of New and validated high-rank syntaxa from Europe

Lazaroa, 2009

Mucina, L., Dengler, J., Bergmeier, E., Čarni, A., Dimopoulos, P., Jahn, R. & Matevski, V. New an... more Mucina, L., Dengler, J., Bergmeier, E., Čarni, A., Dimopoulos, P., Jahn, R. & Matevski, V. New and validated high-rank syntaxa from Europe. Lazaroa 30: 267-276 (2009).

Research paper thumbnail of New and validated high-rank syntaxa from Europe

Lazaroa, 2009

Mucina, L., Dengler, J., Bergmeier, E., Čarni, A., Dimopoulos, P., Jahn, R. & Matevski, V. New an... more Mucina, L., Dengler, J., Bergmeier, E., Čarni, A., Dimopoulos, P., Jahn, R. & Matevski, V. New and validated high-rank syntaxa from Europe. Lazaroa 30: 267-276 (2009).

Research paper thumbnail of New and validated high-rank syntaxa from Europe

Research paper thumbnail of Exkursionsflora für Kreta

ABSTRACT Full text not available.

Research paper thumbnail of The phytodiversity of the flora of Kriti (Greece) - a survey of the current state of knowledge

Research paper thumbnail of Flora and vegetation of Gávdos (Greece), the southernmost European island. I. Vascular flora and chorological relations

Research paper thumbnail of New and validated high-rank syntaxa from Europe

Mucina, L., Dengler, J., Bergmeier, E., Čarni, A., Dimopoulos, P., Jahn, R. & Matevski, V. New an... more Mucina, L., Dengler, J., Bergmeier, E., Čarni, A., Dimopoulos, P., Jahn, R. & Matevski, V. New and validated high-rank syntaxa from Europe. Lazaroa 30: 267-276 (2009).

Research paper thumbnail of An inventory of the vascular plants and bryophytes of Gavdopoula island (S Aegean, Greece) and its phytogeographical significance

Willdenowia, 2011

Bergmeier E., Blockeel T., Böhling N., Fournaraki C., Gotsiou P., Jahn R., Lansdown R. & Turland ... more Bergmeier E., Blockeel T., Böhling N., Fournaraki C., Gotsiou P., Jahn R., Lansdown R. & Turland N.: An inventory of the vascular plants and bryophytes of Gavdopoula island (S Aegean, Greece) and its phytogeographical significance. -Willdenowia 41: 179 -190. -Online ISSN 1868-6397; © 2011 BGBM Berlin-Dahlem. Gavdopoula is an island of 177.5 ha in the S Aegean, near the southeasternmost point of Europe. Based on field excursions in 1998/99 and 2009/10, we provide an annotated floristic catalogue of 186 vascular plant and 13 bryophyte taxa, with a full record of herbarium specimens and field observations, being the first botanical inventory of the island. Species richness in relation to island area is, as shown in a diagram, according to expectations. Among the vascular plants there are six regional ('Cretan area') endemics. The Saharo-Arabian-S Mediterranean phytogeographical element is well represented, with several species confined in Greece or even in Europe to the small islands south of Crete. Of these, Atriplex mollis occurs in Europe only on Gavdopoula. The moss Entosthodon commutatus has not previously been recorded from the E Mediterranean. The vegetation is controlled chiefly by the dry Mediterranean climate, calcareous shallow soils, sea spray and seasonal grazing. It consists of halo-nitrophytic and Pistacia lentiscus scrub, two types of phrygana, small-scale ephemeral pastures with winter-annuals on red-loamy soils, and sea-cliff vegetation. The new combination, Lysimachia arvensis var. caerulea, is published.

Research paper thumbnail of Flora and phytogeographical significance of the islands Chrisi, Koufonisi and nearby islets (S Aegean, Greece

Bergmeier, E., Kypriotakis, Z., Jahn, R., Böhling, N., Dimopoulos, P., Raus, Th. & Tzanoudakis, D... more Bergmeier, E., Kypriotakis, Z., Jahn, R., Böhling, N., Dimopoulos, P., Raus, Th. & Tzanoudakis, D.: Flora and phytogeographical significance of the islands Chrisi, Koufonisi and nearby islets (S Aegean, Greece). -Willdenowia 31: 329-356. 2001. -ISSN 0511-9618. An annotated floristic catalogue is provided for the islands Chrisi (Gaidouronisi), Koufonisi and the nearby islets Mikronisi, Strongili, Makrouli and Trachilos, all off SE Kriti. Critical use is made of literature data, and hitherto unpublished records, mostly from 1997 through 2000, add substantially to the first full vascular plant inventory of the islands. The total numbers of vascular plant taxa currently known from each island are as follows (accepted taxon records from literature, if extant, in brackets): Chrisi 275 (162), Mikronisi 71 (21), Koufonisi 273 (71), Strongili 110, Makrouli 115, Trachilos 96. Most noteworthy are Suaeda palaestina and Ononis vaginalis (currently with their single localities in Europe); Allium brachyspathum, Astragalus boeticus, A. peregrinus, Galium recurvum, Hippocrepis unisiliquosa, Lagurus ovatus subsp. nanus, Ononis diffusa, Orobanche grisebachii, Schoenoplectus litoralis (new records or confirmations for the Cretan area as a whole, or for the territory of Kriti proper including offshore islands); and Chlamydophora tridentata, Frankenia corymbosa and Hymenolobus procumbens (new regional records for the E part of Kriti and its offshore islands). The N African, pronouncedly thermophilous phytogeographical element is fairly well represented in the investigated area, thence Koufonisi in particular must be considered the driest and hottest SE European island. The principal habitats encountered in each of the islands are outlined and the present conditions for nature conservation discussed.

Research paper thumbnail of The Cerastium scaposum group (Caryophyllaceae): three annual taxa endemic to Crete (Greece), two of them new

Research paper thumbnail of Euro+Med-Checklist Notulae, 3

Willdenowia, 2014

Raab-Straube E. von & Raus Th. (ed.

Research paper thumbnail of An inventory of the vascular plants and bryophytes of Gavdopoula island (S Aegean, Greece) and its phytogeographical significance

Willdenowia, 2011

BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access t... more BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses.

Research paper thumbnail of New and validated high-rank syntaxa from Europe

In the course of the compilation of a checklist of the high-rank syntaxa of Europe, it turned out... more In the course of the compilation of a checklist of the high-rank syntaxa of Europe, it turned out that for several syntaxa no valid and le-gitimate names were available. With this contribution, we aim to solve some of the problems by publishing or validating seven syntaxon names (1 order, 5 alliances, 1 association) and by proposing a nomen novum for one illegitimate alliance name. The validations concern the Artemisio albi-Brometalia erecti (Festuco-Brometea; xerophytic basiphilous grasslands in subatlantic-submediterranean Europe), Dictamno albi-Ferulagion galbaniferae (Antherico ramosi-Geranietalia sanguinei, Trifolio-Geranietea sanguinei; xerophytic basiphilous forest-edge communities of the Balkans and the SE Alps), Euphorbio taurinensis-Geranion lucidi (Geranio-Cardaminetalia hirsutae, Stellarietea mediae; short-lived nitrophilous forest-edge communities of Macedonia), and Gentianello amarellae-Helictotrichion pratensis (Brometalia erecti, Festuco-Brometea; meso-xerophytic bas...

Research paper thumbnail of The vascular flora of Crete and adjacent islets has been tbe object of many floristic studies during the last decades. The currently known numbers of taxa are given in Table I

Research paper thumbnail of Quantified ecology and co-occurrence of Mediterranean woody species in a landscape context

Research paper thumbnail of Reciprocal extrapolation of species distribution models between two islands – Specialists perform better than generalists and geological data reduces prediction accuracy

Ecological Indicators

Abstract This study aims to test the extrapolation effects of species distribution models (SDM) u... more Abstract This study aims to test the extrapolation effects of species distribution models (SDM) using three groups of predictor variables: climate, relief and geology (bedrock type). We highlight potential ecological differences for selected taxa, regarding both generalists and specialists in terms of edaphic conditions. We used distributional data of 12 woody species shared by two large Mediterranean islands (Crete and Sicily) to calibrate Maxent models of their potential distribution. We trained models with data from Crete and extrapolated to Sicily and vice versa. We tested ten proxies for the three variable groups and compared AUC values as a measure of model performance. Extrapolation of SDMs worked fairly well across species and islands for those models including climatic and relief data, while those including geological information performed worse for the tested species. Edaphic generalists performed less well compared to edaphic specialists. The latter performed best with climate data included in models and more poorly with only geological data. This may be due to differences in bedrock type affinities of species between the two islands.

Research paper thumbnail of New and validated high-rank syntaxa from Europe

Lazaroa, 2009

Mucina, L., Dengler, J., Bergmeier, E., Čarni, A., Dimopoulos, P., Jahn, R. & Matevski, V. New an... more Mucina, L., Dengler, J., Bergmeier, E., Čarni, A., Dimopoulos, P., Jahn, R. & Matevski, V. New and validated high-rank syntaxa from Europe. Lazaroa 30: 267-276 (2009).

Research paper thumbnail of New and validated high-rank syntaxa from Europe

Lazaroa, 2009

Mucina, L., Dengler, J., Bergmeier, E., Čarni, A., Dimopoulos, P., Jahn, R. & Matevski, V. New an... more Mucina, L., Dengler, J., Bergmeier, E., Čarni, A., Dimopoulos, P., Jahn, R. & Matevski, V. New and validated high-rank syntaxa from Europe. Lazaroa 30: 267-276 (2009).

Research paper thumbnail of New and validated high-rank syntaxa from Europe

Research paper thumbnail of Exkursionsflora für Kreta

ABSTRACT Full text not available.

Research paper thumbnail of The phytodiversity of the flora of Kriti (Greece) - a survey of the current state of knowledge

Research paper thumbnail of Flora and vegetation of Gávdos (Greece), the southernmost European island. I. Vascular flora and chorological relations

Research paper thumbnail of New and validated high-rank syntaxa from Europe

Mucina, L., Dengler, J., Bergmeier, E., Čarni, A., Dimopoulos, P., Jahn, R. & Matevski, V. New an... more Mucina, L., Dengler, J., Bergmeier, E., Čarni, A., Dimopoulos, P., Jahn, R. & Matevski, V. New and validated high-rank syntaxa from Europe. Lazaroa 30: 267-276 (2009).

Research paper thumbnail of An inventory of the vascular plants and bryophytes of Gavdopoula island (S Aegean, Greece) and its phytogeographical significance

Willdenowia, 2011

Bergmeier E., Blockeel T., Böhling N., Fournaraki C., Gotsiou P., Jahn R., Lansdown R. & Turland ... more Bergmeier E., Blockeel T., Böhling N., Fournaraki C., Gotsiou P., Jahn R., Lansdown R. & Turland N.: An inventory of the vascular plants and bryophytes of Gavdopoula island (S Aegean, Greece) and its phytogeographical significance. -Willdenowia 41: 179 -190. -Online ISSN 1868-6397; © 2011 BGBM Berlin-Dahlem. Gavdopoula is an island of 177.5 ha in the S Aegean, near the southeasternmost point of Europe. Based on field excursions in 1998/99 and 2009/10, we provide an annotated floristic catalogue of 186 vascular plant and 13 bryophyte taxa, with a full record of herbarium specimens and field observations, being the first botanical inventory of the island. Species richness in relation to island area is, as shown in a diagram, according to expectations. Among the vascular plants there are six regional ('Cretan area') endemics. The Saharo-Arabian-S Mediterranean phytogeographical element is well represented, with several species confined in Greece or even in Europe to the small islands south of Crete. Of these, Atriplex mollis occurs in Europe only on Gavdopoula. The moss Entosthodon commutatus has not previously been recorded from the E Mediterranean. The vegetation is controlled chiefly by the dry Mediterranean climate, calcareous shallow soils, sea spray and seasonal grazing. It consists of halo-nitrophytic and Pistacia lentiscus scrub, two types of phrygana, small-scale ephemeral pastures with winter-annuals on red-loamy soils, and sea-cliff vegetation. The new combination, Lysimachia arvensis var. caerulea, is published.

Research paper thumbnail of Flora and phytogeographical significance of the islands Chrisi, Koufonisi and nearby islets (S Aegean, Greece

Bergmeier, E., Kypriotakis, Z., Jahn, R., Böhling, N., Dimopoulos, P., Raus, Th. & Tzanoudakis, D... more Bergmeier, E., Kypriotakis, Z., Jahn, R., Böhling, N., Dimopoulos, P., Raus, Th. & Tzanoudakis, D.: Flora and phytogeographical significance of the islands Chrisi, Koufonisi and nearby islets (S Aegean, Greece). -Willdenowia 31: 329-356. 2001. -ISSN 0511-9618. An annotated floristic catalogue is provided for the islands Chrisi (Gaidouronisi), Koufonisi and the nearby islets Mikronisi, Strongili, Makrouli and Trachilos, all off SE Kriti. Critical use is made of literature data, and hitherto unpublished records, mostly from 1997 through 2000, add substantially to the first full vascular plant inventory of the islands. The total numbers of vascular plant taxa currently known from each island are as follows (accepted taxon records from literature, if extant, in brackets): Chrisi 275 (162), Mikronisi 71 (21), Koufonisi 273 (71), Strongili 110, Makrouli 115, Trachilos 96. Most noteworthy are Suaeda palaestina and Ononis vaginalis (currently with their single localities in Europe); Allium brachyspathum, Astragalus boeticus, A. peregrinus, Galium recurvum, Hippocrepis unisiliquosa, Lagurus ovatus subsp. nanus, Ononis diffusa, Orobanche grisebachii, Schoenoplectus litoralis (new records or confirmations for the Cretan area as a whole, or for the territory of Kriti proper including offshore islands); and Chlamydophora tridentata, Frankenia corymbosa and Hymenolobus procumbens (new regional records for the E part of Kriti and its offshore islands). The N African, pronouncedly thermophilous phytogeographical element is fairly well represented in the investigated area, thence Koufonisi in particular must be considered the driest and hottest SE European island. The principal habitats encountered in each of the islands are outlined and the present conditions for nature conservation discussed.

Research paper thumbnail of The Cerastium scaposum group (Caryophyllaceae): three annual taxa endemic to Crete (Greece), two of them new