BRYOPHYTE OCCURRENCE PATTERNS ON DEAD WOOD IN MONTANE FORESTS

Transcription

1 BRYOPHYTE OCCURRENCE PATTERNS ON DEAD WOOD IN MONTANE FORESTS Irina Goia & Dan Gafta Babeş-Bolyai University Cluj-Napoca (Romania) Department of Taxonomy and Ecology

2 Introduction The significance of dead wood for bryophytes covers the following main issues in the current literature: Dependence of species richness upon wood decay stage, thickness and water retention capacity, distance from water bodies (Söderström 1988a, Laaka 1993, Vellak & Paal 1999, Christensen & Emborg 1996, Kirby et al ). Ecological determinism of bryophyte assembly in epixyle communities (McCulloch 1948, Muhle & LeBlanc 1975, Cornelissen & Karssemeijer 1987, Crites & Dale 1998, Söderström 1988b, Jansová & Soldán 2006). Dead wood bryophytes as indicators of old-growth, unmanaged forests (Ódor & Standovar 2001, Goia & Schumacker 2003). Dead wood as a habitat for threatened bryophytes (Gustafsson & Hallingbäck 1988, Söderström 1988b, Samuelsson et al. 1994, Ódor & Standovár 2001, Goia & Schumacker 2003).

3 Objective and goals Searching for patterns in species occurrence and floristic composition of epixyle bryophyte communities in relation to dead wood species, ph, slope, aspect and elevation. We set out to answer the following questions: (1) Are bryophyte assemblages different in terms of species composition between beech and spruce dead wood? (2) How porophyte-specific are epixyle bryophyte species? (3) Which are the most important abiotic factors that are related to the frequency of epixyle bryophyte species? (4) Which are the common species that mostly co-occur with the threatened ones?

4 Romanian Western Carpathians Area: 580 Km2 Altitudinal limits: - Cucurbăta Mare (Biharia Peak) 1849 m a.s.l.; - Confluence between Arieşul Mic and Arieşul Mare rivers 565 m a.s.l.; - Elevation range: 1284 m a.s.l.; Mean annual precipitation: mm Mean annual temperature: 7.46oC

5 Dominant vegetation types: beech, spruce and mixed forests

6 Alder and willow-groves hardly subsist to village development and agricultural activities along streams

7 Materials and Methods 130 relevés have been performed on dead wood of beech (37 relevés) and spruce (93 relevés) Area sampled was determined by the extent of bryophyte communities, and varied between 30 cm2 and 4 m2 Environmental variables related to dead wood substrate: ph, elevation, slope and aspect All statistical analyses were performed on presence/absence of recorded species: ANOSIM to assess the significance of floristic dissimilarity between bryophyte assemblages on beech and spruce dead wood CCA to visualise the eco-floristic overlap between the two porophytetype groups ANCOVA to test the separation of the two groups along the CCA axis 1 by accounting for ph and elevation Multiple logistic regression to test the effect of porophyte species on the occurrence of each bryophyte species by controlling for the effect of environmental variables One-tailed exact Fisher's test to estimate the association between threatened species and common species

8 Results 8 Box-plot of ranked floristic dissimilarity between and within bryophyte assemblages developed on beech and spruce dead wood.

9 CCA ordination of epixyle bryophyte assemblages with environmental variables drawn as vectors and 95% concentration ellipses.

10 Adjusted means along with their 95% confidence interval of CCA axis 1 scores of bryophyte assemblages assigned to either beech or spruce dead wood by controlling for the effect of ph and elevation.

11 Predicted probabilities of occurrence of Brachythecium salebrosum, B. velutinum, Sanionia uncinata and Herzogiella seligeri by dead wood species

12 Probability curves of occurrence of Cephalozia bicuspidata, Bryum subelegans, Pseudoleskeela nervosa, Pterigynandrum filiforme by dead wood species as a function of ph (B = beech; S = spruce)

13 Probability curves of occurrence of Plagiothecium laetum, Pterigynandrum filiforme and Hypnum cupressiforme by dead wood species as a function of elevation. B = beech S = spruce

14 Probability curves of occurrence of Lophozia ascendens as a function of ph and elevation

15 Common species (in black) displaying significant association with threatened taxa (in red) [only species with frequency larger than 5% were considered] Tritomaria exsecta Cephalozia bicuspidata Blepharostoma trichophyllum Rhizomnium punctatum Buxbaumia viridis Calypogeia suecica Scapania apiculata Lophozia ascendens Lophozia ventricosa Riccardia latifrons p= p= Lophocolea heterophylla Herzogiella seligeri Lophozia incisa

16 Conclusions There is a significant but slight floristic distinctiveness between epixyle bryophyte assemblages established on spruce and beech dead wood, even when accounting for the effects of ph and elevation. Few common species display a preference for either spruce or beech dead wood, but in some species these relationships are confounded by the effects of ph and/or elevation. We detected several common species that are potential indicators of threatened species occurrence. None of threatened species recorded shows a preference for a dead wood species. To a small extent our results may be biased by the difference in sample size between spruce and beech dead wood. That was determined by the much higher availability of spruce dead wood in the area investigated. The practice of forest management should take into account the importance of leaving in place the uprooted, damaged and dead standing trees, especially in deciduous forests.

17 BRYOPHYTE OCCURRENCE PATTERNS ON DEAD WOOD IN MONTANE FORESTS Irina Goia & Dan Gafta Babeş-Bolyai University Cluj-Napoca (Romania) 1 Department of Taxonomy and Ecology

18 Introduction The significance of dead wood for bryophytes covers the following main issues in the current literature: Dependence of species richness upon wood decay stage, thickness and water retention capacity, distance from water bodies (Söderström 1988a, Laaka 1993, Vellak & Paal 1999, Christensen & Emborg 1996, Kirby et al ). Ecological determinism of bryophyte assembly in epixyle communities (McCulloch 1948, Muhle & LeBlanc 1975, Cornelissen & Karssemeijer 1987, Crites & Dale 1998, Söderström 1988b, Jansová & Soldán 2006). Dead wood bryophytes as indicators of old-growth, unmanaged forests (Ódor & Standovar 2001, Goia & Schumacker 2003). Dead wood as a habitat for threatened bryophytes (Gustafsson & Hallingbäck 1988, Söderström 1988b, Samuelsson et al. 1994, Ódor 2 & Standovár 2001, Goia & Schumacker 2003).

19 Objective and goals Searching for patterns in species occurrence and floristic composition of epixyle bryophyte communities in relation to dead wood species, ph, slope, aspect and elevation. We set out to answer the following questions: (1) Are bryophyte assemblages different in terms of species composition between beech and spruce dead wood? (2) How porophyte-specific are epixyle bryophyte species? (3) Which are the most important abiotic factors that are related to the frequency of epixyle bryophyte species? (4) Which are the common species that mostly co-occur with the threatened ones? 3

20 Romanian Western Carpathians Area: 580 Km2 Altitudinal limits: - Cucurbăta Mare (Biharia Peak) 1849 m a.s.l.; - Confluence between Arieşul Mic and Arieşul Mare rivers 565 m a.s.l.; - Elevation range: 1284 m a.s.l.; Mean annual precipitation: mm Mean annual temperature: 47.46oC

21 Dominant vegetation types: beech, spruce and mixed forests 5

22 Alder and willow-groves hardly subsist to village development and agricultural activities along streams 6

23 Materials and Methods 130 relevés have been performed on dead wood of beech (37 relevés) and spruce (93 relevés) Area sampled was determined by the extent of bryophyte communities, and varied between 30 cm2 and 4 m2 Environmental variables related to dead wood substrate: ph, elevation, slope and aspect All statistical analyses were performed on presence/absence of recorded species: ANOSIM to assess the significance of floristic dissimilarity between bryophyte assemblages on beech and spruce dead wood CCA to visualise the eco-floristic overlap between the two porophytetype groups ANCOVA to test the separation of the two groups along the CCA axis 1 by accounting for ph and elevation Multiple logistic regression to test the effect of porophyte species on the occurrence of each bryophyte species by controlling for the effect of environmental variables One-tailed exact Fisher's test to estimate the association between 7 threatened species and common species

24 Results 8 Box-plot of ranked floristic dissimilarity between and within bryophyte 8 assemblages developed on beech and spruce dead wood.

25 CCA ordination of epixyle bryophyte assemblages with environmental variables drawn as vectors and 95% concentration ellipses. 9

26 Adjusted means along with their 95% confidence interval of CCA axis 1 scores of bryophyte assemblages assigned to either beech or spruce dead wood by controlling for the effect of ph and elevation. 10

27 Predicted probabilities of occurrence of Brachythecium salebrosum, B. velutinum, Sanionia uncinata and Herzogiella seligeri by dead wood species 11

28 Probability curves of occurrence of Cephalozia bicuspidata, Bryum subelegans, Pseudoleskeela nervosa, Pterigynandrum filiforme by dead wood species as a function of ph (B = beech; S = spruce) 12

29 Probability curves of occurrence of Plagiothecium laetum, Pterigynandrum filiforme and Hypnum cupressiforme by dead wood species as a function of elevation. B = beech S = spruce 13

30 Probability curves of occurrence of Lophozia ascendens as a function of ph and elevation 14

31 Common species (in black) displaying significant association with threatened taxa (in red) [only species with frequency larger than 5% were considered] Tritomaria exsecta Cephalozia bicuspidata Blepharostoma trichophyllum Rhizomnium punctatum Buxbaumia viridis Calypogeia suecica Scapania apiculata Lophocolea heterophylla Lophozia ascendens Herzogiella seligeri Lophozia ventricosa Riccardia latifrons Lophozia incisa p= p=

32 Conclusions There is a significant but slight floristic distinctiveness between epixyle bryophyte assemblages established on spruce and beech dead wood, even when accounting for the effects of ph and elevation. Few common species display a preference for either spruce or beech dead wood, but in some species these relationships are confounded by the effects of ph and/or elevation. We detected several common species that are potential indicators of threatened species occurrence. None of threatened species recorded shows a preference for a dead wood species. To a small extent our results may be biased by the difference in sample size between spruce and beech dead wood. That was determined by the much higher availability of spruce dead wood in the area investigated. The practice of forest management should take into account the importance of leaving in place the uprooted, damaged and dead standing trees, especially in deciduous forests. 16