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The reproductive potential and importance of key management aspects for successful Calluna vulgaris rejuvenation on abandoned Continental heaths

View Article: PubMed Central - PubMed

ABSTRACT

The abandonment of traditional pastoralism as well as the use of heath areas for military purposes has had a major impact on dry heaths in the Continental biogeographical region of Europe, causing severe degradation of its key species Calluna vulgaris (L.) HULL. The reproductive potential of this species in a Continental climate is assumed to be low, although there is yet no observational or experimental evidence for this. More knowledge is also needed about cost‐effective and sustainable measures to restore abandoned dry heaths in this biogeographical region, because traditional management options are often too expensive (e.g., sod‐cutting) or restricted due to environmental laws and the danger of unexploded ammunition (e.g., burning). Using as an example an 800 ha Continental heathland in Germany that has been abandoned for about two decades, we studied the reproductive potential (seed production, soil seed bank, and germination ability) of degenerate C. vulgaris stands. In addition, we conducted a comprehensive field experiment to test the effects of low‐intensity, year‐round grazing by Heck cattle and Konik horses as well as one‐time mowing and patchy exposure of bare soil on the generative rejuvenation (i.e., recruitment and survival) of degenerate C. vulgaris stands over 3 years. We used generalized linear mixed models for statistical analyses. Seed production of degenerate C. vulgaris stands was high as well as the germination ability of their seeds, being similar to Atlantic heathlands. However, soil seed‐bank densities were lower than those found in managed or abandoned Atlantic heaths. Overall seedling recruitment in the field was considerably lower in comparison with Atlantic heaths. Low‐intensity grazing or one‐time mowing did not induce a substantial increase in C. vulgaris recruitment, whereas an additional one‐time creation of bare soil patches or the one‐time creation of bare soil without subsequent management significantly facilitated seedling recruitment and survival in the first year. However, from the second year on, the positive effect of the creation of bare soil without subsequent management was no longer present. In the third year, survival of juveniles was significantly supported by low‐intensity grazing in combination with shallow soil disturbances as well as in combination with one‐time mowing and shallow soil disturbances, whereas mowing alone resulted in marginally significant lower survival. The extremely low seedling recruitment requires a careful choice of suitable management measures to promote the survival of sufficient numbers of Calluna individuals. Therefore, we recommend low‐intensity grazing with free‐ranging robust breeds and the combination of this with one‐time mowing as an effective means of supporting generative rejuvenation of C. vulgaris in degraded heaths. However, at the beginning of the restoration process, the creation of bare soil patches for seedling recruitment is crucial. For implementation into practice, we present different strategies to enhance the proportion of bare soil after long‐term abandonment of heaths when traditional management options are no longer feasible.

No MeSH data available.


Related in: MedlinePlus

Experimental design: A block consists of four 5 × 5 m plots containing the grazing (G) and mowing (M) treatments and the control (C). Soil disturbances (D treatment) were carried out on one half of each plot (i.e., on subplots of 2.5 × 5 m each, gray shading). Each plot was separated by ca. 15 m buffer strips
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ece32816-fig-0001: Experimental design: A block consists of four 5 × 5 m plots containing the grazing (G) and mowing (M) treatments and the control (C). Soil disturbances (D treatment) were carried out on one half of each plot (i.e., on subplots of 2.5 × 5 m each, gray shading). Each plot was separated by ca. 15 m buffer strips

Mentions: A block consisted of four 5 × 5 m plots with ca. 15‐m strips between plots. Calluna cover ranged from 70% to 90%. The plots were covered by approximately 70% litter in a 1‐ to 3‐cm‐thick layer over a thin humus layer. Dominating vascular plant species as well as the cryptogam coverage was mentioned above (see study site). Each block consisted of two grazed and two ungrazed plots (exclosures) as well as of two mown and two unmown plots. Grazing (G) and mowing (M) were the main treatments, with a soil disturbance treatment (D) included on half of each plot (i.e., subplots of 2.5 × 5 m each). All possible combinations of these single treatments, including the control (C), resulted in eight different treatments (Figure 1). G treatment plots were grazed as described above (basic management measure in the study area). The ungrazed plots were set up before the implementation of grazing in 2008. For the M treatment, we cut Calluna with a brushcutter at a height of 3–10 cm above the ground in November 2012. The clipped material was removed from the plots. A total of 25 small‐scale, shallow soil disturbances (10 × 10 × 3 cm) were randomly distributed over each D treatment subplot. These soil disturbances were supposed to mimic either higher grazing pressure (by imitating the trampling effects of grazers) or deep‐set mowing which exposes bare soil and were manually created by removing the litter and humus layer in November 2012.


The reproductive potential and importance of key management aspects for successful Calluna vulgaris rejuvenation on abandoned Continental heaths
Experimental design: A block consists of four 5 × 5 m plots containing the grazing (G) and mowing (M) treatments and the control (C). Soil disturbances (D treatment) were carried out on one half of each plot (i.e., on subplots of 2.5 × 5 m each, gray shading). Each plot was separated by ca. 15 m buffer strips
© Copyright Policy - creativeCommonsBy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5383499&req=5

ece32816-fig-0001: Experimental design: A block consists of four 5 × 5 m plots containing the grazing (G) and mowing (M) treatments and the control (C). Soil disturbances (D treatment) were carried out on one half of each plot (i.e., on subplots of 2.5 × 5 m each, gray shading). Each plot was separated by ca. 15 m buffer strips
Mentions: A block consisted of four 5 × 5 m plots with ca. 15‐m strips between plots. Calluna cover ranged from 70% to 90%. The plots were covered by approximately 70% litter in a 1‐ to 3‐cm‐thick layer over a thin humus layer. Dominating vascular plant species as well as the cryptogam coverage was mentioned above (see study site). Each block consisted of two grazed and two ungrazed plots (exclosures) as well as of two mown and two unmown plots. Grazing (G) and mowing (M) were the main treatments, with a soil disturbance treatment (D) included on half of each plot (i.e., subplots of 2.5 × 5 m each). All possible combinations of these single treatments, including the control (C), resulted in eight different treatments (Figure 1). G treatment plots were grazed as described above (basic management measure in the study area). The ungrazed plots were set up before the implementation of grazing in 2008. For the M treatment, we cut Calluna with a brushcutter at a height of 3–10 cm above the ground in November 2012. The clipped material was removed from the plots. A total of 25 small‐scale, shallow soil disturbances (10 × 10 × 3 cm) were randomly distributed over each D treatment subplot. These soil disturbances were supposed to mimic either higher grazing pressure (by imitating the trampling effects of grazers) or deep‐set mowing which exposes bare soil and were manually created by removing the litter and humus layer in November 2012.

View Article: PubMed Central - PubMed

ABSTRACT

The abandonment of traditional pastoralism as well as the use of heath areas for military purposes has had a major impact on dry heaths in the Continental biogeographical region of Europe, causing severe degradation of its key species Calluna vulgaris (L.) HULL. The reproductive potential of this species in a Continental climate is assumed to be low, although there is yet no observational or experimental evidence for this. More knowledge is also needed about cost‐effective and sustainable measures to restore abandoned dry heaths in this biogeographical region, because traditional management options are often too expensive (e.g., sod‐cutting) or restricted due to environmental laws and the danger of unexploded ammunition (e.g., burning). Using as an example an 800 ha Continental heathland in Germany that has been abandoned for about two decades, we studied the reproductive potential (seed production, soil seed bank, and germination ability) of degenerate C. vulgaris stands. In addition, we conducted a comprehensive field experiment to test the effects of low‐intensity, year‐round grazing by Heck cattle and Konik horses as well as one‐time mowing and patchy exposure of bare soil on the generative rejuvenation (i.e., recruitment and survival) of degenerate C. vulgaris stands over 3 years. We used generalized linear mixed models for statistical analyses. Seed production of degenerate C. vulgaris stands was high as well as the germination ability of their seeds, being similar to Atlantic heathlands. However, soil seed‐bank densities were lower than those found in managed or abandoned Atlantic heaths. Overall seedling recruitment in the field was considerably lower in comparison with Atlantic heaths. Low‐intensity grazing or one‐time mowing did not induce a substantial increase in C. vulgaris recruitment, whereas an additional one‐time creation of bare soil patches or the one‐time creation of bare soil without subsequent management significantly facilitated seedling recruitment and survival in the first year. However, from the second year on, the positive effect of the creation of bare soil without subsequent management was no longer present. In the third year, survival of juveniles was significantly supported by low‐intensity grazing in combination with shallow soil disturbances as well as in combination with one‐time mowing and shallow soil disturbances, whereas mowing alone resulted in marginally significant lower survival. The extremely low seedling recruitment requires a careful choice of suitable management measures to promote the survival of sufficient numbers of Calluna individuals. Therefore, we recommend low‐intensity grazing with free‐ranging robust breeds and the combination of this with one‐time mowing as an effective means of supporting generative rejuvenation of C. vulgaris in degraded heaths. However, at the beginning of the restoration process, the creation of bare soil patches for seedling recruitment is crucial. For implementation into practice, we present different strategies to enhance the proportion of bare soil after long‐term abandonment of heaths when traditional management options are no longer feasible.

No MeSH data available.


Related in: MedlinePlus