invasive species as a treat to local biodiversity: integrated approach on buddleja davidii and...

| Content i

Students 3th Bachelor Green management PHL University College Supervision and coördination : Sarah Descamps and Alain De Vocht

September 23th 2012

INVASIVE SPECIES AS A THREAT TO LOCAL BIODIVERSITY:

INTEGRATED APPROACH ON BUDDLEJA DAVIDII AND CYPRINUS CARPIO IN AN

EDUCATIONAL TRIAL

Invasive species as a threat to local biodiversity p

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Content Content ......................................................................................................................................................................................................................... ii Summary ..................................................................................................................................................................................................................... iii 1 Introduction ....................................................................................................................................................................................................... 1 2 Project goals and objectives ....................................................................................................................................................................... 1 3 Material and methods ................................................................................................................................................................................... 2 3.1 Sampling plots and soil sampling in stands of Butterfly bush (B. davidii) ..................................................................... 2 3.2 Soil analysis ............................................................................................................................................................................................... 2 3.3 Fish monitoring ....................................................................................................................................................................................... 2

4 Results .................................................................................................................................................................................................................. 4 4.1 Soil conditions near stands of B. davidii ....................................................................................................................................... 4 4.2 Fish community ....................................................................................................................................................................................... 6

5 Discussion ........................................................................................................................................................................................................... 7 5.1 Soil conditions and Butterfly bush .................................................................................................................................................. 7 5.2 Control measures for Butterfly bush .............................................................................................................................................. 7 5.3 Fish community ....................................................................................................................................................................................... 8

6 Conclusions ........................................................................................................................................................................................................ 8 7 References ....................................................................................................................................................................................................... 11


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| Summary iii

Summary This project was carried out as a student project by students in the specialisation ’Nature and Forest management’ of the bachelor Green management of the PHL University College. The presence of invasive alien species (IAS) is a major problem in many quarries. IAS have an important negative impact on the local biodiversity and are a threat to native species not only in the quarry but if further dispersed also for the surroundings. This project will investigate the invasive species Buddleja davidii, a major problem in quarries such as Loën and source for contamination of adjacent habitats or ecosystems, as gravel banks of river Meuse. The species shows a very strong potential for dispersion and dominates new ecosystems very rapidly, strongly hampering settlement of native species in early successions. The project will investigate the distribution and habitat specificity in the quarry of Loën. Methods to eliminate and control the species will be studied and a selection of methods will be presented. The results are applicable in other quarries of HeidelbergCement.

The project has been set up as an educational project for 3th year bachelor students in Nature and Forest conservation. The aim of the educational project is to enhance the knowledge of vulnerability of novel ecosystems for invasive alien species and to increase their insight in the important potentials for habitat restoration for endangered species in quarries.

Secondly the biodiversity of fishes in the central pond in the quarry of Loën will be studied. The presence of native as well as invasive species will be investigated. Based on the inventory, adequate measures to enhance the aquatic fish or amphibian biodiversity and the control of invasive alien fish species can be formulated.

Students in the professional bachelor nature-‐ en forest conservation (PHL University College) are very sceptic and often negative regarding exploitation of quarries and their impact on the landscape and biodiversity. This project aims to widen their views and to open their minds regarding the potentials and threats in novel ecosystems and their knowledge in management of invasive alien species. In the project students will be introduced in the ecology of the quarry, they will set up a soil sampling scheme and mapping of B. davidii. Science based results will be used the support control strategies. Further more they will help monitoring the fishes in the shores of the aquatic pond. Especially the presence of carp (Cyprinus carpio) has a negative effect on the reproductive success of amphibians in these ecosystems.

This report summarizes of a more elaborated version in Dutch, with the results of the soil analysis in the quarry of Loën in respect to the distribution and cover of the Butterfly bush (B. davidii). After a concise introduction, elucidating the problem, the sampling set up and methods applied are listed in the section ‘Material and methods’. The results of the soil analysis (pH, NO2-‐, NO3-‐, O-‐PO43-‐, Fe, Ca, humidity) and cover of B. davidii is presented in the section ‘Results’. The results, invasive character of the species and management options are discussed and conclusions of the project are formulated.

In addition the results of the fish monitoring in the central pond are presented as well as possible actions to enhance the ecological quality of this aquatic ecosystem.

The students and supervisors wish to thank HeidelbergCement and CBR for the support and engagement in this educational project. The project gave us the opportunity to adjust our initial idea of excavation and its impacts on biodiversity. Both the opportunities for biodiversity in these novel ecosystems as well as the threats for biodiversity are certainly clarified to us now

| Introduction 1

1 Introduction Invasive alien species (IAS) are one of the major threats to biodiversity worldwide. The Conference of the Parties (COP) to the Convention on Biological Diversity (CBD) has recognized that there is an urgent need to minimize the spread and impact of IAS. Article 8(h) of the Convention states: Each Contracting Party shall, as far as possible and as appropriate, prevent the introduction of, control or eradicate those alien species which threaten ecosystems, habitats or species. Especially novel ecosystems and pioneer habitats are vulnerable to invasion of alien species. In nature development many initiatives to enhance local biodiversity are hampered by invasion of foreign species in newly created habitats or biotopes. Pumpkinseed or carps invade ponds constructed for amphibians and narrow-‐leaved ragwort or butterfly bush invade bare soils in restoration projects.

Regarding the potential for nature conservation and biodiversity in quarries, these aspects have to be taken into account. Management cannot only be focussed on rare or red list species; establishment of populations of invasive species will have to be integrated in quarry management plans and restoration efforts. HeidelbergCement as a company promotes biodiversity in their quarries and integrates this aspect in its company vision and mission (HeidelbergCement, 2010).

2 Project goals and objectives Three main goals of the project can be formulated and their measurability, relevance, attainability and time-‐dependence have been checked.

Students in the professional bachelor nature-‐ en forest conservation (PHL University College) are very sceptic and often negative regarding exploitation of quarries and their impact on the landscape and biodiversity. This project aims to widen their views and to open their minds regarding the potentials and threats in novel ecosystems and their knowledge in management of invasive alien species.

Apart of this central goal the project aims to clarify the invasive success of Buddleja davidii in the quarry of Loën in order to evaluated possible management actions.

Quarries such as in Loën are important for rare amphibians such as Natterjack toad (Bufo calamita), Midwife toad (Alytes obstreticans), both recorded in the quarry of Loën. Predation by fishes, and especially Carp or Pumpkinseed, is an important pressure on the conservation of these populations. Knowledge on the fish community present in the central pond is crucial in this respect. The project aims to make an inventory of the fishes present in shallow habitats of the pond that are important for amphibian reproduction.

The first goal is monitored by a survey before and after the project and these results are presented in the conclusions only.

The second goal is met if correct information on soil composition has been made available and discussed in respect to management strategies.

Results of the fish monitoring will clarify the potential impact of fishes on the amphibian reproduction and aquatic ecosystem.

The goals will have to be attained within a short time frame, leaving possibilities for further adjustment.


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| Material and Methods 2

3 Material and Methods

3.1 Sampling plots and soil sampling in stands of Butterfly bush (B. davidii) Students executed the soil or substrate sampling in order to investigate the soil or substrate characteristics in stands of B. davidii in five different plots of 2 by 2 meter with different cover of Butterfly bush (B. davidii) (Figure 1). Duplicate plots with the same cover of Butterfly bush were selected and sampled (Table 1).

Within each plot six soil subsamples were taken with the gouge bit or Edelmann earth auger (Figure 2). These samples were mixed in order to retrieve a representative soil sample of the plot.

Table 1. Codes of sampled plots and indication of the cover of Buddleja davidii and number of individuals.

3.2 Soil analysis Soil or substrate samples were weighted the day of sampling and dried in the oven (105 ° C) in order to determine moisture content (Figure 3). Soil moisture content was calculated as WH2O = (m1 – m2/m2 – m0)*100. The dried soil samples were grinded and sieved (2 mm) (Figure 4). Soil solutions were prepared with demineralized water and filtered sequentially with a paper filter MN 615 and microfiltration with PALL Acrodisc 32 mm (0.2 µm) on a syringe. The filtered solution was used for determination of pHH2O, conductivity and nutrients. A solution of 1 M KCl was used for determination of pHKCl.. For pH-‐measurements, the slurry was shacked for 60 min ± 10 min on a mechanical stirring machine. Measurement was performed in between 1 and 3 hours after filtration.

Measurements were performed by room temperature (± 20 °C) using 20 g dried soil and 100 ml solution (demineralized water or KCl). pH and conductivity were measured using Hanna HI 2550 (Figure 5). Total and carbonate hardness were measured colorimetrically (Merck). Ammonia (NH4+), nitrite (NO2-‐), nitrate (NO3-‐), orthophosphate (O-‐PO43-‐) and iron (Fe) were measured with a spectrophotometer Merck SQ NOVA 60 (Figure 6). Total NPK (nitrogen, phosphorus and Potassium) were measured additionally.

3.3 Fish monitoring The fish community in the central pond or lake was investigated the 27th of April 2012. Shallow banks and connected shallow marshes and bays, important breeding habitats for amphibians, were monitored by electrofishing (DEKA 7000) from a boat (Figure 7, Figure 8). All fishes (and amphibians) were identified, measured and large fish was weighed (Figure 9, Figure 10). The pond it self is very turbid and milky of colour. The poor visibility hampers the growth of submerse aquatic vegetation. In the shallow bays reed is present.

Cover Buddleja davidii Plot Observed plants of Buddleja davidii

0% 0A 0 plants

0B 0 plants

0 -‐ 25% 1A 2 small plants

1B 2 small plants

25 -‐ 50% 2A 6 small plants

2B 4 plants

50 -‐ 75% 3A 5 plants: 3 tall, 2 small

3B 6 plants

75 -‐ 100% 4A 5 plants, of which 1 very tall branched

4B 8 plants, of which 3 small


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| Material and Methods 3

Figure 1. Students on a field visit for soil sampling. Figure 2. Soil sampling site near Butterfly bush.

Figure 3. Drying of the soil samples. Figure 4. Grinding and sieving of the soil samples.

Figure 5. Measurement of pHKCl in a solution of the soil sample.

Figure 6. Measurement of nutrients using the spectrophotometer.

Figure 7. Start of the fishing. Figure 8. Electrofishing a shallow bay of the pond.


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| Results 4

Figure 9. Students measuring the fishes. Figure 10. Weighing individual Carp.

4 Results 4.1 Soil conditions near stands of B. davidii The results of the soil analysis are summarized in Table 2. Soil moisture content varies between 5 and 17 %. There is no significant difference in pHH2O of the soil solution between the different stands or covers (Figure 11). An average of 8.75 (± sd 0.22) is noted. pHH2O has Remarkably a higher pHKCl is measured if the cover of Butterfly bush is higher. The average pHKCl is 6.88 (± sd 0.46). The difference between pHH2O and pHKCl is relatively high, indicating potentials for less alkaline conditions over time. Dense stands of Butterfly bush hamper weathering of the disturbed soils or substrate. In denser stands of Butterfly bush, proton (H+) are bound stronger to the substrate in comparison to soils were no Butterfly bush is present. There is no clear correlation between the conductivity of the soil solution and the presence and cover of Butterfly bush. The average conductivity of the soil solution is low, 61 µS/cm (± sd 20) indicating a strong bond between ions and the substrate and a very low bioavailability of nutrients (Figure 12). Also the carbonates or Ca2+ and Mg2+-‐ions (total hardness) are well bound and have a relative low bioavailability. A slight increase in alkalinity can be noticed in respect to the cover of Butterfly bush (Figure 13). This confirms the findings of higher pHKCl in the stands. Whether Butterfly bush buffers the soil in the stands or it prefers better buffered soil conditions.

Table 2. Results of the soil analysis including moisture content, pH (H2O and KCl), conductivity, carbonate alkalinity, total hardness, ammonia (NH4+-‐N) , nitrite (NO2

—N), nitrate (NO3—-‐N), phosphate (O-‐PO4

3-‐-‐P ) and iron (Fe) concentrations in the soil in relation to the cover of Butterfly bush (B. davidii).

Cover Buddleja davidii

Sampling plot

moisture content

pHH2O pHKCl Cond. (µS/cm)

Carb. Alk. (d°)

Total hardness (d°)

NH4+-‐N

(mg/l) NO3

-‐-‐N (mg/kg)

NO2-‐-‐N

(mg/kg) O-‐PO4

3-‐-‐P

(mg/kgl Fe

(mg/kg)

0% 0A 5.63% 8.9 6.2 32.7 3 2.5 5.2 6.5 0.45 3.95 0.9

0B 11.2% 8.4 6 94.8 3 3.5 3.65 19 0.35 3.8 1.2

0 -‐ 25% 1A 16.81% 8.6 6.9 77.1 4 3 4.25 17.5 0,3 6.35 1.2

1B 11.68% 9.2 6.7 40.1 3 2.25 2.05 9.5 0.35 4.7 0.85

25 -‐ 50% 2A 13.36% 8.6 7.1 62 5 3.5 4.25 9.5 0.35 5.95 1.15

2B 8.12% 8.8 7.2 65.8 4 2.75 2.7 6 0,3 17.2 0.7

50 -‐ 75% 3A 18.3% 8.9 7.3 50.2 3 3 3.15 17 0.25 8.2 0.9

3B 14.16% 8.8 6.9 42.3 3 2.75 2.1 17.5 0.25 15.5 0.95

75 -‐ 100% 4A 17.24% 8.6 7.2 73.5 5 3.75 3.25 13.5 0.3 7.95 0.7

4B 10.26% 8.7 7.3 74.8 4 3.5 3.2 17.5 0.3 4.3 0.95


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| Results 5

Figure 11. pH in the different soil samples in relation to the cover of B. davidii.

Figure 12. Conductivity in the different soil samples in relation to the cover of B. davidii.

Figure 13. Alkalinity and total hardness in the different soil samples in relation to the cover of B. davidii.

Figure 14. Nitrogen (ammonia, nitrate and nitrite) in the different soil samples in relation to the cover of B. davidii.

Figure 15. Orthophosphate-‐phosphorus in the different soil samples in relation to the cover of B. davidii.

Figure 16. Iron in the different soil samples in relation to the cover of B. davidii.

Nitrogen is present in the soil solutions as ammonia (0.68 ± 0.2 mgN/l), nitrite (0.06 ± 0.012 mgN/l) and nitrate (2.67 ± 1.01 mgN/l). No significant difference in ammonia concentration was found. Nevertheless in soils with a denser cover of Butterfly bush lower ammonia concentrations are found (Linear regression R2 = 0.30) (Figure 14). This can, however, be caused by a higher pH in denser stands and the formation of gaseous NH3. Great differences in nitrate concentration between duplicates were encountered in the reference conditions (0A and 0B). A positive trend toward higher nitrate levels in soils under dense cover of Butterfly bush is found as in ammonia. Possibly a better nitrification due to bacterial activity underneath Butterfly bush is responsible for lower ammonia and higher nitrate levels. Also in nitrite concentration, a negative correlation in respect with cover of Butterfly bush is


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| Results 6

found. A part of two high values of phosphorus in the soil samples no clear difference in phosphate concentration is found (Figure 15). In iron concentrations as well, no clear differences can be observed (Figure 16).

4.2 Fish community In total 603 fishes were caught. Five fish species; Roach, Three-‐spined stickleback, Carp, Prussian carp and Gudgeon are present (Table 3). Roach was most abundant but Carp and Gudgeon are present in high numbers as well. Three species of amphibians were found as well (Table 3).

Table 3. Fishes and amphibians caught in the shallow zones of the central pond in the quarry of Loën.

Name Scientific name Number

Roach Rutilus rutilus 359 Three-‐spined stickelback Gasterosteus aculeatus 14 Carp Cyprinus carpio var. 113 Gudgeon Gobio gobio 116 Prussian carp Carassius gibelio 1 Total 603 Alpine newt Ichthyosaura alpestris 2 Edible frog Pelophylax kl. esculentus 3 Marsh frog Pelophylax ridibundus 2

Figure 17. Length frequency distribution of the gudgeon in the pond of the quarry in Loën..

Figure 18. Length frequency distribution of roach in the pond of the quarry in Loën.

Figure 19. Length frequency distribution of three-‐spined stickelback in the pond of the quarry in Loën.

Figure 20. Length frequency distribution of carp in the pond of the quarry in Loën.


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| Discussion 7

Maximum length of Gudgeon was 11.6 cm. Gudgeons were very pale, lacking the characteristic spots on the flanks. Growth is slow, with a length of 4 – 4.5 cm after the first year. Most individuals are 2 to 4 years old but clear year classes cannot be identified in the length frequency distribution (Figure 17). Roach varied in length between 3.5 and 19,5 cm, with a median length of 7 cm (Figure 18). Most individuals belong to the first year class, with remarkably uncoloured iris in the eye. Older, adult fishes were present in much lower number. Fourteen Three-‐spined stickelbacks were caught with a maximum length of 6.5 cm (Figure 19). No year classes can be seen in the length frequency distribution.

A part of these native fish species, Carp and Prussian carp are present. Most carp was found in the length class between 10 and 30 cm, so still young, subadult individuals (Figure 20). Older, adult Carp up to 50 cm in length and 2.440 g were caught. The catches indicate that the reproductive success of Carp is high in the pond. Growth (length-‐weight relation) shows a normal growth and sufficient food for the populations.

5 Discussion 5.1 Soil conditions and Butterfly bush Difference between soil variables are small and do not explain the presence or differences in cover of Butterfly bush in the quarry of Loën. Also exposition has little influence on the presence of Butterfly bush in the quarry. The success of the Butterfly bush in the quarry of Loën can possibly be explained by the strong root system of the species, breaking the chalk or marl layer. An early maturation of the bush and high seed production help the plants to spread rapidly in novel ecosystems. Our results confirm the fact that Butterfly bush can influence the soil nutrient cycle. This is reflected in much higher nitrogen concentrations in de leaves of the species in comparison to native shrubs (Feng et al. 2007).

The measured nitrogen levels in the chalk quarry of Loën are very low. Both Birch and Butterfly bush are early pioneers of these habitats. At low soil nitrogen, Butterfly has an ability to maintain a greater leaf area irrespective of form, whereas Birch cannot. This explains the more rapid growth of Butterfly bush. Maintenance of leaf area is proposed as means whereby some pioneer species are able to grow faster than other species on soils and spoils with low nitrogen level (Humphries & Guarino, 1987).

Butterfly bush is found in the surroundings as well on the gravel banks of the river Meuse and along railways. Both these growing conditions are harsh as well. The substrate is composed out of stones and pebbles, the soil solution being alkaline.

5.2 Control measures for Butterfly bush Management of Butterfly bush is already integrated in the management plan (Colart 2010). In th priority zones selected, the biodiversity will be enhanced and Butterfly bush will be managed. Further woodland creation with Beech, Oak, Maple, Hazelwood and Ash will compete with Butterfly bush and lower light intensity is negative for this exotic species. However, in the open biotopes in the quarry, Butterfly bush will still be present and will have to be controlled over time. The control measures presented in this document can be helpful in controlling the species in the quarry. Biological control by species grazing on Butterfly bush has not yet been introduced in Europe. Cleopus japonicas and Mecysolobus erro have been introduced experimentally in New Zealand but results are not yet available. Introducing other alien species as control agent are dangerous if the introduced species is not a single host plant specialist.

General aspect in the control of Butterfly bush are a elimination or control from the outer bound of the quarry towards the centre, comprising roadside and other transport routes into the quarry in the control area, mechanical control is favoured to chemical control, which can be adapted if necessary. Minimise further


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| Conclusions 8

disturbance as this favours the species (Ream, 2006). Defoliation of Butterfly bush resulted in a marked decrease in reproductive capacity, consistent with the priority allocation of resources to compensational leaf area growth (Thomas et al. 2008).

Possible actions in controlling Butterfly bush in the quarries of HeidelbergCement:

• Removing tall shrubs with excavation machines in the quarry;

• Cutting and rub in glyphosate on the stubs in late summer (transport into the root system, preventing new shoots to establish again after cutting) Control for germination of seedlings is needed;

• Young plants (less than 3 years old) can be cut out (including major part of root system), alternatively plants can be burned or steamed but in the quarry many places are inaccessible;

• Cut branches before flowering or seed formation, preventing further spread. Difficult on the steep slopes;

• Establishing chalk meadow vegetation (sowing). Plant cover reduces the invasiveness;

• Increasing shad in bushed or forested areas will reduce growth and success of Butterfly bush;

• Intensive grazing by ‘Mergelland’ sheep or goats, but Butterfly bush is not loved by grazing herds;

5.3 Fish community Only a limited number of fish species was found inshore of the central pond of the quarry. Limnophilic species are lacking because no submerse vegetation is present in the turbid water. The high turbidity might well be increased by the presence of a high number of bottom-‐ dwelling fish such as Carp. In order to enhance the biodiversity of the aquatic ecosystem some measures are presented.

• The north bank can be more shallow, enhancing the bank vegetation and hence foraging and spawning habitat for limnophilic fish species and amphibians.;

• Control of invasive plants such as Black locust (Robinia pseudoacacia), Japanese knotweed (Phallopia japonica), Butterfly bush (B. davidii) on the banks;

• Control tree growth on the island and reconstruct the shores;

• Remove the carp population in order to enhance the visibility and submerse vegetation growth;

• Introduction of pike to further diminish the fish population.

6 Conclusions Soil variables do explain the invasive success of Butterfly bush in different stands in the quarry of Loën. Some trends are found, but the sampling effort is to small do draw scientifically based conclusions. The microclimate and alkaline, hard substrate favours Butterfly bush to indigenous bushes. Further research on Butterfly bush in the quarry of Loën could focus on the root system of the plants. Penetration depth, impact of ground water or local water tables might be important in the survival and success of the bush.

An extensive seed production, short juvenile life span with early reproduction, fast vegetative growth, deep rooting system and high tolerance to extreme conditions make the Butterfly bush a successful invasive plant. Recent research did not reveal adaptation of frost hardness and tolerance to colder climate conditions, leaving the


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| Conclusions 9

genetic potentials identical in native and invasive populations (Ebeling et al. 2008). The authors indicate a potential for further extension out of its native range. Only extreme cold (-‐ 30 °C) or high temperatures limit the further expansion of Butterfly bush. Butterfly bush there by managed to become the new black cherry worldwide. Management actions are desperately needed but will have be performed in an integrated approach and coordinated on a national or higher level. Informing the public if Butterfly bush is managed is needed. The ornamental plant is found to be attractive by the public and it attracts many butterflies.

The central pond in the quarry of Loën is in need of an ecological rehabilitation. Steep banks and especially the high turbidity restrict submerse aquatic vegetation and a high ecological value. Invasive exotic plant species on the banks will have to be removed. The milky character of the water has a negative impact if settled on eggs of both native fishes and amphibians. Side waters of the central pond are important breeding habitats for Natterjack toad and will have to maintain their open character. The management action being proposed can be realized in a short time frame without excessive costs.

Finally, one of the goals of the project was to widen the view and perception of student regarding biodiversity in quarries. The results of the survey before and after the project are presented in Figure 23 and Figure 24. The left column shows the answers prior to the project in February 2012. The right hand column shows the survey results after completion of the project and graduation of the students (September 2012). Students think that the impact of quarries on the landscape is a severe assault on the landscape (question 1) but their opinion regarding the impact on the biodiversity is changed and less negative (question 2). They do not further support the idea that quarries have a negative impact on species richness in the area (question 3) and they all see the potential for fauna and flora in quarries (question 4). The students still have mixed opinions about the need or necessity of quarries in society (question 5) and a minority of the students think that quarries should be forbidden (question 6).

We can conclude clearly, because student are unanimous in their answers that this project changed their view and opions regarding quarries and opportunities for nature conservation (Figure 21). They are also very well aware of the potential threats imposed by invasive alien species in quarries after completion of the project (Figure 22).

Figure 21. Positive change in opinions regarding quarries and opportunities for nature conservation.

Figure 22. Positive change in opinions regarding quarries and potential threats for nature conservation..


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| Conclusions 10

Figure 23. Results from the survey held among the students prior to the project.

Figure 24. Results from the survey held among the students prior to the project..


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| References 11

7 References Colart D. 2010. S.A. Cimenteries CBR (Heidelberg Cement Group). La biodiversité dans nos carrières.

Ebeling, S.K., Welk, E., Auge, H. and Bruelheide, H. 2008. Predicting the spread of an invasive plant: combining experiments and ecological niche model. Ecography 31: 709-‐719.

Feng, Y.L., Auge, A. & Ebeling, S.K. 2007. Invasive Buddleja davidii allocates more nitrogen to its photosynthetic machinery than five native woody species. Oecologia 153: 501-‐510.

Humphries, R.N. & Guarino, L. 1987. Soil nitrogen and the growth of birch and buddleia in abandoned chalk quarries. Reclamation and Revegetation Research Vol. 6, no. 1, pp. 55-‐61.

2HeidelbergCement AG (ed.). 2010. Promotion of biodiversity at the mineral extraction sites of HeidelbergCement.

2nd Edition. Edited by: Dr. Rademacher M., Dr. Tränkie U., Dr. Hübner F., Offenwanger H. & Kaufmann S.

Thomas, M. M. Watt, M. S. Jay, J. Peltzer, D. Mason, E. G Turnbull, M. H. Whitehead, D. 2009. Influence of defoliation on reproductive capacity and growth in Buddleja davidii. Weed Research Vol. 49 Issue 1 pp. 67-‐72

Ream, J. 2006. Production and Invasion of Butterfly Bush (Buddleja davidii) in Oregon. Project State University of Oregon pp. 65.

invasive species as a treat to local biodiversity: integrated approach on buddleja davidii and...

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