BSc Thesis
Floor Borstlap
July 2018, Amsterdam
The impact of aeolian activity on the occurrence of
Liparis Loeselii on the “Hors”, South-West Texel
Source: Texel (https://www.plusonline.nl/lekker-weg-in-eigen-land/texel-wad-een-eiland)
Supervisor: mw. dr. A.M. Kooijman
1
Abstract
The coastal dune areas represent one of the last nutrient-poor, base-rich landscapes in the Netherlands. These are good conditions for a high biodiversity (Grootjans et al., 2002). Dune areas are therefore important habitats for the species featuring on the Dutch Red List of endangered plant species, which are mainly pioneer species such as liparis loeselii (Grootjans et al., 2002). In order to protect these species from total extinction the focus should be on the creation of new habitat sites that can be colonised rather than on the maintenance of present populations (Oostermeijer & Hartman, 2014). Our research is important in order to better understand the population turnover rates in a metapopulation. And to possibly better understand the effect of more extreme weather on the habitat conditions, for endangered plant species. Therefore the aim of this research is to identify the role of aeolian activity in setting back succession in dune slacks. The methods that were used in order to answer the research question consists of a literature review, collecting soil samples and data in the field on Texel and in the laboratory and finally data analysis was used in order to draw
conclusions of the collected data. According to the pH range, vegetation cover and soil organic matter content, transect 3 in T6 and transect 1 in T8 are the most ‘stable’ transects. Transect 2 and 3 in T6 and transects 3,4 and 5 in T8 are considered to be the more ‘dynamic’ transects. Dynamic transects are influenced by sand deposits through aeolian activity and sometimes water. In the southern part of transect 4 of dune slack T8 high pH values are measured and the vegetation cover is low. Patches of bare sand are found there. We assume the pH value to decrease in the coming years. Therefore we expect the southern part of transect 4 of dune slack T8 to be the most favourable location for the growth of Liparis Loeselii in the near future.
2
Content
Introduction ... 3 Research area ... 3 Liparis Loeselii ... 4 Succession ... 5 Relevance ... 6 Methods ... 6 Results ... 10 Results T6 ... 10 pH ... 10 Vegetation cover ... 11Soil organic matter (SOM) ... 11
Boxplots ... 12
Combined results ... 12
Results T8 ... 13
pH ... 13
Vegetation cover ... 13
Soil organic matter (SOM) ... 14
Boxplots ... 14
Combined results ... 15
Discussion ... 15
Lack of data ... 15
Reliability of collecting soil samples ... 16
Making conclusions on possibly false premises ... 17
Upscaling to larger scales ... 17
Conclusion ... 18
References ... 20
3
Introduction
Wetlands are among the world’s most important ecosystems. The Netherlands consists of a large amount of these environmental resources. However the wetland ecosystems are under high pressure nowadays, mainly due to human activities (Best et al., 1993). The first major changes of the Dutch wetland ecosystems had to do with the afforestation with pine plantations, prohibition of pasturing and levelling of the coastal dunes in order to protect the inner dune belt from sand drift (van Dijk & Grootjans, 1993 ; Grootjans et al., 2002). During the 19th century local extensive agriculture and
management for drinkwater supply were the main disturbances in the dune areas (van Dijk &
Grootjans, 1993 ; Grootjans et al., 2002). While the agricultural activities were only for a short period of time, the drinkwater production from the fresh dune water is at present still one of the main functions of the dune area. Other present ecosystem services of the dunes are sea defence, outdoor recreation and nature conservation.
Research area
This research will focus on two dune slacks situated on the southern tip of the isle of Texel. Dune slacks are the low-lying areas within the coastal dunes. The research area Texel is unique as it is one of the last places in Europe where large amounts of sand are available for the formation of primary dunes (Westhoff and Van Oosten, 1991). This largeamount of sand can be traced back to morphological elements which are typical for barrier islands. One of these elements is a tidal inlet. This is a main channel that, in this case, connects the North sea with the Wadden sea and is known as the main ebb-channel because of the sediment transport that is dominated by ebb (Sha, 1990). The
Texel inlet, called “Marsdiep”, is the main channel between the North sea and the Wadden sea. It is located between Den Helder and the southern point of Texel and is formed between 800 and 1303 AD, probably during the heavy storms of the 12th century. After the formation of this tidal inlet the
coast of Texel has been growing due to accreting shoals in the ebb-tidal delta. This process resulted in the large amount of sand available in Texel (Kooijman et al., 2016). The shoal the “Hors” became attached to the island in 1749. The “Onrust” became part of Texel between 1908-1916. The present shoal of the ebb-tidal delta is an aggregation of two shoals: the "Noorderhaaks" and the "Razende Bol". The Razende Bol was above the low water line since 1925. Between 1956-1960 the two shoals became attached to each other and formed the “Razende Bol-Noorderhaaks” (fig. 1) (Kooijman et al., 2016). In this research we are only interested in the dune slacks T6 and T8 because these dune slacks are the areas that were recently colonized by Liparis Loeselii and are likely to be affected by aeolian activities (fig. 2).
4
Liparis Loeselii
The coastal dune areas represent one of the last nutrient-poor, base-rich landscapes in the Netherlands. These areas have the right conditions for a high biodiversity (Grootjans et al., 2002). Most of the species featuring on the Dutch Red List of endangered plant species, mainly pioneer species, are restricted to dune areas because the inland populations have become extinct (Grootjans et al., 2002).
In this study we focus on the plant species Liparis Loeselii. This is a perennial orchid that occurs in coastal dune slacks and inland fens. It is a small species and has white to pale green flowers and two yellow-green leaves (fig. 3) (Odé & Bolier, 2003). Within Liparis Loeselii two types are distinguished: a narrow- leaved type occurring in fens and a shorter, broader-leaved type occurring in dune slacks (Oostermeijer & Hartman, 2014). The species has a world-wide distribution. It occurs in parts of Europe, North America, Canada and Russia (Kooijman et al., 2016). Unfortunately the species is declining. Causes for decline of Liparis Loeselii can be traced back to habitat loss due to land
reclamation, drainage of wetlands and unfavourable management of nature reserves. Other reasons for the decline are (atmospheric) eutrophication and acidification, shrub encroachment and restriction of natural ecosystem dynamics. Therefore, in Europe the species is listed as endangered in the Habitat Directive and the Bern
Convention. In the other countries Liparis Loeselii has the highest conservation priority (Oostermeijer & Hartman, 2014).
A suitable habitat for Liparis Loeselii consists of nutrient poor, base-rich or calcareous soil with a high pH. The short life span of Liparis Loeselii brings forth a highly dynamic metapopulation, where the
formation of new sites with young successional vegetation is paramount for survival. According to Kooijman et al. (2016) there is a relation between the occurrence of Liparis Loeselii and the pH of the soil. Liparis Loeselii occurs only within a pH range of approximately 5.5-7.5, with peak values at a pH Figure 2 Map of dune slacks of SW-Texel (Kooijman et al, 2016)
Figure 3 Liparis Loeselii
Source: https://www.infoflora.ch/de/flora/liparis-loeselii.html
5 of 6.5. Furthermore, Liparis Loeselii was only found by a content below 4.3%. In soils with a C-content higher than 4.3% Liparis Loeselii is absent, this is illustrated by the fact that the species generally occurs in dune slacks with low soil organic matter content (Kooijman et al., 2016). However the species can still occur in rich fens which largely consist of soil organic matter and in dune slacks with a very high C-content, but only in combination with a high pH due to large groundwater seepage. This suggests that the soil organic matter content is a less important condition than the pH of the soil (Kooijman et al., 2016).
Succession
The Liparis Loeselii appears within approximately six years after formation of a new dune slack. After 11-16 years peak values are reached (Oostermeijer & Hartman, 2014 ; Kooijman et al., 2016). Due to accumulation of soil organic matter and a decrease of pH from 7.6 to 5.8 the species will eventually decline (fig. 4). It takes approximately 32-36 years for a dune slack to reach unsuitable pH conditions for Liparis Loeselii (Kooijman et al., 2016).
As reported by Kooijman et al. (2016) soil pH values significantly decrease with dune slack age. In the youngest dune slack (t11) the mean pH was approximately 8.4, whereas in the oldest dune slack (t1) values had decreased to 5.4 and 4.8. Correlations between pH and dune slack age are thus highly significant. Bulk density also significantly decreased during succession, due to accumulation of soil organic matter, which is much lighter than sand (Kooijman et al., 2016).
It is difficult to maintain habitat quality of the current populations on the longer term (Oostermeijer & Hartman, 2014). But short-term habitat management should not be neglected, as the remaining populations are essential seed sources for the colonisation of new sites. Some management options could extend population life span in European dune slacks. Annual mowing can keep vegetation structure open, and slows down acidification and accumulation of organic matter. Sod cutting is recommended in areas in which natural formation of new young successional sites does not occur. This sets back succession and increases the pH in situations in which accumulation of organic matter has acidified dune slacks (Oostermeijer & Hartman, 2014; Kooijman et al., 2016).
Figure 4 Succession (Oostermeijer & Hartman, 2014)
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Relevance
Previous research has shown that local extinction is an inevitable and natural process for some species, such as Liparis Loeselii (Oostermeijer & Hartman, 2014). In order to protect these species from total extinction the focus should be on the creation of new habitat sites that can be colonised rather than on the maintenance of present populations (Oostermeijer & Hartman, 2014). Our research is important in order to better understand the population turnover rates in a
metapopulation. And to possibly better understand the effect of more extreme weather on the habitat conditions, for endangered plant species. This can be very useful knowledge in order to obtain possible management practices in dune slacks facing climate change in the future. Since Liparis Loeselii is one of the first species to appear when the habitat has become suitable, and one of the first to disappear when succession proceeds, it is an excellent indicator species for its
endangered habitats.
The aim of this research is to identify the role of aeolian activity in setting back succession in dune slacks. Therefore the research question is:
‘What is the influence of aeolian activity on succession in the dune slacks T6 and T8, considering the
occurrence of Liparis Loeselii?’
First, the methods that were used are presented, after that the results are provided, this is followed by a discussion and conclusion. At the end also reference and appendixes are included.
Methods
An overview of the steps that have to be taken in order to write this research is provided in a table (tab. 1). First a literature review was done, next soil samples and other related data were collected on Texel and in the laboratory. The final data analysis was then done on all collected data. The written report of the entire process was done during the entire research period.
Table 1 Indication of the work flow
literature study
-research proposal - introduction - theoretical framework - methodology - expected resultsdata gathering
- fieldwork - transect sampling - transect soil profiledescription - grid point sampling
- grid point profile description - labaratory work
- bulk density - pH and EC values - organic matter content
data analysis
- GIS analysis-transect analysis - grid point analysis - aeral photographs - statistical analysis - conclusions - discussions
7 First it is important to obtain knowledge which is done through a literature study. This is a very important part as it is the basis of your research. With earlier research you can obtain important knowledge of the research area and other important elements which will be described in the theoretical framework. In this research we provided background information about the endangered plant species: Liparis Loeselii and presented the main concept of the research: succession.
Additionally literature can be used for combined research, the results of our research can be compared to earlier research to acquire new insights.
Figure 5 Research area
The second part of the research is the fieldwork period, in this period data is collected in the research area (fig. 5). During the fieldwork 70 sampling point are taken in the two selected dune slacks, T6 and T8. Dune slack T6 contains four transacts (fig. 6) and dune slack T8 contains three transects (fig. 7). Each transect consists of 10 sampling points, which means that the two dune slacks are divided into 7 transects. The transects were in some cases divided in two transects of each 5 sampling points. This was done in order to fit the sampling points in the dune slack area at places where the width of the dune slack was too small for a transect of 10 sampling points.
8 Fig 6. Location of transect point in dune slack T6
Fig 7. Location of transect points in dune slack T8
Before we went in the field we created a field form for all the transect sampling points where surface characteristics are documented such as the vegetation cover and bare sand cover. Furthermore the soil profile is described in detail, where we were mainly looking for thin layers of sand on top of the soil. Also a soil sample is collected in each sample point with metal pF-rings for the analysis of bulk density, pH and soil organic matter content that was measured later in the laboratory.
9 Besides the transects a grid is conducted in the two dune slacks. In dune slack T6 92 grid point
measurements were taken of which 30 measurements were taken in T1, 38 measurements in T6-T2 and 22 measurements in T6-T3. In dune slack T8 180 grid point measurements were taken of which 22 measurements were taken in T8-T1 and the other 158 measurement were taken in one big grid that was conducted in T8-T2/T3/T4. The location of each grid point is recorded with a GPS, and characteristic surface and topsoil features are described. For the grid point also a field form is made in order to save important information.
After the week of fieldwork, some laboratory work is done. For each soil sample the bulk density, pH and EC, and soil organic matter contents are measured. Two weeks were spend in the laboratory in order to obtain data out of our measurements. The methods and equations that were used for the measurements are demonstrated in a table (tab. 2). In the next part of this research the soil samples that were measured in the laboratory will be compared with soil samples that were collected in 2010, 2014/2015 in the dune slacks T6 and T8.
In the last part of the research GIS analysis was used in order to make maps of the collected data. The GIS-analysis consists of spatial analysis of the grid point data and the transect sampling point data. For the analysis of the data, interpolation techniques were applied. In this research the inverse distance weighted (IDW) interpolation technique was used. Apart from the field data, extrapolation wasapplied through comparison between field and laboratory data. Maps were made from data obtained in the field and data that were measured in the laboratory. This made is possible to make a map of the whole area. The aerial photos that were used in the GIS studio were obtained from PDOK (‘Publieke Dienstverlening Op de Kaart’). This is a website with aerial photos of the Netherlands were no license is needed to have access to the photographs.
Furthermore statistical analysis was done. Linear regression was used to determine relations
between two soil characteristics. It was determined that a relation was valid when the R-squared was 0.4 or higher. In Excel relations were plotted. Additionally statistical analysis in Matlab wasdone. By cause of small datasets in the previous years boxplots were made in order to give an overview of the measurements of the previous years in comparison to the measurements of 2018.
Soil measurement Laboratory method
Bulk Density of soil
20 grams of the soil sample will be put in the oven for 48 hours at 105°c. After the soil is dried in the oven the sample will be weighted again. Knowing the volume and weight of the original sample, the bulk density can be calculated as:
Dry sample weight
Bulk density = ________________________________________ Volume original sample
10 Table 2 Laboratory methods
Results
In this chapter the results are presented. The results consists of several maps and graphs. We will focus on a few soil characteristics that were measured in the field: the pH, soil organic matter content, bulk density and vegetation cover. First these characteristics will be considered separately after that the relations between the soil characteristics will be discussed.
Results T6
pH
A clear difference of the pH range can be seen between the transects. In T1 the pH ranges from 6.6-6.9, with a pH of around 6.8 which is most prevalent. In T2 the pH ranges from 6.4-6.9, with mostly a pH of around 6.6, which is slightly lower than the average pH of T1. In T3 the pH ranges from 5.9-6.6. The lowest pH values can thus be found in T3.
pH and EC value of soil 25 ml of demineralized water will be mixed with 10 grams of the soil
sample. It will be shaken for 2 hours, followed by a resting period overnight and another 20 minutes in the shaker the next day. The values will be measured using a pH and EC electrode.
Soil Organic Matter content (SOM)
The soil sample will be weighted and be placed in the oven for 16 hours at 375°c. The soil sample will be weighted again after this process and the SOM can be calculated as:
SOM = Wet sample weight – Dry sample weight
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Vegetation cover
All three transects have a most prevalent vegetation cover of 100%. In T2 also a number of bare patches are visible, with a vegetation cover that ranges from 0 to 50%. In a part of the T1 transect there was an 80% vegetation cover. The highest vegetation cover can be found in T3, which is almost fully vegetated.
Soil organic matter (SOM)
The lowest SOM content can be found in T1 (0.0-0.1). In T2 higher values of SOM (0.05-0.2) are visible. In T3 the highest SOM content can be found (0.15-0.3).
Figure 9 Vegetation cover in dune slack T6
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Boxplots
From 2015 to 2018 the bulk density in T1 has dropped from a median of approximately 1.43 to a median of 1.3. In the pH the same trend can be seen. The pH had a median of 7.6 in 2015. In 2018 the pH decreased to a value of around 6.8.
Figure 11 Bulk density in dune slack T6-T1
Combined results
Figure 12 Correlation pH and Soil organic matter
There is a clear relation visible in T6 between pH and SOM (fig. 12). A high pH corresponds with a lower SOM content. In the maps it can be seen that when the pH is lower, the vegetation cover is higher and therefore the SOM content is also higher. When the pH decreases and the SOM content increases, the bulk density decreases (fig. 12). This decrease in bulk density can be traced back to the amount of SOM in the soil. Sand is heavier than SOM and therefore the bulk density decreases when the SOM content increases.
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Results T8
pH
The lowest pH values are found in T1 where the pH is approximately 6.4. T2 and T3 have intermediate pH values of around 6.8. In the southern part of T4 higher pH values of around 7.4 can be found.
Vegetation cover
In T1, the whole transect has a vegetation cover of 100%. Both T2 and T3 have a varied vegetation cover that ranges from
approximately 70% to 100%. With one patch of bare soil which is located between the transects. In the southern part of T4 bare soil patches can be found, with a vegetation cover of 0-50%.
Figure 13 pH in dune slack T8
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Soil organic matter (SOM)
The highest SOM content can be found in T1 (0.0-0.15). The SOM content in T2/3/4 is quite low in comparison with T1 (0.0-0.06).
Boxplots
The bulk density decreased marginally from a median of around 1.55 in 2010 to a median of around 1.45 in 2015. In 2018 the difference between the bulk density within the transects is shown. The bulk density in T1 dropped to a median of around 1.05, whereas the bulk density in T2 and T3 decreased marginally to 1.45 and 1.4 respectively. In T4 the bulk density increased to a median of around 1.5 in 2018.
The pH decreased from a median of 7.2 in 2010 to a median of around 6.85 in 2014. After that, the pH increased in 2015 to a median of around 7.25. In 2018 the pH decreased significantly in T1 to a median of around 6.5. In T2/T3/T4 the pH also decreased to a median of around 6.6 in T2 and T3 and a median of 7.0 in T4.
Figure 16 Bulk density in dune slack T8 Figure 15 Soil organic matter content in dune slack T8
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Combined results
In T8 a clear correlation is visible between pH and vegetation cover. A high pH corresponds with a low vegetation cover (fig. 17). The maps confirm this correlation. A higher pH correlates with a lower vegetation cover (T8-T1). When the vegetation cover is high, there is more SOM in the soil. This results in lower bulk density measurements.
Figure 17 Correlation between pH and vegetation cover
Discussion
During the research a number of limitations have been encountered. In this chapter these limitations are discussed.
Lack of data
In the first place the aim of this research was to investigate whether the storm of January 2018 has affected the dune slacks T6 and T8, with in particular the habitats of Liparis Loeselii. Unfortunately it was not possible to investigate this due to a lack of data from the previous years. There was only data available from the years 2010,2014 and 2015. Thus comparisons of before the storm and after the storm could not be made. Therefore the research aim was changed. Now it was decided to investigate the impact of aeolian activity on dune slacks T6 and T8 instead. Nevertheless there was still a lack of data from the previous years. In the years 2010,2014 and 2015 only 8 samples of dune slack T6 were taken and dune slack T8 only had 4 samples each year. This made it difficult to
compare and do statistical analysis on the previous years with 4-8 samples and this year (2018) with 70 transects points and 282 grid points. To accommodate for the lack of data, boxplots were made. However, these boxplots are still not reliable because of the small datasets. Furthermore there were no aerial photographs available of this year because they were not yet made. Therefore the effects on the vegetation pattern and bare sand cover according to the aerial photographs could not be included in the research.
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Reliability of collecting soil samples
The results of the bulk density in our research did not correspond with what is stated in the literature. In the literature is defined that when succession takes place, the pH decreases, the
vegetation cover and the soil organic matter content increases and the bulk density decreases due to a larger amount of soil organic matter, which is lighter than sand (Kooijman et al., 2016). In this research the bulk density in dune slack T6 transects 2 and 3 increased between previous years and this year whereas the pH decreased (fig. 18; fig. 19)).Which is not in line with the literature. The differences of these measurements can have multiple explanations. First it can be due to sampling differences between the years. The bulk density is measured with a metal pF ring, with witch a certain amount of soil can be collected. This is done by different individuals who can have different methods of sampling. As the amount of soil that is collected directly affects the bulk density measurement, reliability of these measurements can be questioned. A second explanation can be the fact that when succession occurs the soil is covered with more vegetation, which results in more roots in the soil. When sampling the soil samples for the bulk density, roots can be found in the pF ring. When these roots are removed from the sample, the bulk density measurement will be lower due to a loss of soil from the sample. Tempering with the sample can affect reliability of the
measurement. The last explanation can be that aeolian activity caused a deposit of bare sand on the soil which results in a higher bulk density, because sand is heavier than soil organic matter. However when aeolian activity is the case, the pH is assumed to increase (Kooijman et al., 2016). The change in pH is not yet visible in the results (fig. 18; fig. 19).
17 Figure 19 Bulk density in dune slack T6-T2
Making conclusions on possibly false premises
According to vegetation cover and the soil organic matter content of transect 1, dune slack T8 was considered to be the most stable transect of T8. The vegetation cover is high and the vegetation consists mostly of shrubs. Furthermore the soil organic matter content is high due to this high
vegetation cover. Both a high soil organic matter content as a high vegetation cover are indicators for succession. However the pH in transect 1 is approximately 6.4, this is considered to be a suitable pH for the growth of Liparis Loeselii (Kooijman et al., 2016). In the literature it is stated that the pH is a more important indicator than the soil organic matter content (Kooijman et al., 2016). This would mean that transect 1 should be a suitable habitat for Liparis Loeselii. But in this case it appears to be questionable as this transect is considered to be stable due to the large amount of vegetation in the form of shrubs.
In the maps that contain the pH measurements, different legends are used. In dune slack T6 the pH ranges from 5.9-6.9 whereas in dune slack 8 the pH ranges from 6.3-7.5. Because the differences between the pH values in dune slack T6 were very small it was necessary to use a different legend to be able to distinguish differences of pH measurements. When comparing dune slack T6 with dune slack T8 conclusions might be questionable and one should be aware of this problem when analysing the data.
In dune slack T6 a vegetation cover of 100% is prevalent in the three transects. The fact that a 100% vegetation is found would indicate that the succession is already highly developed. But this is only the case when it concerns shrubs. In our research however this was not the case as the 100% vegetation cover mainly existed of mosses. Drawing conclusion based on vegetation cover percentages could be inaccurate.
Upscaling to larger scales
On a positive side, although for this research it was difficult to compare with previous years as stated above, we were the first year that made transects and a grid. Therefore future researches can elaborate on this research which makes this research project a good basis for these particular dune slacks, providing enough data for the coming years to draw conclusions about the effect of aeolian activity and storms on the dune slacks.
Having achieved to collect data in an area that is highly dynamic and is thus representative for measuring the effect of aeolian activity and finding out the difficulties concerning reliability of
18 colleting appropriate soil samples from this research area. It will now be possible to conduct a larger study in the same area with reliable datasets. And furthermore this will enable us to implement the same methodology on different locations to study the problem of aeolian acitivity and succession on a more global scale.
Conclusion
Most data that was collected was in line with data from earlier publications on this subject. However we also found conflicting data. The data of bulk density was not consistent with findings in other publications so this data was not documented in the results.
According to the pH range, vegetation cover and soil organic matter content transect 3 in T6 and transect 1 in T8 are the most ‘stable’ transects. The pH in these transects are low in comparison with the other transects. Furthermore the vegetation cover and therefore also the soil organic matter content is higher than in the other transects. This is caused by succession which brings forth a lower pH and therefore a less suitable habitat for Liparis Loeselii. The other transects are less affected by succession. The pH is still quite high, the vegetation cover is lower and the soil organic matter content is higher. From this it can be concluded that transect 2 and 3 in T6 and transects 3,4 and 5 in T8 are the more ‘dynamic’ transects. Dynamic transects are influenced by sand deposits through aeolian activity and sometimes water. In these transects aeolian activity plays a role in setting back succession. Bare sand is deposited, this causes an increase in the pH which makes the soil more suitable for the growth of Liparis Loeselii.
The optimal pH for the growth of Liparis Loeselii lies between 5.8-7.5. According to the pH the most suitable habitats for Liparis Loeselii are located in transect 2 and a part of transect 3 in dune slack T6 and in transect 1 of dune slack T8 (fig. 20). However transect 3 in T6 and transect 1 in T8 are the more stable parts of the dune slacks, which indicate that succession occurs and that the soil is less favourable for the growth of Liparis Loeselii. In both transects the vegetation cover is almost 100% in the entire transect, and the type of vegetation is mostly shrubs. Therefore we expect that these parts of the dune slacks are not suitable habitats for Liparis Loeselii. However, in the southern part of Figure 20 Optimum pH values in dune slacks T6 & T8
19 transect 4 of dune slack T8 high pH values are measured and the vegetation cover is low (fig. 14; fig. 20). Patches of bare sand are found there. We assume the pH value to decrease in the coming years. Therefore we expect the southern part of transect 4 of dune slack T8 to be the most favourable location for the growth of Liparis Loeselii in the near future.
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References
Odé, B., and Bolier, A., 2003, Groenknolorchis op de kaart: Gorteria, v. 29, p. 33-37
Sha, L.P., 1990, Sedimentological studies of the ebb-tidal deltas along the West Frisian Islands, The Netherlands
Westhoff, V.,Van Oosten, M.F., 1991, De plantengroei van de Waddeneilanden: Utrecht, Stichting Uitgeverij Koninklijke Nederlandse Natuurhistorische Vereniging, 417 p.
van Dijk,H.W.J., Grootjans,A.P. (1993). Wet dune slacks: decline and new opportunities.
Hydrobiologica 265, 281-304
Grootjans,A.P., Geelen,H.W.T., Jansen,A.J.M., Lammerts, E.J. (2002). Restoration of coastal dune slacks in the Netherlands. Hydrobiologia 478, 181-203
Kooijman,A.M., Bruin,C,J,W., van de Craats,A.,Grootjans,A.P.,Oostermeijer,J.G.B., Scholten,R., Sharudin,R. (2016). Past and future of the EU-habitat directive species liparis loeselii in relation to landscape and habitat dynamics in SW-Texel, the Netherlands. Science of the total environment, 568, 107-117
Oostermeijer,J.G.B., Hartman,Y. (2014). Inferring population and metapopulation dynamics of liparis loeselii from single-census and inventory data. Acta Oecologica 60, 30-39
Klijn, J.A., 1981, Nederlandse kustduinen: geomorfologie en bodem: Wageningen, Pudoc Best, E. P. H., Verhoeven, J. T. A., Wolff, W. J.(1993). The ecology of The Netherlands wetlands: characteristics, threats, prospects and perspectives for ecological research. Hydrobiologica, 265, 1– 3, pp 305–320
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Appendixes
TRANSECT FIELDFORM GPS coordinates: Dune slack (T6/T8): Transect (1/2/3/4): Sampling point: Date: Notes: Samples to take:Two pF-ring soil samples (100cm3)
Soil profile description Thickness of top sand layer (mm): Water Table:
Surface characteristics
Coverage of bare sand (%):
Type(s) of vegetation and % when present
Moss: Herbs: Shrubs: Vegetation cover (%): TRANSECT FIELDFORM GPS coordinates: Dune slack (T6/T8): Transect (1/2/3/4): Sampling point: Date: Notes: Samples to take:
Two pF-ring soil samples (100cm3)
Soil profile description Thickness of top sand layer (mm): Water Table:
Surface characteristics
Coverage of bare sand (%):
Type(s) of vegetation and % when present
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Moss: Herbs: Shrubs:
GRIDPOINT FIELDFORM GPS coordinates: Dune slack (T6/T8): Sampling point: Date: Notes:
Topsoil layer Thickness of top sand layer (mm):
Depth: Type:
Surface characteristics
Coverage of bare sand (%):
Type(s) of vegetation and % when present
Moss: Herbs: Shrubs: Vegetation coverage (%): GRIDPOINT FIELDFORM GPS coordinates: Dune slack (T6/T8): Sampling point: Date: Notes:
Topsoil layer Thickness of top sand layer (mm):
Depth: Type:
Surface characteristics
Coverage of bare sand (%):
Type(s) of vegetation and % when present
Moss: Herbs: Shrubs: Vegetation coverage (%): GRIDPOINT FIELDFORM GPS coordinates: Dune slack (T6/T8): Sampling point: Date: Notes:
Topsoil layer Thickness of top sand layer (mm):
23
Surface characteristics
Coverage of bare sand (%):
Type(s) of vegetation and % when present
Moss: Herbs: Shrubs: Vegetation coverage (%):
