Active blowouts as management measure for grey dunes on Texel
What is the impact of an active, natural blowout in the grey dunes in de Koog (Texel, The Netherlands) on biodiversity and soil characteristics compared with a stabilized zone?
Bachelor (BSc) thesis E.M. Kolb (10737235) Bèta Gamma Earth Sciences, University of Amsterdam
A.M. Kooijman & J.H. van Boxel July 2nd 2017 Wordcount: 4398
2 Active blowouts as management measure for grey dunes on Texel
What is the impact of active, natural blowouts in the grey dunes in de Koog (Texel, The Netherlands) on biodiversity and soil characteristics compared with a stabilized zone? July 2nd, 2017
Photo front page: Spek, E. van der. (2017)
BSc applicant
Eline Marianne Kolb Student number: 10737235 Email: eline.kolb@student.uva.nl
Bsc Bèta Gamma Earth Sciences University of Amsterdam
Supervisor & First assessor
Dr. Annemieke M. Kooijman
Institute of Biodiversity and Ecosystem Dynamics (IBED) University of Amsterdam
Second assessor
Dr. John H. van Boxel
Institute of Biodiversity and Ecosystem Dynamics (IBED) University of Amsterdam
3 Abstract
The grey dunes in the coastal area of the Netherlands have suffered from the processes of eutrophication and acidification over the past decades, caused by the deposition of
atmospheric inorganic nitrogen. Active blowouts in grey dunes can be effective as a natural measure for enhancing the biodiversity in species-rich grey dunes and slow down processes of acidification and eutrophication in the soil. The purpose of this study was to investigate the effects of natural, active blowouts on the effects of nitrogen deposition by comparing an active, natural blowout zone with a stabilized zone in the grey dunes in de Koog (Texel, the Netherlands) A field survey, lab analyses and ArcGIS analyses have been used to analyze the differences in soil and vegetation characteristics between a natural blowout and a stabilized zone. It was concluded that the pH in the active blowout area was higher, caused by
deposition of sand and formation of sand deposited layers. A higher number of species occurred in the active blowout zone, when the blowout was excluded. The number of species increased when the C/N ratios of the soil decreased. In contrast, the stable zone had a lower pH, a thicker Ah layer and higher contents of soil organic matter and soil C and N contents compared with the active zone. Herbs cover and biomass of plants were higher in the stable zone and indicate grass encroachment and slower decomposition of organic matter which are traits of older dune soils. Only two zones have been analyzed, so the results should be
interpreted carefully. However, based on the results of this study, it can be concluded that a natural, active blowout can have a positive influence on biodiversity, a negative influence on soil acidification in the lime-poor grey dunes in the Wadden district and counteract grass encroachment.
Nederlandse samenvatting
Stikstofdepositie is de laatste decennia afgenomen, maar blijft grote effecten hebben op bodem en vegetatie in duingebieden langs de Nederlandse kust. In de kalkarme grijze duinen kunnen stuifkuilen voor een toename in biodiversiteit en veranderingen in de bodem rondom de stuifkuil zorgen. In dit onderzoek zijn verschillen in vegetatie, diversiteit en
bodemkarakteristieken tussen een gebied met een stuifkuil en een gebied met een gestabiliseerde stuifkuil in de kalkarme, grijze duinen bij de Koog (Texel, Nederland)
geanalyseerd, met behulp van veldonderzoek, labonderzoek en GIS analyses. Uit deze studie blijkt dat in het gebied met de actieve stuifkuil, de pH van de bodem hoger is en positief gecorreleerd is aan het percentage kaal zand in het gebied. Ook is de soortenrijkheid hoger, met uitzondering van de blowout zelf. In het stabiele gebied is een hoger percentage grassen
4 aanwezig, en is het mosgehalte significant lager in vergelijking met het gestabiliseerde
gebied. In de bodem is een dikkere Ah lag gevonden met hogere koolstof en stikstofgehaltes, wat lage decompositiesnelheden aangeeft en een kenmerk zijn van N depositie. De resultaten van dit onderzoek bevestigen dat een actieve, natuurlijke stuifkuil kan zorgen voor nieuwe successie in de kalkarme grijze duinen, door verandering in bodemkarakteristieken en vegetatie door het verspreide zand uit de stuifkuil in het gebied.
5 Table of contents Abstract ... 3 Nederlandse samenvatting ... 3 Abbreviations ... 6 1. Introduction ... 7 2. Theoretical framework ... 8 3. Field description ... 10 4. Methods ... 11 4.1 Fieldwork ... 11 4.2 ArcGIS analyses ... 12 4.3 Lab analyses ... 12 4.3.1 Soil analysis ... 12 4.3.2 Plant analysis ... 13 4.4 Statistical analyses ... 13 5. Results ... 14 5.1 Vegetation parameters ... 14 5.2 Soil parameters ... 16
5.3 Soil and Vegetation interactions... 19
6. Discussion ... 20
6.1 Influence of blowout activity on nitrogen deposition: soil characteristics ... 20
6.2 Influence of blowout activity on nitrogen deposition: vegetation characteristics ... 21
6.3 Influence of blowout activity: interactions between soil and vegetation ... 22
6.4 Implications ... 22
7. Conclusions ... 23
List of references ... 24
Appendix ... 27
A. Field survey data summary table ... 27
B. Statistical analysis summary tables ... 31
6 Abbreviations
BD Bulk density
C Carbon
CaCO3 Calcium carbonate
CO2 Carbon dioxide
EC Electrical conductivity
GIS Geographic information system H2130A Grey dunes (lime-rich)
H2130B Grey dunes (lime-poor)
HCl Hydrochloric acid
N Nitrogen
P Phosphorus
pH Acidity
rpm Rounds per minute
7 1. Introduction
Grey dunes in the coastal area of the Netherlands have suffered from the processes of
eutrophication and acidification over the past decades, which are caused by the deposition of atmospheric inorganic nitrogen (N) (Kooijman et al., 2005). According to van Breemen & van Dijk (1988), the atmospheric input of inorganic N in the Netherlands is one of the highest in the world. Levels of atmospheric N have increased globally since the 1940s due to vehicle emissions, industry, agriculture and domestic combustion (Jones et al., 2014). Additionally, N deposition from the North sea affects the coastal area of the Netherlands (Kooijman et al., 2016). As a result, the critical deposition value of 8-15 kg N per hectare per year (kg/ha/yr) of the lime-poor grey dunes in the
Netherlands is exceeded (van Dobben, 2012). This results in accelerated succession, a decline in the biodiversity, shifts in species composition, grass encroachment,
acidification of the soil and changes in the biochemical cycle in the grey dunes (Jones et al., 2014).
Various measures against acidification and eutrophication are already taken to protect the grey dunes. Since 1990, the emissions of atmospheric N across Europe have decreased with a quarter (Figure 1) due to policy measures (Jones et al., 2014). According to the RIVM (2016), the average N deposition in the Netherlands decreased from 2700 mole/ha to 1600 mole/ha between 1990-2015 (Figure 1). Grey dunes became a priority habitat type of the European Union Habitats Directive (Provoost et al., 2004) and ministries developed monitoring programs with help of research institutes to understand the impacts of N deposition in the Dutch coastal area (Kooijman et al., 2005), and to provide measures against the negative effects. The measures provided over the past decades include natural management and
artificial measures. Grazing and sand deposition of blowouts can be an effective way to enrich the vegetation abundance and slow down the processes of soil acidification and eutrophication in several areas along the Dutch coast (Kooijman et al., 2005).
Figure 1: Noordijk (2007). Average yearly Nitrogen deposition between 1999-2004 in the Netherlands. The critical deposition value of grey acidic dunes is 571-1071 mole/ha/yr (van Dobben, 2012).
8 The aim of this research is to establish whether active, natural blowouts can be effective against biodiversity decline, accelerated succession by grass encroachment and soil
acidification caused by N deposition, and improve habitat conditions in the lime-poor grey dunes in de Koog, Texel. Therefore, an active, natural blowout zone and a stable zone have been compared on soil and vegetation characteristics, and samples were compared and correlated.
2. Theoretical framework Habitat types in the coastal dunes
The coastal dunes in the Netherlands consist of embryo dunes, white dunes and grey dunes (Arens et al., 2013a). Grey dunes are species-rich dry grasslands. The vegetation mostly contains grasses, herbs, lichen and mosses (Arens et al., 2013a). H2130A is lime-rich, with a calcium carbonate (CaCO3) content of 2-10% and a pH of 6,5 at the soil surface (Kooijman et al., 2005), and H2130B is poor in CaCO3, with a content of 0,5-2% and a pH of 3.5 at the soil surface. C/N ratios in lime-poor soils are high and decomposition rates of litter are low compared to calcareous soils (Kooijman & Besse, 2002).
The dunes on the island of Texel, are located in the Wadden district and poor in CaCO3 (Kooijman et al., 1998; Kooijman et al., 2005). The Wadden district used to be a lagoon and the shoreline was located further in the North sea than in present times. This causes the absence of lime-rich shells (Eisma, 1968; Kooijman et al., 2005). Lime-rich dune soils do have a buffer capacity which slows down the processes of decalcification, whereas lime-poor soils have lower buffer capacity which results in faster rates of acidification (Kooijman et al., 2005.
The processes of acidification and eutrophication
Atmospheric N deposition has been observed from 1935 (Kooijman et al., 2005). In the end of the 1980’s monitoring projects were started to understand the impact of atmospheric N deposition on ecosystems (Figure 2) and to provide measures against the negative effects.
9 Figure 2: Impact of increased N concentrations on ecosystems (Bobbink & Hettelingh, 2011, p. 22).
Acidification of grey dune soils occurs naturally when there is no mobilisation of sand (Aggenbach et al., 2016a). This is a slow process, caused by the dissolution of CaCO3 and loss of base cations. Acidification lowers buffer capacities and pH in grey dunes. Lime-poor grey dunes are more sensitive to N deposition than lime-rich dunes due to the lower buffer capacity. Eutrophication occurs when there is increased N availability, which stimulates plant productivity and rates of nutrient cycling in N limited ecosystems (Jones et al., 2014). The species composition shifts, less vascular plants and mosses occur whereas grasses increase (Jones et al., 2014). Nitrogen availability is higher in Dutch coastal dune grass soils with a low pH , than in calcareous soils and closely related to SOM (Kooijman & Besse, 2002). The grey dunes (H2130B) that occur in the area of research are extremely sensitive to nitrogen deposition and have a critical deposition value of 8-15 kg/ha/year (van Dobben et al., 2012). Geomorphology of blowouts
“A blowout is a saucer-, cup- or through-shaped depression or hollow formed by wind erosion on a pre-existing sand deposit” (Glenn & McKee, 1979; Carter et al., 1990; Hesp, 1996; Hesp, 2002). Blowouts can affect several hectares with their sand spray which results in a dune zone with younger vegetation types surrounded by older ones (Arens et al., 2013b). In stabilized
10 zones where the blowout is inactive, pioneer stages become rare which causes a decrease in biodiversity (Arens et al., 2013b).
3. Field description
Texel is the southernmost barrier island of the Wadden Sea, located in the Northwest of the Netherlands (van Heteren et al., 2006). The fieldwork area (Figure 3), active blowouts and stabilized zones are present (Figure 4). The blowout has a surface of 150m2, based on aerial photos (Google Maps, 2017). The blowout zone and stabilized zone are both 470*150 meters. The area of the field survey is a protected dune area with a temperate climate and sandy Arenosols (IUSS Working Group, 2006) .
Figure 3: Aerial photos of the Netherlands and fieldwork area (Google Maps, 2017) with the blowout zone (green) and stable zone (blue).
11 4. Methods
4.1 Fieldwork
Models were developed with Paint (Figure 5). In the field, the exact location of the two zones was determined, and with Trimble Yuma 2, a transect and a grid were plotted in ArcMap (Figure 6).
Figure 5: Model of transect A (left) and model of grid A (right).
The grids both contain 150 sites with a radius of 2 meters, of which bare sand, shrubs, mosses and herbs percentages have been estimated. Additionally, a soil profile of 0,20 meters depth was made to measure the depth of the Ah layer and sand shifted (S) layers.
The transects contained 20 points (figure 6). A soil profile with a depth of 1,20 meters was made, 300 cm3 of soil were collected to measure the bulk density (BD) and additional soil characteristics. Vegetation plots of 25*25 centimeters were made and vegetation cover was cut.
12 4.2 ArcGIS analyses
Maps of the bare sand, shrubs, mosses and herbs percentages and thickness of the Ah and S layer in the blowout and stabilized zone have been produced in ArcMap 10.4. Spline
interpolation with the Spatial analyst tool was used to create maps. 4.3 Lab analyses
4.3.1 Soil analysis
Locked bags with 300 cm3 of soil have been weighted and unlocked. The bags were stored in an oven for 48 hours at 40°C, however 5 grams of each sample were removed and stored in an oven for 24 hours at 105°C. The part that was stored at 40°C has been sieved at 2mm sieves afterwards to remove most of the roots and large particles which can influence the results. 4.3.1.1 Bulk density
300cm3 of soil was collected in the field with 3 pF rings and a spade. The BD was calculated with the formula (1) by Cresswell & Hamilton (2002).
4.3.1.2 pH and electrical conductivity
10 grams of the sieved soil samples of both transects were stored in tubes with 25 milliliters of demi water. The tubes were shaken for 2 hours and after 14 hours, the samples were shaken for 30 minutes. Finally, the pH and electrical conductivity (EC) was measured with a pH and EC electrode.
4.3.1.3 Carbon and Nitrogen
The dried and sieved soil samples were milled for 5 minutes at 400rpm. Around 40-60 mg of the milled samples have been weighted in tin cups with tweezers. The C(%) and N(%) of the samples were measured in duplicates in the Elementar Vario EL. SOM was calculated out of this total organic carbon (C) of the soil samples. With help of the formula (2) with a
conversion factor of 1.72 (Schumacher, 2002), the SOM content was established. Organic matter (%) = Total organic carbon (%) * 1.72 (2)
13 4.3.1.5 Calcium carbonate
5 grams of milled sample was weighted in an Erlenmeyer flask with a test tube with 4M hydrochloric acid (HCl). The Erlenmeyer flasks were closed with polyethylene caps. The test tubes with HCl were emptied before shaking, to start the reaction. Two reference Erlenmeyer flasks were filled with 250 milligrams CaCO3 and HCl tubes, and two blanco Erlenmeyer flasks with HCl tubes. In a Wesemael machine, all flasks were shaken for 26 hours, to let CaCO3 react with HCl into carbon dioxide (CO2) (Wesemael, 1955). The weight before and after the reaction with HCl was used to calculate the CO2% and the CaCO3% in the samples with formulas (3a and 3b) (Wesemael, 1955), and the mole mass of CO2 (44) and the mole mass of CaCO3 is 100.
4.3.2 Plant analysis 4.3.2.1 Dry weight
The samples of the plants were dried in an oven for 48 hours at 40°C in unlocked bags. The weight of the plants was measured before and after drying.
4.3.2.2 Carbon and Nitrogen
The dried plants were cut in small pieces and pulverized with a speed of 8000 rpm. 5-10mg of the milled samples was weighted in tin cups for the C and N content measurement in the Elementar Vario EL.
4.4 Statistical analyses
In Matlab 2016, all data has been initiated and the mean, standard deviation, minimal and maximal values were calculated. With independent t-tests the significance of differences between the active blowout and stabilized blowout zone have been established. However, for the number of species, mosses, vascular plants and C/N ratios of the soil, the zones have been subdivided (Table 1). This was done to reduce the unrealistic values of the C/N ratios in the blowout. For vegetation species, this was done to reduce the effect of the blowout itself on the
14 number of vegetation species, and the deposited sand differed per location. For the soil C content, soil N content and soil C/N ratios, the zones have been divided in an unaffected, blowout and accumulated area.
Table 1 different zones
Pearson correlations between all soil and vegetation parameters were calculated in Matlab. Levels of significance for both t-tests and Pearson correlations were 0.05.
5. Results
5.1 Vegetation parameters
Differences in vegetation characteristics were significant (p<0.05) between the active zone and the stable zone for herbs cover, mosses cover, C content of the vegetation, N content of the vegetation, plant C/N ratios and dry weight of the vegetation (Appendix B, Table 2). The dry weight was significant higher in the stable zone, compared with the blowout zone. Both the C and N contents of the stabilized zone were higher than of the blowout zone, as well as the plant C/N ratios.
15 A significant higher number of species occurred in the active zone, compared with the stabilized zone (Figure 7). However, the blowout group contained more species in the stabilized zone. More vascular plant species were found in the accumulated group of the active zone whereas more mosses species were only present in the unaffected group. However, a higher percentage of mosses was found in the active zone (Figure 8). Herbs cover was significant higher in the stable zone (Figure 9), whereas shrubs cover did not significant differ between both zones (Figure 10). The shrubs cover of the stable zone had a higher average.
Figure 8: Cover of mosses of the active zone (left) and the stable zone (right).
Figure 9: Cover of herbs of the blowout zone (left) and stable zone (right).
0 5 10 15 20 25 30 Sp ecie s (c o u n ts )
Number of species between zones
means zone A means zone S
16 Figure 10: Cover of shrubs (%) of the active blowout zone (left) and the stable zone (right).
Pearson correlations were positive significant for C and N content of the vegetation
(Appendix B). C/N ratios of vegetation were positive correlated with species diversity (Figure 11).
5.2 Soil parameters
Differences in characteristics of the soil between the active zone and the stable zone were significant for BD, pH, thickness of the organic layer, thickness of the S (sand deposited) layer, bare sand cover and SOM (Table 3).
Table 3: independent t-tested soil parameters
pH, BD and thickness of the S layer were significant higher in the active zone and the C and N content, SOM were significant lower in the active zone (Table 3). No significant
differences in CaCO3 contents, EC values and moisture content between the active blowout and stabilized area were found in this study. However, significant positive Pearson
17 correlations between EC and soil moisture content, C and N content of the soil were found (Appendix B).
Differences in C/N ratios between the active zone and the stable zone were significant in the accumulated area (Appendix B). In the unaffected area, the C/N ratio of the stable zone was higher, but not significant. C content of the soil was significant higher in the
accumulated area of the stable zone (Figure 11). N content of the soil was significant higher in the accumulated and the blowout area of the stable area.
Pearson correlations were significant for many soil parameters (Appendix B). Highest significant positive correlation were found between bare sand cover and pH (Figure 12), and between pH and S layer thickness (Appendix B). A strong significant positive correlation between C and N content of the soil was found (Appendix C).
High negative correlations were found between BD and C and N content of the soil, and between pH and C and N content of the soil. The BD decreased when the SOM and thickness of the Ah layer increased. pH and BD had comparable correlations 0 0,2 0,4 0,6 0,8 1 1,2 1,4 1,6 1,8 Min era l con ten t (g/ m 2)
Average soil C and N content
N content C content R² = 0,5912 0 10 20 30 40 50 60 70 80 90 100 4 5 6 7 8 9 Bare San d (% ) pH
Bare Sand - pH
Figure 12: Correlation between pH and bare sand
18 for most parameters (Appendix B).
Figure 13: pH value per sample over transects, side view and front view
The pH was significant higher in the active zone. The pH of the soil showed the highest values at sample 6 and 7 of the active zone (Figure 13), which was located in the blowout.
Figure 14: Ah layer thickness of the active zone (left) and stable zone (right).
Figure 15: S layer thickness of the active zone (right) and stable zone (right).
4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 10 11 12 13 14 PH V A LUE SAMPLE NUMBER
pH over zones side view
pH A pH S 4 6 8 20 19 18 6 15 16 17 PH V A LUE SAMPLE NUMBER
pH over zones front
view
19 Figure 16: over of the bare sand of the active zone (left) and stable zone (right).
Significant differences between the blowout zone and the stable zone were present for thickness of the Ah layer, which was higher in the stable zone (Figure 14), and thickness of the S layer (Figure 15) and bare sand cover of the soil (Figure 16), which were higher in the active zone.
5.3 Soil and Vegetation interactions
Certain soil- and vegetation parameters showed significant Pearson correlations (Appendix B). pH and herbs cover were negative correlated, as well as the pH and C and N content of vegetation (Appendix B), and plant C/N ratio. BD showed comparable correlations. High negative correlations between plant C/N ratios and bare sand cover and thickness of the S
layer were present, whereas positive correlations of plant C/N ratios and thickness of the Ah layer were found. Significant negative correlations were found between total number of species, mosses and vascular plants and soil C/N ratios (Figure 17) . R² = 0,2007 R² = 0,4109 R² = 0,3298 0 5 10 15 20 25 30 35 6,00 8,00 10,00 12,00 14,00 N u m b er o f speci es soil C/N ratios
Species - soil C/N ratios
Nr of vascular species Nr of mosses
Total nr of species Lineair (Nr of vascular species) Lineair (Nr of mosses) Lineair (Total nr of species)
20 6. Discussion
High atmospheric N deposition in grey dunes causes accelerated succession, grass
encroachment, a decline in biodiversity, soil acidification and changes in the biochemical cycle in vulnerable ecosystems. Lime-poor grey dunes are ecosystems that are vulnerable to N deposition and critical deposition values are exceeded. Providing more knowledge about N affected ecosystems and how to restore them is therefore important. In this study, an active, natural blowout zone and a stabilized blowout zone in the grey, lime-poor dunes at de Koog, Texel, were compared to establish the hypothesis that active, natural blowouts can be
effective against the negative effects on soil and vegetation characteristics caused by atmospheric N deposition.
6.1 Influence of blowout activity on nitrogen deposition: soil characteristics
Blowout activity does affect several soil characteristics of lime-poor grey dune soils, based on the results of this study. The active, natural blowout zone in this study shows a higher pH, a thicker S layer and higher percentages of bare sand cover. Additionally, pH and sand cover show positive correlation, as well as pH and thickness of the S layer. Based on these results, it can be concluded that the blown sand of the blowout enhances the pH of the soil in the whole zone, and counteracts soil acidification. When more bare sand cover is present and the pH is higher, pioneer species can grow and enhance the biodiversity of the area (Kooijman et al., 2005). According to Aggenbach et al. (2016b), this also indicates for early stages of
succession. Succession rate and soil development in dry dune landscapes, are largely dependent of decomposition rates of SOM and nutrient cycling. When the pH decreases, decomposition and mineralization of SOM slows down which results in an increase of humus content (Aggenbach & Jalink, 1999; Provoost et al., 2002). In this study, the BD of the soil in this study is significant higher in the active zone, and negative correlated with SOM. High BD indicates for coarser structures of the soil (Adams, 1973; Rawls & Walter, 1983), which also indicates for higher sand content.
Younger dune soils are covered with low, productive pioneer species, such as small grasses and mosses (Grootjans et al., 2013). The SOM content in these soils is low and pH is higher. The blowout zone in this study, shows characteristics of younger dune soils that causes new succession phases. In older dune soils, the decomposition rate of SOM increases, whereas pH decreases, and the availability of N increases (Grootjans et al., 2013). In the stable zone, a significant higher N content of the soil is found and thus can be confirmed by the results of Grootjans et al. (2013). C/N ratios of the soil can also be related to the decomposition of SOM
21 (Kooijman et al., 2005). When the decomposition of SOM slows down, the C/N ratios of the soil increase. In the results of this study, both higher SOM contents and C/N ratios are found the stable zone. This indicates that the biochemical cycles are different between the zones.. Based on these results, it can be concluded that soil acidification and accelerated succession can be counteracted by active, natural blowouts in lime-poor grey dunes and changes the biochemical cycle.
The EC gives information about nutrient conditions of the soil, and can be used as a parameter for biological activity (Smith & Doran, 1996). Contrastingly than expected, no significant differences in EC between both zones are found, and no clear correlations with SOM and pH are present. However, significant positive Pearson correlations are present between EC and soil moisture, and between EC and C and N content of the soil. The lime-poor dune soils in this study contain a low percentage of CaCO3 and no significant difference between both zones is found in this study or significant Pearson correlations are found. However, high lime-contents make grey dunes less vulnerable for N deposition and these low lime-contents (Appendix B) indicates for a vulnerable habitat.
6.2 Influence of blowout activity on nitrogen deposition: vegetation characteristics
When the soil is acidified by N deposition, changes in vegetation follow. Grass encroachment is an important negative effect of N deposition. In this study, differences in vegetation
between the active blowout zone and stable zone are present and indicate that higher grass encroachment is present in the stable zone compared with the active zone. Herbs cover include grasses, and is higher in the stable zone compared with the active blowout zone. According to Veer & Kooijman (1997), grass encroachment has a negative influence on the availability of light and as a result, species diversity declines, especially mosses and lichen diversity. Low numbers of species are found in the stable zone compared with the active zone, which indicates that blowout activity enhances biodiversity. Also, mosses cover was higher in the blowout zone, probably due to higher availability of light.
Biomass of the vegetation in the stable zone is higher in comparison with the active blowout. According to Jones et al. (2004), the higher atmospheric N inputs, the higher plant biomass and the lower species richness. In this study, mosses cover and number of total species, number of mosses and number of vascular plants are all lower in the stable zone. Positive correlation between biomass and herbs cover indicates grass encroachment, however no relation between the number of species and biomass is found in this study. Also between
22 herbs cover and species richness, no correlations were found. Tall grasses cover and species might have given a high negative correlation, however in this study no distinction is made between tall grasses species and smaller vascular plants.
6.3 Influence of blowout activity: interactions between soil and vegetation
Vegetation and soil characteristics are closely related and in this study, relations are present. pH is a soil characteristic that according to Isermann (2005) can be positive related to species diversity. In this study, no strong correlation between pH and species richness is found. However, the active blowout area, with higher pH does contain more species compared with the inactive blowout area. In contrast, the C/N ratios of the soil show a negative correlation with species richness, which indicates that grass encroachment that leads to a decline in species diversity.
High C and N contents of the soil indicate grass encroachment. In this study, P-availability has not been taken into account. However, studies suggest that high grass encroachment in the lime-poor grey dunes in the Wadden district can be related to high levels of P (Kooijman et al., 2016). The availability of P has not been measured, however this may also be a good indicator for the soil characteristics.
Some indicator species can be related to soil characteristics. Crowberry is an indicator species for acidified soils (Tybirk et al., 2000). In the stable zone, more crowberry is present
compared with the active zone (Appendix C). Another indicator species are marram grasses. This species is stimulated by blown sand, however classified as a problematic species (Kooijman et al., 2004). Blowouts can be a good measure, however there are thus negative effects.
6.4 Implications
This study does have implications. 40 soil and vegetation samples were collected. However, more samples would have given a higher statistical power. Results which are influenced most by low statistical power are C/N ratios of the soil and number of total species, mosses and vascular plants because of subdivision in smaller groups to exclude influences of the blowout. Another implication is that only two zones in lime-poor grey dunes have been compared. Further research needs to be done in other areas along the Dutch coast to establish the effects of active, natural blowouts in lime-rich grey dunes on soil and vegetation characteristics. In lime-poor grey dunes, grass encroachment is higher than in lime-rich areas (Kooijman et al., 2016). Further research needs to be done, to see whether active, natural blowouts do influence
23 the soil and vegetation characteristics in lime-poor grey dunes different, than in lime-rich grey dunes.
Additionally to lime contents, blowouts occur in different morphological types. In this study, a saucer formed blowout, based on the types described by Hesp (2002) was analyzed.
Differences in morphology depend on height and width of the dune, exposure of wind and the degree and type of vegetation cover. Different morphological forms of blowouts consequently have differences in soil and vegetation characteristics (Hesp, 2002). This blowout is effective against the processes of acidification and eutrophication of the soil, however other
morphological blowout forms may have different influences on soil characteristics and vegetation. Furthermore, this study is only done in a short time period. Long term effects of natural, active blowouts on soil and vegetation characteristics in the grey dunes have not been taken into account.
7. Conclusions
Nitrogen deposition in the lime-poor grey dunes in the Wadden district, causes acidification and eutrophication of the soil. The surface surrounded by an active, natural blowout compared with an equal sized surface with an stable blowout in the lime-poor grey dunes at de Koog show differences in soil and vegetation characteristics. pH in the active blowout area is higher, and is positive correlated to bare sand cover. This indicates for counteraction in soil acidification and indicates for early states of succession which has influence on the
vegetation. A higher number of species and higher mosses cover occur in the active blowout zone, and show enhanced biodiversity by blowout activity. In contrast, the stable zone has a lower pH, a thicker Ah layer and higher SOM, and soil C and N contents which indicate for slower decomposition rates. Changes in vegetation follow, herbs cover and biomass of plants is higher in the stable zone and grass encroachment is present in the stable zone. Based on the results of this study, active blowouts can be effective against soil acidification and grass encroachment, enhance plant biodiversity and slow down accelerated succession. However, the results are only based on two areas and the form of the blowout and the weather
conditions might have had an impact on the results of the study. Conclusions therefore should be interpreted carefully.
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27 Appendix
A. Field survey data summary table
Sample pH EC (mS/cm) BD (g/cm3) SM (%) CaCO3 (%) SOM (%) C soil (g/m2)
A1 6,05 27,6 1,36 0,03 0,41 0,70 0,55 A2 7,35 66,4 1,41 0,00 0,10 0,35 0,29 A3 5,69 71,6 1,05 0,05 0,08 2,10 1,28 A4 5,67 61,1 1,25 0,07 0,16 1,03 0,75 A5 6,29 158,7 1,03 0,06 0,00 1,03 1,82 A6 8,7 48,7 1,57 0,03 0,00 0,00 0,20 A7 8,52 61,9 1,42 0,04 0,00 0,22 0,21 A8 7,38 88 1,30 0,03 0,00 0,25 0,38 A9 6,75 160,4 1,06 0,09 0,17 0,51 1,19 A10 6,95 87,8 1,25 0,02 0,00 1,93 0,56 A11 6,88 37,3 1,29 0,05 0,00 0,77 0,36 A12 5,79 59,5 1,02 0,06 0,00 0,47 1,21 A13 5,56 28,3 1,18 0,05 0,42 2,03 0,67 A14 5,49 79,2 1,00 0,08 0,21 0,97 1,67 A15 6,99 79,3 1,37 0,02 0,77 2,88 0,39 A16 7,33 76,6 1,38 0,02 0,48 0,49 0,23 A17 5,18 108,4 0,92 0,03 0,53 0,28 1,38 A18 6,29 131,4 0,81 0,09 0,00 2,59 1,13 A19 5,15 65,7 1,04 0,10 0,00 2,40 1,30 A20 5,88 39,9 1,22 0,05 0,18 2,14 0,62 S1 5,52 63,1 1,03 0,11 0,00 0,88 0,92 S2 5,1 113,6 0,96 0,08 0,00 1,54 1,57 S3 4,66 93,6 0,83 0,08 0,00 2,81 1,91 S4 5,12 36,6 1,14 0,04 10,65 3,94 0,79 S5 4,58 73,4 0,92 0,08 0,00 1,19 1,30 S6 5,83 43,8 1,33 0,02 0,62 2,43 0,29 S7 5,8 54,4 1,31 0,01 0,00 0,38 0,36 S8 4,35 79,2 0,91 0,07 0,00 0,47 1,79 S9 4,1 46,3 1,13 0,05 0,00 3,39 0,90 S10 4,06 139,1 0,60 0,11 0,00 1,38 2,09 S11 4,89 99,7 0,83 0,06 0,00 5,99 2,37 S12 4,81 109,3 0,63 0,19 0,00 4,92 1,79 S13 5,26 87,1 0,92 0,03 0,00 4,93 1,79 S14 5,52 60,8 1,07 0,04 0,00 3,35 1,20 S15 5,49 103,4 0,90 0,05 0,00 1,93 1,58 S16 5,08 74,2 0,90 0,06 0,00 3,02 1,92 S17 5,09 67,9 0,96 0,08 0,00 3,66 1,56 S18 5,22 79,2 1,04 0,04 0,00 2,80 1,69 S19 6,05 112,3 0,98 0,05 45,72 2,80 1,63 S20 6,13 35,8 1,34 0,01 1,02 2,86 0,56
28
Sample N soil (g/m2) C/N ratio soil Ah layer (cm) Sand layer (cm) Bare sand (%)
A1 0,07 7,77 4 0 5 A2 0,02 12,35 6 0 0 A3 0,11 12,01 5 0 0 A4 0,07 10,62 6 0 10 A5 0,16 11,23 5 0 2 A6 0,00 61,90 0 20 100 A7 0,00 64,44 0 20 60 A8 0,04 9,77 0 11 75 A9 0,10 11,41 0 4 40 A10 0,05 10,91 5 0 5 A11 0,04 8,72 2 0 40 A12 0,10 11,59 4 0 2 A13 0,07 9,58 3 0 0 A14 0,14 12,02 5 0 0 A15 0,01 61,29 0 20 60 A16 0,00 64,71 0 20 70 A17 0,11 12,21 3 0 0 A18 0,09 12,57 8 0 1 A19 0,12 10,96 12 0 0 A20 0,06 9,62 3 0 0 S1 0,08 11,09 7 0 0 S2 0,13 11,90 5 0 0 S3 0,16 11,95 7 0 0 S4 0,09 9,22 2 0 0 S5 0,11 11,55 2 0 5 S6 0,04 6,78 3 0 20 S7 0,05 7,64 4 0 20 S8 0,15 12,31 8 0 5 S9 0,08 11,43 5 0 0 S10 0,16 12,99 13 0 0 S11 0,17 13,99 9 0 0 S12 0,13 14,14 5 0 0 S13 0,14 12,86 13 0 0 S14 0,10 11,68 6 0 0 S15 0,14 11,34 9 0 0 S16 0,14 13,79 7 0 0 S17 0,13 12,41 4 0 2 S18 0,15 11,04 3 0 1 S19 0,14 11,84 3 0 15 S20 0,06 9,67 1 0 25
29 Sample Herbs cover (%) Shrubs cover (%) Mosses cover
(%) Species Mosses species Vascular species
A1 60 0 40 25 9 16 A2 40 3 50 25 8 17 A3 45 5 45 29 7 22 A4 50 2 40 32 7 25 A5 70 10 20 31 5 26 A6 0 0 0 0 0 0 A7 30 2 0 3 0 3 A8 10 10 5 25 2 23 A9 30 20 10 32 9 23 A10 40 10 30 28 7 21 A11 20 20 40 34 7 27 A12 50 10 40 32 8 24 A13 20 10 70 24 9 15 A14 25 25 70 17 3 14 A15 40 10 0 20 0 20 A16 10 20 0 19 1 18 A17 45 1 50 15 5 10 A18 45 4 50 24 4 20 A19 40 4 55 19 5 14 A20 30 4 70 25 6 19 S1 55 5 40 20 3 17 S2 70 1 35 17 3 14 S3 50 3 50 17 3 14 S4 60 20 15 22 5 17 S5 30 20 40 28 5 23 S6 40 13 40 28 8 20 S7 40 8 45 22 4 18 S8 60 10 35 17 4 13 S9 40 10 50 20 6 14 S10 70 10 20 25 6 19 S11 55 20 25 20 5 15 S12 45 15 35 13 3 10 S13 65 15 20 16 3 13 S14 60 2 40 17 4 13 S15 20 5 20 19 2 17 S16 70 6 30 26 4 22 S17 50 3 50 21 5 16 S18 5 55 45 25 5 20 S19 45 5 40 23 3 20 S20 35 15 25 30 5 25
30
Sample C content veg N content veg C/N ratio veg dry weight veg (g)
A1 332,98 7,35 45,29 7,75 A2 141,44 3,41 41,53 3,44 A3 229,02 6,39 35,84 5,09 A4 413,41 8,61 48,04 9,23 A5 203,61 7,17 28,39 4,98 A6 0,00 0,00 0,00 0,00 A7 80,37 3,87 20,75 1,88 A8 174,61 7,65 22,84 4,42 A9 120,61 2,68 45,02 2,85 A10 208,97 6,20 33,71 5,61 A11 115,32 3,41 33,79 3,19 A12 210,07 6,60 31,82 4,89 A13 308,68 7,06 43,73 6,36 A14 815,63 21,85 37,33 17,40 A15 259,03 10,49 24,69 5,72 A16 153,57 6,53 23,50 3,96 A17 153,78 5,45 28,23 3,48 A18 368,44 9,56 38,52 7,84 A19 187,68 5,63 33,31 4,15 A20 312,68 6,44 48,55 6,79 S1 401,05 9,48 42,29 8,71 S2 590,44 16,00 36,90 12,60 S3 163,65 4,70 34,83 3,51 S4 456,19 9,45 48,26 9,99 S5 647,96 15,53 41,73 13,86 S6 119,34 2,53 47,22 2,91 S7 188,10 6,41 29,33 4,57 S8 873,51 25,15 34,73 18,85 S9 457,83 11,60 39,47 9,81 S10 468,85 11,46 40,92 10,03 S11 605,64 14,10 42,96 12,37 S12 647,43 15,01 43,13 12,65 S13 938,55 20,82 45,07 18,93 S14 329,71 9,30 35,46 6,65 S15 384,48 9,64 39,90 8,01 S16 486,51 13,75 35,39 10,43 S17 417,77 7,77 53,75 9,32 S18 308,35 9,77 31,58 6,80 S19 247,94 5,18 47,83 5,21 S20 171,54 5,51 31,15 4,22
31 B. Statistical analysis summary tables
Summary tables: Soil variables
Soil variables Min A Max A Mean A Std A
BD 0,8 1,6 1,2 0,2
EC [S/m] 27,6 160,4 76,9 38,0
pH 5,2 8,7 6,5 1,0
Ah layer 0,0 14,0 4,6 3,0
Sand deposited layer 0,0 20,0 1,5 4,8
Bare sand [%] 0,0 100,0 10,1 19,9 C content [g/m2] 0,2 1,8 0,8 0,5 N content [g/m2] 0,0 0,2 0,1 0,05 C/N ratio 7,8 64,7 21,3 21,5 SOM 0,0 2,9 1,2 0,9 Soil variables Min S Max S Mean S Std S BD 0,6 1,3 1,0 0,2 EC [S/m] 35,8 139,1 78,6 28,5 pH 4,1 6,1 5,1 0,6 Ah layer 0,0 16,0 6,2 3,5
Sand deposited layer 0,0 0,0 0,0 0,0
Bare sand [%] 0,0 75,0 3,5 10,3
C content [g/m2] 0,3 2,4 1,4 0,6
N content [g/m2] 0,0 0,2 0,12 0,0
C/N ratio 6,8 11,5 14,1 1,9
SOM 0,4 6,0 2,7 1,5
Soil variables Highest mean P-value Significant difference
BD A 0,00 Yes
EC [S/m] S 0,87 No
pH A 0,00 Yes
Ah layer S 0,00 Yes
Sand deposited layer A 0,00 Yes
Bare sand [%] A 0,00 Yes
C content [g/m2] S 0,00 Yes
N content [g/m2] S 0,00 Yes
C/N ratio A 0,05 Yes
SOM S 0,00 Yes
Soil variables Min A Max A Mean A Std A
C/N unaffected 7,77 12,35 10,79 1,82
C/N blowout 61,9 64,44 63,17 1,79
32
Soil variables Min S Max S Mean S Std S
C/N unaffected 9,22 11,95 11,95 1,13
C/N blowout 7,64 7,2 6,78 0,61
C/N accumulated 11,43 14,14 12,77 1,05
Soil variables
Highest
mean in P-value Significant difference
C/N unaffected S 0,73 No
C/N blowout A 0,00 Yes
C/N accumulated S 0,00 Yes
Summary tables vegetation variables
Vegetation variables Min A Max A Mean A Std A
Herbs [%] 0 75,0 37,0 16,3
Shrubs [%] 0 70,0 9,6 10,8
Mosses[%] 0 80,0 48,1 19,4
Species amount 0 34,0 23,0 9,1
Number of Vascular plants 0 27,0 17,9 7,2
Number of mosses 0 9,0 5,1 3,1
C content [g/m2] 0 815,6 238,5 169,3
N content [g/m2] 0 21,9 6,8 4,3
C/N ratio 0 32,4 48,0 11,3
Dry weight [g] 0 17,4 5,4515 3,544
Vegetation variables Min S Max S Mean S Std S
Herbs [%] 5,0 75,0 52,9 14,3
Shrubs [%] 1,0 65,0 12,0 11,9
Mosses[%] 5,0 75,0 39,7 14,0
Species amount 13,0 40,0 21,3 4,6
Number of Vascular plants 10,0 25,0 17,0 3,9
Number of mosses 2,0 8,0 4,3 1,4
C content [g/m2] 119,3 938,6 445,2 225,0
N content [g/m2] 2,5 25,2 11,2 5,6
C/N ratio 29,3 41,0 53,8 6,4
Dry weight (g) 2,91 18,93 9,4715 4,5467
Vegetation variables Highest mean P-value Significant difference
Herbs [%] S 4,9E-17 Yes
Shrubs [%] S 7,0E-02 No
Mosses[%] A 2,8E-05 Yes
33
Number of Vascular plants A 6,4E-01 No
Number of mosses A 3,1E-01 No
C content [g/m2] S 2,3E-03 Yes
N content [g/m2] S 9,0E-03 Yes
C/N ratio S 6,0E-03 Yes
Dry weight [g] S 0,0023 Yes
Vegetation variables Min A Max A Mean A Std A
Species unaffected 25 32 28,4 3,29 Species blowout 0 3 1,5 2,12 Species accumulated 17 34 27,43 5,94 Vascular unaffected 16 26 21,2 4,55 Vascular blowout 0 3 1,5 2,12 Vascular accumulated 14 27 21 4,8 Mosses unaffected 5 9 7,2 1,1 Mosses blowout 0 0 0 0 Mosses accumulated 2 9 6,43 2,82
Vegetation variables Min S Max S Mean S Std S
Species unaffected 17 28 20,8 4,55 Species blowout 22 28 25 4,24 Species accumulated 13 25 18,29 3,81 Vascular unaffected 14 23 17 3,67 Vascular blowout 18 20 19 1,41 Vascular accumulated 10 19 13,86 2,73 Mosses unaffected 3 5 3,8 1,1 Mosses blowout 4 8 6 2,82 Mosses accumulated 3 6 4,43 1,27 Vegetation variables Highest
mean P-value Significant difference
Species unaffected A 2E-02 Yes
Species blowout S 2E-02 Yes
Species accumulated A 5E-03 Yes
Vascular unaffected A 1E-01 No
Vascular blowout S 1E-02 Yes
Vascular accumulated A 5E-03 Yes
Mosses unaffected A 3E-03 Yes
Mosses blowout S 1E-01 No
34
Pearson correlation CaCO3 [%] BD [ml/cm3]
EC [mS/um] Soil moisture [%] pH Ah layer [cm] CaCO3 [%] 1,00 BD [ml/cm3] -0,06 1,00 EC [mS/um] 0,11 -0,59 1,00 Soil Moisture [%] -0,0588 -0,73 0,40 1,00 pH 0,017 0,76 -0,11 -0,49 1,00 Ah layer [cm] -0,12 -0,63 0,27 0,37 -0,59 1,00
Sand deposited layer [cm] -0,0675 0,55 -0,06 -0,30 0,72 -0,53
Bare sand [%] -0,0072 0,65 -0,10 -0,36 0,78 -0,64
C content soil material [g/m2] 0,1025 -0,90 0,58 0,56 -0,71 0,62
N content soil [g/m2] 0,1252 -0,88 0,52 0,53 -0,76 0,62 C/N ratio soil -0,0555 0,45 -0,05 -0,24 0,62 -0,41 SOM [%] 0,1412 -0,44 0,02 0,23 -0,47 0,36 Herbs [%] 0,0607 -0,49 0,25 0,26 -0,52 0,56 Shrubs [%] -0,0472 -0,10 0,05 0,01 -0,14 -0,16 Mosses [%] 0,0047 -0,25 -0,25 0,22 -0,49 0,28 Species [counts] 0,0238 -0,03 0,04 -0,08 -0,16 -0,02 Mosses [counts] -0,1032 -0,01 -0,16 -0,01 -0,25 0,09
Vascular plants [counts] 0,0742 -0,03 0,11 -0,09 -0,10 -0,06
C content veg [g/m2] -0,0571 -0,59 0,13 0,41 -0,64 0,52
N content veg [g/m2] -0,116 -0,55 0,17 0,34 -0,58 0,45
C/N ratio veg 0,2209 -0,42 0,01 0,34 -0,58 0,35
Dry weight veg [g] -0,0669 -0,57 0,12 0,38 -0,64 0,50
Pearson correlation Sand deposited layer Bare sand C content soil N content soil
Sand deposited layer [cm] 1,00
Bare sand [%] 0,89 1,00
C content soil material [g/m2] -0,50 -0,60 1,00
N content soil [g/m2] -0,64 -0,69 0,97 1,00 C/N ratio soil 0,95 0,75 -0,39 -0,55 SOM [%] -0,30 -0,40 0,47 0,42 Herbs [%] -0,48 -0,60 0,50 0,50 Shrubs [%] -0,06 -0,01 0,17 0,19 Mosses [%] -0,70 -0,69 0,18 0,30 Species [counts] -0,49 -0,30 -0,02 0,10 Mosses [counts] -0,62 -0,47 -0,03 0,10
Vascular plants [counts] -0,35 -0,17 -0,01 0,08
C content veg [g/m2] -0,38 -0,49 0,60 0,57
N content veg [g/m2] -0,26 -0,40 0,57 0,52
C/N ratio veg -0,70 -0,70 0,32 0,41
35
Pearson correlation C/N ratio soil SOM [%] Herbs [%] Shrubs [%] Mosses [%]
C/N ratio soil 1,00 SOM [%] -0,21 1,00 Herbs [%] -0,37 0,32 1,00 Shrubs [%] -0,08 0,20 -0,36 1,00 Mosses [%] -0,62 0,09 0,09 -0,04 1,00 Species [counts] -0,57 -0,06 0,13 0,24 0,23 Mosses [counts] -0,64 -0,05 0,18 0,07 0,49
Vascular plants [counts] -0,45 -0,05 0,09 0,27 0,08
C content veg [g/m2] -0,29 0,42 0,42 0,20 0,18
N content veg [g/m2] -0,19 0,31 0,37 0,24 0,11
C/N ratio veg -0,65 0,44 0,43 0,03 0,49
Dry weight veg [g] -0,30 0,39 0,43 0,20 0,19
Pearson correlation Species [counts] Mossess [counts] Vascular plants [counts] C content veg [g/m2] N content veg [g/m2] Species [counts] 1,00 Mosses [counts] 0,71 1,00
Vascular plants [counts] 0,95 0,47 1,00
C content veg [g/m2] -0,12 -0,10 -0,11 1,00
N content veg [g/m2] -0,14 -0,21 -0,09 0,96 1,00
C/N ratio veg 0,44 0,54 0,32 0,44 0,25
Dry weight veg [g] -0,08 -0,08 -0,07 1,00 0,96
Pearson correlation C/N ratio Veg
Dry weight veg [g]
C/N ratio veg 1,00
Dry weight veg [g] 0,44 1,00
Significance level Pearson CaCO3 [%] BD [ml/cm3]
EC [mS/um] Soil moisture [%] pH Ah layer [cm] CaCO3 [%] 0 BD [ml/cm3] 0,73 0,00 EC [mS/um] 0,4963 0,00 0,00 Soil Moisture [%] 0,7187 0,00 0,01 0,00 pH 0,917 0,00 0,52 0,00 0,00 Ah layer [cm] 0,4607 0,00 0,10 0,02 0,00 0,00
Sand deposited layer [cm] 0,679 0,00 0,73 0,06 0,00 0,00
Bare sand [%] 0,9646 0,00 0,54 0,02 0,00 0,00
C content soil material [g/m2] 0,5292 0,00 0,00 0,00 0,00 0,00
N content soil [g/m2] 0,4414 0,00 0,00 0,00 0,00 0,00
C/N ratio soil 0,7339 0,00 0,74 0,14 0,00 0,01
SOM [%] 0,3848 0,00 0,89 0,15 0,00 0,02
36
Shrubs [%] 0,7725 0,53 0,77 0,97 0,38 0,33
Mosses [%] 0,9772 0,12 0,12 0,17 0,00 0,09
Species [counts] 0,8842 0,87 0,82 0,63 0,32 0,90
Mosses [counts] 0,5262 0,95 0,33 0,94 0,12 0,57
Vascular plants [counts] 0,6493 0,85 0,49 0,57 0,54 0,69
C content veg [g/m2] 0,7263 0,00 0,44 0,01 0,00 0,00
N content veg [g/m2] 0,4758 0,00 0,30 0,03 0,00 0,00
C/N ratio veg 0,1707 0,01 0,95 0,03 0,00 0,03
Dry weight veg [g] 0,6815 0,00 0,48 0,01 0,00 0,00
Significance level Pearson
Sand deposited layer
[cm] Bare sand [%]
C content soil [g/m2]
N content soil [g/m2]
Sand deposited layer [cm] 0,00
Bare sand [%] 0,00 0,00
C content soil material [g/m2] 0,00 0,00 0,00
N content soil [g/m2] 0,00 0,00 0,00 0,00 C/N ratio soil 0,00 0,00 0,01 0,00 SOM [%] 0,06 0,01 0,00 0,01 Herbs [%] 0,00 0,00 0,00 0,00 Shrubs [%] 0,71 0,94 0,29 0,23 Mosses [%] 0,00 0,00 0,26 0,06 Species [counts] 0,00 0,06 0,92 0,53 Mosses [counts] 0,00 0,00 0,84 0,53
Vascular plants [counts] 0,02 0,28 0,97 0,61
C content veg [g/m2] 0,02 0,00 0,00 0,00
N content veg [g/m2] 0,10 0,01 0,00 0,00
C/N ratio veg 0,00 0,00 0,04 0,01
Dry weight veg [g] 0,02 0,00 0,00 0,00
Significance level Pearson C/N ratio soil SOM [%] Herbs [%] Shrubs [%] Mosses [%]
C/N ratio soil 0,00 SOM [%] 0,20 0,00 Herbs [%] 0,02 0,04 0,00 Shrubs [%] 0,64 0,21 0,02 0,00 Mosses [%] 0,00 0,58 0,59 0,79 0,00 Species [counts] 0,00 0,73 0,42 0,14 0,15 Mosses [counts] 0,00 0,76 0,27 0,67 0,00
Vascular plants [counts] 0,00 0,76 0,59 0,09 0,63
C content veg [g/m2] 0,07 0,01 0,01 0,22 0,25
N content veg [g/m2] 0,24 0,05 0,02 0,14 0,50
C/N ratio veg 0,00 0,00 0,01 0,83 0,00
37
Significance level Pearson Species [counts] Vascular plants [counts] Mosses [counts]
C content veg [g/m2]
Species [counts] 0,00
Mosses [counts] 0,00 0,00
Vascular plants [counts] 0,00 0,00 0,00
C content veg [g/m2] 0,46 0,54 0,51 0,00
N content veg [g/m2] 0,38 0,19 0,58 0,00
C/N ratio veg 0,00 0,00 0,04 0,01
Dry weight veg [g] 0,62 0,63 0,68 0,00
Significance level Pearson
N content veg
[g/m2] C/N ratio Veg
Dry weight veg [g]
N content veg [g/m2] 0,00
C/N ratio veg 0,13 0,00
Dry weight veg [g] 0,00 0,00 0,00
Matlab script of correlation table % Correlatietabel Texel data % clear clc clear close all % load data xlsread Field_survey_data.xlsx; parameters=ans; % parameters pH=parameters(:,1); EC=parameters(:,2); BD=parameters(:,3); SM=parameters(:,4); CaCO3=parameters(:,5); SOM=parameters(:,6); Csoil=parameters(:,7); Nsoil=parameters(:,8); CNsoil=parameters(:,9); Ah=parameters(:,10); Sh=parameters(:,11); Baresand=parameters(:,12); Herbs=parameters(:,13); Shrubs=parameters(:,14); Mosses=parameters(:,15); Species=parameters(:,16); Mossespecies=parameters(:,17); Vascular=parameters(:,18); Cveg=parameters(:,19); Nveg=parameters(:,20); CNveg=parameters(:,21); dryweight=parameters(:,22); % correlations ECBD=corr(EC,BD)
38 SMBD=corr(SM,EC) pHBD=corr(pH,pH) AhBD=corr(Ah,Ah) ShBD=corr(Sh,Sh) BaresandBD=corr(Baresand,Baresand) CsoilBD=corr(Csoil,Csoil) NsoilBD=corr(Nsoil,Nsoil) CNsoilBD=corr(CNsoil,CNsoil) SOMBD=corr(SOM,SOM) HerbsBD=corr(Herbs,Herbs) ShrubsBD=corr(Shrubs,Shrubs) MossesBD=corr(Mosses,Mosses) SpeciesBD=corr(Species,Species) MossespeciesBD=corr(Mossespecies,Mossespecies) VascularBD=corr(Vascular,Vascular) CvegBD=corr(Cveg,Cveg) [NvegBD,p]=corr(Nveg,Nveg) [pearscor,p]=corr([CaCO3,BD,EC,SM,pH,Ah,Sh,Baresand,Csoil,Nsoil,CNsoil,SOM, Herbs,Shrubs,Mosses,Species,Mossespecies,Vascular,Cveg,Nveg,CNveg,dryweight ],[CaCO3,BD,EC,SM,pH,Ah,Sh,Baresand,Csoil,Nsoil,CNsoil,SOM,Herbs,Shrubs,Mos ses,Species,Mossespecies,Vascular,Cveg,Nveg,CNveg,dryweight])
39 C. Auxiliary correlations and graphs
0 10 20 30 40 50
Buckthorn Marram grasses Crowberry
Cou n ts (grid p o in ts )
Indicator species
transect A transect S R² = 0,919 0,00 5,00 10,00 15,00 20,00 25,00 30,00 0,00 200,00 400,00 600,00 800,00 1000,00 N co n ten t (g/ m 2) C content (g/m2)C and N contents vegetation
R² = 0,9404 0,00 0,02 0,04 0,06 0,08 0,10 0,12 0,14 0,16 0,18 0,20 0,0 0,5 1,0 1,5 2,0 2,5 N co n ten t (g/ m 2) C content (g/m2)
Soil C and N correlation
40
Vegetation species transect A transect S
Buckthorn 20 10
Marram grasses 40 43
