Creating blowouts:why we do it?

Camiel Aggenbach 1

Features of coastal dunes

• young landscapes and soils

• eolean activity->

re-juvilination and

succession

• strong variation space and time

• nutrient poor

Grey Dunes in EU

too less activationis a problem

too much activationis a problem

atmosphericS+N-deposition

> critical N load Grey Dunes

exceedance inprovince Noord-Holland (NL)

Treats for Grey dunes in atlantic region• eolean dynamics

– large-scale dynamics stopped– partly: less small-scale dynamics

• nitrogen and acidifying deposition– N deposition too high– accelerated decalcification and acidification

• management/ grazing– (decline of live stock grazing)– decline of rabbit population

• Grey Dunes– encroachment of tall grasses– encroachment of shrubs and trees– decalcified dunes became homogeneous

Question: is small-scale eolean activity a cure for deteriorated Grey dunes?

Framework for potential effects

deflationzone

not affected strong sanddeposition

weak sanddeposition

prevailing wind

Framework for potential effects

deflationzone

not affected strong sanddeposition

weak sanddeposition

prevailing wind

during eolean activity:re-vitalising old soil

Framework for potential effects

deflationzone

not affected strong sanddeposition

weak sanddeposition

prevailing wind

after stabilization:succession soil+vegetation

Patterns in and around activeblowouts

> 35 y eolean activity

research in Luchterduinen, The Netherlands (Fujita et al. 2015)

Gradient soil moderately CaCO3 richblowout

Vegetation gradient CaCO3 rich blowout

ecological plant species groups

Grey Dunes: nutrient poor and base rich

pioneer: nutrient poor and base rich

Grey Dunes: nutrient poor and base poor

shrub and forest

deflation zone

Spatial effects permanent blowouts

effect of size and CaCO3 content of deflation zone

research stabilized blowoutsLuchterduinen and Meijendel , The Netherlands(Fujita & Aggenbach, in prep.)

> 35 j eolisch actief

6-14 y stabilized; CaCO3 = 2.7 %

6-14 y stabilized CaCO3 = 2.2 % ca. 25 y stabilized; CaCO3 = 1.2 %

14-25 y stabilized; CaCO3 = 1.0 %

soil pH at 2.5 cm below soil surface

6-14 j gestabiliseerd; CaCO3 = 2.7 %

6-14 j gestabiliseerd; CaCO3 = 2.2 % ca. 25 j gestabiliseerd; CaCO3 = 1.2 %

14-25 j gestabiliseerd; CaCO3 = 1.0 %

Effect of stabilisation

0 1-6 11-226-11 22-33 33-44 54-74 >74 y

0

10

20

30

Chrono-sequence soil

• soildevelopment

-> 40-60 jaar

• effect on content CaCO3– more SOM acc in

calcareous soil

Soil development and plant species richness

• SOM accumulation– more species

• calcarious soil– stays high

– Grey Dunes

> 60 y

• non-calcarious– drops after 40 y due

to acidification

plots van 1 m2

Conclusions

• we need eolean dynamics + stabilization!– species rich Grey Dunes = old soil!– time scale >2-6 decennia– eolean activity: positive effect on base chemistry

topsoil and vegetation

• small scale eolean activity– spatial effect: several 10th of m (6-10 x deflation zone)

• size deflation zone• CaCO3 deflation zone• amount of sand transport

– temporal effect: several decennia after stabilization– effect on short+mid time: re-vitalise old soils

Questions

Is small scale eolean activity a cure for deteriorated Grey dunes?Do we understand the process of small scale eoleanactivity enough to make them?When are blowouts successful?Stabilization of blowouts: failure or success?In which dune zones to create blowouts?Which size and density of blowouts?Which time scale for ‘planning’ blowouts?How to create blowouts?What are the clues to create successful blowouts?