Might be worth looking at http://www.kastorfer-geschichte.de/resources/H$C3$B6fefolgen+Sierksrade.pdfhttp://www.kastorfer-geschichte.de/resources/H$C3$B6fefolgen+Sierksrade.pdf as that (German language)website has considerable genealogical (BDM)which appears to have been compiled from Church records in the Sierksrade area of Schleswig Holstein, including various EHLERS entries dating from about 1699 - 1800.
As I do not speak or read German, and the website uses many abbreviations, & German genealogical symbols (eg oo which indicates a marriage; and + indicates a death) I am guessing at much that is shown. Someone familiar with German language & German genealogical shorthand should be able to translate/explain the entries.
Included are Jochen EHLERS (1715)- 1757 & wife Anna Maria (nee DOHRENDORF) whose son Hans Jurgen EHLERS born (?)1723 died 1759, was married to Anna Maria KOP(?) Although the listed offspring (k = kinder)do not include your Jurgen Friedrich EHLERS, there still might be some connection.
I came across this website by googling SPIERING + BARNITZ and if you look closely, you will find a couple of my own ancestors listed: Anna Maria EHLERS (1749-1803,daughter of Jochen EHLERS, in 1772 married Matthias SPIERING (1748 - 1818)
Marvelous what computers sometimes find! Good hunting! regards, Peter.