Please have a look at these links and PDF attachments.

http://link.springer.com/chapter/10.1007%2F978-94-010-0423-7_30

http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=959832

http://www.mycologia.org/content/100/2/191.full

http://link.springer.com/article/10.1007/BF00345684

https://www.researchgate.net/publication/248412852_The_vertical_gradient_of_bark_pH_and_epiphytic_macrolichen_biota_in_relation_to_alkaline_air_pollution

Good Luck

Article The vertical gradient of bark pH and epiphytic macrolichen b...

Dear Ghimire,

Very new perspective of bark, Hope to read more on it

Thank you so much Suresh Ramanan sir  and Arvind sir