Cut cut cut

The post provided by Mareike Roeder

The highest forest fragment of the study is on top of the cliff, Yinshan near Menglun town. The landscape is changing; the left photo is from 2014, when a rubber plantation was established, while the right photo is from 2017, when the cultivation changed to banana and was extended. Photo credit M. Roeder

This post refers to the article Wood density, growth and mortality relationships of lianas on environmental gradients in fragmented forests of montane landscapes by Roeder et al. published in the Journal of Vegetation Science.

This project was a typical low-budget one. I had just finished my postdoc project in Xishuangbanna Tropical Botanical Garden (XTBG), Yunnan, China in 2014 and had a short contract extension but nothing to do. So I decided to survey the liana communities in a forest fragmentation project run by my group. All plots of the forest fragmentation project were conveniently located around the botanical garden. After one and half years, I returned with a new research contract to XTBG, and not having any research funds yet, I decided to re-survey the plots of the forest fragmentation project as an initial project. The idea to include wood density arose from other projects in my research group, which included tree communities and a suite of functional traits to explain the change in community patterns due to disturbance, and also during my daily cycling to work when I saw many easy accessible lianas on the road side.

Subplots were marked by the white-red stick in the centre and could be very different: left side is an open, rocky lime stone subplot, right side is a tropical rain forest subplot. Photo credit M. Roeder

As a lucky coincidence, the country roads around Menglun town were renewed in 2016, and many trees were felled. That provided easy access to many nice liana wood density samples and leaf samples for identification. My assistant and I harvested in total over 400 stems and over 140 (morpho-) species in the surroundings of the institute, and I had a foldable saw in my backpack for many months ready to cut stems or branches of missing species during cycling tours in the surroundings. Prof. Cao Kung Fan and Prof. Ferry Slik were both very supportive of my idea of collecting liana wood density data, even though it was clear from the beginning that for most liana species I could collect this destructive trait only from one or few individuals. Wood density is a functional trait related to life history and regularly used in the analysis of tree communities, but hardly ever for lianas. The range of wood density in lianas is obviously large, from very light soft flexible stems with large vessels up to dense tough stems that can be confused with trees at first sight. In this study we examine how mortality, relative growth rate and wood density are related in liana species and how liana communities respond to environmental gradients and forest fragmentation in terms of abundance, diversity, size structure, mortality, relative growth rate and wood density.

Billy (Yang Zongze) cutting a liana at the forest edge of an evergreen broad leaved forest. Photo credit M. Roeder

All in all, the data resulted in a nice publication but I think the most useful (or of additional further use) is the data set of wood density, which is provided as the paper supplement. Hundreds of bags with stem samples are still remaining in the lab, including a leaf voucher for each individual, and I hope this collection can be reused for other purposes.

Of course, there is also a certain beauty to the wood sections themselves!

Stem sections of (left to right and top to bottom) Acacia pennata, Rourea minor, Amalocalyx microlobus, Tetrastigma 2, Desmos chinensis, Tinospora cf. crispa, Urceola rosea, Salacia cochinchinensis. Photo credit: Mareike Roeder

About the author: Mareike Roeder was researcher at Xishuangbanna Botanical Garden, Chinese Academy of Sciences, Menglun, Yunnan, China. Now she works as a project coordinator at Karlsruher Institut für Technologie in Germany and hobby scientist. Main research interest is general vegetation ecology, including phylogenetic patterns, common garden experiments and plant functional traits.