Scale-dependent relationships between tree species richness and ecosystem function in forests
The official blog of the
journal named the paper Editor’s Choice for the edition.
This is a high profile
acknowledgment considering that the CTFS-ForestGEO network was mentioned by name
for being the leader in global forest plots. Plots stretch from Latin America
and Africa to the Czech Republic and Malaysia. This paper did not focus on any
one site, but on different sites around the world that are similar in size.
Authors of the article include: Ryan
A. Chisholm, Helene C. Muller-Landau, Kassim Abdul Rahman, Daniel P. Bebber,
Yue Bin, Stephanie A. Bohlman, Norman A. Bourg, Joshua Brinks, Sarayudh
Bunyavejchewin, Nathalie Butt, Honglin Cao, Min Cao, Dairon C_ardenas, Li-Wan
Chang, Jyh-Min Chiang, George Chuyong, Richard Condit, Handanakere S.
Dattaraja, Stuart Davies, Alvaro Duque, Christine Fletcher, Nimal Gunatilleke,
Savitri Gunatilleke, Zhanqing Hao, Rhett D. Harrison, Robert Howe, Chang-Fu
Hsieh, Stephen P. Hubbell, Akira Itoh, David Kenfack, Somboon Kiratiprayoon,
Andrew J. Larson, Juyu Lian, Dunmei Lin, Haifeng Liu, James A. Lutz, Keping Ma,
Yadvinder Malhi, Sean McMahon, William McShea, Madhava Meegaskumbura, Salim
Mohd. Razman, Michael D. Morecroft, Christopher J. Nytch, Alexandre Oliveira,
Geoffrey G. Parker, Sandeep Pulla, Ruwan Punchi-Manage, Hugo Romero- Saltos,
Weiguo Sang, Jon Schurman, Sheng-Hsin Su, Raman Sukumar, I-Fang Sun, Hebbalalu
S. Suresh, Sylvester Tan, Duncan Thomas, Sean Thomas, Jill Thompson, Renato
Valencia, Amy Wolf, Sandra Yap, Wanhui Ye, Zuoqiang Yuan and Jess K. Zimmerman
Summary
1. The relationship between
species richness and ecosystem function, as measured by productivity or
biomass, is of long-standing theoretical and practical interest in ecology. This
is especially true for forests, which represent a majority of global biomass,
productivity and biodiversity.
2. Here, we conduct an
analysis of relationships between tree species richness, biomass and
productivity in 25forest plots of area 8–50 ha from across the world. The data
were collected using standardized protocols, obviating the need to correct for
methodological differences that plague many studies on this topic.
3. We found that at very small spatial grains (0.04 ha) species richness was generally positively related to productivity and biomass within plots, with a doubling of species richness corresponding to an average 48% increase in productivity and 53% increase in biomass. At larger spatial grains (0.25 ha, 1 ha), results were mixed, with negative relationships becoming more common. The results were qualitatively similar but much weaker when we controlled for stem density: at the 0.04 ha spatial grain, a doubling of species richness corresponded to a 5% increase in productivity and 7% increase in biomass. Productivity and biomass were themselves almost always positively related at all spatial grains.
4. Synthesis. This is the
first cross-site study of the effect of tree species richness on forest biomass
and productivity that systematically varies spatial grain within a controlled
methodology. The scale-dependent results are consistent with theoretical models
in which sampling effects and niche complementarity dominate at small scales,
while environmental gradients drive patterns at large scales. Our study shows
that the relationship of tree species richness with biomass and productivity
changes qualitatively when moving from scales typical of forest surveys (0.04
ha) to slightly larger scales (0.25 and 1 ha). This needs to be recognized in
forest conservation policy and management.