Scarlett Arana
a few slips: 9/10
March 31, 2011
GEO 4300
ENVIRONMENTAL BIOGEOGRAPHY
Literature Summary #5
1) The full citation reference for the study
Paquette, A. and Messier, C. (2011), The effect of biodiversity on tree productivity:
from temperate to boreal forests. Global Ecology and Biogeography, 20: 170–180.
Alain Paquette is works for Center for Forest Research from the University of
Québec at Montréal, and Messier is from Center for Forest Research in Montréal, QC
Canada.
2) The research problem or question (1 or 2 sentences)
Is tree productivity positively related to diversity? Does the effect of diversity increase
in less productive forests? What metric of diversity better relates to tree productivity?
3) The general background knowledge leading up to this study (2 sentences)
Growing interests in evaluating the role of biodiversity in order to promote
ecosystem function, services, resilience, biodiversity ecosystem in order to {do what
with?} complementarily of the effects and to select of particular function traits such
as sampling effect. This lead to experimental work has led to the proposal of
mechanisms such as niche complimentarily {complimentarity?}, however, few
attempts have been made to confirm these in natural systems, especially in forests.
4) The methods used by the investigators (1 or 2 sentences)
Investigators studied over 12,000 permanent forest plots in order to plot and study
the regressions used to identify the best explanatory variables for tree productivity.
Climatic, environmental, density and biodiversity variables were studied in a
structural equation model in order to links paths between variables and making
structural equation modeling in order to explore causal networks.
5) The results of the study (2 sentences and one figure or table)
The result of the study demonstrated differences between the two forest biomes
investigated. The effects of biodiversity on productivity may therefore be less
important in temperate forests growing on rich deep soils under more favorable
climates where competitive exclusion is the most probable outcome of species
interactions concluding that complementarily effects are more important to
ecosystem processes in harsh climates, whereas competitive exclusions tend to
favorable few dominant, highly productive species in more productive conditions.
(see table below)
6) What are the weaknesses of the study
The study indicated that data used for the study were limited to traits such as leaf
economics, reproductive and morphological descriptors and not enough data on
belowground traits could not be found. Research however does raise questions on
natural forest ecosystems and adds understanding of the nature of plant
relationships and where competitive exclusions are most likely to occur under
more/less favorable habitats condition.
7) What we learned new from the study (2 sentences)
The main objective of the paper is to inform the reader of effect of biodiversity on
tree productivity focusing on temperate to boreal forests and to investigate the
nature of the relationship between biodiversity and ecosystem functioning over a
large forest extent in North-Eastern North America. I learn that there is a significant
effect of biodiversity on tree productivity due to climatic and environmental
conditions.
Figure 2. Results of the multisample structural equation
modelling (SEM) analysis for (a) temperate and (b)
boreal forest biomes. Single arrows represent causal
paths (error paths are not presented for clarity). Printed
standardized coefficients are significant (P < 0.05; robust
statistics). Arrow thickness is proportional to path
coefficient (solid, positive; dashed, negative; grey, not
significant). All coefficients were significantly different
between biomes but only those that contributed the most
in chi-square increments are shown by asterisks. The
amount of variance explained for each dependent
variable in the model is shown inside their respective box.
The model's robust comparative fit indices (CFI) were
0.933 and 0.987, respectively, for the temperate and
boreal biomes. Climate = mean temperature;
environment = organic layer depth. (c) Alternate SEM
analysis for the temperate biome allowing for asymptotic
productivity and species richness responses to stand
density through the addition of a quadratic factor (BA2=
basal area squared). The model's robust CFI was 0.983.