@@ -22,12 +22,12 @@ more likely to coexist locally than similar species
@macarthur_limiting_1967). One way to quantify ecological similarity
between species is via traits, such as leaf, seed and wood
characteristics [@westoby_plant_2002]. Traits influence many aspects
of plant performance, including resource acquisition. Under the *competition-niche similarity hypothesis* higher trait dissimilarity should results in higher resource partitioning at
of plant performance, including resource acquisition. Under the *competition-niche similarity hypothesis* higher trait dissimilarity should results in higher resources partitioning at
local scale and less intense competition. This idea underlies numerous ecological analyses
[@kraft_functional_2008; @cornwell_community_2009]. However this
assumption has rarely been tested against field or experimental
outcomes. This is surprising because it is well known that competitive
interactions among vascular plants are more complex. For instance,
outcomes (but see @uriarte_trait_2010). This is surprising because it is well known that competitive
interactions among vascular plants are more complex than simple resources partitioning. For instance,
most plant species compete for the same limiting resources (water,
light and nutrients), which makes simple local resources partitioning
unlikely. The ranking of competitive ability for these common
...
...
@@ -36,11 +36,10 @@ interaction. If ranking processes are dominant, competitive outcomes
should be more closely related to the hierarchy (or the hierarchical
distance) of relevant functional traits
[@mayfield_opposing_2010; @kunstler_competitive_2012] than trait
dissimilarity. Recent analysis of competitive interactions at local
scale between individual trees (using growth analysis with local
competition index) in mountain forests in the French Alps
[@kunstler_competitive_2012], support this view that competition is
more related to trait hierarchy than trait similarity.
dissimilarity. A recent analysis [@uriarte_trait_2010] of competitive interactions at local
scale between individual trees (using growth adn survival with local
competition index) have shown that it was possible to test the link between competition and traits with simple competition index. Following this approach Kunstler et al. [@kunstler_competitive_2012] have applied this method in mountain forests in the French Alps and shown that competition is
more related to trait hierarchy than trait similarity for tree growth in this system.
# Objective
Given the importance in the ecological literature of the idea that
- $G_{f,p,i,t}$ is the growth (diameter or basal area growth) of
an individual $i$ from species $f$ growing in plot plot $p$ in census $t$,
an individual $i$ from species $f$ growing in plot $p$ in census $t$,
- $D_i$ is the diameter of the individual $i$,
- $B_{n}$ is the the basal area of neighborhood tree of species $n$,
- $B_{n}$ is the the basal area of neighborhood trees of species $n$,
- $G\textrm{max}_{f,p,i}$ is the maximum growth rate of the focal species $f$ on the plot $p$ for the individual $i$,
- $s$ and $g$ are functions representing the size and the competition effect respectively, and
- $\lambda_{n,f}$ is a parameter representing the growth reduction for a
unit of neighborhood basal area increase of species $n$ on species
$f$.
$f$,
- $N_p$ is the number of species on plot $p$.
...
...
@@ -97,7 +97,7 @@ The central part of the analysis involves comparing alternative models for $\lam
\lambda_{n,f} = a +b \times (t_{n} - t_{f}).
\end{equation}
The logic behind the hierarchical trait distance model, can be understand through a decomposition of competition in competitive effect and competitive response. The hierarchical trait distance model occurs when the traits conferring a high competitive effect also confer a high competition tolerance[^compreponse]. During the first day of the workshop we discussed the possibility of including a model with separate
The logic behind the hierarchical trait distance model, can be understood through a decomposition of competition in competitive effect and competitive response. The hierarchical trait distance model occurs when the traits conferring a high competitive effect also confer a high competition tolerance[^compreponse]. During the first day of the workshop we discussed the possibility of including a model with separate
links of traits with competitive effect and competitive response. This
model is connected to several papers by Goldberg *et al.*, where
competition is framed in term of effect and response and their links to
...
...
@@ -135,16 +135,16 @@ functions for competitive response and effect respectively. A series of models w
3. $\lambda$ is influenced by traits of the neighborhood and
focal species (effect-response model):
\begin{equation} \label{response_effect_trait}
\begin{equation} \label{RE}
\lambda_{n,f} = a +b \times t_{f} +c \times t_{n}.
\end{equation}
The trait hierarchical distance model eq. \ref{hier_dist_trait} is a
sub-case of the effect and response model
eq. \ref{response_effect_trait} where $b=-c$.
eq. \ref{RE} \ref{hier_dist_trait} where $b=-c$.
During the workshop David Coomes described how to express the model as a function of the community weighted mean of the trait of the neighborhood trees. For the
most complex model eq. \ref{response_effect_trait} this gives:
most complex model eq. \ref{RE} TODO SOLVE ISSUE WITH EQUATION REF this gives:
\begin{equation}
\sum_{n=1}^{N_p} \lambda_{n,f} \times B_n = \sum_{n=1}^{N_p} (a +b \times t_{f}
...
...
@@ -160,7 +160,7 @@ relative basal area abundance of species $n$, $B_n/B_\textrm{tot}$).
Subsequent to the workshop, and in the material I presented at Ecotas13[^ecotas], I decided to
compare the absolute trait distance model eq. \ref{abs_dist_trait} and the
effect-response model eq. \ref{response_effect_trait}.
effect-response model eq. \ref{RE}.
[^ecotas]:Joint conference of the Ecological Society of Australia and the New Zealand Ecological Society, Nov 2013.
...
...
@@ -237,7 +237,7 @@ table \ref{table-perc} gives the percentage of the data for which at
least 90% of neighborhood is covered with species or genus level
trait. Paracou and M'Baiki are the only two sites with very low
coverage (this because of missing traits but also because of missing
taxonomic identification).
taxonomic identification). TODO NEED TO CHECK WITH GHISLAIN NEW SPECIES LIST.
## Fitting of a mixed linear model
...
...
@@ -336,11 +336,55 @@ Most of the effect-response models fitted show a competitive effect (negative va
- Explore if the decrease in the link between trait and competition at high MAP is related in a change in the packing of trait space in this communities.
- Explore the possibility that trait effect may be different for evergreen/deciduous species (leaf traits) or angiosperm/conifer species (wood density). This could be done by fitting different parameters for the trait of evergreen deciduous and conifer in the effect-response model. This is not really possible for the absolute distance model.
- Use an alternative way of dividing the NFI data than the ecoregion (class of MAP and MAT?).
- Try to run a global analysis with all data (memory limit issue to solve).
- Try to run a global analysis with all data (memory limit issue to solve). and run with global standarization.
<!-- - build plots based on residual to look at the traits effects on -->
<!-- competition. -->
\newpage
# Comments received
@ **Nathan Swenson**: . It appears you are assessing growth/performance using diameter changes. This approach is very flawed from my perspective as it isn't a great metric of actual biomass/growth. Of course it is approximate, but the amount of biomass
