Gradient Analyses
Gradient analyses were completed with the ecodist and vegan packages in R software.
Direct Gradient Analysis:
From the Direct Gradient Analysis, it appears that total terpene concentration and total diterpene concentration are highly associated with basal area increment, ring width, resin duct size and average resin duct area.
Relative resin duct area and resin duct density do not appear to be highly associated with the chemical concentrations.
From the Direct Gradient Analysis, it appears that total terpene concentration and total diterpene concentration are highly associated with basal area increment, ring width, resin duct size and average resin duct area.
Relative resin duct area and resin duct density do not appear to be highly associated with the chemical concentrations.
Indirect Gradient Analysis:
From the Indirect Gradient Analysis, it appears that there is some sort of miss in this analysis. Relative resin duct area and resin duct density appear to be highly correlated. Resin duct size, resin duct production, total resin duct area, ring width, total monoterpene concentrations, total diterpene concentrations and resin duct size appear to be highly correlated.
From the Indirect Gradient Analysis, it appears that there is some sort of miss in this analysis. Relative resin duct area and resin duct density appear to be highly correlated. Resin duct size, resin duct production, total resin duct area, ring width, total monoterpene concentrations, total diterpene concentrations and resin duct size appear to be highly correlated.
Direct Gradient Analysis with PCA:
The Direct Gradient Analysis with PCA is very similar to the Direct Gradient Analysis. Total terpene concentration and total diterpene concentration appear to be highly associated with basal area increment, ring width, resin duct size and average resin duct area.
Relative resin duct area and resin duct density do not appear to be highly associated with the chemical concentrations.
The Direct Gradient Analysis with PCA is very similar to the Direct Gradient Analysis. Total terpene concentration and total diterpene concentration appear to be highly associated with basal area increment, ring width, resin duct size and average resin duct area.
Relative resin duct area and resin duct density do not appear to be highly associated with the chemical concentrations.
Indirect Gradient Analysis with PCA:
For this analysis, total chemical concentrations appear to be associated with resin duct production, basal area increment, total resin duct area and ring width and negatively associated with resin duct density and relative resin duct area.
For this analysis, total chemical concentrations appear to be associated with resin duct production, basal area increment, total resin duct area and ring width and negatively associated with resin duct density and relative resin duct area.
Constrained Gradient Analysis with Canonical correlation analysis (CANCOR)
Table 1. Results from Constrained Gradient Analysis with CANCOR.
From CAN1, total monoterpenes, total diterpenes and total terpenes are highly associated with ring width and basal area increment. The terpene concentrations are also somewhat associated with total resin duct area and resin duct production.
From CAN2, total non-structural carbohydrate concentrations are somewhat associated with relative resin duct area.
IS THERE A RELATIONSHIP BETWEEN RESIN DUCT CHARACTERISTICS AND RESIN-BASED CHEMICAL CHARACTERISTICS?
I hypothesized that due to the growth-differentiation hypothesis in which plants face a trade-off between allocating resources to growth or to chemical or morphological changes, plants will invest similarly to chemical and morphological defences while investing fewer resources to growth.
Terpenes and Non-structural Carbohydrates
Univariate analyses indicated that total monoterpenes and total diterpenes were highly correlated (Figure 28; r = 0.84, p-value < 0.001). Terpenes and non-structural carbohydrates did not appear to be significantly correlated from the univariate analyses, but were highly associated in the gradient analyses. From the Constrained Gradient Analysis with CANCOR, total monoterpenes, total diterpenes and total terpenes were highly correlated.
Total Terpenes and Resin Duct Characteristics
Univariate analyses of total terpene concentrations and resin duct characteristics (Figures 28-45) demonstrated significantly correlated relationships. Total terpenes and resin duct production (r = 0.28, p-value < 0.001), total terpenes and total resin duct area (r = 0.35, p-value < 0.001) as well as total terpenes and resin duct size (0.12, p-value = < 0.001) appeared to be positively correlated . Total terpenes and relative resin duct area (r = -0.22, p-value < 0.001) as well as total terpenes and resin duct density (r = -0.32, p-value < 0.001) appeared to be negatively correlated. From the Direct Gradient Analyses, total terpenes appeared to be mostly associated to resin duct size. From the Constrained Gradient Analysis with CANCOR, total terpenes were somewhat correlated with total resin duct area and resin duct production.
Total Terpenes and Radial Growth
Interestingly, exploratory univariate analyses (Figures 28-45) indicated that terpenes were associated with resin duct characteristics and in particular, total terpenes were positively correlated with radial growth through ring width (r = 0.56, p-value < 0.001) and basal area increment ( r = 0.58, p-value < 0.001). From the gradient analyses, basal area increment and ring width appear to be highly associated with total terpene concentrations. From the Constrained Gradient Analysis with CANCOR, total terpenes were highly associated with ring width and basal area increment.
Non-structural Carbohydrates and Resin Duct Characteristics
Univariate analyses for total non-structural carbohydrates and resin duct characteristics (Figures 28-45) only revealed two significant correlations: total non-structural carbohydrate and total resin duct area (r = 0.13, p-value < 0.001) as well as total non-structural carbohydrate and resin duct size (r = 0.14, p-value < 0.001). These associations were also demonstrated in the Direct Gradient Analyses. From the Constrained Gradient Analysis with CANCOR, non-structural carbohydrates were somewhat correlated with relative resin duct area and resin duct density.
Non-structural Carbohydrates and Radial Growth
Univariate analyses for total non-structural carbohydrates and radial growth characteristics (Figures 28-45) demonstrated a positively correlated relationship: non-structural carbohydrates and ring width (r = 0.18, p-value < 0.001) and non-structural carbohydrates and basal area increment (r = 0.11, p-value < 0.001). This was supported by the gradient analyses which demonstrated a slight correlation. From the Constrained Gradient Analysis with CANCOR, non-structural carbohydrates did not demonstrate much correlation with radial growth characteristics.
Terpenes and Non-structural Carbohydrates
Univariate analyses indicated that total monoterpenes and total diterpenes were highly correlated (Figure 28; r = 0.84, p-value < 0.001). Terpenes and non-structural carbohydrates did not appear to be significantly correlated from the univariate analyses, but were highly associated in the gradient analyses. From the Constrained Gradient Analysis with CANCOR, total monoterpenes, total diterpenes and total terpenes were highly correlated.
Total Terpenes and Resin Duct Characteristics
Univariate analyses of total terpene concentrations and resin duct characteristics (Figures 28-45) demonstrated significantly correlated relationships. Total terpenes and resin duct production (r = 0.28, p-value < 0.001), total terpenes and total resin duct area (r = 0.35, p-value < 0.001) as well as total terpenes and resin duct size (0.12, p-value = < 0.001) appeared to be positively correlated . Total terpenes and relative resin duct area (r = -0.22, p-value < 0.001) as well as total terpenes and resin duct density (r = -0.32, p-value < 0.001) appeared to be negatively correlated. From the Direct Gradient Analyses, total terpenes appeared to be mostly associated to resin duct size. From the Constrained Gradient Analysis with CANCOR, total terpenes were somewhat correlated with total resin duct area and resin duct production.
Total Terpenes and Radial Growth
Interestingly, exploratory univariate analyses (Figures 28-45) indicated that terpenes were associated with resin duct characteristics and in particular, total terpenes were positively correlated with radial growth through ring width (r = 0.56, p-value < 0.001) and basal area increment ( r = 0.58, p-value < 0.001). From the gradient analyses, basal area increment and ring width appear to be highly associated with total terpene concentrations. From the Constrained Gradient Analysis with CANCOR, total terpenes were highly associated with ring width and basal area increment.
Non-structural Carbohydrates and Resin Duct Characteristics
Univariate analyses for total non-structural carbohydrates and resin duct characteristics (Figures 28-45) only revealed two significant correlations: total non-structural carbohydrate and total resin duct area (r = 0.13, p-value < 0.001) as well as total non-structural carbohydrate and resin duct size (r = 0.14, p-value < 0.001). These associations were also demonstrated in the Direct Gradient Analyses. From the Constrained Gradient Analysis with CANCOR, non-structural carbohydrates were somewhat correlated with relative resin duct area and resin duct density.
Non-structural Carbohydrates and Radial Growth
Univariate analyses for total non-structural carbohydrates and radial growth characteristics (Figures 28-45) demonstrated a positively correlated relationship: non-structural carbohydrates and ring width (r = 0.18, p-value < 0.001) and non-structural carbohydrates and basal area increment (r = 0.11, p-value < 0.001). This was supported by the gradient analyses which demonstrated a slight correlation. From the Constrained Gradient Analysis with CANCOR, non-structural carbohydrates did not demonstrate much correlation with radial growth characteristics.
In Summary |
I hypothesized that due to the growth-differentiation hypothesis in which plants face a trade-off between allocating resources to growth or to chemical or morphological changes, plants will invest similarly to chemical and morphological defences while investing fewer resources to growth.
I expected there to be a positive relationship between monoterpenes and resin duct characteristics as well as between diterpenes and resin duct characteristics as trees with enough resources should be able to allocate these to both anatomical and chemical defences. From the Canonical Correlation Analysis, I found that total resin duct area and resin duct production were somewhat correlated with terpene concentrations. This indicates that these trees allocate resources to both the production of chemical and anatomical defence characteristics.
I expected that there is an inverse relationship between the concentration and composition of non-structural carbohydrates and the production of resin ducts as previous research has demonstrated that non-structural carbohydrates support the production of resin ducts (Roth et al. 2018). From the Canonical Correlation Analysis, I found that non-structural carbohydrates were only slightly correlated to resin duct production and were somewhat correlated to relative resin duct area and resin duct density.
I expected that there will be a negative relationship between the concentration of chemical defences and radial growth due to the growth-differentiation hypothesis. Interestingly, the Canonical Correlation Analysis demonstrated that terpenes were highly correlated to radial growth and basal area increment. These findings are contrary to the growth-differentiation hypothesis and indicate that these trees may have enough resources or perhaps do not face a trade-off and that they are able to allocate resources to produce defence characteristics as well as to radial growth. More research is needed to determine if this relationship changes with time, especially as climate change contributes to a warmer and drier climate in these areas.
I expected there to be a positive relationship between monoterpenes and resin duct characteristics as well as between diterpenes and resin duct characteristics as trees with enough resources should be able to allocate these to both anatomical and chemical defences. From the Canonical Correlation Analysis, I found that total resin duct area and resin duct production were somewhat correlated with terpene concentrations. This indicates that these trees allocate resources to both the production of chemical and anatomical defence characteristics.
I expected that there is an inverse relationship between the concentration and composition of non-structural carbohydrates and the production of resin ducts as previous research has demonstrated that non-structural carbohydrates support the production of resin ducts (Roth et al. 2018). From the Canonical Correlation Analysis, I found that non-structural carbohydrates were only slightly correlated to resin duct production and were somewhat correlated to relative resin duct area and resin duct density.
I expected that there will be a negative relationship between the concentration of chemical defences and radial growth due to the growth-differentiation hypothesis. Interestingly, the Canonical Correlation Analysis demonstrated that terpenes were highly correlated to radial growth and basal area increment. These findings are contrary to the growth-differentiation hypothesis and indicate that these trees may have enough resources or perhaps do not face a trade-off and that they are able to allocate resources to produce defence characteristics as well as to radial growth. More research is needed to determine if this relationship changes with time, especially as climate change contributes to a warmer and drier climate in these areas.