Ecological Archives E096-047-A4

Katie E. Marshall and Jennifer L. Baltzer. 2015. Decreased competitive interaction drive a reverse species richness latitudinal gradient in subarctic forests. Ecology 96:461470. http://dx.doi.org/10.1890/14-0717.1

Appendix D. Tables showing most significant principal components of principal components analyses of climate data, with figure showing change in climate parameters over the past 60 years.

Table D1. Loadings of the first two principal components of a principle components analysis of long-term climate data for the Taiga Plains ecoregion (n = 125). Loadings with absolute value of > 0.3 are bolded.

Variable

PC1 (Temperature)

PC2 (seasonality)

Temperature seasonality (coefficient of variation of monthly mean temperature)

-0.227

-0.445

Maximum warmest (maximum of monthly mean temperatures)

0.348

-0.21

Temperature annual range (difference between maximum of warmest period and minimum of coldest period)

0.068

-0.552

Mean temperature of wettest quarter

0.290

0.150

Mean temperature of driest quarter

0.273

-0.128

Mean temperature of warmest quarter

0.351

-0.185

Precipitation of driest month

0.202

0.401

Precipitation seasonality (coefficient of variation of monthly mean precipitation)

0.264

0.210

Precipitation of driest quarter

0.235

0.238

Precipitation of coldest quarter

0.242

0.086

End of growing season (Julian day when minimum temperature < -2 °C)

0.284

0.046

Mean temperature of growing season

0.344

-0.230

Temperature range of growing season

0.343

-0.233

 

 

 

Proportion of variance explained

54.99%

20.26%

 

Table D2. Loadings of the first three principle components of a principal components analysis of climate-related variables from the year immediately prior to vegetation sampling in Taiga Plains ecoregion Permanent Sample Plots. Loadings with absolute value > 0.3 are bolded.

 

PC1 (temperature)

PC2 (seasonality)

PC3 (Winter precipitation, growing season length)

Mean diurnal range (mean of monthly diurnal ranges)

0.268

-0.099

-0.183

Isothermality (mean diurnal range divided by annual temperature range)

0.246

0.173

-0.207

Temperature seasonality (coefficient of variation of monthly mean temperature)

-0.166

-0.394

0.112

Maximum warmest (maximum of monthly maximum temperatures)

0.244

-0.293

0.060

Minimum coldest (minimum of monthly minimum temperatures)

0.173

0.368

0.062

Temperature annual range (difference between maximum of warmest period and minimum of coldest period)

0.064

-0.459

0.002

Mean temperature of warmest quarter

0.260

-0.260

0.047

Precipitation of wettest quarter

0.248

0.175

-0.274

Precipitation seasonality (coefficient of variation of monthly mean precipitation)

0.203

0.090

-0.396

Precipitation of coldest quarter

-0.075

0.059

0.365

Beginning of growing season (Julian day when mean temperature > 5 ºC for 5 days consecutively)

-0.163

-0.146

-0.466

End of growing season (Julian day when minimum temperature < -2 °C)

0.189

0.009

0.279

Length of growing season

0.201

0.093

0.433

Total growing season precipitation

0.288

0.169

-0.050

Growing degree days during growing season

0.280

-0.186

0.132

Annual mean temperature (mean of monthly means)

0.309

0.109

0.106

Annual maximum temperature (mean of monthly maximums)

0.319

0.069

0.047

Mean temperature of growing season

0.211

-0.281

-0.144

Temperature range of growing season

0.257

-0.274

0.005

 

 

 

 

Proportion of variance explained

49.68 %

22.33 %

13.77 %

 

FigD1

Fig. D1. Climate has significantly shifted in the Taiga Plains over the past 60 years in both northern (> 64 º latitude) and southern sites (<64 º latitude). Each point represents a mean for all sites in the north or south in each year. (A) Annual precipitation is significantly greater in the south than the north (F1,118 = 97.58, p < 0.001), although there is no significant change over time (F1,118 = 0.66, p = 0.4165). (B) Annual mean temperature is significantly higher in the south than the north (F1,118 = 349.43, p < 0.001), and has increased significantly with time (F1,118 = 65.96, p < 0.001). (C) The growing season is longer in the south than the north (F1,118 = 127.47, p < 0.001), and has increased significantly with time (F1,118 = 4.55, p = 0.035). (D) The number of growing season degree-days is significantly greater in the south (F1,118 = 166.27, p < 0.001), and has significantly increased with time (F1,118 = 12.42, p < 0.001).


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