Visualization
Let’s visualize some of the twig data by oak species, and then bysize index.
Twigs are the smallest above ground woody component of a tree. Twigsare responsible for supporting the delicate tissues needed to growleaves and protect the buds during the dormant season. Because twigmeasurements are the basis for the Real Twig method, and publiclyavailable databases of twigs are limited, we present a database of twigmeasurements for a wide range of tree genera, species, and qualitativeindices.
The twig radius is the most important part of Real Twig. We recommendthe following process of selecting a twig radius:
Directly measure a twig on the focal tree wheneverpossible.
If direct measurements are not possible, use a species specificmeasurement from thetwigs database.
If the species is not present in the database but the species isknown, use a qualitative index describing the twig, such asslender, orstout (often found in many botanicalmanuals) to pick a radius from thetwigs_indexdatabase.
If none of the above are possible, use the genus average valuefrom thetwigs database.
The reason we advocate for a qualitative index over the genusaverage, is that genera with many species can have a wide range of twigradii. The qualitative index ensures the measurement is closer to thetrue value than a potentially biased average. However, if the species inthe genera are similar the genus average can be used with good results(Morales and MacFarlane 2024).
You can install the package directly fromCRAN:
Or the latest development version fromGitHub:
The first step is to load the rTwig package.
The twig database is built directly into rTwig and can be called asfollows:
# If rTwig hasn't been loaded, but just the twigs are neededrTwig::twigs#> # A tibble: 104 × 7#> scientific_name radius_mm n min max std cv#> <chr> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl>#> 1 Abies concolor 1.43 21 0.89 1.9 0.28 0.19#> 2 Abies spp. 1.43 21 0.89 1.9 0.28 0.19#> 3 Acer platanoides 1.39 30 0.89 2.03 0.3 0.21#> 4 Acer rubrum 1.18 30 0.89 1.52 0.16 0.14#> 5 Acer saccharinum 1.41 14 0.89 1.9 0.27 0.2#> 6 Acer saccharum 1.2 30 0.89 1.65 0.23 0.19#> 7 Acer spp. 1.29 104 0.89 2.03 0.23 0.18#> 8 Aesculus flava 2.96 14 2.29 4.44 0.58 0.19#> 9 Aesculus spp. 2.96 14 2.29 4.44 0.58 0.19#> 10 Betula nigra 0.85 30 0.51 1.52 0.23 0.27#> # ℹ 94 more rowsThe database is broken into 7 different columns.scientific_name is the specific epithet. Genus spp. is theaverage of all of the species in the genus.radius_mm is thetwig radius in millimeters. For each species,n is the numberof unique twig samples taken,min is the minimum twig radius,max is the max twig radius,std is the standarddeviation, andcv is the coefficient of variation.
Let’s see the breakdown of species.
unique(twigs$scientific_name)#> [1] "Abies concolor" "Abies spp."#> [3] "Acer platanoides" "Acer rubrum"#> [5] "Acer saccharinum" "Acer saccharum"#> [7] "Acer spp." "Aesculus flava"#> [9] "Aesculus spp." "Betula nigra"#> [11] "Betula spp." "Carya cordiformis"#> [13] "Carya ovata" "Carya spp."#> [15] "Castanea dentata" "Castanea spp."#> [17] "Cercis canadensis" "Cercis spp."#> [19] "Cladrastis kentukea" "Cladrastis spp."#> [21] "Cornus mas" "Cornus officinalis"#> [23] "Cornus spp." "Crataegus spp."#> [25] "Fagus grandifolia" "Fagus spp."#> [27] "Fagus sylvatica" "Fraxinus americana"#> [29] "Fraxinus pennsylvanica" "Fraxinus quadrangulata"#> [31] "Fraxinus spp." "Ginkgo biloba"#> [33] "Ginkgo spp." "Gleditsia spp."#> [35] "Gleditsia triacanthos" "Gymnocladus dioicus"#> [37] "Gymnocladus spp." "Gymnopodium floribundum"#> [39] "Gymnopodium spp." "Juglans cinerea"#> [41] "Juglans nigra" "Juglans spp."#> [43] "Laguncularia racemosa" "Laguncularia spp."#> [45] "Larix laricina" "Larix spp."#> [47] "Liquidambar spp." "Liquidambar styraciflua"#> [49] "Liriodendron spp." "Liriodendron tulipifera"#> [51] "Magnolia acuminata" "Magnolia spp."#> [53] "Malus spp." "Metasequoia glyptostroboides"#> [55] "Metasequoia spp." "Nyssa spp."#> [57] "Nyssa sylvatica" "Ostrya spp."#> [59] "Ostrya virginiana" "Phellodendron amurense"#> [61] "Phellodendron spp." "Picea abies"#> [63] "Picea omorika" "Picea pungens"#> [65] "Picea spp." "Pinus nigra"#> [67] "Pinus spp." "Pinus strobus"#> [69] "Platanus acerifolia" "Platanus occidentalis"#> [71] "Platanus spp." "Populus deltoides"#> [73] "Populus spp." "Prunus serotina"#> [75] "Prunus spp." "Prunus virginiana"#> [77] "Quercus acutissima" "Quercus alba"#> [79] "Quercus bicolor" "Quercus coccinea"#> [81] "Quercus ellipsoidalis" "Quercus imbricaria"#> [83] "Quercus macrocarpa" "Quercus michauxii"#> [85] "Quercus muehlenbergii" "Quercus palustris"#> [87] "Quercus robur" "Quercus rubra"#> [89] "Quercus shumardii" "Quercus spp."#> [91] "Quercus velutina" "Rhizophora mangle"#> [93] "Rhizophora spp." "Thuja occidentalis"#> [95] "Thuja spp." "Tilia americana"#> [97] "Tilia spp." "Tilia tomentosa"#> [99] "Tsuga canadensis" "Tsuga spp."#> [101] "Ulmus americana" "Ulmus pumila"#> [103] "Ulmus rubra" "Ulmus spp."Similarly, we also provide the same data base broken down by twigsize index. The size classes were adapted from(Coder 2021).
Let’s visualize some of the twig data by oak species, and then bysize index.