The trait observations included in FRED have been collected from many different types of roots. As you explore the User Interface, you may want to consider selecting only a subset of these root measurements for your analysis (for example, living roots only, absorptive fine roots only, or first-order roots only).
In addition to important root traits such as diameter (or diameter class) and color, ancillary root sampling metadata can facilitate accurate comparisons of root traits within- and among species. There are several options available in the FRED User Interface to filter the data according to your needs.
Species-specific traits, or traits of plants growing in mixed communities?
- Single or multiple species: Selecting ‘Single species’ returns data that were collected for individual species, whereas ‘multiple species’ returns data that were collected for more than one species at a time; for instance, where researchers sampled a mixed plant community and did not identify and sort the roots before measuring them. Selecting ‘single species’ does not mean that all rows of data returned will describe the same species; it only means that there are no mixed-species data in any of the rows.
What kind of root?
- Belowground part: FRED includes BS (belowground stems), CR (coarse roots; roots greater than 2 mm in diameter), FR (fine roots; roots 2 mm or less in diameter), R (rhizomes), TB (all belowground parts, which may or may not include any number of the aforementioned types), TR (all roots, which may include coarse roots, fine roots, or both), unspecified (researchers did not specify which belowground parts they collected), or unspecified roots (researchers collected roots but did not specify which roots they collected).
- Root order: This is based on the centripetal (i.e. morphometric) root ordering scheme: roots of order 1 are the roots at the distal tip of the root system with no roots branching from them; order 2 roots are roots with at least one first-order root branching from them; order 3 roots are roots with second-order roots branching from them, and so on.
- Root functional class: Absorptive roots are typically classified as fine roots of orders 1 through 3, and perform functions associated with resource acquisition, while transport roots are typically classified as fine roots of orders 4 or higher, and perform functions associated with resource transport (McCormack et al. 2015).
- Root vitality: FRED includes roots that are living, dead, both, or unspecified. Choosing ‘both’ returns all rows of data that describe samples that contained both living and dead roots but does not return rows that describe samples containing only living roots or only dead roots.
After download from the FRED User Interface, there are other ways to subset observations based on root characteristics, including:
- Root order range: Select from within a range of root orders [Column IDs F00057 and F00058].
- Root heterorhizy class: Select fibrous or pioneer roots [Column ID F00066].
- Root diameter: Select from within a specific range of root diameters [Column ID F00949 and F00950].
- Root age: Choose a given age [Column ID F00061].
- Root numbering scheme: Choose roots that were ordered according to a centripetal or centrifugal numbering scheme [Column ID F00059].
- Soil depth: Choose roots collected from a given soil depth [Column ID F00985].
What portion of the plant kingdom?
These filters select for accepted plant family, genus, and species names, corresponding to Column IDs F01289, 1286, and 1287, respectively, and verified against The World Flora Online. While there are selection boxes within the filter, you can also type in the entry boxes to activate a drop-down predictive text menu that searches within any part of the plant name. To search by species, select the genus and the species epithet in separate filters rather than attempting to search the entire scientific name in the species box.
What kind of plant? These filters are based on categories and data from the TRY plant trait database.
- Growth form: Describes the morphology or architecture of a plant [Columns F01456].
- Leaf habit: Evergreen, deciduous, or a mixture [Columns F00042].
- Photosynthetic pathway: C3, C4, CAM or a mixture [Columns F00043].
- Plant woodiness: Woody, non-woody, or a mixture [Columns F00044].
Where did the roots grow?
Ancillary data associated with plant growing conditions indicate the conditions under which the root traits were measured, for example:
- Growing conditions: ‘In situ’ selects data for plants which were grown or harvested under natural environments; ‘container’ selects data for plants which were grown under artificial environments, such as in containers, greenhouses, and growth chambers; and ‘hydroponic’ selects data for plants which were grown hydroponically [Column ID F01156].
- Indoor/outdoor: If plants were grown indoors or outdoors [Column ID F01158].
Other ways to subset observations, once downloaded from the FRED User Interface, include:
- Environmental gradients: Collected from across observational gradients, or from experimental treatments that included nutrient, water, temperature, elevated [CO2], burning, disturbance, girdling, or light manipulations and their associated controls [Column ID F01159].
These are only a few of the many ways in which the root trait observations in FRED can be organized for comparison.