1 Terminology and acronyms

Athough all georeferenced data can be considered geodata, in this material we use the following terms in the order listed below in our workflows:

  • raw geodata - considered as raw data obtained for a harmonised description of the environment. This may include tables with coordinates, raster or vector data. It can be anything that has been or can be used to create ecogeographical variables, with or without slight processing.

  • geodata product - processed raw geodata that have undegone heavy modifications, e.g.  spatial overlays and combinations of different sets of raw geodata, and are used as input data. In this document, geodata products are categorical raster layers that match the CRS and the pixel locations of input data. When split by categories, they become input data. The processing step of creating geodata products is necessary when decisions about the order of spatial overlays are important. For example, in a high-resolution pixel, there can only be water or forest, if the edge between water and forest need to be calculated.

  • input data or input layers - very-high resolution (multiple times higher than that used for ecogeographical variables) raster data that are the direct input for the creation of most of the ecogeographical variables. The creation of such layers is particularly useful alongside geodata products, as dealing with border misalignment or decisions regarding the order of spatial overlays, as well as simple geoprocessing, is much faster with raster data.

  • ecogeographical variables (EGVs) - this is the final product of the workflow describing environment for statistical analysis (e.g. species distribution modelling). They are suitable also for publishing due to standardisation of the values. In other words, these are standardised landscape ecological variables in the form of high-resolution raster layers (we use 1 ha cells). Each layer contains values representing the environment within the cell footprint or a summary of focal neighbours. In our case, each layer is of quantitative data describing a natural quantity (e.g. timber volume, mean annual temperature), or quantified information of categories (e.g. the fraction of class’s area in an analysis cell or some neighbourhood, the number of pixels creating an edge of a certain class or between two classes in the analysis cell or some neighbourhood). The values of each layer are standardised: for each cell, the layer mean is subtracted and the result is divided by the root mean square error. Therefore, the values are more suitable for modelling, and the layers can be made publicly available as they do not directly provide exact sensitive information.

In this material, we use the term species distribution modelling (SDM) as a more broadly used term, that is synonymous with ecological niche analysis and ecological niche modelling.

Tree species groups:

coniferous - following species (codes) as used in the national forest stand-level-inventory database:

  • pines (1, 14, 22)

  • spruces (3, 15)

  • larch (13)

  • firs (23, 28)

boreal deciduous - following species (codes) as used in the national forest stand-level-inventory database:

  • birches (4)

  • black alder (6)

  • aspens (8, 19, 68)

  • grey alder (9)

  • willows (20, 21)

  • rowan (32)

  • eve (35)

temperate deciduous - following species (codes) as used in the national forest stand-level-inventory database:

  • oaks (10, 61)

  • ashes (11, 64)

  • lindens (12, 62)

  • elms (16, 65)

  • beech (17)

  • hornbeam (18)

  • maples (24, 63)

  • cherry (25)

  • apple (26)

  • pear (27)

  • yew (29)

  • acacia (50)

  • walnut (66)

  • chestnut (67)

  • robinia (69)

Forest stand age groups (vgr) as used in the national forest stand-level-inventory database:

  • young stands (vgr = 1) in coniferous trees, ashes and oaks - until 40 years, in grey alder - until 10 years, in other tree species - until 20 years;

  • medium aged stands (vgr = 2 or vgr = 3) are between young stands (vgr = 1) and legal rotation age;

  • old stands (vgr = 4 or vgr = 5) are stands exceeding legal rotation age. This is defined in by law based on tree species and site quality class (bonity). Generally for oaks, pines and larches it is 101 or 121 years, for spruces, ashes, limes, elms and maples it is 81 years, for birches it is 71 or 51 years, for black alder it is 71 years, for aspens it is 41 years. Currently, there is no minimum rotation age in grey alder. We used 35 years, as it is the age of the youngest stand registered as “full grown” in the databse. This was necessary for the harmonization of EGVs throughout forests.

Acronyms:

CRS - coordinate reference system

DW - Dynamic World

EDI - Institute of Electronics and Computer Sciences

EGV - ecogeographical variables

GEE - Google Earth Engine

SDM - species distribution modelling

SDMs - species distribution models

LAD - Rural Support Service

LĢIA - Latvian Geospatial Information Agency

LULC - Land use and land cover

LU - University of Latvia

LU ĢZZF - University of Latvia Faculty of Geography and Earth Sciences

LVM - state owned Joint Stock Company “Latvia’s State Forests”

LVMI Silava - Latvian State Forest Research Institute “Silava”

NDMI - normalized difference moisture index

NDVI - normalized difference vegetation index

NDWI - normalized difference water index

MVR - State Forest Service’s stand level inventory database “Forest State Registry”

VMD - State Forest Service