FUNDAMENTALS OF PHYTOCENOLOGY AND PLANT GEOGRAPHY - T. P. Larkina - 2017

CHAPTER 2. FUNDAMENTALS OF PLANT GEOGRAPHY

2.1. Distribution of Plant Species Across the Globe

Plant geography, or phytogeography, is a branch of botany and physical geography that studies the geographic distribution of plants.

The Earth's vegetation cover is highly diverse, encompassing a vast number of phytocenoses with various families and species of both higher and lower plants.

The immense variety of plant species is unevenly distributed across different Regions of the globe. The highest diversity of species—and consequently of plant communities—is observed in tropical regions (Africa, Brazil), reaching up to 40,000 species, whereas the lowest diversity is found in northern regions (such as Greenland and Svalbard), with only a few hundred species.

2.2. The Theory of the Range

Determining the geographic range (areal) of a species, genus, family, or plant community is one of the primary tasks of botanical geography.

The range (areal) of a particular plant species refers to the geographic area within which this species occurs on the Earth's surface. METABOLISM/2.html">THE CONCEPT OF a range applies not only to species but also to genera, families, and higher taxa, as well as to individual plant communities (e.g., oxalis-spruce forests, raised bogs). Plant geography deals primarily with the ranges of various species as the primary and foundational empirical material.

N. F. Reimers distinguishes the following types of ranges:

Species range — the region of geographic distribution (terrestrial or aquatic) of individuals belonging to the species in question, regardless of the degree of residency of their habitat in a given locality, but excluding (or, according to other viewpoints, including) instances of accidental Introduction (casuals, vagrants, or floaters) into neighboring regions.

Restored range. 1) The area of past Distribution of a species, other taxonomic group, or community type during a historical period, outlined by the extreme points of paleontological (archaeological) finds and literary records (chronicles, annals, etc.), i.e., essentially a mentally or cartographically reconstructed range (in biogeography); 2) The range of a species that was recently rare or on the verge of extinction, which has re-established its natural boundaries from the past, prior to anthropogenic disturbances (in nature conservation).

Secondary range — A region occupied by a species, other taxonomic category, or community type As a result of range expansion or relocation.

Natural range — A range unaffected (neither expanded, restricted, nor otherwise altered) by human activity.

Artificial range — The range of a living taxonomic group that has been restricted, expanded, or artificially shaped by human intentional or unintentional activity (including a disjunct range type 1 and a patchy range).

Cosmopolitan range — The distribution area of a species or other taxonomic group covering vast land or Water expanses (at least one-third of the globe).

Ribbon (linear) range — A species range elongated in strip-like formations along certain natural features or boundaries (such as a river valley, coastline, etc.).

Minimum range (minimal areal): 1) The smallest area required for a species to avoid natural extinction; 2) The minimum sampling area needed to identify a plant association.

Mosaic range — A species range composed of many small patches of suitable habitats.

Primary (autochthonous) range — The region of initial formation of a species, other taxonomic group, or community type.

Potential range. 1) A region currently unoccupied by a species, possessing suitable ecological conditions within the adaptive zone accessible to the species; 2) The historical habitat area of a species where conditions for its survival still persist, but from which it was eradicated (including by human agency).

Discontinuous range. 1) A species range fragmented by human activity into significant isolated areas. A subtype of an artificial range; 2) A species range interrupted by the distribution area of another species. A subtype of a natural range.

Range of pulsation (fluctuation) — A region to which a species range periodically expands during years most favorable for its survival.

Patchy range — The range of a species, other taxonomic group, or community type fragmented by human activity into small isolated patches, or formed by small pockets of anthropogenic habitats (e.g., settlements for synanthropic species). A subtype of an artificial range.

Disjunct (broken) range. 1) A species range split into a few significant areas as a result of the geological History of the region or species evolution (e.g., European-Far Eastern disjunctions in broadleaved forest species); a subtype of a natural range; 2) A term sometimes used synonymously with a discontinuous range.

Expanding range - the habitat of a species that is expanding due to biological or anthropogenic causes.

Relict range - the range of a species foreign to the current geographical conditions of the area. It is typically small in size.

Modern (recent) range - the currently existing BOUNDARIES OF THE habitat of a species, other taxonomic group, or community type.

Contracting (narrowing) range - the range of a taxonomic group or community type that is decreasing due to natural or anthropogenic causes.

Continuous range - the range of a taxonomic group or community type without significant gaps (though it may be mosaic, ribbon-like, etc.).

Ecological range - a region where a species can inhabit due to the presence of suitable conditions, regardless of where this region is located or whether it is separated by barriers impassable to the species.

Endemic range - a very narrow area of distribution of a species, other taxonomic group, or biotic community type.

The concept of a "range" is much broader than that of a "habitat," so they should not be confused or conflated: within its range, a species—and even plant communities—may not occur everywhere, but rather in specific habitats characteristic of them.

2.3. Shape, Size, and Boundaries of a Species Range

The ranges of various species are extremely diverse in shape and size, and the range of each species is, as a rule, individual and unique.

Weeds have the most extensive ranges, often distributed across several continents. For example, shepherd's purse (Capsella bursa-pastoris), Canadian fleabane (Erigeron canadensis), and many others, possessing little demand for living conditions and thriving in disturbed habitats where plant competition is weaker, are widely distributed across the globe.

Some aquatic plants also have wide distribution boundaries, such as Canadian waterweed (Elodea canadensis) and common duckweed (Lemna minor). This is because these plants do not experience water shortages and depend little on climate, allowing them to grow well in different climatic zones. Additionally, the vegetative parts, seeds, and fruits of these plants are dispersed by water, which contributes to their rapid settlement across the territory.

Conversely, some plants have an extremely limited range; for example, the giant sequoia (Sequoiadendron giganteum), or mammoth tree (Fig. 16), which in the wild is distributed only in a very small area of the southwestern part of North America.

Over geologically short periods of time (tens and hundreds of years), the ranges of many plant species remain stable, and their boundaries do not undergo drastic changes. The most important factor determining THE POSITION OF a range boundary is climate. In different cases, various specific climatic features play a decisive role—for example, a lack of summer warmth, preventing plants from preparing for winter and leading to their death, or excessively low temperatures in winter, causing plants to freeze. When climate proves to be the decisive factor determining the limit of a plant's distribution, it is referred to as a climatically determined range boundary.

The position of a range boundary is also determined by natural barriers (the sea, high mountains, etc.) that the species is unable to overcome due to its biological characteristics.

If the boundary of a species' range is determined by soil factors, such a boundary is called edaphically determined.

A range boundary can be competitive when its position is determined by the interactions between two plants, one of which is stronger and dictates the boundary limit of the second species.