RIVERSIDE FOREST: CHARACTERISTICS, DISTRIBUTION, FLORA AND FAUNA - ENVIRONMENT - 2025

The riverside or gallery forests are the evergreen ecosystems that develop on the edges of water courses. This occurs because these areas maintain soil moisture during different times of the year.

They are variable ecosystems in space and time. Spatial variations are evidenced in changes in the longitudinal, lateral and vertical structure of the forest. Temporal variations may be associated with seasonality or random events.

Gallery forest on the Groot River in South Africa. Source: Paul venter at English Wikipedia, from Wikimedia Commons

They constitute the habitat of a large number of species: they include plant forms with a high diversity of morphological, physiological and reproductive adaptations that have allowed them to survive in flooded soils. They are habitat, refuge and corridor for many animals.

In addition, they are important for the maintenance of environmental quality, since they intervene in the capture of polluting nutrients from water and sediments. For this reason, they are ecosystems that can be used to promote environmental sanitation of contaminated areas.

General characteristics

Ecology

Riparian forests include the most diverse and productive plant communities. They generate a great diversity of habitats and microclimates that support a high number of species.

In addition, they contribute to connectivity between distant areas, serving as ecological corridors that favor the dispersal of individuals and the flow of genes.

On the other hand, the contribution of energy and matter made by the forest is essential for the maintenance of the aquatic trophic web.

Leaves, branches, and logs that fall into rivers and streams are caught by fallen trees and rocks. These provide food and shelter for small fish, crustaceans, amphibians, insects, among others, constituting the basis of the food web of aquatic ecosystems.

Microclimate

Riparian forests have an important effect in controlling the microclimate of rivers and streams through the control of extreme temperatures.

In very hot climates or seasons, the forest sequesters solar radiation reducing the temperature of the water and, with it, evaporation. On the other hand, in cold climates or times, the forest retains the heat from the soil and the body of water, keeping the water at a higher temperature.

Water quality

Riparian forests are very important in environmental sanitation and in maintaining the quality of river water. These remove sediments from the water and sequester, filter or transform nutrients and other pollutants.

Nitrate removal

These ecosystems remove nitrate that is found in excess in water bodies, most of which comes from unsustainable agricultural practices. The processes involved in this segment of the nitrogen cycle are denitrification and nitrate uptake by plants.

Denitrification is the biochemical transformation of nitrate into nitrogen gas, either in the form of molecular nitrogen or nitrogen oxide. Thus, the nitrogen dissolved in the water is extracted and released into the atmosphere.

On the other hand, nitrate taken up by plants can come from soil or water. They incorporate it into their tissues, turning it into plant biomass. In this way, nitrogen is sequestered from the medium and stored for long periods of time. Both mechanisms reduce the amount of available nitrogen dissolved in the water.

Pollutant removal

Some microorganisms can immobilize pollutants present in riparian forests. This can occur through various metabolic pathways (anaerobic, aerobic, heterotrophic, or chemoautotrophic).

Microorganisms take nutrients dissolved in water and incorporate them into your body. With the death and decomposition of microbial cells, these substances are sequestered in the organic matter of the soil.

In this way, the riparian forest soils can store large amounts of pollutants in the long term.

Sediment control

Rains and floods wash away sediments that are intercepted by leaf litter, decomposing organic matter and tree roots. Thus, the particles that make up the sediments are deposited in the forest, preventing them from entering the rivers.

Distribution

Riparian forests have a very wide geographic and climatic distribution, because they only require a watercourse for their development. Thus, we can find them in the intertropical zone and the temperate zone of the planet and in the tropical, subtropical and temperate climates.

Flora

The vegetation associated with riparian forests has numerous morphological, physiological and reproductive adaptations, which allow it to survive in highly energetic environments subject to permanent or seasonal flooding.

Some morphological adaptations respond to low oxygen levels during floods. For example, the presence of air spaces in the branches and roots (aerenchyma) allows the obtaining of oxygen from the aerial zones of the plant.

This adaptation is common in species of the Cyperaceae and Juncaceae families, which grow in the floodplains of riparian forests.

Another morphological adaptation to anoxia in soils is the adventitious roots or pneumatophores; these develop on the ground, allowing the absorption of oxygen from the air. They have small pores called lenticels, where the air is absorbed and distributed to the entire plant by osmosis.

On the other hand, faced with the diverse selective pressures present in riparian forests, the species present a great diversity of reproductive strategies.

Among the most prominent are the presence of both sexual and asexual reproduction, the optimization of the size of the seeds and the forms of dispersal of the seeds, among others.

Fauna

Riparian forests provide an ideal habitat for a great diversity of animals. This is so due to the high productivity, the presence of water, the stability of the microclimate and the large number of microhabitats that characterize these ecosystems.

The different species of wildlife can be forest residents or occasional visitors who find food, shelter or water in the forest. The availability of food depends on the type of vegetation; broadly, it includes fruits, foliage, seeds, organic matter, and invertebrates.

Rivers and streams guarantee the availability of water in riverside forests. The water is used by the different animals as a habitat or as a source of hydration, food or reproduction.

The riverside forests provide shelter for different species of animals. The fish take advantage of the spaces between the roots for the reproduction and growth of fingerlings, since they are areas of difficult access for predators.

For many mammals, the forest represents a suitable habitat. However, large mammals require large territories, so they can make use of extensive riparian forests or that constitute ecological corridors between larger areas.

Other smaller mammals, or that may make partial use of the forest, can be identified in smaller riparian forests.

Structure

Longitudinal structure

The longitudinal structure of the riparian forest depends on the changes in the characteristics of the rivers, from the headwaters to the mouth.

These include important variations in the quantity (flow) and intensity of the water course, as well as the quantity of sediments transported.

Lateral or transverse structure

Riparian forests constitute a transition ecosystem between an aquatic environment and a terrestrial one. In this longitudinal gradient, the riparian forest includes a part of the watercourse, the interior of the forest and the transition to the terrestrial ecosystem.

In this plane, the composition of the forest varies according to the tolerance of the different species to different environmental variables.

Some of these variables are the availability of water, the degree of flooding, the intensity of disturbance by sedimentation or erosion, the intensity of light and the temperature.

The transition zone between the water course and the forest is dominated by species that have higher water requirements and that have adaptations that allow them to withstand currents. Shrubs with a high capacity to regenerate and with flexible trunks stand out.

The transition zone between the forest and the terrestrial ecosystem is dominated by species of adapted root systems, which allow them to take water from the groundwater table in drought and resist floods in the rainy season.

Vertical structure

The vertical structure of a well-developed gallery forest is composed of arboreal, arborescent, and shrub strata.

The arboreal layer is made up of trees that can reach more than 40 meters. Depending on factors such as latitude and surroundings, its specific composition can be more or less diverse. The trees are spaced apart and have high and extensive crowns, which generate shade in the lower strata.

The arborescent layer is made up of medium-sized trees, while the shrub layer is characterized by the presence of shrubs that can measure up to 5 meters in height.

Both strata are mainly composed of the juveniles of the trees of the arboreal stratum. These are more densely distributed in forest clearings, where there is greater intensity of light.

Herbaceous stratum

Another stratum present is the herbaceous, which constitutes the lower part of the forest. It is composed of a dense plant formation, with a high number of species. Plants with large leaves dominate, adapted to capture the little light that reaches the interior of the forest.

In mature forests, epiphytic plants are also present, which are associated with the treetops. The lianas, mosses, ferns, among others, stand out.

References

1. Austin, SH Riparian forest handbook. The Virginia Department of Forestry 900 Natural Resources Drive, Suite Charlottesville, Virginia.
2. Klapproth, JC and JE Johnson. (2000). Understanding the Science Behind Riparian Forest Buffers: Effects on Plant and Animal Communities. Virginian cooperative extension.
3. Naiman, RJ; Fetherston, KL; McKay, SJ & Chen, J. 1998. Riparian forests. Pp. 289-323. In: RJ Naiman & RE Bilby (eds.). River ecology and management: lessons from the Pacific Coastal Ecoregion. New York, Springer-Verlag.
4. Rosales, J., (2003). Gallery forests and jungles. In: Aguilera, MM, Azócar, A., & González, JE, (eds.), Biodiversidad en Venezuela, vol. 2. Polar Foundation. Caracas Venezuela. pp 812-826.
5. Wikipedia contributors. (2018, November 8). Riparian forest. In Wikipedia, The Free Encyclopedia. Retrieved 09:20, January 16, 2019, from wikipedia.org