Limiting factors temperature, soil, water, humidity, light and fire

• Limiting factors: are environmental factors or conditions that can restrict the growth, distribution, abundance, or survival of a species or a population within an ecosystem. These factors can vary depending on the species and the specific ecosystem. These can be either physical or biological factors which can be identified through a response of increased or decreased growth, abundance, or distribution of a population, when the factor is changed and when the other factors necessary to life are not. Here, we’ll discuss some of the common limiting factors:
• Density dependent factors: Density dependent factors are those factors whose effect on a population is determined by the total size of the population. Predation and disease, as well as resource availability, are all examples of density dependent factors. As an example, disease is likely to spread quicker through a larger, denser population, impacting the number of individuals within the population more than it would in a smaller, more widely dispersed population.

• Density independent factors: A density independent limiting factor is one which limits the size of a population, but whose effect is not dependent on the size of the population (the number of individuals). Examples of density independent factors include environmentally stressful events such as earthquakes, tsunamis, and volcanic eruptions, as well as sudden climate changes such as drought or flood, and destructive occurrences, such as the input of extreme environmental pollutants. Density independent factors will usually kill all members of a population, regardless of the population size.

• Physical and biological limiting factors: Limiting factors can also be split into further categories. Physical factors or abiotic factors include temperature, water availability, oxygen, salinity, light, food and nutrients; biological factors or biotic factors, involve interactions between organisms such as predation, competition, parasitism and herbivore.

• Environmental conditions: Limiting factors are also present as environmental conditions. Two of the most prominent examples are temperature and precipitation; these are widely affected by the climate, and seasonal changes within the climate. The effect that each factor has on a particular organism is determined by each individual species.
• Biotic factors: As well as resource and climatic factors affecting population growth, biotic factors such as predation, herbivory, parasitism, and interspecific and intraspecific competition, are also limiting factors; these tend to be density dependent factors. Parasitism, like disease, is generally more destructive to large, dense populations because the parasite is able to effectively parasitize more individuals if they are in close contact. Within tropical ecosystems, the fungus is a prominent parasite, and has many strains specialized on different species.
• Human limiting factors: The increase in human population is responsible for placing many limiting factors on species that did not historically exist. Density dependent limiting factors such as decreased availability of space due to deforestation is a global issue, causing decline and extinctions in many populations. Resources are also increasingly scarce due to hunting and leaching of nutrients from soil, which causes intraspecific and interspecific competition within and between populations. Removal of predators has also disturbed the balance of natural biotic, cycle of predators and prey; in some cases, prey animals have been able to thrive in the absence of predators, exceeding the carrying capacity of ecosystems and causing environmental damage. Predators have also been introduced as invasive species into ecosystems, putting pressure on prey populations and thus on the prey’s natural predators.

Temperature: Temperature is one of the important factors which affect almost all the metabolic activities of an organism. Every physiological process in an organism requires an optimum temperature at which it shows the maximum metabolic rate. Three limits of temperature can be recognized for any organism.

Minimum temperature – Physiological activities are lowest.

Optimum temperature – Physiological activities are maximum.

Maximum temperature – Physiological activities will stop.

Effects of temperature

Temperature affects the enzymatic action of all the bio-chemical reactions in a plant body.

It influences CO₂ and O₂ solubility in the biological systems. Increases respiration and stimulates growth of seedlings.

Low temperature with high humidity can spread diseases to plants.

The varying temperature with moisture determines the distribution of the vegetation types.

Temperature affects the metabolic rates, growth, and reproduction of organisms. Extreme temperatures, both hot and cold, can limit the distribution of species.

Examples: Cold temperatures limit the distribution of tropical plants, while high temperatures can restrict the survival of cold-blooded animals in deserts.

Water: Limitation of water intake reduces animal performance quicker and more dramatically than any other nutrient deficiency (Boyles). Water constitutes approximately 60 to 70 percent of an animal’s live weight and consuming water is more important than consuming food (Faries, Sweeten & Reagor, 1997). Domesticated animals can live about sixty days without food but only about seven days without water. Livestock should be given all the water they can drink because animals that do not drink enough water may suffer stress or dehydration. Signs of dehydration or lack of water are tightening of the skin, loss of weight and drying of mucous membranes and eyes. Stress accompanying lack of water intake may need special considerations. Newly arrived animals may refuse water at first due to differences in palatability. One should allow them to become accustomed to a new water supply by mixing water from old and new sources. If this is not possible, then intake should be monitored to be sure no signs of dehydration occur until animals show adjustment to the new water source.

Table 1 shows estimates of daily consumption of water for various livestock groups. 

Water Functions

1. Eliminate waste products of digestion and metabolism,
2. Regulate blood osmotic pressure,
3. Produce milk and saliva,
4. Transport nutrients, hormone and other chemical messages within the body, and aid in temperature regulation affected by evaporation of water from the skin and respiratory tract.

Effect: Water availability is a critical limiting factor, especially in arid regions. Lack of water can limit the distribution and abundance of both terrestrial and aquatic organisms.

Examples: Drought can limit the growth of vegetation and the survival of many species, while water scarcity can limit the distribution of aquatic organisms.

Humidity: Humidity is essential for life. It is often expressed as relative humidity, which is the ratio of the current absolute humidity relative to the maximum humidity at a specific temperature, indicating the amount of water vapor in the air at that temperature. As a key environmental factor, it plays an important role in air quality (Tian et al. 2014; Cheng et al. 2015) and climate control (Sherwood and Fu 2014).

Effect: Humidity, or the amount of moisture in the air, can limit the distribution of organisms, particularly those adapted to specific humidity ranges.

Examples: Some reptiles, like desert-dwelling lizards, are adapted to low humidity levels and may not survive in high-humidity environments.

Light: also affects divergent aspects of animal’s life. The growth, coloration of plumage or body, migration, reproduction and diapause are affected by light in various insects, birds, fishes, reptiles and mammals. Many animals prefer to remain in dark, while others like hydroids fail to survive in absence of light. Among the animals various kinds of photo-receptor systems exist. These include ‘eyespots’ consisting of amylum granules as in Protozoa; flat ocelli in jellyfish; pit eyes in gastropods; vesicular eyes as in polychaetes, molluscs and some vertebrates; telescopic eyes in certain fishes; compound eyes in Crustacea and insects; simple eyes or ocelli in other arthropods and dermal light receptors in other animals.

Protoplasm: The bodies of most animals remain protected by some sort of body covering which save animal tissues from the lethal effects of solar radiations. But, some­times sun rays penetrate such covers and cause excitation, activa­tion, ionization and heating of protoplasm of different body cells. Ultraviolet rays are known to cause mutational changes in the DNA of various organisms.

Metabolism: The metabolic rate of diffe­rent animals is greatly influenced by light. The increased intensity of light results in an increase in enzyme activity, general metabolic rate and solubility of salts and minerals in the protoplasm. Cave dwe­lling animals are found to be sluggish in their habits and to contain slow rate of metabolism.

Pigmentation: Light influences pigmenta­tion in animals. Cave animals lack skin pigments. If they are kept out of darkness for a long time, they regain skin pigmentation. The darkly pigmented skin of human inhabitants of the tropics also indicates the effect of sunlight on skin pigmentation. The skin pig­ment’s synthesis is dependent on the sunlight.

 Movements: The influence of light on the movement of animals is evident in lower animals. Oriented locomotor movements towards and away from a source of light is called phototaxis. Positively phototactic animals such as Euglena, Ranatra, etc., move towards the source of light, while negatively phototactic animals such as planarians, earthworms, slugs, cope- pods, siphonophores, etc., move away from the source of light.

Effect: Light availability, intensity, and duration affect the photosynthesis and growth of plants, which can, in turn, limit the availability of food and habitat for other organisms.

Examples: Understory plants in dense forests are limited by low light levels, and deep-sea organisms are adapted to extremely low light conditions.

Fire: The immediate effects of fire for animals include death, injury and survival. Animals which survive the fire itself may later starve or be exposed to predators as a result of a lack of food and/or cover. During a fire event, less mobile animals, such as many reptiles and some of the larger mammals, tend to take cover in burrows or tree hollows. Highly mobile animals (including birds, for example) may leave the fire area before or during a fire. To survive, in areas not affected by the fire, they need to outcompete other animals which have also retreated to unburnt areas, or return to the burnt area. Fast moving, high intensity fires can cause high mortality. Intense fires burn into the tree crown and hollows and there may be few or no nearby refuge areas for animals. Intense heat can also penetrate underground. Invertebrates such as insects and spiders are also mainly killed in high intensity fires, when bark and litter layers are destroyed. They may survive lower intensity fires in the litter and soil, or under bark. Flying insects have a higher chance of survival due to their mobility. They may move away and return after the fire. Invertebrates are an important food source after a fire, particularly for surviving birds and reptiles. Various animal species respond differently to fire. Some species, such as the Flame Robin, are attracted to recently burnt areas and are absent in areas that have not been recently burnt.

Effect: Fire is a crucial ecological factor in some ecosystems, and its frequency and intensity can limit the types of vegetation and wildlife that can thrive.

Examples: Fire-adapted plant species in fire-prone ecosystems may not survive in areas where fires are infrequent.

Understanding these limiting factors is essential in ecology and conservation biology because they determine the distribution and abundance of species and can be used to predict the impact of environmental changes. For example, in the context of climate change, shifts in temperature and precipitation patterns can alter the limiting factors for various species, potentially leading to changes in their distribution and abundance. Conservation efforts often aim to address or mitigate limiting factors to protect endangered species and preserve ecosystem health.

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Faries, F.C., Sweeten, J.M., & Reagor, J.C. (1997). Water Quality: Its relationship to livestock (L-2374). Texas Agricultural Extension Service, The Texas A&M University.

Sherwood S, Fu Q. 2014. Climate change. A drier future?Science, 343, 737–739 Tian G, Qiao Z, Xu X. 2014. Characteristics of particulate matter (PM10) and its relationship with meteorological factorsduring 2001–2012 in Beijing. Environmental Pollution, 192, 266–274.