24 hours of sunlight
In the Arctic tundra, the summer season is unique in the sense that the Sun is seen in the sky during the day as well as night.
If there are no reptiles in a tundra region, it's for a reason. Reptiles are cold-blooded species, meaning their own body temperature is dependent on the temperature of their surroundings. They can only survive in warm regions―even in hot deserts. However, in cold regions, like the Arctic and Antarctic tundra, the temperature acts as a limiting factor for them. Similarly, lack of vegetation is the limiting factor, which is responsible for the absence of herbivores from the Antarctic tundra.
Limiting Factors in Tundras Explained
Limiting factors don't just dictate the distribution of species, but also govern their growth and abundance. If food availability is an issue, Arctic lemmings will continue to reproduce, but the litter size will be small. That, in turn, will control their population and bring it down to sustainable levels. There are quite a few biotic and abiotic factors that directly or indirectly affect the biodiversity levels of a tundra biome. We have discussed them below.
The temperature in a tundra biome ranges between −94°F in winter to 54°F in summer. Like we said, this makes it difficult for reptiles to live in this biome. The only species of snake found to the north of the Arctic circle is the European viper (Vipera berus). In contrast, mammals can survive in this harsh climate, owing to their ability to regulate their body temperature.
As a tundra biome is located at the poles, it is in darkness for a considerable part of the year. On the other hand, during a part of the year, it is constantly in light. As a result, only those species of plants and animals that can survive in the dark thrive in this ecosystem. Lack of sunlight for a part of the year also means that plants grow in a tundra biome only during summer.
Freezing temperature and sunlight are not the only factors which limit the growth of plants in this biome. Besides them, tundra plants also bear the brunt of poor soil. The soil in this biome is not just nutrient deficient, but also very shallow. As a result, trees cannot delve their root deep into it.
Limited growing season
As the region is subjected to darkness for nearly half the year, the process of photosynthesis is hindered, which, in turn, limits the growth of plants. The end result in a short growing season. This seasonal availability of food reflects on the abundance of animals in this ecosystem.
The shortage of food supply resulting from lack of sunlight for a part of the year, short growing season, and poor soil limits the population of herbivores and omnivores by forcing them to migrate in search of food and affecting their rate of reproduction. The size of litter in many tundra species is determined by the availability of food. The case of Arctic lemmings, which we discussed earlier, is an apt example of the same.
Competition and predation both act as limiting factors in a tundra biome. When the number of caribous in the Arctic tundra comes down, carnivorous species like gray wolves and wolverines start competing. Eventually, the food shortage resulting from this competition either results in their death, affects their rate of reproduction, or prompts them to migrate, thus restoring the balance in a tundra ecosystem.
When the caribou population increases, gray wolves have abundance of food at their disposal. This, in turn, boosts their reproduction rate and results in an increase in their population. In this manner, the population of both species is balanced out.
A tundra biome may come across as devoid of life, but that is not the case. Despite these limiting factors, it has its unique blend of diversity. In winter, life does come to a standstill here. As the temperature falls, species like the Arctic ground squirrels and polar bears enter hibernation, while caribous and tundra swans migrate south to warmer areas with abundance of food. When caribous migrate, gray wolves follow them, as they are largely dependent on them for their dietary requirements. As a result, the region experiences a phase of darkness. In summer though, things return to normalcy and life flourishes in the biome, which otherwise seems devoid of life.