Fungi and other soil organisms are key in preserving biodiversity

Fungi are often seen as fruiting bodies, or toadstools (© Camila Duarte)

Largely invisible and often overseen, fungi and other microscopic organisms are highly abundant in soils across the world, and play a fundamental in maintaining the biodiversity and nutrient balances in their ecosystem.

Fungi, although visible in the form of fruiting bodies, or toadstools, during certain times, are largely invisible, existing as microbial threads in the soil. It is estimated that there are some 3.8 million species of fungi, only a fraction of which have been formally described and identified. These organisms are incredibly abundant in soils around the world, an are a key component of biological nutrient cycling, as they break down organic matter, releasing key nutrients and compounds from dead bodies. Fungi are found in a variety of areas such as rainforest, woodland, grasslands and even rocky substrates (in the form of lichens) but are most abundant in open areas such as grasslands and Savannah, where they are important in helping poorer soil uptake nutrients.

Fungi exist mainly as a bundle of microbial threads called a mycelium (© Nigel Cattlin)

In the Amazon rainforest for example, fungi are surprisingly abundant and varied. For example, a teaspoon of rainforest soil is estimated to contain around 1800 species of microscopic organisms (according to a study carried out by Dr Camila Duarte of Germany), at least 400 of which are fungi. These fungi are so diverse and they occupy a variety of niches in the forest, such as lichen (a symbiotic relationship between fungi and microscopic plants), some living commensally in the roots of plants and some as plant pathogens and parasites. Each and every one of these plays a significant role on the forest floor, breaking down organic matter and releasing nutrients back into the soil, to be used by plants and animals.

In this sense, the sheer diversity of fungi in the soil means that it is essential to consider this hidden diversity in conservation efforts, particularly in such fragile ecosystems as the Amazon rainforests. Due to their inconspicuous nature fungi are often overlooked in biological surveys, but they are key for nutrient cycling and also act as carbon sinks, absorbing carbon dioxide from dead organisms.

An abundance of fungal species are found in the soils of the Amazon rainforest (© Nathalia Segato)

Some species are also edible, and are a source of medicine, indeed fungal compounds are being considered as new antibiotic sources in the light of antibiotic resistance. On the other hand, some fungi are considerable pests to crops, while others are disease-causing pathogens which cause disease in humans and animals. There is much to learn about soil fungal diversity, in order to incorporate these organisms into conservation efforts, and to help maintain biodiversity.

Study reveals tropical rainforests covered much of Antarctica 90 million years ago, during time of the Dinosaurs

Study reveals tropical rainforests covered much of Antarctica 90 million years ago, during time of the Dinosaurs

Antarctica is arguably one of the most barren, extreme environments on the planet, with only one permanent terrestrial resident – the Emperor penguin. However, wind the clock back 90 million years, and the continent was far from a frozen wasteland. New evidence has suggested that this icy continent was largely covered in tropical swamp forest, during the time of the Dinosaurs.

The cretaceous period, which spanned from approximately 145 to 66 million years ago, was a very warm period in earth’s history, with an almost worldwide greenhouse climate, and an abundance of vegetation and tropical forests. Antarctica at this time was mostly covered in a swampy, tropical forest and there were no glaciers at the south pole.

An artist’s impression of the ancient swamp forests of Antarctica (© James McKay)

Scientists at the Alfred Wegener institute, Germany, made this discovery by analysing sediment cores drilled from the seafloor in West Antarctica. These cores show a glimpse of the past environment in Antarctica, with sediments nearer to the bottom of the core representing older geological time. At three metres down on the core, representing the late cretaceous period, the sediment composition changed drastically, composed mainly of a coal-like material, soil, roots and pollen. The team identified over 65 types of plant material, indicating the presence of an ancient conifer forest.

The ancient Antarctic forests would have been dominated by cycad plants such as this one (© J. Dazley)

So, what exactly lived in these forests? The forests would have likely been very similar in plant structure to some of the forests in modern-day New Zealand, dominated by towering tree ferns, cycads and coniferous trees. At this time in history, flowering plants had only recently evolved so were likely rare in these forests. Biogeochemical evidence from the sediment cores also revealed that microscopic photosynthetic life such as algae and cyanobacteria were common in warm lakes and rivers.

Australovenator was one of several carnivorous dinosaurs to roam prehistoric Antarctica (© L. Xing)

These forests were dominated by a variety of dinosaur species, which filled many of the ecological roles of forest ecosystems today. There were giant herbivorous dinosaurs such as the long necked Austrosaurus, and Muttaburrasaurus, a close relative of the Iguanadon, whose remains are commonly found on the Isle of Wight. There were also carnivorous dinosaurs such as Cryolophosaurus and Australovenator, and the tiny herbivorous Leaellynasaura, which likely lived in small groups in the forest. Primitive mammals shared the forests with the dinosaurs; they were furry, egg laying species which were likely similar to modern echidnas and platypus. It is also known that the river networks around these forests were home to a giant salamander-like amphibian called Koolasuchus, belonging to an ancient lineage of animals over 250 million years old.

The giant amphibian Koolasuchus was one of the last surviving of it’s kind, and probably fed on smaller dinosaurs (© BBC)

The discovery of these polar forests is not only an exciting advance for palaeontology, but also shows us how key carbon dioxide levels are in the shaping of an environment. It is known that the tropical climate during the cretaceous period could have only been possible if carbon dioxide levels were much higher than today, so this discovery could give an insight into the future environmental implications of increased carbon dioxide levels in the near future.