Earthworms, ants, termites: The real engineers of the ecosystem

The contribution of home gardens in the preservation of biodiversity, economics and human health prompted a multidisciplinary group at the South Border College (Ecosur) in Mexico to work on a project in Tabasco, a south state of the country, with the aim to improve the production and environmental management of these plantations. Credit: Image courtesy of Investigación y Desarrollo

The contribution of home gardens in the preservation of biodiversity, economics and human health prompted a multidisciplinary group at the South Border College (Ecosur) in Mexico to work on a project in Tabasco, a south state of the country, with the aim to improve the production and environmental management of these plantations.

Although the research was conducted from different perspectives, head of research Esperanza Huerta Lwanga focused on the study of soil invertebrates because they are indicators of its quality.

"These organisms fulfill various functions,like allowing the soil to absorb processed organic matter such as leaves, wood, trunks and branches and with this nourishing crops; they also maintain an ecological balance capable of preventing the invasion of pests and provide greater fertility without using chemicals. This happens when growing different types of plants, allowing the existence of a wide variety of soil invertebrates" the researcher explains.

The project, which began in 2009 and was funded by the Ministry of Energy, Natural Resources and Environmental Protection (SERNAPAM), arises because home gardens are places where there is a wealth of soil. In total, the research team worked in 50 home gardens located in different physiographic regions of the state: mountains, coast, floodplain and hillocks.

"During the fieldwork I realized that the orchards whose owners had family harmony, were characterized by a rich vegetation and greater diversity of soil invertebrates was found. However, in other orchards we observed garbage instead vegetation and organisms, revealing a gap between people and nature, " relates Huerta Lwanga.

An important finding of this project was when the researcher found a anecic earthworm, initially thought to be a new species, however, it was only a new entry in the state of Tabasco. "Such organism is characterized by its vertical movements, thereby creating tunnels, helping to integrate the organic matter in the soil, aerating it and forming its structure," the researcher says.

Other species were also identified, like earthworms, ants, termites, centipedes, beetles, grasshoppers, cockroaches and woodlice, which may also be called "ecosystem engineers" (specifically earthworms, termites and some ants) because their activities modify the soil, enriching its productivity.

According to the researcher, it is important to note that the presence of such organisms does not mean that the garden is infested with pests. "If you let me live there, they fulfill their tasks and at the same time control their population because the variety of invertebrates generates food chains."

The pest problem, she says, appears when the land is handled as a monoculture. In these cases only one type of organisms thrives and rapidly increases in number and , because nobody eats them, they become a threat to the plantations.

The research results revealed that the coastal region was the one with more garbage, followed by the hillocks. "In the mountains we found healthy vegetation and a great variety of crops, high diversity of invertebrates and greater earthworm biomass, which was estimated at more than 33 grams per square meter," highlights Huerta Lwanga.

That amount is important because according to previous studies it was established that if biomass is equal or greater than 30 grams per square meter germination induction and plant growth are achieved.

Additionally, this project included environmental education, which was given by mini-workshops and training in the production of vermi-compost.

"At Ecosur, we designed a box for composting, which is equiped with a small mill and worms, where we place the fresh waste to be processed. A device like this was given to all farmers, but was only accepted by 47 percent of them," she sadly concludes.

Source: Investigación y Desarrollo

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Live fast, die young: Soil microbes in a warmer world

Aerial view of the Northern Minnesota landscape including numerous conifer peatlands, deciduous uplands and lakes. Credit: USDA Forest Service Northern Research Station

Warmer temperatures shorten the lifespan of soil microbes and this may affect soil carbon storage, according to a new NSF-funded study published in Nature Climate Change this week.

A research team led by Shannon Hagerty and Paul Dijkstra from Northern Arizona University measured two key characteristics of soil microbes that determine their role in the soil carbon cycle: how efficiently they use carbon to grow and how long they live. "Higher temperatures make microbes grow faster, but they also die faster," said Hagerty, who conducted the research as part of her master's degree and was lead author on the study.

Soil microbes consume organic carbon compounds in soil, use some of it to make more microbes and release the rest to the atmosphere as carbon dioxide. The efficiency with which microbes use their food to make new microbes affects how much carbon remains in soil, and how much is released back to the atmosphere. The accepted idea before this study was that microbes would become less efficient at warmer temperatures.

The scientists incubated soil from a peatland and a forest in Minnesota at different temperatures and measured the efficiency with which microbes grew. They used a new method to measure microbial efficiency: they added small amounts of sugar and tracked how individual atoms in this sugar were turned into carbon dioxide.

"Microbes process sugars in similar ways as we do," says Paul Dijkstra. "We know very well how these processes work in laboratory studies, and can predict which carbon atoms in sugar molecules end up as carbon dioxide, and which are used to build new microbes. We applied this knowledge to the microbes living in soil."

The researchers found, contrary to expectation, that temperature had no effect on how microbes utilized their food, but instead boosted microbial death. "We don't yet know why microbes are dying faster at higher temperatures. Maybe they are eaten by nematodes or mites, or they die because of viruses," said Hagerty. "We need to know more about how temperature affects microbial death."

To explore what these new findings could mean for soil carbon storage in a warming world, the team compared output from a soil model that includes the effect of temperature on microbial lifespan to models unaffected by temperature change. "Models are used to predict how soil processes change, for example, in response to climate change," said Steve Allison, coauthor from the University of California, Irvine. "If we want to predict the future correctly, we'd better use models that accurately describe these microbial processes."

Including a temperature-dependent lifespan to the model increased the amount of carbon retained in soils at warmer temperatures compared to estimates from traditional models. The study concludes that incorporating this new insight into soil models will improve our understanding of how soils influence atmospheric carbon dioxide levels and global climate.

Does this mean that with climate change, more carbon will stay in the soil? "Too early to tell," said Bruce Hungate, Director of the Center for Ecosystem Science and Society at NAU. 

"The results suggest that the biochemistry of the microbes remains the same with warmer temperature, but that predation and death become more important. This laboratory study is just the first step, identifying a potential mechanism. Now we need to study how, in the real world, and in the long-term, the processes of biochemical efficiency and lifespan will change. And nobody has done that yet."

Source: Northern Arizona University

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Impact of climate change on the soil ecosystem

The Basque Institute for Agricultural Research and Development NEIKER-Tecnalia has had a Microbial Observatory in the Ordesa and Monte Perdido National Nature Reserve (Huesca Pyrenees) since 2011. Its purpose is to evaluate the impact of climate change on the ecosystems of the soil by monitoring its microbial properties over time. Credit: Image courtesy of Basque Research

The Basque Institute for Agricultural Research and Development NEIKER-Tecnalia has had a Microbial Observatory in the Ordesa and Monte Perdido National Nature Reserve (Huesca Pyrenees) since 2011. Its purpose is to evaluate the impact of climate change on the ecosystems of the soil by monitoring its microbial properties over time. The research areas are located at altitudes of between 1,500 and 2,600 metres, which provides a broad range of different climate conditions and makes it possible to observe how the altitude affects the properties of the soil and the micro-organisms living in it. Preliminary results indicate that microbial properties are highly dependent on the physical and chemical properties of the soil on a small scale and on the environmental conditions existing at the moment when the samples are gathered.

To conduct this research, NEIKER-Tecnalia is using the most advanced techniques in the matter of molecular biology, which have revolutionised microbial ecology. Specifically, massive sequencing analyses are being carried out right now; they allow a large number of genes to be sequenced and identified within a short space of time. The genetic sequencing of the subterranean biosphere is seeking to gain a better understanding of the structure and function of the microbial communities across the altitude gradient.

NEIKER-Tecnalia's Microbial Observatory will contribute towards improving the current understanding of the effects of climate change on soil microbial communities and associated ecological processes. The alpine area where it is located is particularly suitable for a climate change observatory. Firstly, it is a remote spot relatively isolated from direct anthropogenic impacts, which means that global effects like climate change can be clearly perceived without the interference of more local environmental factors. Secondly, the altitude gradients that exist in the mountains in turn create clearly marked climate gradients within short distances; in other words, different climate conditions can be found at different altitudes.

Micro-organisms adapt more quickly than plants and macro-organisms

Micro-organisms adapt more quickly to changes than plants or other macro-organisms, which means they are ideal bioindicators of the impact of sources of environmental stress on the functioning of ecosystems. It is very important to have a record of the alterations gradually occurring in the soil ecosystem as a result of climate change to be able to more accurately predict what future scenarios are going to be in store. It is important to stress that the soil is our most important resource; it is the basis of the terrestrial ecosystem and 95% of our food comes directly or indirectly from it.

The role of micro-organisms in relation to the functioning of the soil ecosystem is fundamental. The soil, which has been traditionally regarded as an inanimate item made up of minerals and chemical substances, contains a myriad of micro-organisms that are responsible for many of its vital functions and, consequently, its health. These functions include the decomposition and recycling of nutrients from dead plant and animal tissue, nitrogen fixing, the maintaining of soil structure and the elimination of contaminants.
It can be predicted that, in the long term, climate change will cause the biota of mountain soil to migrate towards higher altitudes in the quest for the optimum bioclimatic environment. The problem is that this migration has a limit, which is the summit of the mountain, beyond which no migration or escape is possible.

Source:  Basque Research

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The Loss of biodiversity limits toxin degradation

You might not think of microbes when you consider biodiversity, but it turns out that even a moderate loss of less than 5% of soil microbes may compromise some key ecosystem functions and could lead to lower degradation of toxins in the environment.

Research published today in the SfAM journal, Environmental Microbiology, reports that without a rich diversity of soil bacteria, specialized functions such as the removal of pesticide residues are not as effective.

Dr Brajesh Singh of the University of Western Sydney led the work, he said "If the ability of the ecosystem to remove toxins from the environment is reduced, there will be higher toxicity risks in the environment and for non-target organisms, including humans, from agricultural chemicals. It is likely that these contaminants will remain at higher levels in surface and underground water, as well. It is vital to gain a better understanding of the extent to which soil bacteria are involved in the removal of contaminants."

The reasons for, and extent of, the decline in microbial diversity in agricultural soils is likely to be complex. The team has looked specifically at long-term heavy metal pollution where metals such as cadmium, zinc, and copper build up in the environment, usually as a result of industrial use. Another source is from digested sewage sludge, which is spread in agriculture fields to supply nutrients to crops and improve soil fertility; the sludge has historically contained some heavy metals, which can become concentrated in the soil.

Although the concentration of heavy metal used this study was higher than the current EU limit, this study has confirmed that long-term exposure to such contaminants does reduce the diversity of bacteria in the soil.

With the global population set to reach nine billion by 2050, we face a challenge to feed an extra two billion mouths using the same resources that we have at present. Crop losses to pests and disease account for a large percentage of under-production and so giving up pesticides will be difficult. Similarly, the use of sludge as a fertilizer is likely to become more prevalent. Research like this allows us to understand better how to use important agrichemicals and waste products in a sustainable way and so will contribute to future food and environmental security.

Source: Wiley

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