Categories
ecosystem Environment

What does a pond do?

A small container pond full of Azolla plants

What comes to your mind when you hear of a pond?

The word ‘pond’ refers to a body of water that is usually shallow (no more than 2m deep) and smaller than a lake. Unlike a stream or a river, a pond is enclosed. Therefore, pond water is always stagnant. Natural ponds are filled by rainwater or underground springs and there are also man-made ponds.

Despite its small size, a pond plays an important role in maintaining ecosystem functions and supporting the biodiversity of an area. A pond is home to aquatic animals like shrimps and fishes, and smaller wildlife like beetles, water striders, and snails. It also attracts water-loving creatures such as dragonflies, damselflies, frogs and toads. These animals lay their eggs in the pond, where their young hatch and mature.

Many pond animals feed on debris or fresh organic materials like leaves of plants. Some predatory pond wildlife prey on other smaller animals such as tadpoles and insect larvae. Terrestrial animals like birds will also visit a pond for drinking or bathing.

A dragonfly preys on other insects such as mosquitoes. Photo by Siti Syuhada

Aside from animals, there are various plants that grow in and around a pond. These plants are good for the pond. For example, the mosquito ferns (Azolla sp.) and the Mexican sword plant (Echinodorus palifolius). They absorb nutrients from pond water or sediment. In turn, these water plants supply oxygen to the pond, inhibit algae growth, purify pond water and provide food, shade and hiding places for wildlife.

There are also many other pond plants, categorised according to their growing zone. Plants that grow at the edge of pond are known as marginal plants. The floating plants, for example, duckweed, have tiny roots that absorb nutrients directly from water. Some deep water plants such as water lilies have leaves on the water surface and roots that are buried in the mud at the bottom of the pond. There are also submerged plants that are completely under water, like the Indian swamp weed (Hygrophila polysperma), but they do need some exposed surfaces of pond to receive sunlight and carry out photosynthesis.

Floating leaves and flower of water lily. Photo by Goh Shang Ming

There is so much going on in ponds. The next time you find a pond, take a closer look to see all the life it can hold.

Categories
ecosystem

Saving the Underground Farmers: Soil Ecosystems

Have you ever noticed the earth that you step on?

It is where we get materials essential to our survival. It is soil that supports the growth of plants, the producers of the food chain and the sources of fibre, fodder, and fuel.

At first look, it seems static and lifeless. In fact, soil hosts millions of life forms including bacteria, fungi, insects and other invertebrates, that all interact and perform complex activities. Some of these consume other life forms, others compete for space and resources, and certain organisms form collaborative relationships to access resources.

image of earthworm and soil
Earthworms are important members of the underground soil community affecting physical structure of soil

Underground life forms collectively form the soil biota and continuously re-construct the soil environment. These underground farmers are important to ensure healthy development of a plant, as the roots of the plant are a part of the soil ecosystem.  

The Mutualistic Relationships between Plants, Soil Microbes and Fungi

The underground parts of plants carry out nutrient and water uptake from the soil. The root system of a plant is involved in plant-microbe interaction whereby the plant provides carbons and shelter to the microscopic soil organisms (microbes). The microbes in turn supply minerals and trace elements in a modified form that can be used by the plant.

An example of such interaction is that of legume plants (peas, beans) and nitrogen-fixing bacteria. The bacteria in the soil convert nitrogen from the air into a form that legume roots can absorb from the soil.

Plants also develop symbiotic associations with soil fungi, that is, the relationship benefits both the plants and the fungi. These fungi reside near to or within the root cells of the plants.

Soil fungi use the organic nutrients and sugars that are produced by the plants. In return, they benefit plants by improving the plants’ ability to absorb nutrients and water, and their resistance to unfavourable conditions like pollution and diseases.  

The Alteration of Soil Structure and Composition

Over recent decades, large-scale industrial farming and land conversion have resulted in great change of soil structure and composition. The clearing of trees, shrubs and grasses, the digging and overturning of topsoil using machinery, as well as application of chemical insecticides, herbicides and fertilisers have had disastrous impacts on the underground food web.

The soil environment has become less conducive for the organisms to survive. The soil microbial communities lose connection with plant roots that provide carbons and shelter, and in turn the plants’ capacity for taking up water and nutrients declines. The soil ecosystem is losing its viability and robustness. 

Promoting healthy soil ecosystems

In order to revive the fertility of soil, we need to bring back the carbon to the soil. This is important for ensuring food security and sustainability of agricultural activities.  Here are two ways we can do this:

  • Plant different varieties of plants–each plant variety releases a unique set of biological compounds to the surrounding of its root system, and signals different underground microbe community and fungi. The greater the plant variety, the greater the variety in soil microorganisms which improves soil water-retention capacity and nutrient availability.
    Besides soil improvement, more plant varieties result in a greater variety of insects, including predatory insects that feed on pests. The predators help control pest numbers and thus reduce physical damage to the crop plants. 
Soil ecosystem consists of life forms that live within the soil but it also provides food to above-ground organisms
Image credit: USDA (CC-0)
  • Limit the use of chemical fertilizers—The application of NPK fertiliser has to be reduced, so that soil microbial communities have the chance to thrive and re-connect with the plant roots. Instead of relying on chemical input, plants have to derive these essential elements from the underground microbial communities and in return, channel their carbons to the soil. The increase of soil carbon would boost the soil communities, improve nitrogen uptake and also help maintain the structure of soil.  The removal of excess fertiliser reduces the formation of nitrous oxide (a greenhouse gas) in waterlogged or compacted soil.

Summary

If we understand soil and the life it teems with, we can grow healthier plants and do so in a sustainable manner. We can avoid the excessive chemical and water use that is a growing concern.

Plant growth is influenced by the health of the soil and it also influences life around it and beneath it. Having more plants of different varieties helps conserve underground ecosystems. As the soil carbon (provided by plants) increases, the soil microbial community is revived, and the underground farmers can improve the structure and composition of the soil to support more plants.

Reference:

Jones, C. (2018). Light Farming: Restoring carbon, organic nitrogen and biodiversity to agricultural soils . Retrieved from Amazing Carbon Web site: http://amazingcarbon.com/JONES-LightFarmingFINAL(2018).pdf