The brown-rot fungal wood decay resulted in higher concentrations of soil C and N and a greater increase in microbial necromass (i.e., 1.3- to 1.7-fold greater) than the white-rot fungal wood decay. The white-rot sets were accompanied by significant differences in the proportions of the bacterial residue index (muramic acid%) with soil depth; however, the brown-rot-associated soils showed complementary shifts, primarily in fungal necromass, across horizontal distances. Soil C and N concentrations were significantly correlated with fungal rather than bacterial necromass in the brown-rot systems. Our findings confirmed that the brown-rot fungi-dominated degradation of lignocellulosic residues resulted in a greater SOM buildup than the white-rot fungi-dominated degradation.
Comments and Questions 6 20 2017
My only experience with weed mat, was pulling one up, and finding stinky dead earth beneath
Now it sounds like this person’s plastic weed mat caused the soil below it to turn anaerobic due to either a lack of air penetrating the mat or retaining too much moisture which then excluded the air from entering the soil. When this happens the soil begins to anaerobically digest and produce alcohols, phenols, and gasses such as methane, the scent of sewer gas.
Not ideal plant growing conditions!
However there can be benefits when using plastic weed mat in the right conditions that does let air and water through, as the mat can help keep the soil moist, especially in drier regions. Weed mats can also warm or cool the soil depending on how much sunlight they absorb or reflect. They can also help prevent erosion. But the main reason people use it, is because the mats also reduce weed competition for plants planted into or near the weed mat. Reduced competition for water, sunlight, and for nutrients.
However the biggest problem with plastic weed mat when growing and assuming the correct mat was chosen for the conditions, is that if left on for extended periods, the soil often tends to breed plant pathogens. This happens when soils are not amended with a high carbon source such as plant leaf litter, plant exudates, or an organic mulch.
In soils that are kept moist and aerated and warm the microbiology and fauna become more active and will chomp through organic matter like there is no tomorrow. In doing so there is an increase in soil carbon respiration in the form of carbon dioxide and methane along with other gasses. This increase in respiration can actually help increase plant growth by providing carbon dioxide concentrated around the plant leaves. The increase in microbiological activity also increases nutrient cycling and plant available soil nutrients. However if the plants aren’t putting the carbon back into the soil via their roots, exudates, or plant litter when they die – then over the long term the soil community suffers.
When there is a lack of high carbon input that organic mulch provides to soil organisms, competition for that soil carbon increases. And the less soil carbon, the less complex organisms will survive. This is particularly important for fungi that rely on the carbon because they are made up of more carbon than other microbiology. Worse, the fungi that do survive the hostile conditions are often those that are plant predators able to fight for the carbon needed in order to survive because they now lack competition. As a result those predators infect plants and reduce yields or even kill them, and so gardeners and farmers search for solutions to their fungal problems in the form of fungicides. As a result fungi get a bad name. The same happens to nematodes.
However for short season plants like seasonal crops in Kevin’s example, this may not be much of a problem as the plant may be ready for harvest before the predators have overcome a plants defences, and he’s adding organic matter every year.
To conclude, when organic resources are plentiful, everyone’s happy and works in symbiosis, and when they’re not happy it’s war. Not quite extremophile Star Wars, but certainly localised Planet Wars, and eventually those wars include us higher order carbon beings in Human Wars that result from desertification and a lack of resources.
Plastic mulch is also plastic. Did you know that most sea salt already has microplastics in it after a little over 100 years of plastics use?
This study says that leaf litter was preferred by fungi and root litter by other microbes like bacteria and nematodes, and that herbivorous nematodes were controlled more by leaf litter than root litter.
Probably by the fungi catching the nematodes with lasso! Yeehaw.
It also suggests that cutting plants at the stems and just leaving the roots to feed soil microorganisms may increase nematodes over time, especially when nitrogen or phosphorus is added. Phosphorus is known to negatively impact on fungi populations, while nitrogen amendment can result in plants exuding less carbon from their roots that fungi and other soil microbes feed on, microbes that then fix nitrogen and make other nutrients bioavailable for the plant.
So, if you’re doing a no dig approach to gardening and leaving roots in place, mulch is a must. Whether that’s a carbon source in the form of leaves or a low phosphorus compost mulch or otherwise, basically think of the fungi!