Abiotic effects

One of the most intriguing aspects of increased UV-B and its implications for ecosystems is the ability it has to break down living (or once living) tissue without the help of microbes.  As mentioned in the Effects on bacteria/fungi section, microbes drive the process of decomposition and are a major player in nutrient cycling.  What will happen if the breakdown of organic matter and re-introduction of nutrients to the system is actually increased?

This question is particularly applicable to dry ecosystems, where primary production and microbial activity are slow to start with. In these systems, even a small change in organic matter quality and quantity can cause significant alterations relative to the natural level that generally occurs. A recent study aimed to tease apart the effects of increased UV-B on dry versus wetter ecosystems.  They found that abiotic decomposition played a major role in breaking down leaf litter in dry systems where microbial activity tends to be limited However, they also found that in wetter systems the effects of UV-B actually decreased rates of decomposition due to the greater relative effect it had on slowing microbial breakdown of litter  (Smith et al., 2010).

Thus, the degree to which radiation might have an effect on a system is likely very dependent on the starting state of that ecosystem (environmental conditions, species present, rates of central processes, etc.).  In regions where decomposition is slow and tightly controlled, such as cold and/or dry systems, abiotically-driven decomposition (eg. from radiation) will likely have a profound impact on the cycling and availability of nutrients.


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