Abstract
Simple SummaryNutrient cycling in terrestrial ecosystems requires moisture. Deserts are characterized by low precipitation and extreme surface temperature that limit biological activity. Attempts to resolve how nutrients recycle despite these constraints were focused primarily on abiotic factors. We suggest that macro-arthropods may play a disproportionally large role in resolving this conundrum. Macro-arthropods are prevalent in deserts and many of them are burrowing detritivores that can remain active during long dry periods. Desert arthropods process and transport plant litter nutrients belowground, where the conditions are favorable for decomposer activity. Consequently, arthropods may accelerate the recycling rate of plant litter nutrients to inorganic nutrients that become available for plant use. This generates a vertical nutrient recycling loop (VRL) that may also assist in explaining how desert plants receive nutrients when the shallow soil is dry. Macro-arthropods may also regulate the spatiotemporal distribution of nutrients by transporting them between patches and across ecosystems. Burrowing activity that alters the desert microtopography and reduces soil salinity may contribute further to creating hotspots of productivity and biological diversity in the otherwise poor desert environment. We conclude that macro-arthropods may play a key role in explaining how desert ecosystems function, and that better understanding of this unique role may assist combating desertification and restoring degraded arid lands.Nutrient dynamics in most terrestrial ecosystems are regulated by moisture-dependent processes. In drylands, nutrient dynamics are often weakly associated with annual precipitation, suggesting that other factors are involved. In recent years, the majority of research on this topic focused on abiotic factors. We provide an arthropod-centric framework that aims to refocus research attention back on the fundamental role that macro-arthropods may play in regulating dryland nutrient dynamics. Macro-arthropods are prevalent in drylands and include many detritivores and burrowing taxa that remain active during long dry periods. Macro-arthropods consume and process large quantities of plant detritus and transport these nutrients to the decomposer haven within their climatically buffered and nutritionally enriched burrows. Consequently, arthropods may accelerate mineralization rates and generate a vertical nutrient recycling loop (VRL) that may assist in explaining the dryland decomposition conundrum, and how desert plants receive their nutrients when the shallow soil is dry. The burrowing activity of arthropods and the transportation of subterranean soil to the surface may alter the desert microtopography and promote desalinization, reducing resource leakage and enhancing productivity and species diversity. We conclude that these fundamental roles and the arthropods’ contribution to nutrient transportation and nitrogen fixation makes them key regulators of nutrient dynamics in drylands.
Highlights
Drylands constitute up to 45% of the Earth’s terrestrial surface [1] but in comparison to other biomes remain poorly understood
A comprehensive meta-analysis that explored the effect of soil fauna exclusion on litter decomposition questions these findings [26]. They found that exclusion of soil fauna reduces litter mass loss by 35% globally, but only by 18% when focusing on drylands. We believe that these findings do not reflect the actual regulatory role that macro-arthropods play in hot deserts
Our understanding of nutrient dynamics in terrestrial systems relies heavily on studies from mesic systems. Attempts to apply this understanding to water-limited systems were proven insufficient. To bridge this conceptual discrepancy, ecologists put effort predominantly in revealing whether abiotic factors in the harsh desert surface may partially compensate for the lack of water
Summary
Drylands constitute up to 45% of the Earth’s terrestrial surface [1] but in comparison to other biomes remain poorly understood. In this important paper and many of the studies that followed, the researchers used litter bags or cages covered with mesh that exclude macrofauna and prevent litter redistribution, to assess litter mass loss in the presence or absence of focal abiotic factors These studies offer strong experimental evidence that photodegradation, thermal degradation, and alternative sources of moisture, such as fog, dew, and atmospheric water vapor, can assist in explaining the unexpectedly high decomposition rate of exposed plant litter [14,15,16]. We aim to rip the fine mesh of the litter bags and inspire researchers to refocus their attention back to the potentially important regulatory role that macro-arthropods play in arid ecosystems
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