An examination of leaf litter decomposition in various climatic environments reveals that larger invertebrates are the primary drivers of this process in hot and dry areas, particularly during warmer months. Research indicates that larger insects, including woodlice and beetles, significantly contribute to the breakdown of leaf litter in multiple habitats and throughout different seasons, comparable to the roles played by microbes and smaller invertebrates.
Research indicates that larger insects, such as woodlice and beetles, are as essential to leaf litter decomposition in various habitats and seasons as microbes and smaller invertebrates.
The study, released today as a final Version of Record following its earlier appearance as a Reviewed Preprint in eLife, has been characterized by editors as a significant research effort that enhances our understanding of how soil invertebrates of different sizes influence the rate of leaf litter decomposition. The authors present strong evidence that the collective impact of all decomposers on decomposition rates shows that larger invertebrates are more active in summer, while microorganisms lead in winter, ultimately resulting in similar decomposition levels across locations with varying aridity. This research will be valuable to ecologists studying carbon cycles in relation to global warming.
Leaf litter decomposition is vital for the cycling of elements such as carbon within terrestrial ecosystems. Factors such as climate, leaf litter quality, and the types and numbers of decomposer organisms all influence decomposition rates.
“There is evidence that decomposition happens more rapidly in warm and wet conditions, leading to the belief that microorganisms are the primary agents in this process, often overlooking the emerging recognition of the role animals play,” says co-lead author Viraj Torsekar, who was then a postdoctoral scholar at The Alexander Silberman Institute of Life Sciences at The Hebrew University of Jerusalem, Israel, and is now an Assistant Professor at GITAM University, Visakhapatnam, India. “We theorized that the ability of larger creatures like termites and beetles to withstand arid environments might balance the impact of smaller decomposers, resulting in similar decomposition rates across various climatic extremes.”
To explore this, the researchers set up plant litter baskets with three different mesh sizes at seven locations in Israel, ranging from hyper-arid regions with minimal rainfall (average annual rainfall of 22 mm) to areas with cooler, wetter Mediterranean climates (average annual rainfall of 526 mm). The three sizes of baskets allowed for access to different decomposers: ‘micro’ (only microorganisms), ‘meso’ (microorganisms and invertebrates smaller than 2 mm, like springtails), and ‘macro’ (large enough for larger invertebrates from 2 mm to 2 cm, including termites, woodlice, and beetles). The baskets were placed for varying durations during both the hot, dry summer and the cold, wetter winter, while pitfall traps were employed to analyze the composition and abundance of the macrofauna.
The findings revealed that the rate of litter removal varied by season, location, and basket mesh size. Overall, microbial decomposition was low during summer and increased in wetter winter conditions. In contrast, meso-faunal activity was moderate year-round and peaked in semi-arid areas. Macro-faunal decomposition (by termites, woodlice, and beetles) contributed little in winter but became the key factor in summer. Data from pitfall traps indicated that macro-faunal diversity and numbers were greatest in arid regions, where their decomposition rates were also highest. The authors noted that larger invertebrates effectively manage hot and dry conditions by moving into cooler, more humid areas as necessary.
The question of why litter decomposition in arid regions occurs faster than anticipated has puzzled researchers for 50 years, termed ‘the desert decomposition conundrum.’ Previous hypotheses suggested that factors like light, heat, fog, dew, or humidity might assist in litter breakdown. However, this study supports a long-suggested yet often neglected idea—that it’s the macro-faunal decomposers that primarily handle leaf litter decomposition in desert regions.
“Our results reveal that the contrasting climate preferences of micro- and macro-faunal decomposers have led to comparable or even higher annual decomposition rates in arid regions compared to wetter areas,” states senior author Dror Hawlena, a Professor at The Alexander Silberman Institute of Life Sciences at The Hebrew University of Jerusalem.
“This implies that the differing climate preferences among decomposer sizes, rather than abiotic variables, account for the gap between traditional decomposition models and observed rates in drylands, offering a plausible answer to the dryland decomposition conundrum,” concludes co-lead author Nevo Sagi, who was a PhD student at The Hebrew University of Jerusalem at the time and is now a postdoctoral scholar at the University of Texas at Austin, US. “Comprehending the mechanisms governing decomposition in drylands is crucial for preserving and restoring essential ecosystem functions in these expanding areas and enhancing our understanding of global processes like carbon cycling.”
