Hypothetical climate dependence of litter decomposition by microorganisms and mesofauna (dotted orange curve), by macrofauna (grey – dash), and by the whole decomposer community (maroon - solid).

(A) Locations and landscapes of the seven experimental sites across a precipitation gradient from 22 to 526 mm mean annual precipitation (MAP). (B) A block of three litter baskets in the Sayeret Shaked site. Macro-basket in front, meso-basket on the right and micro-basket on the left. The precipitation map courtesy of the Hebrew University GIS center.

Properties of the seven experimental sites

Litter removal rate (mean ± se) from baskets with different mesh sizes across sites and seasons. Asterisks represent significant differences between mesh sizes within site and season: * P-value<0.05, **P-value<0.01, ***P-value<0.001. NS – Nahal Shita; MS – Meishar; AV – Avdat; SS – Sayeret Shaked; HS – Havat Shikmim; BG – Bet Guvrin; RH – Ramat Hanadiv. Negative values may represent cases in which physical cleaning and ash correction failed to correct for all dust accumulation on the litter or cases in which exogenous litter may have penetrated the baskets. Our findings were not sensitive to these negative values.

Contribution of different organism size classes to litter removal (mean ± se) across the precipitation gradient during summer, winter and both seasons combined. Macrofaunal contribution was calculated as the within-block difference between macro- and meso-baskets; mesofaunal contribution as the difference between meso- and micro-baskets; microbial and whole community contributions represent litter removal rates in the micro- and macro-baskets, respectively. Curves were fitted to data using local estimation scatterplot smoothing (LOESS). Negative values may represent cases in which physical cleaning and ash correction failed to correct for all dust accumulation on the litter or cases in which exogenous litter may have penetrated the baskets. Our findings were not sensitive to these negative values.

Results of a full-factorial analysis of variance in litter removal rate across mesh sizes, experimental sites and seasons.

Macro-decomposer abundance, biomass and alpha morphospecies richness across the precipitation gradient in the two experimental seasons (mean ± se). Values are averaged across traps and divided by the number of trapping days. NS – Nahal Shita; MS – Meishar; AV – Avdat; SS – Sayeret Shaked; HS – Havat Shikmim; BG – Bet Guvrin; RH – Ramat Hanadiv.

(A) and (B) Graphical representation of the first two axes of a principal coordinate analysis on the macro-decomposer assemblage data. Colors represent experimental sites in A and seasons in B. Arrows represent taxonomic group scores fitted onto the PCoA ordination. (C) Distribution of abundance, biomass and morphospecies richness among macro-decomposer taxonomic groups in each site across the aridity gradient. NS – Nahal Shita; MS – Meishar; AV – Avdat; SS – Sayeret Shaked; HS – Havat Shikmim; BG – Bet Guvrin; RH – Ramat Hanadiv. Color codes (left to right in panel C): grey – Zygentoma, burgundy – termites, olive green – millipedes, turquoise – woodlice, pink – snails and slugs, purple – earthworms, dark green – crickets, pale yellow – bristletails, red – beetles, pale blue – ants.