Effects of drought and litter types on litter decomposition in desert-oasis ecotone

Plant litter is a crucial source for soil fertility and the soil organic carbon pool, with its decomposition process significantly influenced by both climate conditions and the quality of the litter itself. Litter from different organs of the same plant often exhibits varying quality traits. However, information on how litter decomposition responds to drought and various plant organs within desert ecosystems is relatively scarce. In this study, we analyzed the impacts of litter input on soil stoichiometric characteristics, enzyme activity, and microbial community structure under different drought conditions through decomposition experiments (lasting 360 days) of litter from two types of desert plants (Suaeda salsa and Nitraria tangutorum) with various organs (root, stem, leaf), subjected to three levels of natural drought (gravimetric soil moisture at W1: 7.1 %, W2: 4.1 %, W3: 1.8 %). The results indicate that: (i) There are no significant differences in the mass loss of litter across the drought gradients in desert ecosystem. The initial chemical characteristics of litter (especially phosphorus) and the types of litter organs are the main factors influencing litter decomposition. (ii) The mixing of litter (mixing of identical organs) did not promote decomposition but increased nitrogen loss (p < 0.05), which was suppressed by aridity; mixing of litter also enhanced the effectiveness of soil nutrients. (iii) Litter decomposition increased soil nutrients and enzyme activity, improved soil nutrient conditions, and alleviated nitrogen and phosphorus limitations in the soil. (iv) Both aridity and litter organs are factors influencing the structure of soil microbial communities, but the different types of litter organs are the primary reason for differences in soil microbial community composition, with a greater impact on fungal communities than on bacterial ones. In soil treated with root litter, the fungal community was predominantly composed of Ascomycetes (relative abundance >99 %), while the leaf and stem litters were dominated by Ascomycetes (relative abundance 56.1–98.7 %) and Basidiomycetes (relative abundance 0.8–43.9 %). These results suggest that in desert ecosystems, litter primarily influences soil nutrient cycling through its own nutrient content and organs.