High night‐time humidity and dissolved organic carbon content support rapid decomposition of standing litter in a semi‐arid landscape

Abstract

Summary Litter in arid and semi‐arid ecosystems usually exhibits a prolonged standing dead phase after senescence; however, we know little about the ways in which abiotic and microbial processes affect standing litter decomposition. We conducted a 26‐month in situ decomposition experiment in a steppe to investigate the potential mechanisms governing the decomposition of standing litter, and a 192‐day laboratory incubation experiment to further explore the impacts of the standing dead stage on the subsequent litter decomposition and soil organic carbon (SOC) formation after the litter falls to the soil surface. Compared with soil surface litter, standing litter has higher dissolved organic carbon (DOC) content. Standing litter also experienced higher night‐time relative humidity on its surface, which enhanced litter moisture content. The higher DOC concentration, combined with the greater night‐time moisture content, stimulated more microbial activity in standing litter. The decomposition rate (k) of standing litter was 92% higher than that of soil surface litter. Moreover, the standing phase conditioned the litter, leading to more rapid decomposition after the litter fell to the soil surface, and increasing the efficiency with which the litter formed SOC. We conclude that the long‐neglected standing phase greatly determines litter decomposition and soil carbon storage in semi‐arid regions. Accounting for standing litter decomposition is critical for accurately simulating carbon turnover in arid and semi‐arid ecosystems. A http://onlinelibrary.wiley.com/doi/10.1111/1365-2435.12854/suppinfo is available for this article.

Long‐term deepened snow cover alters litter layer turnover rate in temperate steppes

“…Moreover, soil moisture was indeed negatively correlated with LRT (Figure ). Microbial activity in grasslands are often stimulated by the increased soil moisture (McHugh, Morrissey, Reed, Hungate, & Schwartz, ; Wang, Liu, et al, ), it is therefore reasonable to expect that the higher soil moisture in the dry steppe should increase microbial biomass and activity and further accelerate litter turnover, as indicated in some previous studies (Dirks, Navon, Kanas, Dumbur, & Grünzweig, ; Gliksman et al, ; Jacobson et al, ). However, deepened snow in the dry steppe did not alter the residence time of the litter layer (Figure ), indicating that there were some other factors that inhabited the litter turnover process.…”

Schrenk spruce leaf litter decomposition varies with snow depth in the Tianshan Mountains

“…Snow cover can significantly change the land surface temperature under snow. Thus, the lower rates were probably due to the lower land surface temperatures (− 15-5 °C vs. 5-20 °C) and the condensation of soil water under low temperatures, which might therefore limit the microbial activities and restrict the decomposition of litter during the snow cover period [33][34][35] . Significantly higher lignin concentrations were observed in the pregrowing season and middle of the growing season than in the freeze-thaw period and deep-freeze period.…”

Linkages between stratospheric ozone, UV radiation and climate change and their implications for terrestrial ecosystems

“…270 However, the interaction of moisture and photodegradation has recently been garnering attention. 274,276,280 In moist, forested ecosystems, the amount of solar radiation reaching litter through the canopy can alter decomposition rates. 281 Different types and densities of canopy affect both the amount of radiation reaching ground level and its spectral composition.…”

“…In habitats where standing dead litter remains on the plant, this will present a greater surface area exposed to sunlight than situations where litter falls to the ground becoming easily mixed with soil which then reduces photodegradation. 273,276,[288][289][290] The structure and biochemical composition of litter produced by different plant forms plays a significant role in determining the underlying rate of decomposition. Hence litter with high lignin content may decompose slowly and be most affected by direct photochemical degradation.…”