Litter Decomposition in a Semiarid Dune Grassland: Neutral Effect of Water Supply and Inhibitory Effect of Nitrogen Addition

Abstract

BackgroundThe decomposition of plant material in arid ecosystems is considered to be substantially controlled by water and N availability. The responses of litter decomposition to external N and water, however, remain controversial, and the interactive effects of supplementary N and water also have been largely unexamined.Methodology/Principal FindingsA 3.5-year field experiment with supplementary nitrogen and water was conducted to assess the effects of N and water addition on mass loss and nitrogen release in leaves and fine roots of three dominant plant species (i.e., Artemisia halondendron, Setaria viridis, and Phragmites australis) with contrasting substrate chemistry (e.g. N concentration, lignin content in this study) in a desertified dune grassland of Inner Mongolia, China. The treatments included N addition, water addition, combination of N and water, and an untreated control. The decomposition rate in both leaves and roots was related to the initial litter N and lignin concentrations of the three species. However, litter quality did not explain the slower mass loss in roots than in leaves in the present study, and thus warrant further research. Nitrogen addition, either alone or in combination with water, significantly inhibited dry mass loss and N release in the leaves and roots of the three species, whereas water input had little effect on the decomposition of leaf litter and fine roots, suggesting that there was no interactive effect of supplementary N and water on litter decomposition in this system. Furthermore, our results clearly indicate that the inhibitory effects of external N on dry mass loss and nitrogen release are relatively strong in high-lignin litter compared with low-lignin litter.Conclusion/SignificanceThese findings suggest that increasing precipitation hardly facilitates ecosystem carbon turnover but atmospheric N deposition can enhance carbon sequestration and nitrogen retention in desertified dune grasslands of northern China. Additionally, litter quality of plant species should be considered when modelling the carbon cycle and nutrient dynamics of this system.

Grazing exclusion altered the effect of plant root diameter on decomposition rates in a semiarid grassland ecosystem, northeastern China

“…This is consistent with our result for the root samples that were incubated from September, which decomposed significantly more slowly than the other samples (Figure 2b). Our previous research also supported the importance of the starting date on litter decomposition, as the decomposition rate of fine roots of A. halodendron (collected in the same place and with similar quality) was higher when incubation started in July (Luo et al, ) than when it started in early April (Li et al, ). This importance of the starting date on litter decomposition was also demonstrated by Li, Deng, et al () and Paudel et al ().…”

“…Root diameter is an important controlling factor for decomposition because smaller roots are decomposed faster than larger roots due to differences in the litter quality (i.e., the nitrogen [N] concentration, C/N ratio and lignin content). This diameter effect has been demonstrated both in site‐specific observations (Li et al, ; Luo et al, ; Mao, Zeng, & Li, ; Zhuang et al, ) and in global surveys (Silver & Miya, ; Zhang & Wang, ). However, the relationship between root diameter and decomposition is ambiguous.…”

“…A field study in a subtropical forest with different incubation starting dates found that the mass remaining and the decomposition rate constant ( k ) differed significantly among starting dates, and that the litter decomposition rate was significantly correlated with temperature and precipitation during the early stage of decomposition but not during the later stage (Li, Deng, Zhou, & Zhang, ). In a semiarid degraded sandy grassland, our previous study showed that for root samples of Artemisia halodendron collected from the same place and with similar quality, mass loss of fine roots was less than 40% after 2 years' decomposition which started in April 2010 (Li et al, ). This contrasts with rates of 39.8 and 70.3% after 53 and 381 days of incubation, respectively, when incubation started on July 15 (Luo et al, ).…”

Effects of experimental nitrogen enrichment on soil properties and litter decomposition in a Neotropical savanna

“…Much of what is known about the responses of ecosystems to soil nitrogen enrichment, including how enrichment influences litter decomposition, is the result of fertilisation experiments conducted in the temperate zone (Carreiro et al 2000;Gong et al 2015;Hobbie 2008;Li et al 2016). These experiments have found variable effects of N addition on decomposition (Knorr et al 2005), perhaps due in part to the amount of N added or variation in litter qualityespecially the amount of nitrogen and lignin it contains.…”

“…2015; Hobbie 2008; Li et al . 2016). These experiments have found variable effects of N addition on decomposition (Knorr et al .…”