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

Abstract

Root decomposition often decreases with increasing root diameter, but this relationship is affected by other factors, including the microclimate and land use. The mechanisms that underlie these interactions are unclear. We performed an Artemisia halodendron root decomposition litterbag experiment using fine (<2 mm), medium (2–5 mm) and coarse (>5 mm) roots. We used the same incubation duration (356 days) with five starting dates (May, June, July, October and September) in fenced (grazing exclusion) and grazed plots. Root samples installed in May decomposed faster than those installed in September, and roots decomposed faster in fenced plots than in grazed plots. Root decomposition was the highest for fine roots installed in any month, and medium roots decomposed faster than coarse roots with installation in all the months except May and July. Grazing exclusion and starting incubation time both interacted with root diameter. Root decomposition for a given diameter did not differ significantly between fenced and grazed plots; however, in both land uses, root decomposition decreased significantly with increasing root diameter. Microclimate, especially precipitation, differed among the starting dates, and precipitation patterns (especially in the first growing season) significantly (p < .01) affected coarse root decomposition in the fenced plots. In summary, root decomposition was significantly (p < .01) affected by root diameter. This effect was altered by grazing exclusion and by starting dates. These results highlight the importance of the starting date for root decomposition in a semiarid grassland, suggesting this date should be accounted for in future studies of root decomposition.

Mowing Facilitated Shoot and Root Litter Decomposition Compared with Grazing

“…This brought about higher plant coverage and litter biomass during the growing season following mowing compared to grazing. Less canopy following reduced plant coverage and litter accumulation provided less shade in grazing plots, which increased soil temperature and induced lower soil moisture by evaporation, as supported by our results and previous research [ 22 , 45 ]. Moreover, mammal trampling increased soil bulk density, which might induce soil compaction and salinization, restricting microbial activity and litter decomposition [ 21 ].…”

“…Any visible fresh vegetation soil particles adhering to the shoot or root were removed, and the remaining materials were over-dried at 80 °C for 48 h and weighed. The dry matter loss ratios of litter and root were calculated according to the followed equation [ 45 ]. Mass loss (%) = ( M 0 − M t )/ M 0 × 100 where M 0 is the initial weight and M t is the residual amount after the decomposition time of t .…”

Fine root decomposition in forest ecosystems: an ecological perspective

“…The primary cause of root decomposition is difference in soil water and temperature differences during the initial decomposition stage. Although there are slight differences between fine root decomposition rates of A. halodendron at different starting times, other factors, such as variability in soil moisture and its interaction with soil temperature, are likely to have a greater impact on the root decomposition process overall (Luo et al, 2016;Luo et al, 2020). Consistent with those findings, the presence of mycelia hastens fine root decomposition (Pritsch and Garbaye, 2011).…”