Mean age of carbon in fine roots from temperate forests and grasslands with different management

[摘要] Fine roots are the most dynamic portion of a plant's root system and a majorsource of soil organic matter. By altering plant species diversity andcomposition, soil conditions and nutrient availability, and consequentlybelowground allocation and dynamics of root carbon (C) inputs, land-use andmanagement changes may influence organic C storage in terrestrialecosystems. In three German regions, we measured fine root radiocarbon(¹⁴C) content to estimate the mean time since C in root tissues wasfixed from the atmosphere in 54 grassland and forest plots with differentmanagement and soil conditions. Although root biomass was on average greaterin grasslands 5.1 ± 0.8 g (mean ± SE, n = 27) than in forests3.1 ± 0.5 g (n = 27) (p < 0.05), the mean age of C in fineroots in forests averaged 11.3 ± 1.8 yr and was older and morevariable compared to grasslands 1.7 ± 0.4 yr (p < 0.001). Wefurther found that management affects the mean age of fine root C intemperate grasslands mediated by changes in plant species diversity andcomposition. Fine root mean C age is positively correlated with plantdiversity (r = 0.65) and with the number of perennial species (r = 0.77). Fineroot mean C age in grasslands was also affected by study region withaverages of 0.7 ± 0.1 yr (n = 9) on mostly organic soils in northernGermany and of 1.8 ± 0.3 yr (n = 9) and 2.6 ± 0.3 (n = 9) incentral and southern Germany (p < 0.05). This was probably due todifferences in soil nutrient contents and soil moisture conditions betweenstudy regions, which affected plant species diversity and the presence ofperennial species. Our results indicate more long-lived roots or internalredistribution of C in perennial species and suggest linkages between fineroot C age and management in grasslands. These findings improve our abilityto predict and model belowground C fluxes across broader spatial scales.

[学科分类] 地球化学与岩石