Grazing management practices are a major factor regulating nutrient cycling and plant growth in grasslands. However, the response of long-term grazing regimes to ecosystem carbon and nitrogen accumulation and plant productivity remains uncertain in karst landscapes. A 17 year-long field experiment, constituting the methods of grazing exclusion (GE), continuous grazing (CG), mowing and grazing (MG), and rotational grazing (RG), was conducted to assess the effects of long-term management measures on plant biomass, ecosystem organic carbon, and nitrogen stocks in a karst alpine grassland of the Yunnan-Guizhou Plateau. Our results showed that grazing significantly reduced the aboveground biomass (CG, MG, and RG) and root biomass (MG and RG) compared to GE, but there were no differences between the results obtained using the various grazing methods. The root/shoot ratio increased by 55.98% in CG and decreased by 52.96% and 37.14% in MG and RG, respectively, compared to that achieved with GE. Soil organic carbon (SOC) of GE was higher than that of CG, MG, and RG in each soil layer, while it was significantly higher at 0–10 cm and 20–30 cm. Grazing promoted the mean total N content with a significant increase in CG and RG, and significantly increased total P content in each soil layer compared to GE. Grazing significantly decreased the C/N and C/P ratios at each soil depth. GE significantly increased the ecosystem organic carbon stocks (EOCs) and decreased the ecosystem total nitrogen stocks (ETNs). Although there were no significant changes among the grazing methods, the EOCs increased by 22.29% (MG) and 16.31% (RG) and ETNs increased by 7.76% (RG) when compared to those obtained with CG. EOSs were positively correlated with SOC, stoichiometry (C: N: P), and aboveground biomass, while being negatively correlated with TP; ETNs were positively correlated with N and P, while being negatively correlated with C/N, C/P, aboveground biomass, and root biomass. Our results indicate that GE can provide significant improvements in plant recovery and ecosystem organic carbon storage, whereas RG is beneficial for promoting both EOCs and ETNs under the condition of pasturing utilisation in karst grasslands.