Abstract:

Aims Our objectives were to compare vegetation biomass and total carbon and nitrogen content of severely degraded grassland and undisturbed Kobresia meadow, and to measure the relative influence of various rehabilitation practices on vegetation biomass and carbon and nitrogen content in early secondary succession.

Methods The research was conducted on alpine meadows in Dari County, Qinghai Province, China, using five treatments: undisturbed native meadow, severely degraded grassland, and three grasslands rehabilitated by different practices (mixed seeded, single seeded and natural recovery). In each treatment, vegetation C and N contents were calculated on an area and depth basis from biomass samples and plant concentration analyses.

Important findings In the undisturbed native meadow treatment, total aboveground biomass was 265.1 g·m^-2 and root biomass in the uppermost 30 cm averaged 6 982 g·m^-2. In the severely degraded grassland treatment, above ground biomass was only 139.9 g·m^-2 and root biomass was only 916 g·m^-2. Total aboveground biomass in the mixed seeded, single seeded and natural recovery treatments was 307.1, 179.9 and 200.4 g·m^-2, and root biomass was 1 323, 1 169 and 1 412 g·m^-2, respectively, after seven growing seasons. Total C content of vegetation in the undisturbed native meadow was 3 067.42 g·m^-2, while that of the severely degraded grassland treatment was only 414.07 g·m^-2. Therefore, land degradation leads to loss of 86.5% of the original plant tissue C. In addition, land degradation leads to loss of 68.3% of the original plant tissue N. Compared with the severely degraded land, mixed seeded and natural recovery treatments partly recover C and N content, indicating that they may be alternative approaches to sequestering C in former degraded alpine meadow.

Key words: alpine meadow, grassland degradation, rehabilitation, vegetation C and N content