Fei Ren

The establishment of artificial grasslands is a highly effective strategy for the rapid restoration of degraded grasslands. To investigate the dynamics of biomass production and plant diversity—two critical objectives of grassland restoration—and their relationship during the early stages of artificial grassland establishment, we conducted an experiment in Menyuan County, located in the northeastern region of the Qinghai-Tibet Plateau. The experiment involved sowing different combinations of species (one, three, six, and nine species). Using data collected over three years (2021–2023), we found that biomass production generally increased over time. Specifically, in the second year, biomass production exhibited a unimodal relationship with the number of sown species, while in the third year, it increased linearly with the number of sown species. Plant diversity, which includes both sown and naturally occurring species, initially increased with the number of sown species in the first year but decreased in mixed sown plots in the third year. In the first year, biomass production was not correlated with plant diversity, whereas in the second and third years, biomass production decreased as plant diversity increased. This pattern was primarily driven by the accelerated growth of Gramineae. These results highlight the complex dynamics between biomass production and plant diversity during the early stages of artificial alpine grassland establishment. Our findings suggest that a trade-off between biomass and biodiversity should be carefully considered when designing restoration strategies, as achieving both high productivity and biodiversity may require a more nuanced approach.

The cycle of key nutrient elements nitrogen (N) and phosphorus (P) has been massively altered by anthropogenic activities. Little is known about the impacts on greenhouse gas (GHG) emission of the large nutrient additions occurring in the alpine grasslands of the Tibetan Plateau. We investigated soil surface emissions of carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) under control, N, P and combined nitrogen and phosphorus (NP) additions from July 2011 to September 2012. Compared to the control, CO₂ flux significantly increased by 14.6% and 27.4% following P and NP addition, respectively. The interaction of NP addition had a significant influence on CO₂ flux during the non-growing season and the spring thaw period. Compared to the control, CH₄ flux decreased by 9.9%, 23.2% and 26.7% following N, P and NP additions, respectively, and no interactive effect of NP addition was found in any period. Soil N₂O flux was significantly increased 2.6 fold and 3.3 fold, following N and NP addition treatments, respectively, and there was no interaction effect of NP addition together. The contribution of cumulative CO₂ emission during the non-growing season was less than 20% of the annual budget, but cumulative CH₄ and N₂O emissions during the same period can account for 37.3–48.9% and 44.7–59.5% of the annual budget, respectively. Methane and N₂O emissions did not increase greatly during the spring thawing period, with contributions of only 0.4–3.6% and 10.3–12.3% of the annual budget, respectively. Our results suggest that N and P addition could increase CO₂ and N₂O emissions and reduce CH₄ emission. Furthermore, although the non-growing season is very cold and long, cumulative CH₄ and N₂O emissions are considerable during this period and cannot be neglected by future studies evaluating the greenhouse gas emission budget in the Tibetan plateau.