Grassland restoration in northern China is far from complete: evidence from carbon variation in the last three decades

Spatiotemporal dynamics of grassland aboveground biomass in northern China and the alpine region: Impacts of climate change and human activities

Grassland plays a crucial role in the global cycles of matter, energy, water and, climate regulation. Biomass serves as one of the fundamental indicators for evaluating the ecological status of grassland. This study utilized the Carnegie-Ames-Stanford Approach (CASA) model to estimate Net Primary Productivity (NPP) from meteorological data and the Global Inventory Monitoring and Modeling System (GIMMS) Normalized Difference Vegetation Index (NDVI) remote sensing data for northern China's temperate and alpine grasslands from 1981 to 2015. NPP was subsequently converted into aboveground biomass (AGB). The dynamic changes in grassland AGB were analyzed, and the influence of climate change was examined. The results indicate strong agreement between AGB estimations from the CASA model and Gill method based on field-measured AGB, confirming the model's reliability for these regions. The dynamic changes in AGB exhibited a significant increasing trend of 1.31 g/m2. Grazing intensity (GI), soil moisture, and mean annual precipitation are identified as key factors influencing changes in grassland AGB. Our findings indicate that precipitation and soil moisture are the primary drivers of AGB accumulation during the growing season (spring, summer, and autumn), while temperature plays a critical role in supporting biomass accumulation during winter. Higher temperatures in winter contributes to increased AGB in the following spring, particularly in desert steppe and alpine meadow ecosystems. These insights highlight the complex interaction between climate factors and human activities in shaping grassland productivity across different seasons.

Sown alfalfa pasture decreases grazing intensity while increasing soil carbon: Experimental observations and DNDC model predictions

INTRODUCTION

Grasslands are the most important land use in China and have experienced extensive degradation in the past few decades due to overgrazing. However, regionally viable solutions to grazing intensity alleviation remained elusive to date.

METHODS

Here, we evaluated the grazing intensity effects of sown alfalfa pastures in northern China using an experiment-modeling combined approach that involved six sites in field experiments and five provinces in DNDC modeling of sown alfalfa pasture's forage production and carbon sequestration potentials in marginal lands.

RESULTS

Our results showed that the sown alfalfa pasture's dry-matter yield varied between 4.5 and 9.0 Mg ha-1 under rainfed and irrigated conditions, respectively, from 2025 to 2035. If half of the available marginal lands were mobilized for alfalfa forage production, these yield levels meant that livestock grazing intensity on natural grasslands may drop 8-13% under rainfed and 20-33% under irrigated conditions. Our results also showed that marginal land's soil organic carbon contents were systematically higher under sown alfalfa pasture than under fallow management by a big margin of 8.5 and 9.9 g kg-1 (i.e., +79 and +95%), under rainfed and irrigated conditions, respectively, during 2025-2035.

DISCUSSION

Overall, these results demonstrated that sown alfalfa pasture on marginal lands represents an effective grassland conservation pathway over the short- to medium-term time horizon based on current technologies.

Effects of reforestation on plant species diversity on the Loess Plateau of China: A case study in Danangou catchment

Large-scale vegetation restoration has important impacts on plant species diversity, which then influences plant community stability and resilience. The purpose of this paper is to compare the diversity of plantations as well as the diversity of artificially restored and naturally restored grasslands under different years of recovery and to identify the plots with the highest species diversity by vegetation type and restoration duration to determine strategies for vegetation restoration in hilly and gully regions of the Loess Plateau. Stands of Robinia pseudoacacia and Caragana korshinskii of different ages (10, 20, 30 and 40 years old) in the Danangou catchment on the Loess Plateau of China were selected as a case study to analysis effects of afforestation on the structure and function of ecosystems. The results showed that (1) under different numbers of years of recovery, the species diversity of woodland changes with changes in the coverage of woody plants, and the species diversity of R. pseudoacacia plantations planted on sunny slopes and R. pseudoacacia and C. korshinskii plantations planted on shady slopes reaches its maximum when coverage reaches a minimum value after 20 and 30 years of recovery, respectively; (2) soil moisture (in both shallow and deep layers) is the key factor controlling species diversity in woodlands, as the soil moisture changes with the coverage of woody plants following different numbers of years of recovery, which then influences the species diversity; (3) compared to the woodlands, the natural grassland exhibited higher species diversity under all recovery duration. Therefore, natural recovery is recommended if only species diversity is considered rather than human demand for wood, but if demand for materials is considered, we recommend thinning R. pseudoacacia on sunny and shady slopes at the ages of 10-20 and 10-30 years, respectively.