The modified Carnegie–Ames–Stanford Approach (CASA) model based on the comprehensive and sequential classification system of grasslands (CSCS, a unique vegetation classification system) was used to determine grassland net primary production (NPP) in Gansu province from 1982 to 2011 and its spatio-temporal variability. The relationship between NPP and climate drivers was analyzed. The results showed that annual NPP of grasslands in Gansu province averaged 139.30 gC m-2 yr -1 during the study period. NPP decreased from southeast to northwest across the province. Grassland NPP showed an increasing trend during the period 1982–2011, and the increase rate over the whole period was 92.91%. The highest NPP appeared in summer with more precipitation and higher cumulative temperature conditions; while the lowest values existed in winter. The largest correlation coefficient was found between the average annual NPP and the average annual precipitation (r = 0.77), followed by annual NPP and solar radiation (r = 0.70) or NDVI (r = 0.69), Annual NPP had no significant correlation with annual cumulative temperature (>0°C) or moisture index (K-value). Thus, precipitation is the major controlling factor on the average annual NPP in Gansu grassland. Solar radiation and NDVI also have important effects on grassland NPP in Gansu. These results may provide basic information for sustainable development and utilization of grassland and for the improvement and protection of the ecological environment as well.

Alpine meadows have become particularly vulnerable to climate change. Variations in precipitation and temperature affect the ecological production of a region. The matrices for ecosystem change include net primary production (NPP), net photosynthesis (PsnNet), and net ecosystem production (NEP), of NEP is the most important. Using the CENTURY model for alpine meadows, we investigated the response of NEP to climate change from 1969 to 2018 in Gannan, Gansu Province, China. The distribution pattern of NEP in Gannan was simulated with the model. The Mann–Kendall trend test was used to analyze the interannual variation of NEP for the individual counties and the entire study area over a 50-year period. The results showed the annual NEP distribution pattern varied widely in the region, with the highest NEP values in the southeastern part while northwestern part showed the lowest. The highest NEP was measured in summer with sufficient precipitation and higher temperatures, whereas the lowest values occurred in winter. The total carbon sequestered in the Gannan alpine meadow over the last 50 years was 43580.9 gC, with the average annual NEP of the alpine meadow being approximately 813.62 gC m−2 year−1. Due to the combined effects of precipitation and temperature variations, NEP exhibits significant seasonal and interannual variations. The simulated NEP values of the seven counties fluctuated over the last 50 years, with each county showing an upward trend and the simulated NEP in the entire Gannan area also showing a clear upward trend that mutated around the year 1990. Both precipitation and temperature were found to be significantly and positively correlated with NEP. Precipitation was a significant driving factor, while temperature interacted with precipitation on the carbon budget. The carbon budget in the alpine meadow was stabilized by increasing precipitation and temperature. Estimates from NEP were in satisfactory correlation with measurements (r2=0.74, n=25 at p<0.01). Our findings provide preliminary understanding of the carbon budget and climatic feedback in Gannan alpine meadows which will help to predict carbon fluxes in the terrestrial biosphere and the impacts of climate change.

China is one of the countries most impacted by desertification, with Gansu Province in the northwest being one of the most affected areas. Efforts have been made in recent decades to restore the natural vegetation, while also producing food. This has implications for the soil carbon sequestration and, as a result, the country’s carbon budget. Studies of carbon (C) dynamics in this region would help to understand the effect of management practices on soil organic carbon (SOC) as well as aboveground biomass (ABVG), and to aid informed decision-making and policy implementation to alleviate the rate of global warming. It would also help to understand the region’s contribution to the national C inventory of China. The CENTURY model, a process-based model that is capable of simulating C dynamics over a long period, has not been calibrated to suit Gansu Province, despite being an effective model for soil C estimation. Using the soil and grassland maps of Gansu, together with weather, soil, and reliable historical data on management practices in the province, we calibrated the CENTURY model for the province’s grasslands. The calibrated model was then used to simulate the C dynamics between 1968 and 2018. The results show that the model is capable of simulating C with significant accuracy. Our measured and observed SOC density (SOCD) and ABVG had correlation coefficients of 0.76 and 0.50, respectively, at p < 0.01. Precipitation correlated with SOCD and ABVG with correlation coefficients of 0.57 and 0.89, respectively, at p < 0.01. The total SOC storage (SOCS) was 436.098 × 106 t C (approximately 0.4356% of the national average) and the average SOCD was 15.75 t C/ha. There was a high ABVG in the southeast and it decreased towards the northwest. The same phenomenon was observed in the spatial distribution of SOCD. Among the soils studied, Hostosols had the highest SOC sequestration rate (25.6 t C/ha) with Gypsisols having the least (7.8 t C/ha). Between 1968 and 2018, the soil carbon stock gradually increased, with the southeast experiencing the greatest increase.

In recent years, carbon balance has been a hot research topic both at home and abroad. The grasslands are rich in carbon storage and are also sensitive to climate change, and the Gannan alpine meadow, a distinct type of grassland in Gansu Province, is used as the study area in this paper. The consequences of climate change have a huge impact on human development and can even cause major human disasters. Effective management of climate change is, therefore, a major problem that currently needs to be solved, and grasslands play an indispensable role in the process of carbon deposition in terrestrial ecosystems. The CENTURY model has been used to study the spatial distribution and changes in the carbon budget in the Gannan alpine meadow of Gansu Province over the last 50 years, which is of great significance for climate change management. The results show that 1) the carbon budget has different distribution characteristics in different regions. 2) The spatial distribution of the carbon budget changes over time, as evidenced by the different spatial distribution of the carbon budget in each study stage and quarter. The spatial distribution differs as well. Some areas in the northern part of southern Gansu are carbon sources in spring and carbon sinks in summer, autumn, and winter. The spatial distribution of the carbon budget changes over time and is different at each stage, but it is a carbon sink overall. 3) The Gannan alpine meadow as a whole demonstrated a carbon sink phenomenon from 1969 to 2018, and the carbon balance is a carbon sink. 4) Every year, the carbon sink initially increases and then shows a decreasing trend, with the carbon sink reaching a maximum in August. 5) Temperature and precipitation are positively correlated with net ecosystem productivity (NEP). 6) In the last 50 years, the Gannan alpine meadow has sequestered 43,580.9 gC of carbon. The annual and monthly average NEP values are approximately 871.62 gC/m2 and 72.635 gC/m2, respectively.

What is the ideal soil-grass combination for maximum photosynthesis? In this study, we investigated how soil and grassland types affect photosynthesis in the grasslands of Gannan, China. We divided the grasslands of Gannan into 166 study sites, each with a unique soil-grass combination by intersecting the soil and ecoregion maps using ArcGIS. We obtained 19 years of data on the Net Photosynthesis (PsnNet) of grasslands in the area from 2000 to 2018 and then divided them into &ldquo;growing season&rdquo; (June to September) and &ldquo;non-growing season&rdquo; (October top May). Between 2000 and 2018, PsnNet of grasslands showed a gradually increasing trend. The effect of soil type on PsnNet was not significant during the growing season. However, it was highly significant during the non-growing season. Among the soil types, grasses that grew in Mollic, Gelic, and Haplic soils had the highest rate of photosynthesis. The difference in PsnNet among the various grass types was highly significant during both seasons. However, Tropical and Subtropical succulent evergreen broad-leaf shrubs and Temperate meadows had the highest rate of photosynthesis. Additionally, there was a highly significant difference in PsnNet among the various soil-grass interactions. In the growing season, TStEgBLS growing Eutric soils had the highest PsnNet. However, SaDBLS growing in Gelic soils had the the highest.