Table 1 Classification standard of each influencing factor in the collected results of the meta-analysis and its corresponding keyword classification in the bibliometric analysis
From: Changing soil carbon: influencing factors, sequestration strategy and research direction
Groups | Influencing factor | Standard of classification | Corresponding keyword classification |
|---|---|---|---|
Land use change (LUC) | Degradation | Ecosystem degradation, including diversity loss and loss of other ecological function | Degradation |
Restoration | The restoration of degraded or cultivated ecosystems, including vegetation recovery | Restoration | |
Cultivation | Agricultural cultivation on other ecosystems | Cultivation | |
Forestation | Forestation of other ecosystems, including plantation and agroforestry | Afforestation | |
Agricultural abandonment | Changes from farmland to other ecosystems except forest, as farmland to forest was included in forestation | LUC | |
Deforestation | Changes from forest to other ecosystems except farmland, as forest to farmland was included in cultivation | LUC | |
Management | N addition | Including N fertilization, N addition and N deposition | N management |
Chemical fertilizer | Other chemical fertilizer including N or without N | Chemical fertilizer | |
Organic fertilizer | Organic fertilizer, organic manure, organic amendments and so on | Organic fertilizer | |
Integrated fertilizer | Fertilization including both chemical fertilizer and organic fertilizer | Human activities | |
Litter input | Including straw return, litter input and other organic matter inputs | Litter or straw | |
No fertilizer | No fertilizer or organic matter input | Other factors | |
Cover crop | Cover crop | Litter or straw | |
Rotation | Cropping system including different crops or intercropping | Rotation | |
No tillage | Including reduced tillage and zero tillage | Tillage | |
Tillage | Including plow tillage, rotation tillage, deep tillage and others | Tillage | |
Soil amendment | Soil amending with amendment inputs, including biochar, gypsum, lime, and others | Biochar, soil amendment | |
Combined agricultural management | Management with at least 2 different agricultural measures, including organic farming and conservational farming | Agricultural management | |
Reduced grazing | Including grazing exclusion and reduction | Grazing | |
Grazing | Including different intensities and frequencies of grazing | Grazing | |
Forest harvesting | Including whole tree harvest, stem harvesting, partial harvesting and different intensive harvesting | Forest management | |
Other management | Film mulching, new rice varieties, inhibitors and so on | Agricultural management, pesticides | |
Environmental and climatic change | Warming | Including temperature increases, experimental warming and others | Warming |
Elevated CO2 | Elevated CO2 | Elevated CO2 | |
Rainfall increase | Rainfall increase | Rainfall | |
Rainfall reduction | Rainfall reduction | Rainfall | |
Wetting | Rewetting of drainage ecosystems or irrigation | Drainage or wetting | |
Drying | Including the drainage of flooded areas and drought in uplands | Drainage or wetting | |
Biotic disturbance | Soil disturbance by soil fauna, such as earthworms and so on | Biotic disturbance | |
Plant invasion | Exotic plants invade the original ecosystem | Invasions | |
Fire | Including wildfire and fire management | Fire | |
Pollution | Including metal pollution, waste pollution, organic contamination, acid rain, and so on | Pollution | |
Other environmental and climatic changes | Including increased snowpack, elevated UV-B, attenuated UV-B, elevated O3, freeze–thaw and so on | Climate change, environmental gradient |