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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

GroupsInfluencing factorStandard of classificationCorresponding keyword classification
Land use change (LUC)DegradationEcosystem degradation, including diversity loss and loss of other ecological functionDegradation
RestorationThe restoration of degraded or cultivated ecosystems, including vegetation recoveryRestoration
CultivationAgricultural cultivation on other ecosystemsCultivation
ForestationForestation of other ecosystems, including plantation and agroforestryAfforestation
Agricultural abandonmentChanges from farmland to other ecosystems except forest, as farmland to forest was included in forestationLUC
DeforestationChanges from forest to other ecosystems except farmland, as forest to farmland was included in cultivationLUC
ManagementN additionIncluding N fertilization, N addition and N depositionN management
Chemical fertilizerOther chemical fertilizer including N or without NChemical fertilizer
Organic fertilizerOrganic fertilizer, organic manure, organic amendments and so onOrganic fertilizer
Integrated fertilizerFertilization including both chemical fertilizer and organic fertilizerHuman activities
Litter inputIncluding straw return, litter input and other organic matter inputsLitter or straw
No fertilizerNo fertilizer or organic matter inputOther factors
Cover cropCover cropLitter or straw
RotationCropping system including different crops or intercroppingRotation
No tillageIncluding reduced tillage and zero tillageTillage
TillageIncluding plow tillage, rotation tillage, deep tillage and othersTillage
Soil amendmentSoil amending with amendment inputs, including biochar, gypsum, lime, and othersBiochar, soil amendment
Combined agricultural managementManagement with at least 2 different agricultural measures, including organic farming and conservational farmingAgricultural management
Reduced grazingIncluding grazing exclusion and reductionGrazing
GrazingIncluding different intensities and frequencies of grazingGrazing
Forest harvestingIncluding whole tree harvest, stem harvesting, partial harvesting and different intensive harvestingForest management
Other managementFilm mulching, new rice varieties, inhibitors and so onAgricultural management, pesticides
Environmental and climatic changeWarmingIncluding temperature increases, experimental warming and othersWarming
Elevated CO2Elevated CO2Elevated CO2
Rainfall increaseRainfall increaseRainfall
Rainfall reductionRainfall reductionRainfall
WettingRewetting of drainage ecosystems or irrigationDrainage or wetting
DryingIncluding the drainage of flooded areas and drought in uplandsDrainage or wetting
Biotic disturbanceSoil disturbance by soil fauna, such as earthworms and so onBiotic disturbance
Plant invasionExotic plants invade the original ecosystemInvasions
FireIncluding wildfire and fire managementFire
PollutionIncluding metal pollution, waste pollution, organic contamination, acid rain, and so onPollution
Other environmental and climatic changesIncluding increased snowpack, elevated UV-B, attenuated UV-B, elevated O3, freeze–thaw and so onClimate change, environmental gradient
  1. The categorization of keywords in the bibliometric analysis (29 influencing factors) and the influencing factors in the collected results of the meta-analysis (33 influencing factors) were not exactly the same because the information obtained via the two methods was different