A global meta-analysis shows soil nitrogen pool increases after revegetation of riparian zones

Purpose: Sustainable management of riparian zone soils is required to ensure the health of natural ecosystems and maintenance of soil nitrogen (N) pools and soil N cycling. However, the effect of revegetation type and age on soil N pools remains poorly understood. Materials and methods: This study compiled data from published articles to understand the effects of revegetation types and age on soil total N (TN) and soil inorganic N (NH4+-N, and NO3−-N) using a meta-analysis. We extracted 645 observations from 52 published scientific articles. Results and discussion: The revegetation of riparian zones led to a significant increase of soil TN (mean effect size: 11.5%; 95% CI: 3.1% and 20.6%). Woodland increased soil TN significantly by 14.0%, which was associated with the presence of N fixing species and high litter inputs. Soil NH4+-N concentration significantly increased (mean effect size: 20.1%; 95% CI: 15.1% and 25.4%), whereas a significant decrease in soil NO3−-N (mean effect size: − 21.5%; 95% CI: − 15.0% and − 27.5%) was observed. Of the revegetation types considered in this paper, NO3−-N concentration in soil followed the order: grassland < shrubland < woodland, suggesting that woodland might be more efficient in soil NO3−-N retention than grassland. The high plant N uptake and accelerated NO3−-N leaching in grassland could be related to the decreased soil NO3−-N in grassland compared with other revegetation types. Revegetation significantly decreased soil moisture by (mean effect size: − 7.9%; 95% CI: − 3.3% and − 12.2%) compared with the control, which might be associated with the selection of exotic species as dominant vegetation in the riparian zone. Soil TN increased in revegetation ages between 10 and 40 years following revegetation and was related to increased soil organic carbon inputs within those ages following the establishment. Conclusions: This study provides insight into influence of different vegetation types and age on soil N pools and soil moisture. This study also highlights the importance of revegetation in riparian zones to increase soil TN.