Aim: Planted forests are becoming increasingly common world‐wide for a variety of reasons, including water conservation and carbon sequestration, although the effects of tree plantations on biodiversity are unclear with respect to whether planted ecosystems are “green deserts” or valuable habitats for biodiversity.Location: Global.Time period: 1980–2020.Taxa studied: Flora, fauna and microorganisms.Methods: By conducting a meta‐analysis of 361 observations from 138 sites world‐wide, we explored the global patterns and associated drivers of biodiversity responding to tree plantations by comparing biodiversity levels in plantations and adjacent habitats (primary or secondary forests).Results: Overall, the biodiversity (species richness) and abundance across multitrophic levels in tree plantations were lower than those in primary forests, reached similar values to secondary succession, but varied with plantation and management regimes. Specifically, the biodiversity across multitrophic levels in reforestation was higher than that in afforestation; the biodiversity in mixed, native species and unmanaged plantations was higher than that in monoculture, exotic species and managed plantations. The diversity of vertebrates, invertebrates and plants in reforestation was lower than that in primary forests, whereas belowground biodiversity in reforestation showed no difference from primary forests. Invertebrate diversity in reforestation was lower than that in secondary succession, whereas plant diversity was higher than that in secondary succession. Moreover, the biodiversity in reforestation increased with reforestation age. Furthermore, structural equation models showed that aboveground faunal diversity in reforestation was driven by canopy coverage and plant diversity and that reforestation affected belowground biodiversity mainly by changing soil organic carbon.Main conclusions: Our findings suggest that reforestation by planting mixed native species will be more beneficial to biodiversity. We reveal that biodiversity in intensively managed plantations is significantly lower than that in restoration‐oriented plantations. We highlight that primary forests are not replaceable, but that planted forests might be a reliable way to restore biodiversity rapidly.

Livestock grazing is an important component and driver of biodiversity in grassland ecosystems. While numerous studies and a few meta-analyses had been conducted on the response of single taxon diversity to grazing in grasslands, a synthesis of how multi-taxa diversity is affected has been largely missing, especially reflecting its changes along a grazing intensity gradient. We performed a comprehensive meta-analyses of 116 published studies on the species richness (SR) and Shannon−Wiener index (H′) of plants, arthropods, and microbes to examine the response of biodiversity to grazing intensity in temperate grasslands globally. This quantitative assessment showed that the response of SR and H′ to grazing intensity agreed with the intermediate disturbance hypothesis in grasslands; SR and H′ increased with light and moderate grazing intensities, while they decreased at heavy intensity. In addition, plant SR increased markedly with light and moderate grazing and declined with heavy grazing intensity; however, H′ increased at light intensity and declined at moderate and heavy intensities. Moreover, the SR and H′ of microbes were enhanced at light and moderate grazing and were significantly reduced with heavy intensity. The SR and H′ of arthropods monotonously declined with increasing grazing intensity. Importantly, structural equation modeling showed that grazing resulted in enhanced plant SR mainly through its negative effects on plant biomass. Grazing had negative effects on plant coverage and arthropod abundance so that arthropod SR declined with increased grazing intensity. Moreover, increased grazing intensity caused an increase in soil pH, decrease in soil moisture, and then a decrease in microbe SR. Our findings confirm that different taxa exhibit diverse responses to changes in grazing intensity, and the way that grazing intensity affects diversity also varied with different taxa. We strongly recommend considering the requirements of multi-taxa diversity when applying grazing management and including arthropods and microbes in monitoring schemes.