Distinct fine-root responses to precipitation changes in herbaceous and woody plants: a meta-analysis

Precipitation is one of the most important factors that determine productivity of terrestrial ecosystems. Precipitation across the globe is predicted to change more intensively under future climate change scenarios, but the resulting impact on plant roots remains unclear. Based on 154 observations from experiments in which precipitation was manipulated in the field and root biomass was measured, we investigated responses in fine-root biomass of herbaceous and woody plants to alterations in precipitation. We found that root biomass of herbaceous and woody plants responded differently to precipitation change. In particular, precipitation increase consistently enhanced fine-root biomass of woody plants but had variable effects on herb roots in arid and semi-arid ecosystems. In contrast, precipitation decrease reduced root biomass of herbaceous plants but not woody plants. In addition, with precipitation alteration, the magnitude of root responses was greater in dry areas than in wet areas. Together, these results indicate that herbaceous and woody plants have different rooting strategies to cope with altered precipitation regimes, particularly in water-limited ecosystems. These findings suggest that root responses to precipitation change may critically influence root productivity and soil carbon dynamics under future climate change scenarios.

Accuracy Evaluation and Consistency Analysis of Four Global Land Cover Products in the Arctic Region

Land cover is a fundamental component of crucial importance in the earth sciences. To date, many excellent international teams have created a variety of land cover products covering the entire globe. To provide a reference for researchers studying the Arctic, this paper evaluates four commonly used land cover products. First, we compare and analyze the four land cover products from the perspectives of land cover type, distribution and spatial heterogeneity. Second, we evaluate the accuracy of such products by using two sets of sample points collected from the Arctic region. Finally, we obtain the spatial consistency distribution of the products by means of superposition analysis. The results show the following: (a) among the four land cover products, Climate Change Initiative Land Cover (CCI-LC) has the highest overall accuracy (63.5%) in the Arctic region, GlobeLand30 has an overall accuracy of 62.2% and the overall accuracy of the Global Land Cover by the National Mapping Organization (GLCNMO) is only 48.8%. When applied in the Arctic region, the overall accuracy of the Moderate Resolution Imaging Spectroradiometer (MODIS) is only 29.5% due to significant variances. Therefore, MODIS and GLCNMO are not recommended in Arctic-related research as their use may lead to major errors. (b) An evaluation of the consistency of the four products indicates that the classification of the large-scale homogeneous regions in the Arctic yields satisfactory results, whereas the classification results in the forest–tundra ecotone are unsatisfactory. The results serve as a reference for future research. (c) Among the four products, GlobeLand30 is the best choice for analyzing finely divided and unevenly distributed surface features such as waters, urban areas and cropland. Climate Change Initiative Land Cover (CCI-LC) has the highest overall accuracy, and its classification accuracy is relatively higher for forests, shrubs, sparse vegetation, snow/ice and water. GlobeLand30 and CCI-LC do not vary much from each other in terms of overall accuracy. They differ the most in the classification accuracy of shrub-covered land; CCI-LC performed better than GlobeLand30 in the classification of shrub-covered land, whereas the latter obtained higher accuracy than that of the former in the classification of urban areas and cropland.