The relationship between leaf physiognomy and precipitation has been explored worldwide in regions under different climate conditions. Unlike the linear relationship established between the percentage of woody dicot species with entire margins and mean annual temperature, precipitation has been reported to correlate to different leaf physiognomic characters depending on the region where the correlation is studied. To investigate if precipitation can be calculated from leaf physiognomic characters on the basis of regional sample sites, data from 50 mesic to humid forests in China were analyzed in this study. With data from Chinese forests, the leaf-area analysis based on linear regression between natural logarithms of leaf size and mean annual precipitation (MAP) shows no significant correlation. Both single and multiple linear regression analyses fail to confirm the correlation between leaf physiognomy and precipitation, which may result from the similarity of modern spatial distribution of temperature and precipitation in China. Our results show that, due to variations in climatic conditions among sampling regions, leaf physiognomic characters that correlate to precipitation are not consistent worldwide, and applications of models without considering regional constraints could mislead our understanding of palaeoclimate. Therefore, when choosing a leaf physiognomic model for palaeoclimate reconstructions, it is important to determine if the leaf physiognomy of the palaeoflora lies within the leaf physiognomic spectrum of the model used.

The relationship between leaf physiognomy and precipitation has been explored worldwide in regions under different climate conditions. Unlike the linear relationship established between the percentage of woody dicot species with entire margins and mean annual temperature, precipitation has been reported to correlate to different leaf physiognomic characters depending on the region where the correlation is studied. To investigate if precipitation can be calculated from leaf physiognomic characters on the basis of regional sample sites, data from 50 mesic to humid forests in China were analyzed in this study. With data from Chinese forests, the leaf-area analysis based on linear regression between natural logarithms of leaf size and mean annual precipitation (MAP) shows no significant correlation. Both single and multiple linear regression analyses fail to confirm the correlation between leaf physiognomy and precipitation, which may result from the similarity of modern spatial distribution of temperature and precipitation in China. Our results show that, due to variations in climatic conditions among sampling regions, leaf physiognomic characters that correlate to precipitation are not consistent worldwide, and applications of models without considering regional constraints could mislead our understanding of palaeoclimate. Therefore, when choosing a leaf physiognomic model for palaeoclimate reconstructions, it is important to determine if the leaf physiognomy of the palaeoflora lies within the leaf physiognomic spectrum of the model used.

The Coexistence Approach was established by Mosbrugger and Utescher (1997) as a plant-based method to reconstruct palaeoclimate by considering recent climatic distribution ranges of the nearest living relatives of each fossil taxon. During its existence for over more than 15. years, its basics have been tested and reviewed in comparison with other terrestrial and marine climate reconstruction techniques and climate modelling data. However, some controversies remain about its underlying data or its applicability in general.In view of these controversies this paper discusses the power and limitations of the Coexistence Approach by summarising past results and new developments. We give insights into the details and problems of each step of the application from the assignment of the fossil plant to the most suitable nearest living relative, the crucial consideration of the usefulness of specific taxa towards their climatic values and the correct interpretation of the software-based suggested palaeoclimatic intervals. Furthermore, we reflect on the fundamental data integrated in the Coexistence Approach by explaining different concepts and usages of plant distribution information and the advantages and disadvantages of modern climatic maps. Additionally, we elaborate on the importance of continually updating the information incorporated in the database due to new findings in e.g., (palaeo-)botany, meteorology and computer technology.Finally, for a transparent and appropriate use, we give certain guidelines for future applications and emphasize to users how to carefully consider and discuss their results. We show the Coexistence Approach to be an adaptive method capable of yielding palaeoclimatic and palaeoenvironmental information through time and space.