Plant-environment interactions across multiple scales

It has been known for a long time that the environment shapes the appearance of vegetation (vegetation structure). The systematic description of these effects has led to classifications of life forms at the organismic scale and biomes at the global scale by Alexander von Humboldt, Christen C. Raunkiær, Wladimir Koppen, and other early plant geographers and plant ecologists. Consequently, plant traits and processes carried out by plants (vegetation function) are influenced by climate and other environmental conditions. However, given the previous limitations of both observations and theory, systematic and comparative studies of plant ecology and physiological ecology only began in the twentieth century. Through their adaptive and genetic constitutions, plants can react to environmental changes by different mechanisms involving various time scales. These mechanisms include acclimation, plasticity, and evolution. Plant reactions, in turn, can feed back to influence the environment at different scales by exchanges of matter and energy. For example, plants humidify the air, change turbulence and wind field, and hence influence cloud formation; they absorb carbon dioxide, produce oxygen and reactive volatile organic compounds, and modify, protect, and stabilize soils. There are a large variety of techniques available to researchers for the observation of vegetation-environment interactions at different time scales. No single technique can answer all questions; they have to be used synergistically, and often times these "suites" of observations have to be deployed across broad geographic areas and in multiple types of biomes. Due to the complexity of interactions and feedbacks between vegetation and the environment, numerical modeling has become a pivotal tool in conjunction with model-data fusion techniques. This new emphasis on fusing observations and theory has provided scientists with unprecedented insight into the mechanisms governing plant-atmosphere interactions, permitted the scaling of mechanisms across broad spans of space and time, and provided an integrated picture of global ecological processes.