Introduction

We live in a "carbon" world. Half of the dry mass of organisms is carbon. The uptake of carbon in the form of CO₂ by photosynthesis and the release of carbon in the form of CO₂ by respiration are the two drivers of the global carbon cycle. The transitory difference between carbon uptake and respiration by plants are "photoassimilates" that plants use for growth. When plants die, microbes recycle carbon back into the atmosphere. However, a small fraction may not be recycled but end up in the soil, forming humus. This chapter will introduce you to these processes in an alpine context.