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New Mexico State University (2014)

The role of animals in soil organic carbon cycling in dryland ecosystems

Smith Jane G

Titre : The role of animals in soil organic carbon cycling in dryland ecosystems

Auteur : Smith Jane G

Université de soutenance : New Mexico State University

Grade : Doctor of Philosophy (Ph.D) 2014

Résumé
Soil organic carbon (SOC) makes-up one of the largest and most dynamic global carbon (C) pools. While the accumulation and retention of SOC is largely dependent on the productivity and composition of vegetation, animals also influence SOC cycling through their interactions with plants and soil. However, our understanding of the mechanisms controlling SOC dynamics is lacking, particularly with regard to the role of animals. Additionally, most of what we do know about SOC comes from mesic ecosystems where biotic and abiotic drivers are often different from those in arid and semiarid (dryland) ecosystems. The research presented in the following chapters addresses some of these gaps in our knowledge and illuminates the role of animals in SOC cycling processes in dryland ecosystems. To better understand how animals affect SOC pools in drylands, I quantified changes in the size of the SOC pool in response to livestock grazing in an eastern Australian semiarid woodland and found that even moderate levels of livestock grazing diminished SOC pools, particularly in fertile patches that form around tree islands. I then assessed how small mammals affect the quantity and quality of SOC inputs and the rate of SOC cycling through the generation of greenfall in a Chihuahuan Desert shrubland. I found that animals that create greenfall enhance both the quality and quantity of SOC inputs and increase the rate of decomposition. Lastly, I evaluated the long-term influence of two important animal groups, rodent and ants, on the size and stability of SOC pools in a shrubland in the transition zone between the Chihuahuan and Sonoran Deserts and found that while rodents diminished the quantity and stability of SOC in surface soil, ants increased the quantity, but did not affect the stability, of SOC in deeper soil layers. Overall, my findings substantiate the important influence that animals have on SOC cycling and support that in order to fully understand the processes regulating SOC dynamics in dryland ecosystems, we must include the role of animals

Mots clés : Arid soils — Australia. Carbon content — New Mexico. Desert ecology.

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Page publiée le 6 novembre 2014, mise à jour le 13 octobre 2018