Feedbacks among plant traits, animals and plant decomposition across species

Plant litter, created by mortality of plants and their senesced parts, is an important component of Earth’s ecosystems. The presence of plant litter influences numerous ecosystem functions such as those related to biogeochemical cycles, habitat formation, energy flow, hydrological processes, modification of geomorphological features. Despite having been explored for decades, there is still much to be learned about its versatile role in ecosystem functioning. As the fears over the ever-rising atmospheric CO2 concentration and alarming biodiversity decline have permeated through Academia and have eventually become matters of public concern in recent years, plant litter has become relevant to policies aimed at carbon control and biodiversity conservation. Plant litter preserves a sizeable portion of plant carbon and nutrients, most of which is released to the environment gradually via decomposition. Dead plant organic matter also provides vital resources (i.e., shelter, food and reproductive sites) for a myriad of organisms throughout the entirety of its decomposition trajectory, making it pivotal for detrital food webs, hence a biodiversity hotspot. These two functions, carbon control and biodiversity support, are closely connected as part of the organisms hosted by plant litter are themselves involved in its decomposition . There is therefore great interest in advancing our mechanistic understanding of plant decomposition, needed for improving global carbon cycle modeling and conservation strategies.

Main research gaps addressed in this thesis

While seminal studies have identified climate, substrate quality, and decomposer organisms as primary drivers of decomposition, the relative dominance of these factors remains debated. In addition, significant gaps persist in our understanding of the contributions of vertebrates to plant decomposition, with limited research addressing how these animals influence the decomposition process. The impact of plant litter on biodiversity, particularly the deadwood-dependent diversity as result of the interspecific interactions within decomposer communities, is also inadequately documented. Interspecific interactions among decomposers can significantly influence biodiversity by creating or modifying deadwood heterogeneity. However, the mechanisms through which these interactions shape biodiversity are poorly understood.
In this thesis, I delve into the knowledge gaps on some of the important but overlooked ecological components crucial to plant decomposition and the concomitant (invertebrate) biodiversity. I dedicate three chapters of my doctoral thesis to rarely reported drivers of plant decomposition rates. I explore whether and how vertebrates control plant decomposition at the global scale in Chapter 2 by synthesizing existing literature. Additionally, Chapter 3 experimentally assesses the substantial role that a specific group of vertebrates, i.e. woodpeckers, play in deadwood decomposition. In Chapter 4, I look into how bark traits influence deadwood decomposition by modulating termite activity. Lastly, Chapter 5 explores the mechanisms shaping invertebrate biodiversity in deadwood, emphasizing how deadwood biodiversity is influenced by heterogeneity within deadwood and interspecific interactions. Chapter 6 will summarize and synthesize these four chapters and indicate remaining or emerging research gaps for further study.