Abstract
Across a landscape, aquatic-terrestrial interfaces within and between ecosystems are hotspots of organic matter (OM) mineralization. These interfaces are characterized by sharp spatio-temporal changes in environmental conditions, which affect OM properties and thus control OM mineralization and other transformation processes. Consequently, the extent of OM movement at and across aquatic-terrestrial interfaces is crucial in determining OM turnover and carbon (C) cycling at the landscape scale. Here, we propose expanding current concepts in aquatic and terrestrial ecosystem sciences to comprehensively evaluate OM turnover at the landscape scale. We focus on three main concepts toward explaining OM turnover at the landscape scale: the landscape spatio-temporal context, OM turnover described by priming and ecological stoichiometry, and anthropogenic effects as a disruptor of natural OM transfer magnitudes and pathways. A conceptual framework is introduced that allows for discussing the disparities in spatial and temporal scales of OM transfer, changes in environmental conditions, ecosystem connectivity, and microbial–substrate interactions. The potential relevance of priming effects in both terrestrial and aquatic systems is addressed. For terrestrial systems, we hypothesize that the interplay between the influx of OM and its corresponding elemental composition and the elemental demand of the microbial communities – stoichiometric question – may alleviate spatial and metabolic thresholds. In comparison, substrate level OM dynamics may be substantially different in aquatic systems due to matrix effects that accentuate the role of abiotic conditions, substrate quality, and microbial community dynamics. We highlight the disproportionate impact anthropogenic activities can have on OM cycling across the landscape including reversing natural OM flows through the landscape, disrupting ecosystem connectivity, and nutrient additions that cascade across the landscape. This knowledge is crucial for a better understanding of OM cycling in a landscape context, in particular since terrestrial and aquatic compartments may respond differently to the ongoing changes in climate, land use, and other anthropogenic interferences.
Highlights
Our mechanistic understanding of organic matter (OM) retention and turnover has undergone a profound paradigm shift as technological advances enable measurements and visualizations at ever smaller and at the same time larger scales
We focus on three main concepts toward explaining OM turnover at the landscape scale: the landscape spatiotemporal context, OM turnover described by priming and ecological stoichiometry, and anthropogenic effects as a disruptor of OM transfer, transformation rates, and pathways
We introduce a spatio-temporal model as a heuristic approach to integrate the many abiotic, biotic, and anthropogenic dimensions that describe OM transformations across the landscape
Summary
Our mechanistic understanding of organic matter (OM) retention and turnover has undergone a profound paradigm shift as technological advances enable measurements and visualizations at ever smaller and at the same time larger scales. Controversy and often confusion remain as concepts supporting intrinsic chemical properties, such as “lability and recalcitrance” including refractory substances such as humic and fulvic acids have persisted in the literature and society presentations We argue that this discussion is symptomatic of an emerging paradigm that, until now, has not adequately incorporated the multiple ideas and research avenues that served as a foundation of our past understanding. This process is predicted by adaptive management research (Holling, 2001) that anticipates a period of renewal in which resources or ideas are assembled in various often unsystematic ways to serve as the building blocks of something novel This period of change is evident in the literature as OM retention and release has been addressed from different perspectives: at the ecosystem level (Schmidt et al, 2011), the terrestrial-aquatic connectivity concept (Marin-Spiotta et al, 2014), the priming frame work (Guenet et al, 2010; Bianchi, 2011), and the linkage of carbon cycling across various spatial and temporal scales (Premke et al, 2016). We believe that such a framework is necessary in order to advance our current understanding of OM as the Earth’s systems rapidly respond to unprecedented and rapidly increasing climate and anthropogenic impacts
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
