Abstract. Global ecosystems vary in their function, and therefore resilience to disturbance, as a result of their location on Earth, structure, and anthropogenic legacy. Resilience can therefore be difficult to describe solely based on energy partitioning, as it fails to effectively describe how ecosystems use available resources, such as soil moisture. Maximum entropy production (MEP) has been shown to be a better metric to describe these differences as it relates energy use efficiencies of ecosystems to the availability of resources. We studied three sites in a longleaf pine ecosystem with varying levels of anthropogenic legacy and biodiversity, all of which were exposed to extreme drought. We quantified their resilience from radiative, metabolic and overall MEP ratios. Sites with anthropogenic legacy had ~10% lower overall and metabolic energy use efficiency compared to more biodiverse sites. This resulted in lower resilience and a delay in recovery from drought by ~1 year. Additionally, a set of entropy ratios to determine metabolic and overall energy use efficiency explained more clearly site-specific ecosystem function, whereas the radiative entropy budget gave more insights about structural complexities at the sites. Our study provides foundational evidence of how MEP can be used to determine resiliency across ecosystems globally.
Abstract. Ecosystems are open systems that exchange matter and energy with theirenvironment. They differ in their efficiency in doing so as a result of theirlocation on Earth, structure and disturbance, including anthropogenic legacy.Entropy has been proposed to be an effective metric to describe thesedifferences as it relates energy use efficiencies of ecosystems to theirthermodynamic environment (i.e., temperature) but has rarely been studied tounderstand how ecosystems with different disturbance legacies respond whenconfronted with environmental variability. We studied three sites in alongleaf pine ecosystem with varying levels of anthropogenic legacy and plantfunctional diversity, all of which were exposed to extreme drought. Wequantified radiative (effrad), metabolic and overall entropychanges – as well as changes in exported to imported entropy(effflux) in response to drought disturbance and environmentalvariability using 24 total years of eddy covariance data (8 years per site).We show that structural and functional characteristics contribute todifferences in energy use efficiencies at the three study sites. Our resultsdemonstrate that ecosystem function during drought is modulated by decreasedabsorbed solar energy and variation in the partitioning of energy and entropyexports owing to differences in site enhanced vegetation index and/or soilwater content. Low effrad and metabolic entropy as well as slowadjustment of effflux at the anthropogenically altered siteprolonged its recovery from drought by approximately 1 year. In contrast,stands with greater plant functional diversity (i.e., the ones that includedboth C3 and C4 species) adjusted their entropy exports when facedwith drought, which accelerated their recovery. Our study provides a pathforward for using entropy to determine ecosystem function across differentglobal ecosystems.
more » « less- Award ID(s):
- 1702996
- NSF-PAR ID:
- 10097134
- Date Published:
- Journal Name:
- Biogeosciences
- Volume:
- 16
- Issue:
- 8
- ISSN:
- 1726-4189
- Page Range / eLocation ID:
- 1845 to 1863
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Tropical cyclones can physically alter ecosystems, causing immediate and potentially long‐lasting effects on carbon dynamics. In 2018, Hurricane Michael hit the southeastern United States with category 5 winds at landfall and category 2 winds reaching over 100 miles inland, resulting in extensive damage. Longleaf pine woodlands in the path of the hurricane were damaged, but severity varied based on the storm track. We used a combination of eddy covariance measurements, airborne LiDAR, and forest inventory data to determine whether hurricane affects structure, function, and recovery of two longleaf pine woodlands at the ends of an edaphic gradient. We found that the carbon sink potentials in both sites were diminished following the storm, with reductions in net ecosystem exchange (NEE) primarily due to lower rates of photosynthesis, as respiration only increased marginally. The xeric site carbon losses and physiological reductions were smaller following the disturbance, which led to the recovery of ecosystem physiological activity to prestorm rates before that of the mesic site, as indicated by maximum ecosystem CO2uptake rates. Two years following the hurricane both stands continued to have reduced NEE, which signaled altered function. We expect both locations to recover their lost carbon stocks in ∼10–35 years; however, long‐term studies are needed to examine how longleaf woodlands respond to compounding disturbances, such as drought, fire, or other wind storms, which vary significantly across the ecosystem's range. Additionally, hurricanes are intensifying due to climate change, potentially amplifying the degree to which they will alter this ecosystem in the future.
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- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.5194/bg-16-1845-2019
