Plant physiology and competition in a Mojave Desert riparian ecosystem: Proximate solutions to ultimate questions

The distribution and abundance patterns of species are of primary interest in ecology, and the interactions between an organism and its abiotic and biotic environment provide a basis for a better understanding of the mechanisms by which distribution and abundance patterns are governed. Physiological ecology provides an ideal platform for integrating the effects of both biotic and abiotic influences upon species performance, thus conferring a process-oriented insight into ecological patterns. This dissertation considers the physiological characteristics that may be related to Mojave Desert floodplain domination by Tamarix ramosissima, an exotic invasive riparian plant; Four woody riparian species---Tamarix ramosissima, Salix exigua, Prosopis pubescens and Pluchea sericea---were studied along the Virgin River in southern Nevada. Through field observation and manipulative experiments in the field and glasshouse, the relationships between plant water relations, competition, facilitation, and abiotic stress and environment were investigated at both proximate (i.e., process) and ultimate (i.e., pattern) levels; Tamarix dominated the Virgin River floodplain at a previously burned site (Half-Way Wash) within 50 years following fire. Physiological mechanisms for the success of Tamarix include its water use (on both leaf- and whole branch-levels), starch storage, early investment in additional ramets, and slow radial growth. Pluchea, a native, summer-active halophyte, dominates early seres through tolerance to extreme abiotic stresses, as indicated by the general unresponsiveness of physiological characteristics to the imposition of stress. Salix, which is also native, demonstrated radial growth patterns consistent with sensitivity to drought stress, demonstrated sensitivity to heat and drought stresses in many key physiological traits, and was relatively insensitive to the presence of other species; Studies of plant responses to stress yield a great deal of information concerning the relationships, both inhibitive and facilitative, between species. Furthermore, the relationships between abiotic stress, inhibition, facilitation, and chance environmental events (e.g., aseasonal flooding) contributes to further understanding the short- and long-term mechanisms involved in the successful invasion of the Virgin River floodplain by Tamarix ramosissima

The FLUXNET2015 dataset and the ONEFlux processing pipeline for eddy covariance data

The FLUXNET2015 dataset provides ecosystem-scale data on CO2, water, and energy exchange between the biosphere and the atmosphere, and other meteorological and biological measurements, from 212 sites around the globe (over 1500 site-years, up to and including year 2014). These sites, independently managed and operated, voluntarily contributed their data to create global datasets. Data were quality controlled and processed using uniform methods, to improve consistency and intercomparability across sites. The dataset is already being used in a number of applications, including ecophysiology studies, remote sensing studies, and development of ecosystem and Earth system models. FLUXNET2015 includes derived-data products, such as gap-filled time series, ecosystem respiration and photosynthetic uptake estimates, estimation of uncertainties, and metadata about the measurements, presented for the first time in this paper. In addition, 206 of these sites are for the first time distributed under a Creative Commons (CC-BY 4.0) license. This paper details this enhanced dataset and the processing methods, now made available as open-source codes, making the dataset more accessible, transparent, and reproducible.Peer reviewe

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The FLUXNET2015 dataset and the ONEFlux processing pipeline for eddy covariance data

Abstract The FLUXNET2015 dataset provides ecosystem-scale data on CO2, water, and energy exchange between the biosphere and the atmosphere, and other meteorological and biological measurements, from 212 sites around the globe (over 1500 site-years, up to and including year 2014). These sites, independently managed and operated, voluntarily contributed their data to create global datasets. Data were quality controlled and processed using uniform methods, to improve consistency and intercomparability across sites. The dataset is already being used in a number of applications, including ecophysiology studies, remote sensing studies, and development of ecosystem and Earth system models. FLUXNET2015 includes derived-data products, such as gap-filled time series, ecosystem respiration and photosynthetic uptake estimates, estimation of uncertainties, and metadata about the measurements, presented for the first time in this paper. In addition, 206 of these sites are for the first time distributed under a Creative Commons (CC-BY 4.0) license. This paper details this enhanced dataset and the processing methods, now made available as open-source codes, making the dataset more accessible, transparent, and reproducible