Multiple constraints cause positive and negative feedbacks limiting grassland soil CO efflux under CO enrichment.

Terrestrial ecosystems are increasingly enriched with resources such as atmospheric CO that limit ecosystem processes. The consequences for ecosystem carbon cycling depend on the feedbacks from other limiting resources and plant community change, which remain poorly understood for soil CO efflux, J, a primary carbon flux from the biosphere to the atmosphere. We applied a unique CO enrichment gradient (250 to 500 µL L) for eight years to grassland plant communities on soils from different landscape positions.

Expert-augmented machine learning.

Machine learning is proving invaluable across disciplines. However, its success is often limited by the quality and quantity of available data, while its adoption is limited by the level of trust afforded by given models. Human vs.

Variation in pickleweed root-associated microbial communities at different locations of a saline solid waste management unit contaminated with petroleum hydrocarbons.

The main purpose of this study was to explore the potential influences of pickleweed vegetation on the abundance, diversity and metabolic activities of microbial communities in four distinct areas of a petroleum-contaminated solid waste management unit (SWMU) located in Contra Costa County, northern California. The four areas sampled include two central areas, one of which is central vegetated (CV) and one unvegetated (UV), and two peripheral vegetated areas, one of which is located to the west side of the SWMU (V-West) and one located to the east side (V-East). Measurements were made of total petroleum hydrocarbons (TPH), polyaromatic hydrocarbons (PAH), soil physicochemical properties, and various aspects of microbial communities including metabolic activities, microbial abundances (PLFAs), diversity and composition based on amplicon sequencing.

CO enrichment and soil type additively regulate grassland productivity.

Atmospheric CO enrichment usually increases the aboveground net primary productivity (ANPP) of grassland vegetation, but the magnitude of the ANPP-CO response differs among ecosystems. Soil properties affect ANPP via multiple mechanisms and vary over topographic to geographic gradients, but have received little attention as potential modifiers of the ANPP-CO response. We assessed the effects of three soil types, sandy loam, silty clay and clay, on the ANPP response of perennial C /C grassland communities to a subambient to elevated CO gradient over 10 yr in Texas, USA.

Flowering in grassland predicted by CO and resource effects on species aboveground biomass.

Continuing enrichment of atmospheric CO may change plant community composition, in part by altering the availability of other limiting resources including soil water, nutrients, or light. The combined effects of CO enrichment and altered resource availability on species flowering remain poorly understood. We quantified flowering culm and ramet production and biomass allocation to flowering culms/ramets for 10 years in C -dominated grassland communities on contrasting soils along a CO concentration gradient spanning pre-industrial to expected mid-21st century levels (250-500 μl/L).