Geology topics

Siyuan Ye

Publications and source records attributed to Siyuan Ye.

4 recordsLinked to original sources

USGS2023

Tidal restriction likely has greater impact on the carbon sink of coastal wetland than climate warming and invasive plant

Aims Coastal salt marshes are productive ecosystems that are highly efficient carbon sinks, but there is uncertainty regarding the interactions among climate warming, plant species, and tidal restriction on C cycling. Methods Open-top chambers (OTCs) were deployed at two coastal wetlands in Yancheng, China, where native Phragmites australis ( Phragmites ) and invasive Spartina alterniflora ( Spartina ) were dominant, respectively. Two study locations were set up in each area based on difference in tidal action. The OTCs achieved an increase of average daytime air temperature of ~ 1.11–1.55 °C. Net ecosystem CO 2 exchange (NEE), ecosystem respiration ( R eco ), CH 4 fluxes, aboveground biomass and other abiotic factors were monitored over three years. Results Warming reduced the magnitude of the radiative balance of native Phragmites , which was determined to still be a consistent C sink. In contrast, warming or tidal flooding presumably transform the Spartina into a weak C source, because either warming-induced high salinity reduced the magnitude of NEE by 19% or flooding increased CH 4 emissions by 789%. Remarkably, native Phragmites affected by tidal restrictions appeared to be a consistent C source with the radiative balance of 7.11–9.64 kg CO 2 -eq m –2 yr –1 because of a reduction in the magnitude of NEE and increase of CH 4 fluxes. Conclusions Tidal restrictions that disconnect the tidal hydrologic connection between the ocean and land may transform coastal wetlands from C sinks to C sources. This transformation may potentially be an even greater threat to coastal carbon sequestration than climate warming or invasive plant species in isolation.

Plant and Soil↗

USGS2019

A 3-year in-situ measurement of CO2 efflux in coastal wetlands: Understanding carbon loss through ecosystem respiration and its partitioning

Understanding the link between ecosystem respiration (Reco) and its influential factors is necessary to evaluate the sources of gaseous carbon loss in coastal wetlands. Seablite (Suaeda salsa Pall.) is the main vegetation type pioneering temperate coastal wetlands in northeast China, and is generally an understudied wetland type. To evaluate the influence of environmental factors on Reco, a multi-year in-situ experiment was carried out during the growing seasons of 2012 to 2014. Total CO2 efflux was measured and separated further into soil microbial and belowground root respiration (Rs + r) and plant respiration (Rplant). Reco displayed strong seasonal variation, with effluxes as high as 845 to 1150 mg CO2 m−2 h−1 during summer months and as low as 32 to 111 mg CO2 m−2 h−1 during spring (when new shoots are sprouting) and fall (when plants are senescing) months. Aboveground plant structures contributed on average 79% to total plant biomass, and accounted for most of the Reco measured; i.e., 62–96% was associated as Rplant. Plant activity was strongly seasonal, accordingly driving Reco, with 1 g of soil-emergent S. salsa biomass (dry weight) producing approximately 1.58 mg CO2 per hour toward Reco during mid-summer. When water level was below the soil surface, Rs + r was exponentially correlated to air temperature. Because Reco for S. salsa marsh in the Liaohe Delta is controlled by plant growth cycles, inundation regime, and air temperature, this finding may be applied for national carbon budget estimation purposes from S. salsa wetlands throughout Northeast China and potentially close a key gap in understanding the role of this large wetland area in contributing to respiratory CO2 emissions globally.

Wetlands↗

USGS2018

Spatial distribution and ecological risk assessment of heavy metals in coastal surface sediments in the Hebei Province offshore area, Bohai Sea, China

Seven hundred and nine surface sediment samples, along with deeper sediment samples, were collected from Hebei Province along the coastal section of the Bohai Sea, China, and analyzed for grain size, concentrations of organic carbon (Corg) and heavy metals (Cu, Pb, Zn, Cr, Cd, As, and Hg). Results indicated that the average concentrations in the sediments were 16.1 mg/kg (Cu), 19.4 mg/kg (Pb), 50 mg/kg (Zn), 48.8 mg/kg (Cr), 0.1 mg/kg (Cd), 8.4 mg/kg (As), and 20.3 μg/kg (Hg). These concentrations generally met the China Marine Sediment Quality criteria. However, both pollution assessments indicated moderate to strong Cd and Hg contamination in the study area. The potential ecological risk index suggested that the combined ecological risk of the seven studied metals may be low, but that 24.5% of the sites, where sediments were more finer and higher in Corg concentration, had high ecological risk in Hg and Cd pollution.

Bohai Sea, Hebei Province↗

USGS2016

Inter-annual variability of area-scaled gaseous carbon emissions from wetland soils in the Liaohe Delta, China

Global management of wetlands to suppress greenhouse gas (GHG) emissions, facilitate carbon (C) sequestration, and reduce atmospheric CO 2 concentrations while simultaneously promoting agricultural gains is paramount. However, studies that relate variability in CO 2 and CH 4 emissions at large spatial scales are limited. We investigated three-year emissions of soil CO 2 and CH 4 from the primary wetland types of the Liaohe Delta, China, by focusing on a total wetland area of 3287 km 2 . One percent is Suaeda salsa , 24% is Phragmites australis , and 75% is rice. While S . salsa wetlands are under somewhat natural tidal influence, P . australis and rice are managed hydrologically for paper and food, respectively. Total C emissions from CO 2 and CH 4 from these wetland soils were 2.9 Tg C/year, ranging from 2.5 to 3.3 Tg C/year depending on the year assessed. Primary emissions were from CO 2 (~98%). Photosynthetic uptake of CO 2 would mitigate most of the soil CO 2 emissions, but CH 4 emissions would persist. Overall, CH 4 fluxes were high when soil temperatures were >18°C and pore water salinity <18 PSU. CH 4 emissions from rice habitat alone in the Liaohe Delta represent 0.2% of CH 4 carbon emissions globally from rice. With such a large area and interannual sensitivity in soil GHG fluxes, management practices in the Delta and similar wetlands around the world have the potential not only to influence local C budgeting, but also to influence global biogeochemical cycling.

Liaohe Delta↗