Abstract
Vegetation type plays an important role in regulating the temporal and spatial variation of soil respiration. Therefore, vegetation patchiness may cause high uncertainties in the estimates of soil respiration for scaling field measurements to ecosystem level. Few studies provide insights regarding the influence of vegetation types on soil respiration and its temperature sensitivity in an estuary wetland. In order to enhance the understanding of this issue, we focused on the growing season and investigated how the soil respiration and its temperature sensitivity are affected by the different vegetation (Phragmites australis, Suaeda salsa and bare soil) in the Yellow River Estuary. During the growing season, there were significant linear relationships between soil respiration rates and shoot and root biomass, respectively. On the diurnal timescale, daytime soil respiration was more dependent on net photosynthesis. A positive correlation between soil respiration and net photosynthesis at the Phragmites australis site was found. There were exponential correlations between soil respiration and soil temperature, and the fitted Q 10 values varied among different vegetation types (1.81, 2.15 and 3.43 for Phragmites australis, Suaeda salsa and bare soil sites, respectively). During the growing season, the mean soil respiration was consistently higher at the Phragmites australis site (1.11 µmol CO2 m−2 s−1), followed by the Suaeda salsa site (0.77 µmol CO2 m−2 s−1) and the bare soil site (0.41 µmol CO2 m−2 s−1). The mean monthly soil respiration was positively correlated with shoot and root biomass, total C, and total N among the three vegetation patches. Our results suggest that vegetation patchiness at a field scale might have a large impact on ecosystem-scale soil respiration. Therefore, it is necessary to consider the differences in vegetation types when using models to evaluate soil respiration in an estuary wetland.
Highlights
Vegetation type plays an important role in regulating the temporal and spatial variations of soil respiration through controlling a variety of environmental variables [1,2,3,4]
The spatial distribution patterns of vegetation are mostly identified as patches of Phragmites australis, Suaeda salsa or bare soil on scales of meters to tens of meters because of the obvious gradient change of soil salt content
Precipitation concentrated in the period of August to September, with the largest daily rainfall of 65.9 mm occurred on 6 August (Fig. 2B)
Summary
Vegetation type plays an important role in regulating the temporal and spatial variations of soil respiration through controlling a variety of environmental variables [1,2,3,4]. These variables can be grouped into (1) the amount and chemical composition of organic matter deposited onto the soil surface [3,5,6], (2) the amount of plant C allocate to belowground [7,8,9], (3) the amount of photoassimilates that fuel the metabolic processes of mycorrhizae, endophytes and microbial populations in the rhizosphere [10,11], (4) soil microbial communities [12,13,14], and (5) soil properties and near-surface atmosphere [4,9,15,16]. Vegetation patchiness may introduce uncertainties in the estimates of the soil respiration models designed for scaling up field measurements to ecosystem levels [3,30]
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