Controls of Temporal Variations on Soil Respiration in a Tropical Lowland Rainforest in Hainan Island, China

Abstract

Soil respiration represents the largest carbon (C) flux from terrestrial ecosystems to the atmosphere. We created a study site in tropical lowland rainforest and used static chamber method to measure the temporal variations of soil respiration and their relationship with environmental factors at monthly time scale. The temporal variations of soil respiration showed a seasonal pattern related to soil temperature (p < .01) and soil moisture (p < .05). We tested different regression models to explore the relationship between soil respiration and environmental factors. Soil respiration had a better fit with soil temperature than with soil moisture in single-factor models. At different temperatures, the Q 10 values from different models changed in rather different ways. We found that the mixed quadratic model composite of soil temperature and moisture had the best-fitting effect (R 2 ¼ .74) on soil respiration and could better explain the seasonal variation. In a certain soil moisture range close to 15%, soil respiration increased with soil temperature. However, soil respiration became restricted when the moisture was greatly higher or lower than this value. Furthermore, at low soil temperatures (lower than 16 C), higher soil moisture could decrease soil respiration rapidly. Thus, soil respiration in a tropical lowland rainforest is co-controlled by soil temperature and moisture. This study expands our observations of soil respiration in tropical forests and how it responds to environmental factors, which is important for reducing errors in evaluation and scaling up of soil carbon flux in climate change studies.

Soil Respiration Variations in Temperate Rhododendron (Rhododendron arboreum) Forest of Annapurna Conservation Area (ACA) in Nepal

“…However, the efect of ST on SR in two days of 2017 was found statistically insignifcant (p > 0.05, Figure 2(b); Figure D3, D4) because the diference between the maximum and minimum ST was very narrow range normally within 2 °C as the measurements were carried in a single season. Similar to this study, Cui et al [43] has also detected no signifcant variations of SR due to narrow variation range of the ST in the tropical lowland rainforest of China during the spring season [43] when the variations of ST were very less as we observed in the autumn season. Te compatible trend of SR and ST with signifcant exponential relation of this study was most likely noticed previously while observing the cutting efect on SR in Rhododendron forest in the National Park area in the UK [44].…”

“…Te SWC efect on SR and its variations are not simply understood due to the intricacy of soil on climate and its limitations in the temperate regions under the infuence of monsoon climate with exceptionally getting short period of saturation and drought of these regions [14,47]. However, the SWC efect of SR is the efective measure to evaluate the SR in the semiarid ecosystems [8,48] and tropical region [22,43] where precipitation enhance the most accepted driver of the ecosystem function. Te knowledge of soil-water efect on SR and the breach between them could be flled with the extended research for years with continuous measurements.…”

“…Due to the complexity of the components and spatially heterogeneous nature of the forest's soil, it is much difcult to understand the environmental variability [49], and uniquely coupled with other biotic processes, the most common might be the soil properties in generating a broad spectrum of CO 2 emission rates in the temperate forests [20]. Te prior observations by Cui et al [43] and Kochiieru et al [53] suggested that it is not surprising that SR rates vary considerably in diferent seasons, years, and in the diferent forests, eco-zones, and even in the diferent soils and land use types.…”

Soil Respiration Variations in Temperate Rhododendron (Rhododendronarboreum) Forest of Annapurna Conservation Area (ACA) in Nepal

“…Due to the complexity of the components and spatially heterogeneous nature of the forest's soil, it is much di cult to understand the environmental variability (Li et al, 2013), and uniquely coupled with other biotic processes, the most common might be the soil properties in generating a broad spectrum of CO 2 emission rates in the temperate forests (Klimek et al 2021). The prior observations by Cui et al (2020) and Kochiieru et al (2021) suggested that it is not surprising that SR rates vary considerably in different seasons, years and in the different forests, eco-zones, and even in the different soils and land use types.…”

Carbon flux estimates are sensitive to data source: a comparison of field and lab temperature sensitivity data

“…The Soil Incubation Database (SIDb) is an open database containing time-series respiration measurements from 16 laboratory experiments (Schädel et al 2020, Sierra et al 2020). We extracted respiration flux data from this database and calculated Q 10 using the exponential equation (Cui et al 2020):…”