scholarly journals Differential Organic Carbon Mineralization Responses to Soil Moisture in Three Different Soil Orders Under Mixed Forested System

2021 ◽  
Vol 9 ◽  
Author(s):  
Shikha Singh ◽  
Sindhu Jagadamma ◽  
Junyi Liang ◽  
Stephanie N. Kivlin ◽  
Jeffrey D. Wood ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Microbial Community ◽  
Organic Carbon ◽  
Enzyme Activities ◽  
Microbial Respiration ◽  
Extracellular Enzyme ◽  
Water Holding Capacity ◽  
Organic C ◽  
Extracellular Enzyme Activities ◽  
Water Holding

Soil microbial respiration is one of the largest sources of carbon (C) emissions to the atmosphere in terrestrial ecosystems, which is strongly dependent on multiple environmental variables including soil moisture. Soil moisture content is strongly dependent on soil texture, and the combined effects of texture and moisture on microbial respiration are complex and less explored. Therefore, this study examines the effects of soil moisture on the mineralization of soil organic C Soil organic carbon in three different soils, Ultisol, Alfisol and Vertisol, collected from mixed forests of Georgia, Missouri, and Texas, United States , respectively. A laboratory microcosm experiment was conducted for 90 days under different moisture regimes. Soil respiration was measured weekly, and destructive harvests were conducted at 1, 15, 60, and 90 days after incubation to determine extractable organic C (EOC), phospholipid fatty acid based microbial community, and C-acquiring hydrolytic extracellular enzyme activities (EEA). The highest cumulative respiration in Ultisol was observed at 50% water holding capacity (WHC), in Alfisol at 100% water holding capacity, and in Vertisol at 175% WHC. The trends in Extractable Organic Carbon were opposite to that of cumulative microbial respiration as the moisture levels showing the highest respiration showed the lowest EOC concentration in all soil types. Also, extracellular enzyme activities increased with increase in soil moisture in all soils, however, respiration and EEA showed a decoupled relationship in Ultisol and Alfisol soils. Soil moisture differences did not influence microbial community composition.

scholarly journals Understory vegetation plays a key role in sustaining soil microbial biomass and extracellular enzyme activities

2018 ◽  
Author(s):  
Yang Yang ◽  
Xinyu Zhang ◽  
Jifu Wang ◽  
Chuang Zhang ◽  
Huimin Wang ◽  
...  
Keyword(s):  
Microbial Biomass ◽  
Organic Carbon ◽  
Enzyme Activities ◽  
Extracellular Enzyme ◽  
Chinese Fir ◽  
Understory Vegetation ◽  
Extracellular Enzyme Activities ◽  
Soil Microbial ◽  
Vegetation Removal ◽  
Soil Environmental Factors

Abstract. It is desirable to learn more how understory vegetation affects soil microbial biomass and extracellular enzyme activities in a subtropical Chinese fir (Cunninghamia lanceolata) forests. The aim of this study was to determine the role of understory vegetation in controlling soil properties, through an examination of the effects of understory vegetation on soil environmental factors, microbial biomass, and extracellular enzyme activities. One paired treatment, which comprised understory vegetation removal (None) and understory vegetation left intact (Understory) in the context of litter removal, was established in a subtropical Chinese fir plantation. We mainly evaluated the effects of understory vegetation on soil environmental factors, the biomass of bacteria, fungi and actinomycetes, and the activities of five hydrolases, i.e., α-1,4-glucosidase, β-1,4-glucosidase (βG), β-1,4-N-acetylglucosaminidase (NAG), β-1,4-xylosidase and acid phosphatase (AP), and two oxidase, i.e., phenol oxidase (PPO) and peroxidase (PER). The soil moisture content (SMC), and the concentrations of soil dissolved organic carbon (DOC), particulate organic carbon (POC), soil organic carbon (SOC), ammonia nitrogen (NH4+-N), and total nitrogen, and the POC / SOC ratio declined by 4 % to 34 %, and the biomass of soil bacteria and fungi, total PLFA contents, and the activities of βG, NAG, PPO, and PER were between 13 % and 27 % lower, when understory vegetation was removed. The highest activity of AP among all the measured enzymes may reflect the P was limited in this area, while NAG was positive with the concentration of NO3−-N, reflected that P- and N-degrading enzyme affected by different mechanism. The positive relationship between DOC and AP implied that microorganisms absorb carbon to meet their needs for phosphorus. The concentrations of NO3−-N and NH4+-N were positively correlated with and αG and βG suggested the increased availability of N promoted the decomposition of carbon. Understory vegetation removal inhibited the propagation of microorganisms and restricted their enzyme activities, by reducing soil energy and above-ground nutrient inputs and altering the soil micro-environment. We therefore propose that, to sustain soil quality in subtropical Chinese fir plantations, understory vegetation should be maintained.

scholarly journals Plant and Soil Enzyme Activities Regulate CO2 Efflux in Alpine Peatlands After 5 Years of Simulated Extreme Drought

2021 ◽  
Vol 12 ◽  
Author(s):  
Zhongqing Yan ◽  
Enze Kang ◽  
Kerou Zhang ◽  
Yong Li ◽  
Yanbin Hao ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Plant Growth ◽  
Polyphenol Oxidase ◽  
Enzyme Activities ◽  
Extracellular Enzyme ◽  
Extreme Drought ◽  
Impact Factors ◽  
Extracellular Enzyme Activities ◽  
Standing Biomass ◽  
Plant Coverage

Increasing attention has been given to the impact of extreme drought stress on ecosystem ecological processes. Ecosystem respiration (Re) and soil respiration (Rs) play a significant role in the regulation of the carbon (C) balance because they are two of the largest terrestrial C fluxes in the atmosphere. However, the responses of Re and Rs to extreme drought in alpine regions are still unclear, particularly with respect to the driver mechanism in plant and soil extracellular enzyme activities. In this study, we imposed three periods of extreme drought events based on field experiments on an alpine peatland: (1) early drought, in which the early stage of plant growth occurred from June 18 to July 20; (2) midterm drought, in which the peak growth period occurred from July 20 to August 23; and (3) late drought, in which the wilting period of plants occurred from August 23 to September 25. After 5 years of continuous extreme drought events, Re exhibited a consistent decreasing trend under the three periods of extreme drought, while Rs exhibited a non-significant decreasing trend in the early and midterm drought but increased significantly by 58.48% (p < 0.05) during the late drought compared with the ambient control. Plant coverage significantly increased by 79.3% (p < 0.05) in the early drought, and standing biomass significantly decreased by 18.33% (p < 0.05) in the midterm drought. Alkaline phosphatase, polyphenol oxidase, and peroxidase increased significantly by 76.46, 77.66, and 109.60% (p < 0.05), respectively, under late drought. Structural equation models demonstrated that soil water content (SWC), pH, plant coverage, plant standing biomass, soil β-D-cellobiosidase, and β-1,4-N-acetyl-glucosaminidase were crucial impact factors that eventually led to a decreasing trend in Re, and SWC, pH, β-1,4-glucosidase (BG), β-1,4-xylosidase (BX), polyphenol oxidase, soil organic carbon, microbial biomass carbon, and dissolved organic carbon were crucial impact factors that resulted in changes in Rs. Our results emphasize the key roles of plant and soil extracellular enzyme activities in regulating the different responses of Re and Rs under extreme drought events occurring at different plant growth stages.

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