Expanding the toolbox of nutrient limitation studies: A novel method of soil microbial in‐growth bags to evaluate nutrient demands in tropical forests

ABSTRACTSeveral studies have shown that rainfall seasonality, soil heterogeneity, and increased nitrogen (N) deposition may have important effects on tropical forest function. However, the effects of these environmental controls on soil microbial communities in seasonally dry tropical forests are poorly understood. In a seasonally dry tropical forest in the Yucatan Peninsula (Mexico), we investigated the influence of soil heterogeneity (which results in two different soil types, black and red soils), rainfall seasonality (in two successive seasons, wet and dry), and 3 years of repeated N enrichment on soil chemical and microbiological properties, including bacterial gene content and community structure. The soil properties varied with the soil type and the sampling season but did not respond to N enrichment. Greater organic matter content in the black soils was associated with higher microbial biomass, enzyme activities, and abundances of genes related to nitrification (amoA) and denitrification (nirKandnirS) than were observed in the red soils. Rainfall seasonality was also associated with changes in soil microbial biomass and activity levels and N gene abundances.Actinobacteria,Proteobacteria,Firmicutes, andAcidobacteriawere the most abundant phyla. Differences in bacterial community composition were associated with soil type and season and were primarily detected at higher taxonomic resolution, where specific taxa drive the separation of communities between soils. We observed that soil heterogeneity and rainfall seasonality were the main correlates of soil bacterial community structure and function in this tropical forest, likely acting through their effects on soil attributes, especially those related to soil organic matter and moisture content.IMPORTANCEUnderstanding the response of soil microbial communities to environmental factors is important for predicting the contribution of forest ecosystems to global environmental change. Seasonally dry tropical forests are characterized by receiving less than 1,800 mm of rain per year in alternating wet and dry seasons and by high heterogeneity in plant diversity and soil chemistry. For these reasons, N deposition may affect their soils differently than those in humid tropical forests. This study documents the influence of rainfall seasonality, soil heterogeneity, and N deposition on soil chemical and microbiological properties in a seasonally dry tropical forest. Our findings suggest that soil heterogeneity and rainfall seasonality are likely the main factors controlling soil bacterial community structure and function in this tropical forest. Nitrogen enrichment was likely too low to induce significant short-term effects on soil properties, because this tropical forest is not N limited.

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Reconsidering the phosphorus limitation of soil microbial activity in tropical forests

Functional Ecology ◽

10.1111/1365-2435.13043 ◽

2018 ◽

Vol 32 (5) ◽

pp. 1145-1154 ◽

Cited By ~ 17

Author(s):

Taiki Mori ◽

Xiankai Lu ◽

Ryota Aoyagi ◽

Jiangming Mo

Keyword(s):

Microbial Activity ◽

Tropical Forests ◽

Phosphorus Limitation ◽

Soil Microbial Activity ◽

Soil Microbial

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Century‐long apparent decrease in intrinsic water‐use efficiency with no evidence of progressive nutrient limitation in African tropical forests

Global Change Biology ◽

10.1111/gcb.15145 ◽

2020 ◽

Vol 26 (8) ◽

pp. 4449-4461 ◽

Cited By ~ 2

Author(s):

Marijn Bauters ◽

Sofie Meeus ◽

Matti Barthel ◽

Piet Stoffelen ◽

Hannes P. T. De Deurwaerder ◽

...

Keyword(s):

Water Use Efficiency ◽

Nutrient Limitation ◽

Tropical Forests ◽

Water Use ◽

Intrinsic Water Use Efficiency ◽

Apparent Decrease ◽

Use Efficiency

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Soil microbial nutrient constraints along a tropical forest elevation gradient: a belowground test of a biogeochemical paradigm

Biogeosciences ◽

10.5194/bg-12-6071-2015 ◽

2015 ◽

Vol 12 (20) ◽

pp. 6071-6083 ◽

Cited By ~ 34

Author(s):

A. T. Nottingham ◽

B. L. Turner ◽

J. Whitaker ◽

N. J. Ostle ◽

N. P. McNamara ◽

...

Keyword(s):

Tropical Forests ◽

Elevation Gradient ◽

Hydrolytic Enzymes ◽

Nutrient Status ◽

N Availability ◽

P Availability ◽

Total N ◽

Peruvian Andes ◽

Soil Microbial ◽

Microbial Nutrient Status

Abstract. Aboveground primary productivity is widely considered to be limited by phosphorus (P) availability in lowland tropical forests and by nitrogen (N) availability in montane tropical forests. However, the extent to which this paradigm applies to belowground processes remains unresolved. We measured indices of soil microbial nutrient status in lowland, sub-montane and montane tropical forests along a natural gradient spanning 3400 m in elevation in the Peruvian Andes. With increasing elevation there were marked increases in soil concentrations of total N, total P, and readily exchangeable P, but a decrease in N mineralization determined by in situ resin bags. Microbial carbon (C) and N increased with increasing elevation, but microbial C : N : P ratios were relatively constant, suggesting homeostasis. The activity of hydrolytic enzymes, which are rich in N, decreased with increasing elevation, while the ratio of enzymes involved in the acquisition of N and P increased with increasing elevation, further indicating an increase in the relative demand for N compared to P with increasing elevation. We conclude that soil microorganisms shift investment in nutrient acquisition from P to N between lowland and montane tropical forests, suggesting that different nutrients regulate soil microbial metabolism and the soil carbon balance in these ecosystems.

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Is microbial activity in tropical forests limited by phosphorus availability? Evidence from a tropical forest in China

10.1101/575001 ◽

2019 ◽

Author(s):

Taiki Mori ◽

Xiankai Lu ◽

Cong Wang ◽

Qinggong Mao ◽

Senhao Wang ◽

...

Keyword(s):

Organic Matter ◽

Organic Carbon ◽

Tropical Forest ◽

Microbial Activity ◽

Tropical Forests ◽

Microbial Respiration ◽

P Fertilization ◽

Soil Microbial ◽

Prevailing Paradigm ◽

P Addition

AbstractThe prevailing paradigm for soil microbial activity in tropical forests is that microbial activity is limited by phosphorus (P) availability. Thus, exogenous P addition should increase rates of organic matter decomposition. Studies have also confirmed that soil respiration is accelerated when P is added experimentally. However, we hypothesize that the increased rates of soil microbial respiration could be due to the release of organic material from the surface of soil minerals when P is added, because P is more successful at binding to soil particles than organic compounds. In this study, we demonstrate that P addition to soil is associated with significantly higher dissolved organic carbon (DOC) content in a tropical evergreen forest in southern China. Our results indicate that P fertilization stimulated soil respiration but suppressed litter decomposition. Results from a second sorption experiment revealed that the recovery ratio of added DOC in the soil of a plot fertilized with P for 9 years was larger than the ratio in the soil of a non-fertilized plot, although the difference was small. We also conducted a literature review on the effects of P fertilization on the decomposition rates of litter and soil organic matter at our study site. Previous studies have consistently reported that P addition led to higher response ratios of soil microbial respiration than litter decomposition. Therefore, experiments based on P addition cannot be used to test whether microbial activity is P-limited in tropical forest soils, because organic carbon desorption occurs when P is added. Our findings suggest that the prevailing paradigm on the relationship between P and microbial activity in tropical forest soils should be re-evaluated.

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A Novel Method to Assess the Aerobic Gasoline Degradation by Indigenous Soil Microbial Community using Microbial Diversity Information

Journal of the Korean Society of Civil Engineers ◽

10.12652/ksce.2016.36.5.0839 ◽

2016 ◽

Vol 36 (5) ◽

pp. 839-846

Author(s):

Seoyun Hwang ◽

Nari Lee ◽

Hyeji Kwon ◽

Joonhong Park

Keyword(s):

Microbial Community ◽

Microbial Diversity ◽

Soil Microbial Community ◽

Soil Microbial ◽

Novel Method

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Does long-term soil warming affect microbial element limitation? A test by short-term assays of microbial growth responses to labile C, N and P additions

10.5194/egusphere-egu2020-11341 ◽

2020 ◽

Author(s):

Chupei Shi ◽

Carolina Urbina Malo ◽

Ye Tian ◽

Shasha Zhang ◽

Marilena Heitger ◽

...

Keyword(s):

Microbial Communities ◽

Nutrient Limitation ◽

Microbial Growth ◽

Soil Samples ◽

Growth Responses ◽

Soil Warming ◽

Soil C ◽

Soil Microbial ◽

Limiting Nutrients

Human activities have caused global warming by 0.95 &#176;C since the industrial revolution, and average temperatures in Austria have risen by almost 2 &#176;C since 1880. Increased global mean temperatures have been reported to accelerate carbon (C) cycling, but also to promote nitrogen (N) and phosphorus (P) dynamics in terrestrial ecosystems. However, the extent of warming-induced increases in soil C, N and P processes can differ, causing an eventual uncoupling of biogeochemical C, N and P cycles, and leading to altered elemental imbalances between available plant and soil resources and soil microbial communities. The altered dynamics in soil C and nutrient availability caused by increased soil temperature could shift the growth-limiting element for soil microorganisms, with strong repercussions on the decomposition, mineralization and sequestration of organic C and nutrients. The latter relates to the conservative cycling of limiting elements while elements in excess are mineralized and released at greater rates by microbial communities.Despite the many laboratory and in situ studies investigating factors that limit soil microbial activity, most of them explored nutrient addition effects on soil respiration or soil enzyme activities. A critical assessment, however, clearly indicated the inappropriateness of these measures to deduce growth-limiting nutrients for soil microbes. Similar to studies of plant nutrient limitation, unequivocal assessment of soil microbial element limitation can only be derived from the response of microbial growth to element amendments. To our knowledge this has not been performed on soils undergoing long-term soil warming.In this study, we therefore investigated the effect of long-term soil warming on microbial nutrient limitation based on microbial growth measurements in a temperate calcareous forest soil. Soil samples were taken from two soil depths (0-10, 10-20 cm) in both control and heated plots in the Achenkirch soil warming project (>15 yrs soil warming by + 4 &#176;C). Soil samples were pre-incubated at their corresponding field temperature after sieving and removal of visible roots. The soils were amended with different combinations of glucose-C, inorganic/organic N and inorganic/organic P in a full factorial design, the nutrients being dissolved in 18O-water. After 24 hours of incubation, microbial growth was measured based on the 18O incorporation into genomic DNA. Nutrient (co)limitation was determined by comparing microbial growth responses upon C and nutrient additions relative to unamended controls. Basal respiration was also measured based on the increase in headspace CO2, allowing to estimate microbial C use efficiency (CUE). The fate of C and nutrient amendments was finally traced by measurements of inorganic and organic extractable and microbial biomass C, N and P. This study will thereby provide key insights into potential shifts in limiting nutrients for microbial growth under long-term soil warming, and into concomitant effects on soil C and nutrient cycles.

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