scholarly journals Multiple constraints cause positive and negative feedbacks limiting grassland soil CO2 efflux under CO2 enrichment

2020 ◽  
Vol 118 (2) ◽  
pp. e2008284117
Author(s):  
Philip A. Fay ◽  
Dafeng Hui ◽  
Robert B. Jackson ◽  
Harold P. Collins ◽  
Lara G. Reichmann ◽  
...  
Keyword(s):  
Carbon Cycling ◽  
Plant Community ◽  
Clay Soil ◽  
Sandy Loam ◽  
Species Turnover ◽  
Community Change ◽  
Silty Clay ◽  
Ecosystem Carbon ◽  
Negative Feedbacks ◽  
Limiting Resources

Terrestrial ecosystems are increasingly enriched with resources such as atmospheric CO2 that limit ecosystem processes. The consequences for ecosystem carbon cycling depend on the feedbacks from other limiting resources and plant community change, which remain poorly understood for soil CO2 efflux, JCO2, a primary carbon flux from the biosphere to the atmosphere. We applied a unique CO2 enrichment gradient (250 to 500 µL L−1) for eight years to grassland plant communities on soils from different landscape positions. We identified the trajectory of JCO2 responses and feedbacks from other resources, plant diversity [effective species richness, exp(H)], and community change (plant species turnover). We found linear increases in JCO2 on an alluvial sandy loam and a lowland clay soil, and an asymptotic increase on an upland silty clay soil. Structural equation modeling identified CO2 as the dominant limitation on JCO2 on the clay soil. In contrast with theory predicting limitation from a single limiting factor, the linear JCO2 response on the sandy loam was reinforced by positive feedbacks from aboveground net primary productivity and exp(H), while the asymptotic JCO2 response on the silty clay arose from a net negative feedback among exp(H), species turnover, and soil water potential. These findings support a multiple resource limitation view of the effects of global change drivers on grassland ecosystem carbon cycling and highlight a crucial role for positive or negative feedbacks between limiting resources and plant community structure. Incorporating these feedbacks will improve models of terrestrial carbon sequestration and ecosystem services.

scholarly journals Soil Texture Alters the Impact of Salinity on Carbon Mineralization

Agronomy ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 128
Author(s):  
Ruihuan She ◽  
Yongxiang Yu ◽  
Chaorong Ge ◽  
Huaiying Yao
Keyword(s):  
Soil Texture ◽  
Clay Soil ◽  
Sandy Loam ◽  
Microbial Community Composition ◽  
Clay Content ◽  
Interactive Effects ◽  
Silty Clay ◽  
C Mineralization ◽  
Negative Effect ◽  
Silty Clay Soil

Soil salinization typically inhibits the ability of decomposer organisms to utilize soil organic matter, and an increase in soil clay content can mediate the negative effect of salinity on carbon (C) mineralization. However, the interactive effects of soil salt concentrations and properties on C mineralization remain uncertain. In this study, a laboratory experiment was performed to investigate the interactive effects of soil salt content (0.1%, 0.3%, 0.6% and 1.0%) and texture (sandy loam, sandy clay loam and silty clay soil with 6.0%, 23.9% and 40.6% clay content, respectively) on C mineralization and microbial community composition after cotton straw addition. With increasing soil salinity, carbon dioxide (CO2) emissions from the three soils decreased, but the effect of soil salinity on the decomposition of soil organic carbon varied with soil texture. Cumulative CO2 emissions in the coarse-textured (sandy loam and sandy clay loam) soils were more affected by salinity than those in the fine-textured (silty clay) soil. This difference was probably due to the differing responses of labile and resistant organic compounds to salinity across different soil texture. Increased salinity decreased the decomposition of the stable C pool in the coarse-textured soil, by reducing the proportion of fungi to bacteria, whereas it decreased the mineralization of the active C pool in the fine-textured soil through decreasing the Gram-positive bacterial population. Overall, our results suggest that soil texture controlled the negative effect of salinity on C mineralization through regulating the soil microbial community composition.

scholarly journals Livestock exclosure with consequent vegetation changes alters photo-assimilated carbon cycling in a <i>Kobresia</i> meadow

2013 ◽  
Vol 10 (11) ◽  
pp. 17633-17661 ◽  
Author(s):  
J. Zou ◽  
L. Zhao ◽  
S. Xu ◽  
X. Xu ◽  
D. Chen ◽  
...  
Keyword(s):  
Community Structure ◽  
Carbon Cycling ◽  
Plant Community ◽  
Plant Functional Groups ◽  
Ecosystem Functions ◽  
Plant Community Structure ◽  
Soil System ◽  
Plant Soil ◽  
Ecosystem Carbon ◽  
Aboveground Productivity

Abstract. Livestock exclosure has been widely used as an approach for grassland restoration. However, the effects of exclosure on grassland are controversial and can depend on many factors, such as the grassland ecosystem types, evolutionary history and so on. In this study, we conduct field experiments to investigate the variations of ecosystem function in response to livestock exclosure in a Kobresia humilis meadow under six years grazing exclosure on the Qinghai-Tibetan plateau. We focused on two ecosystem functions: plant community structure and ecosystem carbon cycling. The plant aboveground productivity, plant diversity and the composition of plant functional groups of the meadow were addressed as the indicators of the plant community structure. The 13C isotope pulse labeling technique was applied to evaluate the alterations of ecosystem carbon cycling during the short-term. The results showed that the plant community structure was changed after being fenced for six years, with significantly decreased aboveground productivity, species loss and varied composition of the four plant functional groups (grasses, sedges, legumes and forbs). Using the pulse labeling technique, we found a lower cycling rate of 13C in the plant–soil system of the fenced plots compared with the grazed sites during the first 4 days after labeling. A higher proportion of 13C amount recovered in the plant–soil system were migrated into soil as root exudates immediately after labeling at both fenced and control grazed sites, with significantly lower proportion in the fenced site, coinciding with the lower loss of 13C in soil respiration. Thirty-two days after labeling, 37% of recovered 13C remained in the soil of the fenced plots, with significant differences compared to the grazed plots (47%). In addition, less 13C (5% vs. 7%) was lost by soil respiration in the fenced plots during the chase period of 32 d. Overall, our study suggested that livestock exclosure had negative effects on the two ecosystem functions investigated, and the effects on 13C cycling and sequestrations in the soil were in response to variations in community structures, especially the suppression of forbs and legumes in the fenced site.

scholarly journals Species turnover reveals hidden effects of decreasing nitrogen deposition in mountain hay meadows

PeerJ ◽  
2019 ◽  
Vol 7 ◽  
pp. e6347 ◽  
Author(s):  
Tobias Roth ◽  
Lukas Kohli ◽  
Christoph Bühler ◽  
Beat Rihm ◽  
Reto Giulio Meuli ◽  
...  
Keyword(s):  
Plant Community ◽  
Plant Communities ◽  
Climate Warming ◽  
Species Turnover ◽  
Monitoring Program ◽  
Community Change ◽  
N Deposition ◽  
Indicator Values ◽  
Hay Meadows ◽  
Random Expectation

Nitrogen (N) deposition is a major threat to biodiversity in many habitats. The recent introduction of cleaner technologies in Switzerland has led to a reduction in the emissions of nitrogen oxides, with a consequent decrease in N deposition. We examined different drivers of plant community change, that is, N deposition, climate warming, and land-use change, in Swiss mountain hay meadows, using data from the Swiss biodiversity monitoring program. We compared indicator values of species that disappeared from or colonized a site (species turnover) with the indicator values of randomly chosen species from the same site. While oligotrophic plant species were more likely to colonize, compared to random expectation, we found only weak shifts in plant community composition. In particular, the average nutrient value of plant communities remained stable over time (2003–2017). We found the largest deviations from random expectation in the nutrient values of colonizing species, suggesting that N deposition or other factors that change the nutrient content of soils were important drivers of the species composition change over the last 15 years in Swiss mountain hay meadows. In addition, we observed an overall replacement of species with lower indicator values for temperature with species with higher values. Apparently, the community effects of the replacement of eutrophic species with oligotrophic species was outweighed by climate warming. Our results add to the increasing evidence that plant communities in changing environments may be relatively stable regarding average species richness or average indicator values, but that this apparent stability is often accompanied by a marked turnover of species.

scholarly journals Species turnover reveals hidden effects of decreasing nitrogen deposition in mountain hay meadows

2018 ◽  
Author(s):  
Tobias Roth ◽  
Lukas Kohli ◽  
Christoph Bühler ◽  
Beat Rihm ◽  
Reto Giulio Meuli ◽  
...  
Keyword(s):  
Plant Community ◽  
Plant Communities ◽  
Climate Warming ◽  
Species Turnover ◽  
Monitoring Program ◽  
Community Change ◽  
N Deposition ◽  
Indicator Values ◽  
Hay Meadows ◽  
Random Expectation

Nitrogen (N) deposition is a major threat to biodiversity in many habitats. The recent introduction of cleaner technologies in Switzerland has led to a reduction in the emissions of nitrogen oxides, with a consequent decrease in N deposition. We examined different drivers of plant community change, i.e. N deposition, climate warming, and land-use change, in Swiss mountain hay meadows, using data from the Swiss biodiversity monitoring program. We compared indicator values of species that disappeared from or colonized a site (species turnover) with the indicator values of randomly chosen species from the same site. While oligotrophic plant species were more likely to colonize, compared to random expectation, we found only weak shifts in plant community composition. In particular, the average nutrient value of plant communities remained stable over time (2003-2017). We found the largest deviations from random expectation in the nutrient values of colonizing species, suggesting that N deposition or other factors that change the nutrient content of soils were important drivers of the species composition change over the last 15 years in Swiss mountain hay meadows. In addition, we observed an overall replacement of species with lower indicator values for temperature with species with higher values. Apparently, the community effects of the replacement of eutrophic species with oligotrophic species was outweighed by climate warming. Our results add to the increasing evidence that plant communities in changing environments may be relatively stable regarding average species richness or average indicator values, but that this apparent stability is often accompanied by a marked turnover of species.

Impact of natural or industrial liming materials on soil properties and microbial activity

2009 ◽  
Vol 89 (2) ◽  
pp. 209-222 ◽  
Author(s):  
Roger Lalande ◽  
Bernard Gagnon ◽  
Isabelle Royer
Keyword(s):  
Alkaline Phosphatase ◽  
Soil Properties ◽  
Microbial Activity ◽  
Soil Ph ◽  
Clay Soil ◽  
Sandy Loam ◽  
Soil Layer ◽  
Cement Kiln ◽  
Silty Clay ◽  
Silty Clay Soil

Soil acidity is a major problem in agriculture because it limits plant growth and reduces crop productivity. The neutralizing potential of industrial by-products and their impact on soil properties were evaluated in two acidic soils characterized by contrasting textures, and submitted to intensive agriculture practices. Soil pH, microbial (dehydrogenase and alkaline phosphatase) activity, and Mehlich-3 extractable P, K, Ca and Mg were monitored in the year of soil incorporation of eight liming products and in the following 2 yr. In the sandy loam, liming products did not result in significant increases in soil pH in the 0- to 7.5-cm soil layer. Lime mud (LM) significantly increased soil pH by 0.4 units in the 7.5- to 20-cm layer compared with cement kiln dust (CKD). In the silty clay, calcium-phosphate-magnesium (CalPoMag) significantly raised pH by 0.65 units over both natural calcitic lime (NCa) and the magnesium dissolution product (MgD) in the first soil layer, and by 0.5 units over carbide lime (CL) treatment in the second soil layer. Activities of dehydrogenase and alkaline phosphatase were increased to various degrees by all liming materials, especially on the silty clay; LM and CalPoMag were the most beneficial materials. The exception was MgD, which did not result in any impact on microbial activity relative to the control. Both enzymatic activities were related to the increase in soil pH, particularly the alkaline phosphatase. Ion leaching was more pronounced in the sandy loam than in the silty clay soil, where large differences in the Ca and Mg ion levels were still detected in the 20- to 40-cm layer of the sandy loam. In this study, LM and CalPoMag are interesting liming products, particularly in the silty clay soil. Key words: Enzymatic activity, soil pH, lime, soil cations

Effects of three fertility amendments on soil dehydrogenase activity, organic C and pH

1997 ◽  
Vol 77 (2) ◽  
pp. 281-283 ◽  
Author(s):  
J. M. Cooper ◽  
P. R. Warman
Keyword(s):  
Clay Soil ◽  
Sandy Loam ◽  
Organic Amendments ◽  
Soil Microbial Activity ◽  
Chicken Manure ◽  
Silty Clay ◽  
Soil Organic C ◽  
Organic C ◽  
Soil Microbial ◽  
Silty Clay Soil

An Acadia silty clay and a Pugwash sandy loam were each fertilized with three rates of either composted chicken manure, fresh chicken manure, or synthetic fertilizer. The effects of these amendments on soil microbial activity (dehydrogenase enzyme activity, DHA), organic C and pH were monitored. The sandy loam soil, which was relatively high in organic C, did not experience increases in DHA due to organic amendments while compost produced higher DHA than manure or fertilizer treatments to the silty clay soil. There was no treatment effect on soil organic C in the sandy loam, while organic treatments increased organic C in the silty clay soil. Soil pH was affected by treatments to both soils with compost amendments producing the greatest increases in this parameter. The results emphasize the importance of considering initial soil organic C and soil texture when planning studies of the effect of organic amendments on soil microbial activity. Key words: Dehydrogenase, compost, chicken manure, pH, soil organic carbon

The effect of tillage and KCl addition on pH, conductance, NO3-N, P, K and Cl distribution in the soil profile

1994 ◽  
Vol 74 (3) ◽  
pp. 307-314 ◽  
Author(s):  
C. A. Grant ◽  
L. D. Bailey
Keyword(s):  
Soil Profile ◽  
Clay Soil ◽  
Sandy Loam ◽  
Sandy Loam Soil ◽  
Silty Clay ◽  
Zero Tillage ◽  
Tillage Systems ◽  
Fine Sandy Loam ◽  
Loam Soil ◽  
Silty Clay Soil

Distribution of NO3, P, K, Cl, pH and conductance through the soil profile were measured on two soil types after 4 yr of crop production using zero tillage (ZT) or conventional tillage (CT), with or without addition of KCl. All plots received N and P fertilizer each year as banded applications. Surface concentrations of NO3-N were higher under ZT than CT, particularly on the fine sandy loam soil. Accumulation of NO3-N also occurred in the 60- to 120-cm zone, under both tillage systems in both soils. Carryover of NO3-N was substantially greater on the silty clay than the fine sandy loam soil. Phosphate accumulated at the depth of band application in both soils under both tillage systems. Potassium concentration was generally higher under ZT than CT in the surface 15 cm of both soils, presumably due to surface retention of K from fertilizer applications and crop residues. Chloride was higher under ZT than CT in the surface 5 cm of both soils, but was higher under CT than ZT in the 30- to 60-cm and 60- to 120-cm depths in the silty clay soil, if KCl had been applied. The pH on both soils under both tillage systems was reduced in the 10- to 12.5-cm soil depth, corresponding to the zone of fertilizer application. On the silty clay soil, pH was higher under ZT than CT in the 10- to 15-cm depth and tended to be higher under ZT than CT at all depths below 15 cm. Conductance was not influenced by tillage in either soil. Application of KCl increased K and Cl concentrations in the surface 15 cm on both soils. Concentration of Cl was increased to 120 cm in both soils, indicating the mobility and leaching potential of this anion. Conductance and pH were increased in the 2.5- to 5.0-cm and 10- to 12.5-cm depths by KCl application in the fine sandy loam soil, but on the silty clay soil, only conductance was increased. Key words: Zero tillage, nutrient stratification, pH stratification

scholarly journals Species turnover reveals hidden effects of decreasing nitrogen deposition in mountain hay meadows

2018 ◽  
Author(s):  
Tobias Roth ◽  
Lukas Kohli ◽  
Christoph Bühler ◽  
Beat Rihm ◽  
Reto Giulio Meuli ◽  
...  
Keyword(s):  
Plant Community ◽  
Climate Warming ◽  
Species Turnover ◽  
Nutrient Content ◽  
Community Change ◽  
N Deposition ◽  
Indicator Values ◽  
Hay Meadows ◽  
Random Expectation ◽  
Using Data

Nitrogen (N) deposition is a major threat to biodiversity in many habitats. The recent introduction of cleaner technologies in Switzerland has led to a reduction in the emissions of nitrogen oxides, with an according decrease in N deposition. We examined different drivers of plant community change, i.e. N deposition, climate warming, and land-use change, in Swiss mountain hay meadows, using data from the Swiss biodiversity monitoring. We compared indicator values of species that disappeared from or colonized a site (species turnover) with the indicator values of randomly chosen species from the same site. While oligotrophic plant species were more likely to colonize, compared to random expectation, we found only weak shifts in plant community structure. In particular, the average nutrient value of plant communities remained stable over time (2003-2017). However, we found that the nutrient values of colonizing species showed the largest deviations from random expectation, suggesting that N deposition or other factors that change the nutrient content of soils were important drivers of the species composition change over the last 15 years in Swiss mountain hay meadows. In addition, we observed an overall replacement of species with lower indicator values for temperature with species with higher values. Apparently, the community effects of the replacement of eutrophic species with oligotrophic species was outweighed by climate warming. Our results add to the increasing evidence that inferring species turnover will generate a far more reliable understanding of the biotic response to changing environments than solely tracking average community composition.

scholarly journals Species turnover reveals hidden effects of decreasing nitrogen deposition in mountain hay meadows

2018 ◽  
Author(s):  
Tobias Roth ◽  
Lukas Kohli ◽  
Christoph Bühler ◽  
Beat Rihm ◽  
Reto Giulio Meuli ◽  
...  
Keyword(s):  
Plant Community ◽  
Plant Communities ◽  
Climate Warming ◽  
Species Turnover ◽  
Monitoring Program ◽  
Community Change ◽  
N Deposition ◽  
Indicator Values ◽  
Hay Meadows ◽  
Random Expectation

Nitrogen (N) deposition is a major threat to biodiversity in many habitats. The recent introduction of cleaner technologies in Switzerland has led to a reduction in the emissions of nitrogen oxides, with a consequent decrease in N deposition. We examined different drivers of plant community change, i.e. N deposition, climate warming, and land-use change, in Swiss mountain hay meadows, using data from the Swiss biodiversity monitoring program. We compared indicator values of species that disappeared from or colonized a site (species turnover) with the indicator values of randomly chosen species from the same site. While oligotrophic plant species were more likely to colonize, compared to random expectation, we found only weak shifts in plant community composition. In particular, the average nutrient value of plant communities remained stable over time (2003-2017). We found the largest deviations from random expectation in the nutrient values of colonizing species, suggesting that N deposition or other factors that change the nutrient content of soils were important drivers of the species composition change over the last 15 years in Swiss mountain hay meadows. In addition, we observed an overall replacement of species with lower indicator values for temperature with species with higher values. Apparently, the community effects of the replacement of eutrophic species with oligotrophic species was outweighed by climate warming. Our results add to the increasing evidence that plant communities in changing environments may be relatively stable regarding average species richness or average indicator values, but that this apparent stability is often accompanied by a marked turnover of species.

scholarly journals Field <sup>13</sup>CO<sub>2</sub> pulse labeling reveals differential partitioning patterns of photoassimilated carbon in response to livestock exclosure in a <i>Kobresia</i> meadow

2014 ◽  
Vol 11 (16) ◽  
pp. 4381-4391 ◽  
Author(s):  
J. Zou ◽  
L. Zhao ◽  
S. Xu ◽  
X. Xu ◽  
D. Chen ◽  
...  
Keyword(s):  
Community Structure ◽  
Carbon Cycling ◽  
Plant Community ◽  
Lower Proportion ◽  
Plant Functional Groups ◽  
Plant Community Structure ◽  
Soil System ◽  
Plant Soil ◽  
Ecosystem Carbon ◽  
Aboveground Productivity

Abstract. Livestock exclosure has been widely used as an approach for grassland restoration. However, the effects of exclosures on grasslands are controversial and can depend on many factors, such as the grassland ecosystem types, evolutionary history and so on. In this study, we conduct field experiments to investigate the variations of the ecosystem function in response to livestock exclosure in a Kobresia humilis meadow with 6 years of grazing exclosure on the Qinghai–Tibetan Plateau. We focused on two ecosystem functions: plant community structure and ecosystem carbon cycling. The plant aboveground productivity, plant diversity and the composition of plant functional groups of the meadow were addressed as the indicators of the plant community structure. The 13C isotope pulse labeling technique was applied to evaluate the alterations of ecosystem carbon cycling during a short term. The results showed that the plant community structure was changed after being fenced in for 6 years, with significantly decreased aboveground productivity, species loss and varied composition of the four plant functional groups (grasses, sedges, legumes and forbs). Using the pulse labeling technique, we found a lower cycling rate of 13C in the plant–soil system of the fenced plots compared with the grazed sites during the first 24 h after labeling. A higher proportion of recovered 13C in the plant–soil system migrated into the soil as root exudates immediately after labeling at both fenced and control grazed sites, with a significantly lower proportion in the fenced site, coinciding with the lower proportion of 13C lost from soil respiration. Thirty-two days after labeling, 37% of the recovered 13C remained in the soil of the fenced plots, with significant differences compared to in the grazed plots (47%). In addition, less 13C (5 vs. 7%) was lost by soil respiration in the fenced plots during the chase period of 32 days. Overall, our study suggests that livestock exclosures have negative effects on the plant community structure and partitioning patterns of the photoassimilated carbon in the Kobresia meadow, and the effects on photoassimilated carbon cycling are likely to result from the variations of community structures in the ecosystem.

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