@article {KNZ002045, title = {Mechanisms influencing physically sequestered soil carbon in temperate restored grasslands in South Africa and North America}, journal = {Biogeochemistry}, year = {2021}, abstract = {

Sequestering carbon (C) into stable soil pools has potential to mitigate increasing atmospheric carbon dioxide concentrations. Carbon accrues in grassland soil restored from cultivation, but the amount of physically protected C (here measured as microaggregate-within-macroaggregate C) and predominant mechanisms of accrual are not well understood. We modeled the rate of physically protected carbon accrued in three mesic temperate perennial restored grasslands from cross-continental regions using datasets with a wide range of restoration ages from northeast Kansas, USA; southeast Nebraska, USA; and northeast Free State, South Africa. Further, we investigated major controls on the amount of physically protected C in each site using structural equation modeling. Variables in the structural equation model were root biomass, root C:N ratio, soil structure (indicated by bulk density, percent of macroaggregates on a per whole soil mass basis, and percent of microaggregate-within-macroaggregates on a per macroaggregate mass basis), microbial composition (indicated by microbial biomass C, total phospholipid fatty acid [PLFA] biomass, and PLFA biomass of arbuscular mycorrhizae fungi [AMF] biomass), and microaggregate-within-macroaggregate C on a per whole soil mass basis. Across all sites, physically protected C accrued at a rate of 16\ \±\ 5 g m\−2 year\−1. Data from South Africa fit an a priori metamodel developed for northeast KS that hypothesized physically protected C could be explained as a function of microbial composition, soil structure, root C:N ratio, and root biomass (listed in order of strength of direct effect on physically protected C). In contrast to the model-based hypothesis, root C:N ratio was the strongest influence (negative) on physically protected C in South Africa. The lesser effect of AMF on physically protected C in South Africa was consistent with lower AMF biomass in arid environments. The hypothesized model did not fit southeast Nebraska data possibly due to high (~\ 30\%) clay content. Overall, these results suggest that physically protected C in soil with moderate amounts of clay (more than 10\% and less than 30\%) can be predicted with knowledge of roots (biomass and C:N ratio), microbial biomass, and soil aggregation.

}, keywords = {LTER-KNZ}, doi = {10.1007/s10533-021-00774-y}, url = {https://link.springer.com/article/10.1007/s10533-021-00774-y}, author = {Scott, D.A. and Bach, Elizabeth M. and Du Preez, Chris C. and Six, Johan and Baer, S.G.} } @article {KNZ001819, title = {Restoration and management for plant diversity enhances the rate of belowground ecosystem recovery}, journal = {Ecological Applications}, volume = {27}, year = {2017}, pages = {355 - 362}, abstract = {

The positive relationship between plant diversity and ecosystem functioning has been criticized for its applicability at large scales and in less controlled environments that are relevant to land management. To inform this gap between ecological theory and application, we compared recovery rates of belowground properties using two chronosequences consisting of continuously cultivated and independently restored fields with contrasting diversity management strategies: grasslands restored with high plant richness and managed for diversity with frequent burning (n = 20) and grasslands restored with fewer species that were infrequently burned (n = 15). Restoration and management for plant diversity resulted in 250\% higher plant richness. Greater recovery of roots and more predictable recovery of the active microbial biomass across the high diversity management strategy chronosequence corresponded with faster recovery of soil structure. The high diversity grasslands also had greater nutrient conservation indicated by lower available inorganic nitrogen. Thus, mesic grasslands restored with more species and managed for high plant diversity with frequent burning enhances the rate of belowground ecosystem recovery from long-term disturbance at a scale relevant to conservation practices on the landscape

}, keywords = {LTER-KNZ, Aggregates, Biodiversity, carbon, Ecosystem function, nitrogen, phospholipid fatty acid, prairie, root, soil}, doi = {10.1002/eap.1503}, url = {https://esajournals.onlinelibrary.wiley.com/doi/full/10.1002/eap.1503}, author = {Klopf, Ryan P. and S.G. Baer and E.M. Bach and Six, Johan} } @article {KNZ001516, title = {Plant and soil responses to high and low diversity grassland restoration practices}, journal = {Environmental Management}, volume = {49}, year = {2012}, pages = {412 -424}, abstract = {

The USDA\’s Conservation Reserve Program (CRP) has predominantly used only a few species of dominant prairie grasses (CP2 practice) to reduce soil erosion, but recently has offered a higher diversity planting practice (CP25) to increase grassland habitat quality. We quantified plant community composition in CP25 and CP2 plantings restored for 4 or 8 years and compared belowground properties and processes among restorations and continuously cultivated soils in southeastern Nebraska, USA. Relative to cultivated soils, restoration increased soil microbial biomass (P = 0.033), specifically fungi (P \< 0.001), and restored soils exhibited higher rates of carbon (C) mineralization (P = 0.010). High and low diversity plantings had equally diverse plant communities; however, CP25 plantings had greater frequency of cool-season (C3) grasses (P = 0.007). Older (8 year) high diversity restorations contained lower microbial biomass (P = 0.026), arbuscular mycorrhizal fungi (AMF) biomass (P = 0.003), and C mineralization rates (P = 0.028) relative to 8 year low diversity restorations; older plantings had greater root biomass than 4 year plantings in all restorations (P = 0.001). Low diversity 8 year plantings contained wider root C:N ratios, and higher soil microbial biomass, microbial community richness, AMF biomass, and C mineralization rate relative to 4 year restorations (P \< 0.050). Net N mineralization and nitrification rates were lower in 8 year than 4 year high diversity plantings (P = 0.005). We attributed changes in soil C and N pools and fluxes to increased AMF associated with C4 grasses in low diversity plantings. Thus, reduced recovery of AMF in high diversity plantings restricted restoration of belowground microbial diversity and microbially-mediated soil processes over time.

}, keywords = {LTER-KNZ, Conservation reserve program, Nitrogen mineralization, Phospholipid fatty acids, Soil microbial community, tallgrass prairie}, doi = {10.1007/s00267-011-9787-0}, url = {https://link.springer.com/article/10.1007\%2Fs00267-011-9787-0}, author = {E.M. Bach and S.G. Baer and Six, J.} } @article {KNZ001357, title = {Soil texture affects soil microbial and structural recovery during grassland restoration}, journal = {Soil Biology \& Biochemistry}, volume = {42}, year = {2011}, pages = {2182 -2191}, abstract = {

Many biotic and abiotic factors influence recovery of soil communities following prolonged disturbance. We investigated the role of soil texture in the recovery of soil microbial community structure and changes in microbial stress, as indexed by phospholipid fatty acid (PLFA) profiles, using two chronosequences of grasslands restored from 0 to 19 years on silty clay loam and loamy fine sand soils in Nebraska, USA. All restorations were formerly cultivated fields seeded to native warm-season grasses through the USDA\’s Conservation Reserve Program. Increases in many PLFA concentrations occurred across the silty clay loam chronosequence including total PLFA biomass, richness, fungi, arbuscular mycorrhizal fungi, Gram-positive bacteria, Gram-negative bacteria, and actinomycetes. Ratios of saturated:monounsaturated and iso:anteiso PLFAs decreased across the silty clay loam chronosequence indicating reduction in nutrient stress of the microbial community as grassland established. Multivariate analysis of entire PLFA profiles across the silty clay loam chronosequence showed recovery of microbial community structure on the trajectory toward native prairie. Conversely, no microbial groups exhibited a directional change across the loamy fine sand chronosequence. Changes in soil structure were also only observed across the silty clay loam chronosequence. Aggregate mean weighted diameter (MWD) exhibited an exponential rise to maximum resulting from an exponential rise to maximum in the proportion of large macroaggregates (\>2000 μm) and exponential decay in microaggregates (\<250 μm and \>53 μm) and the silt and clay fraction (\<53 μm). Across both chronosequences, MWD was highly correlated with total PLFA biomass and the biomass of many microbial groups. Strong correlations between many PLFA groups and the MWD of aggregates underscore the interdependence between the recovery of soil microbial communities and soil structure that may explain more variation than time for some soils (i.e., loamy fine sand). This study demonstrates that soil microbial responses to grassland restoration are modulated by soil texture with implications for estimating the true capacity of restoration efforts to rehabilitate ecosystem functions.

}, keywords = {LTER-KNZ, Aggregates, Conservation Reserve Program (CRP), Microbial biomass, Phospholipid fatty acids, Soil microbial communities, tallgrass prairie}, doi = {10.1016/j.soilbio.2010.08.014}, url = {https://www.sciencedirect.com/science/article/abs/pii/S0038071710003020?via\%3Dihub}, author = {E.M. Bach and S.G. Baer and Meyer, C.K. and Six, J.} } @article {KNZ001356, title = {Contrasting ecosystem recovery on two soil textures: implications for carbon mitigation and grassland conservation}, journal = {Ecosphere}, volume = {1}, year = {2010}, pages = {5 -}, abstract = {

Understanding processes that promote or constrain ecosystem recovery from disturbance is needed to predict the restorative potential of degraded systems. We quantified a suite of ecosystem properties and processes across two chronosequences of restored grasslands on contrasting soil textures to test the hypothesis that restorations on silty clay loam soil would exhibit greater recovery of soil carbon (C) and nitrogen (N) pools and fluxes than on loamy fine sand because soil with higher clay content possesses a greater capacity to physico-chemically protect organic matter. Warm-season grass aboveground net primary productivity was similar between the two soil textures. Root biomass increased and root quality (as indexed by C:N ratio) decreased across both chronosequences. An asymptote in the accumulation of N in roots in the silty clay loam chronosequence resulted in wider C:N ratios of roots than in the loamy fine sand chronosequence. Total soil C (TC) and microbial biomass C (MBC) increased across the silty clay loam chronosequence at 21.2 and 5.7 g C\·m\−2\·yr\−1, respectively, and contained \>6 times the amount of C in large macroaggregates and nearly 3 times the aggregate mean weighted diameter (MWD) relative to cultivated soil following 15 yrs of restoration. In contrast, there were no changes in TC, MBC, or MWD in the loamy fine sand chronosequence. Total and microbial biomass N increased at 2.0 and 0.27 g N\·m\−2\·yr\−1, respectively, across the silty clay loam chronosequence, and restored soil contained nearly 6 times large macroaggregate N than cultivated soil following 15 yrs of restoration. Potential net N mineralization rates declined with years of grass establishment in both soil textures, but overall rates were lower in the silty clay loam soil relative to the loamy fine sand, which was attributed to lower quality root systems, more improved soil structure, and larger microbial biomass. Thus, the potential for restored agricultural lands to mitigate CO2 emissions over the short term cannot be generalized across all soils. Lastly, the low restorative potential of cultivated loamy fine sand soil through grassland restoration within two decades (relevant to many conservation programs) underscores the need to prioritize preservation of remnant sand prairies.

}, keywords = {LTER-KNZ}, doi = {10.1890/ES10-00004.1 }, url = {https://esajournals.onlinelibrary.wiley.com/doi/full/10.1890/ES10-00004.1}, author = {S.G. Baer and Meyer, C.K. and E.M. Bach and Klopf, R.P. and Six, J.} } @mastersthesis {KNZ001358, title = {Biotic and abiotic drivers of soil microbial community recovery and ecosystem change during grasslands restoration}, volume = {MS Thesis}, year = {2009}, school = {Southern Illinois University}, type = {M.S. Thesis}, address = {Carbondale, IL}, abstract = {

Tallgrass prairies have some of the deepest and most fertile topsoil on earth. Widespread conversion of these grasslands to agriculture has decreased soil Carbon (C) storage by exacerbating erosion and disrupting aggregates that protect C from decomposition, coupled with lower plant C inputs. Thus, a primary goal of some grassland restorations is to improve soil structure and functioning. Conversion of cultivated systems to perennial grasslands often increases soil C, microbial biomass, and soil aggregate size and stability. A few studies have documented changes in soil microbial community structure after restoration. The objective of this work was two fold: 1) to explore the importance of soil texture and 2) determine plant diversity effects on recovery of soil biotic and abiotic properties. In the first study changes in soil microbial phospholipid fatty acid (PLFA) profiles and soil aggregates were examined in two 0-19 year chronosequences of restored grasslands in Nebraska on soils differing in texture, silty clay loam (SCL) and loamy fine sand (LFS), and compared them to native prairie. Soil was collected from the 0-10 cm soil depth at each site in May of 2007 and 2008. The SCL chronosequence exhibited increases in total PLFA biomass P\<0.05, r2=0.29), PLFA richness (P\<0.0001, r2=0.25), fungi (P\<0.0001, r2=0.65), fungal:bacterial ratio (P\<0.0001, r2=0.67), Gram (+) bacteria (P=0.02, r2=0.22), Gram (-) bacteria (P=0.05, r2=0.16), and actinomycetes (P=0.02, r2=0.23). Average soil aggregate diameter also increased (p=0.0002, r2=0.52). However, LFS sites showed no change across the chronosequence for any parameter. Total PLFA biomass (ANOVA, P\<0.0001), richness (P\<0.0001), and fungi (P=0.005) were greater on SCL restorations than LFS, but LFS had greater fungal:bacterial ratios (P=0.02). Soil microbial groups and soil aggregates were highly correlated, especially in the LFS choronosequence indicating that structural recovery is key to microbial community recovery. The second study investigated high diversity restorations with low diversity restorations on silty clay loam. In this study, high diversity and low diversity restorations in southeast Nebraska, aged 4 and 8 years were compared. The quantity of forbs seeded was too low and high diversity communities were a mixture of dominant C4 grasses (Andropogon gerardii Vitman, Schizachyrium scoparium (Michx.) Nash, Panicum virgatum L., Bouteloua curtipendula (Michx.) Torr. and Sorghastrum nutans (L.) Nash) and subdominant C3 grasses (Elymus canadensis L., Pascopyrum smithii (Rybd.) A. L{\"o}ve, and Elymus virginicus L.). Eight year old plantings had greater root biomass, root C storage, root C:N ratio (P\<0.05 for all), microbial biomass (low diversity only, PC\<0.1, PN\<0.05), PLFA richness (low diversity only, P\<0.05), mycorrhizal fungi (P\<0.05), and C mineralization (low diversity only, P\<0.05) than 4 year old plantings. Low diversity plantings, which contained almost exclusively dominant C4 prairie grasses, had greater root C storage (P\<0.1), mycorrhizal fungi (8 years only, P\<0.1), and C mineralization (8 years only, P\<0.05). Thus, C4 grasses and their associated arbuscular mycorrhizal fungi seem to drive recovery of soil C, soil respiration, and soil microbial communities over time. Overall, this work indicates that rates and success of belowground recovery are dependent on both abiotic and biotic factors in restoration. Restored plant communities affected soil recovery as dominant C4 grasses appeared to drive belowground recovery, but recovery depended on soil texture.

}, keywords = {LTER-KNZ}, url = {https://www.researchgate.net/publication/42361822_Biotic_and_Abiotic_Drivers_of_Soil_Microbial_Community_Recovery_and_Ecosystem_Change_during_Grassland_Restoration}, author = {E.M. Bach} }