Effects of Microtopography on Absorptive and Transport Fine Root Biomass, Necromass, Production, Mortality and Decomposition in a Coastal Freshwater Forested Wetland, Southeastern USA

Li, Xuefeng; Minick, Kevan J.; Luff, Jordan; Noormets, Asko; Miao, Guofang; Mitra, Bhaskar; Domec, Jean‐Christophe; Sun, Ge; McNulty, Steven G.; King, John S.

doi:10.1007/s10021-019-00470-x

Cited by 17 publications

(10 citation statements)

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“…In contrast, TBCA approaches would include both topographic positions spatially, depending upon how components of the TBCA calculations are estimated [24]. However, this microtopographic differentiation in BNPP is also not a consistent result; fine root BNPP (< 2 mm) to a depth of 20 cm averaged 455 g/m 2 /year for a mixed hardwood site along the Alligator River in North Carolina, USA, with 77% of that BNPP associated with hummocks [57]. Production of absorptive roots (i.e., first and second order roots) contributed more to hummock BNPP than transport roots (i.e., third-order roots), with transport roots contributing proportionately higher to BNPP in hollows [57].…”

Section: The Role Of Bnpp In Total Ecosystem Productivity In Retreating Freshwater Forestsmentioning

confidence: 99%

Belowground productivity varies by assessment technique, vegetation type, and nutrient availability in tidal freshwater forested wetlands transitioning to marsh

et al. 2021

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Wetlands along upper estuaries are characterized by dynamic transitions between forested and herbaceous communities (marsh) as salinity, hydroperiod, and nutrients change. The importance of belowground net primary productivity (BNPP) associated with fine and coarse root growth also changes but remains the dominant component of overall productivity in these important blue carbon wetlands. Appropriate BNPP assessment techniques to use in various tidal wetlands are not well-defined, and could make a difference in BNPP estimation. We hypothesized that different BNPP techniques applied among tidal wetlands differ in estimation of BNPP and possibly also correlate differently with porewater nutrient concentrations. We compare 6-month and 12-month root ingrowth, serial soil coring techniques utilizing two different calculations, and a mass balance approach (TBCA, Total Belowground Carbon Allocation) among four tidal wetland types along each of two river systems transitioning from freshwater forest to marsh. Median values of BNPP were 266 to 2946 g/m2/year among all techniques used, with lower BNPP estimation from root ingrowth cores and TBCA (266–416 g/m2/year), and higher BNPP estimation from serial coring of standing crop root biomass (using Smalley and Max-Min calculation methods) (2336–2946 g/m2/year). Root turnover (or longevity) to a soil depth of 30 cm was 2.2/year (1.3 years), 2.7/year (1.1 years), 4.5/year (0.9 years), and 1.2/year (2.6 years), respectively, for Upper Forest, Middle Forest, Lower Forest, and Marsh. Marsh had greater root biomass and BNPP, with slower root turnover (greater root longevity) versus forested wetlands. Soil porewater concentrations of NH3 and reactive phosphorus stimulated BNPP in the marsh when assessed with short-deployment BNPP techniques, indicating that pulses of mineralized nutrients may stimulate BNPP to facilitate marsh replacement of forested wetlands. Overall, ingrowth techniques appeared to represent forested wetland BNPP adequately, while serial coring may be necessary to represent herbaceous plant BNPP from rhizomes as marshes replace forested wetlands.

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Section: The Role Of Bnpp In Total Ecosystem Productivity In Retreating Freshwater Forestsmentioning

confidence: 99%

Belowground productivity varies by assessment technique, vegetation type, and nutrient availability in tidal freshwater forested wetlands transitioning to marsh

et al. 2021

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“…Live and dead AFRs and TFRs were separated according to the procedures described in Li et al (2020b). All fine roots were dried at 50 °C to a constant weight and weighed.…”

Section: Fine Root Biomass and Necromass Measurementsmentioning

confidence: 99%

“…AFR and TFR production, mortality and decomposition were determined using the dynamic-flow model (Li and Lange 2015;Li et al 2020b). Interval i was any given soil coring interval (1≤ i) (year).…”

Section: Dynamic-flow Modelmentioning

confidence: 99%

Methodological Comparisons of Absorptive and Transport Fine Root Production, Mortality and Decomposition in A Loblolly Pine Plantation Forest

Zheng

et al. 2021

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Background and aims Fine roots can be functionally classified into an absorptive fine root pool (AFR) and a transport fine root pool (TFR) and their production, mortality and decomposition play a critical role in forest soil carbon (C) cycling. Different methods give significant estimates. However, how methodological difference affects AFT and TFR production, mortality, and decomposition estimates remains unclear, impeding us to accurately construct soil C budgets. Methods We used dynamic-flow model, a model combining measurements of litterbags and soil cores, and balanced-hybrid model, a model combining measurements of minirhizotrons and soil cores, to quantify these fine root estimates in a managed loblolly pine forest. Results Temporal changes in production, mortality or decomposition estimates using both models were not different for both AFRs and TFRs. Annual production, mortality, and decomposition were comparable between AFRs and TFRs when measured using the dynamic-flow model but significantly higher for AFRs than for TFRs when measured using the balanced-hybrid model. Annual production, mortality and decomposition estimates using the balanced-hybrid model were 75%, 71% and 69% higher than those using the dynamic-flow model (P < 0.05 for all), respectively, for AFRs, but 12%, 6% and 5% higher than those using the dynamic-flow model (P > 0.05 for all), respectively, for TFRs. Model test showed that the balanced-hybrid model had greater estimation accuracy than the dynamic-flow model. Lower AFR estimates using the dynamic-flow model appeared to result from the underestimated AFR mass loss rate induced by the litterbag method. Conclusions Methodological difference had a more significant impact on AFR estimates than on TFR estimates. These results have important implications for better quantifying the most dynamic fraction of fine root system and understanding soil C cycling.

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“…In addition to evapoconcentration, mechanisms of increased nutrient availability in hummocks relative to hollows may be also attributed to accumulation of debris and litter (Resler and Stine, 2009) and/or higher turnover and cycling rates (Wetzel et al, 2005). Both the mass of absorptive fine roots (Li et al, 2020) and mycorrhizal activity are greater in hummocks than hollows, which may be important for P acquisition from ferric-bound particles (Cantelmo Jr. and Ehrenfeld, 1999). Overall, our finding of greater phosphorus on hummocks aligns with numerous studies where hummocks are consistently found to be zones of greater phosphorus concentrations than hollows (Jones et al, 1996;Wetzel et al, 2005;Eppinga et al, 2008).…”

Section: Controls On Soil Chemistrymentioning

confidence: 99%

Microtopography is a fundamental organizing structure of vegetation and soil chemistry in black ash wetlands

et al. 2020

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Abstract. All wetland ecosystems are controlled by water table and soil saturation dynamics, so any local-scale deviation in soil elevation and thus water table position represents variability in this primary control. Wetland microtopography is the structured variability in soil elevation and is typically categorized into a binary classification of local high points (hummocks) and local low points (hollows). Although the influence of microtopography on vegetation composition and biogeochemical processes in wetlands has received attention around the globe, its role in forested wetlands is still less understood. We studied relationships among microtopography and understory vegetation communities, tree biomass, and soil chemistry in 10 black ash (Fraxinus nigra Marshall) wetlands in northern Minnesota, USA. To do so, we combined a 1 cm resolution surface elevation model generated from terrestrial laser scanning (TLS) with colocated water table, vegetation, and soil measurements. We observed that microtopography was an important structural element across sites, where hummocks were loci of greater species richness; greater midstory and canopy basal area; and higher soil concentrations of chloride, phosphorus, and base cations. In contrast, hollows were associated with higher soil nitrate and sulfate concentrations. We also found that the effect of microtopography on vegetation and soils was greater at wetter sites than at drier sites, suggesting that the distance-to-mean water table is a primary determinant of wetland biogeochemistry. These findings highlight clear controls of microtopography on vegetation and soil distributions while also supporting the notion that microtopography arises from feedbacks that concentrate biomass, soil nutrients, and productivity on microsite highs, especially in otherwise wet conditions. We therefore conclude that microtopography is a fundamental organizing structure in black ash wetlands.

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Effects of Microtopography on Absorptive and Transport Fine Root Biomass, Necromass, Production, Mortality and Decomposition in a Coastal Freshwater Forested Wetland, Southeastern USA

Cited by 17 publications

References 50 publications

Belowground productivity varies by assessment technique, vegetation type, and nutrient availability in tidal freshwater forested wetlands transitioning to marsh

Belowground productivity varies by assessment technique, vegetation type, and nutrient availability in tidal freshwater forested wetlands transitioning to marsh

Methodological Comparisons of Absorptive and Transport Fine Root Production, Mortality and Decomposition in A Loblolly Pine Plantation Forest

Microtopography is a fundamental organizing structure of vegetation and soil chemistry in black ash wetlands

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