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Plant organ biomass allocation and morphological characteristics are important functional traits. The responses of plant root, stem, and leaf traits to heterogeneous habitats in floodplain wetlands are highly important for understanding the ecological adaptation strategies of riparian plants. However, the patterns of these responses remain unclear. In a floodplain wetland in the middle reaches of the Heihe River, we studied the responses of the root, stem, and leaf morphological traits and biomass allocation of Leymus secalinus to varying habitat conditions. We measured these traits in three sample plots, delineated based on distance from the riverbank: plot I (near the riparian zone, 50–150 m from the riverbank), plot II (middle riparian zone, 200–300 m from the riverbank), and plot III (far riparian zone, 350–450 m from the riverbank). The results showed that in plot I, L. secalinus tended to have slender roots and stems and small leaves, with a biomass allocation strategy that maximized the root–shoot ratio (RSR). In plot II, L. secalinus had thick stems and moderate leaf and root patterns, and the RSR values were between those of plot I and plot III. In plot III, L. secalinus had thin and short stems and large leaves; furthermore, among the root morphological structures, plot III had the shortest Rhizome length (RL) and longest Rhizome diameter (RD), and the RSR was the lowest. Moreover, there was a significant correlation between organ biomass and leaf thickness, stem length, RD, and RL in the three habitats (p < 0.05). By balancing the biomass allocation among organs, wetland plants in floodplains balance changes in root, stem, and leaf morphological characteristics to improve their environmental adaptation. [ABSTRACT FROM AUTHOR]

Plant organ biomass allocation and morphological characteristics are important functional traits. The responses of plant root, stem, and leaf traits to heterogeneous habitats in floodplain wetlands are highly important for understanding the ecological adaptation strategies of riparian plants. However, the patterns of these responses remain unclear. In a floodplain wetland in the middle reaches of the Heihe River, we studied the responses of the root, stem, and leaf morphological traits and biomass allocation of Leymus secalinus to varying habitat conditions. We measured these traits in three sample plots, delineated based on distance from the riverbank: plot I (near the riparian zone, 50–150 m from the riverbank), plot II (middle riparian zone, 200–300 m from the riverbank), and plot III (far riparian zone, 350–450 m from the riverbank). The results showed that in plot I, L. secalinus tended to have slender roots and stems and small leaves, with a biomass allocation strategy that maximized the root–shoot ratio (RSR). In plot II, L. secalinus had thick stems and moderate leaf and root patterns, and the RSR values were between those of plot I and plot III. In plot III, L. secalinus had thin and short stems and large leaves; furthermore, among the root morphological structures, plot III had the shortest Rhizome length (RL) and longest Rhizome diameter (RD), and the RSR was the lowest. Moreover, there was a significant correlation between organ biomass and leaf thickness, stem length, RD, and RL in the three habitats (p < 0.05). By balancing the biomass allocation among organs, wetland plants in floodplains balance changes in root, stem, and leaf morphological characteristics to improve their environmental adaptation.

Purpose: In recent decades, riparian floodplains have undergone intensive reclamation worldwide, which has potential to influence soil carbon (C) accumulation. Such influence generally varies based on reclamation duration. Therefore, a study on changes in soil C stock along the reclamation chronosequence can help reveal the impact of reclamation on terrestrial C cycling. Materials and methods: We chose natural floodplains (as the control) and croplands reclaimed for 13, 24, and 33 years in the lower reaches of the Yellow River and determined soil organic C (SOC) and soil inorganic C (SIC) contents at different depths and the stocks in 0–100 cm profiles. Results and discussion: The SOC and SIC stocks generally increased at average rates of 2.73 and 5.54 Mg C ha−1 yr−1, respectively, and the SIC stock was closely related with the SOC stock across the reclamation chronosequence. The SOC content increased more at 0–20 cm depth in the profile along the reclamation chronosequence, but the SIC content often had a higher rate of increase in the deep soil layers. Significantly, the contents of SOC and SIC were both positively correlated with the proportion of silt fractions. Conclusions: Our findings suggest that reclaimed croplands from riparian floodplain play an important role in C accumulation, highlighting the importance of soil inorganic C in C budget. Moreover, soil C accumulation relates closely to soil texture, which changes continuously along the reclamation chronosequence and often varies due to spatial heterogeneity. [ABSTRACT FROM AUTHOR]

Abstract: Recent work has shown that the biodiversity of organisms can influence geophysical processes such as the transport of streambed sediments and the erosion of soils. Yet most of this work has been conducted in small‐scale fluvial system mimics, demonstrating a clear need to investigate the relationship between biodiversity and erosion in natural systems. We conducted an observational field study across 3 rivers in forested watersheds in northern Michigan, U.S.A., quantifying streambank retreat rates using aerial photos and measuring riparian plant community biodiversity and abundance. We hypothesized that more diverse riparian plant communities would produce greater woody plant stem density and basal area, which in turn would reduce erosion rates of streambanks due to increased root production. We used structural equation modelling to compare causal networks using plant biodiversity metrics to predict streambank migration rate indirectly through effects on plant abundance, as well as models that used migration rate to predict plant abundance indirectly through effects on plant biodiversity. Although structural equation models explained both causal pathways successfully, models using biodiversity to predict migration rate were a better fit to data than models that used migration rate to predict plant biodiversity and abundance. The best performing models suggested plant biodiversity was indirectly negatively correlated with erosion rate (average standardized path coefficient = −0.22), after accounting for environmental differences between sites. This work adds to a growing body of evidence indicating that biodiversity can modify geophysical processes, demonstrating the need to explicitly account for biological variation when considering ecogeomorphic feedbacks. [ABSTRACT FROM AUTHOR]

• Reclamation of riparian floodplain promotes soil N and P accumulation. • Subsoil (20–100 cm) contributes great to the increase of TN and TP stocks. • Soil TN content and N: P in croplands indicate N-limitation, despite an increase. • Reclamation generally increases activities of most soil enzymes. • Enzyme activities relate closely to soil TN content or N: P ratio. Croplands reclaimed from floodplain wetlands play an important role in food production. As reclamation continues, various agronomic measures affect soil nutrient contents and metabolism. In the lower reaches of the Yellow River, we selected croplands (wheat and maize double-cropped system) reclaimed for 13, 24, and 33 years from natural wetlands (as the control), with similar starting soil characteristics and management practices. We determined total nitrogen (TN) and phosphorus (TP) contents and enzyme activities (including invertase, dehydrogenase, β-glucosidase, urease, protease, acid phosphatase, and alkaline phosphatase) in 0–100 cm soil profile. As results, TN and TP contents increased following reclamation, particularly in the plough layer (0–20 cm) with a clear increase during the chronosequence. The subsoil (20–100 cm) accounted for 55.3–63.9% and 66.6–68.0% of the N and P stocks in croplands, respectively. The TN content was positively correlated with the silt proportion in the 100-cm profile, whereas TP content was positively correlated with the clay proportion in the plough layer, and negatively with pH in the subsoil. Nevertheless, the C: N and C: P ratios in the plough layer were higher in the croplands than in the natural wetlands, and the N: P ratio increased from 0.4 to 2.6 following reclamation. Activities of most enzymes in the plough layer increased along with the chronosequence, and the subsoil generally had higher enzyme activity after 33 years of reclamation than in the natural wetlands. Redundancy analysis revealed that TN content and N: P ratio had strong explanatory power for the enzyme activities in the plough and subsoil layers, respectively. These findings suggest reclamation increases soil nutrient contents and enzyme activities in the floodplains, and the subsoil plays an essential role. However, these croplands remain N deficient. Thus, applying N fertilizer, as well as planting deep-rooted and N 2 -fixing crops, should be considered for agricultural management. [ABSTRACT FROM AUTHOR]

In this study effects of cypress knees as vegetation resistance factor on Turkey Creek watershed discharge calculation were analyzed. The Turkey Creek watershed is a 3rd order stream system draining an approximate area of 5,240 ha. It is located at 33°08' N latitude and 79°47' W longitude, approximately 60 km north-west of City of Charleston in South Carolina (USA). Turkey Creek (WS 78) is typical of other watersheds in the south Atlantic coastal plain. In the case of Turkey Creek watershed, one of the main channels and riparian floodplain vegetation contains cypress trees. Cypress trees live in moist or swampy regions along the Atlantic coastal plain. The cypress trees are characterized by the unique root system called knees that appear just above the water line, up to 1.2 m above water surface. This study is conducted to examine the effects of roughness of cypress knee as related to its shape (diameter and height) on discharge estimates of the Turkey Creek watershed. Hydraulic characteristics of the cypress knees were determined by field inventory in selected cross-section along the main stream channel. The Pasche method was used to calculate the total Darcy–Weisbach friction factor in discharge capacity calculation of the study watershed. The results of this study show that the effect of vegetation shape in the Pasche approach is significant. If the variability of vegetation stem diameter is taken into consideration in the calculations, an increase by 10-32% in the values of friction coefficients occurs. [ABSTRACT FROM AUTHOR]

Summary: Streambank seeps commonly originate from localized heterogeneity or preferential flow pathways (PFPs) in riparian floodplains. However, limited field data have been reported on ground water seep flows and solute transport to seeps from PFPs. The objective of this research was to build upon previous floodplain-scale investigations of PFPs by analyzing seep discharge and transport characteristics through a single PFP. An important research question was whether this PFP could be conceptualized as a homogeneous, one-dimensional flow path. Streambank seep discharge measurements were obtained by inducing a hydraulic head in a trench injection system. Also, co-injection of Rhodamine WT (RhWT) and a potassium chloride (KCl) tracer over a 60-min period was used to investigate transport dynamics. Seep discharge and breakthrough curves for electrical conductivity (EC) and RhWT were measured at the streambank using a lateral flow collection device. The breakthrough curves were fit to one-dimensional convective-dispersion equations (CDEs) to inversely estimate solute transport parameters. The PFP from which the seep originated was clean, coarse gravel (6% by mass less than 2.0mm) surrounded by gravel with finer particles (20% by mass less than 2.0mm). Located approximately 2m from the trench, the seep (50cm by 10cm area) required at least 40cm of hydraulic head for flow to emerge at the streambank. At a higher hydraulic head of 125cm, seep discharge peaked at 3.5L/min. This research verified that localized PFPs can result in the rapid transport of water (hydraulic conductivity on the order of 400m/d) and solutes once reaching a sufficient near-bank hydraulic head. A one-dimensional equilibrium CDE was capable of simulating the EC (R 2 =0.94) and RhWT (R 2 =0.91) breakthrough curves with minimal RhWT sorption (distribution coefficient, Kd , equal to 0.1cm3/g). Therefore, the PFP could be conceptualized as a one-dimensional, homogenous flow and transport pathway. These results are consistent with previous research observing larger-scale phosphorus transport. [Copyright &y& Elsevier]

Tidal freshwater zones (TFZ) of coastal rivers link terrestrial watersheds to the ocean and are characterized by large, regularly inundated riparian zones. We investigated the effect of riparian denitrification on nitrogen flux in the TFZ Newport River, North Carolina (U.S.A.) by developing an empirical model of denitrification and parameterizing it using measured denitrification rates, sediment oxidation-reduction potential dynamics, and riparian topography. Denitrification rates were measured monthly in laboratory-incubated sediment cores by using a membrane inlet mass spectrometer to assess net water-borne N2 flux from the cores. Annual average rates of denitrification in three intertidal riparian habitats, emergent marsh, mudflat, and hardwood forest, were 1864, 1956, and 2018 μg m−2 h−1, respectively. Laboratory experiments and in-situ monitoring revealed that the temporal lag between tidal inundation and reduced, denitrifying conditions was 4–5 h. Field measurements and remotely sensed data showed that the inundated surface area during high tide was three times greater than that at low tide. By combining data on denitrification, oxidation-reduction potential, and topography, the model predicted that the daily denitrification flux constituted 2–15% of the daily riverine nitrate flux during most of the year and >100% during low discharge periods. Current regional and global nitrogen budgets thus may overestimate nitrogen delivery to the ocean by not accounting for the TFZ denitrification. [ABSTRACT FROM AUTHOR]