POC Concentrations Research Articles

Pengaruh Pupuk Organik Cair dan Hormon Giberelin Terhadap Pertumbuhan dan Produksi Benih Kacang Hijau (Vigna radiata L.)

One of the efforts to increase the growth and production of mung bean seeds can be done by applying NASA POC and GA3 hormones. This research was conducted to determine the effect of giving NASA Liquid Organic Fertilizer (POC) and giving the hormone Gibberellin (GA3) to increasing growth and seed production of mung bean (Vigna radiata L.). This trial was carried out in August-November 2022, at the Jember State Polytechnic agricultural land. The experimental design used in this study was a factorial Randomized Completed Block Design (RBD) consisting of two factors and repeated 3 times. The first factor was the NASA POC concentration (P), consisting of 5 ml/l (P1), 10 ml/l (P2), and 15 ml/l (P3). The second factor was the concentration of Gibberellins (G), consisting of 125 ppm (G1), 150 ppm (G2), and 175 ppm (G3). The results obtained were then analyzed using the F test or ANOVA (Analysis of Variance) and then the DMRT test was carried out. The treatment of the NASA POC application had a very significant effect (**) on the parameter number of productive branches. The best result was the P3 treatment (2.93 branches). The treatment with the hormone GA3 (Giberelin) had a very significant effect (**) on the parameters of plant height at 28 hst the best result was the G2 treatment (26.37 cm) and had a significant effect (*) on the parameters of plant height at 14 hst with the best treatment results G2 (12.72cm). The interaction between the application of NASA POC and the GA3 hormone had a significant effect (*) on the parameters of the amount of production per hectare with the best treatment interaction, namely P3G2 (738.35 kg)

Pengaruh Konsentrasi dan Interval Waktu Aplikasi POC NASA terhadap Produksi Benih Gambas (Luffa acutangula L.)

Gambas (Luffa acutangula L.) has several benefits as a treatment for jaundice, swollen lymph nodes, and diuretics. This study aims to determine the interaction between concentration and time interval of NASA POC application on gambas seed production. This research was conducted at the Jember State Polytechnic Experimental Field from August to November 2022. This study used factorial randomized group design (RGD) which was repeated 3 times. The first factor is the concentration of NASA POC consisting of K1 (1 ml/L), K2 (2 ml/L), K3 (3 ml/L). The second factor is the application time interval consisting of W1 (once every 3 days), W2 (once every 6 days), W3 (once every 9 days), W4 (once every 12 days). The data were statistically analyzed using ANOVA, if the results showed significantly different effects then continued with the DMRT test at 5%. The results showed that the treatment of NASA POC concentration and application time interval each gave a significantly different effect on the parameters of plant length, fruit weight per plant, number of seeds per plant, and seed production per plot

Aplikasi Pupuk Sp-36 dan Organik Cair Terhadap Pertumbuhan Bibit Asal Setek Kopi Robusta (Coffea canephora pierre)

The significant increase in coffee production every year needs to be balanced with the provision of planting materials in the form of quality seeds and seedlings to meet these needs. The purpose of this study was to determine the effect of fertilizer application. The purpose of this study was to determine the effect of SP-36 and liquid organic fertilizer on the growth of Robusta coffee cuttings. The research was conducted in September 2022 – November 2022 at the Jember State Polytechnic nursery which is located at Jl. Mastrip, Krajan Timur, Sumbersari, Kec. Sumbersari, Jember Regency, East Java. The design used was factorial randomized completely block design (RCBD) with 2 factors and 3 replications. The first factor was the dose of SP-36 fertilizer which consisted of 3 levels, namely D₁ ( 4 g/plant), D₂ (8 g/plant), D₃ (12 g/plant). The second factor was the POC concentration of the coffee husks which consisted of 3 levels, namely K₁ (30%), K₂ (40%), K₃ (50%). Data were analyzed using the ANOVA test and continued with the DMRT (Duncan’s Multiple Range Test) with a level of 5%. The results showed that the treatment with SP-36 and liquid organic fertilizer had no significant effect on the parameters of shoot length, number of leaves, leaft length, leaf width, root length. The interaction between dose and concentration had a significantly different effect on the parameter number of leaves aged 6 MSP.

PENGARUH KONSENTRASI DAN INTERVAL WAKTU PEMBERIAN PUPUK ORGANIK CAIR AZOLLA TERHADAP PERTUMBUHAN DAN HASIL TANAMAN PAKCOY Varietas Nauli (Brassica rapa chinensis L.)

The aim of the research was to determine whether there was a real interaction effect of Azolla POC concentration and the time interval of POC administration on the yield and growth of Pakcoy plants. The research used a Randomized Group Design (RAK) arranged factorially including 2 factors which were repeated 3 times. Factor I is the nutrient dose of Azolla liquid organic fertilizer which consists of 3 levels 4 namely D1: 0 ml/1 water, D1: 2 ml/l water, D2: 4 ml/l water, D3: 6ml/l water and Factor II is Time interval for application of 3 level Azolla liquid organic fertilizer. S1: Application time interval 2 days, S2: Application time interval 4 days, S3: Application time interval 6 days. Plant height (cm) was observed at 0, 7, 14, 21, 28, 35 HST, measured using a meter. The number of leaves at 1, 3, 5, 7 and 9 WAP and leaf width at 0, 7, 14, 21, 28, 35 HST were measured using a tape measure. Accumulated fruit weight per plant (grams) The wet fruit weight of Pokcoy plants is determined by weighing all parts of the plant (roots, stems, leaves). Plants were weighed one by one using an analytical balance. Observational data were analyzed using Analysis of Variance (ANOVA) with a level of α = 0.05 and if there were significant differences between treatments then a further test was carried out using the DMRT test (Duncan's Multiple Range Test) at a level of α = 0.05. The results of research that have been carried out have concluded that there is a real interaction between the concentration of Azolla liquid organic fertilizer (D) and the time interval for POC application on the growth and yield of Pak Choy plants. The best treatment combination for plant height variables; number of leaves; leaf area is the D2S2 treatment, namely the combination treatment of azolla POC concentration of 4 ml/L and the POC application time interval of 4 days, while for plant fresh weight the best combination is D2S3, namely the combination treatment of 6 ml Azolla POC concentration and 4 day POC application time interval with weight. fresh plants amounting to 58.17 grams.

Vertical distributions of organic matter components in sea ice near Cambridge Bay, Dease Strait, Canadian Archipelago

Ice algae thriving within sea ice play a crucial role in transferring energy to higher trophic levels and influencing biogeochemical processes in polar oceans; however, the distribution of organic matter within the ice interior is not well understood. This study aimed to investigate the vertical distribution of organic matter, including chlorophyll a (Chl-a), particulate organic carbon and nitrogen (POC and PON), carbohydrates (CHO), proteins (PRT), lipids (LIP), and food material (FM), within the sea ice. Samples were collected from the bottom, middle, and top sections of the sea ice column near Cambridge Bay during the spring of 2018. Based on the δ13C signature, biochemical composition, and POC contribution of biopolymeric carbon (BPC), the organic substances within the sea ice were predominantly attributed to marine autotrophs. While the highest concentrations of each parameter were observed at the sea ice bottom, notable concentrations were also found in the upper sections. The average sea ice column-integrated Chl-a concentration was 5.05 ± 2.26 mg m−2, with the bottom ice section contributing 59% (S.D. = ± 10%) to the total integration. The column-integrated concentrations of FM, BPC, POC, and PON were 2.05 ± 0.39, 1.10 ± 0.20, 1.47 ± 0.25, and 0.09 ± 0.03 g m−2, respectively. Contributions of the bottom ice section to these column-integrated concentrations varied for each parameter, with values of 20 ± 6, 21 ± 7, 19 ± 5, and 28 ± 7%, respectively. While the bottom ice section exhibited a substantial Chl-a contribution in line with previous studies, significantly higher contributions of the other parameters were observed in the upper sea ice sections. This suggests that the particulate matter within the interior of the sea ice could potentially serve as an additional food source for higher trophic grazers or act as a seeding material for a phytoplankton bloom during the ice melting season. Our findings highlight the importance of comprehensive field measurements encompassing the entire sea ice section to better understand the distribution of organic carbon pools within the sea ice in the Arctic Ocean.

The seasonal variations in the interactions between rare earth elements and organic matter in tropical rivers

The escalation of global demands for critical minerals to facilitate the green energy transition creates emerging needs to better understand their environmental behaviours. Several nations recognize rare earth elements (REEs) as priority critical minerals and emphasize the necessity to evaluate their environmental mobility and potential effects on natural ecosystems and human health. Here, we investigated the seasonal variations in dissolved concentrations of REEs and their leachable fractions from suspended particles in samples collected bi-weekly from the Sai Gon and Dong Nai Rivers in Southern Vietnam. The investigation period extended over sixteen months, including a transition from wet to dry seasons. We reported significant mobility of REEs in the river waters during the wet season due to watershed runoff, especially in Sai Gon River with the occurrence of acid-sulphate soils. Dissolved REE concentrations in the dry season were significantly lower because of the interactions with organic-rich particles (up to 13% of particulate organic carbon, POC) mainly derived from phytoplankton materials. The conditional distribution coefficients (logKD from 5 to 7 for Pr) were proportional to POC content. The scavenging capacity of particulate organic matter also led to affect the fractionation between light REEs and heavy REEs in solution, and the characteristic Middle REE-enrichment patterns for the leachable REEs fraction. We also reported significant Eu anomalies (Eu/Eu* up to 7) in the Dong Nai River during the dry season and associated this observation with the decomposition of organic matter that previously accumulated Eu. However, further studies are required to confirm this hypothesis because of small reservoir effects; elevated Eu anomalies were observed in water samples with low dissolved Eu concentrations.

The Effect of Lamtoro Leaf POC and Tofu Liquid Waste on the Growth of Cayenne Chili (Capsicum frutescens)

Background: Liquid organic fertilizer is a fermented solution of organic plant residues, animal and human feces containing nutrients. Lamtoro and tofu liquid waste contain N, P, K, Mg, and Ca, which are suspected to have the potential for liquid organic fertilizer to increase the growth of cayenne pepper (C. frutescens). This study aims to determine the effect of giving POC from lamtoro leaves and tofu liquid waste on the growth of cayenne pepper (C. frutescens). Methods: This study used a completely randomized design (CRD) with two replications. POC volume 1:1 consisted of two-liter lamtoro leaf extract and 2-liter tofu liquid waste. The first factor is the volume concentration of POC with the respective concentrations of V0: 0%, V1: 10%, V2: 20%, and V3: 30%. The second factor is the time of spraying POC T1: 3 days interval and T2: 6 days interval. Parameters measured included plant height (cm), number of leaves (strands), and plant fresh weight (g). Results: 20% volume (V2) with three-day intervals (T1) gave the best results for plant height (20.10 cm), number of leaves (7.00 leaves), and plant fresh weight (11.50 g). 0% volume (V0) with an interval of 6 days (T2) gave the lowest yield on plant height (6.35 cm), number of leaves (3.00 leaves), and fresh weight of plants (3.00 leaves). Conclusions: Application POC from lamtoro leaves and tofu liquid waste can potentially increase the growth of cayenne pepper (C. frutescens).

Effect of Banana Stem Liquid Organic Fertilizer On Shallot Growth And Production (Allium ascalonicum L.)

The study-aims-to-determine-the-effect-of POC (liquid-organic-fertilizer) concentration of-banana-stems and-the interval of-application-of POC (liquid-organic-fertilizer) banana-stems on-the growth-and yield of onion plants. Conducted on private land, Tamanan Hamlet, Kepulungan Village, Gempol District, Pasuruan Regency from December 2022 to March 2023. Using factorial Group Randomized Design (RAK) and further tests using BNJ. The first-factor is-the concentration-of POC Banana Stems which-consists of-3 levels,-namely 100ml / L, 200ml / L, 300ml / L. while the-second-factor-is-the-interval-of-fertilizer-application-consisting of-3 levels,-namely-once-every-5-days,-once-every-10-days,-every-15-days, The-results-of variety analysis-show that-there is no-interaction between-the concentration of banana stem POC fertilizer and the time interval of POC fertilizer application. POC fertilizer concentration treatment has-a real-effect on observing plant-height, number-of bulbs and number-of POC fertilizer concentration treatment has-a real-effect on observing plant-height, number-of bulbs and number-of onion saplings, from banana stem POC fertilizer concentration treatment which can-produce-the-best wet weight-of shallots,-namely with a-concentration of 200ml/L.

Effect of Concentration Variation of Liquid Organic Fertilizer Application on the Growth of Mustard Plants

This study aimed to determine the effect of giving Infarm POC concentration variations on the growth of green mustard (Brassica juncea L). The research employed a completely randomized design (CRD) or randomized block design with 6 treatments and 5 replications, resulting in a total of 30 experimental units. The data collection method and mechanism used involved implementing a completely randomized design (CRD) with 6 types of treatment and 5 replications, leading to the cultivation of 30 mustard plants with POC concentrations ranging from 2% to 10%. The findings revealed that the application of POC fertilizer to mustard plants resulted in increased plant height, leaf count, and resistance to leaf pests. Notably, the POC concentration of 6% exhibited the most significant improvements in plant height and leaf count. However, to gain a more comprehensive understanding of the effectiveness of this POC, further research is necessary. It is recommended to extend the duration of the study until harvest to assess the weight and quality of the mustard greens, thereby providing more conclusive insights

Effect of Concentration and Interval of Giving Goat Urine Liquid Organic Fertilizer on Growth and Yield of Kailan (Brassica oleraceae L.)

The effect of the concentration and interval of giving goat urine liquid organic fertilizer on the growth and yield of kailan. This study aims to determine the interaction between the concentration and interval of giving goat urine liquid organic fertilizer on the growth and yield of kailan. This research was conducted at Ds. Jatikalang Krian started in February – April 2023. The study used a factorial Randomized Block Design (RBD) consisting of 2 factors with 3 replications. The first factor is the POC concentration which consists of 4 levels, namely concentration of 60 ml/L, concentration of 90 ml/L, concentration of 120 ml/L, concentration of 150 ml/L. The second factor is the administration interval which consists of 3 levels, including 3 days, 5 days, 7 days. The research results show that the concentration of goat urine liquid organic fertilizer has an effect on the observation of the number of leaves, leaf area, wet weight and dry weight. While the time interval treatment only affects the plant height parameter. The combination of goat urine liquid organic fertilizer treatment with the time interval of application showed a significant interaction on the observation of kailan leaf area. The best concentration of goat urine liquid organic fertilizer is giving 120 ml with an interval of application every 5 days.

Increased Growth and Yield of Peanuts (Arachis Hypogaea L.) with Tillage and Liquid Organic Fertilizer Fish Waste.

Peanut (Arachis hypogaea L.) is an important food commodity in Indonesia. The low production of peanuts in Riau Province has not been able to meet the people's need for peanuts. According to the Riau Province Food Crops Service (2022) the need for peanuts in Riau Province in 2019 is 8,516 tons, in 2020 the need for peanuts is 7,390 tons, and in 2021 the need for peanuts is 6,474 tons. This study aims to determine the effect and interaction between tillage and the application of fish waste liquid organic fertilizer (POC) and the single factor of both the growth and production of peanut plants and to get the best combination. The research was conducted using a split-plot design. The first factor as the main plot is tillage consisting of three levels, namely without tillage, minimum tillage, and maximum tillage. The second factor as a subplot was POC concentration consisting of four levels, without POC fish waste, 25% POC fish waste (250 ml POC + 750 ml water), 50% POC fish waste (500 ml POC + 500 ml water), and 50 % POC waste fish 75% (POC 750 ml + water 250 ml). Parameters observed included plant height, number of primary branches, flowering age, harvest age, number of pods, number of filled pods, seed production per plant, and weight of 100 seeds. The data obtained were analyzed statistically using analysis of variance and continued with Duncan's multiple range test at the 5% level using the SAS application. The results showed that the interaction of tillage and POC fish waste affected increasing plant height, number of primary branches, number of pods, number of filled pods, seed production per plant, and weight of 100 seeds.

Pengaruh POC Kombinasi Ampas Teh dan Sabut Kelapa terhadap Pertumbuhan Tanaman Cabai Rawit (Capsicum frutescens)

Cayenne pepper is one of the most popular horticultural crops, therefore fertilization can be used to increase the growth of chili plants. This research was conducted to determine the effect of the POC combination of tea dregs and coconut coir on the growth of cayenne pepper. The study was conducted using an experimental method using a completely randomized design (CRD) factorial pattern, namely POC concentration factor P0 (without giving POC), P1 (100 ml POC tea dregs and coconut coir + 900 ml water), P2 (200 POC tea dregs and coconut coir ml + 800 ml water), P3 (POC tea dregs and coconut coir 300 ml + 700 ml water) and time intervals H1 (3 days), H2 (6 days). Observational data were analyzed by ANOVA test with 5% confidence level. The parameters measured were plant height, number of leaves and wet weight. The best growth of cayenne pepper plants was in the P3H2 treatment (300 ml POC concentration + 700 ml water and 6 days interval) with an average plant height of 24.5 cm, 8 leaves and 14.5 g fresh weight.

THE INFLUENCE OF ADDING NUTRIENT ELEMENTS IN POC COMPOSITION ON ROOT AND LEAF GROWTH IN PAKCOY (Brassica rapa L.) PLANTS USING HYDROPONIC CULTIVATION SYSTEM

Planting with a hydroponic system is a technique for cultivating plants without using soil media, but instead using water as a medium for cultivating plants. So that planting with a hydroponic system can use narrow land. So a study was conducted with the aim of applying Liquid Organic Fertilizer (POC) with the Indonesian National Standard (SNI) in a hydroponic planting system by adding POC constituent nutrients to the growth of roots and leaves of mustard greens, by adding a dose POC concentration of 0%, 9%, 12%, and 15% by analyzing samples of 0, 7, 14, 21, 28, 35 days to obtain better growth of pakcoy vegetables. The best growth of pakcoy plant roots was obtained from a concentration of 15%, obtained a length of 18.75 cm. The best growth in leaf width of the oajcoy plant was obtained from a concentration of 0% or without POC, the leaf width was 5.75 cm.

Factors affecting broadscale variation in nearshore water-column organic carbon concentrations along the Great Barrier Reef

Organic carbon is a key energy source in marine food-webs, but elevated concentrations can have negative ecological impacts. We used 12 years of marine physiochemical, climate, and near-surface sea and meteorological condition data to investigate broadscale correlates and potential drivers of variability in dissolved and particulate organic carbon (DOC and POC, respectively) concentrations in coastal waters of the Great Barrier Reef (GBR), Australia. DOC concentrations were higher when salinity was lower, when the Southern Oscillation Index was more positive, and at times of greater northward wind speeds. POC concentrations were higher in shallower waters and were positively correlated with total suspended solids and chlorophyll a concentrations. Latitude was important for structuring variation in organic carbon concentrations, likely reflecting terrestrial material from rivers and broader marine processes. We conclude that variability in broadscale patterns of DOC concentrations in GBR coastal waters is likely most sensitive to material discharge from rivers as well as oceanographic and climatic processes and forcing. Variability in broadscale patterns of POC concentrations in coastal waters of the GBR is likely most affected by sediment resuspension and phytoplankton biomass accumulation.

Dynamic transport of particulate organic carbon in the Yellow River during dam-orientated Water-Sediment Regulation

The Yellow River has experienced prolific environmental changes from dam regulations that have significantly altered the downstream hydrologic regime, and transport of sediment and POC within the river-coast continuum. Here, we investigated the contrasting changes in sources and transport of POC from the lower Yellow River to the river mouth, at two different stages (e.g., Water vs. Sediment regulation) of dam operation - during the period of Water-Sediment Regulation Scheme (WSRS). Riverbed erosion downstream the Xiaolangdi Dam contributed the POC with more enriched δ13C stable isotopic values, along with those more isotopically depleted POC from riparian floodplains and the reservoir at the Water-regulation stage, when clear water was released from the reservoir. At the Sediment-regulation stage, muddy floodwaters were released, while soil-derived POC and fine-grained sediment released from the reservoir became dominant with evidently increasing POC content. The dispersal and distribution of river-laden POC at the river mouth were primarily modulated by the plume dynamics, as remotely impacted by dam regulation, in combination with the dynamic shear front. As a result, the POC distribution was confined within 10 km off the river mouth due to the rapid deposition of coarse-grained sediments. In contrast, the fine-grained sediment and more isotopically depleted POC, from modern sources (e.g., C3 vascular plant), were delivered to the far-field plume region. POC transport along the Yellow River-Estuary continuum exhibited complex behaviors, coupled with natural and dam-regulated drivers, on a variety of spatial-temporal scales. These findings provide important insights into dynamic linkages on how coastal carbon cycling can be significantly altered, remotely from the upstream dam regulations, in a large global river system.

Particulate organic matter in the Lena River and its delta: from the permafrost catchment to the Arctic Ocean

Abstract. Rapid Arctic warming accelerates permafrost thaw, causing an additional release of terrestrial organic matter (OM) into rivers and, ultimately, after transport via deltas and estuaries, to the Arctic Ocean nearshore. The majority of our understanding of nearshore OM dynamics and fate has been developed from freshwater rivers despite the likely impact of highly dynamic estuarine and deltaic environments on the transformation, storage, and age of OM delivered to coastal waters. Here, we studied particulate organic carbon (POC) dynamics in the Lena River delta and compared them with POC dynamics in the Lena River main stem along a ∼ 1600 km long transect from Yakutsk, downstream to the delta. We measured POC, total suspended matter (TSM), and carbon isotopes (δ13C and Δ14C) in POC to compare riverine and deltaic OM composition and changes in OM source and fate during transport offshore. We found that TSM and POC concentrations decreased by 70 % during transit from the main stem to the delta and Arctic Ocean. We found deltaic POC to be strongly depleted in 13C relative to fluvial POC. Dual-carbon (Δ14C and δ13C) isotope mixing model analyses indicated a significant phytoplankton contribution to deltaic POC (∼ 68 ± 6 %) and suggested an additional input of permafrost-derived OM into deltaic waters (∼ 18 ± 4 % of deltaic POC originates from Pleistocene deposits vs. ∼ 5 ± 4 % in the river main stem). Despite the lower concentration of POC in the delta than in the main stem (0.41 ± 0.10 vs. 0.79 ± 0.30 mg L−1, respectively), the amount of POC derived from Yedoma deposits in deltaic waters was almost twice as large as the amount of POC of Yedoma origin in the main stem (0.07 ± 0.02 and 0.04 ± 0.02 mg L−1, respectively). We assert that estuarine and deltaic processes require consideration in order to correctly understand OM dynamics throughout Arctic nearshore coastal zones and how these processes may evolve under future climate-driven change.

Divergent accumulation of amino sugars and lignins mediated by soil functional carbon pools under tropical forest conversion

Tropical primary forests are being destroyed at an alarming rate and converted for other land uses which is expected to greatly influence soil carbon (C) cycling. However, our understanding of how tropical forest conversions affect the accumulation of compounds in soil functional C pools remains unclear. Here, we collected soils from primary forests (PF), secondary forests (SF), oil-palm (OP), and rubber plantations (RP), and assessed the accumulation of plant- and microbial-derived compounds within soil organic carbon (SOC), particulate (POC) and mineral-associated (MAOC) organic C. PF conversion to RP greatly decreased SOC, POC, and MAOC concentrations, whereas conversion to SF increased POC concentrations and decreased MAOC concentrations, and conversion to OP only increased POC concentrations. PF conversion to RP decreased lignin concentrations and increased amino sugar concentrations in SOC pools which increased the stability of SOC, whereas conversion to SF only increased the lignin concentrations in POC, and conversion to OP just increased lignin concentrations in POC and decreased it in MAOC. We observed divergent dynamics of amino sugars (decrease) and lignin (increase) in SOC with increasing SOC. Only lignin concentrations increased in POC with increasing POC and amino sugars concentrations decreased in MAOC with increasing MAOC. Conversion to RP significantly decreased soil enzyme activities and microbial biomasses. Lignin accumulation was associated with microbial properties, whereas amino sugar accumulation was mainly associated with soil nutrients and stoichiometries. These results suggest that the divergent accumulation of plant- and microbial-derived C in SOC was delivered by the distribution and original composition of functional C pools under forest conversions. Forest conversions changed the formation and stabilization processes of SOC in the long run which was associated with converted plantations and management. The important roles of soil nutrients and stoichiometry also provide a natural-based solution to enhance SOC sequestration via nutrient management in tropical forests.

Differential effects of forest-floor litter and roots on soil organic carbon formation in a temperate oak forest

Both forest-floor litter and roots are known to be involved in the formation of soil organic carbon (SOC), but it remains elusive how the two contrasting types of plant carbon sources would differentiate in their effects on SOC. Here we used field-based soil mesocosms to study the responses of SOC components (i.e. mineral-associated organic C [MAOC], particulate organic C [POC], and dissolved organic C [DOC]) and pathways of production (i.e. plant-derived vs. microbial-derived C compounds) to multi-year treatments of forest-floor litter and roots in a temperate oak forest in central China. After eight years, the concentrations of both POC and MAOC were significantly higher in plots with presence of forest-floor litter than in those exclusive of both forest-floor litter and roots at the soil depth of 0–5 cm; roots predominantly affected POC but not the total SOC. The contributions from the forest-floor litter and roots to total SOC and its components were all non-additive; the plots with co-occurrence of forest-floor litter and roots had 49.7% less total SOC, 36.6% less POC, and 54.7% less MAOC, than the sum of the plots with only forest-floor litter or roots, at the soil depth of 0–5 cm. The concentrations of both lignin phenols and microbial biomass carbon (MBC) were significantly higher in plots with only forest-floor litter than in those exclusive of both forest-floor litter and roots down to a depth of 20 cm, and the plant-derived neutral sugars were significantly higher in plots with only forest-floor litter than in those exclusive of both forest-floor litter and roots at the soil depth of 0–10 cm. In contrast, the concentration of lignin phenols was significantly higher in plots with only roots than in those exclusive of both forest-floor litter and roots below the depth of 5 cm, and the concentrations of MBC and microbial-derived neutral sugars were higher in plots with only roots than in those exclusive of both forest-floor litter and roots at the soil depth of 0–10 cm. The plots with co-occurrence of forest-floor litter and roots had a significantly higher concentration of lignin phenols at all soil depths investigated, as well as higher concentrations of the plant- and microbial-derived neutral sugars and MBC at the soil depth of 0–5 cm, than those exclusive of both forest-floor litter and roots; the effects were all non-additive such that the plots with co-occurrence of forest-floor litter and roots had less plant- and microbial-derived C compounds than the sum of the values between the plots with only forest-floor litter and the plots with only roots. The contributions of amino sugars to SOC did not significantly respond to either the treatments with forest-floor litter and roots or soil depth, albeit variable MBC concentrations. In addition, our results show that the microbial-derived neutral sugars were positively correlated with plant-derived neutral sugars. Findings in this study provide empirical evidence on the primacy of forest-floor litter in SOC pool at the soil depth of 0–5 cm, and demonstrate the differential roles and contributions between forest-floor litter and roots in the pathways of SOC formation and spatial differentiation of carbon compounds.

Paired Synoptic and Long-Term Monitoring Datasets Reveal Decadal Shifts in Suspended Sediment Supply and Particulate Organic Matter Sources in a River-Estuarine System

The San Francisco Estuary, in central California, has several long-running monitoring programs that have been used to reveal human-induced changes throughout the estuary in the last century. Here, we pair synoptic records of particulate organic matter (POM) composition from 1990–1996 and 2007–2016 with more robust long-term monitoring program records of total suspended sediment (TSS) concentrations generally starting in the mid-1970s to better understand how POM and TSS sources and transport have shifted. Specifically, POM C:N ratios and stable isotope values were used as indicators of POM source and to separate the bulk POC pool into detrital and phytoplankton components. We found that TSS and POC sources have shifted significantly across the estuary in time and space from declines in terrestrial inputs. Landward freshwater and brackish water sites, in the Delta and near Suisun Bay, witnessed long-term declines in TSS (32 to 52%), while seaward sites, near San Pablo Bay, recorded recent increases in TSS (16 to 121%) that began to trend downwards at the end of the record considered. Bulk POM C:N ratios shifted coeval with the TSS concentration changes at nearly all sites, with mean declines of 12 to 27% between 1990–1996 and 2007–2016. The widespread declines in bulk POM C:N ratios and inferred changes in POC concentrations from TSS trends, along with the substantial declines in upstream TSS supply through time (56%), suggest measurable reductions in terrestrial inputs to the system. Changes in terrestrial TSS and POM inputs have implications for biotic (e.g., food web dynamics) and abiotic organic matter cycling (e.g., burial, export) along the estuarine continuum. This work demonstrates how human-generated environmental changes can propagate spatially and temporally through a large river-estuary system. More broadly, we show how underutilized monitoring program datasets can be paired with existing (and often imperfect) synoptic records to generate new system insight in lieu of new data collection.

Storm pulse responses of fluvial organic carbon to seasonal source supply and transport controls in a midwestern agricultural watershed

Storm events are the primary mechanisms of delivering fluvial organic carbon (OC) in both dissolved (DOC) and particulate (POC) forms but their sources and flow pathways can vary with seasonal land use and weather. Within the low relief and poorly drained landscapes of a predominantly agricultural watershed in Eastern Iowa, six storm events were monitored for DOC and POC concentrations over a two hydrological year period in order to investigate the export mechanisms, landscape connectivity, and hydro-climatological controls of fluvial OC under representative events and associated management practices. Event-driven dynamics favored POC over DOC, where POC accounted for 54–94 % of total OC export during events, highlighting a sampling-driven bias against POC in the absence of event monitoring. The disparity between POC and DOC export exhibited a seasonal effect, where the POC:DOC export ratio was low (1.3–1.7) for October events while June/July events yielded a much higher value (up to a value of 14.7). The relationships between event DOC and POC export, Normalized Difference Vegetation Index of landscapes, and antecedent wetness conditions suggest a strong interaction or competing influences between vegetation coverage and runoff-generation threshold. While we recognize the low statistical power of the limited data set (n = 6), the storm events could be binned into two clusters: a “bare soil” period and a crop “rapid growth” period. Specifically, intra-storm variations in OC concentration and concentration-discharge (C-Q) hysteresis patterns demonstrated a seasonally-dependent access to contributing OC sources, which can be viewed as the rapid liberation of DOC during the “bare soil” period, and a progressive leaching of terrestrial DOC during the “rapid growth” period. Although high resolution event monitoring of fluvial carbon is rare this work highlights the importance of such efforts to predict C sourcing and transformation in inland water systems under variable land use and across seasons.