Effectiveness assessment of soil conservation measures in reducing soil erosion in Baiquan County of Northeastern China by using (137)Cs techniques

Assessment of soil erosion in the Upper Citarum watershed for sustainability of the Saguling reservoir: unmixing model approach

The Citarum watershed and the Saguling reservoir are vital natural resources in Indonesia, affecting the livelihood of West Java and the DKI Jakarta population. This study aimed to assess the soil erosion in the Upper Citarum watershed and identify its source. The study used the fallout radionuclide technique, geochemical tracers, and an unmixing model to measure soil erosion and the contribution of suspended sediment sources due to erosion. Soil bulk transects and surface soil were sampled using a coring tool on the Ciwidey and Cisangkuy sub-watersheds. Riverbank and suspended sediment samples were collected from tributaries and rivers. With 137Cs, 40% of the samples had values below the minimum detectable activity, and vice versa for 210Pbex, all samples are detectable. For mitigation, bare land needs to be recovered due to its erosion (25.6 t ha-1 year-1) exceeding the tolerance erosion value (17 t ha-1 year-1). Statistically, Mg and Na were the most appropriate composite tracers for suspended sediment contribution. The unmixing model predicted the sediment contributors from bare land (58%), the riverbank (32.7%), and plantation land (9.3%). Proper land conservation could reduce sediment supply by almost 14.7% and extend the reservoir's life. This is the first study to report the feasibility of the unmixing model in Indonesia.

Behaviour of 137Cs and 210Pb inventory at three candidate reference sites for erosion study in the upstream Citarum watershed area, West Java, Indonesia

The fallout radionuclide (FRN) analysis needs a reference site (RS) inventory to determine erosion and sedimentation in the study area. The investigated area is in the upstream Citarum watershed, West Java, Indonesia. Twenty-seven corings and 22 scrap samples have been prepared well and measured using HPGe gamma spectroscopy. The data below the minimum detectable activity (MDA) was found for ¹³⁷Cs in RS6 cor 4 and 7 (<0.16 ± 0.08 Bq kg^-1). MDA quantification implies that the inventory below MDA eroded greater than its maximum value (76.02 tons ha^-1 a^-1). The comparison ¹³⁷Cs inventory in this study is lower than the three estimation models; however, the inventory of Mt. Papandayan is closer to the model. This study found the depth percentage of 20-30 cm using the proportion of 0-20 cm/0-30 cm ratio and predicted the portion of the existence of ¹³⁷Cs and ²¹⁰Pb_ex in the 20-30 cm in the bulk sample. The highest H₀ (142.04 kg m^-2), the relaxation length λ, and proportion of 20% of ¹³⁷Cs in 20-30 cm depth imply that ¹³⁷Cs inventory activity is possibly deeper than 30 cm. This study recommends that Mt. Papandayan could be the alternative RS for the upstream Citarum watershed.

Shelterbelt farmland-afforestation induced SOC accrual with higher temperature stability: Cross-sites 1 m soil profiles analysis in NE China

Shelterbelt farmland afforestation has been well-reported in its wind-break and climate regulation function, but less is on underground-soil organic carbon (SOC) sequestration and environmental stability. In this paper, we collected 180 soil samples from soil depths of 1 m (0-20, 20-40, 40-60, 60-80, 80-100 cm) in the farmland and neighbor shelterbelts in Songnen Plain, northeastern China. The sample plots covered six regions in the study area. SOC concentration and respiration decomposition rate, Q₁₀ (temperature sensitivity), H_s (humidity sensitivity) were determined in the laboratory cultivation. Soil properties (N, P, K, electrical conductivity-EC, pH) and geographic-climate factors (multiple-year mean annual temperature and precipitation, MAT&MAP; temperature and precipitation during sampling month, MT &MP) were used to reveal the underlying reason for the changes in soil carbon sequestration. The results showed no significant difference in SOC respirational decomposition rate between farmland and shelterbelt forests but a 15.8% higher SOC concentration in shelterbelt forests (p < 0.05). The poplar shelterbelts reduced the Q₁₀ value by 15.4% (p < 0.05), with deeper soils a more significant reduction in Q₁₀. With soil moisture increases, both shelterbelt forests and farmland showed an obvious respiration pattern of first-increasing-then-decreasing. No significant H_s (linear gradients) differences were found in farmland and shelterbelt forests. Partitioning of the RDA ordination-based variation showed that SOC stability (H_s and Q₁₀) of farmland was more affected by geo-climate. In contrast, the SOC stability of shelterbelt forests was greatly influenced by soil properties. Our findings manifest that the above-mentioned SOC changes can improve shelterbelt forest carbon sequestration function by prolonging the SOC lifespan in soil by at least 7% and SOC concentration by >15%. This should be included in the future to assess the underground soil carbon impact of Three-North shelterbelts in China and provide data supports for the estimation of similar forest stands in other parts of the world.

137Cs estimates of soil erosion rates in a small catchment on a channelized river floodplain in the lower reaches of Yangtze River, China

Channelization significantly affects soil erosion in river floodplains. The object of this study was to use ¹³⁷Cs as a tracer to determine the ¹³⁷Cs inventory and derived soil erosion rates under various land use types in a catchment on channelized river floodplain in the lower reaches of Yangtze River, China. Sampling was carried out to establish a¹³⁷Cs reference inventory in a 70-year old paddy field located on the shoulder-slope of a local hill. The mean reference inventory of ¹³⁷Cs was 1275 Bq m^-2, whereas the ¹³⁷Cs inventory within the catchment ranged from 284 to 1150 Bq m^-2 and the soil erosion rates from -33.3 to -2.4 t ha^-1 yr^-1, respectively. The dominated land use of paddy in cultivated soils contributed relative low soil erosion. Bamboo and castanea mollissima were preferential for local land uses in uncultivated soils in comparison with woodland and Pinnus massoniana. The rates of soil erosion rates in old tea garden were higher than that in new tea garden. Overall, severe soil erosion and no deposition in the entire catchment occurred in the entire catchment due to the human-induced channelization in the 1970s. Our results suggest that restricting farmland being returned to tea plantations, thereby maintaining the current land use types would reduce soil erosion in river floodplain in the future.

Evaluación de los servicios ecosistémicos proporcionados por las terrazas agrícolas

Las terrazas agrícolas son ampliamente utilizadas en todo el mundo desde la antigüedad. Su interés paisajístico es innegable y algunas de ellas forman parte del Patrimonio Mundial de la UNESCO. Son prácticas muy eficaces para la conservación del suelo y el agua a través del control de la escorrentía y la erosión, y proporcionan a los agricultores y a la sociedad importantes Servicios Ecosistémicos (SE). Presentamos un estudio basado en ejemplos de terrazas documentados en detalle en la base de datos WOCAT (World Overview of Conservation Approaches and Technologies), complementado con una revisión de la literatura científica sobre los impactos de las terrazas, con el objetivo de evaluar los múltiples SE que proporcionan. Los resultados muestran que los SE más importantes proporcionados por la construcción de terrazas están relacionados con servicios de regulación como el control de la erosión, escorrentía y otros riesgos naturales externos. Además, la presencia de terrazas favorece servicios de aprovisionamiento como el suministro de alimentos, fibras, y cantidad y calidad del agua. Se constatan las funciones ambientales, geomorfológicas e hidrológicas de las terrazas, así como la mejora de la calidad de vida de los habitantes. Sin embargo, los avances tecnológicos en la agricultura han llevado al abandono de este tipo de construcciones, con importantes riesgos de erosión y pérdida de SE. Nuestra evaluación destaca la importancia de preservar y restaurar las terrazas como parte de la agricultura regenerativa, con múltiples beneficios para el funcionamiento de los paisajes culturales y, en definitiva, para la sociedad.