Dynamics of solar-induced chlorophyll fluorescence (SIF) and its response to meteorological drought in the Yellow River Basin.

Solar-induced chlorophyll fluorescence (SIF) has been used since its discovery to characterize vegetation photosynthesis and is an effective tool for monitoring vegetation dynamics. Its response to meteorological drought enhances our comprehension of the ecological consequences and adaptive mechanisms of plants facing water scarcity, informing more efficient resource management and efforts in mitigating climate change. This study investigates the spatial and temporal patterns of SIF and examines how vegetation SIF in the Yellow River Basin (YRB) responds to meteorological drought. The findings reveal a gradual southeast-to-northwest decline in SIF across the Yellow River Basin, with an overall increase-from 0.1083 W m-2µm-1sr-1 in 2001 to 0.1468 W m-2µm-1sr-1 in 2019. Approximately 96% of the YRB manifests an upward SIF trend, with 75% of these areas reaching statistical significance. The Standardized Precipitation Evapotranspiration Index (SPEI) at a time scale of 4 months (The SPEI-4), based on the Liang-Kleeman information flow method, is identified as the most suitable drought index, adeptly characterizing the causal relationship influencing SIF variations. As drought intensified, the SPEI-4 index markedly deviated from the baseline, resulting in a decrease in SIF values to their lowest value; subsequently, as drought lessened, it gravitated towards the baseline, and SIF values began to gradually increase, eventually recovering to near their annual maximum. The key finding is that the variability of SIF with SPEI is relatively pronounced in the early growing season, with forests demonstrating superior resilience compared to grasslands and croplands. The responsiveness of vegetation SIF to SPEI can facilitate the establishment of effective drought early warning systems and promote the rational planning of water resources, thereby mitigating the impacts of climate change.

Investigating the long-term response of plateau vegetation productivity to extreme climate: insights from a case study in Qinghai Province, China.

Over the past three decades, there has been a significant global climate change characterized by an increase in the intensity and frequency of extreme climate events. The vegetation status in Qinghai Province has undergone substantial changes, which are more pronounced than other regions in the Qinghai-Tibet Plateau. However, a clear understanding of the response characteristics of plateau vegetation to extreme climate events is currently lacking. In this study, we investigated the response of net primary productivity (NPP) to different forms of extreme climate events across regions characterized by varying levels of aridity and elevation gradients. Specifically, we observed a significant increase in NPP in relatively arid regions. Our findings indicate that, in relatively arid regions, single episodes of high-intensity precipitation have a pronounced positive effect (higher correlation) on NPP. Furthermore, in high-elevation regions (4000-6000 m), both the intensity and frequency of precipitation events are crucial factors for the increase in regional NPP. However, continuous precipitation can have significant negative impacts on certain areas within relatively wet regions. Regarding temperature, a reduction in the number of frost days within a year has been shown to lead to a significant increase in NPP in arid regions. This reduction allows vegetation growth rate to increase in regions where it was limited by low temperatures. Vegetation conditions in drought-poor regions are expected to continue to improve as extreme precipitation intensifies and extreme low-temperature events decrease.

Temporal and spatial variation characteristics of surface water area in the Yellow River Basin from 1986 to 2021.

The Yellow River Basin is short of water resources. The dynamic monitoring of surface water area is helpful to clarify the distribution and change trend of water resources in this area. It is of great scientific significance to deeply understand the impacts of climate change and human activities on water resources and ensure the ecological security of the basin. Based on the Google Earth Engine (GEE) cloud platform, we analyzed the spatial variations of surface water area in the Yellow River Basin from 1986 to 2021 by using the mixed index algorithm, and revealed the driving factors of surface water area change in the Yellow River Basin. The results showed that the overall recognition accuracy of the water extraction algorithm based on mixing index was 97.5%. Compared with available water data products, the proposed algorithm can guarantee the integrity of the whole water area to a certain extent. The surface water area in the upper, middle, and lower reaches of the Yellow River Basin was 71.7%, 18.4%, and 9.9% of the total surface water area, respectively. From 1986 to 2021, the surface water area of the basin showed an overall upward trend, with a total increase of 3163.6 km2. The surface water area of the upper, middle, and downstream regions increased by 72.0%, 22.4%, and 5.6%, respectively. The increase of precipitation was the main reason for the increase of water area, with a contribution of 55%. Vegetation restoration and construction of water conservancy projects had increased the water area of the basin. The intensification of human water extraction activity reduced the water area of the basin.

Deep Learning-Based Model Significantly Improves Diagnostic Performance for Assessing Renal Histopathology in Lupus Glomerulonephritis.

Background: Assessment of glomerular lesions and structures plays an essential role in understanding the pathological diagnosis of glomerulonephritis and prognostic evaluation of many kidney diseases. Renal pathophysiological assessment requires novel high-throughput tools to conduct quantitative, unbiased, and reproducible analyses representing a central readout. Deep learning may be an effective tool for glomerulonephritis pathological analysis. Methods: We developed a murine renal pathological system (MRPS) model to objectify the pathological evaluation via the deep learning method on whole-slide image (WSI) segmentation and feature extraction. A convolutional neural network model was used for accurate segmentation of glomeruli and glomerular cells of periodic acid-Schiff-stained kidney tissue from healthy and lupus nephritis mice. To achieve a quantitative evaluation, we subsequently filtered five independent predictors as image biomarkers from all features and developed a formula for the scoring model. Results: Perimeter, shape factor, minimum internal diameter, minimum caliper diameter, and number of objects were identified as independent predictors and were included in the establishment of the MRPS. The MRPS showed a positive correlation with renal score (r = 0.480, p < 0.001) and obtained great diagnostic performance in discriminating different score bands (Obuchowski index, 0.842 [95% confidence interval: 0.759, 0.925]), with an area under the curve of 0.78-0.98, sensitivity of 58-93%, specificity of 72-100%, and accuracy of 74-94%. Conclusion: Our MRPS for quantitative assessment of renal WSIs from MRL/lpr lupus nephritis mice enables accurate histopathological analyses with high reproducibility, which may serve as a useful tool for glomerulonephritis diagnosis and prognosis evaluation.

[Effects of shrub patch pattern on runoff and sediment yield]. / çŒæœ¨æ–‘å—æ ¼å±€å¯¹äº§æµåŠäº§æ²™è¿‡ç¨‹çš„å½±å“.

Understanding the changes of runoff, sediment transport, and hydrodynamic parameters of slopes under the influence of landscape patch coverage and connectivity is of great significance for revealing the hydrodynamic mechanism and hydrological connectivity of slope soil erosion process. In this study, the changes of runoff, sediment transport and hydrodynamic parameters of downhill surface in different coverage levels (0%, 20%, 40%, 60%, 90%) and different connectivity modes (vertical path, horizonal path, S-shaped path, random patches) of shrublands were analyzed by field artificial simulated rainfall test. The results showed that, with the increases of shrub cove-rage, runoff yield and sediment yield decreased exponentially. When the coverage increased to more than 60%, the capacity of shrubs to reduce runoff and sediment became stable. With the increases of shrub coverage, flow velocity, flow depth, Reynolds number, Froude number, stream power, and flow shear resistance significantly decreased, while Manning's roughness coefficient and Darcy-Weisbach resistance coefficient increased significantly. When shrub coverage increased to more than 60%, there was no significant difference in the eigenvalues of hydraulic parameters. The runoff rate under the four connectivity modes followed the order of vertical path > S-shaped path > horizonal path > random patches. The sediment rate was the largest in the vertical path, followed by the S-shaped path, and the horizonal path was not significantly different from the random patches. The path with poor connectivity (horizonal path, random patches) exhibited stronger resistance of hydraulic transmission and poor hydraulic sedimentation capacity than the well-connected path (vertical path, S-shaped path). Our results could provide important theoretical basis for soil erosion control on the Loess Plateau and high-quality development of the Yellow River basin.

[Determination of 10 pyrethroid pesticide residues in tea by gas chromatography-tandem mass spectrometry coupled with multi-plug filtration cleanup].

A method for the determination of 10 pyrethroid pesticide residues in tea was established by multi-plug filtration cleanup (m-PFC) method combined with gas chromatography-tandem mass spectrometry (GC-MS/MS). Different extraction solvents (acetonitrile, acetone and ethyl acetate) and extraction methods (immersion without water and immersion with water) were compared. The effect of two kinds of QuEChERS pipes and m-PFC column on the purification of tea extracts and the pesticide recoveries were compared. The results showed that the tea samples could be extracted most efficiently when using acetonitrile without immersion in water. The m-PFC column had a good purification effect on the tea extract and could guarantee a high recovery rate. Good linear relationships were observed for the 10 pyrethroid pesticides, and the correlation coefficients (R2) were greater than0.9980. The average recoveries for the 10 pyrethroid pesticides were in the range of 87.5%-111.3% at four spiked levels, and the RSDs were in the range of 2.1%-8.9%. The LODs and LOQs were 0.001-0.015 mg/kg and 0.003-0.05 mg/kg, respectively. The method was applied to the determination of the 10 pyrethroid pesticides in 50 tea samples. The detection rate of the pyrethroid pesticides was 48%, but all the pesticide residues were below the national standard limits. Compared with the traditional QuEChERS and solid phase extraction methods, this method has the advantages of operational simplicity as well as high accuracy and good precision. The establishment of this method provides a new strategy for the rapid detection of pyrethroid pesticide residues in tea.

A label-free aptasensor for turn-on fluorescent detection of ochratoxin A based on aggregation-induced emission probe.

A novel label-free fluorescence aptasensor used for the detection of ochratoxin A (OTA) is presented in this study. When aggregated on the surface of DNA aptamer, aggregation-induced emission (AIE) fluorescence probe presents turn-on fluorescence property. The method proposed in this article was based on an AIE probe, 4, 4-(1E,1E)-2, 2-(anthracene-9, 10-diyl) bis (ethene-2, 1-diyl) bis (N, N, N-trimethylbenzenaminium iodide) (DSAI). With OTA present, the aptamer will combine with OTA and the conformation of the aptamer will switch to an antiparallel G-quadruplex from the initial random coil, which obstructs its digestion by Exo I. After the solution is added with DSAI, DSAI will aggregate on the surface of the aptamer/OTA complex and produces a strong emission. In the range of 5 to 500 ng · ml-1 OTA concentrations, the fluorescence increases with a linear logarithm relationship. The detection limit is 1.9 ng · ml-1. This method was used to detect OTA in spiked real samples, with recoveries and RSDs in the range of 92.2% to 106.3%, and 2.7% to 5.2%, respectively.

Hydrologic alteration and possible underlying causes in the Wuding River, China.

Understanding hydrological alteration of rivers and the potential driving factors are crucial for water resources management in the watershed. This study analyzed the daily runoff time series at six gauging stations during 1960-2016 in Wuding River basin, northwestern China. The Mann-Kendall test and Lee-Heghinian method were employed to detect the temporal trends and abrupt changes in annual streamflow. The flow duration curve (FDC) and the index of hydrologic alteration (IHA)/Range of Variability Approach (RVA) were applied to assess the daily streamflow and degree of hydrologic alteration (DHA). In addition, we analyzed the changes of index of hydrological connectivity (IC) and reservoirs/dams (RI) in 1990, 1995, 2000 and 2015 in the basin. The relationship between IC, RI and DHA were assessed to investigate the potential influences of land use changes and constructions of reservoirs/dams on hydrological alteration. The results indicated that annual streamflow at five stations showed significant downward trends (p < 0.01) from 1960 to 2016, and an abrupt changing point appeared in the beginning of 1970s in Wuding River basin. Exception is Qingyangcha station without significant changes, and Hanjiamao station with changing point in 1967. FDC analysis indicated that both high and low flow indices reduced greatly. The integral DHA were higher than 70% at all the stations in the Wuding River basin, suggesting great variation in the magnitude, duration, frequency, timing and rate of change of daily streamflow. Both IC value and RI had close relationship with DHA, implying that DHA was highly affected by land use changes and dams/reservoirs constructions, and was more sensitive to the land use change (p < 0.01). This study provides good insight to understand the effects of soil and water conservation measures on hydrological regime.

A label-free fluorometric aptasensor for adenosine triphosphate (ATP) detection based on aggregation-induced emission probe.

Based on Aggregation-Induced Emission (AIE), the development of a label-free, simple and sensitive fluorometric aptasensor for adenosine triphosphate (ATP) detection is described. With ATP present, the aptamers will combine with ATP and the conformation of the aptamer will switch from a random coil to an antiparallel G-quadruplex, which impedes the digestion by exonuclease I (Exo I). Addition of 4,4 -(1E,1E)-2,2-(anthracene-9,10-diyl) bis (ethene-2,1-diyl) bis (N,N, N-trimethyl-benzenaminium iodide) (DSAI) into the solution will cause aggregation of DSAI on the surface of the aptamer/ATP complex and consequently give rise to strong emission. Additionally, a good linear relationship was observed under optimized conditions between the fluorescence intensities and the logarithm of ATP concentrations (R2 = 0.9908). The established aptamer sensor was highly sensitive and exhibited a low limit of detection of 32.8 nM, with superior specificity for ATP. It was also used in the quantification of ATP levels in human serum samples and demonstrated satisfactory recoveries in the scope of 93.2%-107.6%. The cellular ATP assay results indicated that the developed method can be used for monitoring ATP concentrations in cell extracts without the interference of other substances in the cells. This method offers several advantages such as simplicity, rapidity, low cost and excellent selectivity, which make it hold great potential for the detection of ATP in bioanalytical and biological studies.

Rotundic acid induces Cas3-MCF-7 cell apoptosis through the p53 pathway.

In the present study, the functions and mechanisms of rotundic acid (RA) underlying its induction of apoptosis in caspase-3-transfected MCF-7 human breast cancer cells (Cas3-MCF-7 cells) were investigated. RA induced apoptosis in Cas3-MCF-7 cells more efficiently compared with that in MCF-7 cells transfected with control plasmid. The results from an MTT assay demonstrated that RA effectively inhibited Cas3-MCF-7 cell viability in a dose-dependent manner and induced cell apoptosis via caspase-3 activity within 12 to 48 h. Western blotting and fluorescence-activated cell sorting demonstrated that RA initiated Cas3-MCF-7 cell apoptosis via p53 activation. The silencing of the p53 gene in the Cas3-MCF-7 cell line led to decreased RA-induced Cas3-MCF-7 cell caspase-3 activity and cell apoptosis. Collectively, the results of the present study indicate that caspase-3 serves a critical function in rotundic acid-induced apoptosis, and suggest that caspase-3 deficiency may contribute to the chemotherapy-resistance of breast cancer. Reconstitution of caspase-3 sensitizes MCF-7 breast cancer cells to chemotherapy. RA has the potential for development as a novel drug combined with reconstitution of caspase-3 gene therapy for the treatment of human breast cancer with caspase-3 deficiency.

[Determination of 50 pesticide residues in fruits by gas chromatography-tandem mass spectrometry].

A method for the determination of 50 pesticides in fruits by gas chromatography-tandem mass spectrometry (GC-MS/MS) was developed. The three QuEChERS methods (the original one without buffer, the one with acetate buffer and the one with citrate buffer) were compared. The purification effects of primary secondary amine (PSA) and SinChERS-Nano column were also investigated. The results showed that the acetate buffer and the citrate buffer had positive influence on the extraction compared to the original method without buffer, and there was no significant difference between the two methods using buffers. Finally, the QuEChERS method using acetate buffer was chosen as the extraction method. By comparing the purification effect images and the total ion current (TIC) chromatograms, SinChERS-Nano column was revealed to have a better cleaning effect, and was chosen for cleanup. The recoveries of methamidophos, acephate, omethoate, chlorothalonil and dicofol were in ranged of 71.2%-129.2%, the other 45 pesticides were ranged from 79.1% to 122.3%. The limits of detection (LODs) were 0.3-3.0 µ g/kg and the limits of quantification (LOQs) were 1.0-10.0 µ g/kg. The method is rapid and suitable for the screening of the 50 pesticide residues in citrus, grapes and other fruit samples.

Rotundic acid enhances the impact of radiological toxicity on MCF-7 cells through the ATM/p53 pathway.

Although radiation therapy is a powerful anticancer modality, radiation- induced stress response and gene expression with adaptive resistance may severely compromise the effectiveness of radiation. The function of rotundic acid (RA) on inducing apoptosis in the human breast cancer cell line MCF-7 has been investigated in a previous study. In the present study, the combined effect of chemotherapy and radiotherapy on reducing side effects was examined. The results of an MTT assay revealed that radiation (0.5, 2 and 10 Gy) effectively inhibit MCF-7 cell viability in a dose-dependent manner, consistent with the effects of RA (2, 5 and 12.5 µM). Interestingly, a lower dose of radiation (1 Gy) combined with RA (5 µM) exhibited a greater inhibition efficiency compared with a high dose of radiation alone. Flow cytometry revealed that radiation combined with RA induced the apoptosis of MCF-7 cells. Using western blotting, it was demonstrated that radiation induced the expression of ataxia-telangiectasia mutated (ATM) and p53 protein, and that RA enhanced this effect. On examining the potential underlying mechanism, it was revealed that radiation and RA combined induce Bcl-2-associated X protein expression and cell apoptosis in MCF-7 cells. An ATM inhibitor was able to restore the effect of radiation and RA on inducing MCF-7 cell apoptosis. These results suggest that the ATM/p53 pathway directly participates in radiation and RA-induced apoptosis in MCF-7 cells. RA has the potential for development as a novel drug for the treatment of human breast cancer combined with radiation therapy, given that the combined side effects are reduced.

Therapeutic effect of chitosan on CCl4­induced hepatic fibrosis in rats.

Chitosan is a linear polysaccharide that is made by treating the chitin shells of shrimp and crustaceans with an alkaline substance, for example sodium hydroxide. Due to its unique physical and chemical properties, chitosan has a wide range of applications in the medical field. Currently, there are no effective treatments for liver fibrosis; therefore, the aim of the present study was to investigate the therapeutic effect of chitosan in a CCl4­induced hepatic fibrosis (HF) rat model. The serum levels of aspartate transaminase (AST), alanine transaminase (ALT) and alkaline phosphatase (ALP) were measured by ELISA. Collagen (COL) 3 and α­smooth muscle actin (SMA) expression levels in the rat liver were detected by reverse transcription­semiquantitative polymerase chain reaction and western blotting, respectively. The results demonstrated that treatment with chitosan significantly improved HF, by decreasing the serum levels of AST, ALT, and ALP; improving liver histology; and decreasing the expression levels of COL3 and α­SMA. Chitosan may offer an alternative approach for the clinical treatment of HF.

Reduced sediment transport in the Chinese Loess Plateau due to climate change and human activities.

The sediment load on the Chinese Loess Plateau has sharply decreased in recent years. However, the contribution of terrace construction and vegetation restoration projects to sediment discharge reduction remains uncertain. In this paper, eight catchments located in the Loess Plateau were chosen to explore the effects of different driving factors on sediment discharge changes during the period from the 1960s to 2012. Attribution approaches were applied to evaluate the effects of climate, terrace, and vegetation coverage changes on sediment discharge. The results showed that the annual sediment discharge decreased significantly in all catchments ranging from -0.007 to -0.039 Gt·yr-1. Sediment discharge in most tributaries has shown abrupt changes since 1996, and the total sediment discharge was reduced by 60.1% during 1997-2012. We determined that increasing vegetation coverage was the primary factor driving the reductions in sediment loads since 1996 and accounted for 47.7% of the total reduction. Climate variability and terrace construction accounted for 9.1% and 18.6% of sediment discharge reductions, respectively.

Assessing response of sediment load variation to climate change and human activities with six different approaches.

Understanding the relative contributions of climate change and human activities to variations in sediment load is of great importance for regional soil, and river basin management. Considerable studies have investigated spatial-temporal variation of sediment load within the Loess Plateau; however, contradictory findings exist among methods used. This study systematically reviewed six quantitative methods: simple linear regression, double mass curve, sediment identity factor analysis, dam-sedimentation based method, the Sediment Delivery Distributed (SEDD) model, and the Soil Water Assessment Tool (SWAT) model. The calculation procedures and merits for each method were systematically explained. A case study in the Huangfuchuan watershed on the northern Loess Plateau has been undertaken. The results showed that sediment load had been reduced by 70.5% during the changing period from 1990 to 2012 compared to that of the baseline period from 1955 to 1989. Human activities accounted for an average of 93.6 ±â€¯4.1% of the total decline in sediment load, whereas climate change contributed 6.4 ±â€¯4.1%. Five methods produced similar estimates, but the linear regression yielded relatively different results. The results of this study provide a good reference for assessing the effects of climate change and human activities on sediment load variation by using different methods.

Developing a flippase-mediated maker recycling protocol for the oleaginous yeast Rhodosporidium toruloides.

OBJECTIVES: To establish a recombinase flippase (FLP) and flippase recognition target (FRT) system-mediated protocol for post-integration excision of exogenous DNA fragments in the oleaginous yeast Rhodosporidium toruloides. RESULTS: Binary vectors were constructed to harbor FLP expressing cassette together with the hygromycin-resistance marker. Results showed that R. toruloides transformants produced FLP, but failed to mediate removal of the bleomycin-resistance marker within two FRT sites. When FLP was fused with a native nuclear localization signal (NLS) peptide, the system was found functional. Moreover, R. toruloides recombinant strains expressing the NLS-fused FLP under the control of PADH2, an promoter of alcohol dehydrogenase 2 gene (RHTO_03062), were obtained to realize homologous recombination upon growing in glucose-deficient medium. CONCLUSIONS: We have devised a homologous recombination method for R. toruloides based on the FLP/FRT system, which may facilitate further metabolic engineering and designing advanced cell factories for value-added chemicals.

Expression of phosphotransacetylase in Rhodosporidium toruloides leading to improved cell growth and lipid production.

Microbial lipids (MLs) are potential alternatives to vegetable oils and animal fats for production of biofuels and oleochemicals. It remains critical to improve ML production efficiency and costs for further commercial development. In the present study, we overexpressed a gene encoding phosphotransacetylase (Pta) in the oleaginous yeast Rhodosporidium toruloides for enhanced cell growth and lipid production. Compared with the parental strain R. toruloides NP11, the engineered strain NP-Pta-15 showed significant improvement in glucose consumption, cell growth and lipid accumulation when cultivated under nitrogen limited conditions in an Erlenmeyer flask as well as a stirred tank bioreactor. The introduction of Pta may establish an additional acetyl-CoA formation route by utilization of acetylphosphate. Our results should inspire more engineering efforts to facilitate the economic viability of ML technology.

Exchanging the order of carotenogenic genes linked by porcine teschovirus-1 2A peptide enable to optimize carotenoid metabolic pathway in Saccharomyces cerevisiae.

The yeast Saccharomyces cerevisiae serves as a promising host for the production of a wide range of chemical compounds and fuels. Currently, simultaneous expression of several genes could be achieved via the use of 2A viral peptides, yet detailed characterizations to assess the discrepancy of different orders of genes linked by 2A peptides are rarely sufficient. In this study, we investigated the effects of the order of genes linked by porcine teschovirus-1 2A (P2A) peptide on the metabolic pathway in S. cerevisiae. A heterologous carotenoid biosynthetic system involving nine kinds of polycistronic expression of codon-optimized carotenogenic genes GGPPS, CARB and CARRP from Blakeslea trispora was introduced into S. cerevisiae. The order of genes in the polycistronic segment was exchanged; ß-carotene production by engineered yeasts was significantly different. The highest ß-carotene yield was achieved in transformants carrying the plasmid, with CARB as the first gene in the polycistronic construct regardless of the location of GGPPS, CARRP. In addition, we found that ß-carotene production was coupled with the growth in engineered strain with the highest ß-carotene content during the shake flask fermentation and fed-batch fermentation. A novel microbial heterologous carotenoid production system was established by optimizing the order of genes linked by P2A peptide sequences in a polycistronic expression construct. The observation of the importance of the order in a polycistronic construct may be used to increase yields in other P2A peptide-containing expression systems.

Prediction of aboveground grassland biomass on the Loess Plateau, China, using a random forest algorithm.

Grasslands are an important component of terrestrial ecosystems that play a crucial role in the carbon cycle and climate change. In this study, we collected aboveground biomass (AGB) data from 223 grassland quadrats distributed across the Loess Plateau from 2011 to 2013 and predicted the spatial distribution of the grassland AGB at a 100-m resolution from both meteorological station and remote sensing data (TM and MODIS) using a Random Forest (RF) algorithm. The results showed that the predicted grassland AGB on the Loess Plateau decreased from east to west. Vegetation indexes were positively correlated with grassland AGB, and the normalized difference vegetation index (NDVI) acquired from TM data was the most important predictive factor. Tussock and shrub tussock had the highest AGB, and desert steppe had the lowest. Rainfall higher than 400 m might have benefitted the grassland AGB. Compared with those obtained for the bagging, mboost and the support vector machine (SVM) models, higher values for the mean Pearson coefficient (R) and the symmetric index of agreement (λ) were obtained for the RF model, indicating that this RF model could reasonably estimate the grassland AGB (65.01%) on the Loess Plateau.