Northeast Institute of Geography and Agroecology, Chinese Academy Of Sciences
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Evaluation and Improvement of SMOS and SMAP Soil Moisture Products for Soils with High Organic Matter over a Forested Area in Northeast China
No full textSoil moisture (SM) retrieval from SMOS (the Soil Moisture and Ocean Salinity mission) and SMAP (the Soil Moisture Active/Passive mission) passive microwave data over forested areas with required accuracy is of great significance and poses some challenges. In this paper, we used Ground Wireless Sensor Network (GWSN) SM measurements from 9 September to 5 November 2015 to validate SMOS and SMAP Level 3 (L3) SM products over forested areas in northeastern China. Our results found that neither SMOS nor SMAP L3 SM products were ideal, with respective RMSE (root mean square error) values of 0.31 cm(3)/cm(3) and 0.17 cm(3)/cm(3). Nevertheless, some improvements in SM retrieval might be achievable through refinements of the soil dielectric model with respect to high percentage of soil organic matter (SOM) in the forested area. To that end, the potential of the semi-empirical soil dielectric model proposed by Jun Liu (Liu's model) in improving SM retrieval results over forested areas was investigated. Introducing Liu's model into the retrieval algorithms of both SMOS and SMAP missions produced promising results. For SMAP, the RMSE of L3 SM products improved from 0.16 cm(3)/cm(3) to 0.07 cm(3)/cm(3) for AM (local solar time around 06: 00 am) data, and from 0.17 cm(3)/cm(3) to 0.05 cm(3)/cm(3) for PM (local solar time around 06: 00 pm) data. For SMOS ascending orbit products, the accuracy was improved by 56%, while descending orbit products improved by 45%
Soil organic carbon fractions are affected by different land uses in an agro-pastoral transitional zone in Northeastern China
No full textSoil organic carbon (SOC) consists of various C fractions with different stabilities and chemical compositions that are differently affected by changes in land use. A better understanding of the responses of different C fractions to land uses is vital for maintaining soil quality and mitigating global warming. Using data from a short-term land use experiment in northeastern China, this paper investigated the effect of five land uses, corn cropland (Corn), alfalfa grassland (Alfalfa), artificial grassland of Lyemus chinensis (AG), Lyemus chinensis grassland for mowing (AG+Mow) and restored grassland (RG), on the dynamics of total SOC and four SOC fractions with increasing degrees of oxidizability at 0 to 50 cm depths. The results show that land use had a significant effect (P<0.05) on the total SOC and SOC fractions of very labile C (F1), labile C (F2) and less labile C (F3), while the difference in recalcitrant C (F4) was less pronounced. SOC in the study area was characterized by a predominantly very labile C fraction, and the percentages of Fl to total SOC were more than 40% for all land uses. Compared with Corn, the treatments AG + Mow, AG and RG decreased the percentage of Fl to SOC (by 4.49%, 6.53% and 3.55%, respectively) and increased the percentages of F2 (by 3.32%, 2.77% and 6.60%, respectively) and F3 (by 4.47%, 3.46% and 0.3%, respectively) to SOC. These findings suggest that land -use type is a major factor that influences soil C fractions and that labile C fractions contribute a large part of the total SOC. In addition, grassland colonization of croplands improves soil C sequestration in northeastern China. (C) 2016 Published by Elsevier Ltd
Spatial and temporal changes in daily temperature extremes in China during 1960-2011
No full textBased on daily maximum and minimum temperature data from 437 weather stations over China, this study examined the spatiotemporal change of temperature extremes in China from 1960 to 2011. Results showed a general downward trends in the occurrence of cold days (TX10) and nights (TN10) (base period 1961-1990), but upward tendency on the occurrence of warm days (TX90) and nights (TN90), the temperatures of coldest day (TXn), coldest night (TNn), warmest day (TXx), and warmest night (TNx) in China and most climate regions. At the national scale, TX10 and TN10 have significantly decreased by -1.89 and -4.39 days/decade, and TX90 and TN90 have significantly increased by 2.49 and 4.72 days/decade from 1960 to 2011. The national average trends for TXn, TNn, TXx, and TNx were 0.28, 0.54, 0.17, and 0.27 A degrees C/decade, respectively. The temporal changes of extremes indices showed that changes in cold (warm) relative indices may be primarily related to that of corresponding winter (summer) T-max and T-min, respectively. Regionally, the magnitudes of changes in extreme indices decreased from the north to south of China. However, we found significant increase of warm extremes, especially warm days and nights in Southeast China. For most climate regions, the trend magnitudes in warm days/nights were larger than that in cold days/nights, but the trend in coldest temperature was much higher than that in warmest temperature. The trend magnitudes in minimum temperature indices were larger than those based on daily maximum temperature, explaining the faster increase of T-min than T-max in China
Monitoring spatiotemporal changes of marshes in the Sanjiang Plain, China
No full textThe marshes have undergone dramatic loss in the Sanjiang Plain since the 1950s. This paper analyzed the spatiotemporal changes of the marshes using the transition probabilities index, loss rate, and landscape indices. We also used a trajectory analysis method to trace every location of marshes over multiple points in time and to quantitatively estimate the impact of human activities on the marsh changes since the 1950s. This study indicates that the marsh area declined sharply by 79.4% (approximately 2.99 million ha) from 1954 to 2015. A large area of marsh was reclaimed as cultivated land from 1954 to 2015. The changes in the related landscape indices showed the large-scale loss of the marsh area and marsh fragmentation in the study period. Human activities were the dominant factor (87.86%) that influenced the marsh changes in the Sanjiang Plain during the last 60 years compared with natural factors. These findings can provide valuable information for better understanding wetlands changes and implementing sustainable management strategies for wetlands (such as wetland restoration). (C) 2017 Elsevier B.V. All rights reserved
Spatial patterns of car sales and their socio-economic attributes in China
No full textUsing data from the Economic Advisory Center of the State Information Center (SIC), we examined the spatial patterns of car sales in China at the prefectural level in 2012. We first analyzed the spatial distributions of car sales of different kinds of automakers (foreign automakers, Sino-foreign joint automakers, and Chinese automakers), and then identified spatial clusters using the local Moran's indexes. Location quotient analysis was applied to examine the relative advantage of each type of automaker in the local markets. To explain the variations of car sales across cities, we collected several socioeconomic variables and conducted regression analyses. Further, factor analysis was used to extract independent variables to avoid the problem of multicollinearity. By incorporating a spatial lag or spatial error in the models, we calibrated our spatial regression models to address the spatial dependence problem. The analytical results show that car sales varied significantly across cities in China, and most of the cities with higher car sales were the developed cities. Different automakers exhibit diverse spatial patterns in terms of car sales volume, spatial clusters, and location quotients. The scale and incomes factor were extracted and verified as the two most significant and positive factors that shape the spatial distributions of car sales, and together with the spatial effect, explained most of the variations of car sales across cities
Using Landsat images to quantify different human threats to the Shuangtai Estuary Ramsar site, China
No full textMultiple human activities can impose significant negative effects on wetland ecosystem. This study aimed to identify and quantify the human threats on the Shuangtai Estuary Ramsar site (SERS) by means of detecting wetland landscape changes using Landsat images from 1988 to 2014. Land-cover changes induced by agricultural reclamation, urban expansion, petroleum industry, aquaculture, and the increases in transportation land were identified using an object-oriented classification method and a decision tree. Human-triggered wetland conversions and landscape metrics-characterized wetland changes were documented in order to assess the protection effectiveness after this wetland was listed as a national nature reserve (1988) and a Ramsar site with international importance (2005). Results indicate that wetlands area at this Ramsar site decreased from 127,526 ha in 1988-117,805 ha in 2005, 113,705 ha in 2014 at an annual averaged loss rate of 531.6 +/- 72 ha/yr. The only two vegetated wetland types, Phragmites australis and Suaeda heteroptera, have lost 4788 ha and 12,856 ha, respectively. Aquaculture ponds increased by 9715 ha, and almost all were transformed from natural wetlands. The landscape metrics used in this study show notable fragmentation trend of wetland as a result of the expansion of transportation lands. Multiple human activities occupied large areas of various wetland types. Compared to agricultural reclamation and urbanization, wetland changes at the study site were affected primarily by the development of aquaculture and petroleum industry. Obvious wetland loss and fragmentation determined by the analysis of Landsat images suggests that the protection effect has been relatively low in spite of the fact that the SERS is a national natural reserve and Ramsar site. As an internationally critical rest habitat for migration waterfowl, ecological degradation of the SERS and severe human threats create great challenges for ecosystem managements. This study also indicates that the protection effectiveness of other costal wetland should also be assessed using remote sensing to objectively track the conservation or restoration of these areas. (C) 2016 Elsevier Ltd. All rights reserved
Agrobacterium deltaense sp nov., an endophytic bacteria isolated from nodule of Sesbania cannabina
No full textA Gram-negative, non-spore-forming, aerobic rods, strain YIC4121(T) was isolated from root nodule of Sesbania cannabina grown in Dongying (Yellow River Delta), Shandong Province, PR China. Based on phylogenetic analysis of 16 S rRNA gene sequences, strain YIC4121(T) was assigned to the genus Agrobacterium with 99.7, 99.3, 99.0, 98.8 and 98.7% sequence similarities to Agrobacterium radiobacter LMG140(T), A. pusense NRCPB10(T), A. arsenijevicii KFB 330(T), A. nepotum 39/7(T) and A. larrymoorei ATCC51759(T). Analysis of the concatenated housekeeping genes (recA-atpD-glnII), showed lower sequence similarities (<= 94.6%) between strain YIC4121(T) and other recognized Agrobacterium species. Strain YIC4121(T) shared whole-genome average nucleotide identities (ANI) 87.94, 91.27 and 77.42%, with A. pusense NRCPB10(T), A. radiobacter LMG140(T) and A. larrymoorei ATCC51759(T). The predominant cellular fatty acids were C-19:0 cyclo omega 8c, summed feature 2 - (C-12:0 aldehyde/unknown 10.9525), summed feature 8 (C-18:1.omega c/ C-18:1 omega 6c), C-16:0 3 OH and C-16:0. The G + C content of strain - YIC4121(T) was 59.80 mol%. Tween 80, lactulose, citric acid, alpha-ketoglutaric acid, glycyl- L-glutamic acid and 2, 3butanediol could not be utilized as carbon source, distinguishing strain YIC4121(T) from the other related species. Based on the distinctly genetic and phenotypic dissimilarity, a novel species Agrobacterium deltaense sp. nov. is proposed with YIC4121(T) (= HAMBI 3654(T) = LMG 2928(T)) as the type strain
Scaling of soil carbon, nitrogen, phosphorus and C:N:P ratio patterns in peatlands of China
No full textInspired by the importance of Redfield-type C : N : P ratios in global soils, we looked for analogous patterns in peatlands and aimed at deciphering the potential affecting factors. By analyzing a suite of peatlands soil data (n = 1031), mean soil organic carbon (SOC), total nitrogen (TN) and total phosphorous (TP) contents were 50.51%, 1.45% and 0.13%, respectively, while average C : N, C : P and N : P ratios were 26.72, 1186.00 and 46.58, respectively. C : N ratios showed smaller variations across different vegetation coverage and had less spatial heterogeneity than C : P and N:P ratios. No consistent C : N : P ratio, though with a general value of 1245 : 47 : 1, was found for entire peatland soils in China. The Northeast China, Tibet, Zoig Plateau and parts of Xinjiang had high soil SOC, TN, TP, and C:P ratio. Qinghai, parts of the lower reaches of the Yangtze River, and the coast zones have low TP and N : P ratio. Significant differences for SOC, TN, TP, C : N, C : P and N : P ratios were observed across groups categorized by predominant vegetation. Moisture, temperature and precipitation all closely related to SOC, TN, TP and their pairwise ratios. The hydrothermal coefficient (RH), defined as annual average precipitation divided by temperature, positively and significantly related to C : N, C : P and N : P ratios, implying that ongoing climate change may prejudice peatlands as carbon sinks during the past 50 years in China