Bibliometric Analysis of Soil Fertility Evaluation Papers Based on Core Journals in CNKI

[Objectives]This study was conducted to deeply analyze the research status in the field of soil fertility evaluation.[Methods]With the core journals of Peking University included in CNKI database from 2002 to 2021 as the research object,papers were searched in the advanced search mode using SU=‘soil fertility’and SU=‘evaluation’as the retrieval subject terms and analyzed by the bibliometric research method,from three perspectives,namely,the annual number of papers published,the number of papers issued by authors and the number of highly cited papers.[Results]A total of 891 first authors issued 990 papers related to soil fertility evaluation in total from 2002 to 2021,with an average annual number of papers published at about 50,and the number of published papers showed a trend of rapidly increasing first and then gradually stabilizing.The top 13 authors published 3-4 papers,including Yang Xiaojuan,Chen Haisheng and Li Xinju(4 papers)ranking first.The top 10 papers with the highest citation frequency were published in 9 journals,respectively covering ecology,forestry,agriculture,geography,engineering and other fields,which shows that there are many kinds of journals focusing on the research field of soil fertility evaluation.[Conclusions]The results can provide reference for further research on soil fertility evaluation.

Book Retrieval Method Based on QR Code and CBIR Technology

It is the development trend of library information management,which applies the mature and cutting-edge information technology to library information retrieval.In order to realize the rapid retrieval of massive book information,this paper proposes a book retrieval method combining QR code with image retrieval technology.This method analyzes the visual features of book images,design a book image retrieval method based on boundary contour and regional pixel distribution features,and realizes the association retrieval of book information combined with the QR code,so as to improve the efficiency of book retrieval.The experimental results show that,the books can be retrieved effectively through the boundary contour and regional pixel distribution features,the book information can be displayed through QR code,readers can be provided with fast and intelligent massive book retrieval services.

Study on Improvement of Soil Porosity

In order to further improve soil porosity and improve soil physical properties,the raw materials,formula and application methods of soil amendment were optimized,and the pH and porosity of yellow soil were compared and analyzed after application of soil amendment.The results showed that the application of amendments increased soil pH and porosity.The results will provide the scientific basis for the improvement of soil porosity.

Equilibrium Climate Response of the East Asian Summer Monsoon to Forcing of Anthropogenic Aerosol Species

We used an online aerosol-climate model to study the equilibrium climate response of the East Asian summer monsoon （EASM） to increases in anthropogenic emissions of sulfate, organic carbon, and black carbon aerosols from 1850 to 2000. Our results show that each of these aerosol species has a different effect on the EASM as a result of changes in the local sea-land thermal contrast and atmospheric circulation. The increased emission of sulfate aerosol leads to a decrease in the thermal contrast between the land and ocean, a southward shift of the East Asian subtropical jet, and significant northerly wind anomalies at 850 hPa over eastern China and the ambient oceans, markedly dampening the EASM. An increase in organic carbon aerosol results in pronounced surface cooling and the forma- tion of an anomalous anticyclone over the oceans north of 30°N. These effects cause a slight increase in the sea-land thermal contrast and southerly flow anomalies to the west of the anticyclonic center, strengthening the northern EASM. An increase in organic carbon emission decreases the sea-land thermal contrast over southern China, which weakens the southern EASM. The response of the summer 850-hPa winds and rainfall over the East Asian monsoon region to an increase in black carbon emission is generally consistent with the response to an increase in organic carbon. The increase in black carbon emission leads to a strengthening of the northern EASM north of 35°N and a slight weakening of the southern EASM south of 35°N. The simulated response of the EASM to the increase in black carbon emission is unchanged when the emission of black carbon is scaled up by five times its year 2000 levels, although the intensities of the response is enhanced. The increase in sulfate emission primarily weakens the EASM, whereas the increases in black carbon and organic carbon emissions mitigate weakening of the northern EASM.

Comparing independent climate-sensitive models of aboveground biomass and diame ter grow th with their compatible simultaneous model system for three larch species in China

Accurate estimate of tree biomass is essential for forest management.In recent years,several climate-sensitive allometric biomass models with diameter at breast height(D)as a predictor have been proposed for various tree species and climate zones to estimate tree aboveground biomass(AGB).But the allometric models only account for the potential effects of climate on tree biomass and do not simultaneously explain the influence of climate on D growth.In this study,based on the AGB data from 256 destructively sampled trees of three larch species randomly distributed across the five secondary climate zones in northeastern and northern China,we first developed a climate-sensitive AGB base model and a climate-sensitive D growth base model using a nonlinear least square regression separately.A compatible simultaneous model system was then developed with the climate-sensitive AGB and D growth models using a nonlinear seemingly unrelated regression.The potential effects of several temperature and precipitation variables on AGB and D growth were evaluated.The fitting results of climatic sensitive base models were compared against those of their compatible simultaneous model system.It was found that a decreased isothermality([mean of monthly(maximum temperatureminimum temperature)]/(Maximum temperature of the warmest month-Minimum temperature of the coldest month))and total growing season precipitation,and increased annual precipitation significantly increased the values of AGB;an increase of temperature seasonality(a standard deviation of the mean monthly temperature)and precipitation seasonality(a standard deviation of the mean monthly precipitation)could lead to the increase of D.The differences of the model fitting results between the compatible simultaneous system with the consideration of climate effects on both AGB and D growth and its corresponding climate-sensitive AGB and D growth base models were very small and insignificant(p>0.05).Compared to the base models,the inhere nt correlation of AGB with D was taken into account effectively by the proposed compatible model system developed with the climate-sensitive AGB and D grow th models.In addition,the compatible properties of the estimated AGB and D were also addressed substantially in the proposed model system.