Abstract:The key to application of the Indicator Kriging method is the choice of an appropriate threshold. Three soil salinity thresholds, i.e. 1.0 g kg^-1, 2.0 g kg^-1 and 3.0 g kg^-1 were set for the study on variograms, prediction probability and spatial distribution of the prediction probability of soil salinity in the top layer (0~20 cm) of a farmland in relation to soil salinity threshold in Yucheng, typical of the salt-affected soil amelioration zone in the Huang-Huai-Hai Plain. Results show（1）regardless of threshold values, salt contents in all soils are all moderate in spatial autocorrelation; however, with threshold declining, soil salinity intensifies in spatial structure and its model of variation function increases in accuracy; therefore, taking into account the accuracy of the indicator variogram model, the soil salt content of 1.0 g kg^-1 is the optimal threshold for assessment of the risk of salinization of the studied region; （2）both the maximum value and the mean value of prediction probability increase with rising salinity threshold, which may serve as reference for selecting thresholds for different objects of soil salinization risk assessment; and（3）predictive distribution of probability prediction of soil salinity using different thresholds demonstrates certain spatial regularity and similarity; high probability is concentrated mainly in the west part of the studied region, while low probability in the east. Distribution of the prediction probability of soil salt content is closely related to landform and topography and distribution of rivers in the study area.

Abstract:After comparative analysis of the distribution characteristics of soil water and salt in farmlands ( 3 cotton fields and 1 orchard) and their shelterbelts in drip irrigation prevailing Kalamiji Oasis in the lower reaches of Tarim River, Northwest China through comparative tests and field monitoring, effects of the current drip irrigation pattern on farmlands within forest networks and their shelterbelts and main factors affecting salt-water dynamics in the soil within the forest network were studied and analyzed with the following conclusions obtained. ⑴ In Kalamiji oasis, the groundwater table in the fields lowers at a rate of 0.5 m a^-1 as a result of popularization of drip irrigation and varies seasonally; it is relatively shallow in non-irrigation season and relatively deep in irrigation season; and over 1 m deeper in the latter than in the former. (2) As the impact of drip irrigation on soil never goes deeper than 80 cm, the irrigation supplies little water, almost nil, to groundwater, while the roots of farmland shelterbelt have to go deep into the soil to absorb water, thus leading to significantly lower soil water content in the shelterbelt than in farmland (p<0.01). (3) The current irrigation rate, 5 250 m³ hm^-2 a^-1 in the cotton field and 7 000 m³ hm^-2 a^-1 in the orchard are adequate to keep the soil (0~60 cm) low in salinity and basically satisfying the requirements of farmland desalination; but, in shelterbelt land soil salinity is obviously higher or 2～3 times higher than in farmland (p<0.01); surface accumulation of soil salts is apparent; as a result, the conductivity is 79.3%, 77.1%, 80.6% and 88.4% higher in loamy forest land, sandy forest land, clayey forest land 1 and clayey forest land 2 than in farmlands, respectively. (4) Comparison in soil water and salt contents between shelterbelt lands shows that the difference in depth of the groundwater table is the main factor for difference in soil water and salt content and consequently, forest lands, high in water content, are high in salinity, and vice versa in the 0~150 cm soil layer.

Abstract:In order to study effects of organic pollutants in irrigation water on soil physical properties, tracts of farmland in the Jiaokou Irrigation Zone, Shaanxi, that had long been irrigated with water polluted with organic contaminants were selected as subject in the study and some other tracts of farmland that had long been irrigated with unpolluted groundwater were set as control. They were both the same in soil condition and under the same climate condition and the same cultivation system. Composition of soil aggregates and microaggregates were measured by dry sieving and wet sieving, separately for analysis of variation of, dominant fractions of aggregates. Results show that long-term irrigation with organic-polluted water significantly decreased the contents of macro–aggregates (>10 mm) and micro-aggregates (<0.25 mm), but increased the content of “(quality) dominant aggregates” (1~5 mm). Correlation analysis shows that the content of water-stable aggregates was positively related with the content of soil organic matter, but insignificantly related to the mechanical composition of water-stable aggregates. Long-term irrigation with organic-polluted water also improved soil aggregate stability and enhanced soil aggregation, but reduced aggregate dispersion coefficient, an indication that soil structure was effectively improved. The findings prove that organic pollutants in irrigation water significantly improves soil structure and properties.

Abstract:In order to determine effects of structure characteristics and shear strength of red soil on soil detachment, relationships of soil detachment rate with soil aggregate characteristics and shear strength of the red soil were studied through indoor simulated erosion experiment with concentrated flows. Eight typical types of red soils were chosen for the study. Results show that aggregate stability index (As) integrated main mechanisms of aggregate breakdown, and was found to be well related with soil detachment rate under different flow shear stresses; A positive linear relationship was observed between saturated soil shear strength (σ_s) and critical flow shear stress (τ_c) in concentrated flow. By introducing As and σ_s into the WEPP (Water Erosion Production Project) model of rill erosion, a prediction equation of red soil detachment rate was established with a good correlation coefficient ( R ² = 0.8871). The study provides a new approach to research on erosion mechanisms of red soil, which is of great significance to perfection of the physical process model of soil erosion.

Abstract:The composition and fractal dimension (D) of micro-aggregates in 0~20 cm soil layer were studied on a long-term fertilized field under wheat-maize cropping rotation in North China Plain, and relationships of soil fertility with compositional proportion of characteristic soil micro-aggregates (PCM, ＜20 μm/(250~20) μm), ratio of the content of ＜20 μm particle-size to the content of 2 000~20 μm particle-size content in soil micro-aggregates determination (RMD, ＜20 μm/(2 000~20) μm) and D were evaluated. The long-term fertilization experiment was designed to include 7 treatments: fertilizer NPK (NPK), organic manure (OM), half organic manure with chemical fertilizer NPK (1/2OMN), chemical fertilizer NP (NP), chemical fertilizer PK (PK), chemical fertilizer NK (NK) and control (CK). After 18 years of fertilization, all the treatments, except CK showed lower values of PCM, RMD and D, and higher nutrients content and enzyme activity. Among the fertilization treatments, Treatment OM was the lowest in PCM、RMD and D, followed by Treatment 1/2OMN, and the treatments with chemical fertilizers. Balanced application of fertilizers (Treatment NPK) was lower in PCM、RMD and D than imbalanced use of fertilizers (Treatments NP, PK, and NK). PCM, RMD and D were closely related to crop yield, soil organic matter, hydrolysis N, and enzyme activity. The findings indicate that the use of organic manure alone or in combination with fertilizer NPK and balanced application of fertilizer NPK are key to improving soil micro-aggregate composition, decreasing PCM, RMD and D, and increasing soil nutrient preserving and supplying capacity; and that PCM, RMD and D can be used as integrated quantitative indexes to evaluate the soil fertility under a long-term fertilization cropping system.

Abstract:Soil is an important organic carbon pool, of which any small change may lead to great variation of CO₂ concentration in the atmosphere. Soil aggregates have the function of physical protection of soil organic carbon. Application of barnyard manure can not only increase the content of soil organic carbon, but also promote formation of soil aggregates, which is of great significance to sequestrating and maintaining soil organic carbon. In this experiment the wet sieving method was used to isolate and fractionate aggregates. It was found after a 8-year stationary field experiment on application rate of manure that application of an appropriate amount of manure significantly increased soil mean weight diameter (MWD), and improved soil structure, but excessive application of manure significantly reduced the content of >2 000 µm aggregates while increased that of 2 000~250 µm aggregates. In Aquic-brown soil, soil organic carbon was mainly distributed in 250~53 µm and 2 000~250 µm fractions of aggregates, accounting for about 73.7%~78.5% of the total soil organic carbon content. With increased input of organic carbon, soil organic carbon was mainly stored in the 2 000~250 µm fraction of aggregates. Manure application significantly sped up renewal of the >2 000 µm fraction of aggregates. The content of light fraction organic carbon in the soil increased with increased manure input, and accounted for 22.1% of the total soil organic carbon in the soil applied with a high rate of manure. The ability of the soil to sequestrate organic carbon is limited, and apparent phenomena of hierarchical saturation are observed. It is, therefore, concluded that in soils deficient in organic matter, it is of great significance to apply organic manure, whereas in soils high in organic matter it is advisable to put in less organic carbon.

Abstract:In order to explore CO₂ concentration in the sand layer of the mobile sand dunes of the Alxa Desert, and its influence atmospheric CO₂ and its role in the global carbon cycling, the research team utilized infrared CO₂ monitor to observe diurnal variation of CO₂ concentrations in the 19 holes drilled in mobile sand dunes of the desert. Results show that the CO₂ concentration in the air was lower than that in the sands 1 m, 2 m, 3 m, 4 m or 5 m deep, which indicates that the mobile sand dunes with rare plants release CO₂ into the atmosphere both at night and in the daytime during the warm season, acting as CO₂ sources. In the sand layer 5 m deep in the profile, the CO₂ concentration is markedly higher than that in the air, suggesting that the potential of CO₂ release is very big. In the extremely arid part of the Alxa Desert, CO₂ concentration is usually higher in the sand layer 2 m deep than in the layers 1 m, 3 m, 4 m or 5 m deep, but with some individual exceptions. Diurnal variation of CO₂ concentration in the area follows a specific law in all the layers, showing a curve of saddle shape from 08:00 am to 07:00 am the next day, and a significant positive relationship with the temperature in the profile. In that region, the sand layer higher in moisture content is significantly higher in CO₂ concentration, which indicates that moisture content in the sand layers is the major factor determining CO₂ concentration in the layer.

Abstract:Methane fluxes from rice fields in the Taihu Lake Region were studied using static-chamber/gas chromatography. In-situ observation was carried out in paddy fields different in treatment or cultivation pattern, separately, i.e. Treatments NN (no N control), FP (farmer’s practice), YE (10%～15% higher in yield and 20%～30% higher in N use efficiency), HY (30%～40% higher in yield), HE (30%～50% higher in N use efficiency), and IE (currently integrated management for the same as FP in yield and 20%～30% higher in NUE). It was found that distinctive seasonal variation existed of methane emission from rice fields. Methane fluxes increased after transplanting peaking at the vegetative growth stage early or late depending on treatments and then declined rapidly after mid-season drainage. The cumulative methane emission observed during the period from transplanting to the heading stage accounted for 93%～98% of the seasonal total. Methane fluxes differed among different treatments. Treatment HY with organic manure emitted as high as 258.8 kg hm^-2, obviously higher than Treatments NN, FP, YE, and IE without organic manure. However, CH₄ emission per unit grain yield did not differ much among treatments, averaging CO₂ 0.60 kg kg^-1, which indicates that cultivation patterns with higher rice production would not substantially enhance CH₄ emission. Treatment YE was the lowest in CH₄ emission per unit grain yield, being CO₂ 0.49 kg kg^-1, thus deserving wide extension due to increased grain yield, improved N use efficiency and decreased global warming potential simultaneously.

Abstract:An incubation experiment was conducted to evaluate the effects of temperatureand soil types on soil net nitrification rate. Four temperatures (15, 20, 25, and 30℃) were set, and three types of soils (black soil, chao soil, and red soil) with high and low content of soil organic matter (SOM) were selected. Urea N was applied at an equivalent rate of 200 mg kg^-1 soil. All soil nitrification rates increased along with incubation temperature within the range of 15~30℃, and the relationship between accumulated soil NO₃-N contents and accumulation temperature of incubation (T×t, ℃×d) could be fitted by a single exponential model. Under the same incubation temperature, the soil nitrification rates decreased in a sequence of: chao soil with high SOM > chao soil with low SOM >black soil with high SOM > black soil with low SOM > red soil with low SOM > red soil with high SOM. There was a significant relationships between soil nitrification rate (incubated under 25℃ for 14 days) and soil total phosporus (TP), total potassium (TK), clay content and pH. Soil pH and TP content was the key factors controlling nitrification rate ( R ²=0.981).

Abstract:Quantity-intensity (Q/I) relationships of NH₄⁺ in purple soils and purple paddy soils different in land use (paddy field, dry land, woodland and vegetable plot) were studied. It was found that in both 0~20 cm and 20~40 cm layers of the two soils the curve of NH₄⁺ Q/I relationships were observed only when NH₄⁺ activity ratios in the soils were low, suggesting release of nonexchangeable (or specifically adsorbed) NH₄⁺ in the soils NH₄⁺ in the two soils ranged from 71.47 to 203.7 cmol kg^-1 (mol L^-1)^-1/2 in potential buffering capacity (PBC), from 0.029 5 to 0.089 7 cmol_c kg^-1 in labile NH4 (-ΔNH₄⁰), from 0.187 × 10^-3 to 1.255 × 10^-3 (mol L^-1)^1/2 in equilibrium activity ratio (AR⁰_NH4) and from 0.010 6~0.118 5 cmol kg^-1 in specific adsorption sites (NH_4-sas). Correlation analysis and path analysis indicate that the content of clay (<0.002 mm) is in extremely significant positive relationship with both PBC and NH_4-sas (p<0.01). The effect of clay (<0.002 mm) is mainly indirect on PBC (indirect path coefficient, 0.585), but strong and direct on NH_4-sas. Positive linear relationships were observed of organic C with -ΔNH₄⁰ and AR⁰_NH4 in all soil samples. The effect of organic C is high and direct on -ΔNH₄⁰ (direct path coefficient, 0.966), but indirect on -ΔNH₄⁰. The concentration of exchangeable NH₄⁺ is positively related to -ΔNH₄⁰ (r=0.876 4, n=8, p<0.01) and they are approximate in value. Moreover, exchangeable NH₄⁺ is also positively related to AR⁰_NH4 (r=0.983 7, n=8, p<0.01). This study clearly demonstrates that differences between the soils in clay and organic C are the main reason for the differences in exchangeable NH₄⁺ and Q/I parameters between purple soils different in land use. The use of exchangeable NH₄⁺ as indicator of NH₄⁺ availability has a similar effect as the use of Q/I relationships.

Abstract:Mollisol samples were incubated indoors with ¹³CO(NH₂)₂ as substrate to investigate transformation of urea-carbon into soil amino sugar and its effect on dynamics of amino sugar pool. Contents of the three types of amino sugars (glucosamine, galactosamine and muramic acid) and their enrichments of ¹³C were measured with gas chromatography/mass spectrometry. On such a basis, specific utilization of urea-carbon by different microbial communities was evaluated. Results show that urea-carbon might be assimilated by soil microorganisms, but was significantly lower in availability than glucose-carbon. A higher amount of ¹³C was found in glucosamine than in muramic acid, suggesting that fungi are more capable of assimilating urea-carbon than bacteria. Application of urea decreased soil organic carbon content to some extent and at the same time significantly lowered the total amino sugar and its relative proportion in soil organic carbon, indicating that in severe shortage of carbon sources, amino sugars would be the priority carbon source to be decomposed to make up the carbon supply. Although muramic acid was very low in concentration, it was highly capable of regulating and balancing carbon budget. Glucosamine was more stable than muramic acid, but decomposition of some of it was found in shortage of other carbon sources. As a whole, the dynamics of amino sugars is closely associated with the availability of soil carbon sources and their coupling effect, thus playing an important role in regulating supply and requirement of carbon and nitrogen in soil.

Abstract:Pot and incubation experiments were carried out to study effects of soil moisture and phosphorus (P) application on soil available P content in a new rice cultivation system, i.e. aerobic cultivation of rice crop. In the experiments, significant effects were observed of both soil moisture and P fertilization, and more of the interaction between the two, on soil available P content, and on biomass and P uptake by rice, as well. The content of soil available P in the tested soil increased with increasing soil moisture and P application rate, but decreased with growth of rice. Biomass and P uptake of rice increased with increasing P application rate and growth period of the crop, and peaked when soil moisture was moderate in content. Therefore, when the rice field is ensured soil moisture being 80% of the soil saturation moisture capacity and conventional N and K input, P application at 67.5 kg hm^-2 is adequate to meet the P requirement of rice for growth in aerobic soil.

Abstract:A field experiment was carried out during the period from 2005 to 2007 to investigate effects straw mulching and tillage on soil physical, chemical and biological properties of upland rice field that has been under the double-rice cropping system since 2003 in the seasonal arid region of South China (Yujiang County, Jiangxi Province). Results show that no significant difference was found between the treatments, i.e. conventional flooded rice cultivation (CF), upland rice cultivation with straw mulching (SM), and non-tillage upland rice cultivation with straw mulching (N-SM) in soil bulk density and total porosity in 0~ 15 cm depth soil layer. But Treatment N-SM significantly increased soil organic matter, total N, alkalystic N and soil basal respiration, and both Treatments SM and N-SM significantly increased soil microbial biomass carbon content and the activities of urease and saccharase, as was compared with Treatment CF. Therefore, the findings suggest that upland rice cultivation with straw mulching and non-tillage upland rice cultivation with straw mulching may be cited as novel water-saving and fertility building rice cultivation models for extrapolation in this region.

Abstract:Excessive nitrogen (N) fertilization in wheat season in the Taihu Lake region has resulted in serious environmental problems. Previous studies have recommended optimum N fertilization rate. However, so far no holistic evaluation has been made of environmental impacts of N fertilizer. Therefore, based on experiments on fates of various N fractions in relation to N application rate in the region, an evaluation model for knock-on effect of N was developed, integrating agronomic, environmental, and economic benefits in wheat season in the Taihu Lake region. Evaluation with the model show that N application was recommended at N 205 kg hm^-2 for wheat season in the Taihu Lake region, which may bring about maximum net benefit 2 621 Yuan, which is the balance between 3 722 yuan hm^-2 in yield benefit and 1 101 yuan hm^-2 in total environmental loss. The total loss covers the following losses lined in a decreasing sequence in terms of value, acid rain, greenhouse effect and eutrophication. If the net economic benefit is allowed to fluctuate within the range of 10 yuan hm^-2, the recommended regional mean N application rate would vary in the range from 193 to 218 kg hm^-2, which is 10% to 40% lower than the prevailing N application rate, and nevertheless, would increase the net economic benefit by 5%～15% in the Taihu Lake region. This method not only takes into account agronomic, environmental and economic benefits comprehensively, but also provides reference for eco-farming in other regions or other crops. It is easy for decision-makers and farmers to calculate or recommend N fertilizer rate.

Abstract:The key to ecological restoration of rocky desertification is to recover vegetation, of which the nature is to improve soil productivity. With a tract of farmland on the slope of depression in between typical karst hills as control, integrated ecological effect of the practice of “Grain for Green” was analyzed by determining 21 soil indexes of seven models of “Grain for Green”, i.e. converting farmland to land of Zenia insignis, Toona sinensis, Castanea mollissima, Citrus reticulata, Zenia insignis + Guimu No. 1 Forage, Guimu No. 1 Forage, or desertion for comparison with those of the control. On such a basis, an optimal model was screened out. Results show that in comparison with red soil in regions at the latitude, the soil in karst depression was higher in soil nutrient except for total potassium and available phosphorus. The practice of “Grain for Green” significantly increased most of the soil main nutrients, soil water content, and mineral nutrients, but reduced the content of SiO₂, indicating that all the seven models, except for cultivation of Zenia insignis, had their nutrient status restored up to the pre-rocky desertification level. Besides, the practice also increased microbial population, B_C, B_C/SOM, and B_C/TN, but decreased slightly B_N and B_N/TN. Clustering analysis intuitively divided the slope field and 7 conversion models into 4 types, i.e. remarkable improvement, improvement, slow improvement, and sluggish improvement, and the models of cultivation of Toona sinensis and Castanea mollissima are best in soil ecological effects.

Abstract:Effect of elevated surface O₃ concentration（~70 nmol mol^-1） on functional diversity of soil microbial communities in paddy field under the rice/wheat rotation system was investigated in 2009 and 2010 through determination of water-soluble organic carbon (WSOC) content and BIOLOG index, by making use of the O₃-FACE ( Free-Air ozone Concentration Enrichment) platform of China. Results show that with O₃ concentration elevated, both WSOC content, and AWCD (Average Well Colour Development ) tended to decrease. Diversity indexes determined in the two years indicate that elevated O₃ concentration did not have much effect on, Shannon, Simpson and McIntosh indices. PCA results in 2010 show that elevation of O₃ concentration affected the edaphon’s ability of utilizing substrates of some specific carbon sources. The findings of the experiment suggest that under elevated O₃ concentration (~70 nmol mol^-1), functional diversity of soil microbes was significantly increased in rice field.

Abstract:Based on the long-term experiment carried out in an upland field of red soil, the impacts of long-term application of organic manure on distribution and community structure of soil nematodes were studied. The long-term organic manure application experiment was designed to have four treatments: CK (no pig manure); ON1 (low amount of pig manure); ON2 (high amount of pig manure); ON2L (high amount of pig manure with lime). A total of 15 families and 29 genera of soil nematodes were identified in the upland field, including 8 genera of plant-parasites, 9 genera of bacterivores, 3 genera of fungivores and 9 genera of predators/omnivores, of which Pratylenchus, Rhabditis and Protorhabditis were found to be the dominant genera. The four treatments followed a decreasing order of ON2 > ON1> ON2L > CK in total nematode number. The soil nematode community responded differently to the treatments in all the ecological indices except for SI, which suggests that changes in soil nematode community structure may be used as an indicator of variation of soil fertility and considered an important bioindicator of soil health quality.

Abstract:For decades, a large area of natural desert grasslands in the middle reaches of the Heihe River in Hexi Corridor of Northwest China has been converted tract by tract into farmland and plantation. However, few researchers have addressed responses of ground arthropod communities to soil salinization in lands different in land-use and management. In this study, five major types of land use 21-year-old planted shrubland without irrigation and fertilization, 28-year-old irrigated Poplar plantation and 33- year-old irrigated Pinus plantation, 27-year-old farmland with irrigation and fertilization, and natural desert grassland were selected for comparison with the last one as control. All the sampling plots, except the last used to be natural desert grassland. Soil salinity and its composition in the surface layer and ground arthropod communities in the plots were observed. Based on the observations, redundancy analysis (RDA) and multiple regression analysis were performed to determine relationships between the distribution of the arthropod community and soil salinization variables. The one-way analysis of variance demonstrated that the conversion of natural grassland to planted shrubland, Poplar plantation, Pinus plantation and farmland significantly reduced abundance of the ground arthropod community, but little affected species richness of the arthropod community. Results of RDA show that soil salinization properties had significant and differential effects on abundance and species richness of the arthropod community. The key factors affecting composition of the ground arthropod community were soil pH, Na⁺, Mg²⁺, Cl^- and SO₄^2- concentrations in the topsoil layer. Abundance of the ground arthropods increased with increasing soil pH and decreased with increasing Mg²⁺ and Cl^- concentrations. The findings suggest that change in soil salinity environment caused by changes in land-use and management is one of the key variables driving evolution of the ground arthropod community.

Abstract:Fungal laccase can efficiently oxidize polycyclic aromatic hydrocarbons (PAHs), suggesting the potential of laccase-producing fungi for application to remediation of PAHs-contaminated soil. Based on its feature of being capable of oxidizing guaiacol into something red, a strain of laccase-producing fungus, F-1, was isolated from soil. According the BLAST alignment of near full-length 18S rRNA gene sequence, this strain is closely related to Myrothecium verrucaria. Both single factor and Plackett-Burman experiments were performed to assess F-1’s laccase-producing capacity. The laccase activity was found to be greatly increased by 2 orders of magnitude in specific culture medium, suggesting the significant effect of environment factors on laccase activity of F-1. Soil microcosms were set up with or without inoculation of F-1, and the PAHs contents were determined after 30-days of incubation. Results show that PhA, FluA, Pyr, BaA, Chr, BbF, BkF, BaP, DbA, BghiP and In[1,2,3-cd]P were degraded to varying extent in fungus inoculated microcosms, confirming the remedial potential of F-1 in PAHs-contaminated soil.

Abstract:Brasilobates spinosus Fujita collected from pollution-free soil by Tullgern method was used as subject in an experiment to explore effect of phoxim on activities of enzymes (acetylcholinesterase, adenosinetriphosphatase, glutathione-S-transferase, glutathione peroxidase, superoxide dismutase and catalase) in B. spinosus Fujita, 48 h and 96 h after treatment with phoxim. Results indicate that the activities of acetylcholinesterase and adenosinetriphosphatase declined obviously with increasing phoxim concentration and elapsing time, while the activities of the other four enzymes showed a reverse trend. A certain dose-effect relationship was found to be in existence between activities of the enzymes and concentration of phoxim, and the findings may serve as reference or basis for use of bio-indicator of phoxim pollution of soils.

Abstract:Palynological analysis of 33 samples of topsoils and mosses collected from fields under five different types of land use in the karst area of rocky desertification in Nanping Town, Chongqing, shows that (1) the spores and pollens found in the samples could be sorted into 50 genera dominated by those of herbage and ferns, which accounted for 38.84%～86.56% of the total (except for samples from Secondary Masson Pine forest, Secondary Cryptomeria forest and Peach orchard), and was followed by those of arbor (mainly Pinus massoniana) accounting for 13.42%～59.40%, and by those of shrubs, accounting for only about 0.00%～12.50%, which is a significant indicator of serious degradation of the local vegetation; (2) Abundance of pollen types did not differ much from field to field under different land uses, and changes in species diversity took place mainly in arbors and shrubs, and little in herbage and ferns; (3) Pollen assemblage varied sharply from field to field under different land uses, which reflects basically the situation of the current vegetation of the area; (4) With increasing land use intensity, pollens of arbors and shrubs were decreasing in content and type, while those of herbs and ferns increasing, and dominated by pollens of farmland weeds. It is, therefore, concluded that the changes in land use are the main factor affecting the secondary vegetation and the pollen assemblages in the karst rocky desertification area.

Abstract:How to acquire soil physico-chemical parameters instantly in the field is an important orientation of the research of soil science, and the technology is also a potential way to complement or replace the conventional soil laboratory analysis with field-based measurements. In 2008, a Working Group on Proximal Soil Sensing was formed in the International Union of Soil Sciences (IUSS). The working group is oriented to provide a platform for academic exchange on theories, technology, equipment and application of various proximal soil sensors. In this paper, researches on proximal soil sensors are classified per operation principles of the sensors and elaborated separately, and in the end, main problems and trends of the development of PSS are pointed out.

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