Zhang Fengrong

Change of soil organic matter as affected by household land use based on 3S technology in urban fringes of north China

Abstract Different land‐use managements accompany different land‐use objectives in the changing phases of household economic development. These management changes lead to a number of changes in soil nutrients such as in soil organic matter (SOM). This article, with support from global positioning system (GPS) and geographic information system (GIS) monitoring, analyses and compares SOM change in an area of urban fringe in north China from 1982 to 2000 and then from 2000 to 2006. SOM increased by 27% (5.43 g kg‐1‐6.90 g kg‐1) during the first period but decreased by 7% during the second. In the first period, with the implementation of the “Household Responsibility System”, material inputs, especially of fertiliser was very high when the central household objective was to “have a full stomach”. Yields also increased quickly, so there were corresponding increases in the amount of organic materials returned to the fields and SOM also increased during this earlier period. In the second period, household objectives developed making a trade‐off between consumption and income above subsistence level. Land‐use types evolved from subsistence field cropping to the growing of cash crops. Changing material inputs and managements between the different cropping systems affected soil nutrients such as SOM. SOM decreased in most of the region during this second period. Dynamic monitoring (GPS and GIS) is needed in the region to conduct scientific research on fertiliser use and management.

The Reclamation Effects Should Be Considered for Saline Soil Criteria in Soil Classification System

It is well known that most saline soils have salt accumulation at the soil surface and the root zone due to the capillary movement of saline groundwater and subsequent evaporation. The criteria for classifying soil as saline taxa are different in different soil classification systems. In Chinese Soil Taxonomy (CST), soils that have a salic horizon starting within 30 cm from the soil surface are named as Orthic Halosols. In the World Reference Base for the Soil Resources (WRB), soils that have a salic horizon starting within 50 cm from the soil surface are named as Solonchaks. In the US Soil Taxonomy (ST), soils that have a salic horizon starting within 100 cm from the soil surface are named as Salids. In China, a large area of saline soils was reclaimed for crop production. This chapter describes some soil profiles that were classified into saline taxa in CST, WRB, and ST before they are reclaimed, to see if these soils, after a long history of irrigation, are still classified into saline taxa in the three soil classification systems. The results showed that the salts were leached into certain depth, the salic horizons were observed at different depth from the surface, many profiles could not be classified as Orthic Halosols as identified earlier, some of them could not be classified as Solonchaks, and few of them even could not be classified as Salids. With a long irrigation history, the depth of salic horizon is related to the amount of irrigation water and irrigation models. When more water was used for irrigation each time, the salts were found at deeper layers. Relatively the surface irrigation leached the salts deeper than the drip irrigation. According to the present study, we suggest that the criteria of ST should be taken in order to keep the reclaimed saline soils in the saline taxa, i.e., soil classification should not be changed by irrigation. We also suggest that more soil survey should be taken for discovering how much water was used in normal irrigation models and how deep the salts were leached under such normal irrigation models. Through analyzing large amount of data, especially those data coming from reclaimed saline soils, the depth and index for salic horizon should be redefined to keep the reclaimed saline soils in the saline taxa of soil classification systems. In this chapter, we examined the criteria of saline soil classification and made some suggestions by citing other scholar’s research results published in the scientific literature.

Analyzing Land Use Structur e Differ ence of Rur al Residential Ar eas in Differ ent Regions of Pinggu Distr ict of Beijing

Based on the collective land survey data in Pinggu,Beijing in 2006,the paper analyzes the inner land use structure in rural residential areas of differential regions with the aid of landscape ecology method,thus revealing its geographical distributions.It shows that the difference in productivity caused the characteristic of land use structure of different regions.As far as the diversity index of inner land use structure is considered,Mid-Levelsplainsmountains.As far as the centrality index is considered,mountainsplainsMid-Levels.Meanwhile,the location index of different land use types change regularly as the regions change.As far as residence land is considered,mountainsplainsMid-Levels.As far as factory land is considered,Mid-Levelsmountainsplains.As far as service establishment land is considered,Mid-Levelsmountains plains,as far as idle construction land is considered,plainsmountainsMid-Levels.In the progress of new rural area construction in the future,the development of urban and rural should be integrated in the view of arranging the industry distribution reasonably,and reflect the principle of land intensive use.Moreover,different rural residential areas should have different scale control modes and approaches of land adjustment.