Taiyang Zhong

Estimation of the relationship between vegetation patches and urban land surface temperature with remote sensing

It is well known that vegetation has cooling effect on urban land surface temperature (ULST). However, the influence of vegetations structure, component, and spatial distribution on ULST has rarely been quantitatively studied. This paper, taking Landsat ETM+ data to retrieve ULST, and IKONOS data to obtain vegetation information, studied the relationship between ULST and vegetation patches. Results showed that in the urban environment, (1) ULSTs over tree and shrub, lawn, and weed patches were not much different, because of the edge effects of the vegetation patches and their fragmentized distribution pattern; (2) the relationship between ULST and area, perimeter, and shape index of vegetation patches exhibited positive, while LST and the ratio of perimeter/area presented negative linear relationship; (3) using land use polygons as units, area density had quadratic curve relationship to ULST, edge density and mean area density, had strongly negative relationship to ULST. These results indicated that not only the characteristics of vegetation patches, but also their spatial distribution had a great effect on ULST, which should be considered in urban ecological environment management.

Impact of Soil Heavy Metal Pollution on Food Safety in China.

Food safety is a major concern for the Chinese public. This study collected 465 published papers on heavy metal pollution rates (the ratio of the samples exceeding the Grade II limits for Chinese soils, the Soil Environmental Quality Standard-1995) in farmland soil throughout China. The results showed that Cd had the highest pollution rate of 7.75%, followed by Hg, Cu, Ni and Zn, Pb and Cr had the lowest pollution rates at lower than 1%. The total pollution rate in Chinese farmland soil was 10.18%, mainly from Cd, Hg, Cu, and Ni. The human activities of mining and smelting, industry, irrigation by sewage, urban development, and fertilizer application released certain amounts of heavy metals into soil, which resulted in the farmland soil being polluted. Considering the spatial variations of grain production, about 13.86% of grain production was affected due to the heavy metal pollution in farmland soil. These results many provide valuable information for agricultural soil management and protection in China.

Scaling of impervious surface area and vegetation as indicators to urban land surface temperature using satellite data

Vegetation and impervious surface as indicators of urban land surface temperature (LST) across a spatial resolution from 30 to 960 m were investigated in this study. Enhanced thematic mapper plus (ETM+) data were used to retrieve LST in Nanjing, China. A land cover map was generated using a decision tree method from IKONOS imagery. Taking the normalized difference vegetation index (NDVI) and percent vegetation area (V) to present vegetated cover, and the normalized difference building index (NDBI) and percent impervious surface area (I) to present impervious surface, the correlation coefficients and linear regression models between the LST and the indicators were simulated. Comparison results indicated that vegetation had stronger correlation with the LST than the impervious surface at 30 and 60 m, a similar magnitude of correlation at 120 and 240 m, and a much lower correlation at 480 and 960 m. In total, the impervious surface area was a slightly better indicator to the LST than the vegetation because all of the correlation coefficients were relatively high (>0.5000) across the spatial resolution from 30 to 960 m. The indicators of LST, V and I are slightly better than the NDVI and NDBI, respectively, based on the correlation coefficients between the LST and the four indices. The strongest correlation of the LST and vegetation at the resolution of 120 m, and the strongest correlation between the LST and impervious surface at 120, 480 and 960 m, denoted the operational scales of LST variations.

Pollution and health risk assessment of heavy metals in urban soil in China

ABSTRACT The pollution and potential health risk due to lifetime exposure to heavy metals in urban soil of China were evaluated, based on the urban soil samples collected from published papers from 2005 to 2014. The contamination levels were in the order of Cd > Hg > Cu > Zn > Pb >As > Ni > Cr, and Hg and Cd fell into the category of “moderately contaminated” to “heavily contaminated.” The non-carcinogenic risk for different populations varied greatly, among which children faced high risk, and then the adult female and adult male followed. The hazard index (non-carcinogenic risk) higher than 1.00 occurred in Shanghai, Gansu, Qinghai, Hunan, and Anhui, whereas most of those in northern and western China had low risks. For the carcinogenic risk, Anhui and Ningxia provinces had urban soils exceeding the safe reference (1 × 10−6–1 × 10−4). Qinghai and Gansu had high carcinogenic risks since their risk indexes were much closer to the reference, and the others were in low risk.

Growing centralization in China’s farmland protection policy in response to policy failure and related upward-extending unwillingness to protect farmland since 1978:

Since 1978, China has experienced a rapid loss of arable land, leading to centralizing of farmland protection policies. To understand the growing centralization, this paper has used the lens of the interactions among (1) unwillingness to protect farmland among diverse actors, (2) policy failure and (3) policy change. The growing centralization is an adaptive response to the unwillingness to protect farmland from local up to provincial government levels, and its associated policy failure. The article suggests that gradual centralization over the last almost 40 years has gone through three phases: centralization to county-level, centralization to provincial-level, and intensifying technical supervision from central government. In the first phase, the unwillingness to preserve farmland appeared at the levels of the rural household, village and township; in the second phase, county- and prefecture-level governments began to lose willingness to preserve farmland; and, in the third phase, provincial governments’ willingness to preserve farmland weakened. The current centralized system has succeeded, for the most part, in addressing the problem of asymmetric information about farmland preservation between central and local governments, but the basic planning problem regarding loss of farmland remains a challenge.

Comparative analysis of influence factors on arable land use intensity at farm household level: A case study comparing Suyu District of Suqian City and Taixing City, Jiangsu Province, China

Using data from the farm household survey conducted in 2009, arable land use intensity (ALUI) and its influence factors at farm household level were investigated by the Tobit model. Suyu District of Suqian City and Taixing City of Jiansu Province, China were chosen as the regions for comparison. The results show that: 1) On the average, the ALUI, labor intensity, yield-increasing input, and labor-saving input are 15 238.14 yuan (RMB)/ha, 192 d/ha, 7233.01 yuan/ha, and 2451.32 yuan/ha in the less economically developed Suyu District, and 13 020.65 yuan/ha, 181 d/ha, 5871.82 yuan/ha, and 2625.97 yuan/ha in more economically developed Taixing City. The figures indicate that Suyu District has higher ALUI and labor intensity input but lower labor-saving input. 2) Comparing all the influence factors, the total arable land area in available and average plot size have bigger effects on arable land intensive use; to a small degree, family’s non-farm income affects labor intensity, yield-increasing input, and labor-saving input; the yield-increasing input decreases significantly when the householder has higher education attainment; the commercialization rates of agricultural products and the planting proportion of cash crops both have unstable influence on ALUI; the share of arable land rented in has few impacts on labor intensity, yield-increasing input, and labor-saving input. 3) There are no differences found in the internal impact mechanism of influence factors on the arable land intensive use behaviors of farm households. However, there are conspicuous disparities in the impact degrees and statistical significance based on varying economic levels. 4) Using the results as bases, this study proposes that the government should implement land management and agricultural policies according to local condition. And these policies should decrease land fragmentation to promote scale management of land and arable land use intensification.

Carbon Emission of Regional Land Use and Its Decomposition Analysis: Case Study of Nanjing City, China

Through the matching relationship between land use types and carbon emission items, this paper estimated carbon emissions of different land use types in Nanjing City, China and analyzed the influencing factors of carbon emissions by Logarithmic Mean Divisia Index (LMDI) model. The main conclusions are as follows: 1) Total anthropogenic carbon emission of Nanjing increased from 1.22928 × 107 t in 2000 to 3.06939 × 107 t in 2009, in which the carbon emission of Inhabitation, mining & manufacturing land accounted for 93% of the total. 2) The average land use carbon emission intensity of Nanjing in 2009 was 46.63 t/ha, in which carbon emission intensity of Inhabitation, mining & manufacturing land was the highest (200.52 t/ha), which was much higher than that of other land use types. 3) The average carbon source intensity in Nanjing was 16 times of the average carbon sink intensity (2.83 t/ha) in 2009, indicating that Nanjing was confronted with serious carbon deficit and huge carbon cycle pressure. 4) Land use area per unit GDP was an inhibitory factor for the increase of carbon emissions, while the other factors were all contributing factors. 5) Carbon emission effect evaluation should be introduced into land use activities to formulate low-carbon land use strategies in regional development.

Spatial distribution and risk assessment of copper in agricultural soils, China

ABSTRACT High Cu contamination in agricultural soil can cause toxicity, leading to ecological damages. Thus, we need to understand the concentration level, contaminated area, and spatial distribution of Cu in agricultural soils on a regional or national scale. This paper reviewed the studies on Cu concentrations throughout Chinese agricultural soils, based on relevant 482 published papers from 2004 to 2017. The results showed that the average Cu concentration was 29.85 mg/kg, higher than its background of 22.60 mg/kg, indicating that Cu has been introduced into soil from exterior sources. A large high spatial cluster was observed in southern China, including Hunan, Fujian, Guangdong, and Guangxi provinces, while low spatial clusters were mainly found in Chongqing and Shandong provinces. About 3.08% of the agricultural areas faced a high Cu risk, higher than the pollution rates of the whole land uses, based on the spatial distribution of Cu concentrations throughout China. The remaining areas were within the ranges of moderate and low Cu risks.

Links between China’s “virtual land use” and farmland loss

ABSTRACT China has experienced notable loss of farmland and increase in food imports during the past three decades. This article provides an econometric examination of the interactions between virtual land use through food trade and farmland loss in China. The results show that net virtual land imports have grown from 2.37 million hectares (Mha) in 1987 to 33.51 Mha in 2013, accounting for one-quarter of China’s farmland in 2013. The analysis on causality indicates there has been bidirectional feedback: the aggravated farmland conversion stimulated virtual land imports, which in turn increased construction encroachment on farmland.