Spatial Subtidal Macrobenthic Distribution in Relation to Abiotic Conditions in the Lima Estuary, NW of Portugal

During the summer of 2002, sampling was carried out in the Lima estuary in order to compare the pattern of the macrobenthic community’s distribution in relation to physical and chemical variables. A total of 54 macrobenthic taxa were identified. Abundance, biomass and specific diversity varied among the twenty stations. Abundance ranged from 212 to 9856 ind./m², with an average of 1581 ind./m². Abra alba presented the highest density corresponding to 39.1% of the total specimens gathered, followed by Hediste diversicolor with 31.5%. Biomass ranged from 0.12 to 264.62 g AFDW/m², with an average of 17.58 g AFDW/m². Cerastoderma edule and A. alba were the species with a clear predominance in the total biomass, contributing 75.3 and 13.8%, respectively. The multivariate techniques used revealed a macrobenthic community with five distinct groups, particularly related to the sedimentological characteristics and salinity. These results demonstrated significant differences in macrobenthic assemblage’s composition along an estuarine gradient. For the first time the presence of the nonindigenous invasive species Corbicula fluminea was described in this estuary.     

Pollen and phytoliths from fired ancient potsherds as potential indicators for deciphering past vegetation and climate in Turpan, Xinjiang, NW China

It is demonstrated that palynomorphs can occur in fired ancient potsherds when the firing temperature was under 350°C. Pollen and phytoliths recovered from incompletely fired and fully fired potsherds (ca. 2700 yrs BP) from the Yanghai Tombs, Turpan, Xinjiang, NW China can be used as potential indicators for reconstructing past vegetation and corresponding climate in the area. The results show a higher rate of recovery of pollen and phytoliths from incompletely fired potsherds than from fully fired ones. Charred phytoliths recovered from both fully fired and incompletely fired potsherds prove that degree and condition of firing result in a permanent change in phytolith color. The palynological data, together with previous data of macrobotanical remains from the Yanghai Tombs, suggest that temperate vegetation and arid climatic conditions dominated in the area ca. 2700 yrs BP.     

新疆准噶尔荒漠植物叶片功能性状的进化和环境驱动机制初探

植物功能性状是由遗传因素和环境条件共同决定的。剖析各因素对植物性状变异的相对影响,对揭示植物对环境变化的响应和适应规律至关重要。作者以干旱区植物为研究对象,定量化分析了植物叶片功能性状变异及其与环境梯度的关系。研究区域位于中国新疆准噶尔盆地及其周边区域。在30个样地中,观测了110种植物的叶比重、叶片单位质量氮含量和单位面积氮含量以及叶片干物质含量,通过插值法获得每个样地的生物气候数据。结果表明:物种水平上叶片性状(性状值为每个物种的实际观测值)的变异在很大程度上由植物进化背景所决定,气候因子和功能群的作用次之;在群落尺度上(性状值为每个样地的权重和),叶比重与气候干旱程度呈正相关,单位质量氮含量在水热组合最优的区域出现最大值,而叶片干物质含量和单位面积氮含量与气候因子的相关性较小。叶比重是群落尺度上探讨叶片功能性状与环境梯度关系的一个合适的指标。此外,在研究植物性状-环境关系过程中,尽可能观测多个植物功能性状是必要的。但是,只有排除植物系统背景的影响,关于植物性状-环境关系的研究结论才可能接近真实情况。将来应该加强同一种内不同种群间的叶片性状的采样和分析工作。     

Spatial distribution,contamination levels,sources, and potential health risk assessment of trace elements in street dusts of Urumqi city,NW China

Abstract

A total of 83 dust samples were collected from the streets of Urumqi city in NW China and analyzed for the concentrations of As, Cd, Cr, Cu, Hg, Mn, Ni, Pb, and Zn elements. The spatial distribution, contamination levels, main sources, and potential health risks of these trace elements were determined based on geostatistical analysis, geo-accumulation index, multivariate analysis, and the health risk assessment model introduced by the USEPA, respectively. The obtained results indicate that the average concentrations of Cd, Cr, Cu, Hg, Ni, Pb, and Zn exceed the corresponding background values determined in Xinjiang soils by factors of 2.0, 1.35, 1.38, 8.24, 1.28, 2.09, and 3.26, respectively. The spatial distribution patterns of the nine trace elements in street dust were found to be substantially heterogeneous, and the contamination level decreased in the following order: Hg?>?Zn?>?Pb?>?Cd?>?Cr?>?Cu?>?As?>?Ni?>?Mn. Based on the identified concentrations, the collected dust samples were found to be moderately polluted by Hg, and not polluted by As, Cr, Cu, Mn, and Ni. The remaining elements, Cd, Pb, and Zn lie on the borderline between non-pollution and moderate pollution levels. Furthermore, it was shown that Mn and Zn in street dusts originate from both, natural and anthropogenic sources, while As, Cd, Cr, Cu, Hg, Ni, and Pb are mainly produced by anthropogenic sources. Overall, the carcinogenic and non-carcinogenic health risks of the analyzed elements, instigated primarily by oral ingestion of street dusts, were found to be within the acceptable range for both, children and adults. As and Cr are the main non-carcinogenic elements, whereas Cr is the major carcinogenic element among the investigated dust-bound metals in the study area.     

Spatial Distribution of Human Schistosoma japonicum Infections in the Dongting Lake Region,China

Background

The aim of this study was to spatially model the effect of demographic, reservoir hosts and environmental factors on human Schistosoma japonicum infection prevalence in the Dongting Lake area of Hunan Province, China and to determine the potential of each indicator in targeting schistosomiasis control.

Methodology/Principal Findings

Cross-sectional serological, coprological and demographic data were obtained from the 2004 nationwide periodic epidemiologic survey for Hunan Province. Environmental data were downloaded from the USGS EROS data centre. Bayesian geostatistical models were employed for spatial analysis of the infection prevalence among study participants. A total of 47,139 participants from 47 administrative villages were selected. Age, sex and occupation of residents and the presence of infected buffaloes and environmental factors, i.e. NDVI, distance to the lake and endemic type of setting, were significantly associated with S. japonicum infection prevalence. After taking into account spatial correlation, however, only demographic factors (age, sex and occupation) and the presence of infected buffaloes remained significant indicators.

Conclusions/Significance

Long established demographic factors, as well presence of host reservoirs rather than environmental factors are driving human transmission. Findings of this work can be used for epidemiologic surveillance and for the future planning of interventions in the Dongting Lake area of Hunan Province.     

乌鲁木齐南部山区地生地衣群落分布格局

为了查明乌鲁木齐南部山区地生地衣群落分布格局,作者选取了24个样点(20 m×20 m),设置了240个50cm×50 cm样方,调查地生地衣的种类及盖度,分析其分布格局及其与环境因子的关系.结果表明,乌鲁木齐南部山区共有地生地衣17种,隶属于2目5科10属.聚类分析和DCA排序将该地区的地生地衣分为4个主要样点组,分...     

Spatial patterns of leaf nutrient traits of the plants in the Loess Plateau of China

The spatial patterns of leaf nutrient traits of plants in seven sites, Yangling, Yongshou, Tongchuan, Fuxian, Ansai, Mizhi and Shenmu, standing from south to north in the Loess Plateau of China, were studied. The results showed that of the 126 plant samples in the Loess Plateau, the mean leaf organic carbon (C), nitrogen (N), phosphorus (P) and potassium (K) were 43.8, 2.41, 0.16 and 1.67%, respectively, and ranked in the order of C > N > K > P. Leaf C, N, P and K ranged from 32.6 to 54.8%, 0.82 to 4.58%, 0.06 to 0.35%, and 0.24 to 4.21%, respectively. The mean leaf C/N, C/P and N/P ratios were 21.2, 312 and 15.4, respectively. It is indicated that leaf N in the Loess Plateau was significantly higher than those in Chinese and global flora, but leaf P was significantly lower than that in global flora, which resulted in a higher N/P ratio in the Loess Plateau. The results also showed that leaf C, N, P, K, C/N and C/P ratios varied significantly among the seven life-form groups, which were trees, shrubs, herbages, evergreen trees, deciduous trees, C₃ and C₄ herbages, but leaf N/P ratio differed little among the seven life-forms. In the sampled species in the Loess Plateau, leaf C was negatively correlated with leaf N, P and K, while leaf N, P and K were positively correlated with one another. In general, leaf N/P ratio increased as the latitude and annual solar radiation increased and the mean annual rainfall and mean annual temperature decreased.     

Spatial patterns of photosynthetic characteristics and leaf physical traits of plants in the Loess Plateau of China

The spatial patterns of photosynthetic characteristics and leaf physical traits of 171 plants belonging to nine life-forms or functional groups (trees, shrubs, herbs, evergreen trees, deciduous trees, C₃ and C₄ herbaceous plants, leguminous and non-leguminous species) and their relationships with environmental factors in seven sites, Yangling, Yongshou, Tongchuan, Fuxian, Ansai, Mizhi and Shenmu, ranging from south to north in the Loess Plateau of China were studied. The results showed that the leaf light-saturated photosynthetic rate (P_max), photosynthetic nitrogen use efficiency (PNUE), chlorophyll content (Chl), and leaf mass per area (LMA) of all the plants in the Loess Plateau varied significantly among three life-form groups, i.e., trees, shrubs and herbs, and two groups, i.e., evergreen trees and deciduous trees, but leaf nitrogen content differed little among different life-form groups. For the 171 plants in the Loess Plateau, leaf P_max was positively correlated with PNUE. The leaf nitrogen content per unit area (N_area) was positively correlated but Chl was negatively correlated with the LMA. When controlling the LMA, the N_area was positively correlated with the Chl (partial r = 0.20, P < 0.05). With regard to relationships between photosynthetic characteristics and leaf physical traits, the P_max was positively correlated with N _area, while the PNUE was positively correlated with the Chl and negatively correlated with the N_area and LMA. For all the species in the Loess Plateau, the PNUE was negatively correlated with the latitude and annual solar radiation (ASR), but positively correlated with the mean annual rainfall (MAR) and mean annual temperature (MAT). With regard to the leaf physical traits, the leaf Chl was negatively correlated with the latitude and ASR, but positively correlated with the MAR and MAT. However, the N_area and LMA were positively correlated with the latitude and ASR, but negatively correlated with the MAR and MAT. In general, leaf N_area and LMA increased, while PNUE and Chl decreased with increases in the latitude and ASR and decreases in MAR and MAT. Electronic supplementary material The online version of this article () contains supplementary material, which is available to authorized users.     

黄土丘陵小流域土壤水分的空间异质性及其影响因子

研究了黄土丘陵小流域土壤水分空间异质性的剖面及时间变化规律，从土壤水分与环境因子的关系分析入手，探讨了景观尺度上土壤水分空间异质性的影响因子，结果表明，黄土丘陵小流域土壤水分的平均值与空间异质性均呈现出明显的剖面变化与季节变化规律，土壤平均含水量从表土层开始，随着土层深度的增加而增高；空间异质性（变异系数）从亚表层开始增加，土壤含水量在降雨后立即升高随后逐渐降低；空间异质性却正好相反，方差分析与相关分析表明，土壤水分的空间异质性是立地尺度（坡度），坡面尺度（坡位与相对高度）和流域尺度（土地利用与降雨）等多重尺度上的环境因子共同作用的结果，这些不同尺度的环境因子对土壤水分空间异质性的影响表现出明显的剖面变化规律与季节变化规律。     

Distribution of soil organic C, N and P in three adjacent land use patterns in the northern Loess Plateau, China

The northern Loess Plateau is an important cropping-pastoral ecotone and wind–water erosion crisscross region in China, but the distribution of soil organic carbon (C), nitrogen (N) and phosphorus (P) in different land uses across this vulnerable ecoregion is not well understood. This study was carried out to determine the distribution patterns of soil organic C, N and P in native grassland and in two woody lands (Chinese Pine land and Korshinsk Peashrub land) that were established on the native grassland 28 years ago. In the north part of the Loess Plateau, the concentrations of soil organic C, N and P were lower than in the southern Loess Plateau either across or within the land use patterns. The concentrations and stocks of organic C and total N were significantly decreased in Chinese Pine and Korshinsk Peashrub lands compared with those in native grassland in the surface 0–40 cm soil layer, where more than 70% of the roots were distributed. The decreases in organic C in 0–40 cm soil layers were 2.6 and 3.0 Mg C ha^?1 (26.3 and 27.7%) by Chinese Pine and Korshrinsk Peashrub, while those of total N were 0.6 and 0.4 Mg N ha^?1 (31.5 and 17.2%), respectively, compared with native grassland. Both concentration and stock of total P varied only slightly with land use. The findings suggested that the conversion of natural grass into Chinese Pine and Korshinsk Peashrub resulted in decreased soil organic C and total N in the surface 0 to 40 cm soil layer of the northern Loess Plateau. Our results further indicated that a combination of low temperatures, little precipitation and large soil degradation impede increasing C and N stocks by afforestation, and the afforestation on grassland should be viewed very critically in such areas.