土壤系统分类中年平均土温的判定

广西年平均气温具有三维的分布规律。某些地方的年平均气温可以用三元经验方程来估算。经验方程是:(?)(年平均气温℃)=69.2362-0.6675×纬度-0.2941×经度-0.0049×海拔(m)。用各气象台站的有关数据,通过线性回归方程可得到年平均土温的附加常量,便可估算出任何采样点的年平均土温,对野外工作带来方便。

Influence of Climate on Soil Organic Carbon in Chinese Paddy Soils

Soil organic carbon(SOC) is a major component of the global carbon cycle and has a potentially large impact on the greenhouse effect. Paddy soils are important agricultural soils worldwide, especially in Asia. Thus, a better understanding of the relationship between SOC of paddy soils and climate variables is crucial to a robust understanding of the potential effect of climate change on the global carbon cycle. A soil profile data set(n = 1490) from the Second National Soil Survey of China conducted from 1979 to 1994 was used to explore the relationships of SOC density with mean annual temperature(MAT) and mean annual precipitation(MAP) in six soil regions and eight paddy soil subgroups. Results showed that SOC density of paddy soils was negatively correlated with MAT and positively correlated with MAP(P < 0.01). The relationships of SOC density with MAT and MAP were weak and varied among the six soil regions and eight paddy soil subgroups. A preliminary assessment of the response of SOC in Chinese paddy soils to climate indicated that climate could lead to a 13% SOC loss from paddy soils. Compared to other soil regions, paddy soils in Northern China will potentially more sensitive to climate change over the next several decades. Paddy soils in Middle and Lower Yangtze River Basin could be a potential carbon sink. Reducing the climate impact on paddy soil SOC will mitigate the positive feedback loop between SOC release and global climate change.

Micromorphological Evidences of Climatic Change in Yazd Region,Iran

The fact of, present is the key of the past, will help us to use paleosols properties as indicators of the ecological characteristics of past .time, particularly the paleoclimate. In this respect the micro- morphological properties showed to be a very good indicator. Therefore, for investigating of climate change in Ardakan-Yazd plain, Central Iran 9 pedons were digged and described. Yazd has an arid climate with less than 100 mm annual precipitation and more than 22℃ mean annual temperature （Aridic-hyper thermic soil moisture and temperature regions, respectively）. Based on the morphological and physicochemical analysis Arglic, Calcic and Gypsic diagnostic horizons have been distinguished in these soils. Thin section studied showed that the illuviated form of clay includes, infillings on channel, coating on pendant, on nodules and on grains, at lower depths and also juxtaposed calcite needles on void argillan at upper part of the profiles. Mineralogical result showed fine clay in arglic horizon, too. Considering depth and forms of these pedofeatures, we concluded that, the observed illuviated clays at lower depth must be the result of the more humid climate of the past, where the carbonates have been removed completely as pendant, nodules or coating to considerable depth, following processes, clay has been dispersed and also trans located to these depths. In contrast to these features, the juxtaposed needle calcite at the shallower depth is probably the result of drier climate of today.

Nematode Diversity in Phaeozem Agroecosystems of Northeast China

The diversity and distribution patterns of soil nematode communities in phaeozem agroecosystems of Northeast China were assessed to evaluate nematode taxonomic diversity and functional diversity in relation to climatic condition and soil characteristics in human modified landscape. Along the latitudinal gradient, soil samples were collected from north （Hailun） to south （Gongzhuling） down to a depth of 100 cm with intervals of 030, 20-40, 40-60, 60-80, and 80-100 cm. The nematode abundance and taxonomic diversity （generic richness） were lower at Hailun than at other sites, and higher values of evenness were observed at Hailun and Harbin than at Dehui and Gongzhuling. Nematode faunal analysis revealed that soil food web at Hailun was sueeessionally more mature or structured, and the environment little disturbed, while at Harbin and Gongzhuling, the soil food web was degraded with stressed environment. The environmental variables relevant in explaining the patterns of nematode distribution and diversity in phaeozem agroecosystems, using canonical correspondence analysis （CCA）, were the mean annual temperature, total nitrogen, electrical conductivity, mean annual precipitation, and other soil properties. Among these variables, the mean annual temperature was a relatively important factor, which could explain 29.05% of the variations in nematode composition.

Zonal Differences in Correlation Patterns Between Soil Organic Carbon and Climate Factors at Multi-extent

Studying the relationship between climate factors and soil organic carbon （SOC） is vitally important. However, how SOC responses to climate （temperature and precipitation） at cohesive extents is poorly studied. Two transects of approximately the same length （transect P and transect T） were selected to examine the variation of SOC content in relation to mean annual temperature （MAT） and mean annual precipitation （MAP）. The coefficients of partial correlation between SOC density and MAT （Rt） and MAP （Rp） were determined to quantify the relationships between SOC density and the two climate factors. The results indicated that for transect T, Rt was statistically significant once the extent level was greater than or equal to two fundamental extent units, while for transect P, Rp showed statistical significance only at extent levels which were greater than two fundamental extent traits. At the same extent levels but in different transects, Rts exhibited no zonal difference, but Rps did once the extent level was greater than two fundamental extent units. Therefore, to study the relationship between SOC density and different climate factors, different minimum extent levels should be ex- amined. The results of this paper could deepen the understanding of the impacts that SOC pool has on terrestrial ecosystem and global carbon cycling.

Branched tetraether lipids in Chinese soils:Evaluating the fidelity of MBT/CBT proxies as paleoenvironmental proxies

The ubiquitous occurrence of branched glycerol dialkyl glycerol tetraethers(br GDGTs) in soils has allowed development of new proxies for reconstruction of past climate and environment. The methylation and cyclization degrees of br GDGTs, expressed as MBT and CBT, respectively, are reported to be mainly controlled by mean annual air temperature(MAAT) and soil p H. However, the br GDGT-derived temperatures and soil p H scatter widely when data from different environmental conditions are considered. In this study, we collected over 300 soil samples from China, which are representative of humid(Xishuangbanna, Guangzhou, and Shanghai), semi-arid(Dongying) and semi-arid/arid(Lanzhou, Tibetan Plateau) regions. Collectively we have the most extensive dataset that broadly characterizes the distribution of br GDGTs according to climate zones in China. The overall data demonstrate that the MBT/CBT derived temperatures better match the measured MAATs in humid and non-alkaline regions than those from regions of low MAP(<400 mm/yr) and above neutral soil p H(>7.0–7.5). Similarly, CBT describes soil p H much better in humid and non-alkaline soils than in semi-arid/arid and alkaline soils; the semi-arid/arid and alkaline soils tend to show a positive correlation between soil p H and CBT, which contradicts that in the humid and non-alkaline soils. While soil p H, MAAT and mean annual precipitation(MAP) are dominating factors controlling the br GDGT distribution across all climate zones, conductivity, total organic carbon and total nitrogen, as well as soil water content can also play an important role locally. Removing br GDGT-II resulted in a revised CBT index that provides more accurate estimation of p H, especially in semi-arid/arid and alkaline soils. The overall Chinese dataset demonstrates that continental air temperature derived from br GDGT-proxies can vastly deviate from real measurements and should be used with extreme caution in paleo-climate or-environment studies.

Carbon and Nitrogen Storage in Inner Mongolian Grasslands: Relationships with Climate and Soil Texture

Understanding the spatial variability of soil carbon （C） storage and its relationship with climate and soil texture is critical for developing regional C models and for predicting the potential impact of climate change on soil C storage. On the basis of soil data from a transect across the Inner Mongolian grasslands, we determined the quantitative relationships of C and nitrogen （N） in bulk soil and particle-size fractions （sand, silt, and clay） with climate and soil texture to evaluate the major factors controlling soil C and N storage and to predict the effect of climate changes on soil C and N storage. The contents of C and N in the bulk soil and the different fractions in the 0 20 and 20 40 cm soil layers were positively correlated with the mean annum precipitation （MAP） and negatively correlated with the mean annual temperature （MAT）. The responses of C storage in the soil and particle-size fractions to MAP and MAT were more sensitive in the 0-20 cm than in the 2（~40 cm soil layer. Although MAP and MAT were both important factors influencing soil C storage, the models that include only MAP could well explain the variation in soil C storage in the Inner Mongolian grasslands. Because of the high correlation between MAP and MAT in the region, the models including MAT did not significantly enhance the model precision. Moreover, the contribution of the fine fraction （silt and clay） to the variation in soil C storage was rather small because of the very low fine fraction content in the Inner Mongolian grasslands.