黑土稻田生长季／休闲期温室气体排放研究

本文以黑土稻田为供试对象，对稻田生长季和休闲期CH4和N2O的排放通量进行了研究。结果表明，黑土稻田生长季CH4的排放总量为2.719／m2，接近中国稻田生长季CH4排放总量变化范围的下限。N2O的排放量很少，只有0.07g／m2，排放主要集中在水稻生长季节中的排水阶段。采用间歇灌溉和施用长效尿素的农田管理方式后，计算综合温室效应发现，间歇灌溉措施和施用长效尿素分别能减少稻田生长季CH4和NZO综合排放量的13 ．3％和4.8％。稻田休闲期CH4的排放量很小，可忽略不计；NZO的排放主要发生在春季土壤融化期，排放量占休闲期NZO排放总量的57.4％。针对大田冻融期获得的结果，设计了室内模拟冻融试验。结果表明，冰冻土壤在融化初期出现NZO的排放高峰，而土壤冰冻初期在短时间内也排放大量的N2O。添加硝态氮的处理在冻土融化时，N2O的排放量显著高于未添加硝态氮处理。冰冻时间越长，则冻融期间的N2O排放量越大。在水稻休闲季节对土壤进行了翻耕并施入稻草处理，结果表明翻耕能减少土壤中N2O的排放，施加稻草则增加N2O的排放；翻耕和施加稻草均能促进大田CO2的排放。针对东北黑土区气温逐年升高的情况，设计了室内模拟试验考察温度升高对黑土稻田土壤淹水期cH；刻卜放的影响。结果表明，温度升高显著促进稻田CH；的排放。

乙草胺、甲胺磷及其复合对黑土真菌的生态效应

农药对土壤微生物区系结构和功能的影响以及潜在的生态风险成为人们关注的热点之一。本文以中科院海伦生态站农田黑土作为实验土壤，采用室内模拟的方法，利用传统的（CFU和ergosterol）及分子微生物生态学技术（DGGE，real-time PcR，clolle library）研究了乙草胺、甲胺磷及其复合对黑土真菌的生态效应，并得出以下结果：经8周处理，中、高浓度乙草胺（150和250mgkg-1）对土壤真菌数量、生物量和可培养真菌种群多样性具有长期抑制效应。乙草胺处理8周后可培养真菌和土壤固氮微生物n州基因的种群结构不能得到恢复，而总的真菌结构可基本恢复。甲胺磷对土壤可培养真菌数量和生物量具有促进作用，以高浓度（250mgkg~(-1)）尤为显著。高浓度甲胺磷（25omgkg~(-1)）对nifH基因多样性有长期抑制效应。甲胺磷处理8周后可培养真菌种群结构不可恢复，而总的真菌和n积基因种群结构可部分恢复。两者复合后对真菌数量，生物量，多样性及n担基因多样性的影响无论是促进还是抑制其作用强度都大于单因子。处理8周后可培养真菌、总的真菌和n州基因三者的种群结构均不可恢复。克隆测序分析发现乙草胺、甲胺磷及其复合可明显促进植物致病真菌（colletolrichum；truncatum，Rhizoctonia zeae，Fusarium oxysporum）的生长，同时使土壤中常见的青霉菌数量减少，使农药处理后具有潜在的植物病害爆发的风险。本试验结果表明，乙草胺、甲胺磷及其复合对土壤真菌数量、结构、多样性和功能基因nifH的多样性及其种群组成有不同程度的影响，甚至产生某些不可逆的长期生态效应。复合处理对土壤真菌的影响要大于两个单因子作用，表现了明显的复合生态效应。一般来说受到午扰的真菌种群结构不容易自然恢复，因此建议在施用这两种农药过程中要避免大量、频繁的单独或复合施用。

黑龙江省黑土区土壤养分空间变异特征研究

本研究在大样本实验研究的基础上，综合运用现代信息统计原理和比较分析方法，从时空运动的角度，对黑龙江省黑土区23个县市的耕层土壤有机质、全氮、全磷、全钾、碱解氮、有效磷、有效钾含量的空间异质性特征及其演变过程进行了深入研究。目前黑龙江省黑土有机质和全氮含量仍处于我国较高的水平，全量磷钾含量处于中等水平，速效磷钾含量却处于高等级水平。土壤有机质与除有效磷外的其它5种养分性状均呈0.001水平极显著相关，23个县市的7种养分性状综合聚类为3个主要区域。7种养分含量均具有较强的空间相关性，钾素的空间有效相关距离最小，为200km，有效磷为372k讯，其它在600-1100k讯之间。有机质、全氮、全磷、碱解氮含量的空间分布主要受结构因素影响，分别高达84％、79.6％、84.8％、91.3％，且有相似的空间分布规律；全钾和有效钾的空间分布受结构因素和随机因素的影响约各占50％，空间分布相反；有效磷含量完全受随机因素施肥的影响，空间分布除哈尔滨市外较均匀。同开垦前的相比，有机质、全氮、全磷含量下降均超过50％，同第二次土壤普查比，全磷、全钾含量降低相对较大，土壤有机质和全氮含量有升有降，变化幅度小，南部部分县市和拜泉县养分状况正朝好的方向发展。

Grassland degradation in the

Supported by MSS images in the mid and late 1970s, TM images in the early 1990s and TM/ETM images in 2004, grassland degradation in the "Three-River Headwaters" region (TRH region) was interpreted through analysis on IRS images in two time series, then the spatial and temporal characteristics of grassland degradation in the TRH region were analyzed since the 1970s. The results showed that grassland degradation in the TRH region was a continuous change process which had large affected area and long time scale, and rapidly strengthen phenomenon did not exist in the 1990s as a whole. Grassland degradation pattern in the TRH region took shape initially in the mid and late 1970s. Since the 1970s, this degradation process has taken place continuously, obviously characterizing different rules in different regions. In humid and semi-humid meadow region, grassland firstly fragmentized, then vegetation coverage decreased continuously, and finally "black-soil-patch" degraded grassland was formed. But in semi-arid and and steppe region, the vegetation coverage decreased continuously, and finally desertification was formed. Because grassland degradation had obviously regional differences in the TRH region, it could be regionalized into 7 zones, and each zone had different characteristics in type, grade, scale and time process of grassland degradation.

Dynamics of plant populations in Heteropogon contortus(black speargrass) pastures on a granite landscape in southern Queensland. 2. Seed production and soil seed banks of H. contortus

Seed production and soil seed hanks of H. contortus were studied in a subset of treatments within an extensive grazing study conducted in H. contortus pasture in southern Queensland between 1990 and 1996. Seed production of H. contortus in autumn ranged from 260 to 1800 seeds/m2 with much of this variation due to differences in rainfall between years. Seed production was generally higher in the silver-leaved ironbark than in the narrow-leaved ironbark land class and was also influenced by a consistent stocking rate x pasture type interaction. Inflorescence density was the main factor contributing to the variable seed production and was related to the rainfall received during February. The number of seeds per inflorescence was unaffected by seasonal rainfall, landscape position, stocking rate or legume oversowing. Seed viability was related to the rainfall received during March. Soil seed banks in spring varied from 130 to 520 seeds/m2 between 1990 and 1995 with generally more seed present in the silver-leaved ironbark than in the narrow-leaved ironbark land class. There were poor relationships between viable seed production and the size of the soil seed bank, and between the size of the soil seed bank and seedling recruitment. This study indicates that H. contortus has the potential to produce relatively large amounts of seed and showed that the seasonal pattern of rainfall plays a major role in achieving this potential

Black carbon affects the cycling of non-black carbon in soil

Black carbon (BC) is an important fraction of many soils worldwide and plays an important role in global C biogeochemistry. However, few studies have examined how it influences the mineralization of added organic matter (AOM) and its incorporation into soil physical fractions and whether BC decomposition is increased by AOM. BC-rich Anthrosols and BC-poor adjacent soils from the Central Amazon (Brazil) were incubated for 532 days either with or without addition of (13)C-isotopically different plant residue. Total C mineralization from the BC-rich Anthrosols with AOM was 25.5% (P < 0.05) lower than with mineralization from the BC-poor adjacent soils. The AOM contributed to a significantly (P < 0.05) higher proportion to the total C mineralized in the BC-rich Anthrosols (91-92%) than the BC-poor adjacent soils (69-80%). The AOM was incorporated more rapidly in BC-rich than BC-poor soils from the separated free light fraction through the intra-aggregate light fraction into the stable organo-mineral fraction and up to 340% more AOM was found in the organo-mineral fraction. This more rapid stabilization was observed despite a significantly (P < 0.05) lower metabolic quotient for BC-rich Anthrosols. The microbial biomass (MB) was up to 125% greater (P < 0.05) in BC-rich Anthrosols than BC-poor adjacent soils. To account for increased MB adsorption onto BC during fumigation extraction, a correction factor was developed via addition of a (13)C-enriched microbial culture. The recovery was found to be 21-41 % lower (P < 0.05) for BC-rich than BC-poor soils due to re-adsorption of MB onto BC. Mineralization of native soil C was enhanced to a significantly greater degree in BC-poor adjacent soils compared to BC-rich Anthrosols as a result of AOM. No positive priming by way of cometabolism due to AOM could be found for aged BC in the soils. (C) 2009 Elsevier Ltd. All rights reserved.

(Table 1) Tree age, post fire stand age, and soil organic matter thickness in the western Quebec black spruce boreal ecosystem

The observed long-term decrease in the regional fire activity of Eastern Canada results in excessive accumulation of organic layer on the forest floor of coniferous forests, which may affect climate-growth relationships in canopy trees. To test this hypothesis, we related tree-ring chronologies of black spruce (Picea mariana (Mill.) B.S.P.) to soil organic layer (SOL) depth at the stand scale in the lowland forests of Quebec's Clay Belt. Late-winter and early-spring temperatures and temperature at the end of the previous year's growing season were the major monthly level environmental controls of spruce growth. The effect of SOL on climate-growth relationships was moderate and reversed the association between tree growth and summer aridity from a negative to a positive relationship: trees growing on thin organic layers were thus negatively affected by drought, whereas it was the opposite for sites with deep (>20-30 cm) organic layers. This indicates the development of wetter conditions on sites with thicker SOL. Deep SOL were also associated with an increased frequency of negative growth anomalies (pointer years) in tree-ring chronologies. Our results emphasize the presence of nonlinear growth responses to SOL accumulation, suggesting 20-30 cm as a provisional threshold with respect to the effects of SOL on the climate-growth relationship. Given the current climatic conditions characterized by generally low-fire activity and a trend toward accumulation of SOL, the importance of SOL effects in the black spruce ecosystem is expected to increase in the future.

Reclamation of the Fresno type of black-alkali soil /

Mode of access: Internet.

Arkansas, Black, Red, Ouachita, and White River systems and their tributaries : hearings before the Committee on Flood Control, House of Representatives, Seventy-fourth Congress, first session, measures providing for the prevention of soil erosion, for flood control, for irrigation, for navigation, for constructing hydroelectric plants, and other betterments in the areas drained by the Arkansas, Black, Red, Ouachita, and White River systems and their tributaries. Februrary 14, 15, 16, and 19, 1935.

Riley J. Wilson, chairman.

Selected soil properties and bacterial abundance in the glacier forefields 'Black Valley Transect' and 'Glacier Transect' on Larsemann Hills, East Antarctica

Antarctic glacier forefields are extreme environments and pioneer sites for ecological succession. Increasing temperatures due to global warming lead to enhanced deglaciation processes in cold-affected habitats, and new terrain is becoming exposed to soil formation and microbial colonization. However, only little is known about the impact of environmental changes on microbial communities and how they develop in connection to shifting habitat characteristics. In this study, using a combination of molecular and geochemical analysis, we determine the structure and development of bacterial communities depending on soil parameters in two different glacier forefields on Larsemann Hills, East Antarctica. Our results demonstrate that deglaciation-dependent habitat formation, resulting in a gradient in soil moisture, pH and conductivity, leads to an orderly bacterial succession for some groups, for example Cyanobacteria, Bacteroidetes and Deltaproteobacteria in a transect representing 'classical' glacier forefields. A variable bacterial distribution and different composed communities were revealed according to soil heterogeneity in a slightly 'matured' glacier forefield transect, where Gemmatimonadetes, Flavobacteria, Gamma- and Deltaproteobacteria occur depending on water availability and soil depth. Actinobacteria are dominant in both sites with dominance connected to certain trace elements in the glacier forefields.

Soil N2O and CO2 emissions from cotton in Australia under varying irrigation management

Irrigation is known to stimulate soil microbial carbon and nitrogen turnover and potentially the emissions of nitrous oxide (N2O) and carbon dioxide (CO2). We conducted a study to evaluate the effect of three different irrigation intensities on soil N2O and CO2 fluxes and to determine if irrigation management can be used to mitigate N2O emissions from irrigated cotton on black vertisols in South-Eastern Queensland, Australia. Fluxes were measured over the entire 2009/2010 cotton growing season with a fully automated chamber system that measured emissions on a sub-daily basis. Irrigation intensity had a significant effect on CO2 emission. More frequent irrigation stimulated soil respiration and seasonal CO2 fluxes ranged from 2.7 to 4.1 Mg-C ha−1 for the treatments with the lowest and highest irrigation frequency, respectively. N2O emission happened episodic with highest emissions when heavy rainfall or irrigation coincided with elevated soil mineral N levels and seasonal emissions ranged from 0.80 to 1.07 kg N2O-N ha−1 for the different treatments. Emission factors (EF = proportion of N fertilizer emitted as N2O) over the cotton cropping season, uncorrected for background emissions, ranged from 0.40 to 0.53 % of total N applied for the different treatments. There was no significant effect of the different irrigation treatments on soil N2O fluxes because highest emission happened in all treatments following heavy rainfall caused by a series of summer thunderstorms which overrode the effect of the irrigation treatment. However, higher irrigation intensity increased the cotton yield and therefore reduced the N2O intensity (N2O emission per lint yield) of this cropping system. Our data suggest that there is only limited scope to reduce absolute N2O emissions by different irrigation intensities in irrigated cotton systems with summer dominated rainfall. However, the significant impact of the irrigation treatments on the N2O intensity clearly shows that irrigation can easily be used to optimize the N2O intensity of such a system.

Soil N2O emissions under N2-fixing legumes and N-fertilised canola: A reappraisal of emissions factor calculations

Introducing nitrogen (N)-fixing legumes into cereal-based crop rotations reduces synthetic fertiliser-N use and may mitigate soil emissions of nitrous oxide (N2O). Current IPCC calculations assume 100% of legume biomass N as the anthropogenic N input and use 1% of this as an emission factor (EF)—the percentage of input N emitted as N2O. However, legumes also utilise soil inorganic N, so legume-fixed N is typically less than 100% of legume biomass N. In two field experiments, we measured soil N2O emissions from a black Vertosol in sub-tropical Australia for 12 months after sowing of chickpea (Cicer arietinum L.), canola (Brassica napus L.), faba bean (Vicia faba L.), and field pea (Pisum sativum L.). Cumulative N2O emissions from N-fertilised canola (624 g N2O-N ha−1) greatly exceeded those from chickpea (127 g N2O-N ha−1) in Experiment 1. Similarly, N2O emitted from canola (385 g N2O-N ha−1) in Experiment 2 was significantly greater than chickpea (166 g N2O-N ha−1), faba bean (166 g N2O-N ha−1) or field pea (135 g N2O-N ha−1). Highest losses from canola were recorded during the growing season, whereas 75% of the annual N2O losses from the legumes occurred post-harvest. Legume N2-fixation provided 37–43% (chickpea), 54% (field pea) and 64% (faba bean) of total plant biomass N. Using only fixed-N inputs, we calculated EFs for chickpea (0.13–0.31%), field pea (0.18%) and faba bean (0.04%) that were significantly less than N-fertilised canola (0.48–0.78%) (P < 0.05), suggesting legume-fixed N is a less emissive form of N input to the soil than fertiliser N. Inputs of legume-fixed N should be more accurately quantified to properly gauge the potential for legumes to mitigate soil N2O emissions. EF’s from legume crops need to be revised and should include a factor for the proportion of the legume’s N derived from the atmosphere.