Climatic variability and changing reproductive goals in Sub-Saharan Africa

Using 40 rounds of Demographic and Health Survey data from 18 sub-Saharan African countries, linked to high-resolution historical climate records, we analyze the relationship between climatic variability and fertility goals among reproductive-aged women. We find that, overall, women exposed to above-average temperatures report lower ideal family size and reduced probability of desiring a first or additional child. Results indicate that exposure to precipitation anomalies during the 12 months prior to the DHS survey is associated with a significant reduction in ideal family size, but longer 60-month spells of above-average precipitation are associated with increases in ideal family size. Effects of unusual precipitation are null for women’s fertility preferences at both shorter- and longer-term periods. Additional analyses show that this association varies across sub-populations defined by parity, education, residence in rural or urban areas, and region. In general, our results suggest that women exposed to adverse environmental conditions—namely abnormally hot or dry spells—will reduce their ideal family size and their preferences for having another child. In some cases, however, fertility goals may also decline during spells of favorable environmental conditions, possibly due to increased labor demands among women and their spouses. One implication of the observed links between climate variability and reproductive goals is that policymakers concerned with climate adaptation should work to ensure women have access to the necessary family planning resources needed to realize dynamic reproductive goals in a changing climate.     

SPLASH TRANSPORT OF ORGANIC CARBON AND ASSOCIATED CONCENTRATION AND MASS ENRICHMENT RATIOS FOR AN OXISOL,HAWAII

Rainsplash is an important component of interrill erosion. To date, few studies have critically examined the linkages between aggregate entrainment by splash and associated nutrient flux. An Oxisol was used in laboratory rainfall experiments with two different antecedent moisture contents (AMC) and ten different rainfall energy flux densities (EFD). Splash and soil organic carbon (SOC) flux increased with increased EFD regardless of initial AMC. Aggregates were not transported in proportion to their content in the original soil matrix, those of 2000–4000 μm and <105 μm were found to be the most resistant to splash. Energy required to detach 1 gC varied from a median of 1870 J for the 2000–4000 μm fraction to 120 J for the 425–850 μm fraction. Temporal variation in cumulative splash flux and carbon flux for various combinations of AMC and EFD indicated distinct patterns. Under dry AMC, splash increased during 1 h duration storms and this was explained by increased aggregate breakdown by air-slaking, decreased soil strength and increased erodibility as soil moisture increased. Wet soil runs exhibited the opposite pattern of decreased flux with time, probably indicating a complex response to limited aggregate availability, increased seal development by raindrop compaction, and transient water layer effects in drop impact craters. The formulation of mass-based SOC enrichment ratios (ER) clearly indicated preferential detachment and transport of splashed aggregates between 250 and 2000 μm. A reliance of chemical transport models on concentration-based ER values can be misleading, because it is the balance between nutrient concentration and sediment quantity that is important for soil quality and non-point source modelling.     

大别造山带花岗岩类和正片麻岩的Rb／Sr分区

根据花岗岩类和片麻岩的Ｒｂ／Ｓｒ比值和其他岩相学和地球化学性质,大别造山带可以分为下列四个带：（１）北大别北带：是一个灰色片麻岩和基性、超基性岩带,其灰色片麻岩的Ｒｂ／Ｓｒ比值为０．０１～０．０９;（２）北大别南带：为中酸性岩浆活动和强裂混合岩化的区域,其片麻岩的Ｒｂ／Ｓｒ比值为０．１１％～０．４０,花岗岩类为０．３％～０．９;（３）南大别带：为一构造混杂带,超高压变质作用和岩浆活动和混合岩化均有     

Advances in understanding the Kombolgie Subgroup and unconformity-related uranium deposits in the Alligator Rivers Uranium Field and how to explore for them using lithogeochemical principles

The Alligator Rivers Uranium Field (ARUF) includes the mined and unmined Jabiluka, Ranger, Koongarra and Nabarlek unconformity-related uranium deposits and several small prospects including the newly discovered King River prospect. Uranium mineralisation is hosted by a variety of metamorphosed Nimbuwah Domain lithologies that are unconformably overlain by the Kombolgie Subgroup, a basin package of unmetamorphosed arenites and mafic volcanics. All of the uranium deposits and prospects preserve an identical alteration assemblage that is subdivided into a distal and proximal alteration zone. The distal alteration zone comprises an assemblage of sericite and chlorite that replace albite and amphibole. In some cases, this alteration can be traced >1000 m from the proximal alteration zone that is dominated by uraninite, hematite, chlorite and sericite. Uranium precipitated in the basement as uraninite at 1680 Ma at around 200°C from a fluid having δ¹⁸O_fluid values of 3.0±2.8‰ and δD_fluid values of ?28±13‰ VSMOW reflecting an evolved marine source. These geochemical properties are indistinguishable from those recorded by diagenetic illite and chlorite that were collected from the Kombolgie Subgroup sandstones across the ARUF. The illite and chlorite formed in diagenetic aquifers, and where these aquifers intersected favourable basement rocks, such as those containing graphite or other reductants, U was precipitated as uraninite. Therefore, it is proposed that the Kombolgie Subgroup is the source for fluids that formed the deposits. A post-ore alteration assemblage dominated by chlorite, but also comprising quartz±dolomite±sulfide veins cut the uranium mineralisation at all deposits and has historically been recorded as part of the syn-ore mineralisation event. However, these minerals formed anywhere between 1500 to 630 Ma from fluids that have distinctly lower δ¹⁸O_fluid values around 1.5‰ and lower δD_fluid values around ?45‰ reflecting a meteoric water origin. Despite unconformity-related uranium deposits having a large alteration halo, they remain difficult to find. The subtle alteration of albite to sericite several hundred metres from mineralisation occurs in isolation of any increase in trace elements such as U and radiogenic Pb and can be difficult or impossible to identify in hand specimen. Whole rock geochemical data indicate that Pearce Element Ratio (PER) analysis and General Element Ratio (GER) analysis may vector into this subtle alteration because it does not rely on an increase in trace elements to identify proximity to ore. PER and GER plots, Al/Ti vs (2Ca + Na + K)/Ti, Na/Al vs (Na + K)/Al, K/Al vs (Na + K)/Al and (Fe + Mg)/Al vs (Na + K)/Al provide a visual guide that readily distinguish unaltered from altered samples. A plot of (Na + K)/Al and (Fe + Mg)/Al on the x-axis against the concentration of trace elements on the y-axis reveals that U, Pb, Mo, Cu, B, Br, Ce, Y, Li, Ni, V and Nd are associated with the most intensely altered samples. The lithogeochemical vectors should aid explorers searching for uranium mineralisation in a prospective basin environment, but exploration must first focus on the characteristics of the basin to assess its mineralisation potential. A holistic model that describes the evolution of the Kombolgie Subgroup from deposition through diagenesis to formation of the uranium deposits in the underlying basement rocks is presented and has application to other basins that are considered prospective for unconformity-related uranium deposits. The model outlines that explorers will need to consider the thickness of the sedimentary pile, its lithological composition relative to depositional setting, the depth to which the sediments were buried during diagenesis and the degree of diagenesis achieved, which may be time dependant, before deciding on the prospectivity of the basin.     

光强和营养盐对伪矮海链藻昼夜节律变化的影响 Ⅱ.碳水化合物、蛋白质及生化组成比

于1989年1月—1989年8月,用连续培养和半连续培养方法进行了伪矮海链藻碳水化合物、蛋白质和生化组成比率的日变化同光强、营养盐关系的研究。结果表明,碳水化合物、碳水化合物同叶绿素α和蛋白质的比值均呈现光照期升高而黑暗期降低的昼夜节律;蛋白质在光照期和黑暗期均有合成,但是,光照期的增长速率大于黑暗期的;蛋白质同叶绿素α的比值无明显的日变化。各指标的日变化幅度均随光强的增强和营养盐供应速率的增加而升高,因此,光和营养盐是影响各指标日变化的重要因素。     

海拔梯度及典型土地利用类型对北热带山地土壤有机质和综合肥力的影响

为深入了解北热带海拔梯度各山地土壤带及典型土地利用类型（次生林、香蕉园、橡胶林）土壤有机质（SOM）、综合肥力（SIF）分布特征,以云南省金平县蝴蝶谷地区为例,区分表层（0～20 cm）和亚表层（20～40 cm）,测定SOM、pH、全氮、全磷、全钾和速效氮磷钾,采用修正内梅罗指数法评价SIF,分析限制SIF的关键因素。结果表明,研究区海拔与SOM、SIF呈显著正相关,6个山地土壤带表层和亚表层SOM、SIF排序为棕壤带>黄棕壤带>黄壤带>红壤带>赤红壤带>砖红壤带（P<0.05）。无论表层还是亚表层,SOM和SIF均以次生林最大,香蕉园次之,橡胶林最小,次生林SOM显著大于香蕉园和橡胶林（P<0.05）,SIF则无显著差异。随着海拔升高,限制SIF的因素由速效氮、速效磷转变为速效磷和速效钾,且pH的限制逐渐加强,而维持和限制低海拔不同土地利用类型SIF的因素与同海拔段内自然土壤基本一致。未来山地开发利用过程中低海拔区域应该注重补充氮肥和磷肥,中高海拔区域注重补充磷肥和钾肥,同时调节适宜的pH更有助于土壤养分释放和植物吸收利用。综上,海拔梯度和...