基于RS与GIS的广州市森林景观格局时空分异研究

以TM影像和野外调查资料为数据源,基于3S技术对1986-2006年广州市森林空间格局进行动态分析。结果表明:1986-2006年广州市森林景观斑块数量增加,平均斑块面积减小,景观结构破碎化程度有上升趋势,主要表现在:多样性指数、分维数增大,聚集度、均匀度减小,在空间和类型上局部变化不同于整体表现。自然地理条件、人口增长、政府政策是导致景观格局变化及其区域差异的主要驱动力。随着城市扩展、农田开发等人类干扰的不断加剧,森林景观生态环境保护与经济开发之间的矛盾将愈加突出。     

海底油气藏及天然气水合物的时频电磁辨识

提出了伪随机多频海洋电磁法观测方案.采用伪随机多频信号作为激励场源,多偏移距同线偶极-偶极同时观测,相关辨识海底地电系统的频率特性和冲激响应,可以在时间域和频率域同时辨识海底高阻薄层.在时间域,瞬变冲激时刻可以直接指示海底地层电导率的变化;在频率域,利用多个频率的电场响应计算的频散率及其道闻变化量,相对相位道间变化量对高阻薄层有很好的反映.从而实现对海底油气及天然气水合物的多参数辨识.     

中国人口收缩的城乡分异特征及形成机理

在县市尺度上对2000-2010年人口收缩区的城乡分异特征进行分析,划分出城增乡减型、城乡双收缩型和城减乡增型等类型,并建立人口收缩城乡分异的理论分析框架,探讨了不同类型的形成机理,主要的发现如下:①2000-2010年,人口收缩单元占比约为38.6％,城增乡减型单元占据绝对主体,达到34.5％,而"城乡双收缩型"和"...     

斯里兰卡亚洲象栖息地生境质量时空变化及分异特征

斯里兰卡亚洲象栖息地是全球重要的亚洲象保护区,象群分布密度约为其他地区的10倍,但由于生境破碎与丧失以及人象冲突等原因导致亚洲象数量急剧下降。对斯里兰卡亚洲象栖息地的生境质量监测与评估能够为亚洲象及其栖息地的保护政策制定与规划提供理论依据,并在全球物种多样性保护中具有重要意义。为评估斯里兰卡亚洲象栖息地的生境质量,综合考虑亚洲象栖息地需求以及影响亚洲象栖息地的关键要素,应用InVEST-HQ模型来估算生境质量指数,同时分析亚洲象栖息地生境质量在海拔梯度及植被覆盖梯度上的分布状况;随后引入空间自相关分析方法在像元尺度上探讨亚洲象栖息地生境质量的空间分布模式与时间演化过程,进而分析栖息地内不同保护区和气候分区的生境质量所存在的空间分异特征。研究结果表明：在空间分布上,斯里兰卡亚洲象栖息地生境质量具有高度聚集性,空间异常值不显著。生境质量高值区主要集中在中低海拔、植被覆盖情况较好、保护区范围密集的区域;生境质量低值区集中于耕地面积大、海拔偏高的区域。在梯度分布上,斯里兰卡亚洲象栖息地生境质量对海拔和植被覆盖度均具有显著线性相关关系,且在较低海拔和较高植被覆盖度梯度上存在聚集现象。在区域尺度上,斯里兰卡亚洲象栖息地生境质量存在显著的地域差异性。栖息地内自然保护区的生境质量明显高于非自然保护区,其中严格自然保护区的生境质量相对较高;热带雨林气候带的生境质量高值聚类大于其余气候分区,而热带疏林草原气候带与热带季风气候带生境质量受到季节性降水的影响较大,高值像元占比偏少。在时间尺度上,斯里兰卡亚洲象栖息地的生境质量总体呈现先降低后趋于平缓的态势。1995年—2010年,生境质量高值聚类占比明显减少,低值聚类占比缓慢上升;2010年—2020年生境质量低值占比有小幅度下降,高值聚类逐渐增加,生境质量逐渐稳定并呈缓慢上升的趋势。     

膨胀岩的判别与分类标准

膨胀岩的判别与分级是膨胀岩研究的重要内容。本文在分析和总结了前人研究成果的基础上,提出了一种以膨胀岩中亲水矿物成分的含量为基础控制指标,以岩块的干燥饱和吸水率、极限膨胀量、极限膨胀力为主要控制指标新的标准。并利用新的标准对文献中的工程实例进行了分析应用。     

川滇西部地区钾质煌斑岩特征及其成因

川滇西部地区钾质煌斑岩带产物扬子板块西缘与三江褶皱带之间的过渡地带，侵位于老第三系地层。岩石化学特点具有中等含量钾、钛和钠、铝弱饱和，属岛弧环境的钙碱性煌斑岩与板内环境的钾镁煌斑岩（超钾）之间的过渡类型。微量元素Sr相对于Rb,Ba,K等元素具有明显的负异常，是地幔交代作用的产物。区域上与其伴生的壳源型花岗岩侵位在前，分布于西侧；碱性岩层中；钾质煌斑岩侵位在后，分布于东侧，属反序侵位序列，为喜山期陆壳碰撞、褶皱造山运动所触发的被动地幔作用产物。     

2008年初极端寒冷天气对荔枝龙眼成花的利弊分析

2008年初玉林市出现了一次与历史同期相比持续时间最长,平均温度最低、日照时数最少、总降水量居历史第二位的极端寒冷天气过程。通过对2008年1~4月份荔枝龙眼的观测和调查资料进行分析后发现,这次阴冷无霜的天气过程对荔枝龙眼的成花是既有利,也有弊,但总体上是弊大于利。因为持续长时间的低温和日照严重不足既抑制了冬梢,也抑制了花芽分化,最终导致了成花率明显偏低、花质差、雌花比率低、花期短等不良后果。鉴于这次罕见的极端寒冷天气对荔枝龙眼成花的影响,今后应从提高中长期天气预报准确率和栽培管理技术等方面来做好应对全球气候变暖背景下极端气象灾害的防御工作。     

Significance of selective crystal entrainment and differential crystal-melt separation in petrogenesis of granites from the Tongbai orogen

Partial melting has been shown to be an important mechanism for intracrustal differentiation and granite petrogenesis. However, a series of compositional differences between granitic melt from experiments and natural granites indicate that the processes of crustal differentiation are complex. To shed light on factors that control the processes of crustal differentiation, and then the compositions of granitic magma, a combined study of petrology and geochemistry was carried out for granites (in the forms of granitic veins and parautochthonous granite) from a granulite terrane in the Tongbai orogen, China. These granites are characterized by high SiO₂ (>72 wt%) and low FeO and MgO (<4 wt%) with low Na₂O/K₂O ratios (<0.7). Minerals in these granites show variable microstructures and compositions. Phase equilibrium modelling using P–T pseudosections shows that neither anatectic melts nor fractionated melts match the compositions of the target granites, challenging the conventional paradigm that granites are the crystallized product of pure granitic melts. Based on the microstructural features of minerals in the granites, and a comparison of their compositions with crystallized minerals from anatectic melts and minerals in granulites, the minerals in these granitoids are considered to have three origins. The first is entrained garnets, which show comparable compositions with those in host granulites. The second is early crystallized mineral from melts, which include large plagioclase and K-feldspar (with high Ca contents) crystals as well as a part of biotite whose compositions can be reproduced by crystallization of the anatectic melts. The compositions of other minerals such as small grained plagioclase, K-feldspar and anorthoclase in the granites with low Ca contents are not well reconstructed, so they are considered as the third origin of crystallized products of fractionated melts. The results of mass balance calculation show that the compositions of these granites can be produced by mixing between different proportions of crystallized minerals and fractionated melts with variable amounts of entrained minerals. However, the calculated modal proportions of different crystallized minerals (plagioclase, K-feldspar, biotite and quartz) in the granites are significantly different from those predicted by melt crystallization modelling. Specifically, some rocks have lower modes of biotite and plagioclase, whereas others show lower K-feldspar modes than those produced by melt crystallization. This indicates that the crystallized minerals would be differentially separated from the primary magmas to form the evolved magmas that produce these granites. Therefore, the crystal entrainment and differential melt-crystal separation make important contributions to the composition of the target granites. Compared with leucogranites worldwide, the target granites show comparable compositions. As such, the leucogranites may form through the crystal fractionation of primary granitic magmas at different extents in addition to variable degrees of partial melting.