中国秦岭地区树木年轮密度对气候响应的初步分析

采用秦岭四个地点的树木年轮样本,进行了密度量测,建立各自的最大密度与最小密度年表。分析结果表明,密度变异对气候变化有显著的响应,这些年表可以成为表征过去局地气候的代用资料。     

丝绸之路青海道吐蕃时期墓葬出土木材记载的森林干扰史

森林动态与气候变化及人类活动有着紧密的联系, 了解森林干扰的发生历史对准确预测全球变暖背景下的森林动态具有重要意义, 也可为理解历史时期的气候变化和人地关系演变提供线索。文章利用丝绸之路青海道沿线吐蕃时期3个墓葬中出土的78棵祁连圆柏(Juniperus przewalskii Komarov)原木作为研究对象, 利用树木年轮学方法分析了其干扰历史。结果表明: 在公元1世纪到公元8世纪, 该地区祁连圆柏个体平均出现了51个主要生长释放事件年与15个主要生长抑制事件年, 其中公元4世纪下半叶的干扰事件发生频率最高。在公共区间85~700 A.D. 期间, 该地区森林出现大范围生长抑制事件的主要时期为537~548 A.D., 大范围生长释放事件发生在372~393 A.D. 和561~574 A.D. 期间。墓葬周边现生祁连圆柏生长与气候因素的响应分析以及相关的历史资料显示, 气候条件由干转湿是导致该地区森林生长释放事件的重要原因, 吐谷浑与吐蕃到达柴达木地区后增加的森林采伐与森林破坏也可能促进了生长释放的发生。研究结果有助于进一步认识青藏高原东北部历史时期森林干扰的发生规律, 以及气候变化和人类活动对丝绸之路青海道沿线森林产生的影响。

     

玛曲湿地遥感影像提取及精度分析

以甘肃玛曲县为研究区,以区域湿地遥感信息提取为目标,采用TM多光谱数据和DEM数据,利用归一化植被指数和主成分分析得到的第一主成分作为分类特征,通过对数据的空间特征、波谱特征与统计结果的对比分析,构建湿地信息提取决策树模型,并与非监督分类法、最大似然法相比较,表明基于多特征决策树分类法能够用于湿地专题信息的提取,在研究区有较好的适用性。     

秦岭南坡佛坪1789年以来1~4月平均温度重建

采用秦岭南坡陕西佛坪龙草坪、光头山、三个包及三官庙建立的秦岭冷杉、油松和铁杉树轮宽度、密度年表, 分析树木生长对气候要素变化的响应关系, 重建了佛坪1789年以来1~4月平均温度变化, 并对其进行了变化特征分析。结果表明, 各样点的树木生长明显受生长季前期温度影响, 呈较为显著的正相关关系。利用多个样点的年表并引入主分量分析方法建立回归方程, 显著地提高了回归方程的稳定性和显著性, 进而提高了重建结果的可信度。功率谱分析结果表明, 佛坪1~4月平均温度变化具有显著的3~4年周期。而滑动t检验、滑动F检验和Lepage检验结果表明, 18世纪后期以来于1896年前后发生了10年时间尺度的方差突变, 表现为温度波动幅度的变化。     

面要素空间信息量的度量方法研究

 地图是空间信息的载体,地图空间信息的度量是地图信息传输理论的一个基础问题。地图空间信息主要包括地图要素的空间信息和要素分布的空间信息。地图空间信息是由要素的几何形态结构来体现,即要素的空间信息通过其几何形态特征描述。为此,本文以面要素为研究对象,提出一种以几何形态结构特征的面要素空间信息量度量方法。首先,从空间认知角度对面要素结构进行凸包分解,构建凸包树的面要素表达方法。然后,采用层次化策略,分别从结点的元素、邻域和整体三个层次来描述面要素几何形态结构,将面要素空间信息分解为几何形态信息和分布结构信息,结合面要素空间信息量的认知分析,给出了几何形态和分布结构特征的定量描述指标,并发展了基于几何形态结构特征的面要素空间信息量计算模型。最后,通过一组实验计算,进行了案例验证分析。     

采用高山松最大密度重建川西高原1917-2002年夏季气温

Having analyzed the tree ring width and maximum latewood density of Pinus den-sata from west Sichuan, we obtained different climate information from tree-ring width and maximum latewood density chronology. The growth of tree ring width was responded princi-pally to the precipitation in current May, which might be influenced by the activity of southwest monsoon, whereas the maximum latewood density reflected summer temperature (June-September). According to the correlation relationship, a transfer function had been used to reconstruct summer temperature for the study area. The explained variance of re-construction is 51% (F=-52.099, p<0.0001). In the reconstruction series: before the 1930s, the climate was relatively cold, and relatively warm from 1930 to 1960, this trend was in accor-dance with the cold-warm period of the last 100 years, west Sichuan. Compared with Chengdu, the warming break point in west Sichuan is 3 years ahead of time, indicating that the Tibetan Plateau was more sensitive to temperature change. There was an evident sum-mer warming signal after 1983. Although the last 100-year running average of summer tem-perature in the 1990s was the maximum, the running average of the early 1990s was below the average line and it was cold summer, but summer drought occurred in the late 1990s.     

Climatic significance of<Emphasis Type="Italic">δD</Emphasis> time series in tree rings from Tianmu Mountain

Based on cross-dating tree ring age from Tianmu Mountain, Zhejiang Province, theδD      

虚拟水战略新论

根据在我国干旱区的实践, 更新了对虚拟水战略的解释.首先, 辨析Allan虚拟水战略具有的局限性, 在此基础上采用扩展的分析框架, 重新定义了虚拟水战略: 贫水地区为了实现水安全, 提高生活质量, 充分利用各种社会资源, 打通优化配置水资源(实体水+虚拟水)渠道的一个过程; 然后, 阐述了实施虚拟水战略的关键是要找到发展二、 三产业的具体途径--即在更大的范围内形成正反馈环.最后, 结合生态经济的实践, 论证了甘肃河西干旱区张掖市当前采取的生态经济之路就是在实施虚拟水战略.     

The relationship between herders and trees in space and time in northern Cameroon

Extensive herding is an important activity in northern Cameroon, in terms of both the local social economy and local land management. However, this activity is strongly linked to the availability and accessibility of fodder resources. Due to territorial processes, such as land clearance and wood harvesting, this resource is receding and pasturelands are becoming fragmented. Herders are facing new challenges to secure their livelihoods, and, in this context, fodder trees are emerging as a key resource, allowing herds to subsist up to the end of the dry season. Increasingly, trees are playing a significant part in the herders' strategies to feed their herds in time and space and to 'root' their activities to particular lands. This trend requires an analysis of the importance of fodder trees in the definition of territorial strategies operated by herders in northern Cameroon, in the context of various herding systems (nomadic herding, agro herding using transhumance, and settled agro herding). A discussion of herding strategies needed to address the decreasing access to fodder resources highlights the problems of current extensive herding systems and leads to proposed alternatives.