Can modelling enable us to understand the rôle of humans in landscape evolution?

Landform-evolution models have typically failed to include human actions, or have done so only in a static, scenario-based way. This failure is despite the extensive empirical data that suggest rates of soil erosion are most sensitive to anthropic pressure. The CybErosion modelling framework overcomes this limitation by using an agent-based approach to simulating the dynamic interactions of people and their landscapes. The interactions simulated relate to basic processes of food acquisition (hunting, gathering and basic agriculture) in prehistoric communities. Simulations demonstrate the value of this approach in supporting the vulnerability of landform evolution to anthropic pressures, and demonstrate the limitations of existing models that ignore human and animal agency, which are likely to produce both quantitatively and qualitatively different results. The model is also a useful heuristic tool for understanding human-landscape interactions and for suggesting directions for future research. Despite the acknowledged limitations of agent-based approaches in simulating human populations, it is suggested that further research will be fruitful, especially if combined with a range of field evidence.     

GIS在人口重心迁移研究中的应用

利用GIS技术，建立甘肃少数民族人口重心研究的图形数据库和人口统计数据库，计算各主要民族人口重心及其移动轨迹，制作人口重心移动专题图件，并在此基础上对少数民族人口重心移动规律展开讨论。     

近20年来中国人口重心与经济重心的演变及其对比分析

采用近20年来中国各省（市、区）的人口、GDP、工业、农业、第三产业的产值及消费额数据，计算出其各年的重心坐标，定量表示出中国近20年来人口、GDP、工业、农业、第三产业及消费重心的动态演化过程。在此基础上分析了中国人口、经济发展、生活水平区域差异的动态变化及其之间的关系，以及各要素动态演化的驱动因子。结果表明：近20年来，中国人口重心表现为缓慢地向西南方向移动；GDP、工业、第三产业和消费额重心向东南方向移动。与中国几何中心比较，区域差异在总体上是扩大了；与人口重心相比较，东西方向呈不平衡态势发展，南北方向则开始趋于平衡；而农业重心则表现为无规律性变化。     

资源开发、环境保护与地球物理学

人口、资源、灾害与环境是困扰当代人类的几个重大问题.人口的增长,要求有更多的资源,而资源开发、利用的合理与否,又势必对环境产生有利或有害的影响;环境的改善或恶化,反过来又必然影响到资源的增减.因此,如何处理好它们之间的关系,使资源得到合理的开发和利用,同时又保护或改善环境,形成资源开发利用与环境保护改善之间的良性循环,应当是人类共同奋斗的一个目标. 本文依据一些实际资料论述了上述问题以及地球物理学在解决这些问题中所应起的作用.     

Dams and population displacement on China’s Upper Mekong River: Implications for social capital and social–ecological resilience

China is home to nearly half of the world’s 50,000 large dams, which provide irrigation, flood protection, and hydroelectricity. Most of these projects involve substantial population displacement, which can disrupt social capital, the webs of interdependence and support that community members maintain with one another through relationships of trust and reciprocity. We use new empirical evidence to examine the association between dam-induced displacement and social capital in China and interpret our findings in the context of social–ecological resilience theory. Our focus is on agricultural households on the Upper Mekong River, where four large hydropower dams have been constructed over the past twenty years.Our broad finding is that resettlement is associated with diminished social capital, as measured by two key indicators: inter-household exchange of financial resources, and inter-household exchange of agricultural labor. These effects differ across the four dam sites in the study based on local economic conditions and changes in resettlement policy. We find that population resettlement is associated with markedly lower levels of agricultural labor exchange. In an economically under-developed setting, this reduces the depth and breadth of social support that agricultural households rely on to produce crops for subsistence and income. This in turn diminishes social–ecological resilience because social capital is a key factor that helps agricultural or resource-dependent communities manage risk and adapt to changes and stressors.We consider the policy implications of our findings in the context of scientific and industry efforts to minimize social harm, promote economic vitality, and improve the sustainability of hydropower as a form of renewable energy.     

Wasp-waist populations and marine ecosystem dynamics: Navigating the “predator pit” topographies

Many marine ecosystems exhibit a characteristic “wasp-waist” structure, where a single species, or at most several species, of small planktivorous fishes entirely dominate their trophic level. These species have complex life histories that result in radical variability that may propagate to both higher and lower trophic levels of the ecosystem. In addition, these populations have two key attributes: (1) they represent the lowest trophic level that is mobile, so they are capable of relocating their area of operation according to their own internal dynamics; (2) they may prey upon the early life stages of their predators, forming an unstable feedback loop in the trophic system that may, for example, precipitate abrupt regime shifts. Experience with the typical “boom-bust” dynamics of this type of population, and with populations that interact trophically with them, suggests a “predator pit” type of dynamics. This features a refuge from predation when abundance is very low, very destructive predation between an abundance level sufficient to attract interest from predators and an abundance level sufficient to satiate available predators, and, as abundance increases beyond this satiation point, decreasing specific predation mortality and population breakout. A simple formalism is developed to describe these dynamics. Examples of its application include (a) a hypothetical mechanism for progressive geographical habitat expansion at high biomass, (b) an explanation for the out-of-phase alternations of abundances of anchovies and sardines in many regional systems that appear to occur without substantial adverse interactions between the two species groups, and (c) an account of an interaction of environmental processes and fishery exploitation that caused a regime shift. The last is the example of the Baltic Sea, where the cod resource collapsed in concert with establishment of dominance of that ecosystem by the cod’s ‘wasp-waist” prey, herring and sprat.     

Vegetation of Mangroves： Spatial and Temporal Pattern of itsDominant Populations in Futian National Nature Reserve

The community characteristics of mangroves in the Futian Nature Reserve,Shenzhen, China are given based on surveying of 33 quadrats in 4 transects which stretch from the higher tidal zone to the lower tidal zone. The results show that there are 6 community types in this area: Kandelia candel association, Avicennia marina association, A egiceras corniculatum association, Kandelia candel Aegiceras corniculatum association,degiceras corniculatum Kandelia candel association and Acanthus ilicifolius association.Kandelia candel, degiceras corniculatum and dvicennia marina dominate the typicalquadrats. Kandelia candel can be seen at almost all quadrats, Aegiceras corniculatumdistributes mostly toward the estuary and the higher tidal zone, Avicennia marina distributesmostly toward the bay and the lower tidal zone, Bruguiera gymnorrhiza occasionally occurs toward the Estuary with one or several individuals, Acanthus ilicifolius was common towardthe higher tidal zone, as an accompanying species, Derris trifoliata was common in manymature ouadrats. Totallv. 6 snecies of man~rove plants and 3 soecies of semi-mangrove plants appear in this research area. From the higher tidal zone to the lower tidal zone, the average diameter and basal area of mangrove trees increase gradually. According to the results, the dvicennia marina dominates in average diameter and basal area, and the degicerascorniculatum trees are on the contrary. From the transect ! to the transect 4, the importance value ot dvicennia marina, Bruguiera gymnorrhiza and Kandelia candel decreases, and degiceras corniculatum increases. In this area, the Kandelia candel population and Ae giceras corniculatum population are developing populations with many seedlings and saplings, but the Avicennia marina population is in a mature stage with few seedlings and not so many total individuals. According to this research, we suppose that Aegiceras corniculatum should be developed toward the estuary and the dvicennia marina association should be protected.     

南极夏季普里兹湾桡足类优势种的产卵量和种群结构

1998年12月－1999年1月在南极普里兹湾采用现场培养的方法对大、中型桡足类优势种尖角似哲水蚤（Calanoides acutus)、戈氏长腹水蚤（Metridia gerlachei)和巨锚哲水蚤（Rhincalanus gigas)进行了实验研究，同时根据浮游动物垂直拖网的样品分析了它们的种群结构。结果表明，在实验中，C.acutus和M.gerlachei的平均产卵量分别为13.3(5-49)和5（4－12）个／雌／天；R.gigas没有产卵。随后对获得的卵进行连续观察，所有的卵均没有孵化。通过标本分析发现，C.acutus夏季的种群结构为双峰态，尤其是陆冰缘站，新生个体主要是CI期桡足幼体，而越冬个体包括CIV、CV和雌性成体。R.gigas的种群结构特征不明显，新生个体为12月末发现的大量集中分布的无节幼体。M.gerlachei表现出和C.acutus相似的丰度分布特性，但其种群结构主要是成体和晚期幼体。     

黄、渤海及东海江豚的洄游和种群差异

江豚对食物没有明显的选择性,常随分布区优势饵料种类的变化而变化。探讨了江豚洄游与饵料分布的关系,并对黄、渤海和东海长江两地理种群的差异进行了比较。