Crustal thickness and adakite occurrence in the Philippines: Is there a relationship?

Adakites are increasingly being recognized worldwide in a variety of tectonic settings. Models on the formation of this geochemically distinct class of volcanic rocks have evolved from partial melting of subducted young, hot oceanic slabs to magmatism resulting from oblique subduction, low‐angle or flat subduction, or even slab‐tearing. Some workers have also pointed to the partial melting of thickened crust to explain the generation of adakitic melts. Rare earth element ratios from adakites and adakitic rocks in the Philippines were used in this study to obtain approximations of the levels where they were generated. These were tied to available geophysical data that defines the crustal thickness of the areas where the samples were collected. High Sm/Yb and La/Yb ratios denote the involvement of amphiboles, and in some cases garnet, in the generation of adakites and adakitic magmas. The presence of amphibole and garnet as residual phases suggests high pressures corresponding to thicker crust (～30 to 45 km). Adakites and adakitic rocks formed through processes other than melting of subducted young oceanic crust would need ≥30 km to account for the heavy rare earth element signatures. If mantle fractionation is not the process involved, crustal thickness is critical to generate adakites and adakitic rocks.     

Is anthropogenic land subsidence a possible driver of riverine flood-hazard dynamics? A case study in Ravenna,Italy

We investigate possible changes in flood hazard over a 77-km² area around the city of Ravenna. The subsidence rate in the area, naturally a few mm year^?1, increased dramatically after World War II because of groundwater and natural gas extraction, exceeding 110?mm year^?1 and resulting in cumulative drops larger than 1.5?m. The Montone–Ronco river system flows in the southern portion of the area, which is protected against frequent flooding by levees. We performed two-dimensional simulations of inundation events associated with levee breaching by considering four different terrain configurations: current topography and a reconstruction of ground elevations before anthropogenic land subsidence, both neglecting and representing the main linear infrastructures (e.g. roads, artificial channels). Results show that flood-hazard changes due to anthropogenic land subsidence (e.g. significant changes in computed water depth and velocity) are observed over less than 10% of the study area and are definitely less important than those resulting from construction of the linear infrastructures.     

ENSO–climate fluctuation–crop yield early warning system—A case study in Jilin and Liaoning Province in Northeast China

Crop yield is very sensitive to climate variability. The El Niño–Southern Oscillation (ENSO) is one of the most important contributors to global climate fluctuation, and therefore has a major impact on agricultural production. In this study, we structure an ENSO–climate fluctuation–crop yield early warning system to model the maize yield in Jilin and Liaoning Provinces in Northeast China. The system, which consists of a weather generator and a Model to capture the Crop Weather relationship over a Large Area (MCWLA), is not only capable of simulating the maize yield both at the provincial (regional) scale and the grid scale, but can also provide the exceedance probability of yield. Simulation results show maize yields in El Niño years to be higher on average than those in neutral years, while yields in La Niña years are the lowest. Spatially, the central part of the study area always shows a higher yield than other parts of the study, while yields in the northeast and northwest parts are relatively lower, no matter how high or low the exceedance probability and whatever the ENSO phase. Our study strongly implies that such a warning system shows considerable potential for application in other areas of China.     

Is there a great unconformity between Xiamaling and Longshan formations in the North China Craton?

The existence of a 0.3 Ga "great unconformity" between the Mesoproterozoic "Undefined System" Xiamaling Formation and the "Neoproterozoic" Longshan Formation has long been controversial.In this study,stratigraphy,sedimentology,detrital zircon dating,lithium isotope,and major and trace elements were applied to systematically analyze their relationship.Results demonstrate that coarse to fine sandstone-mudstone normal cycles with different grades and thicknesses exist from the Xiamaling to the Long...     

Extreme climate events,migration for cultivation and policies:A case study in the early Qing Dynasty of China

Based on the historical records of the annual increase in the workforce (men older than 16 years of age), the annual new taxed cropland in the Shengjing area (Northeast China), the extreme climate events in North China, and related management policies in Northeast China during 1661―1680, a case study has been conducted to investigate the relationship between the extreme climate events in North China and the migration to Northeast China for cultivation. This study has found that the migration to Northeast China for cultivation from 1661 to 1680 was a response to the drought events that occurred in North China. The upsurge of migration, which occurred in 1665―1680, was a response to the drought period during 1664―1680 in North China while the fewer disasters period in Northeast China. There were three migratory peaks during the upsurge of migration, which corresponded to the three drought events. The peaks of migration, however, often lagged behind the drought events about 1―2 years. The encourag-ing-migration policy, which was adopted to encourage cultivation in Northeast China, did not produce much migration into the region in the early Qing Dynasty. It did, however, provide a policy background, which ensured more than 10000 migrants per year to Northeast China when North China suffered from drought/flood disasters. As a response to the highest peak of migration induced by the severe droughts in North China during 1664―1667, a prohibiting-migration policy restricted further migration to Northeast China was carried out in 1668. Although the prohibiting-migration policy could not entirely stop the migrants fleeing from famine in North China to Northeast China, the migrants and cultivation were significantly reduced under the policy. The frequent changes of the policy on the years when taxation started after the land was cultivated were also related to climate events. The extreme climate events in North China, migration to Northeast China for cultivation, and the related management poli-cies showed an impact-response chain, which reflected the interaction among extreme climate events, human behavior, and policies.     

Complexity analysis of precipitation using the Lempel–Ziv algorithm and a multi-scaling approach: a case study in Jilin province,China

Precipitation is an important part of the hydrologic cycle, and its complexity is closely related to surface runoff and changing groundwater dynamics, which in turn influences the accuracy of precipitation forecasts. In this study, we used the Lempel–Ziv algorithm (LZA) and a multi-scaling approach to assess precipitation complexity for 1958–2011 by analyzing time series data from 28 gauging stations located throughout Jilin province, China. The spatial distribution of normalized precipitation complexity was measured by LZA, a symbolic dynamics algorithm, and by a multi-scaling approach, which is described by fractals. In addition, the advantages and limitations of these two methods were investigated. The results indicate that both methods are applicable and consistent for calculating precipitation complexity, and that the degree of relief is a primary factor controlling precipitation complexity in the mountainous area; in the plain terrain, however, the prominent influencing factor is climate.     

Do macrophytes, diatoms and non-diatom benthic algae give redundant information? Results from a case study in Poland

We analyzed species composition and abundance of macrophytes, diatoms and non-diatom benthic algae, water chemistry and habitat structure of 24 river sites in Poland, in order to better understand which parameters structure macrophyte and benthic algae communities. Community patterns for macrophytes and diatoms are most closely related, while macrophytes and non-diatom benthic algae have the weakest relationship. Environmental parameters best explaining community patterns are channel substrate parameters for non-diatom benthic algae, and a combination of channel substrate and river bank characteristics for submerged macrophytes, emergent macrophytes and diatoms. Among the organism groups investigated, the diatom community pattern is best correlated to the environmental data similarity matrix. We hypothesize that the results can be explained by the shorter generation time of diatoms compared to macrophytes, and by a higher dispersal rate of diatoms compared to macrophytes and non-diatom benthic algae. This has several practical consequences for bioindication: (1) Diatoms are usually the organism group most closely following environmental parameters, for both increasing and decreasing impact. (2) Since the biotic indices developed for the Water Framework Directive are meant to primarily indicate ecological changes, not water chemistry, the nature of diatoms to closely reflect water chemistry is not necessarily advantageous. (3) The applicability of macrophyte and probably also non-diatom benthic algae indices is more locally restricted, while diatom indices are applicable to greater areas. (4) In ecosystems which are subject to changing environmental conditions, differences in biotic indices between macrophytes, diatoms and non-diatom benthic algae are to be expected. These differences could provide information relating to ecosystem stability. (5) In stable ecosystems, analyzing one of the three organism groups “diatoms”, “non-diatom benthic algae” and “macrophytes” will be sufficient to characterize the quality element “macrophytes and phytobenthos”, as required by the Water Framework Directive. However, in ecosystems subject to increasing pressure, macrophytes likely will have a tendency to indicate “too good”, while in ecosystems subject to decreasing pressure, diatoms will have a tendency to indicate “too good”.     

Modeling urban growth with GIS based cellular automata and least squares SVM rules: a case study in Qingpu–Songjiang area of Shanghai,China

A critical issue in urban cellular automata (CA) modeling concerns the identification of transition rules that generate realistic urban land use patterns. Recent studies have demonstrated that linear methods cannot sufficiently delineate the extraordinary complex boundaries between urban and non-urban areas and as most urban CA models simulate transitions across these boundaries, there is an urgent need for good methods to facilitate such delineations. This paper presents a machine learning CA model (termed MachCA) with nonlinear transition rules based on least squares support vector machines (LS-SVM) to simulate such urban growth. By projecting the input dataset into a high dimensional space using the LS-SVM method, an optimal hyper-plane is constructed to separate the complex boundaries between urban and nonurban land, thus enabling the retrieval of nonlinear CA transition rules. In the MachCA model, the transition rules are yes–no decisions on whether a cell changes its state or not, the rules being dynamically updated for each iteration of the model implementation. The application of the MachCA for simulating urban growth in the Shanghai Qingpu–Songjiang area in China reveals that the spatial configurations of rural–urban patterns can be modeled. A comparison of the MachCA model with a conventional CA model fitted by logarithmic regression (termed LogCA) shows that the MachCA model produces more hits and less misses and false alarms due to its capability for capturing the spatial complexity of urban dynamics. This results in improved simulation accuracies, although with only less than 1 % deviation between the overall errors produced by the MachCA and LogCA models. Nevertheless, the way MachCA model use in retrieving the transition rules provides a new method for simulating the dynamic process of urban growth.