科技支撑有望实现退耕还林经济效益内隐向外显转化——陕西省山阳县退耕还林实施状况调查

秦巴山区退耕还林3 810.68万亩,约占全国退耕还林总面积的10%。调查发现,秦巴山区退耕还林工程实效中存在着生态效益外显与经济效益内隐的矛盾。其主要原因在于缺乏科学规划和科技指导。陕西山阳县通过科技指导和技术示范有望实现退耕还林生态效益与经济效益双赢的目标。     

Short- and long-term effects of site factors on net N-mineralization and nitrification rates along an urban-rural gradient

Long- and short-term effects of urban site factors on net N-mineralization and nitrification rates were investigated in oak stands along an urban-rural land-use transect in the New York City metropolitan area. We used reciprocal transplants of undisturbed soil cores between urban and rural forests to determine the relative importance of long-term effects (mor vs. mull soils, quality of soil organic matter, and deposition of N) vs. short-term effects (soil temperature) of urban factors in controlling field N-transformation rates along the gradient. In addition, undisturbed soil cores from surface (A, Oe horizons) and subsurface (B horizon) soil were collected from urban, suburban, and rural stands and allowed to incubate in these respective sites to compare the net effect of all urban factors with transplanted-core results. The transplant experiment revealed that soil type (long-term) affected net N-mineralization and nitrification rates. Urban soils nitrified nearly 6.3 and 5.4 times more than rural soils incubating in urban and rural stands, respectively (p = 0.003 and p = 0.002, respectively). Similarly, in rural stands total accumulation of inorganic N was 87% higher in urban than in rural soils, whereas in urban stands, urban soils mineralized 83% more N than rural soils (p = 0.043 and 0.08, respectively). Comparing soils incubating in their native locations, urban soils incubating in urban stands mineralized more than 2.5 times the amount of N than rural soils incubating in the rural stands (p = 0.019). By contrast, urban soils incubating in urban stands exhibited a 8-fold increase in nitrification over rural soils incubating in rural stands (p = 0.008). As with the transplanted cores, the urban and suburban environments had a positive effect on net rates of N-mineralization and nitrification in both surface and subsurface layers of soil. The surface layer of suburban and urban stands had a 3- and 2.3-fold higher accumulation of net inorganic N than rural stands (ANOVA, p = 0.05). Similarly, in the subsurface layer both urban and suburban stands had 2.6-fold higher net N-mineralization rate than rural stands (ANOVA, p = 0.01). Along this urban-rural gradient, soils in oak stands exhibit higher net nitrification and, to a lesser extent, net N-mineralization rates in urban and suburban stands than in rural stands. Results from the transplant experiment and in situ measurements of surface and subsurface soil indicate that long-term effects (mor vs. mull soils, N deposition) contribute to the higher N-transformation rates in urban and suburban stands. As a result of these effects, urban and suburban stands have the potential for higher losses of N than rural stands.     

大数据背景下网络借贷的信用风险评估——以人人贷为例

在大数据时代,网贷平台每天流动着海量交易数据。为充分利用这些数据控制信用风险,运用数据挖掘算法建立了信用风险评估模型。由于网贷数据多为非平衡数据,所以通过多次尝试使用SMOTE算法进行处理,提高了模型评估性能。研究发现:随机森林模型更适合用于信用风险评估,其次是CART、ANN、C4.5。用户的婚姻、房/车产(贷)等信息重要程度较低,而公司规模、工作时间等信息,历史借款、信用评分等信用档案信息在信用风险评估中尤为重要。     

Riparian woody plant diversity and forest structure along an urban-rural gradient

Changes in riparian woody plant assemblages are anticipated in the southeastern United States due to increases in urbanization rates. Because riparian forests serve important roles in maintaining water quality and biodiversity, understanding how they respond to urbanization is crucial. The objective of this study was to examine forest structure and woody vegetation diversity indices of riparian communities in response to an urbanization gradient in West Georgia, USA. Measures of forest structure and diversity were compared to measures of urbanization and land cover. Although Liquidambar styracifluaand Quercus nigrawere dominant species in the forest stand and regeneration layer for all riparian communities, the invasive, non-native shrub Ligustrum sinense was the most dominant species observed in the regeneration layer for urban, developing, and agriculture communities. The proportion of non-native species in the forest stand and regeneration layer decreased and Shannon diversity of the regeneration layer increased with increasing distance from the urban center. Shifts in diversity indicate that anthropogenic disturbance may subdue the ability of diverse communities to resist non-native plant invasions.     

清末川边藏区的林事活动

为挽救西藏地方的危局，清廷于光绪三十一年(1905)任用赵尔丰为川滇边务大臣，实施“倚康治藏”方略。数年间，赵尔丰等人在川边辖境做了许多抗英、拒俄、实边、固藏的工作，深受学界好评。本文专论川边藏区鲜为人知的林事活动，如森林保护、植树造林、漆液采割、纸张生产以及边茶贸易、药材经营等，并指出其在实边方面的重要作用。     

清代黔东南锦屏苗族林业契约之卖契研究

清代黔东南文斗林业契约主要分为卖木又卖地契、卖木不卖地契、卖栽手三类.卖木又卖地契与内地绝卖契相类似,但有自己的特点,大量的需要十年、二十年才能获取预期收益的卖木不卖地契、卖栽手契的存在,说明了锦屏苗民对契约的信心,也旁证了当年人工林业经济的繁荣.     

Nonparametric Tree‐Based Predictive Modeling of Storm Outages on an Electric Distribution Network

This article compares two nonparametric tree‐based models, quantile regression forests (QRF) and Bayesian additive regression trees (BART), for predicting storm outages on an electric distribution network in Connecticut, USA. We evaluated point estimates and prediction intervals of outage predictions for both models using high‐resolution weather, infrastructure, and land use data for 89 storm events (including hurricanes, blizzards, and thunderstorms). We found that spatially BART predicted more accurate point estimates than QRF. However, QRF produced better prediction intervals for high spatial resolutions (2‐km grid cells and towns), while BART predictions aggregated to coarser resolutions (divisions and service territory) more effectively. We also found that the predictive accuracy was dependent on the season (e.g., tree‐leaf condition, storm characteristics), and that the predictions were most accurate for winter storms. Given the merits of each individual model, we suggest that BART and QRF be implemented together to show the complete picture of a storm's potential impact on the electric distribution network, which would allow for a utility to make better decisions about allocating prestorm resources.     

东晋南朝时人对南方山林的地理认知

汉魏以前，中原人将南方视为畏途，其地理认知十分粗疏。这一状况在永嘉南渡后发生很大改变。本文从认知主体和载体两个层面，着重分析作为南渡北人及其后裔的文人、僧侣以及地方官员在认知重点和表达方式上的差异，进而论述对各区域的认知特点。文章认为，对南方山林认知的提升开阔了以原先北方为主体的观念世界，为文学审美拓展了新途径，并触及了生物气候地带性规律。     

A classification updating procedure motivated by high-content screening data

The current paradigm for the identification of candidate drugs within the pharmaceutical industry typically involves the use of high-throughput screens. High-content screening (HCS) is the term given to the process of using an imaging platform to screen large numbers of compounds for some desirable biological activity. Classification methods have important applications in HCS experiments, where they are used to predict which compounds have the potential to be developed into new drugs. In this paper, a new classification method is proposed for batches of compounds where the rule is updated sequentially using information from the classification of previous batches. This methodology accounts for the possibility that the training data are not a representative sample of the test data and that the underlying group distributions may change as new compounds are analysed. This technique is illustrated on an example data set using linear discriminant analysis, k-nearest neighbour and random forest classifiers. Random forests are shown to be superior to the other classifiers and are further improved by the additional updating algorithm in terms of an increase in the number of true positives as well as a decrease in the number of false positives.