Studying crop sequences with CarrotAge,a HMM-based data mining software

We have developed a knowledge discovery system based on high-order hidden Markov models for analyzing spatio-temporal data bases. This system, named CarrotAge , takes as input an array of discrete data – the rows represent the spatial sites and the columns the time slots – and builds a partition together with its a posteriori probability. CarrotAge has been developed for studying the cropping patterns of a territory. It uses therefore an agricultural drench database, named Ter-Uti , which records every year the land-use category of a set of sites regularly spaced. The results of CarrotAge are interpreted by agronomists and used in research works linking agricultural land use and water management. Moreover, CarrotAge can be used to find out and study crop sequences in large territories, that is a main question for agricultural and environmental research, as discussed in this paper.     

关中东部缓坡地面全新世土壤侵蚀与沉积发展演变规律研究

对华县古洪积扇全新世黄土一土壤剖面的磁化率、粒度进行分析研究，揭示了全新世以来缓坡地面面状流水侵蚀和沉积的发生规律。研究结果表明，晚更新世末期，由于黄土土质疏松，植被薄弱，在即将进入全新世时有自然侵蚀沉积发生；在全新世4000aB．P.之前，洪积扇特殊的环境生态条件造成土壤堆积时期土壤水分缺乏，成壤较弱，面状流水侵蚀与沉积活动不明显。自夏商时代以来，农业耕垦活动影响古洪积扇地表，促进了坡面流水侵蚀堆积过程，发生了面状流水侵蚀；从3100aB．P.开始气候干旱，人类活动强烈地影响着当地的生态环境，加速了面状流水侵蚀沉积；隋唐以来人类活动引起的加速侵蚀沉积则更进一步增强，这个过程反映土壤侵蚀呈现阶段性加速的趋势。由此可见，土壤侵蚀的加速是与人类的活动相伴随，随着人类活动强度的增强，土壤侵蚀在自然侵蚀的基础上，呈现加速趋势。     

松嫩平原西部不同土地覆被水盐动态对比研究

通过对6种土地覆被2003年6～10月水盐时空动态进行分析，对比不同土地覆被水盐动态变化差异，结果发现：采样期内，不同土地覆被(碱斑地除外)0-120cm剖面含水量均出现明显峰值，大豆地和羊草草地在7月底出现峰值，玉米地和向日葵地在8月初，退化草地则在8月底才达到，比羊草草地滞后了一个月。除羊草草地外，其他土地覆被剖面含水量变化呈W型，只是波动幅度各不相同。采样期内，羊草草地剖面含水量的相对变率最大，为74％，其他依次为退化草地、大豆地、向日葵地、玉米地，碱斑地最低，仅为6．4％。相对于农田土地覆被，在0～40cm，羊草草地、退化草地和碱斑地随盐渍化程度的加重，含盐量剖面变异逐渐减小，而农田的三种土地覆被之间变异比较接近。整个采样期，向日葵地储盐量随时间的变化呈下降趋势，其他土地覆被波动变化一致，都经历了下降-上升-下降过程，但波动幅度不同，且羊草草地在7月7日出现上升，其他4种土地覆被在9月8日开始出现滞后于含水量的变化。相对于采样初期，不同土地覆被含盐量的相对变率均为负值，农田的下降幅度大，草地次之，碱斑地最小。协方差分析表明：95％置信度下，土地覆被、土壤剖面和两者的交互作用对含盐量的影响差异显著。     

不同农业利用方式下湘南第四纪红壤的粘粒矿物学组成与表面电荷特性

用X-射线衍射分析技术和化学方法研究不同农业利用方式对湘南第四纪红粘土及其发育土壤的粘粒矿物学组成和表面电荷特性的影响．结果表明：湘南第四纪红壤的粘粒矿物组成以高岭石为主，其次是1．4nm过渡矿物．经过人为耕种尤其在水田条件下，蛭石和水云母的含量增加，铁的活化度增大．土壤表面电荷数量（CECpH3.2、CECp、CECv、AEC）和电荷零点（pH）的值也发生相应的改变．     

污水土地处理磷污染物迁移转化模拟讨论分析

根据磷在土壤中的迁移转化机理，进行了以土柱试验为基础的“污水土地处理条件下磷的迁移转化模拟试验”，总结了污水中的磷在土壤中迁移转化的规律，提出了定量模拟这一规律的迁移转化联合模型。联合模型为研究磷在土壤中的运动提供了定量化依据，避免了已有研究中将迁移和转化割裂研究造成的误差，丰富并完善了不同形态磷的迁移转化模型。     

黄土高原沟坡地土地生产力评价的指标体系与评价方法

通过对渭北黄土高原地区沟坡地土壤理化性质的分析和对当地社会经济状况的调查研究,应用层次分析法对沟坡地土地自然生产力和现实生产力进行了分析和评价.在分析过程中,把当地主要造林树种根系垂直分布特征及其根系抗旱性特性纳入了分析评价体系.结果表明,嘴头村和西坡村不同树种沟坡地上刺槐(Robinia pseudoacacia)的自然生产力属于中等稍微偏上水平,而山杏(Prunus armeniacia var. ansu)、油松(Pinus tabulaeformis)和侧柏(Platycladus orientalis)的自然生产力水平则较低.两地沟坡地上的现实生产力计算结果则证明刺槐和山杏两个树种表现出了较高的水平,具有较好的发展前途;而油松和侧柏的现实生产力水平则较低,其发展推广受到了限制.群众对沟坡开发治理的态度和对开发方案的认可对沟坡开发的成功起到了重要作用.     

苏打盐碱地养鱼稻田水体微生物区系研究

对松嫩平原苏打盐碱地养鱼稻田水体微生物数量及种类组成进行了初步研究。结果表明,养鱼稻田异养细菌数量为0.280万～30.716万mL-1,高于未养鱼稻田(P<0.05),其平均值的时间分布为水稻生长末期>中期>初期;养鱼稻田和未养鱼稻田放线菌和霉菌数量均较少。养鱼稻田大肠菌群数量为403.6～17934.2L-1,显著高于未养鱼稻田(P<0.01),其平均值的时间分布为水稻生长中期>初期>末期。异养细菌数量与鱼产量、总施肥量和有机肥施用量均呈极显著相关,与化肥施用量相关不显著;大肠菌群数量与鱼产量相关显著,与总施肥量相关不显著,但与有机肥施用量相关极显著。养鱼稻田中检测出10个科(属)异养细菌,优势菌为弧菌属(Vib rion)、气单胞菌属(Aeromonas)和芽孢杆菌属(Bacillus)。     

长春市不同土地利用生境土壤昆虫幼虫群落组成与生态分布

对长春市郊区天然次生林、市内公园风景林、郊区防护林和农田等土地利用生境进行土壤昆虫幼虫调查,研究土地利用差异对土壤昆虫幼虫群落特征的影响。研究区共捕获土壤昆虫幼虫35科411只,其中鞘翅目幼虫14科319只,双翅目幼虫13科64只,鳞翅目幼虫8科28只。研究结果表明:不同土地利用生境土壤昆虫幼虫群落组成与生态分布存在差异,防护林和农田土壤昆虫幼虫的类群数和个体密度显著减少;除农田外,其他生境土壤昆虫幼虫群落个体密度和类群数主要集中分布在0～5cm土壤层,生境凋落物的移除对土壤昆虫幼虫群落组成影响不明显;此外,鞘翅目、双翅目和鳞翅目幼虫对土地利用和植被类型变化的响应也不同。     

Individual dispersal status influences space use of conspecific residents in the common lizard, Lacerta vivipara

The effects of immigration on the behaviour of residents may have important implications for the local population characteristics. A manipulative laboratory experiment with yearlings of the common lizard (Lacerta vivipara) was performed to test whether the introduction of dispersing or philopatric individuals influences the short-term spacing behaviour of resident individuals. Staged encounters were carried out to induce interactions within dyads. The home cage of each responding individual was connected by a corridor to an unfamiliar “arrival cage” to measure the latency to leave their own home cage after each encounter. Our results showed that the time that pairs spent in close proximity was longer when a dispersing individual was introduced in the home cage. The latency to leave the home cage was longer after the introduction of a dispersing individual. These response variables were not influenced by the relative body sizes of contestants nor by the level of aggression towards each other. In contrast, the aggressive response was significantly influenced by the residency asymmetry established experimentally (“owner” of the home cage vs introduced individual). Our results suggest that the space use by resident individuals is influenced by the dispersal status of conspecifics. The potential ultimate causes driving this effect are discussed.     

Statistical inference on patch-specific survival and movement rates from marked animals

Empirical estimates of patch-specific survival and movement rates are needed to parametrize spatially explicit population models, and for inference on the effects of habitat quality and fragmentation on populations. Data from radio-marked animals, in which both the fates and habitat locations of animals are known over time, can be used in conjunction with continuous-time proportional hazards models to obtain inferences on survival rates. Discrete-time conditional logistic models may provide inference on both survival and movement rates. We use Monte Carlo simulation to investigate accuracy of estimates of survival from both approaches, and movement rates from conditional logistic regression, for two habitats. Bias was low (relative bias < 0.04) and interval coverage accurate (close to the nominal 0.95) for estimates of habitat effect on survival based on proportional hazards. Bias was high ( relative bias 0.60) and interval coverage poor ( = 0.26 vs. nominal 0.95) for estimates of habitat effect based on conditional logistic regression; bias was especially influenced by heterogeneity in survival and the shape of the hazard function, whereas both bias and coverage were affected by ‘memory’ effects in movement patterns. Bias estimates of movement rate was low ( relative bias < 0.05), but interval coverage was poor ( = 0.48–0.80), possibly as a result of poor performance of a Taylor series estimate of variance. An example is provided from a radio-telemetry study of 47 wintering American woodcock (Scolopax minor), illustrating practical difficulties in field studies to parametrize these models. We also discuss extensions of continuous-time models to explicitly include a movement process, and further examine tradeoffs between continuous and discrete models.