Simulating farming practices within a region using a stochastic bio-decisional model: Application to irrigated maize in south-western France

Agricultural is a major contributor to environmental resource management problems. Modelling the distribution of agricultural land use to evaluate current situations or scenarios is an important issue for policy-makers and natural resource managers. A promising approach is the use of bio-decisional models based on decision rules. However, at the regional scale, the large number of farmers makes it difficult to identify decision rules, and the diversity of farmers' decisions is rarely considered. To this end, we developed SIMITKO, a spatialised and stochastic bio-decisional model, able to simulate the spatial and temporal variability in farming practices. We focused on the choice of varietal earliness and sowing practices of maize (Zea mays L.) in the Baïse sector (south-western France). Model development was based on statistical analyses of surveys of farmers’ practices to identify their current strategies, the best variables to describe the practices and the probabilities associated with the values of the variables for each strategy. We tested SIMITKO by simulating the dynamics of areas sown with maize. Comparing model predictions of practices to observed data showed generally good predictions of sowing dynamics but less satisfactory predictions of varietal earliness choices. Possible improvements are suggested.     

长时序海量土地利用时空数据统计优化方法

针对任意查询区域年度现状地类面积统计困难、长时序变更流量分析计算耗时等问题,提出基于时空变化图模型的统计优化方法。运用图的连通性原理,对查询统计区域内和边界处的要素实体进行分类,实现了时序快照统计优化算法,解决了任意查询区域时点现状统计困难的问题,提高了时序快照统计的效率。运用多商品流原理进行时空网络图约化性判定,实现了变更流量统计优化算法,减少了要素空间叠置分析次数,解决了长时序土地利用变化变更流量统计耗时问题,提高了统计的效率。最后,以2009—2012年琼海市土地利用数据为例,进一步验证优化算法的有效性和可行性。     

Analysis of spatio-temporal changes in forest biomass in China

Forests play a central role in the global carbon cycle.China's forests have a high carbon sequestration potential owing to their wide distribution,young age and relatively low carbon density.Forest biomass is an essential variable for assessing carbon sequestration capacity,thus determining the spatio-temporal changes of forest biomass is critical to the national carbon budget and to contribute to sustainable forest management.Based on Chinese for-est inventory data (1999-2013),this study explored spatial patterns of forest biomass at a grid resolution of 1 km by applying a downscaling method and further analyzed spatio-temporal changes of biomass at different spatial scales.The main findings are:(1) the regression relationship between forest biomass and the associated influencing factors at a provincial scale can be applied to estimate biomass at a pixel scale by employing a downscaling method;(2) for-est biomass had a distinct spatial pattern with the greatest biomass occurring in the major mountain ranges;(3) forest biomass changes had a notable spatial distribution pattern;increase (i.e.,carbon sinks) occurred in east and southeast China,decreases (i.e.,carbon sources) were observed in the northeast to southwest,with the largest biomass losses in the Hengduan Mountains,Southern Hainan and Northern Da Hinggan Mountains;and,(4) forest vegetation functioned as a carbon sink during 1999-2013 with a net increase in biomass of 3.71 Pg.     

Multi-time scale analysis of sugarcane within-field variability: improved crop diagnosis using satellite time series?

Within-field spatial variability is related to multiple factors that can be time-independent or time-dependent. In this study, our working hypothesis is that a multi-time scale analysis of the dynamics of spatial patterns can help establish a diagnosis of crop condition. To test this hypothesis, we analyzed the within-field variability of a sugarcane crop at seasonal and annual time scales, and tried to link this variability to environmental (climate, topography, and soil depth) and cropping (harvest date) factors. The analysis was based on a sugarcane field vegetation index (NDVI) time series of fifteen SPOT images acquired in the French West Indies (Guadeloupe) in 2002 and 2003, and on an original classification method that enabled us to focus on crop spatial variability independently of crop growth stages. We showed that at the seasonal scale, the within-field growth pattern depended on the phenological stage of the crop and on cropping operations. At the annual scale, NDVI maps revealed a stable pattern for the two consecutive years at peak vegetation, despite very different rainfall amounts, but with inverse NDVI values. This inversion is linked with the topography and consequently to the plant water status. We conclude that (1) it is necessary to know the crop growing cycle to correctly interpret the spatial pattern, (2) single-date images may be insufficient for the diagnosis of crop condition or for prediction, and (3) the pattern of vigour occurrence within fields can help diagnose growth anomalies.

不同土地利用方式对岩溶山区旱坡地土壤水分时空分异的影响

通过对岩溶山区贵州修文县2年的土壤水分定点观测,系统分析了研究区不同坡度下土地利用方式对土壤水分的影响。分析结果表明,在不同坡度之间,土壤水分的变化差异极为显著;在不同的土地利用方式条件下,蔬菜地的土壤水分变化与其他两种用地的差异极为显著,而裸地与小麦—玉米轮作地之间却没有显著差异。同一时间径流深虽然16°坡地>9.5°坡地>6.5°坡地,但土壤水分却存在9.5°坡地>16°坡地>6.5°坡地的关系,初步分析这是由土壤剖面质地差异所致,从剖面分布来看,土壤水分含量都随着深度的增加而增大。坡度和土地利用方式对土壤水分的影响主要集中在BC层以上,而在C层这种影响较弱,坡度因素的影响深度比土地利用方式小。     

毛乌素沙地樟子松人工林土壤物理性质的时空变异规律

以毛乌素沙地榆林沙区樟子松人工林土壤为研究对象,分析不同林龄樟子松人工林土壤质量含水量、土壤体积质量、孔隙度时空变异规律。结果表明,土壤质量含水量在流沙地为丘间地>迎风坡>背风坡>丘顶,在樟子松人工林为丘间地>背风坡>迎风坡>丘顶,并随土层深度增加而增加,0～5cm土层质量含水量樟子松人工林高于流沙地,5～25cm和25～50cm土层低于流沙地。土壤体积质量在流沙地为丘顶>迎风坡>背风坡>丘间地,在樟子松人工林为丘顶>中部(迎风坡、背风坡)>丘间地,随土层深度增加而增加,且樟子松人工林对应各层土壤体积质量均小于流沙地。毛管孔隙度均为丘间地>中部(迎风坡、背风坡)>丘顶,土壤孔隙度(总孔隙度、毛管孔隙度、非毛管孔隙度)随土层深度增加而降低,樟子松人工林对应各层土壤孔隙度均大于流沙地。随樟子松林龄增加,质量含水量和孔隙度分别增加1.32%～21.82%、2.88%～12.00%,土壤体积质量降低1.16%～7.12%。统计分析表明,所测指标总体上存在显著差异。     

辽宁地区近50年无霜期时空演变特征

结合GIS技术、气候倾向率以及突变分析方法,利用近50a辽宁省52个气象观测站的逐日气温资料对无霜期初日、终日以及持续日数的时空演变特征进行分析。结果表明:(1)区域平均无霜期初日以2.2d/10a的速率提前(P0.01),在1989年前后发生突变;终日和持续日数分别以1.9d/10a和3.9d/10a的速率延后和增多(P0.01),终日在1975年前后发生突变。辽宁大部地区无霜期日数以3～4d/10a速率增加(P0.01)。(2)不同基准年的气候平均值(A时段:1961-1990年,B时段:1971-2000年)有明显差异,B时段较A时段初日提前、终日延后、无霜期日数延长。(3)从年代际变化来看,无霜期日数在20世纪70年代的高值和低值区域较60年代有所扩大,80年代高值区再次扩大,低值区缩小,90年代较前者空间格局变化不大,2000年以后高值区已覆盖辽宁大部地区,低值区明显缩小。     

城镇地籍数据时空演变研究方法

建立城镇地籍数时空模型,运用时空分析方法,综合分析地籍数据的时间、空间和属性等各基本特征之间的相互关系,挖掘城镇地籍数据中的隐藏信息,探索研究城镇地籍数据空演变规律的方法。     

我国低温冷冻害的发生规律分析

本研究简要介绍了低温冷冻害的类型及影响,重点分析了我国冷冻害的时空格局,探讨了全国范围内冷冻害的发生情况.我国受低温冷冻害影响的范围非常广,其中东北和黄淮海地区是影响最大的两个区域,并且近十几年来我国黄淮平原及华中部分地区有加重趋势.云南和广东等华南和西南地区也经常出现不同程度的冷害.个别年份强度非常大.近20年来,我国低温冷冻害经历了减弱-增强-减弱的过程.1992～1999年是冷冻害影响最严重的时段,其中1998年全国总受灾面积867万hm-2,仅江苏、安徽两省就超过了500万hm-2.2000年及以后的几年强度有所降低,但平均每年的受灾面积仍高于370万hm-2.1986～1991年、1992～1999年、2000～2005年3个时段内各省区冷冻害发展变化趋势的分析表明,我国大部分省区冷冻害强度在不断加大,其中有8个省区年平均受灾面积上升辐度超过lO万hm-2.     

青虾泛素特异性蛋白酶9基因Usp9全长cDNA序列的克隆及表达分析

本研究首次克隆了青虾的Usp9 (ubiquitin-specific protease 9)基因全长 cDNA序列,并在青虾中使用荧光定量 PCR 技术首次检测了 Usp9 基因在不同组织和发育阶段中的表达变化。青虾 Usp9 基因cDNA全长 1259 bp,包括 162 bp的 5’ UTR, 978 bp的开放阅读框以及 116 bp的 3’ UTR。氨基酸序列比对分析显示,青虾 Usp9蛋白与太平洋牡蛎(Crassostrea gigas)、凤仙花熊蜂(Bombus impatiens)及灰短尾负鼠(Monodelphis domestica)的蛋白相似度分别为 99%、 97%和 95%。应用 MEGA5.1软件对青虾与其他物种的 Usp9氨基酸进行系统进化树分析,结果表明,青虾 Usp9与同为甲壳纲的钩额型蚤状溞聚为一支,具有最近的亲缘关系。采用荧光定量 PCR技术检测了 Usp9基因的时空表达,水温 28℃时, Usp9基因在青虾发育的后幼体发育期第 5天 PL5出现表达高峰。Usp9基因在 6种成体组织中均有表达,表达水平依次为：脑＞腹神经＞精巢＞卵巢＞肌肉＞肠。而在雌雄组织差异表达分析表明,精巢中Usp9基因表达量比卵巢的比值为 2.86,脑组织中雄虾的表达量比雌虾为 2.27,差异均为极其显著(P＜0.01)。这表明Usp9基因的表达和雄性偏向基因趋势是一致的（雄性表达：雌性表达≥1.5）。本研究为进一步开展青虾Usp9基因功能等相关研究奠定了基础,并可为青虾性别的遗传调控机制研究提供参考。