近30年来白洋淀湿地景观格局变化及其驱动机制

湿地是水陆相互作用形成的独特生态系统,其景观格局极易受到气候变化和人类活动的影响。利用1984—2014年的11期遥感影像数据,综合运用GIS技术和景观格局指数方法,对白洋淀湿地景观格局变化特征及其驱动力机制进行了分析。结果表明,1984—2014年期间,挺水植物和沉水植物呈减少趋势,农田和居民点持续快速增长,纯水体为"增加—减少—再增加"的趋势,林地和裸土地变化幅度不大。其中挺水植物一直是白洋淀最主要的景观类型,占研究区总面积比例达到37%—61%。农田的平均斑块面积最大,挺水植物的最大斑块指数和分维度指数最高,挺水植物和农田的聚集度指数最大,居民点、林地和裸土地空间分布离散,破碎化程度高,连通性差。1989—2004年白洋淀景观多样性指数呈减少趋势,景观格局趋于不稳定,同期聚集度指数上升,湿地连通性增加;1984—1989年和2004—2014年期间白洋淀多样性指数上涨,聚集度指数逐年下降,景观异质性增加。人口和社会经济发展是影响白洋淀景观格局变化的主要因素。     

贵州兴仁煤矿区农田土壤重金属化学形态及风险评估

为了解煤矿区周边农田土壤重金属污染状况,采集了贵州省兴仁县某典型煤矿区农田土壤样品64份,测定了土样中重金属(As、Cr、Pb、Zn、Cd、Hg、Cu、Ni)总量及各形态含量,采用单因子指数法、潜在生态风险指数法(Hkanson法)和风险评估编码法(RAC)对研究区主要土壤利用类型(水稻土、薏米地、植烟土和菜园土)中重金属进行潜在生态风险评估和环境风险评价.结果表明： 不同利用类型土壤中重金属含量除Zn外,其他元素均明显超过贵州省背景值.单因子指数法评价结果表明,As、Pb、Hg和Cu污染较为严重,均属重度污染.形态分析表明,土壤中重金属形态构成差异明显,酸可提取态As、酸可提取态Cd所占比例较高;Cr、Zn、Cu、Ni主要以残渣态为主;Pb主要以可还原态和残渣态为主;而Hg的酸可提取态、可还原态、可氧化态均占有相当比例,三者之和大于55%.重金属可利用度大小顺序为:As(63.6%)>Hg(57.3%)>Cd(56.4%)>Pb(52.5%)>Cu(45.7%)>Zn(32.8%)>Ni(26.2%)>Cr(13.2%).潜在生态风险指数表明,各类型土壤潜在生态风险(RI)〖JP2〗为:菜园土(505.19)>薏米地(486.06)>植烟土(475.33)>水稻土(446.86),均处于较高风险.风险评估编码法结果显示,As在水稻土、薏米地及植烟土中均处于高风险,在菜园土中处于中等风险;Cd、Hg均处于中等风险,Cr、Pb、Zn、Cu和Ni均处于低风险.因此,对该区域农田土壤进行管控时应重点考虑As、Cd和Hg污染.     

不同小麦品种茎秆特性及其与抗倒性的关系

以黄淮麦区优良品种矮抗58、周麦18、豫麦49、百农418为研究对象,采用田间试验与实验室分析相结合的方法,对不同小麦品种在不同生育时期的抗倒伏性状进行研究.结果表明: 茎秆机械强度在开花期至花后20 d处于较高水平,在花后30 d明显下降;倒伏指数在开花期最小,花后30 d最大,其余两个时期处于中间水平.相关分析表明,开花期机械强度与重心高度呈显著负相关,与纤维素、木质素含量呈显著正相关,倒伏指数与节长、株高、重心高度呈显著正相关,与纤维素、木质素含量呈显著负相关;花后10 d和花后20 d机械强度与节长、株高、重心高度呈显著负相关,与茎粗、纤维素、半纤维素、木质素含量呈显著正相关,倒伏指数这段时期正好与之相反;花后30 d机械强度与株高、重心高度呈显著负相关,倒伏指数与株高、重心高度呈显著正相关,与木质素含量呈显著负相关.因此,明确各个生育时期与抗倒性相关的茎秆特性,可为黄淮麦区高产抗倒性品种的选育提供依据.     

基于灾害风险综合指标的陕西省农业干旱时空特征

随着气候变化,农业干旱直接威胁粮食安全.本文以陕西省为研究对象,基于自然灾害风险理论,综合考虑干旱灾害影响因素,从致灾因子的危险性、承灾体的暴露性、环境的脆弱性和地区的抗旱能力4个风险要素选取指标,采用层次分析法确定指标权重,构建自然灾害风险综合指标,分析2009—2013年陕西省农业干旱时空特征.结果表明: 研究期间,陕北地区农业干旱风险略呈下降趋势;陕南地区呈急剧升高态势,以商洛市为甚;关中地区基本稳定,以咸阳市最高、西安市最低.陕西省农业干旱风险大体呈现从南向北逐渐递增现象.     

基于可见光植被指数的面向对象湿地水生植被提取方法

利用ESP分割工具确定最佳分割尺度,通过多尺度分割算法创建最优分割影像,基于微型无人机影像数据生成可见光植被指数,从一系列可见光植被指数中选取一组最优植被指数,建立决策树规则,利用隶属度函数对研究区自动分类,生成水生植被分布图.结果表明: 监督分类法的总体精度为53.7%,面向对象分类法总体精度为91.7%,与基于像元的监督分类法相比,面向对象分类法显著改善了影像分类结果,并大大提高了水生植被提取精度,监督分类法的Kappa系数为0.4,而面向对象分类法的Kappa系数为0.9.这表明利用微型无人机数据生成的可见光植被指数结合面向对象分类方法提取水生植被在该研究区是可行的,并能够应用到其他类似区域.     

Dynamics of the silver fir (Abies alba Mill.) natural regeneration in a mixed forest in the Central Apennine

The dynamics of the silver fir represent an important topic for researchers across Europe. Following its decline, which occurred in Europe after the last glaciation, the remaining relict areas became a very important laboratory for studying its conservation. The Central Apennine chain, particularly in Molise, represents one unique case where silver fir, Turkey oak and beech can be found within the same forest. This study focused on the forest structure of the Bosco Monteluponi where the closeness with Collemeluccio Man and Biosphere reserve has affected the diffusion of conifer within the forest. Consequently, the forest structure has shifted from even aged to uneven aged. The resulting complex forest structure offers new challenges for forest practitioners in the identification of silvicultural treatments, which identify and maintain the balance among the three species within the same forest. Particular importance was given to the silver fir natural regeneration in order to assess the forest suitability for conifer expansion. Results demonstrated that Monteluponi is strongly suitable for the in situ conservation of silver fir and offers a great opportunity for its diffusion.     

Health risk assessment of heavy metals and metalloids via dietary intake of a potential vegetable (Coriandrum sativum L.) grown in contaminated water irrigated agricultural sites of Sargodha,Pakistan

Levels of Mo, As, Se, Fe, Cu, Zn, Ni, and Pb were determined in a vegetable commonly consumed in Pakistan. Samples were collected from three different sites (Ratokala, Phularwan, and Mailowal) supplied with three different water sources. Mo and Pb in water and Mo and As in C. sativum were higher than the suggested standards at the international level. Lower bioconcentration factor and pollution load index were seen at Site-I than at other sites. A positive association was found between the rhizosphere metals and those of the vegetable at all three sites. Enrichment factor at three sites ranged from 0.28 to 10.39. The highest value of daily intake of metals was found for Fe (0.245 mg/kg/day) and of the health risk index for As (70.41) at the wastewater inundated site. It is inferred that uptake of Mo, As, Cu, Ni, and Pb through C. sativum represents a high health danger to the individuals using this vegetable.