长武塬区苹果园和农田相互转换的深层土壤水环境效应

研究长武塬区苹果园和农田相互转换后0~1 000 cm土壤含水量特征，分析了苹果园土壤干燥化和苹果园转换为农田后土壤水分的恢复效应。结果表明：2、7、17、23、29 a苹果园200~1 000 cm的平均土壤含水量分别为22.8%、21.4%、16.8%、15.4%、14.9%。500~1 000 cm土层中，29 a苹果园平均土壤含水量（14.5%）高于23 a的果园（13.3%）；17~29 a的苹果园均表现为轻度干燥化；基于苹果园和农田转换后土壤水分变化情况估算，苹果园最大种植年限为21 a。苹果园转换为农田1、5、10 a后，农田200~1 000 cm土层土壤含水量分别为：15.3%、15.7%和16.2%，恢复到土壤稳定湿度以上的土层厚度分别为140 cm（1 a）、220 cm（5 a）和400 cm（10 a）。     

Climate change and its impacts on mountain glaciers during 1960-2017 in western China

Mountain glaciers are highly sensitive to climate change. In this paper, we systematically analyzed and discussed the responses of glaciers to climate change during 1960-2017 in western China by the methods of least squares and correlation analysis. Results show that the maximum temperature, minimum temperature, average temperature, and precipitation significantly increased in western China at the rates of 0.32°C/10a, 0.48°C/10a, 0.39°C/10a, and 11.20 mm/10a, respectively. However, the wind speed, hours of sunshine, snowfall, and snowy days displayed decreasing trends at the rates of -0.53 m/(s?10a), 3.72 h/10a, -2.90 mm/10a, and -0.10 d/10a, respectively. The annual percentage of glacier area decreased by approximately 0.42%, and the average glacier area decreased by 2.76 km²/a. Meanwhile, glacial shrinkages were greater in the Altay Mountains, Tanggula Mountains, and Qilian Mountains than in the other mountainous regions. Glacier accumulation decreased while melt volume increased at a rate of 2.7×10⁴ m³/a. The area of melt volume was 1.3 times that of the glacier accumulation area. The glacier mass balance (GMB) decreased substantially at a rate of -14.0 mm/a, whereas the equilibrium line altitude (ELA) showed an increasing trend at a rate of 0.5 mm/a. After 1997, the mass was smaller than -500.0 mm, indicating a huge loss in glaciers. Furthermore, relationships between ELA and GMB and various climatic factors were established. Temperature and precipitation demonstrated a significantly negative correlation, whereas wind speed and snowy days had significantly positive correlations with GMB. Snowy days also exhibited a remarkably negative correlation with ELA. The strong warming trend and less snowy days were thought to be the main factors leading to glacial melting, whereas the increase in precipitation, and reductions of sunshine hours and wind speed might slow glacial melting.     

1960-2009年毛乌素沙地腹地气候变化的多重时间尺度分析——以乌审旗为例

采用一维Morlet复值小波变换对毛乌素沙地腹地1960-2009年气候变化的时间尺度特征进行了分析,结果表明:50年来,毛乌素沙地腹地年平均气温上升的气候变化倾向率为0.25℃/10a,年降水量下降的倾向率大小为11.383mm/10a;年平均气温存在着28a、13a和6a,年降水存在9a、28a、7a、5a和14a的多重时间尺度上的复杂嵌套结构,气温变化以28a尺度的周期振荡最强,降水变化以9a尺度的周期振荡最强。     

Studies on very-low volume (VLV) water-based sprays for the control of cotton pests

We evaluated, water-based very-low volume (VLV) sprays of various pyrethroids at different dosage levels, comparing these with ultra-low volume (ULV) sprays for the control of cotton pests in the Nampula province of Mozambique. The results showed that karate (lambda-cyhalothrin) 2.5% SG at a dosage level of 15 g a.i./ha applied as VLV gave a significantly higher yield than karate 0.8% ULV (28 g a.i./ha). Also, karate 3.75% WG (12 and 15 g a.i./ha) gave a similar yield to that of karate 0.8% ULV (28 g a.i./ha). Karate 5% EC (15 and 20 g a.i./ha) gave a yield similar to Karate 0.8% ULV (28 g a.i./ha). Baythroid (cyfluthrin) 5% EC at 15, 22.5 and 30 g a.i./ha gave a yield similar to baythroid 1.2% ULV (36 g a.i./ha). Bulldock (beta-cyfluthrin) 12.5% SC at dosage levels of 6, 9 and 12 g a.i./ha gave a similar yield to that using baythroid 1.2% ULV (36 g a.i./ha). In all four trials, water-based VLV sprays gave a yield of cotton and degree of pest-control similar to those obtained with the ULV formulations at comparatively lower dosage levels. Integrated with other pest management practices, these could play an important role in the cost effective management of insect pests of cotton on small-scale farms in many countries.     

Modelling land use strategies to optimise crop production and protection of ecologically important weed species

There is a need to develop farming systems that enable both a satisfactory level of crop production and suitable environmental conditions for natural species. Wildlife‐friendly cropping techniques, such as a reduced amount of applied herbicide or a lower crop density, might be adopted in order to maintain populations of weed species of biological interest. An alternative might be to adopt an intensive cropping system in a part of the field and spare the other part as set‐aside or field margins, available for the natural development of plant species. The objective of this study was to present a method to compare two strategies for maintaining a desirable level of abundance of a given species of interest in agricultural areas, specifically (i) a strategy based on a wildlife‐friendly cropping system in a large cultivated area and (ii) a strategy based on a more intensive cropping system in a reduced area of cultivation, i.e. with land‐sparing. The principle is to calculate the ratio of crop production obtained with strategy (i) to the production obtained with strategy (ii) for a given target density of natural species. We show that the value of this ratio, and thus the relative performance of the two strategies, depends on the density of the weed species that can be maintained in an uncultivated ecological area. The method is applied in case studies of two plant species with contrasting ecology and conservation goals. The numerical results show that the strategy based on a wildlife‐friendly cropping system is more profitable in most situations.     

Seasonal patterns of dispersal of ascospores of Cryphonectria parasitica (chestnut blight)

Infected barks of chestnut blight cankers, caused by Cryphonectria parasitica , were collected from a naturally infected orchard and incubated at different temperatures. Cankers started to discharge ascospores about a week after incubation at 15–25°C; most ascospores were collected at 20 and 25°C. When incubated at 5, 10 or 30°C, only a few cankers released a small number of ascospores and only during the later stages of incubation. However, the rate of formation of perithecia was not affected by the incubation temperature. The number of airborne ascospores was monitored using a volumetric spore trap in a chestnut orchard during 1996 and 1997. In both years, the number of ascospores trapped daily varied greatly, but in general it increased sharply from March onwards, reached a peak in May, and then declined steeply. There was a significant correlation between daily counts of ascospores and air temperature. Time-series transfer function (TF) analysis showed a positive association of the daily number of ascospores with increasing temperature, rain events and wet/humid conditions. In general, values predicted by the TF model agreed well with the observed pattern. However, a multiple regression equation based on TF analysis failed to provide a satisfactory prediction of the daily number of ascospores.     

Relation between Soil Health, Wave-like Fluctuations in Microbial Populations, and Soil-borne Plant Disease Management

A healthy soil is often defined as a stable soil system with high levels of biological diversity and activity, internal nutrient cycling, and resilience to disturbance. This implies that microbial fluctuations after a disturbance would dampen more quickly in a healthy than in a chronically damaged and biologically impoverished soil. Soil could be disturbed by various processes, for example addition of a nutrient source, tillage, or drying-rewetting. As a result of any disturbance, the numbers of heterotrophic bacteria and of individual species start to oscillate, both in time and space. The oscillations appear as moving waves along the path of a moving nutrient source such as a root tip. The phase and period for different trophic groups and species of bacteria may be shifted indicating that succession occurs. DGGE, Biolog and FAME analysis of subsequent populations in oscillation have confirmed that there is a cyclic succession in microbial communities. Microbial diversity oscillates in opposite direction from oscillations in microbial populations. In a healthy soil, the amplitudes of these oscillations will be small, but the background levels of microbial diversity and activity are high, so that soil-borne diseases will face more competitors and antagonists. However, soil-borne pathogens and antagonists alike will fluctuate in time and space as a result of growing plant roots and other disturbances, and the periods and phases of the oscillations may vary. As a consequence, biological control by members of a single trophic group or species may never be complete, as pathogens will encounter varying populations of the biocontrol agent on the root surface. A mixture of different trophic groups may provide more complete biological control because peaks of different trophic groups occur at subsequent locations along a root. Alternatively, regular addition of soil organic matter may increase background levels of microbial activity, increase nutrient cycling, lower the concentrations of easily available nutrient sources, increase microbial diversity, and enhance natural disease suppression.     

陕南地区近47年来气温、降水变化特征分析

利用陕南地区7个气象站1961～2007年的气温和降水记录,运用线性趋势、距平分析、5年滑动平均,Morlet小波分析等方法,研究了陕南地区近47年来的气候变化特征。结果表明:近47年来,陕南地区气温呈波动上升趋势,其增长率为0.14℃/10a。春、秋、冬季气温在增加,并且冬季增暖最为明显,夏季气温略有降低。气温变化有明显的周期性,普遍存在着20a和3～5a的周期振荡信号;降水量呈减少趋势,平均每10a减少2.9mm。降水量的年际变幅表现为夏季>秋季>春季>冬季,春季和秋季降水减少,夏季和冬季降水增加,减少量大于增加量,导致春旱、秋旱加剧。Morlet小波分析表明降水在20a和4～9a的尺度上也有较强的周期振荡。     

塔里木河流域沙尘暴变化的多尺度特征研究

采用1961-2007年塔里木河流域37个气象站点的沙尘暴日数资料,在分析其空间变化格局的基础上,采用Morlet小波函数,分析了流域近47a来年、春和夏季沙尘暴变化的多时间尺度的复杂结构,确定了其年、春和夏季变化的周期和突变点。结果表明:流域沙尘暴的空间分布既受天气系统的制约,又受地形等环境因素的影响,有明显的地区性差异;47a塔里木河流域年沙尘暴在约2-6a、6-16和16a以上周期尺度上变化类型为多-少、多-少-多和多-少;春季沙尘暴在约2-8a、约8-15a和15a以上周期尺度上表现为多-少-多-少、多-少-多变化和多或少的变化。夏季沙尘暴在约2-6a、6-15a和15a以上周期尺度上表现为少-多-少、多-少-多和多-少的变化,各周期尺度上沙尘暴多在1980和1990年代较少;塔里木河流域年、春和夏季沙尘暴的年际周期变化明显,均存在约2-3 a左右的显著周期,春夏季沙尘暴与年沙尘暴变化小波方差较大且相近,说明春夏季沙尘暴较大程度地影响着年沙尘暴。     

北京市农作物病虫害远程预警信息系统构建

 北京市农作物病虫害远程预警信息系统基于B/S模型,其将病虫害预警过程分为浏览器端和服务器端两部分,并通过网络将用户和领域专家联系起来。该系统包含:病虫害检索、数据采集、数据查询、统计分析、报表汇总、气象数据查询、病虫害预测预报和系统管理8个子系统。构建本预警信息系统的意义在于实现北京市农作物病虫害信息永久保存、资源共享;加强农作物病虫害灾情远程监控、及时制订防治决策,最终降低损失。     

忍冬科的系统发育核糖体DNA ITS区序列证据

以败酱草科Valerianaceae的Centranthu rubber为外类群,使用Phylip 3.65软件对忍冬科Caprifoliaceae 12个属12个代表种的ITS区序列进行了系统发育分析.采用最大简约法分析获得了5个最简约树,步长为580,一致性指数(CI)和维持性指数(RI)值分别为0.783 2和0.741 5.利用5个最简约树获取严格一致树.结果表明:①荚蒾属Viburnum与接骨木属Sambucus是姐妹群,自展支持率100%;并与忍冬科内七子花属Heptacodium、锦带花属Weigela构成姐妹群,虽然自展支持率为60%,从遗传距离上可看出荚蒾属与忍冬科内其他属之间仍有较近的亲缘关系,所以支持荚蒾属和接骨木属置于忍冬科内.②忍冬属Lonicera与鬼吹萧属Leycesteria聚成一小支,并构成姐妹群,自展支持率为100%;并与毛核木属Symphoricarpos、莛子镳属Triosteum构成姐妹群,自展支持率为100%,故不支持将毛核木属置于北极花族内Linnaceae;北极花属Linnaea、六道木属Abelia、猬实属Kolkwitzia、双盾木属Dipelta聚成姐妹群,自展支持率为100%,说明四者亲缘关系较近,仍置于北极花族内.     

陕北地区冬季气温的时空变化特征分析

根据1960-2009年陕北地区逐月气温资料,运用Mann-Kendall法、小波分析、空间插值等方法,对陕北地区近50年来冬季气温的时空分布特征和突变、周期变化规律进行了分析。结果表明：冬季气温总体上呈现增暖的趋势,其线性增长率为0.55℃/10a,相当于近50年冬季气温升高了2.76℃。冬季气温存在15、10 a和...     

以树木年轮宽度资料重建湟水河过去248年来6-7月份河流径流量

基于树轮宽度指标,精确重建了黄河上游一级支流湟水河过去248年来6-7月份河流径流量,发现湟水河6-7月份径流量有明显的枯水期和丰水期的变化。重建结果与历史记载的相对旱涝时期比较吻合,证明了重建结果的可靠性。其中枯水期为:1753-1766年、1785-1802年、1815-1832年、1861-1887年、1918-1941年、1963-1978年、1993-1998年;丰水期为:1767-1784年、1803-1814年、1834-1860年、1891-1916年、1944-1961年、1979-1992年。周期分析表明,湟水河过去近250年6-7月份径流量有明显的2.00a、2.29a、2.31a、2.33a、2.35a、34.29a、40.00a和48.00a的变化周期。     

Introducing an abundance index for assessing weed flora in survey studies

This study was carried out to propose a simple abundance index (AI) of weed species, to describe the ranking of weeds in weed communities, and to evaluate weed flora. Based on a 4 year weed survey program conducted in Tehran province, the Thomas methodology for determining the relative abundance (RA) in weed communities was applied and a new, improved method (called the AI method) was introduced. Sixty-one irrigated wheat fields were selected using a stratified sampling procedure. The boundaries of each county in the province formed the strata. For the Thomas method, the data were summarized for each county using five quantitative measures for determining the RA of each species. For the AI method, three quantitative measures were used, including frequency, uniformity, and mean field density. In the Thomas method, the mean field density had a significant role in determining the RA of a species, while the frequency and uniformity had a less significant role. However, for determining the AI, the frequency and uniformity had a higher value than the mean field density. Higher values for these two parameters for a particular species indicates that this species was more compatible with the soil and climate conditions in which it was growing, while higher values for the mean field density for a particular species indicates that the species had a higher competitive or reproductive ability than other species. In the Thomas method, the weed species with a low mean density were less abundant and not a serious weed for agroecosysytems but, in the AI method, an invasive weed could be detected before the colonization stage.     

Effect of weed interference on Zea mays: Growth analysis

In order to investigate the effect of weed competition on corn, growth trials were conducted in Shushtar, Iran, using a comparative growth analysis. In this study, two sets of treatments were imposed, based on the phenological stages of corn development, using a randomized complete block design with three replicates. The results showed that barnyardgrass and redroot pigweed were the most dominant weeds in these trials. Increasing the duration of weed interference reduced the corn leaf area index gradually. The reduction in the corn leaf area index led to a decline in the crop growth rate as a result of a reduction in the ability of corn to capture light and its photosynthetic ability. The total dry matter and relative growth rate of corn were decreased when the weeds were removed later as a result of a reduction in the leaf area index. According to these results, the leaf area index has a critical role in weed–crop competition.     

The effects of combining modified sowing methods with herbicide mixtures on weed interference in wheat crops

In India, wheat is prone to being heavily infested with weeds, which cause considerable yield losses. Agronomic practices, including sowing method, influence weed interference in wheat growth. A herbicide mixture is usually more effective than a single herbicide for controlling a broad-spectrum of weeds. It may prevent weed species shift and delay resistance development in weeds. This study attempted to develop an integrated approach, combining a modified sowing method with applying a herbicide mixture for efficient weed management in wheat. We found that flat bed missing-row sowing resulted in significant reductions in: (i) the three-year mean population densities of grassy, broad-leaved and total weeds at 40 days after sowing (d.a.s), (ii) total weed population density and biomass (dry weight) at 60 d.a.s., compared to a mainly, furrow-irrigated raised bed system. Applying a tank-mix of fenoxaprop-p-ethyl at 0.08 kg/ha and isoproturon at 0.4 kg/ha applied 30 d.a.s. resulted in significant reductions in total weed population density and biomass, leading to a significant improvement in wheat growth and yield compared to either a weedy check or a regime of fenoxaprop-p-ethyl applied at 0.10 kg/ha. However, a combination of the flat bed missing-row sowing and tank-mix application of fenoxaprop-p-ethyl 0.08 kg/ha and isoproturon 0.4 kg/ha 30 d.a.s. resulted in higher wheat yield through better management of weeds compared with other sowing/ weed control combinations.     

Morphological variation of star dune and implications for dune management: a case study at the Crescent Moon Spring scenic spot of Dunhuang,China

Aerial photographs and 3-D laser scans of a 90-m high star dune at the Crescent Moon Spring scenic spot in Dunhuang, China, are used to investigate the changes in dune morphology on timescales from months to decades. The result revealed that relative-equilibrium airflow strength in three wind directions of northeast, west and south was an important condition for the stability of star dunes with limited migration. Transverse and longitudinal airflows exerted a crucial impact on variation processes of star dune morphology. Controlled by transverse airflows, the easterly winds, the east side was dominated by wind erosion; and strong deposition occurred on the south-south-east arm with a maximum deposition rate of 0.44 m/a in the 46-a monitoring period, causing the east side becoming steep and high. Controlled by longitudinal airflows, the westerly winds, the west-north-west side was mainly eroded and the north arm migrated from west to east with a rate of 0.30 m/a, causing the dune slope becoming gentle and elongate. The local air circulation(southerly winds) exerted a significant impact on the development process of the star dune. Due to the influence of human activities, the south side present surface processes from a concave profile to a convex profile in 46 a, which is a potential threat to the Crescent Moon Spring. The results indicate that rehabilitating the airflow field at most is a crucial strategy to the protection of Crescent Moon Spring from burial. Opening up the passage of easterly, westerly and southerly winds through intermediately cutting the protection forest, demolishing the enclosed wall and changing the pavilion into a porous pattern have been suggested to protect the Crescent Moon Spring from burial.     

河西走廊东部积雪的时空演变特征分析

利用河西走廊东部5个气象站1961—2007年近47 a的逐月积雪深度和积雪日数的常规观测资料,分析河西走廊东部最大积雪深度和积雪日数月、季节和年的空间分布以及时间变化特征。结果表明:受海拔高度、地理位置以及天气系统等影响,河西走廊东部积雪日数、最大平均积雪深度和极端最大积雪深度的分布从东南向西北递减,高海拔地区多于低海拔区,山区多于平原区。时间变化上,积雪日数47 a来呈平稳变化趋势,震荡减少,变率很小,积雪深度呈增加趋势;河西走廊东部积雪日数最多出现在1月,最少出现在9月,积雪深度最大出现在3月,最小出现在12月;积雪日数冬季最大,春季次之,秋季最小;积雪深度春季最大,秋季次之,冬季最小;相关系数法分析表明,积雪日数和积雪深度都是冬季的变化主导了年尺度的变化;河西走廊东部积雪日数1990s中期以前以6~7 a、9~10 a和2~3 a的周期为主,1990s中期以后周期主要表现为6~7 a和2~3 a;积雪深度1970s中期以前以6~7 a和2~3 a周期为主,1970s中期~1990s中期9~10 a、12~13 a和2~3 a反应明显,1990s中期以后周期又表现为6~7 a和2~3 a。     

艾比湖湿地自然保护区克隆植物群落空间格局及其对水盐胁迫的响应

克隆植物对水盐胁迫的响应不仅在个体水平上,在种群分布格局和种群关联水平上也有一定的响应特征。利用Ripley’s K(r)函数和L(r)函数,对艾比湖湿地自然保护区4种克隆草本植物组成的混生群落进行点格局分析和关联分析。结果表明：“密集型”克隆植物花花柴（Karelinia caspia）、芦苇(Phragmites australis)在0~5 m尺度上多为集群分布;“游击型”克隆植物罗布麻（Apocynum venetum）、白麻（Poacynum pictum）在0~1 m尺度上多为随机分布,在1~4.5 m尺度上集群分布,在4.5~5 m尺度上为均匀分布;4种植物间除花花柴和芦苇为负关联关系外,其他多为正关联关系。在较强的水盐胁迫环境下,克隆植物更倾向于集群分布,这与克隆植物的生理整合作用以及种间正关联关系有关。     

陕西省退耕还林工程区植被覆盖度的变化分析

利用MODIS NDVI数据和像元二分模型计算的植被覆盖度,比较分析退耕还林工程区与周边区域、主要土地利用类型、不同坡度耕地植被覆盖度变化程度和趋势。结果表明：（1） 陕西省退耕还林区植被覆盖度从2000年到2011年呈现显著的增长趋势,增长速率高于周边区域;（2） 退耕还林区植被覆盖变化百分率≥10%的面积占79.8%,≤-10%所占面积不及1%;（3） 退耕还林区植被覆盖度显著增加的面积占其总面积的70.6%,显著减少的面积仅占0.1%,植被覆盖度显著增加的情况主要出现在未利用地、草地、林地和耕地,显著和极显著降低的发生在城乡、工矿、居民用地和极少部分耕地;（4） 坡耕地植被覆盖改善比例大,坡耕地植被覆盖改善对于耕地植被改善贡献较大。在陕西省气候呈现暖干化发展趋势背景下,退耕还林区植被覆盖度呈现显著增长趋势,增长速率高于周边区域,坡耕地、林地、草地均比其他类型有明显的增加,退耕还林政策实施区域取得了良好的植被恢复效果。