近16年来新疆耕地与人口变化相关分析

利用1990～2006年的统计数据,采用统计分析方法,建立了耕地与人口相关模型,在此基础上分析了近16年来新疆的耕地变化过程、地域分异特征、耕地与人口相关性变化趋势、以及不同地区耕地与乡村人口相关的区域差异。结果表明:近16年来新疆耕地面积呈现波动增加趋势,但增加速度缓慢,不同时段耕地年均递增率呈现高-低-高-低模式,耕地变化地域差异特征明显;利用2006年耕地与对应的乡村人口数据进行相关分析,发现耕地面积与乡村人口数之间存在着极显著的正相关关系;1990～2006年新疆耕地面积与乡村人口之间的相关性呈正相关,并达到了0.01水平的显著性,且不同地区乡村人口数与耕地面积之间的相关系数在不同时期差别较大;1990～2006年期间,人均耕地面积减少了0.0874hm2,年均递减率为1.46%,而劳耕密度呈现增长趋势,净增加0.1926人/hm2,年递增率为0.2754%,在不同时段人均耕地面积及劳耕密度的变化幅度及趋势不同。     

新疆地区近15年来土地利用时空变化及驱动力分析

以20世纪80年代末新疆土地利用数据库及2000年、2005年两期新疆遥感影像为信息源,结合土地利用变化数量和空间分析模型及马尔科夫过程,分析新疆近15年来的土地利用变化强度及各地类间的转移变化状况,揭示该区域土地利用的时空变化特征和规律.最后采用马尔科夫过程预测各土地利用类型的变化趋势,并对土地变化的驱动力进行分析.结果显示:耕地面积处于上升状态,其年变化幅度最大;林地面积总体呈减少趋势且减少部分主要被开发为耕地;草地面积总体呈下降趋势.水域面积不断增加.工矿居民建设用地增加迅猛.由马尔科夫过程预测结果显示自2000年以后,草地、林地面积逐年增加,耕地面积呈下降趋势.人口增长,农业科技进步和农业结构调整,政策因素,社会经济发展等是驱动新疆土地利用变化的主要因素.     

宁夏耕地压力动态变化规律分析

耕地是人类赖以生存的基本资源和条件,耕地压力指数是指最小人均耕地面积与实际人均耕地面积之比,是衡量区域耕地资源紧张程度及动态变化趋势的重要指标。文中以宁夏回族自治区为样本研究区,运用最小人均耕地面积和耕地压力指数模型对宁夏自1950-2007年耕地变化进行研究。结果表明:1950-2007年,宁夏人均耕地面积和最小人均耕地面积呈不断减小趋势,近50年分别减少0.39hm2和0.74hm2,受耕地面积变化、人口增长、粮食单产变化及政策等影响,耕地压力指数在波动中呈减小趋势,这与近年来宁夏推行的严格耕地保护政策、生态移民、科技兴农等措施密切相关。     

咸阳市耕地资源动态变化分析

依据1990-2003年咸阳市统计资料,运用因子分析方法,分析了咸阳市耕地面积变化的总体趋势、空间差异和驱动因子.结果表明:咸阳市耕地总体呈逐年减少态势,且空间差异显著;经济发展水平、人口增长和城市化水平是影响咸阳市耕地面积变化的3大因素.通过建立多元回归模型,预测出2004-2034年的耕地数量.研究结果将为合理利用和保护耕地资源以及咸阳市农业可持续发展提供科学依据.     

喀什地区近10a绿洲耕地变化及其地下水位效应分析

根据喀什地区绿洲耕地面积和地下水位实测数据,分析近10a来耕地面积和地下水的变化特征及其之间的关性。分析表明：1）近10a绿洲耕地面积呈现波动增加的态势,年均增长率3.40%,人均耕地面积经历从减少到增加的变化过程,年均递增1.14%;耕地空间变化区域差异明显,巴楚县耕地变化率最大,年均达11.49%,岳普湖县最低,为...     

基于3S的农牧交错区耕地动态变化研究——以内蒙古奈曼旗为例

本文利用3S技术,通过对1975、1985、1995和2005年的内蒙古奈曼旗TM影像的解译,提取出近30年来该地区耕地动态变化的信息。从耕地数量、变化速率以及耕地空间格局动态变化等方面对耕地的动态变化进行了全面的分析,并对其驱动机制进行了探讨。研究表明:近30年来,奈曼旗耕地面积呈增加趋势,而变化速度呈下降趋势;耕地主要向林地和固定沙丘地转化;耕地连通性指数、破碎度指数的变化呈波动趋势;耕地斑块数量的变化趋势与破碎度指数相同;耕地的分形维数随着人为干扰程度的增加呈现出逐渐降低的趋势。耕地在整个景观中的影响作用逐渐加强。耕地动态变化的主要驱动因素是耕地需求增加与土地退化之间的矛盾。     

西北干旱半干旱区耕地面积变化与人口、经济发展的相关关系研究——以甘肃省为例

基于甘肃省1997-2006年耕地十年变化的数据,研究了甘肃省经济发展过程中耕地面积变化的过程,并运用统计分析方法,对近十年来耕地变化与人口以及固定资产投资、人均GDP等经济指标进行相关分析.结果表明:耕地面积与人口呈相反趋势,与固定资产投资、人均GDP、城市化水平呈正" U"型三次曲线相关,即固定资产投资总额、人均G...     

新疆阿克苏地区耕地变化趋势及驱动力研究

阿克苏地区作为新疆的农业大区,随着人口规模的扩张,对耕地的需求不断增加,因此研究其耕地的变化具有重要的现实意义。论文利用1991-2005年的统计数据,分析了15年间耕地面积变化的总体趋势、空间差异及其驱动因子。结果表明:15年间阿克苏地区耕地总量经历了上升→下降→回升的过程;耕地变化除具有以全区总体变化为代表的普遍特征外,还具有明显的区域差异;通过文献调研和定量研究得知,15年来阿克苏地区耕地变化主要与政策因素有关,并与有效灌溉面积、粮食单产、年末牲畜存栏总量、总人口、国内生产总值等人口和社会经济发展因素显著相关。经综合分析,耕地需求增加与土地退化是导致阿克苏地区耕地变化的主要原因。     

甘肃省耕地数量变化特征及其对粮食安全的影响

利用51年的耕地统计数据和近年的土地利用详查变更数据,揭示了甘肃省土地利用结构和耕地面积变化的总体特征,1955～2005年,甘肃省耕地面积和人均耕地面积呈现出逐年下降趋势,而粮食产量和人均粮食产量却呈现出上升趋势,最小人均耕地面积和耕地面积压力指数虽逐渐减小,但耕地压力指数历年都大于1,说明此期粮食的供给小于需求,粮食处于不安全状态。运用回归分析方法、预测理论、最小人均耕地面积和耕地压力指数模型,对耕地面积变化的主要驱动因子进行了分析,在定量分析耕地数量变化和人口增长及经济发展关系的基础上,对未来15年耕地、人口、粮食、最小人均耕地面积和耕地压力指数进行了预测。结果显示:2006～2020年,耕地压力指数继续减小,且越来越接近1,这说明耕地面积-人口-粮食之间的供需矛盾减小,粮食安全形势有所缓解。     

咸阳市耕地变化特征及对粮食安全的影响

耕地资源和粮食安全不仅是国家层面的研究问题,也是区域层面的重要课题。文中利用55年的耕地统计数据和粮食总产量和人口数据,揭示了咸阳市耕地总体变化特征,分析了咸阳市耕地减少态势的空间差异,对粮食供需状况进行了分析和预测。研究结果表明:咸阳市的耕地面积在建国以后的55年内,经过小幅度的波动,总体上呈减少的趋势,而人均耕地面积持续减少;咸阳市各县区在近20年里耕地减少的幅度北部高于南部;咸阳市的粮食需求量随着人口的增长而增大,但是粮食的供给受多种因素的影响波动较大,总体上呈增长的趋势。预测结果表明,咸阳市的耕地面积还将继续减少,但是在提高复种指数和粮食单产的基础上,粮食供给在人均粮食消费量400kg/a.人情况下,未来10年还能保持较高的粮食自给水平,至2020年,咸阳市的粮食自给还能保持在90%的状态,仍将处于安全状态。     

Hymenopteran Parasitoids on Fruit-infesting Tephritidae (Diptera) in Latin America and the Southern United States: Diversity, Distribution, Taxonomic Status and their use in Fruit Fly Biological Control

We first discuss the diversity of fruit fly (Diptera: Tephritidae) parasitoids (Hymenoptera) of the Neotropics. Even though the emphasis is on Anastrepha parasitoids, we also review all the information available on parasitoids attacking flies in the genera Ceratitis, Rhagoletis, Rhagoletotrypeta, Toxotrypana and Zonosemata. We center our analysis in parasitoid guilds, parasitoid assemblage size and fly host profiles. We also discuss distribution patterns and the taxonomic status of all known Anastrepha parasitoids. We follow by providing a historical overview of biological control of pestiferous tephritids in Latin American and Florida (U.S.A.) and by analyzing the success or failure of classical and augmentative biological control programs implemented to date in these regions. We also discuss the lack of success of introductions of exotic fruit fly parasitoids in various Latin American countries. We finish by discussing the most pressing needs related to fruit fly biological control (classical, augmentative, and conservation modalities) in areas of the Neotropics where fruit fly populations severely restrict the development of commercial fruit growing. We also address the need for much more intensive research on the bioecology of native fruit fly parasitoids.     

Brief Guide for Authors

正Journal of Arid Land(JAL)is an international journal(ISSN 1674-6767;CN 65-1278/K)for the natural sciences,sponsored by the Xinjiang Institute of Ecology and Geography,Chinese Academy of Sciences and Science Press.It is published by Science Press and Springer-Verlag Berlin Heidelberg bimonthly.JAL publishes original,innovative,and integrative research from arid and semiarid regions,ad     

The parasitoid complex ofLiriomyza cicerina on chickpea (Cicer arietinum)

Liriomyza cicerina (Diptera: Agromyzidae) is an important pest on chickpea in Turkey. The objective of this study was to determine the parasitoids and rates of parasitism ofL. cicerina on chickpea (Cicer arietinum L.) during the 2005 and 2006 seasons in ?anl?urfa province, Turkey. Leaves with mines were sampled weekly and kept in the laboratory to observe and count emerging leafminer and parasitoid adults. Eight parasitoid species were collected: the braconidsOpius monilicornis Fischer andOpius tersus Foerster and the eulophidsDiaulinopsis arenaria (Erdös) andNeochrysocharis formosa (Westwood), which occurred in both the winter and summer seasons;Diglyphus crassinervis Erdös,Neochrysocharis ambitiosa Hansson,Neochrysocharis sericea (Erdös) andPediobius metallicus (Nees), which occurred only in the summer growing areas.Diaulinopsis arenaria was the predominant parasitoid with 4–7.7% parasitism rate whileN. ambitiosa andO. monilicornis were the second and third most predominant species. The results of these trials show that sinceDia. arenaria occurred throughout every season, it could potentially be used for control of the leafminerL. cicerina.     

Plant–herbivore asynchrony necessitates augmentative releases of the exotic beetle,Zygogramma bicolorata,to enhance the biological control of P arthenium hysterophorus

Systematic information on the quantitative impact of Z ygogramma bicolorata on the biology of P arthenium hysterophorus is crucial as the seeds of this weed continue to germinate from the accumulated soil seed bank throughout the year in the form of different germinating flushes, while the activity of the beetle ceases during winter as it enters diapause. Therefore, plant–herbivore interactions need to be explored to develop predictions of the overall impact of the introduced beetle on the weed. The findings revealed that defoliation by Z . bicolorata had a significant impact on the plant height, density and flower production in flushes F ₃, F ₄ and F ₅, but not in F ₁ and F ₂ that exhibited longer periodicity, profuse branching, a longer flowering period and maximum flower production and contributed mostly to the existing seed soil bank. Therefore, total depletion of the existing soil seed bank was not possible. Consequently, the effect of augmentative field releases of laboratory‐reared beetles was explored on F ₁ and F ₂ in February for three consecutive years (2011–2013). Before initiating the trial, random soil samples were taken from the plots that were assigned to the paired treatments (i.e. with the beetle and without the beetle [insecticide‐treated]) and it was found that the seed bank in those samples did not differ. The single release of Z . bicolorata adults at five per plant at the six‐leaf stage significantly reduced the soil seed bank, compared to without the biocontrol agent, irrespective of the flushes at the end of the season.     

Effects of the saprophytic leaf mycoflora on growth and productivity of winter wheat

The effects of the saprophytic mycoflora and its interference with cereal aphids on growth and yield of winter and spring wheat was studied in field experiments in 1980, 1981 and 1982.Yields varied between 5000 and 8000 kg dry matter of kernels per ha. The effect of the saprophytic mycoflora on yield was determined in different treatments: A) no control measures against cereal aphids and saprophytic and necrotrophic fungi, B) no control of cereal aphids, control of saprophytic and necrotrophic fungi, C) control of cereal aphids and control of saprophytic and necrotrophic fungi, D) control of cereal aphids and stimulation of saprophytic mycoflora and E) control of cereal aphids, no control of saprophytic and necrotrophic fungi nor stimulation of saprophytic mycoflora.Considerable differences in top densities of saprophytic mycoflora (10 times as large in A and D as in B and C) were determined. The consequences of these differences for the growth and productivity of wheat were minor. A negative effect of saprophytic mycoflora on the yield could not be detected in 1981 and 1982, whereas a small positive significant effect was found in 1980. This stimulation may have been due to competition between necrotrophic fungal pathogens and saprophytic mycoflora. As a result of favourable weather conditions necrotrophic fungal pathogens were very numerous in 1980 and could form an important yield reducing factor. Yield levels may effect the importance of the necrotrophic and saprophytic mycoflora as yield reducing factors. Additionally, in the presence of aphid honeydew captafol was found to be relatively ineffective against saprophytic fungi.     

Relationship Between Production of the Phytotoxin Prehelminthosporol and Virulence in Isolates of the Plant Pathogenic Fungus Bipolaris sorokiniana

A gas chromatographic method was developed to quantify the phytotoxin prehelminthosporol, which is a sesquiterpene metabolite of the plant pathogen Bipolaris sorokiniana. The toxin was extracted from mycelium or culture filtrates, pre-cleaned using solid phase extraction, and analyzed by gas chromatography as a trimethylsilyl-derivative. The detection limit of the method was 5ngl^–1 (signal to noise ratio 4:1) which corresponds to ca. 15ng prehelminthosporol per mg dry weight of mycelium or 15ng prehelminthosporol per ml culture filtrate. The total amount of prehelminthosporol (mycelium plus culture filtrate) increased with cultivation time when examined in six isolates of B. sorokiniana after 6, 9, 12 and 15 days of incubation. The screening experiment of 17 isolates for prehelminthosporol production after 8 days of incubation revealed significant differences in the toxin production between the isolates. The isolates with low toxin production had lower virulence towards barley roots compared to those with higher production of the toxin. However, the virulence did not increase with prehelminthosporol level among the high producing isolates. Prehelminthosporol was also analyzed in a number of related Bipolaris and Drechslera species. In addition to B. sorokiniana, three out of six Bipolaris species (B. setariae, B. zeicola, B. victoriae) produced prehelminthosporol, which indicates that ability to produce prehelminthosporol is conserved among closely-related Bipolaris species.     

Effect of botanical insecticides and bacterial toxins on the gut enzyme of the rice leaffolderCnaphalocrocis medinalis

The effect of botanical insecticides and bacterial toxins on gut enzyme activity of larvae of the rice leaffolderCnaphalocrocis medinalis (Guenée) (Insecta: Lepidoptera: Pyralidae) was investigated. Gut enzyme activities were affected by botanical insecticides and bacterial toxin individually and in combination. When fed a diet of rice leaves treated with botanical insecticides and bacterial toxins, in bioassays the activities of gut tissue enzymes — acid phosphatases (ACP), alkaline phosphatases (ALP) and adenosine triphosphatases (ATPase) — of rice leaffolder larvae were affected. When combined, the effect was more severe at a low concentration. Larvae that were chronically exposed to botanical insecticides and bacterial toxins showed a reduction in weight (59–89%) and exhibited a significant reduction in ACP, ALP and ATPase activities. The combination ofBacillus thuringiensis kurstaki and botanical insecticides caused a decrease of twofold in enzyme activity even at reduced concentration. A synergistic effect was found when botanical insecticides and bacterial toxins were combined at low doses. These effects were most pronounced in early instars. Clear dose-response relationships were established with respect to enzyme activity. In conclusion: (i) biopesticides are relatively safe and biodegradable; (ii) a synergistic effect of botanical insecticides and bacterial toxins was found; (iii) less expensive, readily available and naturally occurring biopesticides could be an alternative for organic and inorganic pesticides in controlling RLF. http://www.phytoparasitica.org posting Sept. 28, 2004.