毛乌素沙地天然臭柏群落种子产量、种子库及幼苗更新

采用样方调查法,研究了毛乌素沙地臭柏(Sabinavulgaris)群落的种子产量、种子库及幼苗更新。结果表明:毛乌素沙地天然臭柏群落的球果丰富,约为3093. 83粒/m2,种子产量为9118. 5粒/m2,优良种子达2954. 4粒/m2。5种立地条件间的土壤种子库差异大、质量低,种子优良度最高的也仅为3. 7%。土壤种子集中分布于0 ~5cm土层内,并随着土壤深度增加,优良种子数由0~5cm的30. 52粒/m2减少到5~10cm的1. 3粒/m2。5 种立地中当年幼苗数的平均值仅为7. 98株/m2,最高的(A类立地)为14. 7株/m2,仅占表土优良种的30%左右,最低的(D类立地)已经丧失了更新能力。臭柏群落内种子更新苗少,而且种子更新集中在少数滩地小生境中。种子库小、质量差、更新环境的丧失是限制臭柏群落天然更新与拓展的主要因子。     

古尔班通古特沙漠南缘浅层风沙土含水量空间变异

2008年5月,在古尔班通古特沙漠南缘梧桐沟区段设置200 m×50 m样地,均匀选取180个样点进行样方的植被、地形和地貌调查,并且采取表层(0～10 cm)和次表层(10～30 cm)土壤样品进行土壤含水量分析。借助地统计软件GS~+和ArcGIS地统计模块分析研究区土壤含水量在沙垄不同地貌条件下的空间变异规律。结果显示:两层土壤水分的半方差函数值拟合为指数模型;表层和次表层土壤水分的变程分别为37.8 m和21.3 m,偏基台值与基台值的比值[C/(C_0+C)]分别为75.1%和75.6%,说明两层土壤水分具有强烈的空间自相关性,也表明土壤水分的变异主要由结构性差异所引起,客观地反映了研究区土壤水分的空间格局特征。克里格插值图显示,土壤水分随地势的升高而增大,平均数分析表明,0～10 cm土壤含水量由高至低的变化趋势是:垄顶>迎风坡>背风坡>垄间地,而10～30 cm则为:迎风坡>垄顶>垄间地>背风坡。     

青海湖东沙地不同植被恢复措施下土壤水分变化特征

土壤水分是沙地植被格局和过程改变的主要驱动力,也是干旱半干旱区植物生长最大的限制因子。沙漠地区的土壤水分表现出明显的空间异质性。以高寒半干旱沙地青海湖东沙地为研究区,以栽植人工固沙植物(小叶杨、樟子松、沙棘和乌柳)的沙丘和自然固定沙丘(沙蒿为优势种)作为研究样地,探讨不同固沙植物影响下的沙丘不同地貌部位土壤水分变化特征。结果表明:(1)土壤水分的季节变化受降水、植被蒸腾作用和地表蒸发的共同影响,不同物种的分布模式具有差异性,但都表现为7月的土壤含水量最高。(2)同一植物在不同地貌部位的土壤含水量具有差异性,小叶杨在迎风坡最高,樟子松、沙棘和乌柳在背风坡最高,而沙蒿在丘顶最高,但只有乌柳的土壤含水量在沙丘地貌部位间的差异明显(P<0.05)。不同植物在同一地貌部位的土壤含水量也具有差异性,迎风坡樟子松的土壤含水量最小,只有1.81%,而沙蒿的土壤含水量能达到3.48%。丘顶处乌柳的土壤含水量仅为1.82%,而沙蒿可达3.58%。背风坡处的土壤含水量相差不大,乌柳最大为3.41%。(3)土壤水分随着土层深度的变化模式不同,土壤含水量整体表现为10~20 cm处最高。不同植物的土壤水分的垂直分布具有差异性,小叶杨和樟子松下方的土壤含水量随着土层深度的增加而降低,沙棘和沙蒿表现为120 cm土层深度内无明显变化,而乌柳下方的土壤含水量随着土层深度的变化在各地貌部位不同,具体表现为迎风坡无明显变化、丘顶降低和背风坡增加的趋势。土壤水分在高寒半干旱沙地不同植被恢复措施下的分布除受到降水、土壤分布、物种类型、植物根系分布的影响之外,还与沙丘微地貌形态具有一定的相关性。     

黄土丘陵植被恢复过程中土壤种子库萌发数量特征及动态变化

采用野外定点采样与室内土壤种子萌发试验相结合的研究方法,选取黄土丘陵区典型草原带宁夏固原地区不同植被恢复年限(2,5,12,24,35,55,75 a)及当年农地(对照)的8个样地,研究该区土壤种子库萌发数量特征及动态变化.结果表明,8个不同植被恢复年限样地土壤中可萌发的种子的平均数量为3542.5粒/m2,可萌发种子以双子叶植物为主,约占萌发总数的90%.0～5 cm土层可萌发种子数量变化于166.7～9100.0粒/m2;5～10 cm土层变化于133.38～2120.02粒/m2.土壤中可萌发种子数量随着恢复年限的增加表现先增加后下降的趋势.土壤中可萌发的种子数量随时间的变化近似单峰型,双子叶植物峰值主要出现在第4～6周,而单子叶植物萌发高峰在5～6周.表明在环境,气候等条件适宜时,黄土丘陵区典型草原带可萌发的土壤中的种子可形成萌发高峰.     

内蒙古高原小叶锦鸡儿灌丛沙堆对气流结构与风蚀的影响

小叶锦鸡儿(Caragana microphylla)灌丛沙堆是内蒙古高原东南部农牧交错区的主要风沙堆积类型。通过对该区典型灌丛沙堆周围风沙气流的野外观测,结果表明,气流方向与强度和输沙率,随沙堆不同位置而发生变化。绕过沙堆两侧的气流和越过沙堆上部的气流在背风侧汇集,并在同等沙堆高度的范围内和1.5倍沙堆高度的水平范围内出现涡流。从灌丛沙堆迎风坡脚经南北两侧至背风坡脚以及背风侧5倍沙堆高度的水平距离间,风速依次出现逐渐增大—最大—逐渐减小—最小—回増至旷野风速的变化过程。在不同风向条件下,灌丛沙堆背风侧气流的风速廓线,并不完全遵循对数变化规律,沙堆南侧气流在0.3~0.6 m高度处出现变异。另外,沙堆周围输沙率在迎风侧和南北两侧与风速变化基本一致,但在背风侧因气流方向紊乱而出现变异。输沙率随高度增加,在沙堆迎风侧至两侧各部位呈有规律递减,但在背风侧无规律。     

高立式沙障不同叠加模式的阻沙量对比分析

为了解决尼龙阻沙网在沙埋情况下的防风阻沙,采用不同叠加模式的尼龙阻沙网进行防护。设置3种高立式沙障叠加模式方案,叠加位置分别位于迎风坡、阻沙网、背风坡,迎风坡与背风坡叠加的尼龙阻沙网与原有阻沙障距离和长度均相同,叠加的阻沙网高度为沙埋原有阻沙障的一半,且叠加的尼龙阻沙网需高出原有尼龙阻沙障。选择高1.2 m的沙埋阻沙障进行叠加,迎风与背风坡叠加的位置距原有阻沙障水平距离约45 cm。通过野外观测发现：① 不同叠加模式的高立式沙障阻沙量不同,即阻沙网＞迎风坡＞背风坡;② 3种不同叠加模式的积沙量都随着阻沙网的不断叠加而增加,且增加的阻沙量越来越大;③ 随着阻沙网的不断叠加,3种不同叠加模式的单位阻沙成本不断变化。迎风坡与阻沙网模式的单位阻沙成本不断降低,最后趋于平稳;背风坡模式有所不同,其单位阻沙成本先有所增加,然后再下降,最终趋于平稳。阻沙成本为：阻沙网<迎风坡<背风坡。     

PLA沙障对沙丘迎风坡土壤水分的影响

选取风季和雨季两个典型时期,对铺设不同规格PLA沙障沙丘迎风坡不同坡位0-60cm土层的土壤含水量进行测定,并以裸沙丘为对照,探究PLA沙障对沙丘迎风坡土壤水分的影响.结果表明:1m×1m和2m × 2m沙障在不同时期对沙丘迎风坡整体和坡位间土壤水分影响明显,而菱形沙障作用效果差;1m×1m、2m×2m沙障使风季形成迎风坡浅层(5-20cm)土壤含水量低于裸沙丘的水分特征,雨季形成迎风坡表层(0-10cm)土壤含水量优于裸沙丘的水分特征,从而影响了植物的入侵与定居方式;不同时期1m×1m和2m×2m沙障对迎风坡中部和下部土壤水分的影响均较上部明显,迎风坡中部和下部应为重点关注区域,而在上部应采取相伴措施弥补不足.     

毛乌素沙地樟子松人工林土壤微生物数量变化

对毛乌素沙地榆林沙区樟子松人工固沙林地土壤微生物进行测定和分析,结果表明:不同林龄樟子松林地细菌、放线菌和真菌数量差异显著,细菌和真菌数量随林龄增大不断增加;放线菌数量在流沙地(CK)、7～23a生林地这一时期内随着林龄增大显著增加,23a生林地达到最大值,31 a生林地出现明显回落.三大微生物均随土层深度加深而减少,在沙丘部位的分布表现为:丘间地＞背风坡＞迎风坡＞丘顶.在流沙地上栽植樟子松人工林后,土壤微生物数量增加,土壤肥力水平提高.     

小针茅荒漠草原生长季表层土壤有机碳月动态及影响因素

以内蒙古苏尼特右旗小针茅荒漠草原两种主要草地类型为研究对象,选择典型样地,通过实地调查测定其5~9月生长季地上、地下生物量、土壤有机碳及土壤含水量,分析了小针茅荒漠草原生长季土壤有机碳的月动态,探讨了地下生物量、气温、降水及土壤含水量对土壤有机碳的影响。研究结果表明:1)小针茅荒漠草原两种草地型生长季土壤有机碳月变化趋势不同。小针茅+无芒隐子草草地生长季土壤有机碳月变化表现为从5月份开始逐渐降低,到9月份又略有增加,狭叶锦鸡儿-小针茅+无芒隐子草草地土壤有机碳月变化表现为5~7月增加,8月份降低,9月份又增加的趋势。2)小针茅荒漠草原5~9月生长季各月土壤有机碳含量差异不显著,0-10cm土层深度土壤有机碳含量低于10-20cm和20-30cm土层深度土壤有机碳含量。3)小针茅荒漠草原5~9月土壤有机碳含量与月降水量之间呈正相关关系,但不显著。而6~9月土壤有机碳含量与月降水量之间呈显著正相关关系。4)小针茅荒漠草原土壤有机碳受表层地下生物量影响较大,土壤有机碳含量与0~10cm土层地下生物量呈显著正相关。5)小针茅荒漠草原生长季土壤有机碳含量与月均温之间没有显著相关性,与0~10cm土壤含水量呈极显著正相关。     

陕北毛乌素沙地土壤水分时空变异规律研究

对陕北毛乌素沙地流动、固定、半固定沙丘的土壤水分进行的长期动态观测结果表明,含水量排序为流动沙丘(8.47%)＞半固定沙丘(8.40%)＞固定沙丘(8.39%).沙地含水量随土壤深度的变化存在着分布上的差异,随着深度的增加呈现先增加再减少的趋势,在0～60 cm土层,流动沙丘、半固定沙丘和固定沙丘土壤水分含量分别为8.08%、8.00%和8.03%,差异不显著;在60～200 cm土层,流动沙丘、半固定沙丘和固定沙丘土壤水分含量分别为8.65%、8.57%和8.53%,差异显著(P>0.05),其中60～140 cm层,流动沙丘、半固定沙丘和固定沙丘土壤水分含量分别为8.76%、8.62%和8.54%,差异极显著(P>0.01).固定沙丘、半固定沙丘大部分背风面的土壤含水量高于迎风面的含水量,但在流动沙丘上迎风面的土壤含水量却明显比背风面的高.在沙丘的不同部位含水量也存在差异,土壤含水量坡顶部＜坡中部＜坡底部,在沙丘下部的丘间土壤含水量明显高于丘顶部.另外,沙地水分还受季节变化的影响,具有明显的季节变异性.     

Dermestid beetles in ‘evolution Canyon’, lower Nahal Oren, Mt. Carmel, including new records for Israel

Fifteen species of dermestid beetles were recorded at ‘Evolution Canyon’ (EC), Lower Nahal Oren, Mt. Carmel, Israel. They represent ~35% of known Israeli dermestid species. The following three species were recorded for the first time in Israel:Trogoderma svriaca Dalla Torre, 1911;Ctesias svriaca Ganglbauer, 1904; andAnthrenus (s.str.) jordaniens Pic, 1934. Adults of 13 species were collected on the more solar radiated, warmer and climatically more fluctuating south-facing slope (SFS); ten species were collected on the opposite, north-facing slope (NFS), which was cooler and climatically more stable. The abundance of adult dermestid beetles was 1.9 times higher on the SFS than on the NFS (86 and 47, respectively). Species richness and abundance distribution at EC (three collecting stations on each slope and one at the valley bottom) were significantly negatively correlated with the plant cover that consisted of trees and bushes (Spearmanr _s ,P=0.007 and 0.039, respectively) and perennials (Spearmanr _s ,P=0.039 and 0.077, respectively), indicating that non-woody plants were preferred by adult dermestid beetles.     

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.     

Epidemiology of Toxigenic Fungi and their Associated Mycotoxins for Some Mediterranean Crops

Recent data on the epidemiology of the common mycotoxigenic species of Fusarium, Alternaria, Aspergillus and Penicillium in infected or colonized plants, and in stored or processed plant products from the Mediterranean area are reviewed. Emphasis is placed on the toxigenicity of the causal fungal species and the natural occurrence of well known mycotoxins (aflatoxins, ochratoxins, fumonisins, trichothecenes, zearalenone, patulin, Alternaria-toxins and moniliformin), as well as some more recently described compounds (fusaproliferin, beauvericin) whose toxigenic potential is not yet well understood. Several Fusarium species reported from throughout the Mediterranean area are responsible of the formation of mycotoxins in infected plants and in plant products, including: Fusarium graminearum, F. culmorum, F. cerealis, F. avenaceum, F. sporotrichioides and F. poae, which produce deoxynivalenol, nivalenol, fusarenone, zearalenone, moniliformin, and T-2 toxin derivatives in wheat and other small grains affected by head blight or scab, and in maize affected by red ear rot. Moreover, strains of F. verticillioides, F. proliferatum, and F. subglutinans, that form fumonisins, beauvericin, fusaproliferin, and moniliformin, are commonly associated with maize affected by ear rot. Fumonisins, were also associated with Fusarium crown and root rot of asparagus and Fusarium endosepsis of figs, caused primarily by F. proliferatum. Toxigenic A. alternata strains and associated tenuazonic acid and alternariols were commonly found in black mould of tomato, black rot of olive and citrus, black point of small cereals, and black mould of several vegetables. Toxigenic strains of A. carbonarius and ochratoxin A were often found associated with black rot of grapes, whereas toxigenic strains of A. flavus and/or P. verrucosum, forming aflatoxins and ochratoxin A, respectively, were found in moulded plant products from small cereals, peanuts, figs, pea, oilseed rape, sunflower seeds, sesame seeds, pistachios, and almonds. Finally, toxigenic strains of P. expansum and patulin were frequently found in apple, pear and other fresh fruits affected by blue mould rot, as well as in derived juices and jams.     

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     

A survey of the genera of<Emphasis Type="Italic">Microgaster</Emphasis> latreille and<Emphasis Type="Italic">Hygroplitis</Emphasis> thomson (Hymenoptera: Braconidae: Microgastrinae) from China

The genera ofMicrogaster Latreille 1804 andHygroplitis Thomson 1895 from China are presented systematically in this paper. Thirty-two species ofMicrogaster and three species ofHygroplitis are known in China. Diagnosis, character variation, distribution and host of each species among the two genera are presented, including its host and distribution. Keys to the species ofMicrogaster andHygroplitis are given. http://www.phytoparasitica.org posting Dec. 19, 2006.     

Plant Viruses Transmitted by Whiteflies

One-hundred and fourteen virus species are transmitted by whiteflies (family Aleyrodidae). Bemisia tabaci transmits 111 of these species while Trialeurodes vaporariorum and T. abutilonia transmit three species each. B. tabaci and T. vaporariorum are present in the European–Mediterranean region, though the former is restricted in its distribution. Of the whitefly-transmitted virus species, 90% belong to the Begomovirus genus, 6% to the Crinivirus genus and the remaining 4% are in the Closterovirus, Ipomovirus or Carlavirus genera. Other named, whitefly-transmitted viruses that have not yet been ranked as species are also documented. The names, abbreviations and synonyms of the whitefly-transmitted viruses are presented in tabulated form together with details of their whitefly vectors, natural hosts and distribution. Entries are also annotated with references. Whitefly-transmitted viruses affecting plants in the European–Mediterranean region have been highlighted in the text.     

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.     

Broad bean mottle virus in Morocco; curculionid vectors,and natural occurrence in food legumes other than faba bean (Vicia faba)

Broad bean mottle virus (BBMV) was transmitted from infected to healthy faba-bean plants by the curculionid weevilsApion radiolus Kirby,Hypera variabilis Herbst,Pachytychius strumarius Gyll,Smicronyx cyaneus Gyll, andSitona lineatus L. The latter appeared to be an efficient vector: acquisition and inoculation occurred at the first bite, the rate of transmission was c. 41%, and virus retention lasted for at least seven days.S. lineatus transmitted the virus from faba bean to lentil and pea, but not to the three genotypes of chickpea tested. This is the first report on the generaHypera, Pachytychius, andSmicronyx as virus vectors, and onA. radiolus, H. variabilis, P. strumarius, andS. cyaneus as vectors of BBMV.Out of 351 samples of food legumes with symptoms suggestive of virus infection, 16, 11, 19, and 17% of the samples of chickpea, lentil, pea, and common bean, respectively, were found infected when tested for BBMV in DAS-ELISA. This is the first report on the natural occurrence of BBMV in chickpea, lentil, pea, and common bean. The virus should be regarded as a food-legume virus rather than a faba-bean virus solely, and is considered an actual threat to food legume improvement programmes.