Prioritizing woody species for the rehabilitation of arid lands in western Iran based on soil properties and carbon sequestration

Plants are an important component in many natural ecosystems. They influence soil properties, especially in arid ecosystems. The selection of plant species based on their adaptations to site conditions is essential for rehabilitation of degraded sites and other construction sites such as check-dams. Other factors to be considered in species selection include their effects on soil properties and their abilities to meet other management objectives. The purpose of this study was to assess the effects of native (Populus euphratica Oliv. and Tamarix ramosissima Ledeb.) and introduced (Eucalyptus camaldulensis Dehnh. and Prosopis juliflora (Swartz) DC.) woody species on soil properties and carbon sequestration (CS) in an arid region of Iran. Soil sampling was collected at three soil depths (0-10, 10-20 and 20-30 cm) at the sites located under each woody species canopy and in an open area in 2017. Soil physical-chemical property was analyzed in the laboratory. The presence of a woody species changed soil characteristics and soil CS, compared with the open area. For example, the presence of a woody species caused a decrease in soil bulk density, of which the lowest value was observed under E. camaldulensis (1.38 g/cm³) compared with the open area (1.59 g/cm³). Also, all woody species significantly increased the contents of soil organic matter and total nitrogen, and introduced species had more significant effect than native species. The results showed that CS significantly increased under the canopy of all woody species in a decreasing order of P. euphratica (9.08 t/hm²)>E. camaldulensis (8.37 t/hm²)>P. juliflora (5.20 t/hm²)>T. ramosissima (2.93 t/hm²)>open area (1.33 t/hm²), thus demonstrating the positive effect of a woody species on CS. Although the plantation of non-native species had some positive effects on soil properties, we recommend increasing species diversity in plantations of native and introduced woody species to provide more diversity for the increased ecosystem services, resilience, health and long-term productivity.     

Rehabilitation of degraded areas in northeastern Patagonia,Argentina: Effects of environmental conditions and plant functional traits on performance of native woody species

Degradation processes affect a vast area of arid and semi-arid lands around the world and damage the environment and people′s health. Degradation processes are driven by human productive activities that cause direct and indirect effects on natural resources, such as species extinction at regional scale, reduction and elimination of vegetation cover, soil erosion, etc. In this context, ecological rehabilitation is an important tool to recover key aspects of the degraded ecosystem. Rehabilitation trials rely on the use of native plant species with characteristics that allow them to obtain high survival and growth rates. The aim of this work was to assess the survival and growth of native woody species in degraded areas of northeastern Patagonia and relate them to plant functional traits and environmental variables. We observed high early and late survival rates, and growth rates in Prosopis flexuosa DC. var. depressa F.A. Roig and Schinus johnstonii F.A. Barkley, and low values in Condalia microphylla Cav. and Geoffroea decorticans (Gillies ex Hook. & Arn.) Burkart. Early survival rates were positively associated with specific leaf area (SLA) and precipitation, but negatively associated with wood density, the maximum mean temperature of the warmest month and the minimum mean temperature of the coldest month. Late survival rates were positively associated with SLA and soil organic matter, but negatively associated with plant height and precipitation. The temperature had a positive effect on late survival rates once the plants overcame the critical period of the first summer after they were transplanted to the field. Prosopis flexuosa and S. johnstonii were the most successful species in our study. This could be due to their functional traits that allow these species to acclimatize to the local environment. Further research should focus on C. microphylla and G. decorticans to determine how they relate to productive conditions, acclimation to environmental stress, auto-ecology and potential use in ecological rehabilitation trials.     

甜瓜种子携带的链格孢菌种类鉴定及其致病性研究

 采用洗涤检验法和马铃薯葡萄糖琼脂培养基法,从甜瓜种子上分离得到14个链格孢菌分离物。通过菌落形态、产孢表型、分生孢子以及分生孢子梗等形态学观察,结合分析ITS-rDNA和histone 3基因序列,对链格孢菌分离物的种类进行鉴定;甜瓜种子携带的链格孢菌种类分别为细极链格孢(Alternaria tenuissima)、交链格孢(A. alternata)和倒果链格孢(A. obovoidea)。还研究了这些链格孢菌分离物对甜瓜离体叶片的致病性及其对种子发芽的影响;结果表明,除A. obovoidea外,另外两种链格孢菌均对甜瓜离体叶片具有致病性;A. tenuissima和A. alternata的孢子悬浮液对甜瓜种子发芽均有一定的抑制作用。这是国内首次围绕甜瓜种子传带链格孢菌的种类及其致病性开展详细的研究。     

一株拮抗水稻白叶枯病菌的淡紫灰链霉菌的筛选鉴定及其生防效果研究

 为发现绿色安全的水稻白叶枯病天然生物防治微生物,本研究从植物根际土壤中分离获得165株放线菌。利用共培养法和牛津杯法,筛选获得了5株拮抗水稻白叶枯病菌(Xanthomonas oryzae pv. oryzae, Xoo)的放线菌,其中拮抗能力最强的是Sl-10菌株,发酵液抑菌圈直径为62.1 mm ± 1.5 mm。根据形态特征、生理生化实验、16S rDNA序列和系统发育分析,鉴定Sl-10菌株为淡紫灰链霉菌(Streptomyces lavendulae)。Sl-10菌株发酵液对大豆斑点病菌(Pseudomonas syringae pv. glycinea)、烟草野火病菌(P. syringae pv. tabaci)、油菜黑腐病菌(X. campestris pv. campestris)、大豆斑疹病菌(X. axonopodis pv. glycines)、水稻条斑病菌(X. oryzae pv. oryzicola)、烟草青枯病菌(Ralstonia solanacearum)和番茄叶斑病菌(P. syringae pv. tomato)7种植物病原细菌均有拮抗作用。Sl-10菌株发酵液具有较好的耐光、耐酸碱和热稳定性。SDS-PAGE电泳结果显示,Sl-10菌株可抑制Xoo的蛋白质合成。4个品种水稻(甬优15、湘两优900、嘉丰2号和甬优1540)喷施Sl-10菌株发酵液,水稻白叶枯病的病斑抑制率达到82.27%~91.78%。研究结果显示,淡紫灰链霉菌Sl-10菌株具有较好的水稻白叶枯病生物防治潜能。     

云南、广西三七黑斑病病原链格孢菌的鉴定

正黑斑病是三七栽培生产中常见的一大病害,叶片受害产生近圆形或不规则水浸状病斑,常导致成株落叶、幼苗生长点及茎秆顶端腐烂枯死。其病原一般认为是链格孢属真菌人参链格Alternaria panax Whetzel~([1,2]),也有相关研究证明黑斑病病原为细链格孢Alternaria tenuis Nees~([3]),后定名为链格孢Alternaria alternata Keissl~([4])。本研究利用ITS序列和histone 3部分编码序列的PCR鉴定,结合形态学鉴定,分析三七主产区黑斑病菌的组成和分布情况及几种病原菌的致病力差异,以期为三七黑斑病防治提供理论依据。     

RXLR类效应分子PITG_21645.2的基因序列分析及功能验证

 马铃薯晚疫病黑龙江菌株效应分子PITG_21645.2在本氏烟(Nicotiana benthamiana)上可以抑制由INF1引起的过敏性细胞坏死(Hypersensitive response, HR)。为验证其为致病疫霉致病的重要效应分子,克隆了10个致病疫霉菌株以及3个同属卵菌菌株中的PITG_21645.2同源基因,它们在氨基酸序列上相似度为93%~100%。与INF1共表达的结果显示,仅有PITG_21645.2^MP903丧失了抑制HR的功能。其中PITG_21645.2^MP903的第31位氨基酸存在特异性,编码丝氨酸,其余同源基因在该位点均编码天冬酰胺。PITG_21645.2^MP903回复突变体(S31N)能够恢复该基因抑制INF1引起HR的功能,说明第31位氨基酸是影响抑制功能的关键位点。另外,PITG_21645.2还能抑制BAX、大豆疫霉PsojNIP和效应分子Avh238在本氏烟上激发的HR,而PITG_21645.2^MP903都丧失抑制功能。本氏烟上表达PITG_21645.2能够促进致病疫霉在寄主上的定殖,从而提示PITG_21645.2在致病疫霉的侵染中发挥致病性功能。     

Exploring tree diversity and stand structure of savanna woodlands in southeastern Sudan

Savanna woodlands in Sudan host great biodiversity, provide a plethora of ecosystem goods and services to local communities, and sustain numerous ecological functions. Although the importance of the Acacia trees in these areas is well known, up-to-date information about these woodlands' diversity is limited and changes in their woody vegetation composition, density, diversity and relative frequency are not monitored over time. This study explored tree diversity and stand stage structure in Nuara Reserved Forest, a typical savanna woodland ecosystem in southeastern Sudan. A total of 638 circular sample plots (1000 m² for each) were established using a systematic sampling grid method. The distance between plots was 200 m. In each plot, all living trees with diameter at breast height (DBH) ≥5.00 cm were identified and counted, and their DBH values were recorded. From these data, tree composition, diversity, density and stage structure were assessed. There were 12,259 individual trees representing four species (Acacia seyal, Balanites aegyptiaca, Acacia Senegal and Acacia mellifera) that belong to two families. The dominant species was Acacia seyal. Average tree density was 191 trees/hm² and the Shannon-Weiner index for trees diversity was 0.204. Overall, young trees comprised 86.30% of the forest. The state of tree richness and density in the study area was low compared to other similar environments in the region and around the world. We recommended adoption of a proper management system that includes monitoring of woody vegetation diversity in this forest, and management actions to enhance tree diversity and sustain ecosystem services to local communities. In addition to care for the dominant Acacia seyal stands, more attention and conservation should be devoted to reestablishing Acacia senegal and Acacia mellifera trees because of their high ecological and economic values for local communities.     

小麦条锈菌转主寄主小檗(Berberis germanensis)的人工接种鉴定

正条形柄锈菌小麦专化型(Puccinia striiformis f.sp.tritici),简称小麦条锈菌,是引起小麦条锈病(wheat stripe rust or yellow rust)的病原菌。近年通过人工室内接种证实小檗(Berberis spp.)是小麦条锈菌的转主寄主~([1]),由此揭示了小麦条锈菌是具有性、锈、夏、冬和担孢子5种孢子类型的全孢     

哈萨克斯坦阿尔泰山树木径向生长及其对气候要素的响应

针对哈萨克斯坦阿尔泰山南坡西伯利亚云杉（Picea obovata）和西伯利亚落叶松（Larix sibirica）开展树轮研究，建立树轮年表，计算年平均树轮宽度值和年平均断面积生长量（BAI），并分析在1988年发生升温突变前后，这2个树种树轮宽度指数变化趋势，及其树木径向生长对气候因子的响应。结果表明：在升温突变前后，2个树种树轮宽度指数变化趋势一致。但是，在升温突变后，其变化趋势均由不显著增加转为显著下降。即树木径向生长减缓；升温突变后，2个树种树木径向生长对降水的响应有所减弱，而对气温的响应有所增强，并且发生了树轮指数和气候因子间相关性“正负转换”的情况。     

Modelling the biological invasion of Prosopis juliflora using geostatistical-based bioclimatic variables under climate change in arid zones of southwestern Iran

Invasive species have been the focus of ecologists due to their undesired impacts on the environment.The extent and rapid increase in invasive plant species is recognized as a natural cause of global-biodiversity loss and degrading ecosystem services.Biological invasions can affect ecosystems across a wide spectrum of bioclimatic conditions.Understanding the impact of climate change on species invasion is crucial for sustainable biodiversity conservation.In this study,the possibility of mapping the distribution of invasive Prosopis juliflora(Swartz)DC.was shown using present background data in Khuzestan Province,Iran.After removing the spatial bias of background data by creating weighted sampling bias grids for the occurrence dataset,we applied six modelling algorithms(generalized additive model(GAM),classification tree analysis(CTA),random forest(RF),multivariate adaptive regression splines(MARS),maximum entropy(Max Ent)and ensemble model)to predict invasion distribution of the species under current and future climate conditions for both optimistic(RCP2.6)and pessimistic(RCP8.5)scenarios for the years 2050 and 2070,respectively.Predictor variables including weighted mean of CHELSA(climatologies at high resolution for the Earth’s land surface areas)-bioclimatic variables and geostatistical-based bioclimatic variables(1979–2020),physiographic variables extracted from shuttle radar topography mission(SRTM)and some human factors were used in modelling process.To avoid causing a biased selection of predictors or model coefficients,we resolved the spatial autocorrelation of presence points and multi-collinearity of the predictors.As in a conventional receiver operating characteristic(ROC),the area under curve(AUC)is calculated using presence and absence observations to measure the probability and the two error components are weighted equally.All models were evaluated using partial ROC at different thresholds and other statistical indices derived from confusion matrix.Sensitivity analysis showed that mean diurnal range(Bio2)and annual precipitation(Bio12)explained more than 50% of the changes in the invasion distribution and played a pivotal role in mapping habitat suitability of P.juliflora.At all thresholds,the ensemble model showed a significant difference in comparison with single model.However,Max Ent and RF outperformed the others models.Under climate change scenarios,it is predicted that suitable areas for this invasive species will increase in Khuzestan Province,and increasing climatically suitable areas for the species in future will facilitate its future distribution.These findings can support the conservation planning and management efforts in ecological engineering and be used in formulating preventive measures.     

5种盐生植物生物炭产率及其理化性质

为了解不同盐生植物生物炭特性的种间差异,特选用盐地碱蓬(Suaeda salsa)、盐角草(Salicornia europaea)、高碱蓬(Suaeda altissima)、野榆钱菠菜(Atriplex aucheri)、盐穗木(Halostachys caspica) 5种黎科盐生植物为研究对象,于500℃温度下炭化制备生物炭,通过理化性质分析,并结合主成分分析来探讨盐生植物原材料对生物炭特性差异的影响。结果表明:生物炭的产率受盐生植物原材料灰分含量影响。此外,生物炭灰分、养分及阳离子含量受盐生植物原材料物质成分的影响。炭化能显著增加生物质灰分含量,5种生物炭灰分含量与原材料相比增加了67. 22%～169. 24%,同时伴随着灰分增加,水溶性Na~+、K~+等低价离子富集,pH、电导率(EC)增大,碱性增强。本研究为盐生植物生物炭在改良酸性土壤、炭化原材料选择等方面提供基础数据及理论参考。     

西瓜噬酸菌Aac-5AAA ATPases基因moxR和ruvB功能研究

AAA ATPases(ATPase associated with diverse cellular activities)是一种与细胞活性相关的酶,广泛存在于所有生物中,同时具有蛋白酶和分子伴侣活性。为了研究AAA ATPases相关基因缺失对西瓜噬酸菌(Acidovorax citrulli)的影响,本研究通过同源重组双交换的方法构建西瓜噬酸菌moxR基因以及ruv B基因全缺失突变菌株及互补菌株,测定了突变菌株的致病性、烟草过敏反应、运动性、生长能力、生物膜形成等;并利用实时荧光定量PCR方法测定了AAA ATPases与Ⅲ型分泌系统相关基因(hrc N和hrp E)、毒性蛋白相关基因(trb C和vir B)、鞭毛相关基因(fliR和fli M)、菌毛相关基因(pin C-1和pin C-2)以及AAA ATPases亚家族Ruv B相关基因(ruv A和ruv C)的关系。结果表明,moxR基因以及ruv B基因全缺失突变菌株的致病力降低、运动性减弱、生长能力下降、生物膜形成能力增强、烟草过敏性反应减弱、突变菌株中重要的致病基因hrc N和hrp E表达量显著下调,表明AAA ATPases相关基因moxR、ruv B在西瓜噬酸菌的致病力上发挥重要作用。     

樟子松固沙林土壤理化特性对林分密度的响应

为了研究樟子松人工固沙林林分密度对土壤理化特性的影响,在章古台地区选取林分密度分别为625（P₁）、775（P₂）、1 025（P₃）、1 175（P₄）株·hm^-2和1 250（P₅）株·hm^-2的樟子松中龄林（林龄为23~27 a）为研究对象,对0~100 cm深度的樟子松林地土壤按0~10、10~20、20~40、40~60、60~80、80~100 cm进行分层,分析其理化特性。结果表明：0~10 cm土层全氮和20~40 cm土层土壤容重随密度增加呈上升趋势,P₅显著高于P₁（P < 0.05）;0~80 cm土层全钾和0~60 cm土层pH随密度增加先升高后降低,P₃最高,且P₃样地全钾在10~60 cm土层显著高于P₁（P < 0.05）;pH在0~40 cm土层显著高于其他样地（P < 0.05）;0~10 cm土层全磷随密度增加而减小,P₁显著高于P₃~P₅（P < 0.05）;P₄或P₅样地有效钾在0~40 cm土层显著高于P₁、P₂样地（P < 0.05）,在40~100 cm土层显著高于P₃样地（P < 0.05）;P₂~P₄样地的土壤孔隙度在40~100 cm土层低于P₁和P₅样地。综合考虑林分密度对樟子松中龄林土壤理化特性的影响,章古台地区樟子松林的合理林分密度为1 025~1 175株·hm^-2,可采取间伐等营林管理措施调节林分密度,确保樟子松固沙林生长具有良好的土壤条件。     

江原钝绥螨对三种橘园害虫的捕食能力

江原钝绥螨Amblyseius eharaiAmitai et Swirski广泛分布于我国各地的柑橘产区,是我国柑橘园的捕食螨优势种之一。由于滥用化学农药,大量叶螨天敌受到危害,叶螨的抗药性却逐年增强。利用天敌生物防治叶螨成为近年来柑橘害螨绿色防控的重要措施。本文主要研究了江原钝绥螨对柑橘全爪螨Panonychus citri McGregor、柑橘粉虱Dialeurodes citri Ashm和黄胸蓟马Thrips hawaiiensis Morgan等3种橘园害虫的捕食能力及选择性。结果表明,江原钝绥螨在28 ℃时,24 h内可以捕食柑橘全爪螨幼若螨约18.5头、柑橘粉虱1龄若虫约13.9头、黄胸蓟马1龄若虫约10.4头,且对3种猎物的功能反应均为HollingⅡ型。江原钝绥螨在28 ℃时具有最高的捕食效能,温度过高或过低,均会减弱江原钝绥螨对猎物的捕食能力。在柑橘全爪螨、柑橘粉虱和黄胸蓟马这3种猎物同时存在的情况下,江原钝绥螨会优先捕食柑橘全爪螨,占被捕食的比例为82.14%。江原钝绥螨雌成螨对柑橘全爪螨各螨态的取食具有选择性,其幼、若螨是江原钝绥螨的嗜好虫态。本研究表明江原钝绥螨对柑橘全爪螨、柑橘粉虱、黄胸蓟马均有较强的控制潜力,为江原钝绥螨的田间应用提供了理论依据。     

进境油菜籽中十字花科黑斑病菌的检测

 利用MT选择性培养基从加拿大进境油菜籽样品中分离到2株细菌分离物2305-1和5309-1,对分离物进行致病性测定、LOPAT测试、Biolog测试、hrpZ和cfl基因序列分析,以及多位点序列分析。结果表明:2株分离物人工接种油菜、花椰菜和番茄幼苗都能引起典型黑斑症状;LOPAT测试和Biolog测试结果与丁香假单胞菌(Pseudomonas syringae)的各项生理指标一致;hrpZ基因序列与十字花科黑斑病菌(P. syringae pv. maculicola)和番茄细菌性叶斑病菌(P. syringae pv.tomato)的序列相似性均为99.18%～100%;cfl基因序列分析表明分离物2305-1和5309-1基因组中存在冠毒素合成基因;选择gyrB、ropD、gltA、 gap1、 acnB和pgi 6个看家基因进行多位点序列分析,系统发育树显示分离物2305-1和5309-1均与P. syringae pv. ma-culicola聚在一起。根据试验结果将分离物2305-1和5309-1鉴定为十字花科黑斑病菌P. syringae pv. maculicola。     

Changes in rainfall partitioning caused by the replacement of native dry forests of Lithraea molleoides by exotic plantations of Pinus elliottii in the dry Chaco mountain forests,central Argentina

The replacement of native dry forests by commercial (exotic) tree plantations could generate changes in rainfall partitioning, which further affects the water cycle. In this study, we determined (i) the rainfall partitioning into interception, throughfall and stemflow, (ii) the role of rainfall event size on rainfall partitioning, (iii) the pH of water channelized as throughfall and stemflow, and (iv) the runoff in Lithraea molleoides (a native species) and Pinus elliottii (an exotic species) stands in the dry Chaco mountain forests, central Argentina. On average, interception, throughfall and stemflow accounted for 19.3%, 79.5% and 1.2% of the gross rainfall in L. molleoides stand, and 32.6%, 66.7% and 0.7% of the gross rainfall in P. elliottii stand, respectively. Amounts of interception, throughfall and stemflow presented positive linear relationships with the increment of rainfall event size for both tree species (P<0.01 in all cases). Percentages of interception, throughfall and stemflow were all related to the increment of rainfall event size, showing different patterns. With increasing rainfall event size, interception exponentially decreased, throughfall asymptotically increased and stemflow linearly increased. Both P. elliottii and L. molleoides stands presented significant differences in the pH values of water channelized as throughfall (6.3 vs. 6.7, respectively; P<0.01) and stemflow (4.5 vs. 5.8, respectively; P<0.01). Runoff occupied only 0.3% of the gross rainfall in P. elliottii stand and was zero in L. molleoides stand. Our results showed that the native species L. molleoides presented 13.6% more water reaching the topsoil (i.e., net rainfall; net rainfall=gross rainfall-interception-runoff) than the exotic species P. elliottii. This study improves our understanding of the effects of native vegetation replacement on the local water balance in the dry forest ecosystems.     

检疫性疫霉DNA条形码筛选

 疫霉是世界关注的一类植物病原真菌。以疫霉属80个种122个菌株为研究材料,以ITS、CO1、EF-1α和β-tubulin 4个基因片段为候选DNA条形码,分析表明ITS、CO1基因的PCR扩增和测序成功率最高,分别为100%和96.7%;ITS、CO1和β-tubulin存在明显的条码间隔,但种间、种内距离频率分布存在较小重叠;种间、种内遗传距离Wilcoxon秩和检验结果认为各基因对种内遗传距离的效力相等,对种间遗传距离的区分能力为ITS>CO1>β-tubulin。CO1基因和ITS片段可同时作为11种检疫性疫霉的首选DNA条形码,β-tubulin基因可作为辅助DNA条形码。     

Responses in gross primary production of Stipa krylovii and Allium polyrhizum to a temporal rainfall in a temperate grassland of Inner Mongolia,China

In the arid and semi-arid areas of China, rainfall and drought affect the growth and photosynthetic activities of plants. Gross primary productivity (GPP) is one of the most important indices that measure the photosynthetic ability of plants. This paper focused on the GPP of two representative grassland species (Stipa krylovii Roshev. and Allium polyrhizum Turcz. ex Regel) to demonstrate the effect of a temporal rainfall on the two species. Our research was conducted in a temperate grassland in New Barag Right Banner, Hulun Buir City, Inner Mongolia Autonomous Region of China, in a dry year 2015. We measured net ecosystem productivity (NEP) and ecosystem respiration flux (ER) using a transparent chamber system and monitored the photosynthetically active radiation (PAR), air and soil temperature and humidity simultaneously. Based on the measured values of NEP and ER, we calculated the GPP of the two species before and after the rainfall. The saturated GPP per aboveground biomass (GPP_AGB) of A. polyrhizum remarkably increased from 0.033 (±0.018) to 0.185 (±0.055) μmol CO₂/(gdw?s) by 5.6-fold and that of S. krylovii decreased from 0.068 (±0.021) to 0.034 (±0.011) μmol CO₂/(gdw?s) by 0.5-fold on the 1^st and 2^nd d after a 9.1 mm rainfall event compared to the values before the rainfall at low temperatures below 35°C. However, on the 1^st and 2^nd d after the rainfall, both of the saturated GPP_AGB values of S. krylovii and A. polyrhizum were significantly lower at high temperatures above 35°C (0.018 (±0.007) and 0.110 (±0.061) μmol CO₂/(gdw?s), respectively) than at low temperatures below 35°C (0.034 (±0.011) and 0.185 (±0.055) μmol CO₂/(gdw?s), respectively). The results showed that the GPP responses to the temporal rainfall differed between S. krylovii and A. polyrhizum and strongly negative influenced by temperature. The temporal rainfall seems to be more effective on the GPP of A. polyrhizum than S. krylovii. These differences might be related to the different physiological and structural features, the coexistence of the species and their species-specific survival strategies.     

青海东部小麦条锈菌转主寄主小檗资源调查与鉴定

 青海省是中国小麦条锈病的重要流行区。研究证实小檗是小麦条锈菌的转主寄主。然而,关于青海省分布的小檗能否作为小麦条锈菌转主寄主鲜有报道。本研究对青海东部的小檗资源进行调查,并对该地区小檗能否作为小麦条锈菌转主寄主进行了室内人工鉴定。结果表明:有10种小檗在青海东部常见且分布广泛,其中匙叶小檗、置疑小檗、松潘小檗、甘肃小檗和近似小檗,是小麦条锈菌的转主寄主小檗的新种类。本研究对进一步研究青海东部条锈菌有性生殖与毒性变异和小麦条锈病的流行奠定了基础。     

Grazing and heat stress protection of native grass by a sand-fixing shrub in the arid lands of northern China

Shrub species are used in restoration projects on dryland for their facilitation effects, which include environmental improvements and protection from herbivore feeding. Facilitation effects on forage grasses are potentially important in improving grazing capacity on rangelands. However, the morphology-dependent performance of benefactor plants in facilitating forage species growth and supplementation under moderate grazing intensity remains unclear. Here, our main purpose was to measure facilitation performance in terms of the survival of a native forage grass, Agropyron cristatum (L.) Gaertn. (Gramineae)., in accordance with the growth conditions of a sand-fixing benefactor shrub, Caragana microphylla Lam., in the Hulun Buir Grassland, northern China. Six study sites with patches of A. cristatum and C. microphylla were established at the foot of fixed sand dunes. At each site, five quadrats were set in places where C. microphylla coverage was 100% and A. cristatum grew among the shrubs (shrub quadrats), and another five were set where A. cristatum grew alone without C. microphylla (grass quadrats). We measured the morphological traits of C. microphylla and A. cristatum in all 60 quadrats, along with the soil water content and soil temperature. The data were compared between the shrub and grass quadrats by generalized linear mixed-effect models to assess the shrub's facilitation effects. We also used such models to elucidate the relationship between the average height of C. microphylla and the morphological traits of A. cristatum in the shrub quadrats. The maximum height, average grazed height, and the number of seed heads of A. cristatum were greater in the shrub quadrats than in the grass quadrats. The soil surface temperature was lower in the shrub quadrats. The maximum height and seed head number of A. cristatum were positively associated with the average height of C. microphylla. These results suggest that the grazing impact and heat stress were smaller in shrub quadrats than in grass quadrats, and that the degree of this protective effect depended on the shrub height. The shrub canopy seemed to reduce the increase in soil temperature and keep the grass vigorous. Livestock likely avoided grazing grasses in the C. microphylla patches because of the shrub's spiny leaves; only the upper parts of the grass stems (including the seed heads) protruding from the shrub canopy were grazed. The sand-fixing shrub thus moderates the grazing impact and soil temperature, and contributes to vegetation restoration and grazing system sustainability.