Runoff- and erosion-reducing effects of vegetation on the loess hillslopes of China under concentrated flow     

《国际水土保持研究(英文)》2022,10(4):662-676

Evaluating the effects of revegetation on runoff and erosion reduction is essential for studying soil and water conservation on the Loess Plateau after implementation of China's Grain for Green Project. However, quantifying the influence of revegetation on the erosion caused by concentrated runoff in extreme rainstorms is still challenging. To evaluate this influence, scouring-erosion experiments were implemented in situ on the vegetated hillslope plots (GR) and bare hillslope plots (CK). The runoff-reducing effects of grass (GRR) averaged 31%, 20% and 8%, and the erosion-reducing effects of grass (GER) averaged 93%, 95% and 93% on the 5°-plots, 10°-plots and 18°-plots, respectively. The ratios of GRR to GER were 0.09–0.33, implying that the ability of vegetation to reduce erosion was greater than its ability to reduce runoff. The GRR and GER obviously decreased as the inflow rate increased, and the GRR decreased as the hillslope gradient increased, but there were no obvious differences in the GER between hillslope gradients. Vegetation could decrease the ability of the concentrated flow to carry and transport sediment and increase the energy consumption of the concentrated flow in response to hydraulic resistance. Vegetation also significantly reduced the degree of rill development. The degree of rill dissection on the GR (0.054–0.087 m² m^?2) was lower than that on the CK (0.061–0.184 m² m^?2). Our findings provide an essential reference for ecological environment and vegetation restoration on loess hillslopes.  相似文献   

Distribution of major clonal lineages EU_13_A2, EU_2_A1, and EU_23_A1 of Phytophthora infestans associated with potato late blight across crop seasons and regions in Algeria     

Lyes Beninal  Zouaoui Bouznad  Roselyne Corbière  Sihem Belkhiter  Romain Mabon  Abdelmoumen Taoutaou  Abdelaziz Keddad  Eve Runno-Paurson  Didier Andrivon 《Plant pathology》2022,71(2):458-469

Potato is one of the most important agricultural crops in Algeria and worldwide. Each year, potato late blight, caused by Phytophthora infestans, is responsible for significant damage that leads to large production losses, and is thus a direct threat to food security in Algeria. In this study, 131 isolates of P. infestans and 92 DNA fingerprints captured on FTA cards were sampled from commercial and seed production fields in three major potato production regions (western, eastern, and central) during the main-season and late-season in Algeria over six cropping seasons (2010–2016). Genotypes of P. infestans and population genetic diversity were analysed using a 17-plex simple-sequence repeat (SSR) marker assay, and the mating type of all isolates was characterized. Both mating types (A1 and A2) were found, and often occurred in the same field. Differences in mating type proportion were observed between regions and between sampling periods. Analysis with SSR markers showed the prevalence of the EU_13_A2 lineage (70%) over EU_2_A1 (16%), EU_23_A1 (10%), and 4% of unknown multilocus lineage (MLL). The EU_13_A2 showed differentiation within the group. EU_23_A1 was found mainly in late-season crops. However, the cropping region did not influence the distribution of lineages due to the dispersal of the pathogen in Algeria by seeds. Genetic structure did not reveal a clear variation in distribution of the three lineages throughout the sampling regions. These data provide important new information on the composition and change over time of P. infestans populations in Algeria and open the way for a better understanding of the local epidemiology of this important pathogen.  相似文献   

New detections of chestnut blight in Great Britain during 2019–2020 reveal high Cryphonectria parasitica diversity and limited spread of the disease     

Pedro Romon-Ochoa  Jelena Kranjec Orlović  Caroline Gorton  Alex Lewis  Sietse van der Linde  Ana Pérez-Sierra 《Plant pathology》2022,71(4):793-804

Cryphonectria parasitica was detected for the first time in the United Kingdom in 2011. A 2017–2018 survey detected the disease at different sites in Berkshire, Derbyshire, Devon, Dorset and London, while the present study comprises the results of the 2019–2020 survey with new findings and additional sites in the United Kingdom (Berkshire, Buckinghamshire, Cornwall, Derbyshire, Devon, London, West Sussex) and in Jersey, reflecting the progressive detection of more infected trees. A total of 189 samples were collected from 52 sites, and 123 samples tested positive both by quantitative real-time PCR and/or isolation from 43 sites. A total of 115 isolates were tested for mating type, vegetative compatibility group (VCG) and Cryphonectria hypovirus 1 (CHV-1). Twelve VCGs were identified, with four of them being first records in United Kingdom. The highest diversity of VCGs was detected in Devon followed by West Sussex while London and Derbyshire presented the lowest. Both mating types were detected (41% MAT-1 and 59% MAT-2), and no heterokaryons were detected. Perithecia of C. parasitica were not observed at any site during this survey. CHV-1 was detected in three isolates in very low concentration from three different locations in London and was always the unmutated subtype I haplotype E-5. A greater diversity of VCGs at outbreak sites compared with previous surveys, combined with their scattered distribution and the slow spread of the pathogen, supports the hypothesis that this disease has been introduced through imports over time from Europe.  相似文献   

钾肥种类及用量对低温胁迫下苜蓿根颈糖类物质含量及抗寒性的影响     

孙明雪  张玉霞  夏全超  王显国  张庆昕  刘庭玉  张永亮 《干旱地区农业研究》2022,40(5):62-70

为探讨钾肥种类及用量对苜蓿越冬器官抗寒性的影响及根颈糖类保护物质代谢的生理机制,本研究对‘北极熊’紫花苜蓿（M.sativa ‘Gibraltar’）施用KCl、K₂SO₄和KH₂PO₄ 3种钾肥,设置100、200、300 kg·hm^-2K₂O（分别用K₁、K₂和K₃表示）3个施用量,以不施钾肥为对照（CK）,于封冻前期挖取苜蓿越冬器官模拟低温冷冻胁迫处理（4℃、-10℃、-20℃和 -30℃）,测定根颈活力、可溶性糖、蔗糖、果糖和淀粉含量。结果表明,随着低温冷冻胁迫温度的降低,KCl、K₂SO₄和KH₂PO₄处理的苜蓿根颈活力和淀粉含量表现为持续降低的变化趋势,在-30℃下达到最小值,且与4℃处理呈显著差异（P＜0.05）,分别较4℃处理降低了86.25％～91.59％和45.47％～66.07％;可溶性糖、蔗糖和果糖含量则表现为先升高后降低的变化趋势,且均在-20℃下达到最大值,分别达到431.00～513.93 mg·g^-1、235.23～329.05 mg·g^-1和185.75～243.79 μg·g^-1。随着钾肥施用量的增加,KCl、K₂SO₄和KH₂PO₄处理的苜蓿根颈活力、可溶性糖、蔗糖、果糖和淀粉含量均表现为先升高后降低的趋势;且在不同低温胁迫处理下以K₂SO₄处理效果最明显,并且在施用量为200 kg·hm^-2K₂O时,苜蓿根颈活力、可溶性糖、蔗糖、果糖和淀粉含量均与CK差异显著（P＜0.05）,分别较CK增长了56.03％～197.26％、16.38％～48.77％、24.13％～46.22％、30.53％～59.95％和35.73％～67.87％。因此,科尔沁沙地建植苜蓿宜施用K₂SO₄种类钾肥,建议施用量为200 kg·hm^-2K₂O,更有利于提高苜蓿越冬器官的抗寒性。  相似文献   

西藏东南部典型林草交错地带不同植被地表节肢动物多样性研究     

臧建成  孙涛  洪大伟 《西北农林科技大学学报(自然科学版)》2021,49(3):93-100

【目的】了解西藏东南部不同植被类型对地表节肢动物群落结构及多样性的影响。【方法】采用陷阱诱捕法于2018年5~9月对高山栎灌丛、高山栎灌丛林牧交错地带(林牧交错地带)、天然草地、人工种植草地4种典型植被类型进行地表节肢动物调查,分析其相对多度、类群丰富度、Shannon-Wiener多样性指数、Pielou均匀度指数、Simpson优势度及相似性指数S-rensen和Cody。【结果】1）西藏东南部不同植被群落之间地表节肢动物群落组成和数量有较大差异。天然草地具有最多的节肢动物科类群数,地表节肢动物有77科,动物数占全部采集样数的32.36%;其次是林牧交错地带,地表节肢动物有75科,动物数占全部采集样数的32.77%;类群相对较少的是高山栎灌丛和人工草地,分别为59和55科,动物数分别占全部采集样数的9.27%和25.60%;高山栎灌丛采集到的动物数量最少,且不同类群间差异较大。2）类群丰富度天然草地最高,人工草地最低;Shannon-Wiener多样性指数天然草地最高,高山栎灌丛最低;Pielou均匀度指数高山栎灌丛最低,天然草地最高;Simpson优势度指数高山栎灌丛最高,林牧交错地带最低。3）S-rensen相似性指数最高值出现在高山栎灌丛与林牧交错地带之间,高山栎灌丛与人工草地的S-rensen相似性指数和人工草地与林牧交错地带的接近,高山栎灌丛与林牧交错地带的S-rensen相似性指数和人工草地与天然草地的接近。高山栎灌丛与天然草地的Cody相似性指数最高,其次是林牧交错地带与天然草地;高山栎灌丛与林牧交错地带、人工草地与天然草地的Cody指数最小。【结论】西藏东南部植被类型、环境、干扰程度均对地表节肢动物有较大影响。林牧交错地带是高山栎灌丛与天然草地之间的过渡地带,天然草地是林牧交错地带与人工草地之间的过渡地带,但在演替过程中具有连续性。  相似文献   

西南喀斯特地区典型土壤碳通量原位监测的研究   总被引：1，自引：0，他引：1  

胡乐宁  苏以荣  何寻阳 《水土保持通报》2013,33(3):109-113

为了研究西南喀斯特地区典型土壤碳通量特征,以不同植被类型和不同土石界面为研究对象,原位测定3种土壤(红壤、棕色石灰土和黑色石灰土)2个界面(土面、土石面)的乔木林地和灌丛的土壤碳通量,并用土壤碳通量的日变化和季变化指示土壤有机碳转化过程.结果表明,在雨季各土壤碳通量均高于旱季.棕色石灰土在2种植被类型条件下均没有红壤土壤碳通量稳定,受湿度影响大于红壤.黑色石灰土中,灌丛的土石面土壤碳通量与土面差异小于乔木林地,乔木林地中土面土壤碳通量显著大于土石面,土面在7月出现最高值(3.0μmol m2/s),土石面在6月出现最高值(1.5μmol m2/s);灌丛土面土壤碳通量最高值出现在7月(3.0μmol m2/s),土石面6月出现最高值(1.9 μmol m2/s).喀斯特地区土壤碳通量的变化因土壤类型不同而存在差异,土面和土石面的喀斯特土壤碳通量差异受气候、季节和植被的影响较大.  相似文献   

基于改进RVA法的黑河上游水文情势变化分析     

张如强  刘俊国  冒甘泉  王丽 《干旱区研究》2021,38(1):29-38

客观地评价水文情势变化是进行河流生态修复和流域水资源综合管理的基础。改进RVA法将径流典型年份的变化纳入整体改变度的计算过程中,相对更全面地评价径流水文情势的变化。近几十年来黑河流域气候条件的发生显著变化,黑河上游河流水文情势的变化情况仍需进一步研究。以黑河上游为研究区域,应用M-K检验识别径流的突变年份,采用改进RVA法计算分析黑河上游河流水文情势变化。结果表明,黑河上游径流的突变年份为2002年,2002年前后分别以平水年和丰水年为主;采用RVA法计算的整体改变度为54.68%,而改进的RAV方法计算的整体改变度为74.62%,说明RVA法低估了黑河上游水文情势整体改变度;黑河上游径流水文情势变化主要包括:相比于1960—2002年,2003—2015年后各月平均流量均呈不同程度增加,但最小1日、3日、7日和最大7日流量减小,其余极端流量指标呈不同程度增加,高、低流量发生次数及历时变化微弱,流量平均增加率、减小率以及逆转次数均增加;采用改进的RVA法计算的黑河上游水文情势的整体改变度为74.62%,属于高度改变。气候变化是导致黑河上游水文情势高度改变的主要原因。  相似文献   

Children's perspectives on vegetation establishment: Implications for school ground greening     

Märit Jansson  Allan Gunnarsson  Fredrika Mårtensson  Sarah Andersson 《Urban Forestry & Urban Greening》2014,13(1):166-174

School ground greening might provide multiple benefits for children across age, gender and competence through allowing participation in the greening process and experience of nature and vegetation. However, the process of school ground greening must nurture a positive relationship between children and newly planted vegetation during the first years after establishment. This study explored how green space planning, management and maintenance approaches influence children's school ground use and experiences through a series of field observations following establishment of new vegetation in a landscaped area at a school in Malmö, Sweden. The methods included documentation of vegetation, observations of use and interviews with children and teachers on three occasions during one and a half years following the first planting. The greening approach appeared successful, especially for younger children (up to around 11 years), who were more positive and also used the area more than older children. They also used it for pretend play, which was rare in the school ground before greening. Experiences from continuous participation and physical use appeared important for children establishing a positive and caring relationship with the landscaped area. The results suggest that school ground greening should be well integrated with pedagogic activities. Damage to woody vegetation can be limited by establishing other landscape elements that are attractive for play and by using fences without hindering access.  相似文献   

Seasonal dynamics of soil nitrogen availability and phosphorus fractions under urban forest remnants of different vegetation communities in Southern China     

Jing Fan  Jing-Yuan Wang  Xiao-Fei Hu  Fu-Sheng Chen 《Urban Forestry & Urban Greening》2014,13(3):576-585

Urban forest remnants are a useful tool to study forest response to global change with urbanization. Soil nutrient status in urban forests has not been well understood, especially under the pressure of rapid urbanization in developing countries. In this study, ion-exchange resin bags and a modified Hedley P fractionation procedure were used to measure seasonal dynamics of soil N forms (ammonium and nitrate) and P fractions (available, labile, slow, occlude and weathered mineral P) under urban forest remnants across a successional sequence and non-forest land in the city of Nanchang, Southern China. Results showed that soil N availability varied with season and vegetation community (P < 0.05). Soil P fractions showed minimal seasonal variation except available P, while their averages generally increased with forest development from non-forest land to coniferous forest to conifer-broadleaf mixed forest to evergreen broad-leaved forest. The ratios of fresh soil N forms to P fractions generally decreased with forest development, while N forms absorbed by resins to P fractions generally increased from non-forest land to coniferous forest, then decreased from conifer-broadleaf mixed forest to evergreen broad-leaved forest. It is suggested that urban older forest remnants could easily move to N saturation status and soil P enrichment, causing urban water pollution due to the accumulative effect of elevated atmospheric N deposition and exogenous P input with urbanization.  相似文献   

不同香型绿茶的香气成分组成及香型形成的影响因素分析     

尤秋爽  李勤  朱荫  石亚丽  马婉君  林智  吕海鹏 《中国茶叶》2022,(1):7-18

绿茶风味宜人,保健功效显著,深受国人的喜爱,是我国生产量和消费量最大的一类茶叶.香气是评价绿茶品质的重要指标之一,绿茶的香气中呈现出了多种香型,例如清香、栗香、花香和嫩香等,是绿茶香气品质优异的体现之一,引起了人们的广泛关注.文章总结了绿茶不同香型的化学物质基础及其香型形成的主要影响因素等,以期为今后开展不同香型绿茶产...  相似文献