黃芳 徐玉梅 王健 劉曉琴
摘? ? 要:【目的】明確山西省果樹根際土壤線蟲群落結(jié)構(gòu)及其物種多樣性。【方法】以山西省晉中市太谷區(qū)不同管理模式的3個代表性果園為研究對象,采用淺盤分離法對土壤線蟲進(jìn)行分離鑒定及營養(yǎng)類群分析,系統(tǒng)研究了杏樹、葡萄樹、棗樹、蘋果樹、梨樹、桃樹和核桃樹等7種果樹根際土壤線蟲多度和優(yōu)勢度、營養(yǎng)類群,并分析線蟲在果樹根際土壤中的垂直分布。【結(jié)果】在果園0~60 cm土層范圍內(nèi)都發(fā)現(xiàn)有土壤線蟲,其中多集中于20~30 cm土層中。共鑒定出土壤線蟲2綱4目15科26個屬,包括捕食/雜食線蟲2屬,食真菌線蟲3屬,食細(xì)菌線蟲6屬,植物寄生線蟲15屬,其中食細(xì)菌線蟲中的桿屬(Mesorhabditis)以及植物寄生線蟲中的絲尾墊刃屬(Filenchus)為優(yōu)勢屬。以果樹根際土壤線蟲群落作為研究對象,主要研究其營養(yǎng)類群,結(jié)果表明,食細(xì)菌線蟲為第一大營養(yǎng)類群,植物寄生線蟲為第二大類群,食真菌線蟲為第三大類群,雜食-捕食性線蟲為第四大類群?!窘Y(jié)論】土壤線蟲主要集中于果樹根際20~30 cm土層中,果樹根際土壤中共鑒定到2綱4目15科26個屬線蟲,優(yōu)勢營養(yǎng)類群為食細(xì)菌線蟲。研究結(jié)果對山西果樹土壤環(huán)境監(jiān)測和提高果園管理具有重要意義。
關(guān)鍵詞:果園;土壤線蟲;多樣性;優(yōu)勢度;營養(yǎng)類群
中圖分類號:S66 文獻(xiàn)標(biāo)志碼:A 文章編號:1009-9980(2023)12-2591-07
收稿日期:2023-06-12 接受日期:2023-08-31
基金項目:國家自然科學(xué)基金(31801958);山西大同大學(xué)科研基金(2020K6)
作者簡介:黃芳,女,副教授,碩士,研究方向為植物病理學(xué)。E-mail:huangf09@163.com
Research on the community structure and diversity of soil nematodes in the orchards of Shanxi province
HUANG Fang1, XU Yumei2, WANG Jian1, LIU Xiaoqin1
(1School of Medicine, Shanxi Datong University, Datong 037009, Shanxi, China; 2College of Plant Protection, Shanxi Agricultural University, Taigu 030801, Shanxi, China)
Abstract: 【Objective】 It is crucial to study the community structure and diversity of nematodes in the rhizosphere of orchards for preventing soil degradation. This research aims to investigate the community structure and species diversity of nematodes in the rhizospheric soil of fruit trees in the orchards of Shanxi province. The study was conducted at three different locations, including seven species of fruit crops and six rhizosphere depths. 【Methods】 The test samples for this study were selected from the orchard of Shanxi Academy of Agricultural Sciences, Polomogy Istitute, Shanxi Agricultural University and Hancun village orchards. Nematodes were collected from the rhizosphere of seven different fruit crops, namely apricot (Armeniaca vulgaris), grape (Vitis vinifera), jujube (Ziziphus jujuba), apple (Malus pumila), pear (Pyrus sp.), peach (Prunus perisica) and walnut (Juglans regia). Soil samples were collected using the five-point sampling method with a cylinder driller. The rhizosphere of the fruit trees was sampled at a depth of 5-30 cm. For each tree, 100 g of soil was taken in four directions. These soil samples were mixed, and 500 g of soil was selected as the final sample. The sampling site, data, and host plant were marked. The specimens were then brought back to the lab for further treatment. In each sample plot, three samples were taken, resulting in a total of 189 soil samples collected in three replicates. The Shanxi Fruit Research Institute conducted vertical distribution plots of soil nematodes in the rhizosphere of fruit trees. The soil depth was divided into six levels: 0-10 cm, >10-20 cm, >20-30 cm, >30-40 cm, >40-50 cm and >50-60 cm. The five-point sampling method was used to select soil samples from the same layer and fruit tree. A sample of 500 g of mixed soil was taken and three samples were collected from each sample plot. In total, 126 soil samples were collected in three replicates, resulting in a total of 315 soil samples for the experiment. The collected samples were promptly stored in a 4 ℃ refrigerator upon arrival at the laboratory. Nematode populations in a 100 g soil sample were extracted using the Whitehead tray method. The abundance of nematodes was determined by counting the quantity of nematodes per 100 g of dry soil. The nematodes were then authenticated and counted under a microscope. The soil nematode communities were classified into four trophic groups based on their feeding habits and esophageal characteristics: plant-parasitic nematodes, fungivore, bacterivore and omnivore-predator feeders. They were further classified into three groups based on the number of individuals in each genus. The genus with more than 10% of the total of individuals was considered dominant, those with 1% to 10% were considered common, and those with less than 1% were considered rare. 【Results】 The study identified a total of 26 genera of nematodes belonging to two classes, four orders and 15 families. Among these, 15 genera were identified as plant-parasitic nematodes, 6 genera as bacterivores, 3 genera as fungivores and 2 genera as omnivore-predator feeders. In the soil surrounding various fruit trees, the dominant genera were Filenchus and Mesorhabditis, which accounted for 36.32% of the total population. Filenchus was classified as a plant-parasitic trophic nematode, while Mesorhabditis was classified as a bacterivore. Common genera included Aphelenchoides, Aphelenchus, Rhabditis, Cephalobus, Ditylenchus, Mesodorylaimus, Dorylaimus, Protorhabditis, Eucephalobus, Alaimus, Tylenchus, Paratylenchus, Pratylenchus, Tylenchorhynchus, Criconemella, Xiphinema, Longidorus, Doryllium, Eudorylaimus and Aporcelaimus, accounting for 61.58% of the total population. Rare genera including Psilenchus, Helicotylenchus and Rotylenchus accounted for 2.1% of the total population. The investigation and analysis conducted at Shanxi Agricultural University orchard focused on the total number of soil nematodes present in the rhizosphere soil of fruit trees. The findings revealed that the range of nematodes varied from 530 to 940 per 100 g of dry soil, with an average of 684 nematodes per 100 g of dry soil. However, the number differed in the other two sites. The study also observed variations in the total number of soil nematodes among different host species and geographical environments. The dominant trophic group was bacterivore, followed by plant-parasitic nematodes, while fungivores and omnivore-predators were present in lower quantities. Nematodes were distributed throughout the 0-60 cm soil layer, with the highest number observed at a depth of >20-30 cm. Among the fruit species, apple and pear exhibited the highest number of nematodes in each soil layer, followed by grape vines. Jujube and peach trees had a lower number of soil nematodes. 【Conclusion】 The study revealed that the highest abundance of nematodes was primarily concentrated in the >20-30 cm soil layer within the rhizosphere soil of fruit trees. Additionally, the study conducted has identified 26 genera of soil nematodes belonging to two classes, four orders, and 15 families. The dominant trophic group observed was bacterivore or bacteria-feeding nematodes, which indicated that the soil was in a healthy state. The study is of great significance for monitoring soil environment and improving management of orchards in Shanxi province. At present, the soil environment in orchards of Shanxi province is healthy, but it is advisable to regularly monitor plant-parasitic nematodes in orchards to ensure timely detection.
Key words: Orchard; Soil nematodes; Diversity; Dominance; Trophic groups
線蟲是土壤中最豐富的低等無脊椎動物,Van Den Hoogan等[1]估計地球上土壤線蟲數(shù)量高達(dá)4.4×1020頭。土壤線蟲的60%~80%是自由生活線蟲,在土壤食物網(wǎng)的氮礦化和有機(jī)質(zhì)分解中起著重要作用,有些因?qū)κ澄镦満铜h(huán)境反應(yīng)敏感,可根據(jù)土壤線蟲種群變化用于指示土壤環(huán)境的優(yōu)劣[2-5]。還有一些植物寄生線蟲可引起植物病害,對作物造成經(jīng)濟(jì)損失。根據(jù)線蟲的取食習(xí)性,可將土壤線蟲分為食細(xì)菌類、食真菌類、植物寄生類和捕食/雜食類4個營養(yǎng)類群[6-7]。不同食性的營養(yǎng)類群,在土壤生態(tài)系統(tǒng)中的角色各不相同,尤其是在土壤生態(tài)系統(tǒng)穩(wěn)定性的維持方面作用重大。因此,明確土壤線蟲的營養(yǎng)類群及其生物多樣性對于土壤健康狀況和有害生物監(jiān)測具有重要的意義。
山西省是我國的水果主產(chǎn)區(qū)之一,果樹根際土壤線蟲種類豐富,但是對其生物多樣性研究方面報道較少,因此,筆者在本研究中選取山西省晉中市太谷區(qū)常見的杏、梨、蘋果、葡萄、棗、桃、核桃等7種果樹根際土壤線蟲進(jìn)行群落結(jié)構(gòu)和多樣性分析[8-9],旨在明確果樹根際土壤線蟲的種群數(shù)量及其分布情況,為我國土壤動物的生物多樣性研究提供豐富的資料,揭示土壤線蟲在評估土壤健康水平方面的生物指標(biāo)作用,為深入探究線蟲對果樹生產(chǎn)的危害以及控制果樹線蟲病害提供理論依據(jù)。
1 材料和方法
1.1 調(diào)查區(qū)自然概況
山西省晉中市太谷區(qū)(112°28′~113°01′ E,37°12′~37°32′ N)位于山西省中部,地處晉中盆地東北部,縣域地貌形態(tài)分為山地、丘陵、平原,地勢由東南向西北傾斜,海拔767~1914 m,屬暖溫帶大陸性氣候,四季分明。年平均氣溫9.8 ℃,無霜期175 d,年平均降水量462.9 mm,地下水資源可開采量9600 m3。春季少雨干燥多風(fēng),夏季暖熱多雨,秋季天晴氣爽,冬季漫長寒冷少雪。太谷區(qū)農(nóng)業(yè)基礎(chǔ)條件好,果樹產(chǎn)業(yè)為主要經(jīng)濟(jì)產(chǎn)業(yè)之一,全區(qū)果樹種植面積達(dá)到8120 hm2,主要種植的果樹有蘋果、梨、桃、核桃、葡萄、櫻桃、杏、山楂、棗等。
1.2 樣品采集
選取不同管理水平的3個果園:管理粗放的山西省農(nóng)業(yè)科學(xué)院果樹研究所、管理水平中等的山西農(nóng)業(yè)大學(xué)太谷校區(qū)果園和管理精細(xì)的山西省晉中市太谷區(qū)韓村果園為試驗樣地。同一樣地對不同樹種采用五點(diǎn)取樣法,用筒鉆取果樹根際5~30 cm深度的土壤樣本,將采集的5個取樣點(diǎn)的土壤樣品充分混合作為一個土樣,3次重復(fù)。每個重復(fù)土樣按四分法保留500 g土壤樣品,裝袋封口,并標(biāo)明采樣地、采樣時間、寄主植物等,帶回實驗室處理。共采集土樣63個。
選取山西省農(nóng)業(yè)科學(xué)院果樹研究所果園作為果樹根際土壤線蟲垂直分布樣地,按土壤深度分為6個層次(0~10 cm,>10~20 cm,>20~30 cm,>30~40 cm,>40~50 cm,>50~60 cm),按五點(diǎn)取樣法,不同樹種同一層取樣土充分混合后按四分法取500 g作為一個土樣,3次重復(fù),共采集土樣126個。本試驗共采集189個土樣,采集的土樣迅速帶回實驗室,放在4 ℃冰箱中保存。
1.3 線蟲分離、計數(shù)及鑒定
選用淺盤分離法[10]在室溫對線蟲進(jìn)行分離。每個土樣用電子秤準(zhǔn)確稱取土樣100 g,48 h后用20 μm分離篩收集線蟲懸浮液,濾去水至篩中剩余懸浮液30~50 mL,轉(zhuǎn)移50 mL的試管中,靜置3 h,去掉上清液,剩下20 mL線蟲懸浮液,備用。
搖勻線蟲懸浮液,用移液槍取2 mL液體放入表面皿中,在體視顯微鏡下察看并計算線蟲總數(shù)。共3次重復(fù),結(jié)果取平均值,計算每100 g干土壤中存在的線蟲數(shù)量,最后統(tǒng)計每個分離樣品中線蟲的數(shù)量。
用自制的睫毛挑針挑取線蟲,然后放在滴有小水滴的載玻片上,用挑針把浮在水表面的線蟲輕輕壓入水中,蓋上蓋玻片。在光學(xué)顯微鏡下觀察,并依據(jù)《An illustrated key to nematodes found in fresh water》[11]、《植物線蟲分類學(xué)》[12]和《植物線蟲志》[13]將其鑒定到屬。
1.4 優(yōu)勢度
將每個樣本中線蟲個體數(shù)量按照其所處屬中的比例劃分為3個優(yōu)勢度級別。群體中占據(jù)超過10%的物種可以稱作優(yōu)勢屬;占據(jù)1%~10%的為常見屬;而占據(jù)不到1%的則屬于稀有屬。
1.5 線蟲營養(yǎng)類群的劃分
通過觀察線蟲的攝食行為和食道結(jié)構(gòu),筆者可以將土壤中的線蟲群落分為4類不同的營養(yǎng)群[6-7,14]:食細(xì)菌類群(bacterivores feeders,BF)、食真菌類群(fungivores feeders,F(xiàn)F)、植物寄生類群(plant-parasites,PP)和捕食-雜食類群(omnivores-predators,OP)。
2 結(jié)果與分析
2.1 線蟲在果樹根際土壤中的垂直分布
不同果樹根周圍土壤線蟲的垂直分布情況見圖1,結(jié)果顯示在0~60 cm深度范圍內(nèi)土壤線蟲均有分布,尤其是>20~30 cm深度范圍內(nèi)的土壤線蟲數(shù)量最為豐富。各土層中核桃樹、蘋果樹和梨樹的線蟲數(shù)量較多,其次是葡萄樹,棗樹和桃樹根圍土壤線蟲數(shù)量較少。
2.2 土壤線蟲多度與優(yōu)勢度
筆者在本試驗中共分離到2綱4目15科26屬線蟲,如表1所示,包括15個屬的植物寄生線蟲、6個屬的食細(xì)菌線蟲、3個屬的食真菌線蟲以及2個屬的捕食/雜食線蟲。在所得到的26個屬中,優(yōu)勢屬為絲尾墊刃屬和中桿屬,占線蟲總數(shù)的36.32%;常見屬為頭葉屬、擬滑刃屬、莖屬、真滑刃屬、滑刃屬、中矛線屬、矛線屬、小桿屬、原桿屬、真頭葉屬、無咽屬、墊刃屬、小環(huán)屬、劍屬、針屬、長針屬、短矛屬、短體屬、真矛線屬、孔咽屬和矮化屬,占線蟲總數(shù)的61.58%;稀有屬為平滑墊刃屬、螺旋屬和盤旋屬,占線蟲總數(shù)的2.10%。
對土壤線蟲總數(shù)的調(diào)查分析(圖2)發(fā)現(xiàn),山西農(nóng)業(yè)大學(xué)果園果樹根際土壤線蟲總數(shù)范圍為500~950條·100 g-1,平均為681條·100 g-1,不同寄主之間線蟲多度差異顯著,杏樹的線蟲多度最高,其他寄主的線蟲多度均顯著低于杏樹,其中,以蘋果樹線蟲多度最低;韓村果園果樹根際土壤線蟲總數(shù)范圍為80~1750條·100 g-1,平均為1031條·100 g-1,不同寄主之間線蟲多度差異顯著,以棗樹的線蟲多度為最高,其他寄主的線蟲多度均顯著低于棗樹,其中部分寄主的線蟲多度相互間也具有顯著差異,以杏樹的線蟲多度為最低;山西省農(nóng)業(yè)科學(xué)院果樹研究所果樹根際土壤線蟲總數(shù)范圍為400~1100條·100 g-1,平均為601條·100 g-1,不同寄主之間線蟲多度差異顯著,以蘋果樹的線蟲多度最高,杏樹和梨樹次之,其他寄主的線蟲多度相互間不具有顯著差異。在相同地理環(huán)境下不同寄主的土壤線蟲多度不同,不同地理環(huán)境下相同寄主線蟲多度也不同。
2.3 土壤線蟲營養(yǎng)類群
從土壤線蟲的營養(yǎng)類群成分的分析結(jié)果(圖3)來看,在山西農(nóng)業(yè)大學(xué)果園7種果樹的根際土壤中,食細(xì)菌線蟲占比最高,占總體的50%以上,但棗樹例外,其占比僅為22.39%,其次,植物寄生性線蟲和真菌食性線蟲是占據(jù)較高比例的種類,而以捕食和雜食為主的線蟲占比最少,占總體的2%以下;在韓村果園7種果樹的根際土壤中,植物寄生性線蟲占比最高,但葡萄和桃樹根際土壤中植物寄生性線蟲僅占比26.79%和35.14%,食細(xì)菌線蟲以及真菌食性線蟲占比次之,而以捕食和雜食為主的線蟲占比最少,占總體的2%以下;在山西省農(nóng)業(yè)科學(xué)院果樹研究所7種果樹的根際土壤中,占比最高的是食細(xì)菌線蟲,但棗樹例外,其占比僅為27.91%,其次,植物寄生性線蟲及真菌食性線蟲是占據(jù)較高比例的種類,而以捕食和雜食為主的線蟲占比最少,占總體的1%以下。
3 討 論
土壤線蟲是土壤食物鏈中重要的組成部分,對植物生長的土壤環(huán)境和地上植物具有重要影響。了解果園土壤線蟲群落的分布及生物多樣性,對深入認(rèn)識果園土壤環(huán)境、提高果園管理水平具有重要意義。
筆者對土壤線蟲垂直分布研究發(fā)現(xiàn),線蟲多集中于中層土壤,可能的原因是表層土壤屬于砂質(zhì)土,孔隙度小、水分含量不高,且線蟲的繁殖數(shù)量相對較稀少,尤其是位于土壤表層的0~10 cm深度,線蟲數(shù)量更是極少。線蟲分布受多種因素影響,如水分、植物根分泌物、土壤質(zhì)地、溫度和透氣狀況等。線蟲通常難以在淺層土壤中生存,數(shù)量也較少。相比之下,在深20~30 cm的土壤中更有利于線蟲的繁殖和生存。
Viketoft等[15-17]的試驗結(jié)果表明,植物的特征和功能類型明顯地影響著線蟲群落的多樣性。但是,Viketoft[16]研究了一個半自然草地的線蟲群落,只用了8 g濕土進(jìn)行調(diào)查,這個樣本量遠(yuǎn)遠(yuǎn)少于大多數(shù)線蟲學(xué)家通常使用的200 g濕土來分析線蟲群落。因此,這個樣本的代表性可能存在問題。盡管各項結(jié)果有所不同,但所有這些研究都表明,植物的屬性和功能類型會對線蟲群落的多樣性產(chǎn)生影響。
對線蟲土壤營養(yǎng)類群分析發(fā)現(xiàn),食細(xì)菌線蟲和植物寄生線蟲是山西省果樹根際的主要營養(yǎng)類群,研究結(jié)果與樊金玲[18]報道的山西省果樹根際線蟲群落結(jié)構(gòu)的結(jié)果保持一致。通過比較管理模式發(fā)現(xiàn),管理粗放的山西農(nóng)業(yè)大學(xué)和山西省農(nóng)業(yè)科學(xué)院果樹研究所果園以食細(xì)菌線蟲為主,而管理精細(xì)的韓村果園則以植物寄生線蟲為主。食細(xì)菌線蟲與土壤肥力和植物生產(chǎn)力密切相關(guān),據(jù)初步統(tǒng)計,在1 m2森林中就有數(shù)十萬頭食細(xì)菌線蟲存在,一條食細(xì)菌線蟲可每天捕食106個細(xì)菌[19],但是果樹根際的食細(xì)菌線蟲與土壤肥力的相關(guān)性還有待于進(jìn)一步研究。其次,植物寄生線蟲通過食道腺分泌物和口針穿刺等對植物造成直接危害,每年對全球造成的經(jīng)濟(jì)損失高達(dá)3582億美元[20]。在筆者報道的類群中,短體屬(Pratylenchus)可引起植物根腐病害,該屬中的非中國種類是我國對外有害生物檢疫對象;此外,劍屬(Xiphinema)和長針屬(Longidorus)可通過傳播植物病毒對植物造成間接傷害,這2個屬線蟲可在葡萄、桃樹和梨樹上傳播葡萄鉻色花葉病毒、葡萄扇葉病毒、桃叢簇花葉病毒和梨石果病毒等[21],因此建議在果樹上定期監(jiān)測植物線蟲病害及植物病毒病害。
4 結(jié) 論
筆者對山西省晉中市太谷區(qū)果樹根際土壤線蟲的種群數(shù)量和分布情況進(jìn)行研究,線蟲主要分布于果樹根際>20~30 cm土層中,共鑒定到2綱4目15科26個屬線蟲,食細(xì)菌線蟲是主要的營養(yǎng)類群,植物寄生線蟲次之。因此該地區(qū)土壤營養(yǎng)類群屬于健康,但是應(yīng)及時監(jiān)測果園內(nèi)植物寄生線蟲的危害。
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