长期保护性耕作对丛枝菌根真菌多样性的影响

为了明确我国北方干旱地区长期保护性耕作以及深松对丛枝菌根真菌(AMF)多样性的影响,笔者于2014年在山西省临汾市连续22年实施保护性耕作的长期定位试验基地,针对免耕覆盖(NTS)、深松免耕覆盖(SNTS)及传统耕作(TT)3种处理方式,进行了不同耕作条件下土壤AMF物种丰度、孢子密度、Shannon多样性指数以及AMF侵染率等因素的比较研究。结果显示,长期保护性耕作(NTS和SNTS)共分离鉴定出AMF 7属9种,其中根孢囊霉属(Rhizophagus)和斗管囊霉属(Funneliformis)各2种,球囊霉属(Glomus)、近明球囊霉属(Claroideoglomus)、无梗囊霉属(Acaulospora)、硬囊霉属(Sclerocystis)和隔球囊霉属(Septoglomus)各1种;而传统耕作(TT)共分离鉴定出AMF 6属8种,没有检测到无梗囊霉属。NTS、SNTS和TT处理在不同土层的AMF优势种基本一致,0~40 cm土层为摩西斗管囊霉(Fu.mosseae)和变形球囊霉(G.versiforme),40~80 cm土层为摩西斗管囊霉、变形球囊霉和聚丛根孢囊霉(Rh.aggregatum),80~120 cm土层为聚丛根孢囊霉,120 cm土层以下只有NTS和SNTS处理中存在聚丛根孢囊霉,说明保护性耕作措施促进了AMF向土壤深层发展。NTS和SNTS处理在同一土层的AMF物种丰度、孢子密度和Shannon多样性指数均高于TT处理,SNTS处理高于NTS处理。同一耕作措施不同土层的AMF物种丰度、孢子密度和Shannon多样性指数均随土层加深而逐渐降低;NTS和SNTS处理在小麦各生育期的丛枝侵染率和孢子密度均高于TT处理;各处理在小麦拔节期的AMF侵染率最高,分别为14.9%、16.1%和10.6%,而在收获期的土壤孢子密度最高,分别为111.7个·(100g)~(-1)、125.0个·(100g)~(-1)和90.3个·(100g)~(-1)。研究认为,长期免耕覆盖、尤其深松免耕覆盖,提高了AMF多样性。该研究结果可为中国北方旱作农田生态系统中AMF自然潜力的充分发挥,以及保护性耕作技术的合理应用提供科学依据。

Effect of long-term conservation tillage on arbuscular mycorrhizal fungi diversity

To verify the effect of long-term conservation tillage and subsoiling on arbuscular mycorrhizal fungi (AMF) diversity in dry areas in northern China, a comparative analysis of species richness, spore density, Shannon diversity index and colonization rate of AMF among no-till with straw mulching (NTS), no-till with straw mulching after subsoiling (SNTS) and traditional tillage treatment (TT) were conducted in 2014 at a long-term (22 years) positioning test base for conservation tillage in Linfen, Shanxi Province. In the study, 9 AMF species belonging to 7 genera were isolated and identified in soil samples of NTS and SNTS treatments, including two species each of Rhizophagus and Funneliformis and one species each of Glomus, Claroideoglomus, Acaulospora, Sclerocystis and Septoglomus. Also 8 AMF species belonging to 6 genera were isolated and identified in soil samples of TT treatment. The AMF species in the TT treatment were the same with those in NTS and SNTS treatments, except that there was no Acaulospora.The dominant species of AMF in NTS, SNTS and TT treatments were the same. The dominant species of AMF in the 0-40 cm soil layer were mainly Fu. mosseae and G. versiforme, the 40-80 cm soil layer were Fu. mosseae, G. versiforme and Rh. aggregatum, and the 80-120 cm soil layer was Rh. aggregatum. Below the 120 cm soil layer, the dominant AMF species was Rh. aggregatum, which was found only under NTS and SNTS treatments. Species richness, spore density and Shannon diversity index of AMF in NTS and SNTS treatments in the same soil layers were higher than those in TT treatment, and those in SNTS treatment were higher than those in NTS treatment. Species richness, spore density and Shannon diversity index of AMF decreased with increasing of soil depth under the same treatment. The maximum species richness, spore density and Shannon diversity index of AMF were all in the 0-20 cm shallow soil layer. The colonization rate and spore density of AMF at different growth stages of wheat in NTS and SNTS treatments were all significantly higher than that in TT treatment. Colonization rate of AMF in NTS, SNTS and TT treatments was the highest at jointing stage of wheat and was respectively 14.9%, 16.1% and 10.6%. AMF spore density of soil was the highest at maturity stage of wheat and was respectively 111.7 spores·(100g)^-1, 125.0 spores·(100g)^-1 and 90.3 spores·(100g)^-1. The study showed that long-term no-till with straw mulching improved AM fungi diversity, especially under no-till with straw mulching after subsoiling. The results provided the scientific basis for the full play of AMF role and reasonable application of conservation tillage in dry farmland ecosystems in northern China.