根系与土壤微生物

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固氮根瘤菌
Rhizobium bacteria： • • In legumes (e.g., Lupine, clover, alfalfa, soybean). Can fix up to 300 kg ha-1 yr-1
Frankia actinomycetes: • • • In selected trees and shrubs (Alnus, Myrica, Elaeagnus, Ceanothus, Cuasarina) More important than legumes in forests. Can also fix up to 300 kg ha-1 yr-1
• 牧食食物链： if primary production sources are living, the linkages are called a grazing food chain • 碎屑食物链: if primary production sources are dead, the linkages are termed a detrital food chain
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Methods for Quantifying Root Turnover
• Destructive Sampling (harvest by soil core , Isotopic Methods) • Non-destructive Sampling (rhizotron and minirhizotron)
根系与土壤微生物 Roots and soil microbes
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土壤生态系统的结构
降水 气体扩散 辐射和热量平衡
枯落物
蒸发
气体扩散
取
食
亡 死
取食
自养微生物
捕食
同 化
吸
凋落、分泌
收
土壤环境
(水、热、气和矿物质) 地下水上升 水分下渗 矿物淋溶
吸收
土壤动物
捕食
土壤有机质
淋溶
死亡
分解 、矿 化
死亡
异养微生物
质，在土壤形成和发育、土壤肥力演变、养分有效化和有 毒物质降解等方面起着重要作用，被称为“eye of needle”。
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我国不同土壤微生物数量（104个/g 土）
土壤 黑土 灰褐土 黄绵土 红壤 砖红壤 植被 林地 草地 林地 草地 林地 草地 林地 草地 细菌 3370 2070 438 357 144 100 189 64 放线菌 2410 505 169 140 6 3 10 14 真菌 17 10 4 1 3 2 12 7
Direct nagetive effects Induces fungal pathogen growth Attracts root-feeding nematods
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Methods to separate total CO2 efflux into that from roots and heterotrophic populations: • • • • • component integration root exclusion tree girdling isotopic approach ……
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• 土壤微生物Soil microbes • 土壤动物Soil fauna
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土壤微生物Soil microbe
土壤微生物包括： 细菌、真菌、放线菌、病毒
特点：在土壤中数量高，繁殖快。如一般土壤中细菌为
107～108个/g；真菌105～106个/g土；放线菌106～107个/g 土
作用：参与土壤物质转化过程，分解有机质、合成腐殖
Carbon release into the rhizosphere
Indirect nagetive effects Induces immobilization of nutrients making them less plant available Induces microbial phytotoxin production
养分活化与固定 微生物的养分和能源
抵御铁、铝、锰的毒害 微生物能源
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Direct positive effects Stimulate mycorrhizal infection Induces nodule formation Detoxifies rhizotoxic metals Increase nutrient availability Improve soil water holding capacity Suppresses pathogens
Isotopic Methods
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Rhizotron method
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8月 Aug. 15
9月 Sept. 9
10月 Oct. 11
11月 Nov.17
A progressive change of Thelephoroid mycorrhizal rootlets under a mixed conifer stand near Blodgett Forest Station. These images were obtained using a minrhizotron video camera system with a precision indexing handle in 2000. The width of each image is approximately 1.0 cm in real dimension.
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Main mycorrhizal types
Ectomycorrhizae (ECM)：penetrate only outer cell layers of tree roots and only intercellular spaces, form a sheath/mantle of mycelium on fine roots called Hartig Net Endomycorrhizae : penetrate host cells, vesicular arbuscular mycorrhizae (VAM/VA/AM) form vesicles inside host cells for storage
Indirect positive effects Supports associative N2 fixation and N transfer to the plant Induces plant hormone and vitamin production by microbes which enhances plant growth
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菌根真菌 Mycorrhizal fungi
Mycorrhizae (fine root/fungal mutalistic symbiotic association) - plant provides sugars to fungus (at a cost of 5-30% of the total photosynthate translocated belowground) - fungus provides nutrients and water to plants and protects plants against pathogens
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其它土壤初级生产者： 藻类（蓝藻、绿藻和硅藻） 5％ total NPP
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根的共生微生物 Symbiotic associates of roots
• 根瘤Nodules：symbiotic N fixers live in nodules of roots in certain plants • 菌根Mycorrhizae: symbiotic with plant roots, help take up water and nutrients
Fine root production (FRP) measurements: • Sequential core method • Maximum-minimum method • Ingrowth core method • Nitrogen budget method
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D. Milchunas & W. Lauenroth, 2001. Ecosystems 4:139-150
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Soil core method
Root biomass
Time
• Root diameter • Spatial distribution • Temporal distribution
Peak-trough calculation
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细根(fine root): 直径 < 2 mm
Annual losses of fine root biomass Ecosystem Deciduous forest European beech Oak Liriodendron Walnut Coniferous forest Douglas fir Scots pine 40-47 66 80-92 52 42 90 Loss (% total)
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Hartig net Mantle
Two ectomycorrhizal fungi forming mantle on same fine root
Cross section of Douglas-fir fine Root showing ectomycorrhizal mantle and Hartig net
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Ectomycorrhizal roots
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Basidiomycetes
Suillus sp.
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ENDOБайду номын сангаасYCORRHIZAE Arbuscular mycorrhizae Arbuscules
Vesicles
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根产物中有机物质的种类及其在植物营养中的作用
在植物营养中的作用
根产物中有机物质的种类 糖 类 低分子有机化合物 有机酸 氨基酸 酚类化合物 高分子粘胶物质 细胞或组织脱落物及其 溶解产物 多糖、酚类化合物 多聚半乳糖醛酸等 根冠细胞
2 土壤生态系统边界
土壤环境
土壤中的初级生产力 （belowground primary production）
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NPP = gross primary production – plant respiration
A simple assumption: belowground primary production equals that of production aboveground for total net primary production (NPP) (Fogel, 1985). However, this assumption is inadequate and often very wrong. Quantifying NPP belowground remains a real challenge
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3、化能自养 以CO2作为碳源，再从氧化无机物中获取能量。这类微生物虽 在土壤中种类不多，但它们在土壤物质转化中起了重要作用。属 于这一类的土壤微生物主要有：亚硝酸细菌、硝酸细菌、硫氧化 细菌、铁细菌和氢细菌等。
4、光能自养 利用光能进行光合作用，以无机物作为供氢体以还原CO2，从 而合成细胞物质。光合细菌中绿硫细菌、紫硫细菌都属于光能自 养型。
（据《中国土壤》，1987）
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土壤微生物的营养类型
1、化能异养 需要有机化合物作为碳源，通过氧化有机化合物来获取能量。 土壤中绝大部分细菌和几乎全部真菌属于这个类型，这类微生物 是土壤中起主导作用的微生物。 2、光能异养 其能源来自光，但需要有机化合物作为供氢体以还原CO2，并 合成细胞物质。如紫色非硫细菌中的深红红螺菌 （Rhodospirillum rubrum）可利用简单有机物作为供氢体。
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土壤中的次级生产力 （belowground secondary production）
The production of new body tissues by heterotrophs from primary production is called secondary production. CnH2nOn ＋ nO2 → nCO2 ＋ nH2O