美国土壤分类系统有几大土纲？
How many soil orders are in the U.S. soil taxonomy?
美国农业部土壤分类系统把土壤归为约12个土纲（order），如新成土、淋溶土、氧化土和冻土等。它们依据成土过程、气候和母质等特征划分，是全球土壤多样性的框架。
The USDA soil taxonomy groups soils into about twelve orders, such as Entisols, Alfisols, Oxisols, and Gelisols. Based on soil-forming processes, climate, and parent material, they frame global soil diversity.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-08-23
来源 · Source
Tarbuck & Lutgens,《Earth Science》第14版,Pearson,2015
E. J. Tarbuck and F. K. Lutgens, Earth Science, 14th ed., Pearson, 2015
#土纲 #土壤分类 #USDA
什么是土壤团粒结构？
What is soil aggregate structure?
砂粒、粉粒和黏粒被黏土矿物与腐殖质胶结成疏松的小团聚体，就是团粒结构。团粒之间是大孔隙，管通气与排水；团粒内部是细毛管孔隙，管保水与保肥。两套孔隙兼备，水肥气热才能协调，因此它被视为肥沃土壤的标志。它和质地不是一回事：质地由颗粒粗细比例定下、几乎改不动，团粒结构却随有机质与耕作消长，大水漫灌或农机压实就能把它打散。
Sand, silt and clay cemented by clay minerals and humus into loose small clumps form aggregate structure. The gaps between clumps are large pores that aerate the soil and drain water, while the fine capillary pores inside each clump hold water and nutrients; with both pore sizes present, water, nutrients, air and heat stay balanced, which is why it counts as a mark of fertile soil. It is not the same thing as texture: texture is fixed by the proportion of particle sizes and hardly changes, whereas aggregate structure rises and falls with humus and tillage, and one heavy watering or machine compaction can break it apart.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-08-23
来源 · Source
Tarbuck & Lutgens,《Earth Science》第14版,Pearson,2015
E. J. Tarbuck and F. K. Lutgens, Earth Science, 14th ed., Pearson, 2015
#土壤 #团粒
什么是“砖红壤”（laterite）？它为何在热带广泛分布且常较贫瘠？
What is laterite, and why is it widespread in the tropics and often infertile?
砖红壤是热带高温多雨环境下强烈化学风化的产物：可溶的硅和碱金属被大量淋失，相对不溶的铁、铝氧化物富集，使土壤呈红黄色且厚重。由于养分随淋溶流失、又少有有机质积累，这类土壤往往酸性强、肥力低，需谨慎耕作。
Laterite forms under intense tropical chemical weathering: soluble silica and alkali metals are heavily leached away while relatively insoluble iron and aluminum oxides accumulate, giving the soil a reddish-yellow, hardened character. Because nutrients are washed out and organic matter scarce, such soils are often acidic and low in fertility, requiring careful management.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-11-03
来源 · Source
美国农业部自然资源保护局（USDA NRCS）；Brady & Weil《土壤的性质与特性》（The Nature and Properties of Soils）
USDA Natural Resources Conservation Service (NRCS); N.C. Brady & R.R. Weil, 'The Nature and Properties of Soils'
独立核验依据 · Independent verification: 核验依据 1 OPENLIBRARY 标识 /works/OL7296622W：The nature and properti
#砖红壤 #淋溶 #铁铝氧化物 #热带风化 #贫瘠
冻融作用如何塑造地貌？
How does freeze-thaw shape landforms?
水渗进岩石裂隙，结冰时体积膨胀约 9%，把缝壁向外顶；反复穿越冰点，裂口像楔子越凿越深，岩石被剥成棱角分明的碎块。融水带走细粒，石块沿坡面下爬，铺出石海、石河这类冰缘地貌。要紧的是「反复」：常年深冻里水早已冻实，几乎不再做功，作用最强的是冷暖来回过零的地带。它也有别于冰川磨蚀：一个原地敲碎岩石，一个靠移动的冰体切削。
Water seeps into cracks in rock, and freezing expands it by about 9%, pushing the walls apart; repeated cycles through the freezing point drive the wedge deeper and spall the rock into angular fragments. Meltwater washes the fine material away while blocks creep down the slope, laying out block fields and stone streams. What matters is the repetition: ground locked in a permanent deep freeze has already turned its water to ice and does little work, so the action is strongest where temperatures cross the freezing point again and again. It also differs from glacial abrasion—one shatters rock in place, the other cuts with ice that is moving.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-08-23
来源 · Source
Tarbuck & Lutgens,《Earth Science》第14版,Pearson,2015
E. J. Tarbuck and F. K. Lutgens, Earth Science, 14th ed., Pearson, 2015
#土壤 #冻融
什么是永冻层（permafrost）？
What is permafrost?
永冻层是连续两年以上保持冻结、含冰的地下土层，主要分布于高纬度和高海拔地区。气候变暖使它解冻，会释放甲烷并造成地面塌陷。
Permafrost is ground that stays frozen with ice for two or more consecutive years, mainly in high latitudes and altitudes. Warming thaws it, releasing methane and causing the ground to collapse.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-08-23
来源 · Source
Tarbuck & Lutgens,《Earth Science》第14版,Pearson,2015
E. J. Tarbuck and F. K. Lutgens, Earth Science, 14th ed., Pearson, 2015
#永冻层 #冻土 #甲烷
什么是壤土（loam）？
What is loam?
壤土是砂、粉砂和黏土比例较为均衡的土壤，既保水又透气、耕作性良好。它通常被认为是最适宜农业的土壤质地，肥力较高。
Loam is soil with a balanced mix of sand, silt, and clay, holding water yet draining well and easy to work. Often seen as the best agricultural texture, it is generally fertile and productive.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-08-23
来源 · Source
Tarbuck & Lutgens,《Earth Science》第14版,Pearson,2015
E. J. Tarbuck and F. K. Lutgens, Earth Science, 14th ed., Pearson, 2015
#壤土 #砂 #黏土
什么是土壤侵蚀？
What is soil erosion?
土壤侵蚀是表土被水、风或人为活动剥蚀搬运的过程，常因植被破坏和陡坡开垦而加剧。它会降低土地肥力、淤积河道，是严重的环境与农业问题。
Soil erosion is the removal and transport of topsoil by water, wind, or human activity, worsened by clearing vegetation and farming steep slopes. It lowers fertility, silts up rivers, and is a serious environmental and agricultural problem.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-08-23
来源 · Source
Tarbuck & Lutgens,《Earth Science》第14版,Pearson,2015
E. J. Tarbuck and F. K. Lutgens, Earth Science, 14th ed., Pearson, 2015
#土壤侵蚀 #水土流失 #植被
典型的土壤剖面从上到下主要分为哪些土层（soil horizons）？
What are the main soil horizons from top to bottom in a typical soil profile?
典型剖面自上而下包括：O层（地表有机落叶层）、A层（表土，富含有机质）、E层（淋溶层，矿物被冲刷流失）、B层（心土/淀积层，富集从上层淋下的物质）和C层（母质层，风化的基岩碎屑），最下常为R层基岩。美国农业部自然资源保护局（NRCS）的《土壤系统分类》采用此框架。
A typical profile, top to bottom, includes the O horizon (surface organic litter), A horizon (topsoil, rich in organic matter), E horizon (eluviated, leached of minerals), B horizon (subsoil, enriched by material leached from above), and C horizon (parent material of weathered rock fragments), underlain by R (bedrock). The USDA Natural Resources Conservation Service's Soil Taxonomy uses this framework.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-11-03
来源 · Source
美国农业部自然资源保护局（USDA NRCS）《土壤系统分类》（Soil Taxonomy）
USDA Natural Resources Conservation Service (NRCS), 'Soil Taxonomy'
独立核验依据 · Independent verification: 核验依据 1 OPENLIBRARY 标识 /works/OL10729610W：Soil taxonomy（首版 1975）
#土壤剖面 #O层 #A层 #B层 #C层
泥炭地为什么是重要的碳库？
Why are peatlands an important carbon store?
寒冷湿润处植物残体分解慢，碳在泥炭层里积累千年，全球泥炭地储存的碳比森林还多。
In cool wet places plant matter decays slowly and carbon builds up in peat for millennia; peatlands hold more carbon than forests worldwide.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23
来源 · Source
Tarbuck & Lutgens,《Earth Science》第14版,Pearson,2015
E. J. Tarbuck and F. K. Lutgens, Earth Science, 14th ed., Pearson, 2015
#泥炭地 #碳库
泥土是什么？
What is mud?
泥土是细碎的土壤和黏土混合水后的可塑状物，干了会变硬。
Mud is fine soil and clay mixed with water; it hardens when dry.
难度 入门 · 适合 小学低段(6-8)
CC BY 4.0 · 已核验 · Verified 2026-08-23
来源 · Source
Tarbuck & Lutgens,《Earth Science》第14版,Pearson,2015
E. J. Tarbuck and F. K. Lutgens, Earth Science, 14th ed., Pearson, 2015
#土壤 #泥土
土壤是什么？
What is soil?
土壤是岩石风化后的碎屑混上枯枝落叶变成的黑色疏松表层，植物靠它生长。
Soil is weathered rock mixed with decayed plants, a loose dark layer where plants grow.
难度 入门 · 适合 小学低段(6-8)
CC BY 4.0 · 已核验 · Verified 2026-08-23
来源 · Source
Tarbuck & Lutgens,《Earth Science》第14版,Pearson,2015
E. J. Tarbuck and F. K. Lutgens, Earth Science, 14th ed., Pearson, 2015
#土壤 #土壤