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Chapter 4 The Terrestrial Environment. 陸地的環境. 4.1 Life on Land Imposes Unique Constraints. 陸地上的生命承受獨特的限制. 陸地環境對生命的限制. 乾燥效應。（ desiccation ） 重力作用。 (gravity) 環境因子的變動大小（例如：溫度）。. The giant kelp: Macrocystis pyrifera. A redwood wood: Sequoia sempervirens.
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4.1 Life on Land Imposes Unique Constraints 陸地上的生命承受獨特的限制
陸地環境對生命的限制 • 乾燥效應。（desiccation） • 重力作用。(gravity) • 環境因子的變動大小（例如：溫度）。
4.2 Plant Cover Influences the Vertical Distribution of Light 植物的覆蓋影響光線的垂直分佈
Leaf area index (LAI)葉面積指數 • 定義: 葉的表面積除以植物在地表的投影面積 (m2 leaf area/ m2 ground area) . • A leaf area index of 3 would mean that there are 3 m2 of leaf area over 1 m2 of ground area.
Levels of photosynthetically active radiation (PAR), within and above a yellow-poplar stand over a year.
4.3 Soil Is the Foundation Upon Which All Terrestrial Life Depends 土壤是所有陸地生命依賴的基礎
Soil definition（土壤的定義） • Soil is a natural product formed and synthesized by the weathering of rocks and the action of living organisms. • （土壤是岩石的風化作用與生物活動形成的天然產物）
Soil definition （土壤的定義） • Soil is a collection of natural bodies of earth, composed of mineral and organic matter and capable of supporting plant growth. • 土壤是地表聚積的自然體，由無機物及有機物組成，能支持植物的生長。
4.4 The Formation of Soil Begins with Weathering 土壤的形成開始於風化作用
Weathering （風化作用） • Mechanical weathering（物理風化作用）: breaks down rock and minerals into smaller particles.（透過物理作用將岩石或礦物變成小顆粒） • Chemical weathering（化學風化作用）:
4.5 Soil Formation Involves Five Interrelated Factors 土壤的形成包含五個相關的因子
土壤形成的五個因子 • Parental material （母岩） • Climate （氣候） • Biotic factors （生物因子） • Topography （地形） • Time （時間）
4.6 Soils Have Certain Distinguishing Physical Characteristics 土壤具有某些可區分的物理性質
Soil texture（土壤特徵（組成）） • Soil texture is the proportion of different-sized soil particles. • Gravel（砂礫）: larger than 2.0 mm. • Sand（沙）: from 0.05 to 2.0 mm. • Silt（泥沙）: from 0.002 to 0.05 mm. • Clay（黏土）: less than 0.002 mm.
Soil texture（土壤特徵） • Gravel is not part of the fine fraction of soil. • A soil texture is the percentage (by weight) of sand, silt, and clay. • Clay controls the most important properties of soils, including its water holding capacity, and the exchange of ions between soil particles and soil solution.
A soil texture chart, which shows the percentages of clay, silt, and sand in the basic soil texture classes.
4.7 The Soil Body Has Horizontal Layers, or Horizons 土壤有水平的層狀結構
4.8 Moisture-Holding Capacity Is an Essential Feature of Soils 水分保持能力是土壤的重要特徵
Moisture-holding capacity of soil • Saturated（飽和）: the amount of water exceeds what the pore space of soil can hold. • Field capacity（田間容量）: Water fills all the pore spaces of soil and is hold there by internal capillary forces.（水分以毛細作用充滿土壤中所有的孔隙） • Capillary water（毛細水）: Water held between soil particles by capillary forces.（水分以毛細作用為土壤所保留）
Moisture-holding capacity of soil • Wilting point (WP): The moisture level of soil decreases to a point at which plants can no longer extract water. • 枯萎點：土壤中的水分減少到植物無法從中獲得水分，此土壤之含水量稱為枯萎點。
Moisture-holding capacity of soil • Available water capacity (AWC): The amount of water retained by the soil between field capacity and wilting point. • 可利用的水容量：
Water content of three different soils at wilting point (WP), field capacity (FC), and saturation.
4.9 Ion Exchange Capacity Is Important to Soil Fertility 離子交換容量對土壤肥沃度很重要
Ion（離子） • Cation（陽離子）: with positive charge(s)（帶正電荷的離子） • Anion（陰離子）: with negative charge(s)（帶負電荷的離子）
Ion exchange（離子交換） • Ion exchange capacity（離子交換容量）: The total number of charged sites on soil particles within a volume of soil.（一定體積土壤內的帶電荷離子位置總數目） • Colloids（膠狀體）：土壤中帶負電荷的離子 • Cation exchange capacity（陽離子交換容量）
Ion exchange • The lyotropic series : • Al3+＞H+＞Ca2+＞Mg2+＞K+ = NH4+＞Na+ • Hydrogen ions (H+) effect: Al3+
Soil acidity • Typically, soils range from pH 3 (extremely acid) to pH 9 (strongly alkaline).（土壤的酸鹼值一般從pH 3-9） • Soils just over pH 7 (neutral) are considered basic, and those of pH 5.6 or below are acid.
4.10 Basic Soil Formation Processes Produce Different Soils 基礎的土壤形成過程中產生不同的土壤
