Ecosystems and Their Processes | 生态系统及其过程

📚 Ecosystems and Their Processes | 生态系统及其过程

An ecosystem is a dynamic complex of living organisms — plants, animals, and microorganisms — interacting with their non-living environment, including soil, water, air, and sunlight, as a functional unit. Geography at the senior secondary level requires an understanding of the structure of ecosystems, the flows of energy and matter through them, and the ways in which human activity alters these natural systems.

生态系统是指在一定空间范围内，植物、动物和微生物等生物成分与土壤、水、空气和阳光等非生物环境通过物质循环和能量流动而相互作用、相互依存所形成的一个动态功能单位。高中地理阶段要求理解生态系统的结构、能量流动和物质循环的过程，以及人类活动对这些自然系统的影响方式。

1. Defining the Ecosystem | 生态系统的定义与尺度

The concept of the ecosystem was popularised by the British ecologist Arthur Tansley in 1935. He argued that organisms and their physical environment should be viewed as one integrated system, rather than studied in isolation. This holistic view remains central to modern ecology and biogeography.

生态系统这一概念由英国生态学家阿瑟·坦斯利于1935年提出。他认为生物有机体与其物理环境应被视为一个不可分割的整体系统，而非孤立地加以研究。这种整体性视角至今仍是现代生态学与生物地理学的核心思想。

Ecosystems exist at a wide range of spatial scales. A single pond, a decaying log, a forest, or the entire biosphere can each be treated as an ecosystem. The boundary of an ecosystem is often drawn for the convenience of study, although in reality ecosystems grade into one another through transitional zones known as ecotones.

生态系统存在于多种空间尺度上。一个池塘、一根腐木、一片森林乃至整个生物圈都可以被视作一个生态系统。生态系统的边界往往是为研究方便而划定的，但实际上，生态系统之间通过过渡带逐渐交错，这种过渡区域称为群落交错区。

2. Components of an Ecosystem | 生态系统的组成成分

All ecosystems comprise two fundamental components: abiotic (non-living) factors and biotic (living) factors. The abiotic framework supplies the physical template upon which life develops, while the biotic community actively transforms energy and materials.

所有生态系统都由两大类基本成分构成：非生物成分（非生命的物理和化学因素）与生物成分（有生命的有机体）。非生物框架为生命的繁衍提供了物理基底，而生物群落则积极地转化能量与物质。

Abiotic components include solar radiation, temperature, precipitation, wind, soil type, pH, salinity, and the availability of nutrients such as nitrogen and phosphorus. These factors determine which species can survive in a given location and how productive the ecosystem is.

非生物成分包括太阳辐射、温度、降水、风、土壤类型、酸碱度、盐度以及氮、磷等养分的可利用性。这些因素决定了某一地区能够生存的物种类型，并影响着生态系统生产力的高低。

Biotic components are classified by trophic role. Producers, typically green plants and algae, fix solar energy through photosynthesis. Consumers, including herbivores and carnivores, obtain energy by feeding on other organisms. Decomposers such as fungi and bacteria break down dead organic matter and release nutrients back into the soil or water.

生物成分按照营养功能划分。生产者主要为绿色植物和藻类，通过光合作用固定太阳能。消费者包括草食动物和肉食动物，通过取食其他生物获取能量。分解者如真菌和细菌则将死亡的有机体分解，并把养分释放回土壤或水体之中。

Component \| 成分	Examples \| 举例	Role in the Ecosystem \| 在生态系统中的角色
Producer 生产者	Oak tree, grass, phytoplankton	Convert light energy into chemical energy
Consumer 消费者	Deer, fox, owl	Obtain energy by eating other organisms
Decomposer 分解者	Bacteria, earthworms, fungi	Break down dead matter, recycle nutrients

3. Energy Flow through Food Chains and Webs | 能量在食物链与食物网中的流动

Energy enters most ecosystems as sunlight. Photosynthetic organisms convert this radiant energy into chemical energy stored in organic molecules. This energy then passes from one trophic level to the next as organisms are consumed.

能量以阳光的形式进入大多数生态系统。光合生物将这种辐射能转化为储存在有机分子中的化学能。随后，能量随着生物之间的取食关系，从一个营养级传递到下一个营养级。

A food chain is a linear sequence showing how energy transfers from producers through a series of consumers, for example: grass → rabbit → fox → decomposer. In reality, organisms rarely feed on a single species, so food chains interconnect to form complex food webs.

食物链是展示能量如何从生产者经一系列消费者传递的线性序列，例如：草 → 兔 → 狐狸 → 分解者。在现实中，生物很少只取食单一物种，因此食物链相互交织，形成复杂的食物网。

Energy transfer between trophic levels is highly inefficient. Typically, only 10% of the energy stored at one trophic level is converted into biomass at the next level; the remaining 90% is lost as heat through respiration, or remains in undigested material and waste products. This is known as the 10% law.

能量在营养级之间的传递效率极低。通常，一个营养级储存的能量中只有约10%能够转化为下一营养级的生物量；其余约90%通过呼吸作用以热量的形式散失，或保留在未消化的食物残渣和排泄物中。这就是著名的“百分之十定律”。

Energy transfer efficiency ≈ 10% per trophic level

能量传递效率 ≈ 每个营养级 10%

4. Ecological Pyramids | 生态金字塔

Ecological pyramids are graphical representations that illustrate the relationship between trophic levels in an ecosystem. Three types are commonly used: pyramids of numbers, pyramids of biomass, and pyramids of energy.

生态金字塔是以图形方式表达生态系统中营养级之间关系的模型。常用的有三类：数量金字塔、生物量金字塔和能量金字塔。

Pyramid of numbers shows the number of individual organisms at each trophic level. It is often upright, but inverted pyramids occur when producers are large single trees supporting many herbivores.

数量金字塔表示每个营养级上生物个体的数量。它通常是正金字塔形，但当生产者是高大的单一树木、支撑着许多草食动物时，可能出现倒金字塔形。
Pyramid of biomass reflects the total dry mass of living tissue at each level. This pyramid is more meaningful than the pyramid of numbers because it compensates for size differences between organisms.

生物量金字塔反映每一营养级上生物组织的总干重。该金字塔比数量金字塔更有意义，因为它弥补了生物个体大小差异带来的影响。
Pyramid of energy always appears upright because energy is always lost at each transfer. It measures the rate of energy flow per unit area per unit time, expressed in J m⁻² yr⁻¹ or kJ m⁻² yr⁻¹.

能量金字塔永远呈正立形态，因为能量在每一次传递中都会损耗。它度量单位面积单位时间内能量流动的速率，单位常用 J·m⁻²·年⁻¹ 或 kJ·m⁻²·年⁻¹ 表示。

5. Nutrient Cycles: Carbon and Nitrogen | 养分循环：碳循环与氮循环

Unlike energy, which flows one-way through an ecosystem and is eventually lost as heat, matter is cycled. Nutrients such as carbon, nitrogen, phosphorus, and water move repeatedly between the biotic and abiotic compartments of the ecosystem.

与单向流动并以热量形式散失的能量不同，物质在生态系统中是循环使用的。碳、氮、磷和水等养分反复地在生物组分与非生物组分之间迁移转化。

The carbon cycle involves the exchange of carbon between the atmosphere, oceans, biosphere, and geosphere. Photosynthesis removes CO₂ from the atmosphere and fixes it into organic compounds. Respiration by plants, animals, and microbes returns CO₂ to the atmosphere. Combustion of fossil fuels and deforestation have accelerated the release of stored carbon, intensifying the greenhouse effect.

碳循环涉及大气、海洋、生物圈和岩石圈之间碳的交换。光合作用将大气中的CO₂固定为有机化合物；植物、动物和微生物的呼吸作用又把CO₂释放回大气。化石燃料燃烧和毁林加速了储存在地球各库中的碳的释放，加剧了温室效应。

The nitrogen cycle is essential for the synthesis of proteins and nucleic acids. Nitrogen gas (N₂) in the atmosphere cannot be used directly by most organisms. Nitrogen-fixing bacteria, such as Rhizobium in the root nodules of legumes, convert N₂ into ammonia (NH₃). Nitrifying bacteria then oxidise ammonia into nitrites (NO₂⁻) and nitrates (NO₃⁻), which plants can absorb. Denitrifying bacteria return nitrogen to the atmosphere as N₂ gas.

氮循环对于蛋白质和核酸的合成至关重要。大气中的氮气（N₂）不能被大多数生物直接利用。固氮菌，如豆科植物根系中的根瘤菌，将N₂转化为氨（NH₃）。随后亚硝化细菌和硝化细菌将氨氧化为亚硝酸盐（NO₂⁻）和硝酸盐（NO₃⁻），植物方可吸收利用。反硝化细菌则将氮以N₂气体的形式返回大气。

6. The Hydrological Cycle in Ecosystems | 生态系统中的水循环

The hydrological cycle links every ecosystem to the global climate system. Water evaporates from oceans and freshwater surfaces, transpires from vegetation, condenses to form clouds, and falls as precipitation. Once on or beneath the ground, water is stored temporarily in lakes, soil moisture, groundwater, and snow packs before eventually returning to the sea.

水循环将每一个生态系统与全球气候系统紧密相连。水从海洋和水面蒸发，经植被蒸腾，凝结成云，再以降水形式降落。降落到地面或渗入地下的水，暂时储存在湖泊、土壤水、地下水和积雪之中，最终再回归海洋。

Vegetation plays a critical role in regulating water flows. Forest canopies intercept rainfall, reducing surface runoff and soil erosion. Root systems enhance infiltration and groundwater recharge. When forests are cleared, the hydrological balance is disrupted, increasing flood risk and reducing dry-season river flow.

植被在调节水流方面发挥着关键作用。森林冠层截留降水，减少地表径流和水土流失。根系系统增强了水的下渗和地下水补给。当森林被砍伐时，水文平衡遭到破坏，洪水风险增加，旱季河流流量减小。

7. Ecological Succession: Primary and Secondary | 生态演替：原生演替与次生演替

Ecological succession is the directional and predictable change in the species composition of a community over time. Succession occurs because the activities of existing species modify the environment, making it more suitable for new species to colonise.

生态演替是指群落物种组成随时间发生定向的、可预测的变化过程。演替发生的原因在于现有物种的活动改变了环境条件，使环境更适合新物种的定居和繁衍。

Primary succession begins on surfaces that have never been colonised by organisms, such as bare rock, lava flows, or newly exposed glacial till. Pioneer species such as lichens and mosses break down rock surfaces and begin to form thin soils. Over hundreds or thousands of years, herbaceous plants, shrubs, and eventually trees replace one another until a climax community is established.

原生演替开始于从未被生物定居过的表面，如裸岩、熔岩流或新暴露的冰碛物。地衣和苔藓等先锋物种分解岩石表面，开始形成薄层土壤。经过数百年乃至数千年，草本植物、灌木和乔木依次更替，直至形成顶极群落。

Secondary succession occurs in areas where an existing community has been disturbed but the soil remains intact. Examples include abandoned farmland, areas after a forest fire, or land cleared by human activity. Because soil and seeds or roots are already present, secondary succession proceeds more rapidly than primary succession.

次生演替发生在原有群落遭到干扰、但土壤层仍然保留的地区。例如废弃农田、森林火灾后的迹地，或人类活动清理过的土地。由于土壤和种子库或残存根系仍然存在，次生演替的速度比原生演替快得多。

8. Major Terrestrial and Aquatic Ecosystems | 主要的陆地与水生生态系统

Tropical rainforests, found near the equator, are the most biodiverse terrestrial ecosystems. High temperatures and abundant rainfall enable year-round photosynthesis and rapid nutrient cycling. However, most nutrients are stored in the biomass rather than in the soil, making the ecosystem highly vulnerable to deforestation.

热带雨林位于赤道附近，是陆地生态系统中生物多样性最高的类型。高温和充沛的降水使得全年都可进行光合作用，养分循环迅速。然而，大部分养分储存在生物量中而非土壤中，这使得该生态系统在面临毁林时极为脆弱。

Coral reefs are often called the “rainforests of the sea.” They support extraordinary biodiversity within warm, shallow, nutrient-poor waters. Reef-building corals live in symbiosis with zooxanthellae algae, which supply up to 90% of the coral’s energy through photosynthesis. Rising sea temperatures cause the algae to be expelled, leading to coral bleaching and reef degradation.

珊瑚礁常被称为“海底热带雨林”。在温暖、浅层且养分贫乏的水域中，珊瑚礁支撑了极高的生物多样性。造礁珊瑚与虫黄藻共生，后者通过光合作用为珊瑚提供高达90%的能量。海水温度升高会导致藻类被排出体外，引发珊瑚白化与珊瑚礁退化。

Temperate grasslands are dominated by herbaceous vegetation with few trees, shaped by moderate rainfall, seasonal drought, and periodic fire. Deep, fertile soils have made many grasslands prime agricultural regions, yet large-scale conversion to croplands has caused severe loss of native biodiversity.

温带草原以草本植被为主导，乔木稀少，其形态受中等降水、季节性干旱和周期性野火共同塑造。深厚而肥沃的土壤使许多草原成为主要的农业区，但大规模开垦为耕地也导致原生生物多样性严重丧失。

9. Human Impacts on Ecosystems and Sustainable Management | 人类对生态系统的影响与可持续管理

Human activities alter ecosystem structure and function at every scale. Habitat destruction, overexploitation, pollution, introduction of invasive species, and climate change together drive biodiversity loss and disrupt ecological processes such as nutrient cycling and energy flow.

人类活动在每一种尺度上改变着生态系统的结构和功能。栖息地破坏、过度开发、污染、外来物种入侵和气候变化共同驱动着生物多样性的丧失，并干扰养分循环和能量流动等生态过程。

Sustainable ecosystem management seeks to balance human needs with the long-term health of natural systems. Strategies include establishing protected areas, restoring degraded habitats, practising sustainable forestry and fisheries, controlling invasive species, and reducing greenhouse gas emissions. Modern approaches also involve ecosystem-based adaptation, which uses natural systems to help human communities cope with climate change.

生态系统可持续管理旨在平衡人类需求与自然系统的长期健康。主要策略包括建立保护区、修复退化栖息地、实行可持续的林业和渔业、控制入侵物种以及减少温室气体排放。现代方法还涉及基于生态系统的适应策略，即利用自然系统帮助人类社会应对气候变化。

Sustainability = meeting present needs without compromising the ability of future generations to meet their own needs

可持续性 = 满足当代人的需求，而不损害后代人满足其自身需求的能力

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Ecosystems and Their Processes | 生态系统及其过程