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 functional unit of nature where living organisms (biotic components) interact with each other and with their non-living environment (abiotic components) through a series of flows of energy and cycling of matter. Ecosystems range from tiny ponds to vast biomes, and their boundaries are often defined for practical or analytical purposes rather than by rigid natural limits.

生态系统是自然界的功能性单元，其中生物（生物成分）通过一系列能量流动和物质循环，相互之间并与其非生物环境（非生物成分）相互作用。生态系统的范围从小池塘到广阔的生物群系不等，其边界往往是为了实际或分析目的而划定，而非由严格的自然界限决定。

1. Introduction to Ecosystems | 生态系统概述

An ecosystem includes all organisms in a given area, plus the physical environment in which they live. Key properties include energy flow, nutrient cycling, trophic structure, and dynamic stability. Ecologists study systems at several scales: organisms, populations, communities, ecosystems, landscapes, and the whole biosphere.

生态系统包括特定区域内所有生物体及其生存的物理环境。关键属性包括能量流动、养分循环、营养结构和动态稳定性。生态学家在多个尺度上研究系统：个体、种群、群落、生态系统、景观乃至整个生物圈。

The concept was popularised by Arthur Tansley in 1935, who stressed that organisms and their environment form one physical system. Modern ecosystem ecology emphasises the interconnectedness of humans and nature, as human activities are now significant drivers of ecosystem change.

该概念由阿瑟·坦斯利于1935年推广，他强调生物体与其环境构成一个统一的物理系统。现代生态系统生态学强调人与自然相互联系，因为人类活动现在已成为生态系统变化的重要驱动力。

2. Biotic and Abiotic Components | 生物与非生物成分

Biotic components are categorised by their ecological roles. Producers (autotrophs), such as green plants, algae, and some bacteria, photosynthesise to convert light energy into chemical energy. Consumers (heterotrophs) feed on other organisms; they include herbivores, carnivores, omnivores, and parasites. Decomposers, mainly fungi and bacteria, break down dead organic matter and release nutrients for reuse by producers.

生物成分按其生态角色分类。生产者（自养生物），如绿色植物、藻类和某些细菌，通过光合作用将光能转化为化学能。消费者（异养生物）以其他生物为食，包括草食动物、肉食动物、杂食动物和寄生虫。分解者主要是真菌和细菌，它们分解死亡有机物质并释放养分供生产者再次利用。

Abiotic components include light, temperature, water, soil type, pH, salinity, and nutrient availability. These factors directly influence the distribution and productivity of organisms. For example, light drives photosynthesis, while soil pH controls the availability of mineral ions to plants.

非生物成分包括光照、温度、水分、土壤类型、pH值、盐度和养分可用性。这些因素直接影响生物体的分布和生产力。例如，光照驱动光合作用，而土壤pH值控制植物对矿物离子的可利用性。

3. Energy Flow in Ecosystems | 生态系统中的能量流

Energy enters most ecosystems as solar radiation. Plants capture a small fraction of it through photosynthesis and convert it into chemical energy stored in organic molecules. This energy then flows through the food web as organisms are consumed. Energy flow is unidirectional, unlike nutrients which cycle; it is ultimately lost as heat through metabolic processes.

能量以太阳辐射的形式进入多数生态系统。植物通过光合作用捕获其中一小部分，并将其转化为储存在有机分子中的化学能。随后能量随着生物被取食而流经食物网。能量流动是单向的，不同于循环利用的养分；它最终通过代谢过程以热能形式散失。

The gross primary productivity (GPP) is the total rate of photosynthesis by producers, while net primary productivity (NPP) is the energy remaining after plant respiration (R). NPP represents the energy available to consumers and decomposers.

总初级生产力（GPP）是生产者进行光合作用的总速率，而净初级生产力（NPP）是扣除植物呼吸消耗（R）后剩余的能量。NPP代表可供消费者和分解者利用的能量。

NPP = GPP − R

At each trophic level, only about 10% of energy is transferred to the next level; the rest is used for respiration, digestion, excretion, and is lost as heat. This explains why food chains are usually short and why predators are rare compared with prey.

在每个营养级，只有约10%的能量转移到下一级；其余能量用于呼吸、消化、排泄并以热能散失。这解释了为什么食物链通常较短，以及为什么捕食者相对于猎物数量稀少。

4. Food Chains and Food Webs | 食物链与食物网

A food chain is a linear sequence of organisms through which energy and nutrients pass. A simple terrestrial food chain is: grass → rabbit → fox. Each stage is called a trophic level. In reality, organisms rarely consume only one type of food, so food chains interconnect into complex food webs that better represent ecosystem feeding relationships.

食物链是能量和养分通过生物体传递的线性序列。一个简单的陆地食物链是：草 → 兔 → 狐。每个阶段称为营养级。实际上，生物很少只取食一种食物，因此食物链相互连接成复杂的食物网，更能代表生态系统的取食关系。

Food webs help ecologists understand ecosystem stability. If one species declines, predators may switch to alternative prey, buffering the system against collapse. However, invasive species or habitat fragmentation can disrupt these connections, leading to unforeseen cascades.

食物网有助于生态学家理解生态系统稳定性。如果某个物种数量减少，捕食者可能转而取食替代猎物，从而缓冲系统免于崩溃。然而，入侵物种或栖息地破碎化可能破坏这些联系，导致难以预见的级联效应。

5. Trophic Levels and Ecological Pyramids | 营养级与生态金字塔

Ecological pyramids illustrate the distribution of energy, biomass, or numbers among trophic levels. Pyramids of number show the count of organisms; pyramids of biomass show the dry weight of organisms; pyramids of energy show the energy flowing through each level over time.

生态金字塔展示能量、生物量或个体数量在营养级之间的分布。数量金字塔显示生物个体数；生物量金字塔显示生物干重；能量金字塔显示单位时间内流经各营养级的能量。

类型	形状	说明
数量金字塔	通常下宽上尖，可能倒置	一棵大树支持大量昆虫时可能倒置
生物量金字塔	通常下宽上尖	海洋中浮游植物生物量可能低于其消费者，但生产力极高
能量金字塔	始终下宽上尖	能量逐级减少，不可倒置

Energy pyramids are always upright because energy is lost at each transfer. Biomass pyramids can occasionally be inverted in aquatic systems where producers reproduce rapidly but have low standing biomass at any moment.

能量金字塔始终直立，因为能量在每次传递中都会损耗。生物量金字塔在水生系统中偶尔倒置，因为生产者繁殖迅速但某一时刻的现存生物量较低。

6. Nutrient Cycling: The Carbon Cycle | 养分循环：碳循环

Carbon is essential for all organic molecules. The main reservoirs include the atmosphere (CO₂), oceans, fossil fuels, soils, and biomass. Key processes are photosynthesis, respiration, decomposition, and combustion. Carbon moves from the atmosphere into plants via photosynthesis, then to animals via feeding, and returns to the atmosphere through respiration and decomposition.

碳对所有有机分子都必不可少。主要储库包括大气（CO₂）、海洋、化石燃料、土壤和生物量。关键过程包括光合作用、呼吸、分解和燃烧。碳通过光合作用从大气进入植物，再通过取食进入动物体内，并经过呼吸和分解返回大气。

Human activities, especially the burning of fossil fuels and deforestation, have disrupted the carbon cycle, increasing atmospheric CO₂ concentrations. This intensifies the greenhouse effect and leads to global warming, with feedbacks such as melting permafrost releasing even more carbon.

人类活动，特别是化石燃料燃烧和毁林，扰乱了碳循环，导致大气CO₂浓度升高。这加剧了温室效应并导致全球变暖，同时产生反馈效应，例如永久冻土融化释放更多碳。

7. Nutrient Cycling: The Nitrogen Cycle | 养分循环：氮循环

Nitrogen is a key component of proteins and nucleic acids. Although the atmosphere contains about 78% nitrogen as N₂, most organisms cannot use this form directly. Nitrogen fixation converts N₂ into ammonia (NH₃) or nitrate (NO₃⁻), performed by bacteria such as Rhizobium and free-living soil bacteria, as well as by lightning.

氮是蛋白质和核酸的关键成分。虽然大气中约78%是氮气（N₂），但大多数生物无法直接利用这种形式。固氮作用将N₂转化为氨（NH₃）或硝酸盐（NO₃⁻），由根瘤菌和土壤中自由生活的细菌以及闪电完成。

Nitrification is the conversion of ammonia to nitrite (NO₂⁻) and then to nitrate (NO₃⁻) by nitrifying bacteria. Plants absorb nitrate and ammonium, incorporating nitrogen into organic matter. Denitrifying bacteria, under anaerobic conditions, convert nitrate back to N₂ gas, completing the cycle.

硝化作用是硝化细菌将氨转化为亚硝酸盐（NO₂⁻）再转化为硝酸盐（NO₃⁻）的过程。植物吸收硝酸盐和铵盐，将氮合成到有机物中。反硝化细菌在厌氧条件下将硝酸盐还原为N₂气体，从而完成循环。

Humans have greatly increased the supply of reactive nitrogen through fertiliser production and fossil fuel combustion, causing eutrophication in freshwaters and marine dead zones, as well as contributing to acid rain.

人类通过化肥生产和化石燃料燃烧大大增加了活性氮的供应，导致淡水富营养化、海洋死区以及酸雨等问题。

8. Nutrient Cycling: The Phosphorus Cycle | 养分循环：磷循环

Phosphorus is a component of ATP, DNA, and cell membranes. Unlike carbon and nitrogen, phosphorus has no significant gaseous phase in its cycle. It is mainly present as phosphate ions (PO₄³⁻) in rocks and soils. Weathering releases phosphate into soil, where plants absorb it. Animals obtain phosphorus by eating plants, and decomposers return it to the soil.

磷是ATP、DNA和细胞膜的组成成分。与碳和氮不同，磷循环没有显著的气相阶段。它主要以磷酸根离子（PO₄³⁻）形式存在于岩石和土壤中。风化作用将磷酸盐释放到土壤中，植物将其吸收。动物通过取食植物获得磷，分解者将磷返还土壤。

The phosphorus cycle is slow and largely local, as phosphate is not easily transferred through the atmosphere. Modern agriculture relies on phosphate from mined rocks, but reserves are finite, and runoff from farms causes algal blooms and eutrophication in lakes and coastal waters.

磷循环缓慢且在空间上较局限，因为磷酸盐不易通过大气转移。现代农业依赖开采岩石中的磷酸盐，但储量有限，而农田径流导致湖泊和沿海水域藻类爆发和富营养化。

9. Succession | 演替

Ecological succession is the directional change in community composition over time. Primary succession begins on newly exposed or formed surfaces where no soil exists, such as bare rock after a volcanic eruption or glacial retreat. Pioneer species, like lichens and mosses, colonise first, weathering rock and forming a thin soil layer.

生态演替是群落组成随时间的方向性变化。初级演替始于没有土壤的新暴露表面，如火山喷发或冰川退缩后的裸岩。地衣和苔藓等先锋物种首先定殖，通过风化岩石并形成薄薄的土壤层。

Secondary succession occurs where an ecosystem has been disturbed but soil remains, such as after a forest fire or abandoned farmland. Because soil and a seed bank are already present, secondary succession is faster than primary succession.

次级演替发生在生态系统受到干扰但土壤仍然保留的地方，如森林火灾后或废弃农田。由于土壤和种子库已经存在，次级演替比初级演替更快。

Succession may be autotrophic (increasing biomass through photosynthesis) or heterotrophic (dominated by decomposition, as in a contaminated lake). A stable climax community, such as mature temperate forest, represents the final stage under prevailing climatic conditions.

演替可以是自养的（通过光合作用增加生物量）或异养的（以分解为主，如受污染的湖泊）。稳定的顶级群落，如成熟的温带森林，代表在现有气候条件下的最终阶段。

10. Factors Affecting Ecological Succession | 影响演替的因素

Climate is the most important factor ultimately determining the type of climax community. Temperature and precipitation influence which species can survive and reproduce. Soil properties, including texture, pH, and nutrient status, favour certain species over others during different successional stages.

气候是最终决定顶级群落类型的最重要因素。温度和降水影响哪些物种能够生存和繁殖。土壤性质，包括质地、pH值和养分状况，在演替的不同阶段使某些物种比其他物种更具优势。

Species availability and dispersal ability determine how quickly colonisers arrive. Human disturbances, such as fire suppression or grazing, can arrest succession. Moreover, biological interactions such as competition, predation, and facilitation shape the pathway and speed of change.

物种可用性和扩散能力决定了拓殖者到达的速度。人类干扰，如抑制火源或过度放牧，可扭转演替进程。此外，竞争、捕食和促进等生物相互作用也塑造了演替的路径和速度。

11. Human Impacts on Ecosystems | 人类对生态系统的影响

Agriculture replaces diverse natural ecosystems with monocultures, reducing biodiversity and altering nutrient and water cycles. Urbanisation fragments habitats, isolating populations and disrupting gene flow. Pollution from industries and transport introduces toxins, excess nutrients, and greenhouse gases into ecosystems.

农业用单一作物替代多样的自然生态系统，减少生物多样性并改变养分和水循环。城市化使栖息地破碎化，隔离种群并破坏基因流。工业和交通污染向生态系统引入毒素、过量养分和温室气体。

Invasive species, often introduced accidentally or intentionally, can outcompete native species and destabilise food webs. Overexploitation of resources, including overfishing and deforestation, removes keystone species and triggers ecosystem collapse. Climate change compounds all these effects by shifting habitat ranges and phenology.

入侵物种通常被无意或有意引入，可能竞争过本土物种并破坏食物网稳定。资源过度开发，包括过度捕捞和毁林，去除关键种并引发生态系统崩溃。气候变化通过改变栖息地范围和物候期，加剧上述所有影响。

12. Ecosystem Management and Conservation | 生态系统管理与保护

Sustainable ecosystem management aims to meet human needs while maintaining ecological processes and biodiversity. Protected areas, such as national parks and marine reserves, conserve critical habitats and species. Large-scale strategies include wildlife corridors that reconnect fragmented landscapes, and rewilding projects that restore natural disturbance regimes.

可持续生态系统管理旨在满足人类需求的同时维持生态过程和生物多样性。保护区，如国家公园和海洋保护区，保护关键栖息地和物种。大规模策略包括连接破碎化景观的野生动物廊道，以及恢复自然干扰机制的再野化项目。

Effective management requires an understanding of ecosystem structure and processes, monitoring of indicators, and involvement of local communities. Restoration ecology applies scientific principles to restore degraded ecosystems, recognising that ecosystems are dynamic and that human interventions must work with, not against, natural processes.

有效的管理需要理解生态系统结构和过程、监测指标，并让当地社区参与。恢复生态学应用科学原理恢复退化生态系统，认识到生态系统是动态的，人工干预必须顺应而非对抗自然过程。

Success is measured not only by ecological health but also by the capacity of ecosystems to provide services such as clean water, pollination, and climate regulation. Equitable governance is essential to balance conservation goals with social and economic needs.

成功不仅以生态健康衡量，还取决于生态系统提供服务的能力，如清洁水源、授粉和气候调节。公平的治理对于平衡保护目标与社会经济需求至关重要。

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