Designing Experiments in Ecosystems | 生态系统实验设计

📚 Designing Experiments in Ecosystems | 生态系统实验设计

Ecological experiments form the core of practical biology, enabling us to test hypotheses about how organisms interact with each other and their environment. This article covers key experimental designs for the 6.5 Ecosystems topic, from sampling techniques to data analysis, with a focus on reliable and ethical methodology.

生态学实验是生物学实践的核心，使我们能够检验关于生物如何相互作用以及如何与环境互动的假说。本文涵盖 6.5 生态系统专题的关键实验设计，从取样技术到数据分析，重点关注可靠且符合伦理的方法。

1. Introduction to Ecological Experiments | 生态学实验简介

An ecological experiment typically begins with a clear aim, such as determining how a particular abiotic factor influences species distribution or comparing biodiversity between two habitats. Fieldwork must be carefully planned to control variables and collect representative data.

生态学实验通常始于明确的目标，例如确定某个非生物因素如何影响物种分布，或比较两个生境间的生物多样性。野外工作必须仔细规划，以控制变量并收集有代表性的数据。

Both field studies and laboratory simulations can be used. Field experiments provide high ecological validity, whereas lab simulations allow for tighter control of variables like temperature and predator density.

野外研究和实验室模拟均可使用。野外实验提供较高的生态效度，而实验室模拟则可以更严格地控制温度和捕食者密度等变量。

2. Sampling Techniques for Populations | 种群取样技术

To avoid bias, random sampling should be used when investigating plant species or slow-moving animals. This can be achieved by generating random coordinates for quadrat placement using a random number table or app.

为避免偏差，在调查植物物种或移动缓慢的动物时应使用随机取样。这可以通过使用随机数表或应用程序生成样方放置的随机坐标来实现。

For community-level studies, stratified sampling ensures all sub-habitats are represented by dividing the area into distinct zones and sampling each proportionally.

对于群落水平的研究，分层取样通过将区域划分为不同地带并按比例对每个地带取样，确保所有子生境都得到体现。

Sample size matters: a larger number of quadrats or trapping events increases the reliability of estimates like population density and species richness.

样本量很重要：较多的样方或诱捕次数可提高种群密度和物种丰富度等估计值的可靠性。

3. Using Quadrats for Plant Distribution | 使用样方调查植物分布

Quadrats (typically 0.25 m² or 1 m²) are placed either randomly or along a transect. Percentage cover or species frequency is recorded. Percentage cover is particularly useful for species that are difficult to count as individuals, such as grasses or mosses.

样方（通常为 0.25 m² 或 1 m²）随机放置或沿样线放置。记录百分比覆盖度或物种频度。对于难以按个体计数的物种（如禾草或苔藓），百分比覆盖度尤其有用。

To estimate percentage cover, a gridded quadrat with 100 subdivisions allows direct visual estimation, reducing subjectivity when practised with the same observer. Replicates (e.g., 10–20 quadrats) are needed to calculate a mean.

为了估算百分比覆盖度，使用带有 100 个小格的网格样方可以直接进行目视估算，同一观察者练习后可降低主观性。需要重复（例如 10–20 个样方）以计算平均值。

The ACFOR scale (Abundant, Common, Frequent, Occasional, Rare) provides a semi-quantitative alternative when precise counts are not feasible.

当精确计数不可行时，ACFOR 尺度（丰富、常见、频繁、偶见、稀有）提供了一种半定量的替代方法。

4. Transect Studies | 样线调查

A transect line is a tape or rope laid across a habitat to investigate zonation or the effect of an environmental gradient. Quadrats are placed at regular intervals (interrupted belt transect) or continuously (belt transect) to record species composition.

样线是一条横贯生境的卷尺或绳索，用于研究成带现象或环境梯度的影响。以固定间隔（间断带状样线）或连续（带状样线）放置样方，记录物种组成。

This technique is ideal for studying changes along a shoreline, across a wooded area to open grassland, or up an altitudinal gradient. Environmental variables like light intensity, soil moisture, and pH are measured at each sampling point to identify correlations.

该技术非常适合研究沿海岸线、从林地到开阔草地或沿海拔梯度的变化。在每个取样点测量光照强度、土壤湿度和 pH 等环境变量，以识别相关性。

5. Mark-Release-Recapture for Animals | 标记重捕法调查动物

For motile animals, the Lincoln index is used. A sample (n₁) is captured, marked harmlessly, and released. After mixing, a second sample (n₂) is captured, and the number of marked individuals (m₂) is recorded. The population size N is estimated as:

对于能运动的动物，使用林肯指数。捕获首个样本 (n₁)，进行无害标记后释放。待其混合后，捕获第二个样本 (n₂)，记录其中已标记个体数 (m₂)。种群大小 N 估算公式为：

N = (n₁ × n₂) ÷ m₂

Assumptions include: marks are not lost, marked individuals mix equally, no migration or significant births/deaths between samples, and marking does not affect survival or recapture probability. Violating these assumptions skews the estimate.

假设包括：标记不会脱落，已标记个体均匀混合，取样期间无迁移或显著的出生/死亡，且标记不影响生存或重捕概率。违反这些假设会使估算值出现偏差。

6. Investigating Abiotic Factors | 非生物因素调查

Abiotic factors such as temperature, light intensity, wind speed, soil moisture, pH, and oxygen concentration can be measured with portable meters or sensors. Consistent methodology is vital: light sensors should be held at the same height and orientation at each point.

温度、光照强度、风速、土壤湿度、pH 和氧浓度等非生物因素可使用便携式仪表或传感器测量。方法的一致性至关重要：在每个测量点，光传感器应保持相同的高度和朝向。

For aquatic habitats, dissolved oxygen probes and turbidity tubes allow quantitative comparisons. In soil studies, oven-drying a known mass of soil and reweighing gives percentage water content, while a pH meter or universal indicator yields soil pH.

对于水生境，溶解氧探头和浊度管可进行定量比较。在土壤研究中，将已知质量的土壤烘干后重新称重可得到含水量百分比，而 pH 计或通用指示剂可获知土壤 pH。

Data loggers are especially useful for continuous monitoring over 24 hours or across seasons, revealing daily fluctuations in temperature or humidity that influence organism activity.

数据记录仪对于 24 小时或跨季节的连续监测尤为有用，可以揭示影响生物活动的温度或湿度日波动。

7. Simulating Predator-Prey Dynamics | 捕食者-猎物动态模拟

A classic laboratory simulation involves a ‘habitat’ tray and coloured paper discs representing prey, with forceps or a hand serving as the predator. Prey items of different colours are scattered on a contrasting background, and the predator collects as many as possible in a timed interval.

一个经典的实验室模拟使用一个“生境”托盘和代表猎物的彩色纸片，镊子或手充当捕食者。不同颜色的猎物撒在与背景形成对比的表面上，捕食者在一定时间内尽可能多地收集。

This models natural selection: better-camouflaged ‘prey’ survive to the next ‘generation’ by replenishing their numbers proportionally. Students can plot predator and prey population oscillations, demonstrating the cyclic patterns predicted by the Lotka-Volterra models.

这模拟了自然选择：伪装较好的“猎物”通过按比例补充其数量存活到下一个“世代”。学生可以绘制捕食者和猎物种群振荡图，展示 Lotka-Volterra 模型预测的周期性模式。

Refinements include adding structural refuges or varying prey reproduction rates to mimic real ecosystem complexity.

改良方法包括添加结构性避难所或改变猎物繁殖速率，以模拟真实生态系统的复杂性。

8. Measuring Energy Flow and Productivity | 能量流动与生产力测定

Gross primary productivity (GPP) and net primary productivity (NPP) can be estimated indirectly using the light-and-dark-bottle method for aquatic producers, or by measuring changes in dry biomass over time in terrestrial quadrats.

总初级生产力 (GPP) 和净初级生产力 (NPP) 可以通过水生生产者的黑白瓶法间接估算，或通过测量陆地样方内干生物量随时间的变化来估算。

Energy content per gram of dry biomass is determined using a bomb calorimeter, which combusts the sample and measures the heat released. This reveals how much energy is stored at each trophic level and why food chains are short.

每克干生物量的能量含量使用弹式量热计测定，该仪器燃烧样品并测量释放的热量。这揭示了每个营养级储存了多少能量，以及为何食物链较短。

Students can construct pyramids of energy by multiplying the biomass of organisms at each level by their energy density. Efficiency between levels is typically around 10%, aligning with the Lindeman efficiency rule.

学生可以将每个营养级的生物量乘以其能量密度，构建能量金字塔。营养级之间的效率通常约为 10%，符合林德曼效率法则。

9. Food Web and Trophic Level Experiments | 食物网与营养级实验

Building a food web begins with identifying species in the sampled area and determining trophic relationships through direct observation, gut content analysis, or stable isotope analysis. For school labs, literature values and simple dissection can reveal feeding links.

构建食物网始于识别取样区域中的物种，并通过直接观察、肠道内容物分析或稳定同位素分析确定营养关系。在学校实验室中，文献值和简单解剖可揭示取食关系。

Detritivores and decomposers can be studied using choice chambers or bait lamina strips to investigate preferences for different leaf litter conditions (moist/dry, light/dark). This links decomposition rates to abiotic factors.

腐食者和分解者可以使用选择箱或诱饵薄片条进行研究，以调查它们对不同落叶条件（潮湿/干燥、光亮/黑暗）的偏好。这会将分解速率与非生物因素联系起来。

Bioaccumulation of toxins can be modelled by passing a tracer (e.g., coloured water) through a series of containers representing trophic levels, showing how concentrations magnify at higher levels.

毒素的生物积累可以通过让示踪剂（如带颜色的水）依次流经代表营养级的一系列容器来模拟，显示浓度如何在较高营养级中放大。

10. Ethical Considerations in Fieldwork | 野外工作的伦理考虑

All ecological fieldwork must minimise disturbance to habitats and organisms. Quadrats should be placed gently, and destructive sampling (e.g., uprooting plants) should be replaced with non-destructive methods like photography or percentage cover estimates whenever possible.

所有生态学野外工作必须尽量减少对生境和生物的干扰。应轻柔放置样方，并尽可能用摄影或百分比覆盖度估算等非破坏性方法替代破坏性取样（如拔起植物）。

For animal studies, capture techniques must avoid injury, and release should occur at the original capture site. Observed distress requires immediate termination of the experiment.

对于动物研究，捕获技术必须避免伤害，并应在原捕获地点释放。若观察到动物应激，应立即终止实验。

Bringing organisms into the lab (e.g., woodlice for choice chambers) demands providing appropriate conditions and returning them to their habitat promptly after the investigation.

将生物带入实验室（例如用于选择箱的潮虫）需要提供适宜的条件，并在调查结束后立即将其送回原栖息地。

11. Data Analysis and Statistical Tests | 数据分析与统计检验

Quantitative data are often tested for significant differences or correlations. For comparing species abundance between two sites with normally distributed data, an unpaired t-test is appropriate. For non-parametric data, the Mann-Whitney U test can be employed.

定量数据通常需检验显著性差异或相关性。对于比较两个地点物种多度且数据正态分布的情况，可使用非配对 t 检验。对于非参数数据，可使用曼-惠特尼 U 检验。

To assess the relationship between an abiotic factor and species distribution, Spearman’s rank correlation (rₛ) is useful, particularly when data are monotonic but not linear. A significance value (p < 0.05) is typically adopted.

为了评估非生物因素与物种分布之间的关系，斯皮尔曼秩相关系数 (rₛ) 很有用，尤其是当数据呈单调但非线性的关系时。通常采用显著性水平 p < 0.05。

Chi-squared (χ²) tests can analyse the association between two categorical variables, such as the distribution of a species in shaded versus unshaded areas against an expected ratio.

卡方 (χ²) 检验可以分析两个分类变量之间的关联，例如物种在阴蔽与无阴蔽区域的分布是否符合预期比例。

Simpson’s Diversity Index (D = 1 – Σ(n/N)²) calculates biodiversity, taking into account both richness and evenness. A high value indicates high diversity.

辛普森多样性指数 (D = 1 – Σ(n/N)²) 计算生物多样性，同时考虑了丰富度和均匀度。数值越高表示多样性越高。

12. Common Pitfalls and Improvements | 常见错误与改进

One major pitfall is sampling bias, such as placing quadrats in areas that ‘look interesting’. This can be mitigated by strict randomisation and defining coordinates before fieldwork.

一个主要陷阱是取样偏差，例如将样方放置在“看起来有趣”的区域。这可以通过严格随机化和在野外工作前定义坐标来减轻。

Small sample sizes lead to unreliable means and wider confidence intervals. Pilot studies help determine the minimum sample size needed to detect a meaningful effect.

小样本量会导致平均值不可靠和置信区间较宽。试点研究有助于确定检测有意义效应所需的最小样本量。

In mark-recapture studies, if marks make animals more visible to predators, the recapture rate drops, overestimating population size. Using biocompatible, non-toxic marks and observing post-release behaviour can identify this issue.

在标记重捕研究中，如果标记使动物更容易被捕食者发现，重捕率会下降，从而高估种群规模。使用生物相容、无毒的标记并观察释放后的行为，可以识别这一问题。

Finally, failing to calibrate instruments (e.g., pH meters or light sensors) can introduce systematic errors, so all devices should be checked against standards before use.

最后，未能校准仪器（例如 pH 计或光传感器）会引入系统误差，因此所有设备在使用前都应用标准品校验。

Published by TutorHao | Biology Revision Series | aleveler.com

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