Heat Summation – Definition & Detailed Explanation – Phenology Glossary

What is Heat Summation?

Heat summation, also known as growing degree days (GDD), is a measure of the cumulative amount of heat that has accumulated over a period of time. It is commonly used in phenology, the study of the timing of biological events in relation to seasonal changes. Heat summation is important for predicting when certain events, such as plant flowering or insect emergence, will occur based on temperature conditions.

How is Heat Summation calculated?

Heat summation is typically calculated by summing the daily average temperatures above a certain base temperature over a specified period. The base temperature is the minimum temperature required for a particular biological process to occur. For example, the base temperature for corn development is around 50°F.

To calculate heat summation, the daily average temperature is subtracted from the base temperature, and the resulting value is added to the cumulative total for each day. This process is repeated for each day in the period of interest, resulting in a total heat summation value.

Why is Heat Summation important in phenology?

Heat summation is crucial in phenology because many biological processes, such as plant growth and insect development, are directly influenced by temperature. By tracking heat summation, researchers can predict when these events will occur and better understand the impact of climate change on phenological patterns.

What are the implications of Heat Summation on plant and animal behavior?

Heat summation plays a significant role in determining the timing of important events in the life cycles of plants and animals. For example, the timing of flowering in plants, migration in birds, and emergence of insects are all influenced by heat summation. Changes in heat summation due to climate change can disrupt these critical events, leading to mismatches in food availability, pollination, and predator-prey interactions.

How does Heat Summation vary in different climates?

Heat summation can vary significantly in different climates due to differences in temperature patterns. Regions with warmer temperatures and longer growing seasons will accumulate heat more quickly than cooler regions with shorter growing seasons. This variation in heat summation can impact the timing of phenological events, such as the onset of spring growth or the arrival of migratory birds.

What are some examples of Heat Summation influencing phenological events?

One example of heat summation influencing phenological events is the timing of cherry blossom flowering in Japan. The date of cherry blossom flowering is closely tied to heat summation, with warmer temperatures leading to earlier blooming. Changes in heat summation due to climate change have caused cherry blossoms to bloom earlier in recent years, disrupting traditional festivals and cultural events.

Another example is the emergence of caterpillars in temperate forests. Caterpillars rely on heat summation to time their emergence with the budding of leaves, which provides them with food. Changes in heat summation can lead to mismatches between caterpillar emergence and leaf growth, impacting the survival of both the caterpillars and the trees.

Overall, heat summation is a valuable tool for understanding and predicting the timing of biological events in response to changing temperature conditions. By tracking heat summation, researchers can gain insights into the impacts of climate change on phenological patterns and inform conservation efforts to protect vulnerable species.