Dynamic equilibrium and the water carbon cycles

Question 1

What is dynamic equilibrium?

Answer 1

Dynamic equilibrium refers to the state of natural systems where there is a balance between inputs, throughputs, outputs, and stores of energy and materials.

Question 2

What are the characteristics of natural systems in dynamic equilibrium?

Answer 2

Natural systems in dynamic equilibrium have continuous inputs, throughputs, outputs, and variable stores of energy and materials. In the short term, the inputs, outputs, and stores of water or carbon may fluctuate from year to year.

Question 3

How do flows and stores maintain balance in the long term?

Answer 3

In the long term, flows and stores in natural systems usually maintain a balance, allowing the system to retain its stability. Negative feedback loops within the systems help restore balance.

Question 4

What is an example of negative feedback in a drainage basin?

Answer 4

In a drainage basin, unusually heavy rainfall can increase the amount of water stored in aquifers, raising the water table and increasing flow from springs until the water table returns to normal levels. This is an example of a negative feedback loop that restores balance.

Question 5

How does burning fossil fuels affect the carbon cycle?

Answer 5

Burning fossil fuels increases atmospheric CO2 (carbon dioxide) levels.

Question 6

What is the negative feedback response to increased atmospheric CO2 levels?

Answer 6

The negative feedback response to increased atmospheric CO2 levels is the stimulation of photosynthesis. Photosynthesis helps remove excess CO2 from the atmosphere and restore equilibrium in the carbon cycle.

Question 7

What is urbanisation?

Answer 7

Urbanisation is the conversion of land use from rural to urban, where farmland and woodland are replaced by housing, offices, factories, and roads.

Question 8

What are the characteristics of artificial surfaces in urban areas?

Answer 8

Artificial surfaces in urban areas, such as concrete, brick, or tarmac, are largely impermeable, allowing little or no infiltration and providing minimal water storage capacity to buffer run-off.

Question 9

How do drainage systems in urban areas impact water flow?

Answer 9

Urban areas have drainage systems designed to remove surface water rapidly, resulting in a high proportion of water from precipitation flowing quickly into streams and rivers, leading to a rapid rise in water levels.

Question 10

What is the impact of urban development on floodplains?

Answer 10

Urban development on floodplains reduces water storage capacity in drainage basins, increasing river flow and flood risks.

Question 11

What are the transpiration rates for Sitka spruce in the Pennines?

Answer 11

The transpiration rates for Sitka spruce in the Pennines are around 350 mm/year of rainfall equivalent.

Question 12

What changes occur to the local water cycle during clear felling for timber harvesting?

Answer 12

Clear felling for timber harvesting creates sudden but temporary changes to the local water cycle. It increases run-off, reduces evapotranspiration, and increases stream discharge.

Question 13

How does land use change from farmland, moorland, and heath to forestry affect carbon stores?

Answer 13

Changing land use from farmland, moorland, and heath to forestry increases carbon stores. In a typical UK plantation, mature forest trees contain, on average, 170-200 tonnes C/ha. This is ten times higher than grassland and 20 times higher than heathland.

Question 14

Where is a significant carbon pool found in the ecosystem?

Answer 14

The soil represents an even larger carbon pool. In England, measurements of forest soil carbon are around 500 tonnes C/ha.

Question 15

How do forest trees impact atmospheric CO2 levels?

Answer 15

Forest trees extract CO2 from the atmosphere and sequester it for hundreds of years.

Question 16

For how long do forest trees act as an active carbon sink after planting?

Answer 16

Forest trees act as an active carbon sink (absorbing more carbon than they release) for the first 100 years or so after planting.

Question 17

What are the factors that balance the carbon captured by forest trees?

Answer 17

The amount of carbon captured by forest trees is balanced by inputs of litter to the soil, the release of CO2 in respiration, and the activities of soil decomposers.

Question 18

What is the typical rotation period for forestry plantations?

Answer 18

Forestry plantations usually have a rotation period of 80-100 years. After this time, the trees are felled, and reforestation begins anew.

Question 19

What is the rate of interception for preferred plantation species in the UK?

Answer 19

Preferred plantation species in the UK, such as conifers, have high rates of interception. For Sitka spruce, interception rates can be as high as 60 percent.

Question 20

What is the effect of conifer plantations on water yield in upland catchments?

Answer 20

Conifer plantations in upland catchments often reduce water yield for public supply. They result in reduced run-off, stream discharge, and altered drainage basin hydrology. Streams draining plantations typically have relatively long lag times, low peak flows, and low total discharge.