All of the greenhouse gases have a long persistence in the atmosphere resulting in an increasing impact on temperature with increasing concentration. If we didn’t have these gases in our atmosphere the earth would be a very cold place. Te presence of CO2
as one of the most abundant greenhouse
gases keeps the earth’s annual temperature around 60 degrees Fahrenheit (F) [15.5 degrees Centigrade (C)], but as we continue to increase CO2
levels the temperature will increase.
Another question asked is what can be done to reduce concentrations of greenhouse gases in the atmosphere. Reduction of N2
O emissions can be achieved through more
efficient use of nitrogen fertilizers by use of stabilized forms, reduced application rates, multiple small applications, and avoiding overwatering after application to create a saturated soil. Methane reduction is possible but management of turfgrass will not affect these levels because there is little methane emission from grasses.
Carbon dioxide reduction can be achieved through a variety of methods that involve enhancing the ability of the soil to store carbon. Established turfgrass is not disturbed with tillage and maintaining an actively growing turf could potentially be a carbon sink. Turfgrasses exhibit significant carbon sequestration during the first 25-30 years after establishment and several studies have reported that residential turfgrasses can store up to twice the amount of carbon as agricultural soils. Futhermore, one study of a typical residential landscape demonstrates that 90 percent of the carbon stored is captured by the lawn while only 9 percent is captured by trees and 1 percent by shrubs.
Carbon dioxide is beneficial to plants because increasing concentrations in the air enhances growth and improves water
use efficiency. Tere is a different response to increasing CO2 levels between cool-season grasses (primarily C3 and warm-season (primarily C4 metabolism). Te cool-
season grasses will show a large response to increased CO2 levels while warm-season grasses will show a slight to
moderate increase in growth. Te growth of turfgrass is more controlled by water and nutrient management than the changes in CO2
levels. One aspect of the increasing CO2 levels is the effect on water
use by plants. One benefit is that plants become more efficient in their use of water which means they produce more growth per amount of water used by the plant. Both cool- and warm-season grasses will have a greater water use efficiency with future increases in CO2
. What this means for turfgrass
management is that growth will be increased with no change in water use. Tis doesn’t mean that we can abandon water management because the crop will grow better, but we will see some changes in growth. Proper water management of turfgrass will certainly remain a top priority for production, establishment, and management of stands.
70 TPI Turf News July/August 2019 metabolism)
Temperature
Temperature has been increasing because of the rising greenhouse gas levels. Tis is one aspect of climate change that all scientists have agreed upon. However, the degree of this increase is still being debated. It is important to understand that when scientists talk about increases in temperature of 2 degrees F that is a global average and does not account for the variation within a country or within a region. For example, the southeastern U.S. has shown a cooling trend while the remainder of the continental U.S. shows a warming trend as shown in Figure 3.
However, of more interest to the turfgrass industry is the trend in changes in maximum and minimum temperatures. Te increases in temperature we are seeing are due to an increase in the minimum temperatures more than an increase in the maximum temperatures. If we look at the trends for Iowa, for example, there is no change in the 30-year normal for the maximum temperatures in the past 30 years while the minimum temperatures have increased by 0.5 degrees F. In these trends, we see the summer maximum temperatures actually decreasing while the winter maximum temperatures are increasing. Minimum temperatures are increasing throughout the year, which means we don’t cool down as much at night. Tis affects the growth rate of plants and also has implications for the development of diseases because of warmer temperatures and higher humidity. Tis is one aspect that turfgrass managers need to pay attention to because of the potential problems with management of turfgrass diseases.
Increasing temperatures have been further evident in two ways. Longer growing seasons have already begun to occur and a shift in the plant hardiness zones northward in the U.S. was evident in the latest compilation of these maps. Te plant hardiness zones have shifted northward over the past 20 years by nearly 60 miles and implies that the boundary between cool- and warm-season grasses will become less defined. However, this increase in temperatures doesn’t mean that there will not be extremes in seasonal temperatures with cold winters (similar to what we experienced in 2019) or extremely hot summer temperatures. In fact, future climate projections favor more high temperature events than cold events.
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