Q FE 430 Discussion #3: potential evapotranspiration and water deficit submit on Canvas by Wednesday of Week 3 at 11:59pm Pacific Time respond to one of your classmate’s posts by the following Sunday at 11:59 pm Pacific Time *your response to your classmates should be substantial and further the discussion of the processes in the soil water budget and plant water availability. Do you agree or disagree with your classmates? Why? Objectives: 1. Read information from a time series graph about variations in water inputs and water deficit. Grading Rubric: Criteria Points Possible Description of graph and explanation of 15 plant water availability throughout the year Response to classmate 5 Total points for discussion 20 Background Information and Resources: Helpful Resources: • This document • Instructor Overview Week #3 The graph attached shows the soil water budget. The soil water budget, using the annual arrival of precipita-tion as “income” and the annual demands of potential evapotranspiration (PET) as potential “expenditures,” shows the availability of soil water at all times of the year (Fig. 1). Note that, for most areas, soil water re-charge occurs during the water surplus of winter, when precipitation is greater than PET. By late spring, PET increases greatly and usually exceeds precipitation, giving a deficit period. This is not a problem as long as the soil can store enough water in a “savings account” to carry plants through the deficit period, shown in the bud-gets as “soil water utilization.” But, if the deficit is too great for the savings account, soil water is reduced to the wilting point, and vegetational stress begins. For most areas with crops and other mesophytic vegetation, this means irrigation. Question: Select one of the locations in the series of graphs below and write a detailed explanation of the changes in soil water and what this means in terms of water availability for vegetaion. How do you think water availability determines plant species composition? Does your chosen area require irrigation? Responses should be about 200-300 words. I chose Anchorage Alaska. We see that there is no data from November thru March. This is most likely due to the colder temperatures during these months and the ground being frozen due to its northern location and massive amounts of snow. The reason we see a giant spike in April is due to all of the snowmelt runoff causing a massive influx of water running into the watershed. We see that precipitation rises in the month's May to August, peaking in mid-August. After August we see a decrease all the way down at the end of October. We see a rise in Potential evapotranspiration (PET) starting in April, peaking in July, then declining to the end of October. Due to the time of year, we observe that Potential evapotranspiration is higher than precipitation during the months of May to August while it is the opposite during August to the end of October. With this information and observing the graph, we can see that in early April due to the massive snowmelt there is a soil water deficit and vegetation stress. Starting in late April we start to see a surplus of the soil moisture deficit that continues to grow up until mid-August. Late August down to the end of October we see a negative/declining surplus of soil moisture. Lastly, we see that at the beginning of June to mid-August we start to see the deficit and Vegetation appear. Alaska has a lot of moisture typically due to its northern location and high snowpack. There are very limited times of year in which plants are able to grow due to the freezing temperatures. Yet during these growing months, there seems to be available water for certain vegetation compositions to thrive.