Range Management Laboratory. Lab 4 Range Biomass Determination

Transcription

1 Range Management Laboratory Lab 4 Range Biomass Determination Instructional Objectives: 1. Review problem on line intercept data 2. Continue review of range vegetation analysis A.Diversity B.Vigor C.Quality D.Biomass 3. Biomass determination A. Double sampling B. Clip & weigh 4. Using quadrats, determine species density, biomass, and diversity Review problem: Line intercept Mammoth Land Company of Denver, Colorado is interested in purchasing a parcel of rangeland in the area of Dry Gulch, Utah. They have contracted the Green Earth Consulting Firm to assess the state of vegetation on the property in question. As chief scientist for Honeybee Consulting, you have been given the task of fulfilling the contract. Your first step is to conduct a line-intercept survey of the area using 20 replications (i.e. you measure the vegetation along 20 line intercepts of random location) of a 20 m intercept with 2 m intervals. Data from the first intercept is summarized in the table below. Based on this data compute the % cover, relative cover, relative density, and frequency and fill in the data table provided with your answers. Range Lab 4 1 of 15

2 NAME: DATE: 09/30/96 LOCATION: Dry Gulch, Utah SOIL TYPE: Aridsol (Sandy loam) VEGETATION TYPE: Saltdesert shrubland INTERCEPT NUMBER: 1 TOTAL LENGTH OF LINE INTERCEPT: SPECIES INTERCEPTS - LIST EACH ONE SEPARATELY (CM) SUM OF INTERCEPTS NUMBER OF INTERVALS CONTAINING SPECIES 1. Shadscale saltbush Range Lab 4 2 of 15

3 2. Indian Ricegrass Bottlebrush squirreltail galleta grass Canadian thistle downy brome rubber rabbitbrush SUM OF ALL INTERCEPTS: Range Lab 4 3 of 15

4 SPECIES % COVER % RELATIVE COVER RELATIVE DENSITY FREQUENCY VIGOR In discussing the state of range vegetation, you may occasionally hear people use the term "plant vigor". From a common sense point of view, you may correctly deduce that plant vigor may be defined as the overall health of a plant. In the space provided below, list physical and physiological characteristics of plants that would enable you to quantify plant vigor on a range site: Range Lab 4 4 of 15

5 What environmental and management factors will generally reduce plant vigor, at least temporarily? FORAGE QUALITY Rangelands play a critical role in the nutrition of both domestic livestock and wildlife. Measurements of biomass are important, but don't give the complete picture of the potential for rangeland to support animal life. Forage quality must be considered as well. Define Forage Quality How do we determine forage quality? Range Lab 4 5 of 15

6 List 3 plant specific factors that are important in determining forage quality: What are 3 specific methods for evaluating forage quality? What does NIRS stand for? Range Lab 4 6 of 15

7 Draw a graph that shows the general relationship between plant maturity and forage quality: BIOMASS To determine the ability of rangeland to support animal life, one of the most common measurements is biomass. There is some differences in definitions given for biomass. For our purposes we will use the definitions given in A Glossary of Terms Used in Range Management published by the Society of Range Management (1989 edition). Define biomass Define phytomass Range Lab 4 7 of 15

8 How do we measure phytomass? In practical range management, when we refer to biomass or phytomass, we are often referring to the total above ground weight of plant material. Weight is often best expressed as oven-dry weight, since moisture content of plants varies by species and due to environmental conditions. This means that plant tissue collected in the field is dried in a 90 C drying oven until there is no further change in weight. Perhaps the most common means for determining phytomass is clipping and weighing. In this procedure, a suitable size plot or quadrat is selected. Then, using either hand clippers (small plots) or mowers (larger plots), the vegetation is clipped and the entire harvest is weighed on a field scale. Subsamples of the whole harvest may be taken into the lab to be dried. Dry matter content is determined and the fresh weights of plots are converted into dry weights. To help you see how this works, determine the oven dry weight of the plots below, using the data provided. Plot #1 (2 m X 5 m) Plot #2 (10 m X 4 m) Fresh weight (kg) of clipped material Subsample fresh weight (g) Subsample dry weight (g) Range Lab 4 8 of 15

9 % dry matter plot phytomass (oven dry weight basis in kg) Phytomass of range site (kg/ha) Phytomass of range site (lbs/acre) Once the oven dry weight of a plot has been determined, the phytomass for the larger area under study is estimated by multiplying the plot yield by an appropriate conversion factor to give the desired units, such as kg/ha or lbs/acre. [Hint: the conversion factor for converting kg/ha to lbs/acre is Also note that 1 ha=10,000 m 2. ] Using the plot data you calculate, compute the yield in kg/ha and lbs/acre for the range sites represented by the plots. Forage production on rangelands varies widely with both time and location. Based on data presented on pages in our class text, what is the range of phytomass we might expect on western U.S. rangelands on an annual basis? Range Lab 4 9 of 15

10 Estimating Phytomass by Double Sampling 1. Select the range site to be studied 2. Select a random location for the quadrat within the range site Note: In a full scale study, for statistical purposes, you would set up at least 10 plots. For our purposes, we will do only one. 3. Select an appropriate quadrat size and shape for the vegetation present. We will use 1 m 2 4. Inventory the species present in the quadrat and record. 5. Develop a visual unit of plant mass that you can conveniently count. Your instructor will provide you with diagrams to help you do this. 6. Clip and weigh the visual unit for each species and record in the table provided. These are called weight-units. 7. Visually estimate the number of weight units for each species in the quadrat and record in the table provided. 8. To estimate the weight of each species in the quadrat, multiply the weight of the weight unit times the number of units you visually estimate are contained in the quadrat. Record this in the table provided. 9. Total the data for all species to obtain an estimate of total plot phytomass 10. Multiply the phytomass of the plot by an appropriate factor to convert this weight to kg/ha and lbs/acre 11. The procedure outlined in steps 1-11 is a visual estimation of plot phytomass. The second part of the double-sampling technique is a procedure in which you will clip and weight plots. By taking this second Range Lab 4 10 of 15

11 sample (hence the name double sampling) you are able to see how 'good' your estimates are. In fact, you will use the data obtained in this step to compute a correction factor. The correction factor will be used to adjust your visual estimates. In theory then, you get the benefits of visual estimation (speed) as well as some of the accuracy of the direct clipping and weighing procedure. The double sampling technique is used because in some cases you will need to estimate phytomass on so many plots that it's just not practical to clip and weigh each plot. 12. On the same quadrat you visually estimated, clip each species and place in paper bags. [Note: Normally in double-sampling, we would clip one plot for each 7-10 visually estimated plots]. Obtain fresh weight for each species. Depending on the size of the sample, place the entire sample or a 13. When dry, obtain dry weight and determine % dry matter for each species. Use this data to determine dry weight of each species. 14. After obtaining dry weights of the clipped species in step 13, you need to calculate the correction factor for each species. The correction factor, in theory, will correct for any bias you exhibited in your visual sampling. To do this, you need to multiply future visual estimates of phytomass for that species by the following correction factor: Correction factor = clipped weight for a given species Estimated weight for a given species 15. Compute the correction factor for each species. Multiply the correction factor by the estimated weight for each species. This is the corrected plot weight estimate. Record this data in the table provided. 16. Select a randomly located quadrat within your assigned plot. Visually estimate the weight of each species and record the data in the table provided. Then multiply these weights by the correction factors you previously determined to obtain the corrected weights. Record this data in the table provided. 17. Select a small random sample of fresh vegetation ( a mixture of species acceptable for our purposes) and place in a labeled bag. Range Lab 4 11 of 15

12 Weigh this sample and record the weight in the table provided. Place this in a drying oven until the tissue is dry. Re-weigh the sample and compute %dry matter, where % dry matter = (dry wt sample/ fresh wt sample) X Multiply the corrected plot phytomass by the %dry matter data. Convert g/plot to more standard units of kg dry matter /ha. Plot Number = Plot Size = Species Wt Unit (g) Quadrat Data Summary Quadrat 1 Number of Units Estimated Phytomass (g fresh wt) Clipped Correction Phytomass Factor (g) Range Lab 4 12 of 15

13 Total Corrected Phytomass = Plot Number = Plot Size = Species Wt Unit (g) Quadrat Data Summary Quadrat 2 Number of Units Estimated Phytomass (g fresh wt) Clipped Correction Phytomass Factor (g) Range Lab 4 13 of 15

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15 Total Corrected Phytomass = Final Calculations - Unit Conversions For the final part of the procedure, you will need to convert your data into the standard units of kg/ha. To do this you will first compute the % dry matter for the vegetation. To do this follow steps described previously in the lab procedure. Please record your data in the table below and have your lab checked and signed by your instructor. Subsample fresh weight (g) Subsample dry weight (g) % dry matter Corrected plot phytomass (g/plot) X % dry matter Corrected plot phytomass (kg/ha) By my signature I affirm that I have completed this laboratory, calculated and recorded the results above, and have checked the results with the lab instructor. Students Signature/Date Instructors Signature/Date Range Lab 4 15 of 15