Evaluation of Ecosystem Services Provided by the Coteau Rangeland of North Dakota

Guojie Wang, Xuejun Dong, Bob Patton, Anne Nyren and Paul Nyren, Central Grasslands Research Extension Center

The term ecosystem services refers to the benefits from the natural systems that support human life, like soil, water, and climate. The ecosystem services of the Coteau rangeland are essential to supporting the lives and livelihoods of those who live in this area. However, it is difficult to quantify the value of ecosystem services. They are valuable to different people in different ways. How ecosystem services are managed also depends upon the goals of those who manage them. In this report, we use several indexes, including aboveground biomass production, soil water content, and livestock gain/acre, to help quantify the value of the ecosystem services of this region with different management goals in mind.

An ecosystem is a dynamic complex of plant, animal, and microorganism communities and the nonliving environment interacting as a functional unit. Ecosystem services are the benefits people obtain from ecosystems. These include provisioning services, such as food, water, timber, fuel and fiber; regulating services that affect climate, floods, disease, waste, and water quality; cultural services that provide recreational, aesthetic, and spiritual benefits; and supporting services such as soil formation, photosynthesis, biodiversity, and nutrient cycling (Stokstad, 2005).

Ecosystem services are the natural systems that support and fulfill human life. They are important for maintaining the Earth’s life-support system. According to Costanza et al. (1997), the current economic value of ecosystem services provided by grasslands and other biomes in the world is estimated to be an average of $33 trillion per year. This estimate causes scientists, governments, and members of the general public to seriously evaluate and preserve ecosystem services. Many global and regional assessments have been published (e.g., Millennium Ecosystem Assessment, http://www.millenniumassessment.org/).

The grassland is a very important biome occupying almost 25% of the earth’s land area. Because the number of people living on grasslands is increasing, these areas face many problems, like soil erosion and desertification. How to use grasslands to provide the services that humans need, while also allowing the land to maintain itself, is a challenge for us.

The grazing intensity trial at CGREC was started in 1989 as a completely randomized design with five treatments: light, moderate, heavy and extreme grazing intensities and an ungrazed control. Each grazing treatment was replicated three times on pastures of about 30 acres each. The pastures are stocked in mid-to-late May with the goal of leaving 65%, 50%, 35%, and 20% of an average year’s above-ground biomass remaining at the end of the grazing season on the light, moderate, heavy and extreme grazing treatments, respectively.

Yearling heifers were stratified by weight and allotted to twelve different pastures with four different grazing treatments. The heifers were weighed in May before they went on pasture and again when they were removed in each year of the study.

Soil water was measured with a neutron moisture meter around the 1^st and 15^th of each month when the temperature was above 32°F throughout the soil profile. There are 118 sample periods between 1989 and 2004 with 10 to 15 sample periods during each year.

At the beginning of each grazing season from 1989 to 2004, five plots were caged and two uncaged plots paired with each caged plot on each sample site. Herbage clipped from inside the caged plots at the peak of the growing season provides an estimate of peak biomass.

Soil samples for nitrogen and carbon were collected in August 2005. Five samples were taken inside of ungrazed exclosures and five in adjacent grazed areas outside the exclosures. Grazed treatments that were sampled were light, heavy and extreme on overflow range sites and moderate and extreme on silty range sites. Samples where sent to the Soil Testing Lab at NDSU for analysis of the total carbon, total nitrogen, and organic carbon. These samples were analyzed with a Primacs TOC Analyzer and a Tecator Kjeltec 1030 Autoanalyzer and passed through a 60-mesh screen. Total carbon was determined by ignition at 1000°C and inorganic carbon was determined by evolution after the addition of 20% phosphoric acid at room temperature. Organic carbon was determined by subtracting inorganic carbon from total carbon. Total nitrogen was determined by the Kjeldahl Method.

Although grassland provides very valuable ecosystem services, many of the specific services are difficult to quantify. For example, it is difficult to determine the value of biodiversity and soil formation. To better measure the value of the ecosystem services provided by the grasslands of the Missouri Coteau, we selected the following indexes, which represent key functions in the grassland ecosystem and are easy to measure directly:

• Aboveground biomass links many ecosystem functions, such as carbon cycle, nitrogen cycle, and water cycle. It is an important index to show that the entire ecosystem provides services.

• Where there is no water, there is no life. Hence, water content in the soil is an important index, especially in the grassland, where water is the first limiting factor.

• Carbon and nitrogen content in the soil: Along with water, carbon and nitrogen are the main elements of life.

• Gain/acre: The beef production per acre, shows the economic outcome of grazing on the grassland.

Using these indexes, we tried to determine the value of the ecosystem services for different use areas. We determined the differences in these parameters between different stocking rates using analysis of variance (ANOVA) with means separation using Fishers least significant difference procedure at the P=0.05 level (SAS 9.1 software). There were significant differences for aboveground biomass, soil water, and cattle gain/acre between different treatments both on the silty and overflow sites (Tables 1 and 2). However, there were no significant differences for number of species between different treatments on the overflow site. Total carbon and total nitrogen also showed no significant difference. However, organic carbon was greater on moderate grazing than on ungrazed on the silty range site (Table 3).

Table 1. Average aboveground plant biomass production, soil water, number of plant species, and livestock gain/acre on overflow range sites.
Grazing Intensity	Above-ground plant biomass production (lb/a)	Percent total soil water by weight (0-6 inch depth)	Number of plant species	Livestock gain/acre (lb)
Ungrazed	3097 a*	38.58 c	57a	--
Lightly grazed	3673 a	46.50 a	58a	2.71 b
Moderately grazed	3626 a	41.76 b	60a	3.17 b
Heavily grazed	3644 a	39.90 c	60a	11.88 a
Extremely grazed	2476 b	37.87 c	60a	13.27 a
Mean (Avg)	3304	40.92	59	6.21
Standard Deviation	521	3.45	1.41	5.96
*Means in the same column followed by the same letter are not significantly different; P≤0.05)

Table 2. Average aboveground plant biomass production, soil water, number of plant species, and livestock gain/acre on silty range sites.
Grazing Intensity	Above- ground plant biomass production (lb/a)	Percent total soil water by weight (0-6 inch depth)	Number of plant species	Livestock gain/acre (lb)
Ungrazed	2383 ab*	31.21 d	54 c	--
Lightly grazed	2752 a	43.02 a	56 bc	21.08 c
Moderately grazed	2461 ab	34.19 b	60 abc	42.78 b
Heavily grazed	2123 bc	34.40 b	65 a	56.21 ab
Extremely grazed	1859 c	32.86 c	63 ab	62.22 a
Mean (Avg)	2315	35.14	60	36.46
Standard Deviation	340	4.59	4.62	25.78
*Means in the same column followed by the same letter are not significantly different; P≤0.05)

Table 3. Percent carbon and percent nitrogen content in the soil.
Description	Overflow						Silty
	Pasture 7		Pasture 9		Pasture 11		Pasture 5		Pasture 6
	Light	Ungrazed	Heavy	Ungrazed	Extreme	Ungrazed	Moderate	Ungrazed	Extreme	Ungrazed
Total Carbon	3.40	3.43	3.93	4.54	4.33	4.02	3.20	3.05	3.52	3.74
Total Organic Carbon	2.91	2.95	3.93**	4.54	4.33	4.02	3.20a*	2.86b	3.30	3.56
Total Nitrogen	0.26	0.27	0.33	0.39	0.36	0.34	0.28	0.25	0.30	0.31
Means in the same row within the same pasture followed by a different letter are significantly different; (P≤0.05) *Inorganic carbon was 0.00 in many samples.

The same grassland in the hands of different people will be used to meet different management goals. For example, a farmer’s primary goal may be to use the land to produce an economic benefit, while others may place more emphasis on the different ecosystem services provided by the grassland. There are no easy answers to the question of how to balance different management goals. Our goal in this report is to develop an integrated index (I) in combination with some sensitive parameters to grazing within grazing ecosystems to evaluate ecosystem services for different management strategies:

S_biomass, S_water, S_beef represent the value of aboveground plant biomass production, percent water content in the soil, and beef production after standardization to a mean of zero and a standard deviation of one (Table 4). For example the standardized index for biomass production on ungrazed overflow sites is -0.40. This value was obtained from the following formula (See Table 1 for production values):

Table 4. The standardization of the index on the overflow and silty sites.
Grazing Intensity	Overflow Sites			Silty Sites
Grazing Intensity	S_biomass	S_water	S_beef	S_biomass	S_water	S_beef
Ungrazed	-0.40	-0.68	-1.04	0.20	-0.86	-1.41
Lightly grazed	0.71	1.62	-0.59	1.28	1.72	-0.60
Moderately grazed	0.62	0.24	-0.51	0.43	-0.21	0.22
Heavily grazed	0.66	-0.30	0.95	-0.57	-0.16	0.77
Extremely grazed	-1.59	-0.88	1.18	-1.34	-0.50	1.00

For different objectives, we give the parameters in the vector [w₁,w₂,w₃] different weight values. For example, if we want to use the grassland as a tool for earning a living, we should give cattle gain/acre greater weight [0, 0, 1]. If natural resources sustainability is most important, we would give greater weight to aboveground biomass production [1, 0, 0]. If we think aboveground biomass, water content in the soil, and the gain/ acre are equally important, we should give them equal weight [0.33, 0.33, 0.33]. Of course, anyone can select different indexes and give different weights based on their land use goals.

We will discuss some typical scenarios according to different weight values of the three parameters selected which correspond to different management strategies. The integrated evaluations of ecosystem services are shown in Table 5 and Table 6.

Table 5. The standardized index and evaluation index on the overflow range sites for various management plans. Bold figures represent the highest score for the management plan.
Management Plan	Ungrazed	Lightly Grazed	Moderately Grazed	Heavily Grazed	Extremely Grazed
S_biomass	-0.40	0.71	0.62	0.66	-1.59
S_water	-0.68	1.62	0.24	-0.30	-0.88
S_beef	-1.04	-0.59	-0.51	0.95	1.19
[1,0,0]	-0.40	0.71	0.62	0.66	-1.59
[0,1,0]	-0.68	1.62	0.24	-0.30	-0.88
[0,0,1]	-1.04	-0.59	-0.51	0.95	1.19
[0.5,0.5,0]	-0.54	1.17	0.43	0.18	-1.24
[0.75,0.25,0]	-0.47	0.94	0.53	0.42	-1.41
[0.25,0.75,0]	-0.61	1.39	0.34	-0.06	-1.06
[0.5,0,0.5]	-0.72	0.06	0.06	0.81	-0.20
[0.75,0,0.25]	-0.56	0.38	0.34	0.73	-0.90
[0.25,0,0.75]	-0.88	-0.27	-0.23	0.88	0.50
[0.33,0.33,0.33]	-0.70	0.57	0.12	0.43	-0.42

Table 6. The standardized index and evaluation index on the silty range sites for various management plans. Bold figures represent the highest score for the management plan.
Management Plan	Ungrazed	Lightly Grazed	Moderately Grazed	Heavily Grazed	Extremely Grazed
S_biomass	0.20	1.28	0.43	-0.57	-1.34
S_water	-0.86	1.71	-0.21	-0.16	-0.50
S_beef	-1.41	-0.60	0.24	0.77	1.00
[1,0,0]	0.20	1.28	0.43	-0.57	-1.34
[0,1,0]	-0.86	1.71	-0.21	-0.16	-0.50
[0,0,1]	-1.41	-0.60	0.24	0.77	1.00
[0.5,0.5,0]	-0.33	1.50	0.11	-0.37	-0.92
[0.75,0.25,0]	-0.07	1.39	0.27	-0.47	-1.13
[0.25,0.75,0]	-0.60	1.60	-0.05	-0.26	-0.71
[0.5,0,0.5]	-0.61	0.34	0.34	0.10	-0.17
[0.75,0,0.25]	-0.20	0.81	0.38	-0.24	-0.76
[0.25,0,0.75]	-1.01	-0.13	0.29	0.44	0.42
[0.33,0.33,0.33]	-0.68	0.79	0.15	0.01	-0.28

If the primary goal of grassland use is to produce economic value, the extreme grazing intensity had the maximal value both on the overflow and silty range sites. On both range sites, if we place equal weight on biomass, water in the soil, and livestock gain, the light grazing intensity had the maximal value. On the overflow site, if we consider just biomass and beef production (gain/acre), the heavy grazing intensity had the maximal value. In other areas, such as the silty site, light grazing intensity had the maximal value depending on how much weight is given to aboveground plant biomass versus beef production.

Although we selected only three indexes to investigate in this report and further investigations should be done, the results demonstrate the usefulness of this type of research for land-use planning.