Effects of integrated components on available forage model in Southern rangeland of Iran

G R Badjian, D Ismail*, M S Othman** and A A Mehrabi***

Fars Research Center for Agriculture and Natural resources, P.O. Box: 71555-617 Shiraz-Iran
badjian@farsagres.ir
*Department of Animal Science, Faculty of Agriculture, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia
**Rainforest Academy, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia
***Faculty of Natural Resources, University of Teheran, Karaj, Teheran, Iran

Abstract

This study describes the components of pastoral rangeland system in Bakkan, Southern Iran and highlight issues relating to forage endowment and environmental dynamics. In this study, proper use factor and palatability models and their components use to develop the model of available forage and measure it. The components topography, land systems, vegetation, land use, and grass species composition changes were analyzed using GIS. In this study source of information are herders, land and livestock owners, research institution, and personal field inspections. Responses to the questionnaires were obtained from local government offices and research on rangelands and analyzed in parallel with the results of detailed interviews with pastoralists.

 

The results indicate that only 6.2% of the rangeland is in good condition and the rest are in fair (44.9%), poor and very poor (48.9%). About half of the rangeland area shows a positive trend, but are situated a long distance from the watering points, so are not favorable for grazing animals. The range condition situation and its trend in consideration of soil and slope properties in this study indicates that the rangeland in Bakkan is a fragile production system, sensitive to soil erosion and rangeland degradation, so for a long time sustainable exploitation should be goes to minimize land degradation in the future, proper management and sustainable exploitation should be implemented in the future

Keywords: Available forage model, Iran, Southern rangeland

Introduction

The fundamental challenge of grazing management is to optimize, simultaneously, the interception and conversion of solar energy into primary production and the efficient harvest of primary production by livestock. Grazing management involves the manipulation of kinds and classes of livestock, stocking rate, grazing season and grazing intensity to optimize these two opposing processes and maximize livestock production per unit area on a sustainable basis. The managerial task of optimizing primary production and efficient forage harvest is further complicated by climatically induced variation in plant production and the widespread occurrence of selective grazing (Briske and Heitschmidt 1991). Worldwide, at least 40 million pastoralists depend on natural grazing for their livelihood; most are subsistence herders and more than half are in Africa. Rapid increases in human and livestock populations this century, have contributed to increasing grazing pressures, particularly in arid and semi-arid environments (Grandin 1987; Olsson and Rapp 1991; Wiggins 1991). The disappointing record of development programs forced a re-interpretation of grassland ecosystems, their dynamics and development opportunities. This has led to a re-evaluation of concepts such as desertification, overgrazing, land degradation and an assessment of whether, in some grazing lands, no form of development is possible. The scientific community now acknowledges that the exploitation of spatial and temporal variability within grazing lands is a key factor for their sustainable use. With traditional, pastoral peoples, this has long been appreciated, as transhumant and nomadic systems show. The re-interpretation of rangeland ecosystems is often referred to as the "paradigm shift." This shift has led to a revised approach to rangeland development, based on a more complete understanding of grazing-based livestock production systems, including their limitations and dynamics, and a greater role for local people in participatory planning. The "new perspective," and the recent availability of innovative data collection and analysis tools, provides powerful new aids to improving the protection and management of grazed environments (Harris 2000).

 

In temperate and cold latitudes, such as the Bakkan district, the forage production year is distinctly cyclic and plant growth is concentrated in a limited growing season, during which time temperature and soil moisture are usually conductive to plant growth. Range and most pasture vegetation is highly heterogeneous and dynamic across space and time, and grazing animals can select diets much different from the average of what is available to them (Kothmann and Hinnant 1987). This study describes components of pastoral rangeland system in Bakkan, Southern Iran and highlight issues relating to forage endowment and environmental dynamics. It shows an integrated approach to land and forage resource assessment that facilitates quantification of the rangeland resource, understanding of resource component inter-relationships, and prediction of environmental impact and appraisal of development options. The output of the rangeland changes constantly due to the tremendous influences of many interacting factors. The technique described has been successfully applied in a PhD thesis, and is designed to overcome shortcomings of traditional methods of available forage assessment estimation (Badjian2005).
 

 

Procedure

 

Study area

 

The study area is located in the Bakkan catchments in the Fars Province, in the South of I. R. Iran. The area under the study (52º, 8´-52º, 28´E and 30º, 20´-30º, 37´N) is a 35,000-hectare plain. Its elevation range is from 2,200 to 3,135 meters (Mean 2,578 meters above sea level).   

The climate is semi arid with an average annual rainfall of 444.8 mm/yr., falling mainly in the autumn and winter. The average minimum and maximum temperatures are 2.6 ºC and 20.33ºC.

Sheep and goats were the two main sources of animal production. There are three main forage and herbage resources; 25,200 ha of rangeland and 10,000 ha of arable land that provide two main supplements (production of wheat, barley, and sugar beet residue) and herbage (production of alfalfa and barley). In addition, there is a 1,100 ha temporary lake. In Bakkan, the rangeland area is negatively affected by inappropriate land management practices, e.g. overexploitation. Uncontrolled exploitation of the vegetation of the rangelands has an effect on the forage quality because of the transition from a plant community with a higher nutritive value to one with lower nutritional value. Overstocking and extended grazing periods are current characteristics of inappropriate management practices in the study area. In this study, 220 plant species in fifteen major vegetation types were identified in highland rangeland in Bakkan in negative and poor trend and condition..

 

Identification and selection of development options

 

A study questionnaire was used for identification of local environmental and managerial constraints of rangeland to facilitate the relevant list of component issues and the subjective ranking of their importance. The component issues include factors that affect topography, edaphic conditions, plant species choice and rangeland management. Responses to the questionnaires were obtained from the local government offices and research conduction on rangelands and analyzed in parallel with results obtained from detailed interviews with pastoralists. In general, opportunities for rangeland improvement through plant species introduction has more potential in the more humid zones, whereas grazing management is the primary option in arid areas, but an important aspect across all zones.

 

Geographical Information System (GIS) technology, in association with detailed land use surveys is a valuable tool for modeling and analyzing land systems and therefore useful in development planning and management (GIS2003). The following components were analyzed using GIS: topography, land systems (landform, climate, soil type, soil depth and soil texture), vegetation, land use, and grass species composition changes. Arzani (1999) used a visual scoring method of the available dominant species to report the vegetation cover map, botanical composition, and forage production in 15 vegetation types (VT) in the Bakkan region. In this study, his results were used in order to develop a model of available forage and its components, including the Proper Use Factor (PUF) model and the palatability (PL) model and a hardcopy of the map, developed from the digitized calculation of the VT found in the rangeland.  Overlay of integrated areas of VT and PUF, were shown by utilizing GIS Arc/view features.

 

Proper use (PUF) is defined as the degree of utilization of the current year's growth that, if continued, will achieve management objectives and maintain or improve the long-term productivity of the site. PUF varies within season and systems of grazing (Butler et al 1997). Season, rainfall, soil types, slope types, vegetation types, rangeland condition and trend, palatability and management are all factors that can included as components for the available forage model (Figure 1).  

Rangeland forage types, condition and dynamics

 

Vegetation classes, along with distribution information, are an adjunct to general land use data sets. This information is necessary to characterize the study area, ascertain rangeland condition and assess proper use factors. For each vegetation class, information included; floristic composition, area, altitude range, rainfall range, temperature range, soil type, edaphic factors, and the occurrence of palatable and unpalatable plants. Floristic composition and vegetation class information, in effect, summarized the spatial environmental variability of the area. The principal forage parameters required are; yield, utilization and quality. Values of each of these parameters reflect the inter- and intra-year variability of forage supply typical of many rangelands, particularly in arid and semi-arid environments.

 

Rangeland condition and dynamics are major issues in the assessment of grazing land for sustainable use. This is especially true in relation to ecological thresholds, such as; responses of the system to changes in grazing pressure, seasonality of production and the level and impact of inter-year variability of climate on system productivity (Harris 2000). Information on the seasonality of forage supply can be used to assess the nature of forage resources and feed balances, particularly in relation to livestock forage requirements. General information on grassland growth patterns was obtained from Badjian (2005). Details, such as patterns and trends of rangeland and the occurrence of forage deficits were obtained from interviews with pastoralists. Rangeland condition (RC) is a value-laden term, often associated with particular models of rangeland change or particular modes of measurement. Sometimes, RC is assumed to exist in some absolute form and assessments are designed to capture it, or at least to approximate it as closely as possible. The differences amongst definitions are significant, and reflect perceptions of how and why change occurs under use, and the objectives of the assessment (Holechek et al 2001). The term is simply a concept, comparing the level of specific indicators such as vegetation cover, production, composition or soil erosion at a particular location with the assumed potential for that attribute within that vegetation type or compared with other locations.

 

Range trend (RT) is the direction of change in condition or state of the rangeland. However, a true representation of trend has rarely been measured successfully by comparing data over time (Friedel et al 2000). RT in this study was categorized as up, down and fair trend classes and illustrated in detail in Badjian (2005). Estimates at a single point in time of ‘apparent trend’ have depended on current measures of plant composition, plant age, distribution, vigor, litter accumulation and soil surface condition (Wagner 1989).  

 

So range condition of a site based upon the above four factors is then determined by totaling the condition scores for all species present. The numbers obtained (0% to 100%) can be divided into 4 classes:

·                    Excellent Condition = 76 to 100% of the climax community

·                    Good Condition = 51 to 75% of the climax community

·                    Fair Condition = 26 to 50% of the climax community

·                    Poor Condition = 0 to 25% of the climax community (Arzani 1999).

The coefficient rates including consideration of RT and RC for PUF and the requirement to leave 50% of the forage for regeneration and soil conservation (SRM 1991) are shown in Figure 2.

Because livestock is the major user of primary production in the semiarid and arid regions, degradation has always been attributed to this sub-sector (Sidahmed and Yazman 1994). United Nations Environmental Program (UNEP) singled out human impact and, specifically, livestock grazing as being the cause of the irreversible degradation, which prevailed during the past two decades (New Scientist 1992). Most of Iran’s rangeland is in a class lower than poor condition (very poor). So the first class of rangeland condition (Excellent) is no longer seen. Sheep are less intimidated by steeper terrain than cattle and tend to prefer upland grazing sites. Sheep used all slopes regardless of steepness, but when terrain was especially rough, the animals mostly trailed through the area, making little use of the available forage. Sheep utilization was relatively uniform on all side slopes less than 45%, but utilization was reduced by 50-75% on the steeper slopes. The un-herded sheep tended to use the same bedding grounds on the ridge tops with up to 70% forage removal but with significantly less forage use on the mid slopes and bottomlands (Glimp and Swanson 1994)

 

Edaphic conditions

 

The characteristics and distribution of soil types provide substantive information relating to land use patterns and highlight edaphic constraints to rangeland. This information is also necessary to assess suitability of plants proposed for introduction. Historical land use data allows for the analysis of trends in land use and land capability. The main sources of land use and class data are universities and research institutions and land users.

Jaafari and Sarmadian (1999) concluded that 17 soil types exists in Bakkan. The soil properties of the soil types found in Jaafari and Sarmandian (1999) were used in this study as one of the main factors of PUF. The relationship between soil types and species in rangeland was determined by the local knowledge of nomads and consultation with Iranian soil experts from Tehran University. Soil types were categorized in four groups based on the definitions from Badjian (2005) in details. Soil depth, type, texture, gravels, structure, rocky outcrops, and groundwater were the characteristics used to categorize each group (Figure 2).

 

Topography or slope (SL)

 

Holechek (1988) provided the first formal procedures for adjusting grazing capacity for slope and distance from water, and his reductions are well supported by previous and present research like Valentine (2001). Most recently, the United States Department of Agriculture-Natural Resources Conservation Service has adopted Holechek’s guidelines. His guidelines involve no reduction for 0-10% slopes, 30% reduction for 11-30% slopes, 60% reduction for 31-60% slopes, and 100% reduction for slopes over 60%. At the very least, 50% of the above-ground biomass needs to remain each season, to ensure that the plant community remains viable, and can regenerate itself and remain resilient, even in the face of drought (Holechek et al 2001).

 

In this study, upon consideration of the Holechek guidelines, the coefficient rates of slope as a factor of PUF were defined and shown in Figure 2.

Estimation of proper use factors and palatability 

Two forms of utilization information are required for rangeland: proper use factors (optimal or recommended levels of use), and current levels of use. Differences between the forms of utilization indicate under- or overexploitation of the grazing. Such information was obtained from pastoralist interviews and field visits. Estimates of proper use factors incorporate grazing efficiency (the proportion of total herbage that livestock can harvest), carry-over losses between time of forage growth and consumption, forage losses due to trampling and fouling during period of consumption, and the maximum proportion of forage that can be grazed without causing rangeland deterioration (de Leeuw and Tothill 1990).

 

The estimation of proper use factors for grasslands is a complex process and carries the risk of misinterpretation due to generalization. Indicative values for a range of grasslands are presented in Table 1. Such values are influenced by local conditions and differences in livestock species, vegetation, soil and water conditions and the timing of grazing use relative to the forage growth season.

Based on SRM (1991), if a pasture is continuously grazed for the grazing season, PUF will be approximately 50% (i.e., take half and leave half); if the pasture is in a planned grazing system, “proper” use may be 60%. In the current study PUF is determined by the available forage from a maximum 50% of key species on key grazing areas (Badjan 2005). Forage availability (AF) is affected by integrated topography factors (SL), soil type’s properties (SOP), rangeland condition (RC) and rangeland trends (RT). The factors illustrated in Figure 1 follows the coefficient rates and minimum rate of the PUF model stated by Ebrahimi (1999).

              PUF_sp = f (Min. rate of one of: RC, RT, SOP, SL)                                 (1)

where PUF_sp is the proper use factor of the given species.

 

The cumulative PUF_sp consider as PUF in estimation of available forage (AF). Integrated VT and PUF were studied using GIS based on digitalized maps, and information was stored for later analysis. The coefficient rates of integrated factors were used to obtain new maps of integrated PUF.

 

Palatability is defined here as the relative attractiveness of plants to a grazing animal, whereas preference is the act of selection of specific plants by the animal. Animals select one type of forage over another based on smell, feel, and taste. Texture, leafiness, fertilization, dung or urine patches, moisture content, pest infestation, or compounds that cause forage to taste sweet, sour, or salty may therefore influence palatability (PL). The visual estimation for yield determination is made midway during mob grazing of the plants by sheep/goats. The determination of palatability is based upon the leaving of 50% of the forage for regeneration and soil conservation (SRM 1991). Therefore, the maximum palatability rating belongs to class one under good-fair rangeland conditions (50%) and the minimum belongs to class three under poor-very poor rangeland conditions (15%) (Arzani 1999). For this purpose, the species found in VT labeled in palatability classes, under consultation with the Iranian range management specialists. (Ebrahimi 1999). Figure 2 shows the integration of the forages palatability with consideration of RC (Arzani 1999).

 

Estimation of  available forage (AF) model

 

The term AF, refers to that portion of the forage production accessible for use by a specified kind or class of grazing animal. It is the consumable forage stated in digestible dry matter per land unit area, which removes by grazing livestock without damage to the forage plants. In this study, the PL model was compared with the PUF model to show the lowest coefficient rate for calculation of AF.

              AF_sp = PUF_sp (if PUF< PL) * P_spi * Svt (kg DM/ha)                           (2)

     or     AF_sp = PL_sp (if PL <PUF) * P_sp * Svt (kg DM/ha)                                  (3)

P_sp is the production of expected species in the VT, AF_sp is the available forage of expected species and S_vt is the area of VT.

 

These equations show the important role of PUF as a forage index and PL as a limiting factor for range grazing (Figure 2). Therefore, the amount of AF is conditional and based on the minimum coefficient rate of PUF or PL. This is due to the limitations and sensitivity of range production to degradation in arid or semi arid regions. Estimation of AF by plant species, the consumption by the animal and the contribution of the forage to the animal’s diet should be synchronized with each other in the same period (Currie 1987; Valentine 2001). 

 

To measure the forage production area, the digitized land use map of Bakkan was overlaid the digitized species production VT map. Furthermore, the VT map was overlaid on the PUF component areas, to show the amount of forage production in specific unit area accompanied with the available forage (AF).
 

 
Results                                                                                                                                                                                  

Digitized features of Proper Use Factor and its attributes

 

Figure 3 shows the digitized features of the vegetation types, soil, slope, rangeland trend and condition with their areas in Bakkan. Some vegetation types such as VT (9) with 5,573.3 ha and VT (15) with 5,149 ha have an important role in rangeland production of the Bakkan. A wetland in Bakkan covering 881.6 ha is a temporary lake during winter and early spring without an important role in forage production. The total area of VT was 24,809 ha.

These species in VT belong to six botanical compositions Perennial Legumes (PL), Perennial Forbs (PF), Shrubs (S), Perennial Grasses (PG), Annual Grasses (AG), and Perennial Grass-likes (PGl). Table 2 shows 15 VT forage productions among the 6 botanical compositions. This Table indicates that the VT8, VT12, VT7, VT10 and VT1 with 5,461, 3,144, 1,327, 1043 and 1,000 kg/ha respectively are the most productive VT in Bakkan.  

Figure 3 also indicates that only 1494 ha (6.2%) of the rangeland is in good condition and the rest are in fair (44.9%), poor and very poor (48.9%). About half of the rangeland (12,253ha) is situated at a long distance from the watering points, which makes it less attractive to grazing animals and shows a positive trend (up).

 

Property features of the 17 soil types and the area categorizes into four groups with their coefficient rates (Figure 3) indicates that most of the rangeland area has the soil type “group 3” (12,583 ha). This group is characterized by shallow to relatively deep soil with low infiltration rate (Figure 3). Goup 1 is located at the center of the plain and is very deep soil with suitable infiltration rate. Group 4 soil type, with very low depth and low infiltration rate, is rocky and sensitive to soil erosion. Group 4 and 3 covers 61.6% of the Bakkan rangeland, so special soil management techniques are needed to inhibit soil erosion in order to allow for a sustainable exploitation of the rangeland.

 

Slope type properties are included in the rangeland area (23,928 ha) and cropland with wetland area (10,597 ha) with defined located on slope range from zero to >40% steepness. Group 1 and 2 covers 83.3% cropland with a slope of 0-20%. Among the four slope groups, group 2 (10-20% slope) covers most of the Bakkan central area with its 15,047 ha. Only a small part of the Bakkan contains slopes >40% (Figure 3).   

 

Table 1 is the integrated results of the digitized feature of VT featuring of soil type, slope type, rangeland condition, and rangeland trend(s). The results indicate that most parts of the VT are located on two or more soil types with their affects. VT 1 and 12 cover only one soil and slope group and VT 4 and 15 are scattered on all soil groups (soil types) so it can be concluded these VT have a minimum and maximum  relationship with soil properties, respectively. The VT 9 and 15 are found on all slopes, VT 5 and 6 on three of them and the rest are found on either 1 or 2 slopes. Slope group 2 has the maximum frequency and slope group 4 has the minimum frequency based on their area. The results stated in Table 1 also indicate the impact of the slope type properties on the VT forage production.

 

Of the VT area, 31.8% is in poor condition, 13.8% is in very poor condition with the most negative range trend, 47.9% is in fair condition with the most positive rangeland trend and 6.7% has good rangeland condition with a downward range trend.

 

 

Discussion

 

Factors such as soil properties (17 soil types in 4 groups), topography or slope properties (0->40% slope steepness in 4 groups), range trend and range condition properties (15 vegetation types in 6 groups) were used in the PUF, while palatability of the vegetation and rainfall affect the forage availability and its utilization by animals. The results indicated that 26 coefficient rates were available in the PUF model for calculation of AF. Data shown in Figure 4 shows the mean forage production and available forage of 15 vegetation types. The data in this figure is the results of combining PUF components, palatability, and environmental factors on 15 vegetation types.

The results indicate that vegetation types 8 and 12 have the most productive species in presence of PUF components.

 

Soil, rangeland trend, condition, and topography are sustainable components of a vital production system such as Bakkan and have an important role in range management. They are used for estimation of PUF and PL models, calculation of forage production and available forage. This study indicates that rangeland in Bakkan is a fragile production system, sensitive to soil erosion and rangeland degradation. Therefore, a special range management plan should be dveloped to allow for a sustainable exploitation of the rangeland. Except in some parts of Bakkan most factors acted the same effect on forage production and available forage.
 

 

References

 

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