Altitudinal chemical composition variations in biomass of rangelands in Northern Greece

I Mountousis, K Papanikolaou, G Stanogias*, F Chatzitheodoridis and V Karalazos

Department of Animal Production, Faculty of Agriculture,
Aristotle University of Thessaloniki, 54006 Thessaloniki, Greece
dkklinon@otenet.gr (Ioannis Mountousis); klineota@yahoo.gr (Ioannis Mountousis); fxtheo@econ.auth.gr
*Department of Animal Production, Faculty of Agriculture, T.E.I., 53100 Florina, Greece

Abstract

This experiment constitutes part of a two-year research study, which was undertaken in spring 2004. The aim of this experiment was to study the altitudinal variation of the chemical composition of the grazable material in Mt. Varnoudas pastures, North-western Greece. The effect of altitude and exposure on aboveground biomass production and chemical composition [crude protein (CP), ash, ether extracts (EE) and crude fibre (CF)] were studied in herbage samples harvested from 24 experimental cages placed in 8 different altitudes (from 900 to 2100m) towards different exposures (east-west-south), throughout the experimental period (May-October 2004). Sample collection was accomplished by cutting above-ground biomass at a height similar to that grazed by small ruminants.

 

The CP and ash content increased as altitude was getting higher, almost during the whole experimental period, while EE content presented trivial variations to altitude and exposure. On the contrary, CF content was reduced as altitude increased. In the beginning of the experimental period. Above-ground biomass production was initially reduced in higher altitudes; later on, however, there was an increase to every altitude. The combination of "altitude x exposure" influenced crucially the production (P<0.001);  the influence of exposure was also significant. Above-ground biomass production indicated (P<0.05) a positive correlation to altitude (r= 0.075) and to EE (r= 0.072) and crude fibre (r= 0.172) content, whilst it showed a negative correlation (P < 0.05) to exposure (r= -0.029), ash content (r= -0.122) and  protein content (r= -0.230).

 

In order to better exploit the pastures of this area it is considered wise, towards the end of spring, to move the herds from pastures of lower altitude to those of higher altitude for the summer.

Keywords: Altitudinal variations, biomass production, chemical composition, Greece, sub-alpine rangelands

 

 

Introduction

 

Quantity and quality of grazable material to pasturelands are affected by biotic and abiotic environmental factors including soil type, climatic regime, botanical composition, and management (Vázquez-de-Aldana et al 2000; Pérez-Corona et al 1998; Angell et al 1990; Norton 1982; Lyttleton 1973). At landscape scale, topographic factors such as slope, aspect and altitude, together with soil characteristics such as nutrients, structure and texture which largely depend on underlying geology, influence the biomass production and quality of grazable material of pasturelands (Mutanga et al 2004).

 

The quality of grazable material is of great significance to animal production as nutrition is an important factor to the cost of feeding of ruminant agricultural animals (Kitsopanidis et al 1986; Zioganas et al 2001). Quality is the parameter that includes the concentration of the partial nourishing constituents (chemical composition), the biomass quantity that is consumed (food intake), the digestibility and the segregation of metabolism products of the animals (Βιιxton 1996).

 

Although chemical methods can not directly assess the food value of grazable material, they are based on the statistic correlation in order to assess the digestibility and food intake. However, in combinations of the use of patterns, they are increasingly used to foresee animal's productivity or to define the factors that may restrain the animal's production (Minson 1981). The protein and cellular content, as well as the rate of inorganic elements of grazable material and digestibility, are highlighted as the major factors of pasture quality (Ballard et al 1990; Pérez-Corona et al 1994).

 

This research is part of a biennial experimental project, which began in the year 2004 and was completed in the end of the year 2005. The main aim of this research was to study the altitudinal chemical composition variations in above-ground biomass of sub-alpine rangelands in North-western Greece.

 

 

Materials and Methods

 

Study area

 

This research took place in the native and naturalized sub-alpine pastures of Mt. Varnoudas, north-western Greece (40^o 46΄ to 40^o 53΄ N, 21 ^o 07΄το 21^o 24΄E, 900-2100m above sea level). The average altitude of Mt. Varnoudas is approximately 1700m while the highest peak reaches 2334m. The basic background of the whole research area consisted of metamorphic rock textures (i.e. phyllites, gneisses and micas shcists) of the Pelagonic geotectonic zone. . The fertility of the soil varies depending on slope, exposure, and vegetation. The mountain and topographic lie is quite tense and, in combination to the climate conditions that change from zone to zone, create an impressive variation of flora from the lowest to the upper most zones. There are large areas covered by beech and oak forests as well as by other small trees and shrubs. The pasturelands in openings of forests as well as those in sub-alpine region are covered by a high diversity of herbs. The area has special climate characteristics which differ from those of the typical Greek Mediterranean climate (Papanikolaou et al 2001). The climate approaches the Middle - European type having as major characteristics a quite cold and damp winter and a rather dry summer. Sometimes in winter there can be observed very low temperatures, which can reach -23ºC, a fact, which is very unusual for the Greek climatic conditions. The monthly average air temperature as well as rain precipitation in the decade 1991 - 2000 was 12.2 ºC and 52.2 cm respectively. The rain precipitations during the experimental period (2004), was 53.8cm (HNMS 2005), a fact that shows a uniformity of both, rain precipitation and air temperature (~ 12ºC).

 

The pasturelands of Mt. Varnoudas were graded as seasonal (Papanikolaou et al 2002). That is, from 600-1500m, they are grazed during spring and autumn, while over 1500m they are grazed in summer.

 

To achieve the best exploitation of these seasonal pasturelands is necessary the altitudinal move of flocks, a practice which is applied by the stock breeders of this area.

 

Thus, 24 locations with uniform distribution of botanic content, facing 3 different exposures (East - West - South) and being in 8 different altitudes, which ranged from 900 to 2050m, were chosen to be investigated as part of the experimental project.

 

Sampling and chemical analysis methods

 

This research was conducted during the year of 2004, from May to October. Twenty four experimental cages, sized 4m x 5m, fenced with metallic net 1.5m high in order to obstruct free - range grazing, were placed. The north side of the mountain forms a part of the adjacent country (F.Y.R.O.M), so 8 experimental cages were placed to each exposure (east - west - south) to altitudes from 900 to 2050 m.

 

Each experimental cage was divided into 36 equal parts. In the beginning of each month, from May to October aboveground biomass was collected from 6 of the 36 parts. Sample collection was accomplished by cutting aboveground biomass imitating the way of small ruminant grazing (Odum 1971). The collected biomass was stored in paper bags and was weighted immediately afterwards. In the laboratory all samples were oven-dried at 68ºC until a steady weight.

 

The samples of each cage were transported to the lab, where they were placed in the lab desiccator in order to be dried at 68ºC until a steady weight was reached.

 

After drying the samples were weighted again. The proportion of moisture was estimated by the difference of the immediate weight in the fields and the weight after drying.

 

Afterwards it was followed the grinding of the plant samples and the storage in glass containers, which were prepared and ready for chemical analysis. The chemical composition of the samples was defined based on the AOAC methods (AOAC 1999), as far as dry matter, ash and crude protein were concerned (Kjeldahl's distillation method), while EE were defined with diethyl ether extraction in a Soxhlet apparatus and the definition of crude fibre was achieved by Weende's method in the Fibertec apparatus.

 

Statistical analysis

 

The data were analyzed statistically using univariate ANOVA testing for the effects of sampling month, altitudinal zone separately and month x altitude interaction, using the SPSS 12.0 pprogram (SPSS Inc. 2003). It was also carried out an analysis of the correlation and a stepwise regression of the variables with the help of the former statistical method.

 

Results and Discussion

 

Aboveground biomass production

 

The above-ground biomass production of grazable material indicated a differentiation among subsequent or different altitudes and exposures during the experimental period. The statistical analysis proved that there was a very significant influence (P<0.001) of the combination of altitude x exposure in above-ground biomass production, while it was also significant (P<0.05) the influence of exposure (Table 1).

The topography influences the distribution of rain precipitation, temperature and air moisture, draughts, and snow layers accumulation, as well as the kind of growing vegetation (Sarlis 1998). Under the same terms the northern and eastern exposure of an area indicates greater moisture than southern and western due to the difference in temperature and evaporation. This explains the variation in flora of pastures that lie in different directions. Thus, the mountainous pasturelands that are in different directions are valuable because grazing animals are able to find and exploit areas with different composition of biomass during different seasons of the year.

 

Above-ground biomass production varied among altitudes in the eastern, western and southern side of Mt. Varnoudas. In the beginning of the experimental period aboveground biomass production was greater in lower altitudes (900-1350m) due to propitious blooming circumstances of the vegetation of the pastures (temperature, moisture and sunlight). As the experimental period preceded the biomass production tended to increase in higher altitudes, while the maximum value was detected in the western pasturelands (Figure 1).

The variation that occurred in biomass production is possibly due to the presence of spring meadow plants with great leaf size, as well as to the chemical composition of the geological substrate. However, in general, each exposure presented the same variation with an increasing progress during the experimental period to each altitude.

 

As can be seen from Table 2 above-ground biomass production had a negative relation to exposure (r= -0.029), to the ash content (r= -0.122) and to CP content (r= -0.230). On the other hand, there is a positive relation to the EE (r= +0.072) and to CF content (r= +0.172).

To measure the degree of interdependence of above-ground biomass production of pasturelands and CP, CF and EE content that are statistically significant (P<0.05),  a stepwise multiple regression was carried out. Crude protein content seemed to be highly related to production, the contribution of EE content was considerable whereas there was not any contribution of CF content to the corresponding equation (Table 3).

Crude protein, ash, ether extract and crude fibre content

 

The CP content, in general terms, was increasing correspondingly to altitude to the eastern, western and southern research area. The maximum values in the beginning of the experimental period were presented in the east side and then, in the middle and the end of the experimental period, to the west side. The statistical analysis indicated that the altitude influences significantly (P<0.01) the crude protein content while there was no influence in the combination of altitude x exposure on it. The CP content presented a similar variation during the whole experimental period (Figure 2).

The statistical analysis indicated  a positive correlation (P<0.001) among CP to ash (r= +0.45) and EE (r= +0.34) content whereas there was a negative correlation (r= -0.68) to the CF content (Table 2).

 

As plants advance in maturity, their leaf/stem ratio usually decreases. The CP also declines with stage of maturation (Pérez-Corona et al 1994, Vázquez-de-Aldana et al 2000). Consequently, the rapid reduction of CP content, which is observed to lower altitudes in every area, is due to the different phenological stage of vegetation. It has been proved (Peterson et al 1992, Sheaffer et al 1992, Buxton 1996) that the ripening of plants concludes in the reduction of crude protein content on leaves and stems, but also leads to a greater analogy of stems, which have lower crude protein content than this of leaves, to the produced biomass. On the contrary, as altitude is getting higher the circumstances are more propitious because the ripening of plants occurs more slowly than in the areas of lower altitude.

 

Statistical analysis showed a small variation of ash content to every group of the experimental cages (Figure 3).

The influence of altitude and the combination of altitude x exposure to the ash content is significant, while there was not a significant influence of the exposure. Ash correlated negatively (P<0.05) with altitude (r= -0.21) and (P<0.001) crude fibre content (r= -0.42). Moreover, there was a negative relationship among ash content and exposure (r= -0.02), above-ground biomass production (r= -0.12) and EE content (r= -0.04). On the contrary there was a positive correlation (P<0.001) to CP content (r= +0.45) (Table 2).

 

The EE content indicated a low variation, which was similar in every altitude for every group of the experimental cages (Figure 4), presenting the lowest values at the end of the experimental period. Ether extract content indicated a negative relation to exposure (r = -0.14), ash (r= - 0.04) and (P<0.001) CF content (r= -0.40) whereas there was a positive relation (P<0.001) to altitude (r= +0.36) and CP content (r= +0.34) (Table 2). In addition there was a positive relation among EE content and above-ground biomass production (r= +0.07).

Crude fibre, which constitutes the cellular wall, is firstly destined to provide a measure of the indigestible part of food of grazing animals, although, in fact, ruminants can digest a part of it. Nevertheless, the analysis results of CF are very useful due to the significant negative correlation of digestibility of organic matter of the grazable material. Crude fibre content decreased at higher altitudes (Figure 5), a fact that can be explained by the different level of plant ripening, which is mainly due to the different levels of temperature and moisture but also to the variation of the botanical composition of grazable material as we move from lower to higher pasturelands in the research area.

This variation occurred similarly  in each direction. Statistical analysis showed that CF content was connected negatively with exposure (r= -0.09) as well as (P<0.001) with altitude (r= -0.36) and CP (r= - 0.68), ash (r= - 0.42) and EE (r= -0.40) content. On the other hand, CF was positively correlated (P<0.005) with above-ground biomass production (r= 0.17). A higher concentration in CF was found in the experimental cages in the west side of the research area, whereas the higher rate was indicated, in all of them, during October.

 

 

Conclusions

• According to the results of this research, there was a significant influence of the combination altitude x direction to above-ground biomass production of grazable material, while it was also significant the influence of altitude. There was a very significant  influence of altitude to ash, EE and CF content as well as to CP content. Above-ground biomass production presented a positive correlation  to altitude and to EE and CF content. On the other hand it presented a negative correlation between exposure and ash and crude protein content.

  
  
  

• The pasturelands in the west side of the research area indicated a higher production followed correspondingly by those in the south and east side. The highest production was indicated in the first stages in lower altitudes due to the faster ripening of plants while from the middle until the end of the period the production was higher in the pastures of higher altitudes (>1500m).

  
  
  

• The pure mountainous pastures (900-1650m) were more productive than the sub-alpine (>1650m) except from the last two months of the experimental period where sub - alpine pastures presented the greatest above-ground biomass production due to the different phenological type of plants that consist the grazable material of these areas.

  
  
  

• According to the former observations the correct management practice requires the moving of flocks in the end of spring from pastures of lower altitude to those of higher altitude during summer, as, based on the chemical content in higher altitudinal zones n that period, when there is grazable material of better quality in relation to that of lower altitudes.

 

 

Acknowledgments

 

This study is a by-product of the EPEAEK II project "Environment - Archimedes, A Support of Research in issues of Environment and Ecology in Technological Education Institutes" financed 75% by EC and 25% by Greek government.

 

 

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Received 26 July 2006; Accepted 20 August 2006; Published 5 September 2006

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