| Influence of different grazing intensities in desert steppe on some physiological indexes of several pastures |
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| DOI：10.7606/j.issn.1000-7601.2008.02.16 |
| Key Words: desert steppe grazing intensities pastures physiological indexes |
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| Abstract: |
| The changes about free amino acids(Pro) and malondialdehyde(MDA) contents in pastures leaves,soluble sugars(WSS) and reducing sugars contents in pastures roots,three protective enzymes named superoxide dismutase(SOD)、catalase(CAT) and peroxidase(POD) activities in pastures leaves of five pastures that were Stipa bungeana、Lespedeza potanimii、Leymus secalinus、Pennisetum flaccidum and Cleistogenes squarrosa were studied under different grazing intensities in desert steppe.The results showed that all the physiological indexes of five pastures represented different degree changes with the enhancement of grazing intensities.The Pro content increased at first and decreased later in Leymus secalinus,but increased continuously in other pastures.The activity of SOD of Stipa bungeana was in the highest when grazing intensity reached 1.05 sheep/hm2,and was 1.86 times that of 0 sheep/hm2. The activity of SOD of Cleistogenes squarrosa was highest when grazing intensity reached 1.50 sheep/hm2, and was 2.13 times that of 0 sheep/hm2. These two pastures had relative high activities of protective enzymes,and these enzymes behaved relatively cooperativity.The contents of MDA were low and enhanced little.WSS contents in roots decreased at first and increased later.The activities of protective enzymes in Pennisetum flaccidum were in the middle under light grazing intensities and became smaller under heavy grazing intensities.POD activity of Leymus secalinus had no evident coherence with SOD and CAT activities.The contents of MDA in these two pastures enhanced markedly,while the contents of WSS declined continuously.When grazing intensity reached 1.50 sheep/hm2, the contents of MDA of Pennisetum flaccidum and Leymus secalinus were 4.68 and 3.89 times those of 0 sheep/hm2 respectively.Protective enzymes activities of Lespedeza potanimii were relatively low;moreover,MDA content was in the lowest and had a small enhancement.The content of WSS decreased at first and increased later.The changes of reducing sugars contents in roots for Cleistogenes squarrosa and Lespedeza potanimii accorded with the changes of WSS,but reducing sugars and WSS contents changes of other pastures did not represent obvious coherence.With the above physiological indexes as an estimation of feasible grazing intensity for testing pastures,grazing intensity of Stipa bungeana and Cleistogenes squarrosa should be no more than 1.05 sheep/hm2, Leymus secalinus no more than 0.45 sheep/hm2, Pennisetum flaccidum no more than 0.60 sheep/hm2. For Lespedeza potanimii,grazing intensity could reach 1.50 sheep/hm2. |
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