【作者】 马爽；

【导师】 陈秀蓉；

【作者基本信息】 甘肃农业大学 ， 植物病理学， 2004， 硕士

【摘要】 本文在甘肃环县典型草原实验区中设计不同载畜量三个处理：样地1（编号WS1），限制载畜量8只羊/hm2；样地2（编号WS2），限制载畜量24只羊/hm2；样地3（编号WS4），限制载畜量16只羊/hm2。以围栏封育的样地4为对照（编号WS3），对其土壤微生物数量的季节动态、生理类型、优势种群进行了研究。结果表明：土壤理化性状试验区土壤表现为：有机质、全氮和全磷含量低，碱解氮含量中等，速效磷极低。围栏封育地和适度放牧地在有机质、全氮、全磷和土壤含水量等方面均高于过度放牧地并且存在差异显著性，说明围栏封育和适度的放牧对恢复土壤肥力、改善土壤水分状况、维持草地生态平衡具有促进作用。 2、土壤微生物季节动态土壤微生物的季节变化明显，真、细菌均表现为6、7月数量较多，10月较少，放线菌则在10月份数量最多。不同样地间，微生物数量的变化也有明显的差异，全年微生物的总数量（×104 CFU/g dry soil）WS1最多为1918.2， WS4最少为1428.9。（1）细菌：各样地均以细菌占绝对优势，全年细菌总数量以WS1最多为1625.3，WS2最少为1124，分别占各自样地微生物总数的84.73%、75.54%，但是以WS3样地的变幅最小，种群最稳定。（2）真菌：全年真菌总数量最多的WS4为2.996，WS3最少为2.195，分占0.21%、0.13%。（3）放线菌：全年放线菌总数量以WS2最多为360.95，WS3最少为228.35，分别占各自样地微生物总数的24.26%、13.19%。说明，围栏封育和适度的放牧均可使微生物数量增加，有利于退化草场的恢复。方差分析显示，二者在微生物数量上没有显著差异。在三大类土壤微生物中，细菌数量占绝对优势，但是随载畜量的增加细菌数量减少，而真菌、放线菌则有不同程度增加。3、土壤微生物不同生理类群参与氮素循环的微生物主要类群中均以氨化细菌和固氮菌占较大比例，说明在WS1、WS2、WS4、WS3四个样地中氨化作用和固氮作用较强，但载畜量较大的WS2、WS4样地其氨化细菌、纤解菌、固氮菌的数量均少于载畜量小的WS1样地和围栏封育地，而芽孢杆菌数量则表现为WS2、WS4的数量多，表明随载畜量的增加，其退化程度加重，抗逆性强的芽孢杆菌数量亦增多。当地纤解菌以好气纤解菌为主，嫌气纤解菌<WP=6>数量极少，说明当地纤维素的分解主要通过好气纤解菌进行。同时， 载畜量适宜的WS1样地在参与氮素循环的微生物的数量上要优于围栏封育的WS3 样地。4、微生物种群和优势种群 WS1、WS2、WS4、WS3 四样地共有10种优势细菌，均以HJ4和芽孢杆菌为主要优势种群，同时，在围栏封育的WS3 样地，其优势种群与三个放牧地有差别，例如HJ13和HJ8在围栏封育的WS3样地数量较少，而在三个放牧地数量上升，成为优势种群。但三块放牧地之间，也存在差异，即在WS2、WS4样地，HJ16数量较少，而在WS1样地则上升为优势种群。四样地共有优势真菌7种，均以镰孢菌为最多，其中WS3与WS2样地分别占43.86%、34.67%；在WS2样地中青霉菌数量较多，成为优势种群，而在其余样地数量较少；茎点霉仅在WS3样地中占有较大比例，在三块放牧地几乎未检测到。这说明，实行放牧的草地与围栏封育草地之间在优势种群上有明显的差别，并且过度放牧草地与适度放牧草地在微生物种类和数量上也有差别。更多还原

【Abstract】 Based on three different treatments: NO1(WS1) carrying capacity is 8 sheep/hm2; NO2(WS2) carrying capacity is24 sheep/hm2; NO3(WS4) carrying capacity is 16 sheep/hm2; and one control: NO4(WS3,CK) enclosed grassland exempt from grazing (EGEG), quantitative dynamic change against seasons, physiological flora, dominant genera species under different carrying capacities in steppe of Huan Country of Gansu Provirce were studied in this paper. The results showed as follows:(1).Physicochemical properties of grassland soil General characteristics such as low content of organic substance, total nitrogen and phosphorus; medium of alkaline hydrolytic nitrogen, extreme low of available phosphorus.The EGEG and grazing properly are significantly effective in humidity improvement and fertility rehabilitation of grassland soil.(2).Dynamic change against seasons of soil microorganism Flourishing of soil microorganisms(fungi and bacteria) were in June and in July contrasted with their small quantity in October except for actinomyces. The total number of microorganism in 2003(х104CFU/g dry soil)showed the largest quantity (1918.2)in WS1 and the smallest (1428.93)in WS4. Quantitative pattern of various microorganisms among different samples were compared. 1)Bacteria were dominant regardless of the months and samples. Its annual proportion against total bacteria in respective samples reached 84.73%,75.54%in WS1,WS2 samples respectively, but there was a relative smaller fluctuation in WS3. 2)Fungi’s annual proportion against total fungi in respective samples reached 0.21%,0.13% in WS4,WS3 <WP=8>samples respectively. 3)Actinomyces showed the largest quantity (360.95)in WS2 and smallest (228.35) in WS3, its proportion against total actinomyces in respective samples reached 24.26%,13.19%in WS2,WS3 samples respectively. These data suggested that both EGEG and proper grazing could improve the number of soil microorganisms in order to renew the degenerate grassland. Among three kinds of microorganisms, bacteria were the dominant and with the augment of carrying capacities, the number of bacteria decreased while fungi and actinomyces increased. (3). Physiological flora of soil microorganisms Both ammonifiers and azotobacter were abundant in four samples. Nitrogen cycle related to microorganism group such as ammonifiers, cellulolytic microorganisms and azotobacter all gradually declined with increasing carrying capacities while Bacillus reversed. It showed that ammonification were stronger in four samples and anaerobic cellulolytic microorganisms were very scarce,which suggested that the cellulose lysis from local plants depended on aerobic cellulolytic microorganisms. Meanwhile, the number of nitrogen cycle related to microorganisms was larger inWS1 than in WS3. (4).Genera of microorganisms and dominant ones HJ4 and Bacillus appeared dominant in all tested samples. There were a few differences between EGEG and other grazing samples also. For example, HJ13,HJ18 were dominant in grazing samples while minor in EGEG. Difference also appeared between different carrying capacities samples. Apart from the same general pattern as bacteria, Fusarium sp appeared as the dominant fungeous genus in all four samples. Among different carrying capacities samples, difference appeared as well.更多还原