【作者】 董慧霞；

【导师】 李贤伟；

【作者基本信息】 四川农业大学 ， 森林培育学， 2005， 硕士

【摘要】 本研究是在天全县退耕还林（草）区内,以未退耕的陡坡耕地作对比,应用土柱法,对两种不同草本层模式（自然条件下生长的草本层一以下简称自然草林地和人工种植的黑麦草）毛白杨幼林的细根生物量和空间分布以及与土壤的抗蚀性关系进行了研究,结果表明: ①两种模式毛白杨林地内,黑麦草林地0～1mm细根全年总生物量为0.359t·hm^-2。其中上层生物量平均为0.179 t·hm^-2,活细根生物量占82.9%;中层为0.118t·hm^-2,活细根占81.41%;上、中、下三层生物量之比为50:33:17。自然草林地0～1mm细根全年总生物量平均为0.1891 t·hm^-2。其中上层生物量平均为0.101 t·hm^-2,活细根生物量占87.4%;中层为0.054 t·hm^-2,活细根占77.69%;下层平均生物量为0.034t·hm^-2,活细根占71.25%。上、中、下三层生物量之比为53:29:18。两种模式内0～1mm细根在上层和中层均占80%以上,且黑麦草林地0～1mm细根总生物量约为自然草林地的2倍。两种模式内活细根和死细根之比约为4:1。 黑麦草林地1～2mm细根全年总生物量平均为0.254t·hm^-2,上、中、下三层生物量之比为40:41:19。自然草林地1～2mm细根全年总生物量平均为0.276t.hm^-2,上、中、下三层生物量之比为42:34:24。两种模式内1～2mm细根在上层和中层均占80%左右,黑麦草林地1～2mm细根总生物量和自然草林地的相差不大。两种模式内活细根和死细根之比也约为4:1。 黑麦草林地0～2mm根系生物量为0.7335 t·hm^-2,其中草根0.121 t·hm^-2,占16.5%;上层生物量为0.3832 t·hm^-2,占52.2%,中层占32.9%,下层占14.9%。自然草林地0～2mm根系生物量为0.998 t·hm^-2,其中草根0.533 t·hm^-2,占53.4%;上层生物量为0.5879t·hm^-2,占58.9%,中层占23.5%,下层占17.5%。 ②从两种模式毛白杨林地内0～2mm总根系生物量的垂直分布及月变化看来,在上层均呈双峰型变化趋势,峰值都出现在5月和9月,且比较平缓,黑麦草林地最高值为0.5142 t·hm^-2,自然草林地为0.8066 t·hm^-2。尽管黑麦草林地在上层0～1mm和1～2mm的细根生物量均较自然草林地的高,但由于自然草林地内草根的生物量远比黑麦草林地的高,所以就0～2mm根系总量来说,自然草林地的更高;中层两模式林地更多还原

【Abstract】 With the steep plowland by contrast, the biomass spatial distribution and its relationship with the soil anti-erodibility of fine root <2mm in diameter between two herbages’ types (grass grown in natural conditions and ryegrass) of triploid populus tomentosa Carr woodland in Tianquan county, Sichuan province were studied. By using coring methods in the paper, the results were as follows:1. In the populus tomentosa Carr woodland under two types: In the ryegrass woodland, the average total biomass of tree root 0~1mm in diameter was 0.359 t.hm~-2 , the upper layer was 0.179 t.hm~-2 , live fine roots’ accounted for 82.9%; Middle layer was0.118 t.hm~-2, live fine roots’ accounted for 81.41 %; the ratio of biomass in upper layer, middle layer and down layer is 50 : 33 : 17. In the nature grass woodland, the average total biomass of tree root 0~1mm in diameter was 0.1891t.hm~-2, the upper layer was 0.101 t.hm~-2, live fine roots’ accounted for 87.4%; Middle layer was 0.054t.hm~-2 , live fine roots’ accounted for 77.69%, down layer was0.034 t.hm~-2, live fine roots’ accounted for 71.25%; the ratio of biomass in upper layer, middle layer and down layer was 53 : 29 : 18. In these two types, the both total fine root of upper layer and middle layer accounted for over 80%, and in ryegrass, the total biomass of 0~ 1mm fine root was about 2 times as much as those in the nature grass. And the ratio of live root and died root was about 4 :1.In the ryegrass woodland, the average total biomass of fine root 1 ~2mm in diameter was 0.254 t.hm~-2, The ratio of biomass in upper layer, middle layer and down layer was 40 : 41 : 19. In the natural grass woodland, the average total biomass of fine root 1~2mm in diameter amounted to 0.276 t.hm~-2, The ratio of biomass in upper layer, middle layer and down layer was 42 : 34 : 24. In these two types, the both total fine root of upper layer and middle layer accounted for 80%, but the total biomass is similar. The ratio of live root and died root was also about 4 :1.In the ryegrass woodland, the average total biomass of tree root 0~2mm in diameter was 0.7335 thm"2, the grass roots’ was 0.121 thm"2, made up 16.5% of the total biomass; In upper layer, the biomass amounted to 0.3832 t-hm"2, accounted for 52.2%; the middle layer and down layer were 32.9% and 14.9% respectively. In the natural grass woodland, the average total biomass of tree root 0~2mm in diameter amounted to 0.998 t-hm", the grass roots’ was 0.533 t-hm"2 and made up 53.4% of the total biomass. In upper layer, the biomass amounted to 0.5879 t-hm"2, accounted for 58.9% ,the middle layer and down layer were 23.5% and 17.5% respectively 02. From the vertical distribution and monthly changes of biomass of root 0~2mm in diameter under two types: The upper layer biomass showed mild double-peak trend, with peak in May and September; the maximum in ryegrass and natural grass forest were 0.5142 t-hm’2 and 0.8066 t-hm"2 respectively. The total biomass of tree root of 0~lmm and l~2mm in diameter in ryegrass forest were more than those in the natural grass forest. However, the grass root biomass in the natural grass forest was far more than that in the ryegrass forest; therefore, the total root amount of 0~2mm in the natural grass forest was more than that in the ryegrass forest. The biomass in the middle layer under two types both showed single-peak trend. The biomass in the ryegrass forest increased steadily and reached the highest in June, but the biomass in the natural grass forest increased little before June, and reached the highest in July. The down layer root biomass under two types changed smoothly, with little fluctuation.3. After 4 years in the land of converting from cropland to forest, between the woodland and steep plowland, the total content of water stable aggregate had little variation.The content of water stable aggregate in step plowland changed unorderly. But both two types showed that the content of bigger water stable aggregate in upper layer was more than that in the middle and down layer. The total content of water stable aggregate had little difference between the forest and step plowland. However, the bigger water stable aggregate in the upper and middle layer in the forest was obviously more than that in step plowland. In general, the content in the natural grass forest was more than that in the ryegrass forest.In the same depth, the organic matter content of the upper, middle and down layer inthe step plowland were more than those in the forest. The organic matter content of the upper and middle layer in the natural forest were less than those in the ryegrass forest. However, in the down layer the natural grass root input more organic matter to the soil than that in the ryegrass forest, which demonstrated that it was a relatively slow process increasing soil organic matter content through root.Disperse coefficient and disperse rate were taken as the index to soil anti- erodibility. To some extent, they could reflect the disperse and concretion capacity of the soil, but the bigger particle diameter water stable aggregate was more suitable to denote the anti-erodibility of the soil.4. With regard to increasing the content of bigger water stable aggregate(>5mm, 5~3mm) and the totals’ and reducing the content of small water stable aggregate in the soil, the effect of 0~2mm root was notable on the whole, and the significant coefficients were 0.752, 0.572, 0.786 and -0.563 respectively. 0~lmm root also played an important role, and the function of grass root is very significant. The root could increase the bigger water stable aggregate and decrease the small water stable aggregate content in the soil. In this way, fine roots increased the soil anti-erodibility.In conclusion, the converting farmland to forest (grass) was a comparatively suitable popularization method for increasing the soil anti-erodibility.更多还原