黄土丘陵沟壑区弃耕地群落演替与土壤性质演变研究

Study of the Different Succession Stage Community Dynamic and TheEvolution of Soil Characteristics of the Old-field in Loess Hills Gully

通过对黄土丘陵沟壑区退耕2a、68、9a、13a、16a、19a、25a、30a、40a的弃耕地土壤性质演变分析,初步总结出:①土壤含水量在整个的演替过程中,弃耕9a的群落,每一土层的土壤含水量大于其它群落相对应土层的土壤含水量;②土壤容重的平均值从大到小的排列顺序为:弃耕6a＞9a＞13a＞16a＞19a＞25a＞2a＞30a＞40a的群落.除受耕作影响弃耕2a的群落外,从6a到40a随着演替的进展,土壤结构得到改善,土壤容重逐渐变小;③随着演替时间的延续,土壤有机质、全氮、有效氮、全磷、速效磷、速效钾的含量都呈逐渐增加的趋势,而在不同阶段,其变化趋势有所差异;④在黄土丘陵沟壑区的弃耕草地上,土壤的理化性质在0～60cm易发生变化,而在60～100cm土层随着演替时间的增加,土壤的理化性质变化缓慢.⑤尽管演替进行的缓慢,但从土壤发展的角度来看,仍属进展演替,所以在黄土丘陵沟壑区,若排除人为干扰(开垦、放牧等),在现有的气候与环境条件下,植被有望得到恢复.

This paper analyzes the evolution of soil of the abandoned fields of 2 years, 6 years, 9 years, 13 years, 16 years, 19 years,25 years 30 years and 40 years in loess hills gully, and concludes ： ①in the whole evolution process except the 9 years abandoned farmland, the water content in one soil layer is higher than the other. ②The average of the soil bulk density can be sorted, form large to small, 6 years 〉9 years 〉13 years 〉16 years 〉19 years 〉25 years 〉2 years 〉30 years 〉40 years. With the process of the evolution form 6 years to 40 years, the soil construction has improved and the soil bulk density has gradually become smaller except the 2-year-abandonded-field community affected by farming. ③With the succession time lasting, the content of Organic matter, Total nitrogen, Available nitrogen, Total phosphorus, Available phosphorus and Available potassium in the soil all have increased. However, in different stages, they have different trend. ④ On the abandoned farmland in experiment station in loess hills gully, the soil physical and chemical property can be easily changed in the depth from zero to 60 cm. But in the depth from 60 cm to 100 cm, it changed slowly. ⑤Although this succession is slow, it still belongs to succession from the role of the soil development. In loess hills gully, if it was not destroyed （cultivate, graze and so on）, the vegetation can be recovered under the current climate and environment.