黄土高原弃耕地植被演替及其对土壤养分动态的影响

弃耕地演替过程中植被和土壤的互动效应对于植被恢复与重建具有重要意义。本研究选择黄土高原不同演替阶段的弃耕地(弃耕时间分别为1、6、12、22年),连续2年调查各弃耕地的物种丰富度、群落地上生物量,测定0~60 cm土层的土壤容重、pH值、土壤有机质和全氮含量,分析弃耕地演替过程中群落地上生物量、土壤理化性质的变化过程和趋势以及植被土壤之间的互动效应。结果表明:1)弃耕地演替过程中,弃耕早期(1~6年)为茵陈蒿+白莲蒿的杂草群落,演替中期(6~12年)为赖草群落,演替中后期(12~22年)为无芒隐子草+短花针茅群落。随着弃耕时间的增加,物种丰富度呈先减少后增加的变化趋势,地上生物量持续增加。2)土壤有机质和土壤全氮在0~10 cm土层中最高,表现出明显的表聚效应;弃耕时间和土层深度对土壤有机质和土壤全氮产生极显著的影响,弃耕时间与土壤有机质和土壤全氮之间均表现为负相关关系,土壤有机质和土壤全氮具有较为明显的时间效应。3)群落地上生物量与弃耕时间呈显著正相关关系,与土壤有机质和土壤全氮二者之间呈负相关关系,弃耕时间对群落生物量产生正效应,土壤有机质和全氮对群落生物量产生负效应。

The interaction effects of vegetation and soil nutrients on vegetation succession in abandoned farmland on the Loess Plateau

The interaction effects between vegetation and soil are highly significant for vegetation restoration and reconstruction during the succession of abandoned farmland. We chose four kinds of abandoned farmland in the Loess Plateau (1, 6, 12, and 22 yr) to investigate species richness and aboveground biomass. We also determined soil bulk density, pH value, soil organic matter and soil total nitrogen in the 0-60 cm layer. We analyzed species variation processes and trends in aboveground biomass, soil organic matter and soil total nitrogen, as well as the interaction effect between vegetation and soil during the succession stages. Species richness showed an increasing-decreasing-increasing trend and soil bulk density showed a decreasing trend at first, then tended to stabilize during the succession stages. Soil organic matter and soil total nitrogen were significantly different in the soil layers of the 4 kinds of abandoned farmland, and they showed obvious gathering effects at the soil surface. Abandonment time was negatively correlated with soil organic matter and soil total nitrogen. Soil organic matter and soil total nitrogen indicated obvious time effects during the succession stages. Aboveground biomass was significantly correlated with abandonment time, soil organic matter and soil total nitrogen. The results showed that soil organic matter and soil total nitrogen have negative effects on aboveground biomass and that abandonment time has positive effects on aboveground biomass during the succession of abandoned farmland.