黄土高原草地根系生物量沿环境梯度变化规律

Changes in root biomass of grassland along the environmental gradient in the Loess Plateau

草地是陆地生态系统的重要组成部分,根系生物量是研究草地生态系统的重要参数之一,研究草地根系生物量沿环境梯度的变化规律对当地的植被建设和恢复具有重要意义。以黄土高原3种不同草地类型(森林草原、典型草原和荒漠草原)为研究对象,沿环境梯度从东到西选择10个样地,每个样地内设置8个1 m×1 m样方进行根系生物量的调查,旨在分析不同草地类型根系生物量的垂直分布规律,并探讨了根系生物量沿环境梯度的变化规律及其影响因素。结果表明:(1)黄土高原3种草地类型根系生物量有显著差别(P<0.05),其中森林草原的根系生物量最大,典型草原最小;(2)3种不同草地类型根系生物量垂直分布均呈"T"型,土壤表层(0-10 cm)占55%以上的根系生物量,且荒漠草原根系有更多比例的生物量分布在土壤表层;(3)黄土高原草地根系生物量沿经度从东到西呈现先减少后缓慢增加的趋势,但浅层生物量与深层生物量比例(浅深比)没有表现出明显的经度格局;(4)总根系生物量的变化主要受年均温(MAT)影响(P<0.01),随MAT增大而增大;深层生物量同时受气候和土壤养分含量的影响(P<0.01);浅深比则与样点平均土壤全磷含量、深层土壤全磷含量有显著负相关性(P<0.05);(5)气候和土壤因素能解释根系生物量5.12%-39.36%的变异,独立作用中,气候因子对根生物量的解释度最大,可达到2.77%-9.12%的解释度。

Grassland is an important part of terrestrial ecosystem,plant root system plays a critical role in the growth and development of the whole plant,which has the basic functions of storing nutrients,transporting water and supporting plant body.And root biomass is one of the important bases and parameters for studying grassland ecosystem.Thus,studying how root biomass of the grassland changes along environmental gradient is of great significance to local vegetation construction and restoration.Here,we selected ten sites from east to west in the Loess Plateau,which covered the main grassland types,including forest grassland,typical grassland and desert grassland.At each site,the roots of grassland plant were sampled to 0 cm to 50 cm soil depth at eight experimental plots(1 m×1 m)by using roots cores.We aimed to reveal the vertical distribution of root biomass of three different grassland types in the Loess Plateau,and explore the pattern of root biomass along the environmental gradients and their influencing factors.Our results showed that:(1)the root biomass of three different grassland types in the Loess Plateau was significantly different(P<0.05),with the root biomass of forest grassland being the largest and that of typical grassland being the smallest.(2)All of the root biomass vertical distributions of the three different grassland types in the Loess Plateau were“T”type,and the surface soil(0—10 cm)accounted for more than 55%of total root biomass.Moreover,more proportion of the root biomass of the desert grassland was distributed on the surface soil.(3)As the longitude increased,the grassland root biomass of the Loess Plateau decreased first,and then increased.However,the ratio of the root biomass of shallow soil layer to the root biomass of deep soil layer(i.e.,shallow⁃deep ratio)did not show an obvious longitudinal pattern.(4)The change in total root biomass was affected positively by the mean annual temperature(MAT)(P<0.01).But the root biomass of deep soil layer was affected by both climate and soil nutrient content(P<0.01),and the shallow⁃deep ratio was influenced negatively by the total soil phosphorus of average soli layer and deep soil layer(P<0.05).(5)Climate and soil factors could explain 5.12—39.36%of the variation in root biomass,among the independent effects,climate factors had the largest explanatory degree to root biomass,which could reach 2.77%—9.12%.