宁夏干旱区3种典型植物群落根系和土壤水分的空间特征

Distribution patterns of root biomass and soil water contents in three typical arid communities in Ningxia Hui Autonomous Region

以宁夏回族自治区平罗县西大滩的草本型、灌草型和乔草型3种植物群落为研究对象，测定了各群落中不同微生境区位（冠盖区、过渡区和空旷区）的表层土壤稳渗率，土壤密度、植物根系生物量密度和土壤含水率的垂直分布（0～10、10～30、30～60、60～100和100～150cm梯度层）：结果表明：表层土壤稳渗率在各群落中从空旷区向冠盖区不断增大，植物生长能显著提高土壤稳渗率；各群落中相应区位表层土壤稳渗率也存在差异，其中，受植物生长影响较小的空旷区的稳渗率在乔草型群落最大，草本型群落次之，灌草型群落最小，但未达到显著水平；各群落内有较好荫蔽条件的冠盖区0～10cm土壤表浅层中细根密度最高，但过渡区与空旷区细根密度最高的土层埋深下移；采样期间，各群落冠盖区下层土壤均出现不同程度的逆含水率梯度，草本型群落最明显，乔草型群落最弱。

Three typical arid clump-assembled communities （grass-forb, shrub-grass and arbor-grass in lifeform composition） were selected at Xidatan, Pingluo County, Ningxia Hut Autonomous Region to study the special distribution patterns of root systems and soil water contents, as well as the relationship between soil site conditions and vegetation types. Accordingly, three subareas （namely under-canopy, transitional and open-land） were partitioned out in each community to represent the different microhabitats from the base of clumps to inter-clumps bare land. For each sub-area in the three communities, soil bulk densities, root biomass densities, soil water contents in the 5 sequential soil layers （0 - 10 cm, 10 -30 cm, 30 -60 cm, 60 -100 cm and 100- 150 cm in depth） and soil surface steady infiltration rates were meas- ured respectively. The results showed that ： （ 1 ） Surface steady infiltration rates increased from open-land to under-canopy subarea in each community, indicating that the growth of plants can significantly improve the soil infiltration rate; （ 2 ） Steady infiltration rates in open-land subarea where affected little by plants and represented relative original site condition were higher in arbor-grass community than in shrub-grass community to some extent; （3）In each community, the highest fine root biomass density in under-canopy subarea was in 0 - 10 cm soil layer, but in deeper layers in transitional and open-land subareas; （4）luversed soil water content gradients were detected in the three communities during the sampling period, especially in the under-canopy sub-areas. And the trends behaved the most intensively in the grass-forb community, but the least in the arbor-grass community.