摘要
以宁夏沙湖的一个典型的干旱区草本型植物群落——芨芨草(Achnatherum splendens)-苦豆子(Sophora alopecuroides)(禾草-非禾草型)群落为研究对象,自芨芨草-苦豆子聚生丛的基部向丛间裸地依次划分为植冠区、过渡区和空旷区3个分区,通过比较分析两个优势种根系生物量密度在这3个分区的空间分布格局,研究了干旱胁迫生境中芨芨草和苦豆子的根际关系。结果表明:在水平方向上,芨芨草根系总生物量主要集中分布于植冠区,而苦豆子根系总生物量密度在3个分区间无显著差异;在垂直方向上,芨芨草的根系总生物量密度和细根生物量密度最大的土壤层次从植冠区到空旷区埋深渐深,而苦豆子的根系总生物量在3个分区主要分布于10～30cm土层,但其细根生物量密度最大的土层从植冠区向外呈上升趋势;同时发现,在植冠区,根系总生物量密度较高,两种植物细根生物量密度最大的土壤层次不同,但在空旷区和过渡区,两种植物细根生物量密度的垂直分布格局趋于一致。群落中两个主要植物种的根系在植冠区具有垂直层次的分异性,在不同分区间具有水平分布格局的差异性,这可能是群落中两种主要植物种间为了避免根系间直接竞争共同适应干旱胁迫生境的重要机制。
Aims Linking spatial patterns to ecological processes is a central topic in ecology. Inter-specific relationships in arid plant communities have been extensively studied by investigating aboveground patterns, but research on underground distribution patterns is inadequate. Our objective was to explore the inter-specific relationships between two dominant species, Achnatherum splendens （grass） and Sophora alopecuroides （forb）, in a typical grass-forb community of add/semi-arid regions of China. Methods We selected a 30 m×30 m plot in a representative A. splendens-S, alopecuroides community in Sand Lake, Ningxia Hui Autonomous Region, Northwest China. The two dominant species usually spatially assemble as clumps aboveground. We partitioned the spatial gradient from the base of the assemblages to the non-vegetated open spaces between assemblages into under-canopy, transitional and open subareas to characterize the horizontal differences of microhabitat. Five assemblages of the two species were randomly chosen, and a 150 cm deep soil profile with coverage of 100 cm×100 cm was excavated in each subarea. Root biomass in terms of fine roots （diameter 〈2 mm） and coarse roots （diameter 〉t2 mm） of the two species was investigated at soil depths of 0-10, 10-30, 30-450, 60-100 and 100-150 cm. Important findings Horizontally, biomass density of the total roots of A. splendens decreased along the gradient from under-canopy to open subareas. Also, ANOVA showed that biomass density of the to-tal roots significantly differed among the three subareas for A. splendens, but no significant differences were detected for S. alopecuroides. Vertically, the soil layers with the highest biomass density of the total and fine roots of A. splendens increased in depth from under-canopy to open subareas, while that of the total roots ofS. alopecuroides remained at 10-30 cm depth and that of the fme roots ofS. alopecuroides tended to decrease in depth along the gradient. Also, the free roots of the two species were different in the highest biomass density layer in the under-canopy subareas where root systems were densely distributed, but showed similar vertical patterns in the transition and open subareas. Niche separation in the under-canopy subareas and discrepancy in horizontal patterns of the two dominant species could represent an important adaptive strategy of avoiding direct competition and facilitating coexistence in arid communities.
出处
《植物生态学报》
CAS
CSCD
北大核心
2009年第4期748-754,共7页
Chinese Journal of Plant Ecology
基金
国家重大基础研究项目(2006CB400505)
国家自然科学基金(40675040)
关键词
干旱区
聚生丛
根系竞争
根系分布格局
生态位分离
arid environment, species assemblage, root competition, root distribution pattern, niche separation
