摘要:在喀斯特地区异质性生境中，土壤水分含量、植物生存空间和养分状况等的综合作用共同影响植物的生理功能和生长发育。以多年生黑麦草（Lolium perenne L.）为研究材料，通过模拟同质（S-S：浅土-浅土）和异质（S-D：浅土-深土）两种小生境，探究3种施水量（对照：W₀、中度干旱：W₁、重度干旱：W₂）条件下植物对异质生境的适应，主要解决以下问题：异质生境下植物是否会主动寻求高水分、厚土壤、或者更宽阔的生长空间来提高其对异质性生境的适应?降雨量的改变是否会导致植物的适应策略发生改变？主要结果如下：（1）只有在重度干旱（W₂）条件下，异质性生境中黑麦草的株高、分蘖数以及地上、地下生物量和地上、根质量分数显著高于同质生境，而在对照（W₀）和中度干旱（W₁）条件下两种生境均无明显差异。（2）在对照降水（W₀）条件下，异质生境中黑麦草浅土区根系生物量、根组织密度较深土区少，比根长、比根面积较深土区大；随着施水量的减少，浅土区根系生物量占整个植株根系生物量的比例呈现先减小、后增大的趋势，深土区的比根长、比根面积逐渐增大，根组织密度逐渐减小。以上结果表明，在异质性生境中黑麦草表现出更强的抵御干旱胁迫能力，且随着干旱程度的加重这种优势更加明显：异质性生境中黑麦草通过将有限的生物量更多的分配在深土区，同时增大深土区根系的根组织密度，使得根系在生长环境好的斑块中大量增生和下扎，使植株获得大量的水分和养分，而浅土区则充分利用较少的资源，通过增大比根长和比根面积、减小根组织密度的方式发展根系，尽可能多地利用浅土区的水分和养分。随着干旱程度的加重，植物在维持浅土区正常生理活动的基础上有限度地增大深土区的生物量；当浅土区比根长、比根面积增大到一定限度时，植物会通过逐渐增大深土区的比根长和比根面积、减小根组织密度的策略来应对干旱胁迫。



Abstract:In heterogeneous habitats of karst areas, the combined effects of soil moisture content, plants' living space and nutrient status may influence the physiological function and growth of plants. In this research, L.perenne was taken as the research material to explore the adaptation of plants to heterogeneous habitats under three scenarios of precipitation (control group: W₀, moderate drought: W₁, and severe drought: W₂) by simulating two microhabitats, namely homogeneous habitat (S-S: shallow-shallow soil) and heterogeneous habitat (S-D: shallow-deep soil). We mainly investigated the following questions: Whether plants in heterogeneous habitats actively improve their adaptation to heterogeneous habitats by actively seeking more resources such as water in deep soil? Whether the rainfall regulate the adaptation strategies? The main findings are as follows. 1) Only in the scenario of severe drought (W₂), plant height, tiller number, above/below-ground biomass and shoot/root mass fraction of L.perenne in heterogeneous habitat were significantly higher than those in homogeneous habitat. There was no significant difference between the two habitats in scenario W₀ and scenario W₁. 2) In scenario W₀, root biomass and root tissue density of L. perenne in the shallow area of heterogeneous habitat were less than those in deep area, and the specific root length and specific root area were larger than those in deep area. With the decrease of precipitation, the proportion of root biomass in shallow area to the whole plant root biomass showed a tendency of declining at the beginning and rising up later. The specific root length and specific root area of the deep area increased gradually, and the root tissue density decreased gradually. The above results indicate that L.perenne showed a stronger ability to resist drought stress in the heterogeneous habitat, and this kind of advantage became more apparent as the drought degree went aggravating. L.perenne in heterogeneous habitat distributed limited biomass to the deep area, at the same time, the root tissue density of the root system in the deep area increased, so that the root system could proliferate in patches with good growth environment, where the plant could obtain a large amount of water and nutrients; while in shallow area, L.perenne made full use of limited resources and develops root systems by increasing specific root length and specific root area, and reducing root tissue density. Water and nutrients in shallow area were utilized as much as possible. With the increase of drought degree, the biomass in deep soil increased to some extent on the premise of maintaining normal physiological activities in the shallow area. When the root length and root area of shallow area increased to a certain limit, plants would respond to drought stress by increasing the specific root length and specific root area of root in deep area and reducing the root tissue density gradually.





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