基于容器分区处理探究黑麦草生长对喀斯特不同土壤生境和水分的响应

为了探究不同水分条件下喀斯特地区分布不均、厚薄不一土壤小生境对禾本科草本植物生长的影响,用3种不同深度的容器(对照深度CK,深土D和浅土S)两两组合为6种复合容器(CK-CK、CK-S、CK-D、D-D、S-D和S-S)以实现容器分区,研究了黑麦草的根系生长、生物量积累及其分配特征。结果表明:1)在水分充足(W_0)条件下,组合了浅土容器和深土容器的处理中,黑麦草的根系生长(根长、根直径、根表面积和根生物量)均低于对照容器(CK-CK),且有浅土容器的组合处理(S-S,S-D,CK-S)受抑制程度大于有深土容器的组合处理(CK-D,D-D);当水分含量降低后,即中水(W_1)和低水(W_2)条件下,有深土容器的组合D-D和(或)CK-D]根系生长与对照相比显著增加,而有浅土容器的组合S-S和(或)CK-S]根系生长与对照相比显著降低。2)对比同一处理不同容器分区中黑麦草生长指标发现,在水分充足情况下,深土容器和浅土容器均会抑制植物生长,而当水分减少,S区根系生长被严重抑制,但D区根系增长优势明显。3)水分充足条件下,根冠比未受到显著影响;当水分降低时,组合了深土容器的处理根冠比均有升高的趋势,组合了浅土容器的处理根冠比有降低趋势。由此可见,不同土壤生境带来的物理空间限制会影响植物根系生长和生物量积累与分配,但水分的减少会改变根系生长及生物量积累对不同土壤生境的响应:在水分充足时,土壤物理空间是影响根系生长和生物量积累与分配的主要因子,黑麦草主要发展浅层根系。而当水分减少时,黑麦草根系在浅层土壤中无法获取供给生长代谢活动的足量水分,更倾向于将有限的有机物分配给根,通过根系伸长、表面积和体积增大、直径增粗等策略加强水分吸收,从而增强对干旱的抗逆性,提高对土壤和水分异质性的适应。

Growth response of Lolium perenne L. under different soil habitats and water conditions based on container partition in a karst area

Bare rock, uneven soil thickness, and drought have resulted in a harsh habitat in karst areas. Therefore, plant growth in these areas requires more advanced adaptation strategies. To explore the effect of unique soil habitats on herbaceous plant (Gramineae) growth under different water conditions in a karst area, we selected three container typescontrol (CK), deep (D), and shallow (S)] for six soil treatments in the following combinations:CK-CK, CK-S, CK-D, D-D, S-D, and S-S. Root growth, biomass accumulation, and root spatial distribution of Lolium perenne L. in different water levels (W₀, W₁, and W₂) were observed. The results showed 1) with sufficient water (W₀), the root length, diameter, surface area, and biomass of L. perenne in the compound containers that contained S or D were lower than that of the control (CK-CK). The degree of inhibition of L. perenne in treatment combined with shallow soil containers (S-S, S-D, CK-S) was greater than that in treatment combined with deep soil containers (CK-D, D-D). The root growth in treatments containing S (S-S, S-D, CK-S) were more inhibited than those in the treatments containing D (CK-D, D-D). With reduced water content (W₁ and W₂), root growth in the compound containers that contained D (D-D and/or CK-D) was significantly higher than that of the control, whereas it was significantly lower in the containers containing S (S-S/CK-S). 2) Comparing root growth in two sides of one compound container, we found that under W₀, both deep and shallow soil inhibited plant growth. Under W₁ and W₂, root growth of the S sides was inhibited severely. However, root growth occurred in the D sides. 3) Under W₀, the root-to-shoot ratio was not affected by soil space. With decrease in the water content, the root-to-shoot ratio increased in the D compound containers, whereas it decreased significantly in the S compound containers. Thus, the physical space limitation of different soil habitats affected plant root growth and biomass accumulation and distribution; however, the decrease of water content could change these responses:with sufficient water, soil physical space was the main factor affecting root growth and biomass accumulation and distribution. Correspondingly, L. perenne mainly developed shallow roots. However, when water was reduced, L. perenne roots could not obtain enough moisture in the shallow soil to supply metabolic growth activity. Therefore, L. perenne generally distributed limited organic matter to the roots and strengthened water absorption through root elongation, surface area and volume increase, and diameter thickening, to enhance drought resistance and improve adaptability to shallow soil and drought.