模拟喀斯特生境土壤干旱胁迫对蚬木苗木的影响

为揭示喀斯特土壤干旱环境下植物的生长及形态适应性,模拟构建了喀斯特"土壤层-岩石层-岩溶水层"水分供应装置,以2年生蚬木(Excentrodendron hsienmu)苗木为试验材料,研究了岩溶水层岩溶水分(有/无水分)和土壤水分2个因素对蚬木幼苗生长及形态发育的影响。结果表明:岩溶水分和土壤水分极显著影响蚬木幼苗生长,苗木净生长量随土壤干旱增强显著下降,岩溶水层有水处理下(W)苗木净生长量显著高于无水处理(N)。两者极显著影响着苗木总生物量及茎、叶生物量,岩溶水分极显著影响根生物量;生物量随干旱胁迫增强显著下降,W处理的显著高于N处理。土壤水分极显著影响着根冠比和根、茎生物量比,岩溶水分显著影响茎生物量比,因素间交互作用显著影响根冠比和根生物量比、极显著影响着茎生物量比。中度和重度干旱下根冠比及根生物量比显著高于对照,茎生物量比随干旱增强显著下降,W处理茎生物量比显著高于N处理。两个因素极显著影响苗木地径、株高、根长等,岩溶水分显著影响叶片数和一级分枝数、土壤水分的影响达极显著水平,因素间交互作用对地径产生显著影响、且极显著影响叶面积。蚬木幼苗生长受土壤水分条件影响较大,土壤干旱胁迫下表现为生长下降、生物量分配和形态发育发生改变等适应策略,岩溶水分对苗木的影响与土壤水分条件密切相关。

Effect of Drought Stress on Excentrodendron hsienmu Seedlings under Simulating Karst Environment

To explore plant growth and morphological adaptive strategy to karst soil drought environment, we set up a water sup-ply device combining with a simulated karst structure comprising soil, limestone, and epikarst layer.We studied the growth, biomass accumulation and allocation, and morphology of 2-a Excentrodendron hsienmu seedlings under the simula-ted karst environment.A two-factor design, having water or having no water in epikarst layer ( epikarst layer water) and four levels of soil water condition, was performed to analyze the impacts on E.hsienmu seedlings.Both epikarst layer water and soil water significantly affected the growths of leaf, ground diameter, and height of seedlings.Values of net growth were significantly decreased with the increasing of soil drought stress, which in treatment with epikarst layer having water ( W treatment) were greatly higher than those in treatment with epikarst layer having no water (N treatment).They also had very significant influence on the total biomass, leaf and stem biomass, and epikarst layer water affected the root biomass greatly.Total biomass and biomass of root, stem, and leaf were greatly decreased with the increasing of soil drought stress, which in W treatment were significantly higher than those in N treatment.Soil water markedly affected the root-shoot ratio, root and stem mass ratio, and epikarst layer water significantly impacted stem mass ratio.There was a significant epikarst layer water×soil water interaction on root-shoot ratio and root mass ratio, and very significant on stem mass ratio.The root-shoot ratio and root mass ratio in moderate and severe drought stress were greatly higher than those in control, while the stem mass ratio was markedly decreased with the increasing of drought stress.The stem mass ratio in W treatment was greatly higher than that in N treatment.Both of the two factors very significantly affected the ground diameter, height, root length, cumulative length of primary branch, and leaf area of E.hsienmu seedlings.Epikarst layer water had great influ-ence on the number of leaf and primary branch, while soil water had very significant effect.There was also a significant epikarst layer water×soil water interaction on ground diameter, and very significant on the leaf area.The values of morpho-logical characters were basically decreased with the increasing of drought stress, which in W treatment were greatly higher than those in N treatment.The results indicated that the growth of E.hsienmu seedlings was mainly affected by soil water condition, seedlings growth decline, biomass allocation and morphology changed under soil drought stress, and the influ-ence of epikarst layer water on E.hsienmu seedlings was closely related to soil water.