Comparison on the Architecture Characteristics of the Root Systems and the Foliar Traits for Three Desert Shrubs Adapted ToArid Habit

多枝柽柳，梭梭，琵琶柴是广泛分布于我国西北荒漠地区的三种耐盐碱旱生植物，也是我国西北荒漠地区植物群落中的优势种和建群种，由这三种植物及其伴生植物构成的荒漠生物群落，在对荒漠的生态保护、防风固沙、牲畜冬春放牧等方面具有重要的生态经济意义。本论文在野外详细调查基础上，研究了古尔班通古特沙漠南缘原始荒漠的三种建群灌木多枝柽柳、梭梭和琵琶柴根系的构型特征以及其与土壤水分的关系，同时调查了它们的生物量并测定了这三种荒漠灌木的比叶面积(SLA)，比叶重（LMA），单位重量叶氮含量(Nmass)和单位面积叶氮含量(Narea)。结果表明：(1)多枝柽柳为轴根疏丛型根系， 根系的分枝形式是叉状分支，根系功能型为深根潜水性根系。根系的最大根幅为8.9m，是其冠幅半径的6.14倍，平均的根幅/冠幅半径比为4.03。根系主要分布在1.4m-3.1m的土层中；梭梭为轴根密丛型根系， 根系的分枝形式也是叉状分支，根系功能型介于深根性和浅根性根系之间。根系具有迂回生长的特点，其最大根幅为4.5m，平均的根幅/冠幅半径比为3.65，根系主要分布在0-90cm土层中；琵琶柴为根蘖密丛型根系，根系的分枝形式也是叉状分支，其根系功能型为浅根性根系。琵琶柴无明显的主根和侧根之分，侧根发达，最长根幅为2.6m，平均的根幅和冠幅之比为4.74，根系主要分布在0-40cm的土层。(2) 多枝柽柳，梭梭，琵琶柴的根冠比均值分别为2.72、1.28、 0.72 。在三种荒漠灌木当中，琵琶柴的叶重比和茎重比最大，多枝柽柳的最小，而梭梭介于两者之间；多枝柽柳有最小的比根面积和比根长，最大的根重比；琵琶柴有着最大的比根面积和比根重，最小的根重比；梭梭介于两者之间。（3）在叶性因子方面，琵琶柴表现为最小的比叶面积，最高的叶氮含量和比叶重，而多枝柽柳的单位重量叶氮含量最低， 梭梭的比叶面积最大。这些事实表明，三种荒漠灌木随着根系分布的由深到浅，即随着土壤水分亏缺的加剧，在叶性因子方面做了一定的适应性调整。在水分为主要限制因子的干旱生境中，根系分布特征在很大程度上决定了灌木的叶性策略。同时研究表明，荒漠灌木在抗旱和生长之间存在相对平衡的关系。Tamarix ramosissima Ledeb．，Haloxylon ammodendron (C．A．Mey)and Teaumuria soongorica(Pal1．)Maxim．were three primitive and xeric desert shrubs tolerating saline and alkaline which occured widely the arid areas in the northwest of our country and they were also dominant species of the plant community there．The desert community consist of three shrubs and their associated plants were important for ecological conservation，defending wind and retaining sand， livestock graze etc ，This paper based on detailed investigation in the field，the three shrubs T. ramosissimalateral，H. ammodendron and R. soongorica，which growing and dominanting in the southern boundary of the Garbantunggut desert，were wholly excavated for studying architecture characteristics of their root systems，and their relations with soil water content．At the same time， we also measured the specific leaf area (SLA)，leaf mass per area(LMA)，mass-based (Nmass) and area-based(Narea) leaf nitrogen concentration．The results showed as follows：(1) The main root of T. ramosissimalateral was a axial root and its root system extended to a extraordinarily deep and broad range loosly．Its root branching was dichotomous-like．T．ramosissima was a typical phreatophyte，The maximal radial of T. ramosissima’s roots on horizontal spread was 8.9m which was that of canopy radius 6.14 times．The average root crown：canopy radius was 4.03，The most of lateral roots of T. ramosissima distributed in the depth interval 1.4 -3.1m. H. ammodendron had a axial root，too ，but its roots distributed compactly in soil and the root branching was also dichotomous-like. Its functional type of root system between phreatophyte and shallow root type. The root system waves its way through the soil. The longest horizontal lateral root of H. ammodendron was 4.5m which was that of canopy radius 3.46 times. The average root crown：canopy radius was 3．65. The lateral roots of H. ammodendron mainly occured in the depth of 0-0.9m.Because the roots of T.ramosissima tilleried abundantly，its taproot was hardly distinguished from lateral roots. Lots of lateral roots distributed around the taproot like a half circle，root branching was also dichotomous-like，its functional type of root system was shallow root type. R. soongorica’s roots occured concentratedly in the depth of 0-0.4m，the roots in the soil layer exceeded 60% of entire root system，on the contrary，there was no root systems deeper than 0.7 m. The most of the maximal radial of R. soongorica’s root system on horizontal spread was 2.6m which was that of canopy radius 8.67 times， The average root crown：canopy radius was 4.74．(2)the root:shoot ration of T.ramosissima，H.ammodendron and R.soongorica was 2.72，1.28，0.72 respectively．Among the three species，the LMR and RMR of R. soongorica were the largest， that of T. ramosissima were the smallest，H.ammodendron between them. the SRA and SRL of the T. ramosissima were the smallest，the RMR of T. ramosissima was the largest， the SRA and SRL of R. soongorica were the largest， the RMR of R. soongorica was the smallest， H. ammodendron between them.(3)For foliar traits，R. soongorica has the smallest SLA， the highest Nmass and LMA ，the Nmass of T.ramosissima was the smallest， the SLA of H. ammodendron was the largest．These factors indicated that with the distribution of root systems of shallow to deep of the three species in the soil section，namely，when soil moisture constant was becoming decrease，plant of different functional types employed certain adaptive adjustment in order to resist water stress．In other words，in the arid habitat where water was the most limited factor，the architecture characteristics of the root systems of three shrubs determined their foliar strategy in remarkable extent．The results also showed that there was a balance between the growth and drought tolerance for the three desert shrubs

三种荒漠灌木根系的构形特征与叶性因子对干旱生境的适应性比较

以古尔班通古特沙漠南缘原始荒漠的三种建群灌木多枝柽柳、梭梭和琵琶柴为研究对象,采用挖掘法调查其根系构性特征及其与土壤水分的关系,同时测定其比叶面积(SLA),比叶重(LMA),单位重量叶氮含量(Nmass)及单位面积叶氮含量(Narea)。结果表明,三种荒漠灌木的根系分属不同的功能型,多枝柽柳是深根潜水性植物,琵琶柴是浅根性植物,而梭梭介于两者之间。而且,三种荒漠灌木随着根系分布的由深到浅,即随着土壤水分亏缺的加剧,在叶性因子方面做了一定的适应性调整。这些事实表明,在水分为主要限制因子的干旱生境中,根系构型特征在很大程度上决定了灌木的叶性策略。同时研究表明,荒漠灌木在抗旱和生长之间存在相对平衡的关系

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