西藏高寒草原群落植物根系属性在降水梯度下的变异格局

doi:10.17521/cjpe.2018.0140

摘要/Abstract

摘要：

根系功能属性及其变异性能够介导物种共存及环境适应策略, 但强烈的环境约束作用能够引起不同物种间根系属性的趋同性。为了研究西藏高寒草原群落中植物根系属性变异规律, 并阐明不同物种资源获取和适应策略的多样性, 该文对西藏高寒草原不同的环境梯度进行了研究。作者自东向西沿着降水梯度在那曲、班戈和尼玛3个自然草原群落进行群落调查, 并采集了共计22种植物。测定了每种植物的一级根直径、一级侧根长度和根系分支强度3个关键根系属性。结果表明: 在西藏高寒草原群落中, 不同物种根系直径普遍较小, 且种间变异非常小(22.76%), 其中86%的物种一级根直径集中在0.073 mm到0.094 mm之间; 相较于直径较粗的物种, 直径越细的物种分支强度越高, 侧根越短。在群落尺度上, 植物主要通过增加根系直径、侧根长度, 降低分支强度的方式来适应水分的减少; 而在物种尺度上, 植物适应水分变化的策略则呈现多样性。

关键词: 属性变异, 适应策略, 根系分支, 根直径, 根长度, 高寒草原

Abstract:

Aims Root functional traits and their variations mediate coexistence and adaptive strategy of plant species. Yet, strong environmental constraints may induce convergence of root traits among different plant species. To study the variations of root traits and clarify the diverse adaptive strategies across plant species, we sampled three alpine grasslands along a precipitation gradient in the Xizang Plateau.
Methods In three grassland communities along a precipitation gradient: Nagqu, Baingoin and Nyima from east to west of Xizang Plateau, we collected 22 coexisting plant species and measured three key root traits: 1st-order root diameter, 1st-order lateral root length and root branch intensity.
Important findings The main results showed that: (1) the root of plants in the alpine grassland was generally thin, and the interspecific variation was also small (22.76%); (2) the root diameter of 86% plant species was in the range from 0.073 mm to 0.094 mm. Compared with the thick-root species, thin-root species had a higher root branching intensity, but shorter lateral root length. In addition, at community-level, plants mainly increased root diameter and lateral root length, but reduced root branching intensity to adapt to the decreasing precipitation; while at species-level, the plant species exhibited diverse adaptive strategies along the precipitation gradient.

Key words: trait variation, adaptive strategy, root branching, root diameter, root length, alpine grassland

周玮, 李洪波, 曾辉. 西藏高寒草原群落植物根系属性在降水梯度下的变异格局. 植物生态学报, 2018, 42(11): 1094-1102. DOI: 10.17521/cjpe.2018.0140

ZHOU Wei, LI Hong-Bo, ZENG Hui. Variations of root traits in three Xizang grassland communities along a precipitation gradient. Chinese Journal of Plant Ecology, 2018, 42(11): 1094-1102. DOI: 10.17521/cjpe.2018.0140

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链接本文: https://www.plant-ecology.com/CN/10.17521/cjpe.2018.0140

https://www.plant-ecology.com/CN/Y2018/V42/I11/1094

图/表 7

表1 西藏高寒草原群落根系样地基本信息

Table 1 Basic information of the sampling sites of root in Xizang alpine grassland communities

地点 Site	经纬度 Latitude and longitude	年平均气温 Mean annual temperature (℃)	年降水量 Mean annual precipitation (mm)	海拔 Elevation (m)	土壤氮含量 Soil N (%)	土壤碳含量 Soil C (%)	土壤碳氮比 Soil C:N
那曲 Nagqu	31.65° N, 92.02° E	-2.2	445	4 600	0.193	1.965	22.97
班戈 Baingoin	31.43° N, 90.03° E	-1.2	329	4 700	0.117	1.081	13.93
尼玛 Nyima	32.08° N, 86.90° E	-3.1	286	4 780	0.115	2.062	18.24

图1 22种高寒草原植物的谱系发育关系及根系属性的变异。

Fig. 1 Variations of phylogeny and traits among the 22 plant species in the alpine grassland.

表2 西藏高寒草原22种植物的根系属性变异情况

Table 2 Summary of the three root traits for 22 species in Xizang alpine grassland

根属性 Root trait	最小值 Min.	最大值 Max.	平均值 Mean	变异系数 Coefficient of variation (%)
一级根直径 1st-order root diameter (mm)	0.073	0.142	0.088	22.76
一级根长度 1st-order root length (mm)	0.335	5.239	1.541	80.19
根系分支强度 Root branching intensity (No.cm^-1)	1.119	12.041	4.439	61.05

表3 西藏高寒草原22种植物去除种系发生信号(右上)与未去除种系发生信号(左下)时3个根属性间的Pearson相关性

Table 3 Pearson correlations with (top right) and without (bottom left) phylogenetically independent contrasts for root traits across 22 species in Xizang alpine grassland

根属性 Root trait	一级根直径 1st-order root diameter	分支强度 Root branching intensity	一级根长度 1st-order root length
一级根直径 1st-order root diameter		-0.008^ns	0.672^**
根系分支强度 Root branching intensity	-0.432^*		-0.139^ns
一级根长度 1st-order root length	0.728^**	-0.573^**

图2 不同降水梯度上的西藏高寒草原3个草原群落加权后的根系属性。

Fig. 2 Community-weighted root traits of the three grasslands along the precipitation gradient in Xizang alpine grassland.

图3 西藏高原3个草原类型中7个共有物种(同时出现在两个或三个地区)的根系属性(平均值+标准误差)。Ad, 纤杆蒿; Ts, 西藏三毛草; Lp, 弱小火绒草; Sp, 紫花针茅; Pb, 二裂委陵菜; Om, 小叶棘豆; Hs, 半卧狗娃花。

Fig. 3 Root trait mean values of seven regionally common species (appearing in two or three sites at the same time) at three grassland sites (mean + SE) in Xizang alpine grassland. Ad, Artemisia demissa; Ts, Trisetum spicatum; Lp, Leontopodium pusillum; Sp, Stipa purpurea; Pb, Potentilla bifurca; Om, Oxytropis microphylla; Hs, Heteropappus semiprostratus.

图4 西藏高原3个草原类型7个共有物种根系属性随水分变化的平均百分比。Hs, 半卧狗娃花; Om, 小叶棘豆; Pb, 二裂委陵菜; Sp, 紫花针茅; Lp, 弱小火绒草; Ts, 西藏三毛草; Ad, 纤杆蒿。

Fig. 4 The average percentage of root traits of seven regionally common species (appearing in two or three sites at the same time) to water stress at three grassland sites in Xizang alpine grassland. Ad, Artemisia demissa; Ts, Trisetum spicatum; Lp, Leontopodium pusillum; Sp, Stipa purpurea; Pb, Potentilla bifurca; Om, Oxytropis microphylla; Hs, Heteropappus semiprostratus.

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