西藏紫花针茅叶功能性状沿降水梯度的变化

doi:10.3724/SP.J.1258.2012.00136

摘要/Abstract

摘要：

植物叶功能性状与环境因子的关系是近10年来植物生态学的研究热点。该文以广泛分布于青藏高原干旱、半干旱草地的优势植物种紫花针茅(Stipa purpurea)为研究对象, 沿降水梯度(69-479 mm)系统测定了日土、改则、珠峰、当雄和纳木错5个调查地点紫花针茅比叶面积(SLA)、单位重量和单位面积叶氮含量(N_mass, N_area)、叶密度和厚度等叶功能性状以及土壤全氮含量等因子, 试图验证干旱胁迫地区同一物种内SLA-N_mass关系沿降水梯度的策略位移现象是否具有普遍性, 并对是否出现策略位移现象提出可能的解释。研究结果表明: 1) SLA和N_mass与生长季温度和降水以及土壤全氮含量均没有显著关系, SLA与N_mass的关系在干旱半干旱区(年降水/蒸发比< 0.11)与半湿润区(年降水/蒸发比> 0.11)之间并没有出现典型的位移现象; 2)叶密度是决定半湿润区SLA变化的主导因子, 而叶厚度则是干旱半干旱区SLA变化的控制因子, 两者与SLA均呈负相关, 随着温度增加或降水减少, 叶厚度增加而叶密度降低, 导致SLA随温度和降水变化不明显; 3)半湿润区的叶密度增加引起N_area增加, 而干旱半干旱区的叶厚度增加并没有造成N_area的显著变化, 导致N_area沿降水梯度没有显著变化; 4)紫花针茅地上生物量与N_area具有显著正相关关系, 表明N_area的增加有助于提高植被生产力。结果表明, 在干旱胁迫下, 植物通过增加叶厚度来维持不变的N_area可能有助于保持与较湿润地区相似的光合生产和水分利用效率。叶厚度和叶密度对比叶面积的相对影响在干旱半干旱区与半湿润区之间发生转变, 这为进一步检测高寒草地植被的水分限制阈值提供了新思路。

关键词: 叶密度, 叶氮含量, 叶厚度, 比叶面积, 紫花针茅, 策略位移

Abstract:

Aims Stipa purpurea is the dominant species in alpine arid and semi-arid grasslands on the Tibetan Plateau. Our objectives are to determine if this species exhibits a strategy shift in its specific leaf area (SLA) to nitrogen (N) concentration relationship along a rainfall gradient and to detect possible effects of environmental factors on related leaf traits.
Methods We investigated variations in leaf traits of S. purpurea associated with climatic and soil factors along an east-west transect with a rainfall gradient (69-479 mm) but similar altitudes (4 300-4 700 m). Five locations from east to west are Damxung, Namco, Gêrzê, Mount Qomolangma and Rutog. We measured SLA, mass- and area-based leaf N concentration (N_mass, N_area), leaf density and thickness and soil total N along the transect.
Important findings In pooled data, SLA and N_mass varied little with the growing season mean temperature and precipitation and the soil total N concentration. The SLA-N_mass relationship in S. purpurea did not shift between the semi-humid areas (ratio of rainfall to evaporation > 0.11) and the arid and semi-arid areas (ratio < 0.11), although there was a positive correlation between SLA and N_mass across the five locations. Variation in SLA was mainly determined by leaf density in the semi-humid areas and by leaf thickness in the arid and semi-arid areas; both were negatively correlated with SLA. With increasing temperature or declining precipitation, leaf density decreased and leaf thickness increased, leading to non-significant relationships between SLA and climatic factors. The increase of leaf density in the semi-humid areas was correlated with the increase of N_area, but the increase of leaf thickness in the arid and semi-arid areas did not lead to change of N_area, resulting in unchanged N_area along the rainfall gradient. A positive correlation was detected between aboveground biomass and N_area in S. purpurea, indicating that increased N_area may increase plant productivity. Our findings suggest that alpine plants in arid and semi-arid areas may maintain a constant N_area by increased leaf thickness in order to achieve a similar photosynthetic productivity and water use efficiency compared to the relatively humid areas. The relative impacts of leaf density and leaf thickness on SLA shifted between the semi-humid areas and the arid and semi-arid areas, which may provide insight in detecting the threshold of water limitation in alpine grasslands.

Key words: leaf density, leaf nitrogen concentration, leaf thickness, specific leaf area, Stipa purpurea, strategy shift

胡梦瑶, 张林, 罗天祥, 沈维. 西藏紫花针茅叶功能性状沿降水梯度的变化. 植物生态学报, 2012, 36(2): 136-143. DOI: 10.3724/SP.J.1258.2012.00136

HU Meng-Yao, ZHANG Lin, LUO Tian-Xiang, SHEN Wei. Variations in leaf functional traits of Stipa purpurea along a rainfall gradient in Xizang, China. Chinese Journal of Plant Ecology, 2012, 36(2): 136-143. DOI: 10.3724/SP.J.1258.2012.00136

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链接本文: https://www.plant-ecology.com/CN/10.3724/SP.J.1258.2012.00136

https://www.plant-ecology.com/CN/Y2012/V36/I2/136

图/表 7

表1 研究地点的地理位置及气候因子

Table 1 Locations and climatic factors of study sites

研究地点 Study site	纬度 Latitude (°)	经度 Longitude (°)	海拔 Altitude (m)	年平均气温 AT (℃)	生长季平均气温 GST (℃)	年降水量 AP (mm)	生长季降水量 GSP (mm)	年降水量/年蒸发量 Ratio of rainfall to evaporation
当雄 Damxung	30.50	91.05	4 480	1.66	9.78	479	402	0.25
纳木错 Namco	30.77	90.98	4 730	-0.40	7.99	404	338	0.27
珠穆朗玛峰 Mount Qomolangma	28.21	86.56	4 276	2.50	10.73	282	271	0.10
改则 Gêrzê	32.30	84.08	4 437	0.03	10.39	171	154	0.03
日土 Rutog	33.40	79.72	4 286	0.50	11.64	69	59	0.07

图1 西藏紫花针茅比叶面积(SLA)和单位重量叶氮含量(Nmass)的关系。

Fig. 1 Relationships between specific leaf area (SLA) and mass-based leaf N concentration (Nmass) in Stipa purpurea of Xizang.

表2 五个研究地点紫花针茅叶功能性状与环境因子的线性关系

Table 2 Correlation coefficients for linear relationships between climatic factors and leaf functional traits of Stipa purpurea in pooled data across the five study sites

环境因子 Environmental factor	叶性状 Leaf trait
环境因子 Environmental factor	比叶面积 SLA (cm·g^-1)	单位重量叶氮含量 N_mass(mg·g^-1)	单位面积叶氮含量 N_area (g·m^-2)
生长季平均气温 Mean air temperature in growing season (℃)	0.21	-0.29	-0.46^**
年平均气温 Annual mean air temperature (℃)	0.21	-0.27	-0.36^*
生长季降水量 Precipitation in growing season (mm)	0.01	0.20	0.24
年降水量 Annual precipitation (mm)	0.01	0.21	0.28
土壤全氮含量 Total N in soil (mg·g^-1)	0.19	0.18	0.50^**

图2 紫花针茅比叶面积(SLA)分别与叶厚度(A)和叶密度(B)的关系。图A、B中趋势线分别基于干旱半干旱区和半湿润区的数据。

Fig. 2 Relationships of specific leaf area (SLA) with leaf thickness (A) and leaf density (B) of Stipa purpurea. Trends lines are for the data from the arid and semi-arid areas in Fig. 2A and the semi-humid areas in Fig. 2B, respectively.

图3 紫花针茅叶密度(A, B)、叶厚度(C, D)与生长季平均气温和降水量的关系。直线为所有观测数据趋势线。

Fig. 3 Relationships of (A, B) leaf density and (C, D) leaf thickness of Stipa purpurea with growing season mean temperature and precipitation. Trends lines are for all pooled data.

图4 紫花针茅单位面积叶氮含量(Narea)分别与叶密度(A)和叶厚度(B)的关系。直线为半湿润区趋势线。

Fig. 4 Relationships of area-based leaf N concentration (Narea) with leaf density (A) and leaf thickness (B) of Stipa purpurea. Trends lines are for the data from the semi-humid areas.

图5 紫花针茅单位面积叶氮含量(Narea)与地上生物量的关系。

Fig. 5 Relationships between area-based leaf N concentration (Narea) and aboveground biomass of Stipa purpurea.

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