晋西黄土区典型乔灌木短期水分利用效率对环境因子的响应

doi:10.17521/cjpe.2021.0220

摘要/Abstract

摘要：

为明确晋西黄土区植物的水分利用规律及对半干旱区的适应策略, 提高黄土地区植被建设效益, 该研究对该地区典型乔灌木短期水分利用效率随环境因子的变化进行了探究。以典型乔木油松(Pinus tabuliformis)、刺槐(Robinia pseudoacacia)及其林下灌木黄刺玫(Rosa xanthina)、杠柳(Periploca sepium)为研究对象, 测定叶片可溶性糖稳定碳同位素比值(δ¹³C_leaf)与枝条渗出液稳定碳同位素比值(δ¹³C_branch), 使用δ¹³C_leaf推导计算7-10月叶片尺度下植物短期水分利用效率(WUE_leaf)变化趋势, 使用δ¹³C_branch明确植物光合作用后分馏情况, 确定半干旱区植物在生长季的水分变化规律对环境因子变化的响应。结果表明: (1) 7-10月4种植物δ¹³C_leaf总体呈现降低趋势, δ¹³C_branch呈现先升高后降低趋势。δ¹³C_leaf在种间和生活型中均存在差异。具体表现为: 灌木>乔木, 常绿乔木(油松) >落叶乔木(刺槐)。研究过程中未发现明显的碳同位素在光合作用后发生分馏的情况。(2) 4种植物WUE_leaf在7-8月保持稳定, 9-10月逐渐升高。21.5 ℃、0.9 kPa、52.4%分别为WUE_leaf随温度(T_a)、饱和水汽压差(VPD)、相对湿度(RH)变化的突变点, 突变点之后4种植物WUE_leaf均表现出稳定的变化趋势, 不再随T_a、VPD、RH升高而降低。(3) WUE_leaf与T_a、RH、VPD之间存在显著负相关关系, T_a通过非气孔因素, 即酶的作用改变光合速率, 引起WUE_leaf变化。RH、VPD等水分因子则通过改变气孔开度, 影响蒸腾, 进而改变WUE_leaf。随着土壤含水量(SWC)的升高, WUE_leaf呈现先升高后降低的趋势。油松林和刺槐林在SWC分别达到15%-18%、13%-14%时, WUE_leaf达到最高值。经过混合线性模型(LMM)分析得到, 油松和刺槐WUE_leaf主导环境因子分别为RH和VPD, 黄刺玫和杠柳WUE_leaf主导环境因子均为T_a。该研究得到了黄土地区典型乔灌木生长季水分利用效率变化的规律和主要环境影响因子, 明确了黄土地区植物对气候因子变化的适应机制。

关键词: 水分利用效率, 稳定碳同位素, 可溶性糖, 黄土地区, 混合线性模型

Abstract:

Aims We studied changes in the short-term water use efficiency with environmental factors in typical trees and shrubs of the loess area in West Shanxi. Our objective was to determine the patterns of water use and adaptive strategies in plants of this region, aiming for improving the efficiency of vegetation establishment in the loess area.

Methods Two typical trees, Pinus tabuliformis and Robinia pseudoacacia, and two typical understory shrubs, Rosa xanthina and Periploca sepium, were investigated in this study. Measurements were made on the stable carbon isotope of soluble sugars in leaves (δ¹³C_leaf) and phloem in branches (δ¹³C_branch). δ¹³C_leaf was used to calculated the trend of short-term water use efficiency (WUE_leaf) at the leaf level. δ¹³C_branch was used to determine the carbon fractionation from photosynthesis. We compared the difference in WUE_leaf between species and determined the responses of WUE_leaf to changes in environmental factors.

Important findings From July through to October in the year of investigation, the δ¹³C_leafshowed an overall decreasing trend in the four species, whilst δ¹³C_branch displayed a temporal pattern of “up and down”. δ¹³C_leaf differed among the species and between life forms, in the order of shrubs > trees, and Pinus tabuliformis (an evergreen tree) > Robinia pseudoacacia (a deciduous tree). The WUE_leaf values remained stable from July to August in the four species, and then gradually increased from September to October. Abrupt changes in the WUE_leafvalue occurred at 21.5 °C with temperature (T_a), 0.9 kPa with vapor pressure deficit (VPD), and 52.4% with relative humidity (RH), respectively. Following the abrupt changes, the WUE_leaf value remained steady with further increases in T_a, VPD,and RH in the four species. There were significantly negative correlations between the WUE_leaf value and T_a, RH, and VPD. T_a altered the photosynthetic rate by non-stomatal factors, specifically through the effects on enzymes, causing changes in the WUE_leaf value. The water factor affects transpiration by controlling stomatal opening, and then changes the WUE_leaf value. With increases in soil water content (SWC), the value of WUE_leaf showed a trend of an initial increase and then decreases. The WUE_leaf reached peak value at 15%-18% of SWC in the Pinus tabuliformis stands and 13%-14% in the Robinia pseudoacacia stands. The dominant environmental factors influencing WUE_leaf also differed among species. Linear mixed model (LMM) analysis identified RH as the dominant environmental factor on Pinus tabuliformis, and VPD on Robinia pseudoacacia, respectively; T_a was identified as the dominant environmental factor on both Periploca sepium and Rosa xanthina. This study provides quantitative analysis of water use ability of typical trees and shrubs in the loess area, the internal water consumption mechanism in the growing season, and the major controlling environmental factors, which provides a theoretical basis for the vegetation configuration in this region.

Key words: water use efficiency, stable carbon isotope, soluble sugar, the loess area, linear mixed model

韩璐, 杨菲, 吴应明, 牛云明, 曾祎明, 陈立欣. 晋西黄土区典型乔灌木短期水分利用效率对环境因子的响应. 植物生态学报, 2021, 45(12): 1350-1364. DOI: 10.17521/cjpe.2021.0220

HAN Lu, YANG Fei, WU Ying-Ming, NIU Yun-Ming, ZENG Yi-Ming, CHEN Li-Xin. Responses of short-term water use efficiency to environmental factors in typical trees and shrubs of the loess area in West Shanxi, China. Chinese Journal of Plant Ecology, 2021, 45(12): 1350-1364. DOI: 10.17521/cjpe.2021.0220

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链接本文: https://www.plant-ecology.com/CN/10.17521/cjpe.2021.0220

https://www.plant-ecology.com/CN/Y2021/V45/I12/1350

图/表 12

表1 晋西黄土区典型乔灌木样地基本信息表(平均值±标准差)

Table 1 Basic information of sampling plots for typical trees and shrubs in the loess area of West Shanxi (mean ± SD)

样地编号 Plot No.	胸径 Diameter at breast height (cm)	树高 Tree height (m)	海拔 Altitude (m)	林分密度 Stand density (tree·hm^-2)	坡度 Slope gradient (°)
PTF 1	12.38 ± 3.49	7.04 ± 1.04	1 140	1 050	32
PTF 2	13.38 ± 2.13	7.29 ± 0.96	1 130	1 325	27
PTF 3	13.88 ± 2.47	7.94 ± 1.03	1 120	1 100	29
RPF 1	10.08 ± 4.33	8.29 ± 1.89	1 120	1 675	20
RPF 2	10.68 ± 2.56	9.28 ± 1.20	1 120	1 425	20
RPF 3	9.41 ± 2.71	8.20 ± 2.23	1 130	1 475	21

表2 晋西黄土区灌木基本信息(平均值±标准差)

Table 2 Basic information of shrubs in the loess area of West Shanxi (mean ± SD)

种名 Species	株高 Shrub height (m)	基径 Shrub diameter (cm)	盖度 Coverage (%)	冠幅长度 Crown length (m)	冠幅宽度 Crown width (m)
黄刺玫 Rosa xanthina	1.05 ± 0.19	0.51 ± 0.08	26.60 ± 0.07	2.43 ± 0.13	2.30 ± 0.16
杠柳 Periploca sepium	0.53 ± 0.09	0.35 ± 0.10	16.81 ± 0.04	1.30 ± 0.07	1.23 ± 0.06

图1 晋西黄土区研究区观测期间环境因子变化。由于测定太阳辐射的气象站于9月份进行维修, 故B中太阳净辐射缺失9月部分数据和10月全部数据。

Fig. 1 Variations of environmental factors during the observation period in the study area in the loess area of West Shanxi. Since the weather station for measuring solar radiation was repaired in September, the net solar radiation in B missed part of the data for September and all the data for October. PTF, Pinus tabuliformis forest; RPF, Robinia pseudoacacia forest.

表3 晋西黄土区不同月份之间气象因子单因素方差分析(平均值±标准差)

Table 3 One way ANOVA of meteorological factors in different months in the loess area of West Shanxi (mean ± SD)

月份 Month	温度 Temperature (℃)	n	太阳净辐射 Solar radiation (μmol·m^-2·s^-1)	n	相对湿度 Relative humidity (%)	n	饱和水汽压差 Vapor pressure difference (kPa)	n
7	24.66 ± 2.84^a	22	304.45 ± 117.92^a	22	69.38 ± 7.25^a	22	0.97 ± 0.32^a	22
8	23.14 ± 2.71^b	31	331.81 ± 114.69^a	31	72.37 ± 9.57^a	31	0.81 ± 0.33^ab	31
9	17.37 ± 2.14^c	30	345.06 ± 39.74^a	9	59.19 ± 8.86^b	30	0.82 ± 0.21^b	30
10	13.12 ± 3.10^d	6	-	0	55.94 ± 10.70^b	6	0.65 ± 0.10^b	6

图2 晋西黄土区典型乔灌木不同月份各植物种胞间CO2浓度(Ci)变化。Ps, 杠柳; Pt, 油松; Rp, 刺槐; Rx, 黄刺玫。

Fig. 2 Changes in intercellular CO2 concentration (Ci) of different plant species in different months in typical trees and shrubs in the loess area of West Shanxi. Ps, Periploca sepium; Pt, Pinus tabuliformis; Rp, Robinia pseudoacacia; Rx, Rosa xanthina.

图3 晋西黄土区观测期间不同植物叶片可溶性糖稳定碳同位素比值(δ13Cleaf)与枝条渗出液稳定碳同位素比值(δ13Cbranch)变化情况(平均值±标准差)。

Fig. 3 Changes in the stable carbon isotope of soluble sugars in leaves (δ13Cleaf) and phloem in branches (δ13Cbranch) of different plants during the observation period in the loess area of West Shanxi (mean ± SD).

图4 7-10月晋西黄土区不同植物种叶片、枝条稳定碳同位素比值(δ13C)箱形图。*, p < 0.05; **, p < 0.01。

Fig. 4 Box plots of the stable carbon isotope ratios (δ13C) of leaves and branches for different tree species in the loess area of West Shanxi from July to October. *, p < 0.05; **, p < 0.01.

图5 晋西黄土区观测期间不同植物种短期水分利用效率(WUEleaf)及气孔限制值(Ls)变化(平均值±标准差)。

Fig. 5 Changes in the short-term water use efficiency (WUEleaf) and stomatal limit values (Ls) of different plant species during the observation period in the loess area of West Shanxi (mean ± SD).

图6 7-10月晋西黄土区不同植物种短期水分利用效率(WUEleaf)箱形图。Ps, 杠柳; Pt, 油松; Rp, 刺槐; Rx, 黄刺玫。*, p < 0.05; **, p < 0.01; ***, p < 0.001。

Fig. 6 Box plots of the short-term water use efficiency (WUEleaf) for different tree species in the loess area of West Shanxi from July to October. Ps, Periploca sepium; Pt, Pinus tabuliformis; Rp, Robinia pseudoacacia; Rx, Rosa xanthina. *, p < 0.05; **, p < 0.01; ***, p < 0.001.

图7 晋西黄土区短期水分利用效率(WUEleaf)随日平均气温(Ta)(A)、相对湿度(RH)(B)、饱和水汽压差(VPD)(C)和土壤含水量(SWC)(D)变化趋势(平均值±标准差)。Ps, 杠柳; Pt, 油松; Rp, 刺槐; Rx, 黄刺玫。

Fig. 7 Trends of changes in the short-term water use efficiency (WUEleaf) with temperature (Ta)(A), relative humidity (RH)(B), vapor pressure deficit (VPD)(C) and soil water content (SWC)(D) in the loess area of West Shanxi (mean ± SD). Ps, Periploca sepium; Pt, Pinus tabuliformis; Rp, Robinia pseudoacacia; Rx, Rosa xanthina.

表4 晋西黄土区4种植物短期水分利用效率(WUEleaf)不同混合线性模型中赤池信息准则(AIC)差值(计算模型的AIC与最低AIC的差值)

Table 4 Difference in Akaike information criterion (AIC)(difference between AIC of the calculated model and the lowest AIC) in different mixed linear models for short-term water use efficiency (WUEleaf) of four plant species in the loess area of West Shanxi

模型固定因子 Model fixed factors	油松 Pinus tabuliformis	黄刺玫 Rosa xanthina	刺槐 Robinia pseudoacacia	杠柳 Periploca sepium
T_a + RH	-	0.19	7.99	5.24
P + VPD	-	4.38	3.83	2.34
R_n + VPD	5.51	-	9.75	16.07
P + R_n + VPD	-	5.03	4.13	2.98
T_a + P + SWC	9.83	2.22	-	0.00
T_a + R_n + SWC	2.38	6.11	7.50	5.01
P + RH + SWC	0.00	-	433.28	-
T_a + RH + SWC	-	0.00	8.89	6.80
T_a + VPD + SWC	-	3.16	8.84	4.45
P + VPD + SWC	-	2.73	0.00	2.15
R_n + VPD + SWC	5.43	-	11.74	16.01
RH + VPD + SWC	12.76	12.84	28.29	19.72

表5 晋西黄土区4种植物短期水分利用效率(WUEleaf)不同混合线性模型贡献率比较

Table 5 Comparision of contributions by different linear mixed models for short-term water use efficiency (WUEleaf) of the four plant species in the loess area of West Shanxi

树种 Species	固定因子 Fixed factor	R²	方差解释量占比 Percentage of variance explained (%)	p
黄刺玫 Rosa xanthina	T_a	0.497	54.33	0.000^***
	RH	0.447	48.84	0.837
	SWC	0.005	0.57	0.352
杠柳 Periploca sepium	T_a	0.851	88.74	0.000 ^***
	SWC	0.006	0.57	0.946
	P	0.120	12.50	0.249
油松 Pinus tabuliformis	RH	0.769	84.12	0.000^***
	SWC	0.019	2.06	0.167
	P	0.145	15.91	0.078
刺槐 Robinia pseudoacacia	VPD	0.637	68.91	0.000^***
	SWC	0.044	4.71	0.032^*
	P	0.276	29.78	0.000^***

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