混交林内毛白杨和刺槐根系吸水的动态生态位划分

doi:10.17521/cjpe.2022.0197

摘要/Abstract

摘要：

资源吸收的动态生态位划分研究对于认识植物共存机制具有重要意义, 然而至今对于该领域的理解仍然不足。在2019年生长季内, 对华北平原上的一片毛白杨(Populus tomentosa)-刺槐(Robinia pseudoacacia)成熟混交林进行了同位素和土壤含水率的重复取样, 并于生长季末进行细根取样。通过氢氧稳定同位素方法和贝叶斯混合模型(MixSIAR)确定了树木的季节性吸水模式, 使用Pianka的标准化重叠值判断了毛白杨和刺槐的生态位重叠程度。结果显示: 两个树种都具有深根系, 但是, 毛白杨倾向水平侧根的发育并在浅土层(0-30 cm)分布更高比例的细根, 而刺槐则倾向垂直主根的发育, 在深土层(100-600 cm)分布高比例细根。就整个生长季的平均而言, 毛白杨和刺槐的主要水源均是中层(30-100 cm)和深层土壤水。但是, 浅层和中层土壤水对毛白杨吸水的贡献高于刺槐, 深层土壤水和地下水则反之。在应对干旱和夏季强降雨时, 毛白杨和刺槐表现出完全相反的吸水策略。在旱季, 毛白杨增加中土层的吸水贡献, 而刺槐则提高了对地下水的相对吸水量。当强降雨事件发生时, 毛白杨增加浅土层的吸水贡献, 而刺槐却增加深土层的吸水贡献。总之, 毛白杨和刺槐之间存在细根和吸水生态位互补, 并且吸水生态位互补程度随着季节而变化, 在旱季的吸水生态位互补程度相对高于其他季节。此外, 该研究还表明细根生态位划分不能代表树木的资源吸收划分。该研究为进一步理解植物共存机制提供了证据支撑, 并且为未来应对气候变化的混交林管理策略的制定提供重要参考。

关键词: 动态吸水生态位, 细根生态位, 毛白杨, 刺槐, 混交林, 华北平原

Abstract:

Aims The research on dynamic niche partitioning of soil resource uptake is crucial for the understanding of plant coexistence mechanisms. However, there are still knowledge gaps in the interpretation of this field.

Methods In the growing season of 2019, a mature mixed forest of Populus tomentosa and Robinia pseudoacacia on the North China Plain was repeatedly sampled for water isotopes and soil water content, and fine root sampling was performed at the end of the growing season. Seasonal water uptake patterns of trees were determined by the hydrogen-oxygen stable isotope method and Bayesian mixture model (MixSIAR). The degree of niche overlap between P. tomentosaand R. pseudoacaciawas assessed by Pianka’s normalized overlap value.

Important findings Both tree species have deep root systems. Nevertheless, P. tomentosa tended to develop horizontal lateral roots and a higher proportion of fine roots were distributed in the shallow soil layers (0-30 cm). In contrast, R. pseudoacacia inclined to develop vertical taproots and a high proportion of fine roots were distributed in the deep soil layers (100-600 cm). In terms of the mean values of the whole growing season, the primary water sources for P. tomentosa and R. pseudoacacia were water from the middle (30-100 cm) and deep soil horizons. However, the contribution of water from shallow and middle soil horizons to the water uptake of P. tomentosa was higher than that of R. pseudoacacia, while the opposite was true for deep soil water and groundwater for the two species. Populus tomentosa and R. pseudoacacia showed completely opposite water uptake strategies in response to drought and heavy summer rainfall. During the dry season, P. tomentosa enhanced the water uptake contribution of the middle soil layer, while R. pseudoacacia promoted the relative water uptake from the groundwater. When heavy rainfall events occurred, P. tomentosa increased the water uptake contribution of the shallow soil layer, while R. pseudoacacia increased the water uptake contribution of the deep soil layer. In conclusion, there was niche complementarity in the fine root and water uptake between P. tomentosa and R. pseudoacacia. Furthermore, the degree of niche complementation in water uptake varied with seasons, and the water-uptake niche complementation degree in the dry season was relatively higher than that in other seasons. In addition, the study also showed that the root niche partitioning was not representative of the water uptake partitioning of trees. This study provides support for further understanding of plant coexistence mechanisms, and will provide an important reference for the formulation of future mixed forest management strategies to cope with climate change.

Key words: dynamic water uptake niche, fine root niche, Populus tomentosa, Robinia pseudoacacia, mixed forest, the North China Plain

祝维, 周欧, 孙一鸣, 古丽米热·依力哈木, 王亚飞, 杨红青, 贾黎明, 席本野. 混交林内毛白杨和刺槐根系吸水的动态生态位划分. 植物生态学报, 2023, 47(3): 389-403. DOI: 10.17521/cjpe.2022.0197

ZHU Wei, ZHOU Ou, SUN Yi-Ming, Gulimire YILIHAMU, WANG Ya-Fei, YANG Hong-Qing, JIA Li-Ming, XI Ben-Ye. Dynamic niche partitioning in root water uptake of Populus tomentosa and Robinia pseudoacacia in mixed forest. Chinese Journal of Plant Ecology, 2023, 47(3): 389-403. DOI: 10.17521/cjpe.2022.0197

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链接本文: https://www.plant-ecology.com/CN/10.17521/cjpe.2022.0197

https://www.plant-ecology.com/CN/Y2023/V47/I3/389

图/表 10

图1 华北平原毛白杨和刺槐混交林细根、同位素和土壤含水率取样设计和林分结构示意图。

Fig. 1 Schematic diagram of fine root, isotope, and soil water content (SWC) sampling design and stand structure in a mixed forest of Populus tomentosa and Robinia pseudoacacia on the North China Plain.

图2 2019年华北平原毛白杨和刺槐混交林实验地日降水量和参考蒸散量。

Fig. 2 Daily precipitation and reference evapotranspiration at the experimental site in a mixed forest of Populus tomentosa and Robinia pseudoacacia on the North China Plain in 2019.

图3 刺槐(A)和毛白杨(B)的细根形态。

Fig. 3 Fine root morphology of Robinia pseudoacacia (A) and Populus tomentosa (B).

图4 华北平原毛白杨和刺槐混交林不同水源, 刺槐和毛白杨木质部水的氢氧稳定同位素比值(δD、δ18O)月变化。水平带表示置信区间。

Fig. 4 Monthly variations in hydrogen and oxygen stable isotopes ratio (δD, δ18O) of different water sources, tree xylem water of Populus tomentosa and Robinia pseudoacacia in a mixed forest of P. tomentosa and R. pseudoacacia on the North China Plain. Horizontal bands depict confidence interval.

表1 华北平原毛白杨和刺槐混交林各土层土壤含水率的季节动态(平均值±标准差)

Table 1 Seasonal dynamics of soil water content in each soil layer in a mixed forest of Populus tomentosa and Robinia pseudoacacia on the North China Plain (mean ± SD)

土层 Soil layer (cm)	土壤含水率 Soil water content (%)
土层 Soil layer (cm)	4月 Apr.	5月 May	6月 June	7月 July	8月 Aug.	9月 Sept.	平均值 Mean
0-30	6.60 ± 0.61^bB	3.24 ± 0.37^cC	3.85 ± 0.37^cB	4.19 ± 0.32^cB	8.11 ± 1.23^abB	8.71 ± 1.76^aAB	5.78 ± 2.33^B
30-100	4.99 ± 0.58^cC	4.29 ± 0.20^cdB	3.99 ± 0.35^dB	4.13 ± 0.29^cdB	8.18 ± 0.47^aB	6.61 ± 0.95^bB	5.36 ± 1.64^B
100-600	10.30 ± 0.40^aA	10.20 ± 0.71^aA	7.21 ± 0.35^bA	6.82 ± 0.70^bA	11.60 ± 1.41^aA	11.10 ± 1.12^aA	9.59 ± 2.06^A
平均值 Mean	7.32 ± 2.44^ab	5.94 ± 3.31^bc	5.02 ± 1.67^c	5.05 ± 1.39^c	9.32 ± 2.01^a	8.82 ± 2.28^a

图5 华北平原毛白杨和刺槐混交林不同物种垂直细根分布格局(平均值±标准差)。A, 细根根长密度。B, 累积细根比例。C, 各土层细根比例。*, 不同物种的细根指标差异显著(p < 0.05); β, 细根消减系数, 较大的β值意味着更深的生根剖面。

Fig. 5 Vertical fine root distributions of different species in a mixed forest of Populus tomentosa and Robinia pseudoacacia on the North China Plain (mean ± SD). A, Fine root length density (FRLD). B, Cumulative fine root fraction. C, Fine root fraction in each soil layer. *, significant differences (p < 0.05) in the fine root index between different species; β, the root extinction coefficient, larger values of β imply deeper rooting profiles.

表2 利用线性混合效应模型分析水源和物种对华北平原毛白杨和刺槐混交林不同物种吸水贡献的影响

Table 2 Analyses by linear mixed-effects models for the effects of water source and species on water uptake contributions of different species in a mixed forest of Populus tomentosa and Robinia pseudoacacia on the North China Plain

因子 Factor	月份 Month
	4		5		6		7		8		9		平均值 Mean
	F	p	F	p	F	p	F	p	F	p	F	p	F	p
水源 Water source	1.93	ns	74.47	*	17.78	*	2.50	*	86.42	*	104.66	*	2.35	*
物种 Species	0.01	ns	0.80	ns	0.70	ns	0.10	ns	0.32	ns	0.13	ns	0.01	ns
水源×物种 Water source × species	19.73	*	11.61	*	93.43	*	10.09	*	94.23	*	47.36	*	5.70	*

图6 华北平原毛白杨和刺槐混交林不同物种对不同水源吸水贡献(生长季平均)的影响(平均值±标准差)。A, 浅、中、深层土壤水以及地下水(GW)。B, 垂直吸水模式。*, 不同物种之间的吸水贡献有显著差异(p < 0.05); ns, 没有显著差异(p > 0.05)。根据最小显著差异检验, 不同小写字母表示同一物种不同水源之间吸水贡献差异显著(p < 0.05)。

Fig. 6 Effects of species on water uptake contributions of different water sources (mean values of the growing season) in a mixed forest of Populus tomentosa and Robinia pseudoacacia on the North China Plain (mean ± SD). A, Shallow, middle, and deep soil water and groundwater (GW). B, Vertical water uptake patterns. *, significant differences (p < 0.05) in water uptake contributions between different species; ns, no significant differences between different species (p > 0.05). Different lowercase letters indicate significant differences (p < 0.05) in water uptake contributions among water sources, according to the least significance difference test.

图7 华北平原毛白杨和刺槐混交林不同物种垂直吸水模式的季节动态(平均值±标准差)。GW, 地下水。

Fig. 7 Seasonal dynamics of vertical water uptake patterns of different species in a mixed forest of Populus tomentosa and Robinia pseudoacacia on the North China Plain (mean ± SD). GW, groundwater.

表3 华北平原毛白杨和刺槐混交林分别使用根长密度和吸水贡献计算的生态位重叠指数(平均值±标准差)

Table 3 Niche overlap index calculated using root length density and water uptake contribution in a mixed forest of Populus tomentosa and Robinia pseudoacacia on the North China Plain (mean ± SD)

指标 Index	生态位重叠指数 Niche overlap index
指标 Index	4月 Apr.	5月 May	6月 June	7月 July	8月 Aug.	9月 Sept.	平均值 Mean
吸水贡献 Contribution to water uptake	0.79 ± 0.03^b	0.94 ± 0.06^a	0.83 ± 0.05^b	0.84 ± 0.05^b	0.90 ± 0.03^a	0.94 ± 0.03^a	0.87 ± 0.03^A
根长密度 Fine root length density	-	-	-	-	-	-	0.40 ± 0.06^B

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