大连4种城市绿化乔木树种夜间液流活动特征

doi:10.3773/j.issn.1005-264x.2010.05.007

摘要/Abstract

摘要：

夜间液流有助于树木物质运输及其体内水分的补充(water recharge), 它不仅对植物的生长发育具有重要的生理生态学意义, 而且对大尺度植物蒸腾耗水的估算可能产生重要影响。2008年6月1日至8月31日, 以热扩散探针(thermal dissipation probe, TDP)技术对大连市劳动公园内的雪松(Cedrus deodara)、大叶榉(Zelkova schneideriana)、丝棉木(Euonymus bungeanus)和水杉(Metasequoia glyptostroboides) 4种乔木树种的不同径阶样木树干边材液流进行了测定, 并结合同步土壤水分与小气候观测结果分析了树木夜间(18:00至次日5:00)液流特征。实验结果表明, 树木普遍存在可感夜间液流, 夜间液流总量占观测期液流总量的比例在样木个体间呈现显著差异, 其变化范围为0.44%-75.96%; 观测期雨天夜间液流波动活跃, 显著高于晴天, 其单日夜间液流总量可持平, 甚至高于日间液流。相关分析表明: 水汽压亏缺(vapor pressure deficit, VPD)和风速的变化与夜间蒸腾显著相关, 它们能够较好地解释液流变化(R² > 0.6); 树木夜间液流主要用于夜间蒸腾和自身水分补充, 夜间液流现象主要发生在前半夜, 后半夜液流平稳且极接近0, 夜间液流量与相应的日间流量(R² = 0.356, p = 0.00)及胸径(R²_Spearman > 0.80)显著相关, 说明植物本身的结构和生理特点也是影响树木夜间液流的重要因子。单株样木夜间液流占全天总蒸腾量的比例低于14.4%, 如不考虑夜间液流的影响, 根据日间液流通过尺度扩展推算的森林生态系统年蒸腾量可能偏低。

关键词: 环境因子, 夜间液流, 热扩散液流测定技术, 城市树种

Abstract:

Aims Nocturnal sap flow is a driving force not only for chemical transport and nutrient movement within trees, but also for water recharge caused by diurnal transpiration loss. Therefore, it is both ecologically and physiologically significant for estimating tree and stand transpiration at larger spatial and longer temporal scales. Our objective was to analyze nocturnal sap flow (18:00-5:00 next morning) and its biophysical controls in four tree species (Cedrus deodara, Zelkova schneideriana, Euonymus bungeanus and Metasequoia glyptostroboides) in Laodong Park in Dalian, China.

Methods During June 1-August 31, 2008, we measured sap flow of twelve urban trees of four species and three diameter at breast height (DBH) classes of each species continuously by thermal dissipation probes, soil moisture by ECH2O soil moisture probe and microclimate data by an automatic weather station. SPSS 13.0 was used for statistical analysis of sap flow and environmental factors.

Important findings Nocturnal sap flow was measured in all sampled trees, but varied from 0.44% to 75.96% of total daily water consumption. Nocturnal flow was larger and more active on rainy days than that on sunny ones, to the extent that it equaled or exceeded the diurnal volume. Vapor pressure deficit and wind speed were significantly correlated with nocturnal water movement (R² > 0.6), which could provide an explanation for nocturnal transpiration. Nocturnal sap flow mainly contributed to nocturnal transpiration and water recharge. It peaked before midnight and dropped to nearly zero afterwards. Furthermore, nocturnal sap flow was remarkably correlated with diurnal sap flow (R² = 0.356, p = 0.00) and DBH (R²_Spearman > 0.80), substantiating the important role of specific structural and physiological characteristics. Nocturnal sap flow of individuals accounted for an average of < 14.4% of the total transpiration volume. Total water consumption of a forest ecosystem scaled up by daytime sap flux measurements can be underestimated without integration of nocturnal sap flux.

Key words: environmental variables, nighttime sap flow, thermal dissipation probe (TDP), urban trees

陈立欣, 张志强, 李湛东, 张文娟, 张晓放, 董克宇, 王国玉. 大连4种城市绿化乔木树种夜间液流活动特征. 植物生态学报, 2010, 34(5): 535-546. DOI: 10.3773/j.issn.1005-264x.2010.05.007

CHEN Li-Xin, ZHANG Zhi-Qiang, LI Zhan-Dong, ZHANG Wen-Juan, ZHANG Xiao-Fang, DONG Ke-Yu, WANG Guo-Yu. Nocturnal sap flow of four urban greening tree species in Dalian, Liaoning Province, China. Chinese Journal of Plant Ecology, 2010, 34(5): 535-546. DOI: 10.3773/j.issn.1005-264x.2010.05.007

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图/表 11

表1 样木统计表

Table 1 Statistics of sample trees

树种 Species	样木编号 No. of sample trees	胸径 DBH (cm)	冠幅 Crown area (m²)	树高 Tree height (m)	边材面积 Sapwood area (cm²)
雪松 Cedrus deodara	C1	13.60	10.18	6.10	26.42
	C2	17.20	16.61	6.70	30.19
	C3	21.00	22.90	8.30	45.36
大叶榉 Zelkova schneideriana	Z1	10.00	13.85	4.70	11.34
	Z2	14.20	18.10	5.30	20.11
	Z3	17.60	24.63	5.90	25.52
水杉 Metasequoia glyptostroboides	M1	14.60	2.01	10.30	16.62
	M2	18.80	5.31	11.60	43.01
	M3	24.60	7.07	12.90	50.27
丝棉木 Euonymus bungeanus	E1	10.40	22.90	5.20	36.32
	E2	13.50	34.21	5.40	51.53
	E3	16.60	47.78	6.30	66.48

图1 典型晴天(2008年8月9日)天气条件下植物液流日进程。DBH, 胸径。

Fig. 1 Diurnal sap flow pattern in a typical sunny day (August 9th, 2008). DBH, diameter at breast height; Js, sap flux density.

图2 典型雨天(2008年8月22日)条件下植物液流日进程。DBH, 胸径。

Fig. 2 Diurnal sap flow pattern in a typical rainy day (August 22nd, 2008). DBH, diameter at breast height; Js, sap flux density.

图3 连续典型晴天天气下植物夜间液流变化规律。DBH, 胸径。

Fig. 3 Nocturnal sap flow variation in consecutive typical sunny days. DBH, diameter at breast height; Js, sap flux density.

图4 2008年8月5日至30日样木夜间液流总量与土壤体积含水量关系图。 A, 雪松-大叶榉样地。B, 水杉-丝棉木样地。

Fig. 4 Daily accumulated nocturnal sap flow of sampled trees versus soil volumetric water content from August 5th to 30th, 2008. A, Cedrus deodara-Zelkova schneideriana plot. B, Metasequoia glyptostroboides-Euonymus bungeanus plot.

图5 2008年8月5日至30日样木夜间液流总量与降水的关系。柱状图代表降水量, 曲线反映夜间液流总量。

Fig. 5 Relationships between precipitation and sum of nocturnal sap flow of sampled trees. Vertical bars represent precipitation, while multiple lines indicate sum of nocturnal sap flow.

表2 树木夜间液流密度30 min平均值与同步水汽压亏缺(VPD)平均值的相关关系

Table 2 Correlation coefficients between 30 min average nighttime sap flow of sampled trees and vapor pressure deficit (VPD)

树种 Species	样木编号 No. of sample trees	Pearson相关系数 Pearson correlation	显著度(双尾) Sig. (2-tailed)	n
雪松 Cedrus deodara	C1	0.68^*	0.043	1 872
	C2	0.69^*	0.029	1 872
	C3	0.71^*	0.018	1 872
大叶榉 Zelkova schneideriana	Z1	0.65 ^*	0.046	1 872
	Z2	0.72^*	0.018	1 872
	Z3	0.70^*	0.034	1 872
丝棉木 Euonymus bungeanus	E1	0.73^*	0.029	1 872
	E2	0.61^*	0.033	1 872
	E3	0.59^*	0.042	1 872
水杉 Metasequoia glyptostroboides	M1	0.71^*	0.019	1 872
	M2	0.72^*	0.019	1 872
	M3	0.66^*	0.037	1 872

表3 树木夜间液流密度30 min平均值与同步风速均值(0-7 m·s-1)的相关关系

Table 3 Correlation coefficients between 30 min average nighttime sap flow of sampled trees and wind speed (0-7 m·s-1)

树种 Species	样木编号 No. of sample trees	Pearson相关系数 Pearson correlation	显著度(双尾) Sig. (2-tailed)	n
雪松 Cedrus deodara	C1	0.58 ^*	0.045	1 872
	C2	0.73 ^*	0.023	1 872
	C3	0.76 ^*	0.014	1 872
大叶榉 Zelkova schneideriana	Z1	0.81 ^**	0.006	1 872
	Z2	0.76 ^*	0.014	1 872
	Z3	0.73 ^*	0.022	1 872
丝棉木 Euonymus bungeanus	E1	0.72 ^*	0.031	1 872
	E2	0.41	0.099	1 872
	E3	0.69 ^*	0.023	1 872
水杉 Metasequoia glyptostroboides	M1	0.73 ^*	0.017	1 872
	M2	0.52 ^*	0.018	1 872
	M3	0.73 ^*	0.017	1 872

表4 观测季样木单日夜间液流比例统计

Table 4 Statistics of nighttime sap flow in proportion to the daily total amount

树种 Species	胸径 DBH (cm)	占日总量的比例均值 Average percentage in daily sums (%)	占日总量的最大比例 Maximum percentage in daily sums (%)	占日总量的最小比例 Minimum percentage in daily sums (%)
雪松	13.60	10.19	57.71	1.02
Cedrus deodara	17.20	5.90	39.82	0.53
	21.00	9.74	34.53	0.88
大叶榉	14.65	7.63	31.46	1.73
Zelkova schneideriana	21.47	14.40	44.79	6.88
	8.30	9.02	25.24	1.68
丝棉木	16.60	12.00	75.69	0.53
Euonymus bungeanus	13.50	11.65	27.71	0.44
	10.40	4.97	19.88	32.59
水杉	24.60	8.19	31.04	0.74
Metasequoia glyptostroboides	18.80	8.89	50.12	1.04
	14.60	6.48	32.98	0.92

图6 样木夜间液流总量与日间液流总量的相对关系。

Fig. 6 Relationships between the nocturnal and diurnal sap flow volume of all sampled trees.

图7 连续典型晴天(8月6日至9日)天气下植物夜间冠层导度(Gc)变化规律。DBH, 胸径。

Fig. 7 Canopy conductance (Gc) variation in consecutive sunny days in August (6th-9th). DBH, diameter at breast height.

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