基于热比率法的青海云杉林蒸腾量估算

doi:10.17521/cjpe.2017.0082

摘要/Abstract

摘要：

流域上游森林蒸腾量的准确估算对于干旱区水资源管理至关重要。该文采用热比率法的树干液流技术对青海云杉(Picea crassifolia)单木和林分蒸腾量进行了估算和转换, 目的在于通过该研究为不同尺度森林蒸腾量估算提供一个系统的解决方案。研究结果如下: 第一, 青海云杉胸径与边材面积间存在显著指数函数关系, R² = 0.94, p < 0.000β1; 第二, 热比率法的青海云杉蒸腾量测量中, 理论值与观测值间的比例系数为1.09, 观测值偏小; 第三, 基于单木平均液流速率和林分总边材面积的林分蒸腾量计算中, 不同胸径样树液流速率的异质会导致液流速率被高估或低估近1/3; 第四, 基于单木胸径与液流量间关系的林分液流估算技术能够更合理地对青海云杉蒸腾量进行估算。根据该文研究结果, 基于探针式液流测量技术可以更为科学地对单一树种研究区不同尺度的蒸腾量进行估算。

关键词: 蒸腾量, 尺度上推, 热比率法, 青海云杉

Abstract:

Aims Accurate estimation of forest transpiration in the upper reach of the watershed is vital to the management of water resources in arid region. The objective of this study was to provide a systematic method for calculating the forest evapotranspiration at different scales.

Methods In this study we measured the whole-tree transpiration using the heat ratio method technology and estimated the stand- and catchment-transpiration employing the upscaling methods.

Important findings The main results and conclusions were as follows: First, the diameter at breast height (DBH) exhibited significant correlations with sapwood area, and the correlation was characterized by the exponential function (R²=0.94,p＜0.001).Second, in the weighted calculation of sap-flux measurements based on two-point thermocouples and sapwood area of Picea crassifolia，the correction coefficient between the true value and the observation value was 1.09. Third, when calculating sap-fluxes based on the average-sap-flux and total sapwood area of stand-transpiration, ignoring sap-flux velocity heterogeneities of trees led to transpiration rates being overestimated or underestimated by nearly one third; Fourth, the stand-transpiration estimation method based on the relationship between DBH and sap-flux can give a more reasonable prediction ofPicea crassifolia transpiration. The results indicated that the probe-based sap-flux measuring technology would perform well for the transpiration scaling-up calculation at the catchment with only one single tree species, and the calculation methodology can be applied to other watersheds.

Key words: transpiration, upscaling, heat ratio method, Picea crassifolia

杨军军, 封建民, 何志斌. 基于热比率法的青海云杉林蒸腾量估算. 植物生态学报, 2018, 42(2): 195-201. DOI: 10.17521/cjpe.2017.0082

YANG Jun-Jun, FENG Jian-Min, HE Zhi-Bin. Estimating whole-tree water use of Picea crassifolia based on heat ratio method. Chinese Journal of Plant Ecology, 2018, 42(2): 195-201. DOI: 10.17521/cjpe.2017.0082

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链接本文: https://www.plant-ecology.com/CN/10.17521/cjpe.2017.0082

https://www.plant-ecology.com/CN/Y2018/V42/I2/195

图/表 6

表1 青海云杉树干液流测量样木的生物、生理学统计参数

Table 1 Biometric and physiological parameters of sap flow measurements for Picea crassifolia

样树编号 Sample tree number	树高 Tree height	胸径 Diameter at breast height	冠幅宽度 Crown width	冠幅投影面积 Crown projection area	树皮厚度 Bark depth	心材半径 Heartwood radius	边材厚度 Sapwood width	边材面积 Sapwood area
样树编号 Sample tree number	(m)	(cm)	(m)	(m²)	(cm)	(mm)	(mm)	(mm²)
1	16.1	22.2	4.24	14.07	0.6	67	37.5	20β327.0
2	14.2	16.0	4.29	14.16	0.6	42	32.1	11β694.6
3	13.0	15.5	3.38	10.35	0.6	40	31.7	11β090.7
4	11.3	11.4	2.68	8.13	0.6	22	28.6	6β599.9
5	5.5	6.2	2.01	6.34	0.3	8	20.5	2β286.3
6	5.3	5.0	1.60	5.50	0.3	8	14.5	1β343.8
7	4.2	5.1	2.26	6.91	0.3	8	15.0	1β413.7
8	3.8	4.1	2.11	6.55	0.3	8	10.0	785.4

图1 调查林分胸径频率分布及调查样木胸径分布。

Fig. 1 Frequency percentage of diameter at breast height at investigation stand and the diameter of sample trees.

图2 青海云杉胸径(x)与边材厚度(y)变化拟合函数。

Fig. 2 Relationship between diameter at breast height (x) and sapwood width (y) for Picea crassifolia.

图3 青海云杉边材厚度与总蒸腾量间的变化关系。此处总蒸腾量为2015年7月23日到10月25日之间不同胸径青海云杉的总蒸腾量。

Fig. 3 Sap flow variation patterns of sapwood width for Qinghai spruce. Total transpiration was the transpiration of sample trees between July 23th and October 25th in 2015.

表2 观测期青海云杉逐月日均蒸腾量(平均值±标准偏差)(kg·d-1)

Table 2 The daily mean whole-tree water use in each month in the observational period (mean ± SD)(kg·d-1)

月份 Month	样树编号 Sample tree number
月份 Month	1	3	4	5	6	7	8
7月 July	68.67 ± 6.49	29.97 ± 4.19	17.89 ± 2.24	5.37 ± 0.33	7.54 ± 0.87	3.81 ± 0.43	2.78 ± 0.11
8月 August	44.55 ± 9.09	14.77 ± 4.41	9.74 ± 2.57	2.93 ± 0.89	4.36 ± 1.27	1.40 ± 0.53	1.81 ± 0.42
9月 September	34.83 ± 9.50	9.98 ± 3.29	6.88 ± 3.01	1.72 ± 0.72	2.56 ± 1.29	0.53 ± 0.09	0.97 ± 0.28
10月 October	25.81 ± 6.68	6.99 ± 1.43	3.16 ± 1.20	0.95 ± 0.31	1.64 ± 0.68	0.41 ± 0.03	0.79 ± 0.18

图4 观测期(7月23日到10月25日)林分蒸腾量与单木蒸腾量间对比关系。

Fig. 4 Stand sap-flow pattern and tree sap-flow patterns on seven measured trees during the observational period (between July 23th and October 25th in 2015).

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