基于树干液流测定值进行尺度扩展的马占相思林段蒸腾和冠层气孔导度

doi:10.17521/cjpe.2006.0086

摘要/Abstract

摘要：

应用Granier热消散探针,长期监测华南丘陵地马占相思(Acacia mangium)林14棵样树的树干液流(Sap flow),由此计算整树和林段的蒸腾速率,结合同步记录的环境因子,求算冠层平均气孔导度(G_c)。Granier探针的灵敏度较高,能精确测定即使是微弱的液流活动。观测结果显示,树木个体之间的液流密度(J_s)和整树蒸腾(E_t)受树形特征影响较大。马占相思林径级大的树木个体数较少,但占据林段边材总面积和林段蒸腾的比例较大。J_s和E_t的日变化主要受光合有效辐射(Q_o)和空气水蒸气压亏缺(D)的控制,土壤含水量(θ)对较大胸径树木E_t的影响大于胸径较小的树木,个体之间J_s和E_t的差异随θ的下降而缩小。一年中,林段蒸腾(E)在光照和水热条件较好的7月最高,9~12月,由于土壤水分供应的减少致使E值降低,E对D的敏感性下降。G_c与主要环境因子的关系与E相似,如果θ长期偏低,G_c会明显下降,是造成E降低的主要原因。成熟马占相思林在光照充足、水热条件较好的情况下的蒸腾活动旺盛,但对土壤水分胁迫的忍受力较低。

关键词: 马占相思, 树干液流, 冠层平均气孔导度, 空气水蒸气压亏缺, Granier探针

Abstract:

Background and Aims Canopy stomatal conductance is considered as a sensitive parameter of forest ecosystem in responding to environmental changes and can be used to monitor the impacts of water stress, air pollution, trace gas and other environmental factors on forest function. Sap flow of an Acacia mangium forest was measured to scale up stand transpiration and canopy stomatal conductance. It aimed at understanding water use of A. mangium forest in different environmental water conditions and its responses to soil moisture change at an ecosystem level.
Methods The Granier's thermal dissipation probes were applied to monitor sap flow of 14 sample trees in an Acacia mangium forest in hilly land of South China. The sap flow data were used to calculated whole-tree and stand transpiration, and to estimate mean canopy stomatal conductance (G_c) by combing with synchronous measurement of environmental factors.
Key Results Sap flux density (J_s) and whole-tree transpiration (E_t) were obviously affected by tree morphological features. Even though there were less individual trees with large diameter at breast height (DBH) in the sample plot, they comprised relatively larger proportions of total sapwood area and transpiration of the forest. Daily variations of J_s and E_t were mainly controlled by photosynthetically active radiation (Q_o) and vapor pressure deficit (D). Soil moisture (θ) had greater effects on J_s and E_t of trees with larger DBH than on those trees with smaller DBH. The differences of J_s and E_t across individuals reduced with decreasing θ. The highest stand transpiration (E) occurred in July when the radiation and hydrothermal condition were favorable, whereas the reduced water supply in soil during the time period of September-November resulted in lower E value and its sensitivity to D. G_c responded to major environmental factors in a similar way with E. Long-term lower θ would significantly decreased G_c, which would cause reduction in E.
Conclusions Mature A. mangium forest can maintain a vigorous transpiration under sufficient radiation and hydrothermal conditions, but could not stand well under long-term stress of soil moisture. Granier's probes have the potential to accurately estimate stand transpiration, canopy conductance and their responses to environmental factor, extending the temporal and spatial scales in studying the ecological process of forest ecosystem.

Key words: Acacia mangium, Sap flow, Mean canopy stomatal conductance, Atmospheric vapor pressure deficit, Granier's probe

赵平, 饶兴权, 马玲, 蔡锡安, 曾小平. 基于树干液流测定值进行尺度扩展的马占相思林段蒸腾和冠层气孔导度. 植物生态学报, 2006, 30(4): 655-665. DOI: 10.17521/cjpe.2006.0086

ZHAO Ping, RAO Xing-Quan, MA Ling, CAI Xi-An, ZENG Xiao-Ping. SAP FLOW-SCALED STAND TRANSPIRATION AND CANOPY STOMATAL CONDUCTANCE IN AN ACACIA MANGIUM FOREST. Chinese Journal of Plant Ecology, 2006, 30(4): 655-665. DOI: 10.17521/cjpe.2006.0086

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链接本文: https://www.plant-ecology.com/CN/10.17521/cjpe.2006.0086

https://www.plant-ecology.com/CN/Y2006/V30/I4/655

图/表 11

图1 马占相思林样地树木的分布状况 ● 树干液流测定的样树○ 非树干液流测定的树木

Fig.1 Tree distribution within the sample plot of Acacia mangium forest ● Sap flow measurement ○Non-sap flow measurement

图2 马占相思胸径与边材面积的相关关系

Fig.2 Correlation between diameter at breast height (DBH) and sapwood area (As)

表1 马占相思样树的树形特征

Table 1 Tree characteristics of Acacia mangium

序号 No.	树高 Height (m)	枝下高 Stem length (m)	冠幅 Canopy size (m×m)		胸径 DBH (m)	边材厚度 Sapwood depth (m)	边材面积 Sapwood area (m²)
1	19.3	3.1	6.7	3.3	0.292 9	0.025 4	0.020 1
2	17.9	2.7	4.6	3.0	0.238 8	0.021 7	0.013 7
3	22.8	9.0	6.1	8.4	0.328 9	0.027 9	0.024 8
4	19.5	2.8	7.5	8.1	0.375 1	0.031 1	0.031 6
5	15.6	1.6	3.8	2.7	0.181 5	0.017 8	0.008 3
6	14.5	6.0	2.6	4.1	0.171 9	0.017 1	0.007 5
7	12.0	7.3	3.3	4.1	0.168 9	0.016 9	0.007 2
8	19.5	6.5	3.3	3.3	0.238 8	0.021 7	0.013 7
9	18.2	9.2	3.7	2.4	0.213 3	0.020 0	0.011 1
10	18.7	10.9	3.0	4.1	0.254 7	0.022 8	0.015 5
11	19.5	12.0	3.9	1.5	0.203 8	0.019 3	0.010 2
12	20.0	9.3	4.6	4.3	0.207 0	0.019 5	0.010 5
13	12.0	3.7	3.6	4.7	0.133 7	0.014 5	0.004 7
14	19.5	4.7	2.6	2.7	0.181 5	0.017 8	0.008 3

图3 马占相思林样地树木径级的分布频度及对应的边材总面积

Fig.3 Frequency distribution of diameter at breast height (DBH) and sum of sapwood area of all trees at different DBH ranks 1: DBH<0.15 m 2: 0.15 m≤DBH<0.20 m 3: 0.20 m≤DBH<0.25 m 4: 0.25 m≤DBH<0.30 m 5: 0.30 m≤DBH

图4 马占相思光合有效辐射、气温、空气水蒸气压亏缺、液流密度和整树蒸腾的日变化

Fig.4 Daily variation of photosynthetically active radiation (Qo), air temperature (T), vapor pressure deficit (D),sap flux density (JS) and whole-tree transpiration (Et)

图5 马占相思林样地不同径级树木总蒸腾于不同季节的日变化图内柱形小插图示每个径级树木单日蒸腾量占林段总蒸腾的百分比 Eci: 径级I树木的总蒸腾

Fig.5 Daily variation of total transpiration of different diameter at breast height (DBH) rank in different seasons Inserted graphics show the percentage of transpiration of different DBH in the total stand transpiration Eci: Total transpiration trees at DBH rank of I

图6 马占相思林段蒸腾、光合有效辐射、气温、空气水蒸气压亏缺以及土壤含水量的年进程(2004) 间断空白处为雷电或停电造成数据采集仪停止工作,或者仪器故障没有数据记录

Fig.6 Change of stand transpiration (E), photosynthetically active radiation (Qo), air temperature (T), vapor pressure deficit (D) and soil moisture (θ) in year of 2004 Missing data were due to equipment failure as a result of power off or lightning

图7 不同土壤水分条件下马占相思林段蒸腾对空气水蒸气压亏缺的响应 θ:土壤含水量

Fig.7 Stand transpiration (Ec) in response to vapor pressure deficit (D) in different soil moisture levels θ:Soil moisture

图8 马占相思林冠层平均气孔导度的日变化

Fig.8 Daily variation of mean canopy stomatal conductance (Gc)

图9 马占相思林冠层平均气孔导度的年进程

Fig.9 Yearly course of mean canopy stomatal conductance (Gc)

图10 马占相思林冠层平均气孔导度与土壤含水量的相关分析

Fig.10 Mean canopy stomatal conductance (Gc) in correlation with soil moisture (θ)

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