3类典型温带山地森林的叶面积指数的季节动态: 多种监测方法比较

doi:10.3724/SP.J.1258.2012.00231

摘要/Abstract

摘要：

叶面积指数(leaf area index, LAI)是定量描述冠层结构的最有效指标之一。鉴于森林冠层三维结构的高度复杂性和异质性, 迄今仍没有形成统一标准的LAI测量方法。该文利用LAI-2000冠层分析仪、CI-110冠层分析仪和半球摄影法(digital hemispherical photograph, DHP), 对北京东灵山地区以蒙古栎(Quercus mongolica)为主的落叶阔叶林、华北落叶松(Larix gmelinii var. principis-rupprechtii)林和油松(Pinus tabuliformis)林的有效叶面积指数(effective leaf area index, LAI_e)进行了动态监测, 探寻其季节变化规律。为准确地估算温带山地主要森林类型的LAI, 对光学仪器测量值进行了去除木质成分、聚集效应等校正, 与基于凋落物收集法的相应实测值进行了比较分析。结果表明: 3种典型森林在生长季期间叶片生长均呈现单峰型; 3种光学仪器测量方法的同期LAI_e数值大小顺序为: LAI-2000冠层分析仪>DHP>CI-110冠层分析仪。光学仪器的直接测量值LAI_e包含了木质成分的贡献, 钝化了季节动态的变化幅度, 这对有明显季节交替的落叶林尤为突出。经校正, LAI-2000冠层分析仪和DHP的测量值与实测值都表现出显著的相关性, 其中LAI-2000冠层分析仪最适于采用基于空隙大小的校正方法, 而基于空隙度和空隙大小的综合算法则是校正DHP的最佳选择。结合经济成本和野外实际操作等因素考虑, DHP具有更大的推广优势, 特别适用于温带山地落叶林。

关键词: 聚集效应, 有效叶面积指数, 光学测量方法

Abstract:

Aims Leaf area index (LAI) is one of the most frequently used parameters for analysis of canopy structure and forest productivity. It can be determined by direct or indirect methods. Sources of errors in indirect LAI measurements with optical instruments include non-photosynthetic components, element clumping, and a topography effect. Our objective was to find an appropriate method for evaluating LAI and its seasonal dynamics in typical temperate montane forest.
Methods We examined the applicability of three indirect methods (LAI-2000 plant canopy analyzer, CI-110 plant canopy analyzer and digital hemispherical photograph (DHP)) and one direct method (litterfall) to determine the seasonal dynamics of LAI in three typical temperate forests in Dongling Mountain of Beijing. The forests included a secondary deciduous broad-leaved forest dominated by Quercus mongolica and two plantations (Larix gmelinii var. principis-rupprechtii and Pinus tabuliformis). These represent deciduous broad-leaved forest, deciduous needle-leaved forest and evergreen needle-leaved forest, respectively. The optically-based effective leaf area index (LAI_e) values were corrected to eliminate wood elements and clumping effects and then compared with the direct measurement of LAI based on litter collection.
Important findings For all the three forests, the LAI seasonal dynamic shows a uni-modal pattern with a peak in July. Optically-based LAI_e underestimated the amplitude of the seasonal dynamics. Wood element elimination can strengthen the seasonal sensitivity of LAI, especially in the seasonally distinct deciduous forest. The order of LAI_e measured by the three optically-based methods in three stands is LAI-2000 plant canopy analyzer > DHP > CI-110 plant canopy analyzer. There was good correspondence with the direct measurement LAI for the corrected LAI of LAI-2000 plant canopy analyzer and DHP. The correction method based on gap-size distribution was appropriate for the LAI-2000 plant canopy analyzer and the method based on both gap fraction and gap-size distribution for DHP. Considering economics and practical convenience, we recommend DHP for LAI evaluation in these temperate montane forests.

Key words: clumping effects, effective leaf area index, optically-based methods

苏宏新, 白帆, 李广起. 3类典型温带山地森林的叶面积指数的季节动态: 多种监测方法比较. 植物生态学报, 2012, 36(3): 231-242. DOI: 10.3724/SP.J.1258.2012.00231

SU Hong-Xin, BAI Fan, LI Guang-Qi. Seasonal dynamics in leaf area index in three typical temperate montane forests of China: a comparison of multi-observation methods. Chinese Journal of Plant Ecology, 2012, 36(3): 231-242. DOI: 10.3724/SP.J.1258.2012.00231

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链接本文: https://www.plant-ecology.com/CN/10.3724/SP.J.1258.2012.00231

https://www.plant-ecology.com/CN/Y2012/V36/I3/231

图/表 9

图1 1993-2010年研究样地附近气象站(39°58′ N, 115°26′ E, 海拔1 150 m)的月平均气温和降水量(平均值±标准偏差)。

Fig. 1 Mean monthly air temperatures and monthly precipitation (mean ± SD) during 1993 to 2010 from the meteorological station (39°58′ N, 115°26′ E, 1 150 m a.s.l.) adjacent to study site.

表1 3块永久性监测样地的基本情况

Table 1 Basic information of three permanent sample plots

森林类型 Forest type	海拔 Altitude (m)	坡向 Slope aspect	坡度 Slope	乔木密度¹⁾ Tree density¹⁾ (ind.·hm^-2)	胸断面积 Area at breast height (m²)	树高(平均值± 标准偏差) Tree hight (mean ± SD) (m)	主要乔木树种 Main tree species
落叶阔叶林 DBH	1 200	28°	35° NW	2 333	23.41	7.9 ± 1.4	蒙古栎 Quercus mongolica 黑桦 Betula dahurica 五角枫 Acer pictum subsp. mono
落叶针叶林 DNF	1 200	26°	40° NW	3 294	24.51	10.4 ± 1.1	华北落叶松 Larix gmelinii var. principis-rupprechtii
常绿针叶林 ENF	1 150	30°	60° NE	1 333	25.16	10.9 ± 0.3	油松 Pinus tabuliformis

表2 主要乔木树种的比叶面积(cm2 ·g-1)

Table 2 Specific leaf area (SLA, cm2 ·g-1) for main tree species

树种 Tree species	比叶面积 Specific leaf area (SLA)
树种 Tree species	平均值±标准偏差 Mean ± SD	最小值 Minimum	最大值 Maximum
蒙古栎 Quercus mongolica	125.65 ± 21.86	94.98	143.89
黑桦 Betula dahurica	164.12 ± 17.73	149.60	194.55
五角枫 Acer pictum subsp. mono	204.98 ± 22.67	175.48	239.25
白桦 Betula platyphylla	163.23 ± 11.83	151.33	177.25
糠椴 Tilia mandshurica	197.20 ± 24.16	175.15	234.68
黄花柳 Salix caprea	177.27 ± 8.66	166.79	189.41
北京花楸 Sorbus discolor	209.77 ± 45.76	138.85	249.46
青杨 Populus cathayana	200.40 ± 20.07	165.61	215.14
胡桃楸 Juglans mandshurica	158.25 ± 21.51	131.84	182.76
花曲柳 Fraxinus chinensis subsp. rhynchophylla	203.52 ± 29.37	174.36	244.55
蒿柳 Salix schwerinii	135.01 ± 14.11	120.44	156.46
大果榆 Ulmus macrocarpa	197.48 ± 38.30	134.71	237.68
裂叶榆 Ulmus laciniata	221.15 ± 22.56	187.21	248.75
其他阔叶树 Other broad-leaved species	181.39 ± 36.68	94.98	249.46

图2 基于半球摄影法的冠层基本组分聚集指数的季节动态。A, 落叶阔叶林。B, 落叶针叶林。C, 常绿针叶林。CC, 基于空隙大小的聚集指数; CLX, 基于冠层孔隙度和空隙大小两种算法综合的聚集指数; LX, 基于冠层孔隙度的聚集指数。

Fig. 2 Seasonal dynamics of canopy element clumping index based on digital hemispherical photograph. A, deciduous broad-leaved forest. B, deciduous needle-leaved forest. C, evergreen needle-leaved forest. CC, canopy element clumping index based on gap size; CLX, canopy element clumping index based on both gap fraction and gap size distribution; LX, canopy element clumping index based on gap fraction.

图3 3种仪器测量的有效叶面积指数的季节动态(平均值±标准偏差)。A, 落叶阔叶林。B, 落叶针叶林。C, 常绿针叶林。CI-110, CI-110冠层分析仪。DHP, 半球摄影法。LAI-2000, LAI-2000冠层分析仪。

Fig. 3 Seasonal dynamics of effective leaf area index (LAIe) measured by three kinds of instruments (mean ± SD). A, deciduous broad-leaved forest. B, deciduous needle-leaved forest. C, evergreen needle-leaved forest. CI-110, CI-110 plant canopy analyzer. DHP, digital hemispherical photograph. LAI- 2000, LAI-2000 plant canopy analyzer.

图4 叶面积指数的季节动态(平均值±标准偏差)。A, 落叶阔叶林。 B, 落叶针叶林。 C, 常绿针叶林。1, CI-110冠层分析仪。 2, 半球摄影法。3, LAI-2000冠层分析仪。CC, 基于空隙大小的聚集指数校正的叶面积指数; CLX, 基于冠层孔隙度和空隙大小两种算法综合的聚集指数校正的叶面积指数; Col, 基于凋落物收集的叶面积指数实测值; LX, 基于冠层孔隙度的聚集指数校正的叶面积指数。

Fig. 4 Seasonal dynamics of leaf area index (LAI) (mean ± SD). A, deciduous broad-leaved forest. B, deciduous needle-leaved forest. C, evergreen needle-leaved forest. 1, CI-110 plant canopy analyzer. 2, digital hemispherical photograph. 3, LAI-2000 plant canopy analyzer. CC, LAI by correction method based on the gap size clumping index; CLX, LAI by correction method both based on the gap fraction and gap size distribution clumping index; Col, LAI by direct measurement based on litter collection; LX, LAI by correction method based on the gap fraction clumping index.

表3 有效叶面积指数(LAIe)和叶面积指数(LAI)的方差分析

Table 3 Variance analysis of effective leaf area index (LAIe) and leaf area index (LAI)

林型 Forest type	月份 Month	LAI_Col	CI-110冠层分析仪 CI-110 plant canopy analyzer				半球摄影法 Digital hemispherical photograph				LAI-2000冠层分析仪 LAI-2000 plant canopy analyzer
林型 Forest type	月份 Month	LAI_Col	LAI_e	LAI_CC	LAI_LX	LAI_CLX	LAI_e	LAI_CC	LAI_LX	LAI_CLX	LAI_e	LAI_CC	LAI_LX	LAI_CLX
落叶阔叶林 Deciduous broad- leaved forest	MJ	-	***	***	*	***	*	***	*	***	*	***	*	***
落叶阔叶林 Deciduous broad- leaved forest	JO	***	N	N	*	*	N	N	*	*	N	***	*	*
落叶针叶林 Deciduous needle- leaved forest	MJ	-	*	*	***	*	***	*	***	*	***	*	***	*
落叶针叶林 Deciduous needle- leaved forest	JO	***	*	*	***	*	***	*	***	*	*	*	***	*
常绿针叶林 Evergreen needle- leaved forest	MJ	-	*	*	*	*	N	*	*	N	*	*	*	N
常绿针叶林 Evergreen needle- leaved forest	JO	***	N	N	***	*	*	N	*	*	*	N	*	*

图5 有效叶面积指数与基于凋落物收集的重建叶面积指数实测值的比较(平均值±标准偏差)。A, 落叶阔叶林(DBF)。B, 落叶针叶林(DNF)。C, 常绿针叶林(ENF)。CI-110, CI-110冠层分析仪; DHP, 半球摄影法; LAI-2000, LAI-2000冠层分析仪。

Fig. 5 Comparison of effective leaf area index (LAIe) and reconstructed LAI by direct measurement based on litter collection (LAICol) (mean ± SD). A, Deciduous broad-leaved forest. B, Deciduous needle-leaved forest. C, Evergreen needle-leaved forest. CI-110, CI-110 plant canopy analyzer; DHP, digital hemispherical photograph; LAI-2000, LAI-2000 plant canopy analyzer.

图6 比较光学仪器观测的叶面积指数与基于凋落物收集重建的叶面积指数(平均值±标准偏差)。A, 落叶阔叶林。B, 落叶针叶林。C, 常绿针叶林。1, CI-110冠层分析仪。2, 半球摄影法。3, LAI-2000冠层分析仪。CC, 基于空隙大小的聚集指数校正的叶面积指数; CLX, 基于冠层孔隙度和空隙大小两种算法综合的聚集指数校正的叶面积指数; LX, 基于冠层孔隙度的聚集指数校正的叶面积指数。

Fig. 6 Comparison of leaf area indexes (LAI) between by optical instruments and reconstruction based on litter collection (LAICol) (mean ± SD). A, Deciduous broad-leaved forest. B, Deciduous needle-leaved forest. C, Evergreen needle-leaved forest. 1, CI-110 plant canopy analyzer. 2, Digital hemispherical photograph (DHP). 3, LAI-2000 plant canopy analyzer. CC, LAI by correction method based on the gap size clumping index; CLX, LAI by correction method both based on the gap fraction and gap size distribution; LX, LAI by correction method based on the gap fraction clumping effect index.

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