黄土高原生态工程实施下基于日光诱导叶绿素荧光的植被恢复生产力效益评价

doi:10.17521/cjpe.2022.0226

摘要/Abstract

摘要：

基于日光诱导叶绿素荧光(SIF)揭示黄土高原大面积实施生态工程后植被恢复区域的植被生产力效益。通过分析遥感观测的地表绿度特征变化和土地利用动态, 该研究首先识别了近20年来黄土高原植被恢复区域和原有植被的空间分布范围, 在此基础上, 使用SIF和气象数据, 根据改进机理光响应模型(rMLR)计算了植被总初级生产力(GPP), 对比分析了植被恢复区域绿度特征变化下GPP的差异。结果显示: 空间上, 由于生态工程的广泛实施, 黄土高原整体绿化情况得到了明显改善。在2001-2020年间, 黄土高原上林地恢复面积约3.5万km², 占区域总面积的7.42%; 草地恢复面积11万km², 约占区域总面积的25.25%。整体上, 林地恢复区域的光合能力和生产力水平均低于原有林地, 而草地恢复区域较原有草地高; 恢复林地的GPP相当于原有林地GPP的83.86%, 恢复草地的GPP相当于原有草地的121.10%。在相同的叶面积指数(LAI)等级下, 植被恢复区域与原有植被的生产力呈现不同的差异性, 当LAI较大时植被恢复区域与原有植被的GPP差距较大。由裸地转变而来的植被恢复区域生产力效益最差, 而林地生长区域和退耕还草的植被恢复区域分别是林地恢复和草地恢复中的最优模式。植被恢复区域的LAI增长速率和恢复年限也影响了生产力, LAI增长速率越大的区域生产力效益越高, 林地恢复年限越久越利于生产力的提升, 草地恢复年限较短的区域有较高的生产力。总体上, 由于生态工程的实施, 虽然黄土高原上的植被覆盖面积和生物量得到了显著提高, 但植被生产力(尤其是林地)并没有获得同等程度的恢复, 影响了生态工程的生态效益。

关键词: 生态工程, 植被恢复, 日光诱导叶绿素荧光(SIF), 总初级生产力(GPP), 黄土高原

Abstract:

Aims Based on the solar-induced chlorophyll fluorescence (SIF), this study was conducted to reveal the benefit of vegetation productivity in the revegetation region with a significant increase in land surface greenness under the large-scale implementation of ecological programs in the Loess Plateau.

Methods By interpreting satellite-observed terrestrial greenness changes and land use/cover dynamics, we first identified the spatial distribution of revegetation and existing vegetation in the Loess Plateau in the last 20 years. Then, using SIF and meteorological data, the gross primary productivity (GPP) of the revegetation and existing vegetation was calculated according to the revised mechanistic light response (rMLR) model. Finally, we adopted the comparative analysis approach to compare the differences in GPP of the revegetation based on the SIF observations.

Important findings Our results indicated that the ecological programs have made a widespread increase in land surface greenness in the Loess Plateau. In the period 2001 to 2020, the area of revegetated forest was 35 000 km², accounting for 7.42% of the total area, whereas revegetated grassland area was 110 000 km², accounting for 25.25% of the total area. Overall, the photosynthetic capacity and vegetation productivity of the revegetated forests were lower than that of existing forests in the Loess Plateau, while revegetated grassland was higher. GPP of the revegetated forest was equivalent to 83.86% of the existing forest, and GPP of the revegetated grassland was equivalent to 121.10% of that of the existing grassland. At the same leaf area index (LAI) level, GPP of revegetation and existing vegetation showed differences that GPP gap increased as LAI became higher. Revegetation transformed from bare land showed the lowest vegetation productivity, whereas forest growth and grassland restoration from cropland were the optimal land use/cover transition pattern for the revegetated forest and revegetated grassland, respectively. LAI increasing rate and restoration time also affected the productivity of revegetation, revegetated areas with higher LAI increasing rate showed more extensive productivity benefits. Vegetation productivity of revegetated forest increased with standage, while revegetated grassland with shorter restoration periods showed higher productivity. Overall, although ecological programs have widely increased vegetation cover and biomass in the Loess Plateau, however, there exists a certain gap in GPP between the revegetation and existing vegetation areas (especially in forests), thereby affecting the ecological benefits of the ecological programs.

Key words: ecological programs, revegetation, solar-induced chlorophyll fluorescence (SIF), gross primary productivity (GPP), the Loess Plateau

薛金儒, 吕肖良. 黄土高原生态工程实施下基于日光诱导叶绿素荧光的植被恢复生产力效益评价. 植物生态学报, 2022, 46(10): 1289-1304. DOI: 10.17521/cjpe.2022.0226

XUE Jin-Ru, LÜ Xiao-Liang. Assessment of vegetation productivity under the implementation of ecological programs in the Loess Plateau based on solar-induced chlorophyll fluorescence. Chinese Journal of Plant Ecology, 2022, 46(10): 1289-1304. DOI: 10.17521/cjpe.2022.0226

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链接本文: https://www.plant-ecology.com/CN/10.17521/cjpe.2022.0226

https://www.plant-ecology.com/CN/Y2022/V46/I10/1289

图/表 10

图1 黄土高原地理位置。

Fig. 1 Location of the Loess Plateau.

表1 4个AmeriFlux通量站点的详细信息

Table 1 Details of the four AmeriFlux eddy flux sites

名称 Name	经度 Longitude	纬度 Latitude	海拔 Altitude (m)	生态系统类型 Ecosystem type
CA-Cbo	79.93° W	44.32° N	120	落叶阔叶林 Deciduous broadleaf forests
US-MMS	86.41° W	39.32° N	275	落叶阔叶林 Deciduous broadleaf forests
US-MOz	92.20° W	38.74° N	219	落叶阔叶林 Deciduous broadleaf forests
US-Ha1	72.17° W	42.54° N	340	混交林 Mixed forests

图2 黄土高原植被恢复区域和原有植被区域空间分布。A, 林地恢复区域。B, 草地恢复区域。C, 原有林地区域。D, 原有草地区域。

Fig. 2 Spatial distribution of revegetation and existing vegetation of the Loess Plateau. A, Revegetated forest area. B, Revegetated grassland area. C, Existing forest area. D, Existing grassland area.

图3 2020年黄土高原植被恢复区域和原有植被年平均总初级生产力(GPP)空间分布。A, 恢复林地GPP。B, 恢复草地GPP。C, 原有林地GPP。D, 原有草地GPP。

Fig. 3 Spatial distribution of annual average gross primary production (GPP) in the revegetation and existing vegetation areas of the Loess Plateau in 2020. A, GPP of revegetated forest. B, GPP of revegetated grassland. C, GPP of existing forest. D, GPP of existing grassland.

图4 基于TROPOspheric Monitoring Instrument (TROPOMI)日光诱导叶绿素荧光(SIF)计算的总初级生产力(GPP)与实测GPP的比较结果。A, CA-Cbo。B, US-MMS。C, US-MOz。D, US-Ha1。R2, 决定系数; RMSE, 均方根误差; rRMSE, 相对均方根误差。

Fig. 4 Comparison of gross primary production (GPP) calculated based on TROPOspheric Monitoring Instrument (TROPOMI) solar-induced chlorophyll fluorescence (SIF) and observed GPP. A, CA-Cbo. B, US-MMS. C, US-MOz. D, US-Ha1. R2, determinate coefficient; RMSE, root mean square error; rRMSE, relative root mean square error.

图5 黄土高原2020年植被恢复区域与原有植被区域平均冠层顶部日光诱导叶绿素荧光(SIFTOC)、总初级生产力(GPP)对比。A, 林地恢复区域与原有林地区域平均SIFTOC对比。B, 草地恢复区域与原有草地区域平均SIFTOC对比。C, 林地恢复区域与原有林地区域平均GPP对比。D, 草地恢复区域与原有草地区域平均GPP对比。

Fig. 5 Comparison of mean top-of-canopy solar-induced chlorophyll fluorescence (SIFTOC) and gross primary production (GPP) between revegetation and existing vegetation area in the Loess Plateau in 2020. A, Mean SIFTOC comparison between revegetated forest and existing forest. B, Mean SIFTOC comparison between revegetated grassland and existing grassland. C, mean GPP comparison between revegetated forest and existing forest. D, Mean GPP comparison between revegetated grassland and existing grassland.

图6 黄土高原2020年不同叶面积指数(LAI)等级下植被恢复区域和原有植被区域的总初级生产力差异(GPPD)。A, 不同LAI等级下的林地恢复GPPD。B, 不同LAI等级下的草地恢复GPPD。

Fig. 6 Gross primary production difference (GPPD) between revegetation and existing vegetation area under different leaf area index (LAI) level in the Loess Plateau in 2020. A, GPPD of revegetated forest under different LAI levels. B, GPPD of revegetated grassland under different LAI levels.

图7 黄土高原2020年不同条件下植被恢复区域和原有植被区域的总初级生产力差异(GPPD)。A, 不同土地利用类型转变方式下的林地恢复GPPD。B, 不同土地利用类型转变方式下的草地恢复GPPD。C, 不同Sen斜率等级下的林地恢复GPPD。D, 不同Sen斜率等级下的草地恢复GPPD。

Fig. 7 Gross primary production difference (GPPD) between revegetation and existing vegetation area under different conditions in the Loess Plateau in 2020. A, GPPD of revegetated forest under different land use/cover change types. B, GPPD of revegetated grassland under different land use/cover change types. C, GPPD of revegetated forest under different Sen slope levels. D, GPPD of revegetated grassland under different Sen slope levels.

图8 黄土高原2020年不同植被恢复时间的植被恢复区域和原有植被区域的总初级生产力差异(GPPD)。A, 不同恢复时间下的林地GPPD。B, 不同恢复时间下的草地GPPD。

Fig. 8 Gross primary production difference (GPPD) between revegetation and existing vegetation area under different restoration time in the Loess Plateau in 2020. A, GPPD of revegetated forest under different restoration time. B, GPPD of revegetated grassland under different restoration time.

图9 黄土高原2020年不同气候条件下植被恢复区域和原有植被区域的总初级生产力差异(GPPD)。A, 不同温度等级下的林地恢复GPPD。B, 不同温度等级下的草地恢复GPPD。C, 不同土壤湿度等级下的林地恢复GPPD。D, 不同土壤湿度等级下的草地恢复GPPD。

Fig. 9 Gross primary production difference (GPPD) between revegetation and existing vegetation area under different climate conditions in the Loess Plateau in 2020. A, GPPD of revegetated forest under different temperature levels. B, GPPD of revegetated grassland under different temperature levels. C, GPPD of revegetated forest under different soil moisture levels. D, GPPD of revegetated grassland under different soil moisture levels.

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