Figure 1. The layout of the transects and quadrats. Source: Built on the basis of the author’s field survey.

Figure 1. The layout of the transects and quadrats. Source: Built on the basis of the author’s field survey.

Figure 2. Subsidence data obtained from fixed monitoring points (perpendicular to the mining direction). The legend is the date of the measurement. Source: Built on the basis of the author’s field survey and calculations.

Figure 2. Subsidence data obtained from fixed monitoring points (perpendicular to the mining direction). The legend is the date of the measurement. Source: Built on the basis of the author’s field survey and calculations.

Figure 3. Ground subsidence of the study area. The figure was obtained by subtracting the DEM of 1 September from the DEM of 30 May. Source: Built on the DEM obtained from UAV images.

Figure 3. Ground subsidence of the study area. The figure was obtained by subtracting the DEM of 1 September from the DEM of 30 May. Source: Built on the DEM obtained from UAV images.

Figure 4. The elevation value obtained by the DEM and the elevation value obtained by the field measurement (along the mining direction). Source: Built on the basis of the author’s field survey and calculations.

Figure 4. The elevation value obtained by the DEM and the elevation value obtained by the field measurement (along the mining direction). Source: Built on the basis of the author’s field survey and calculations.

Figure 5. Time series monitoring results of chlorophyll content at leaf scale. All the data in the figures were obtained at transect 1. The 31,115 working faces were mined to the position of transect 1 on 15 June. There were two quadrants in each disturbance area, and only the data from the first quadrat are shown in the figures. Source: Built on the basis of the author’s field survey and calculations.

Figure 5. Time series monitoring results of chlorophyll content at leaf scale. All the data in the figures were obtained at transect 1. The 31,115 working faces were mined to the position of transect 1 on 15 June. There were two quadrants in each disturbance area, and only the data from the first quadrat are shown in the figures. Source: Built on the basis of the author’s field survey and calculations.

Figure 6. Time series monitoring results of chlorophyll content at canopy scale. All the data in the figures were obtained at transect 1. The 31,115 working faces were mined to the position of transect 1 on 15 June. There were two quadrants in each disturbance area, and only the data from the first quadrat are shown in the figures. Source: Built on the basis of the author’s field survey and calculations.

Figure 6. Time series monitoring results of chlorophyll content at canopy scale. All the data in the figures were obtained at transect 1. The 31,115 working faces were mined to the position of transect 1 on 15 June. There were two quadrants in each disturbance area, and only the data from the first quadrat are shown in the figures. Source: Built on the basis of the author’s field survey and calculations.

Figure 7. Relationship between degradation coefficient and ground subsidence at leaf scale. Source: Built on the basis of the author’s calculations.

Figure 7. Relationship between degradation coefficient and ground subsidence at leaf scale. Source: Built on the basis of the author’s calculations.

Figure 8. Relationship between degradation coefficient and ground subsidence at canopy scale. Source: Built on the basis of the author’s calculations.

Figure 8. Relationship between degradation coefficient and ground subsidence at canopy scale. Source: Built on the basis of the author’s calculations.

Figure 9. Even if there are fissures, the roots of Ck will not easily break. Ck can continue to live (left figure). However, Sb is more likely to die (there are fissures where the red line is marked on the figure) (right figure). Source: Built on the basis of the author’s field survey.

Figure 9. Even if there are fissures, the roots of Ck will not easily break. Ck can continue to live (left figure). However, Sb is more likely to die (there are fissures where the red line is marked on the figure) (right figure). Source: Built on the basis of the author’s field survey.

Figure 10. Fissures will form when the ground sinks at inconsistent rates. Plants located directly above the fissures will die immediately, but those around the fissures will still survive. Source: Built on the basis of the author’s field survey.

Figure 10. Fissures will form when the ground sinks at inconsistent rates. Plants located directly above the fissures will die immediately, but those around the fissures will still survive. Source: Built on the basis of the author’s field survey.

Figure 11. BRRI-SPAD model for different periods. The data acquired on 11 June is represented by a black square, and the data acquired on 1 July is represented by a red circle. The data were obtained at 11:00–13:00, and the weather conditions were the same. Source: Built on the basis of the author’s field survey and calculations.

Figure 11. BRRI-SPAD model for different periods. The data acquired on 11 June is represented by a black square, and the data acquired on 1 July is represented by a red circle. The data were obtained at 11:00–13:00, and the weather conditions were the same. Source: Built on the basis of the author’s field survey and calculations.

Figure 12. The difference in degradation coefficient at canopy scale and leaf scale. Before mining, no matter at the leaf scale or canopy scale, chlorophyll content was basically the same in the natural area and subsidence area, and the degradation coefficient was about 1. After a period of mining, the chlorophyll content continued to increase in the natural area but gradually decreased in the subsidence area. Therefore, the degradation coefficient at the leaf scale is T2T1. If the quantitative model between leaf chlorophyll content and canopy chlorophyll content does not change, the degradation coefficient should be V2V1 at canopy scale. However, when the canopy structure changes, the model changes from model 1 to model 2. Therefore, the degradation coefficient at the canopy scale changes from V2V1 to V3V1. Obviously,  V3V1 < V2V1 = T2T1. Source: Author’s development.

Figure 12. The difference in degradation coefficient at canopy scale and leaf scale. Before mining, no matter at the leaf scale or canopy scale, chlorophyll content was basically the same in the natural area and subsidence area, and the degradation coefficient was about 1. After a period of mining, the chlorophyll content continued to increase in the natural area but gradually decreased in the subsidence area. Therefore, the degradation coefficient at the leaf scale is T2T1. If the quantitative model between leaf chlorophyll content and canopy chlorophyll content does not change, the degradation coefficient should be V2V1 at canopy scale. However, when the canopy structure changes, the model changes from model 1 to model 2. Therefore, the degradation coefficient at the canopy scale changes from V2V1 to V3V1. Obviously,  V3V1 < V2V1 = T2T1. Source: Author’s development.

Table 1. Working face parameters and mining parameters.

Table 1. Working face parameters and mining parameters.

ParametersValuelength of working face2600 mwidth of working face600 mcoal seam dip angle0–3°mining depth122–266 mmining height4.7–4.9 mmining rate8 m/d

Table 2. Investigation objects and investigation frequency.

Table 2. Investigation objects and investigation frequency.

Investigation ContentInvestigation FrequencyChlorophyll content at leaf scaleTransect 1: a total of 11 sets of measurements.Transect 2: a total of 11 sets of measurements. Transect 3: a total of 11 sets of measurements.Ground subsidence a total of 40 sets of measurements.UAV images a total of 11 sets of images.

Table 3. The Pearson correlation coefficient between the degradation coefficient and subsidence parameters at leaf scale.

Table 3. The Pearson correlation coefficient between the degradation coefficient and subsidence parameters at leaf scale.

Cumulative SubsidenceSubsidence RateNeutral area-Sb−0.642 **−0.298Compression area-Sb−0.597 **−0.244Extension area-Sb−0.451 *−0.148Neutral area-Ck−0.831 **−0.354Compression area-Ck−0.784 **−0.262Extension area-Ck−0.723 **−0.211

Table 4. The Pearson correlation coefficient between the degradation coefficient and subsidence parameters at the canopy scale.

Table 4. The Pearson correlation coefficient between the degradation coefficient and subsidence parameters at the canopy scale.

Cumulative SubsidenceSubsidence Rate Neutral area-Sb−0.717 **−0.312Compression area-Sb−0.651 **−0.267Extension area-Sb−0.629 **−0.178Neutral area-Ck−0.835 **−0.332Compression area-Ck−0.619 *−0.234Extension area-Ck−0.674 **−0.219