# Characterizing Growing Season Length of Subtropical Coniferous Forests with a Phenological Model
## Appendix E  
On average, LORS was \(\sim\)2.5 months in length, and slightly higher in the mesic site (81 d) versus the intermediate and xeric site (78 d). The average LOF (40-51 d) was greater than the average LOR (30-38 d), which may indicate that even if precipitation recovered after a short-term drought, the response of GPP recovery to precipitation was delayed. In the mesic site, the water stress in 2010 occurred in July, and the precipitation was 27.43 mm in that month, but the precipitation returned to normal in August (160.52 mm), which put its POR at early September (252 d). A severe drought occurred in June 2011 with 50.8 mm of precipitation, and precipitation recovered in July (126.23 mm), but the precipitation began to fall again in August (52.32 mm), which brought SOD closer to late spring (135 d), ROD closer to the end of June and POR near mid-August. There was no drought in the summer of 2012 (total precipitation in June-August was 439 mm), and thus the reason for the decline in GPP may be a delayed effect of excessive March rainfall (Appendix B, Figure A2) [64]. Due to the effect of a spring flood event (April, 280.41 mm) and water stress from July to August, there was a lack of recovery in GPP after the end of spring until EOS. A short-term drought occurred in August (30.38 mm) in 2015, but although there was abundant precipitation in June-July, there was still significant GPP decline and the ecosystem entered autumn earlier than normal (210 d). One potential reason could be the dynamics of VPD [63]. For the intermediate site, in 2010, water stress occurred in June-August (total precipitation of 205.48 mm and very low July precipitation of 34.29 mm). Although August precipitation had a weak recovery (85.34 mm), which was reflected in the GPP growth rate (weak recovery trend; Figure A2), it did not offset the carbon loss in July. This led to SOD occurring in the late spring after photosynthesis of the ecosystem reached its peak in the late spring, and GPP continued to decline into autumn until EOS without a recovery. One reason may be that after this severe drought event in July, more August precipitation was needed to recover and stabilize GPP (\(\sim\)85.34 mm), but the threshold of \"effective precipitation\" after the drought was still uncertain. In 2011, drought occurred in June (51.82 mm) and precipitation recovered in July (115.56 mm) but declined again in August (68.08 mm). This caused ROD to occur at the beginning of July and POR at the middle of August, and the ecosystem entered autumn earlier (222 d) than normal (\(\sim\)240 d). In 2014, Due to the spring flood and water stress in July-August (65.87 and 28.95 mm), GPP continued to decline until EOS without obvious GPP recovery. Water stress occurred inAugust (49.27 mm) in 2015, which brought the POR to 211 d; that is, the ecosystem entered autumn early in August until EOS. However, after the spring (140 d), there has been a significant decline in GPP, which is inconsistent with sufficient precipitation from June to July (152.92 and 99.32 mm). One potential reason for that phenomenon may also be the VPD dynamics [63]. In the xeric site in 2010, water stress occurred in June-July (73.41 and 40.89 mm), and precipitation began to recover in August (117.34 mm). Although the recovery of precipitation caused the GPP growth rate to recover, which offset the decline in GPP from June to July, it did not cause a significant GPP recovery. The reasons for this phenomenon are not clear. A severe drought occurred in June and August 2011 (38.86 and 30.22 mm), but July precipitation was normal (160.03 mm). This led to SOD in spring, ROD in late June and early July (188 d), with a POR of 216 d (early start of autumn). Flooding occurred in spring 2014, and the phenology response of the xeric site was consistent with the intermediate and mesic sites. There was no severe drought in the summer of 2015, but GPP decline still occurred, which may have been affected by VPD [63].