Monitoring of vegetation restoration and ecological dynamics of post-fire habitats at Yushan National Park Dujyuan Campground
中文摘要
一.計畫緣起及目的
110年5月16日上午接獲通報因山友
登山用火不慎導致玉山國家公園八通關古道杜鵑營地附近造成森林火燒，歷經12天，至110年5月27日熄滅，經行政院農業部林業及自然保育署嘉義分署(前身為農業委員會林務局嘉義林區管理處)判釋被害面積約22.1公頃以上，延燒面積約79.7公頃。110－111年間，已評估火燒的嚴重程度，並建立長期樣區監測火燒跡地復育情況。本年度持續監測火燒跡地與周遭環境的森林復育情形，並提出該區域火燒森林的中長期監測模式。
二、研究方法及過程
本研究先以杜鵑營地火燒前的氣候情況、水分條件以及地形因子，探究區域內火燒的風險因素，再將杜鵑營地受火燒影響區域劃分為核心區、推移帶、未受干擾區，使用衛星影像之標準化植生指標(NDVI)、葉面積指數指標(LAI)以及淨初生產力指標(GPP)，檢視火燒前後植群整體變動趨勢。最後結合地面調查，針對前期建立的監測樣區與另外設置之臨時樣區進行地被植物調查、木本植物健康度調查。最後統整研究成果擬定火燒影響區域監測策略。
三、重要發現
(一) 火燒風險評估
檢視火燒前的氣候條件，在2021年5月時，杜鵑營地區域自2019年7月起已維持了21個月的相對乾旱期，此外水分條件在2021年4月時更達到極端乾旱條件，顯示區域屬於森林火燒高風險的情況。同時，杜鵑營地的延燒區域內，有86.19%的植被處於水分匱乏的狀態，當中約有4.02%的植被屬於極端乾旱的情況。綜合地形因子的風險評估結果，顯示杜鵑營地大火時，確實在高風險區域，林份受到較嚴重的危害，地形效應確實加劇火燒蔓延與火燒嚴重程度。顯示杜鵑營地火燒雖然是人禍，但氣候條件與地形因素致使火燒蔓延，加劇嚴重程度。
(二) 火燒恢復情況評估
自NDVI 分析結果檢視區域內的植群生長情況，顯示在2022年8月時區域內的植群普遍陷入衰退，至2023年1－4月時NDVI 數值並未好轉，直到8－10月時，火燒核心區的NDVIII數值略為提高，但是推移帶則有衰退的跡象。同時LAI 與GPP 數值顯示在火燒後，代表樹冠密度的LAI 數值大幅下降，同時GPP 也有減少的趨勢。監測樣區的調查結果顯示，火燒區域內仍有冠層木陸續死亡，存活的林木的冠層密度下降與枯梢率上升，死亡植株可能在火燒後健康度下降，對逆境的抵抗力降低，因此在乾旱影響下陸續死亡。同時，研究團隊發現火燒區域的地被層植物開始重新拓植，玉山箭竹的覆蓋率上升，樣區中的物種數增加，同時也發現高密度的臺灣二葉松小苗。代表在乾旱影響下，臺灣二葉松的更新機制仍在運作。
(三) 綜合評估
總和來說，杜鵑營地火燒跡地具有自然復育的優勢與潛在威脅。優勢方面，火燒區域的鑲嵌狀態及地表火的發生有利於自然復育。殘存的樹木與地被植物有助於加速植被恢復，並為野生
動物提供棲息地。同時，殘留木可減少直射光並保持土壤結構，有助於降低土壤流失與崩塌的風險。潛在威脅包括持續乾旱、病蟲害與植物生理作用的受損。氣候變遷下的極端高溫與乾旱事件也可能對植物造成直接威脅，導致植群退化。
四、主要建議事項
本研究建議，火燒跡地應採用自然復育方式，並進行持續的監測與評估，以了解復育進度與植群健康狀態。此外，也需注意極端天氣事件對生態系的影響，以及病蟲害可能對樹木造成的損害。本研究另根據前期研究前人研究提出結合三種面向的監測模式，分別為氣候監測、衛星影像監測與地面樣區監測。氣候監測作為整體復育情況的背景值，評估火燒區域的水分狀態。衛星影像用以評估火燒區域的整體發展情況，可以獲得較即時的資訊，並可評估氣候變動對植群的影響。地面調查可得到詳細的更新狀況，分別針對冠層留存木的健康以及地被更新情況監測，以了解留存木生長情況以及林下小苗更新情形。俟林下小苗成熟後，降低監測頻率，並以苗木為監測主軸，持續監測復育情況。
英文摘要
Purpose of the Project
On the morning of May 16, 2021, it was reported that a forest fire was caused near the
Dujyuan Campground at the Batongguan historic trail in Yushan National Park due to the careless
use of fire by mountain climbers, which lasted for 12 days and was extinguished on May 27, 2021.
The damaged area is about 22.1 hectares, and the area of extended burn is about 79.7 hectares. The
damaged area was about 22.1 hectares, and the extended burn was about 79.7 hectares.
For 2021－2022, the severity of the fires has been assessed, and 13 long-term monitoring plots
have been established to monitor the restoration of the burned area. This year, we continued to mon-
itor the restoration of the burned area and the forest vegetation. Furthermore, we suggest a medium-
and long-term monitoring model for the burned forests in the region.
Research methods
In this study, we first evaluate the risk factors of fire in the Dujyuan Campground using the
climatic conditions, moisture conditions, and topographic factors before the fire. Then, we divided
the fire-affected areas into the fire-core area, the ecotone, and the undisturbed area and examined
the trend of the overall vegetation changes before and after the fire by using the standardized
vegetation index (NDVI), the leaf area index (LAI), and the gross primary productivity (GPP) from
the satellite data. Finally, wild field surveys were combined with understory surveys and woody
plant health surveys in the monitoring plots and temporary plots. Eventually, the study results were
consolidated to formulate a monitoring strategy for the fire-affected areas.
Result and discussion
Reviewing the pre-fire climatic conditions, in May 2021, the Dujyuan Campground had sus-
tained a relatively dry period of 21 months since July 2019, in addition to moisture conditions
reaching extreme drought conditions in April 2021, suggesting that the area was at high risk of for-
est fire. At the same time, 86.19% of the vegetation in the extended burn area was under moisture
deprivation, of which about 4.02% was under extreme drought conditions. The results of the fire
risk assessment of the integrated terrain factor showed that the Dujyuan Campground was indeed in
a high fire-risk area, and the topography effect did aggravate the spread and the severity of the fire.
Although the fire was a man-made disaster, the climatic conditions and topographic factors contrib-
uted to the spread of the fire and the severity of the fire.
The result from the NDVI analyses showed that the vegetation in the region was generally in
decline after the fire. Moreover, the NDVI values continuously decreased to April 2023. In August-
October, the NDVI values improved slightly in the fire-core area, but it showed a declining trend in
the ecotone. Meanwhile, the LAI and GPP values showed that the LAI value, which represents theIV
density of the tree canopy, decreased significantly after the fire, and the GPP also showed a de-
creased tendency. The survey results in the monitoring plot showed that there were still some cano-
py trees dying in the burned area, the canopy density of trees decreased, and the dieback rate in-
creased. The trees might be less resistant to adversity after the fire, so they might die due to the in-
fluence of the coming drought. At the same time, the research team found that the understory plants
in the burned area began to recover, the coverage of Yushania niitakayamensis increased, the spe-
cies richness and diversity in the sample area increased, and a high density of Pinus taiwanensis
saplings was also found. This indicates that the regeneration mechanism of Pinus taiwanensis is still
functioning under the influence of drought.
Suggestion
This research proposed a combination of three monitoring modes based on previous studies
and research results, namely, climate monitoring, satellite monitoring, and wild field monitoring.
Climate monitoring is used as the background value of the overall restoration situation to assess the
moisture status of the burned area. Satellite imagery is used to assess the overall development of
vegetation in the burned area, to obtain more real-time information, and to evaluate the impact of
climate change on the vegetation. Wild field monitoring provides detailed information on regenera-
tion conditions, monitoring the health of the retained wood in the canopy.
