牛樟與樟樹之木材徑向生長與樹冠物候

Wood Radial Growth and Tree Crown Phenology of Cinnamomum kanehirae Hayata and C. camphora (L.) Presl

蔡謦竹(Ching-Chu Tsai)

指導教授 ： 黃玲瓏

共同指導教授 ： 高文媛(Wen-Yuan Kao)

國立臺灣大學/生命科學院/生態學與演化生物學研究所/博士(2020年)

https://doi.org/10.6342/NTU202000606

摘要

在四季變化較不明顯的地區，木材徑向生長除氣候因子之外，也受到樹冠物候的調節。木材徑向生長曲線記錄樹輪形成的時序和生長量，同時反應出氣候和樹冠物候的影響。前人探討徑向生長曲線與樹冠物候的相關研究，主要以溫帶、北寒林和高山地區的針葉樹或落葉闊葉樹為主，極少針對亞熱帶低海拔的常綠闊葉樹。本論文研究台灣中、低海拔具代表性的二種常綠闊葉樹種之木材徑向生長和樹冠物候：牛樟（Cinnamomum kanehirae）為台灣特有瀕危樹種，極具保育價值；樟樹（C. camphora）是台灣原生種，分佈廣泛適合用於研究不同地域的物候差異。
在本研究中，每兩週一次以插針處理或微型年輪錐取樣，連續監測牛樟與樟樹的徑向生長，長達一至三年。所得資料以半母數迴歸法建立整體徑向生長曲線模型。另以岡波茨函數、邏輯函數與平滑樣條法對每一棵樹、每一年份分別配適生長曲線，並取得最大生長量、即時生長速率與最大生長速率等參數。再將配適參數與徑向生長季初始、結束與長度等物候資訊一同進行分析。此外，本研究也探索氣象因子（即溫度、降雨量與相對濕度）和樹冠物候時序（即萌芽、開花、著果、落果、展葉、葉凋亡）分別與徑向生長的關係，以辨別重要的控制因子。
牛樟具有S形徑向生長曲線，其徑向生長開始（積日126 ± 22.4, mean ± SD, n =18），比用溫帶林、北寒和高山針葉樹種之模型所預測的生長季晚。此生長季延遲可能肇因於徑向生長與樹冠物候相（即密集發生於二至六月間開花、著果與展葉期）間的資源競爭。物候相之間高度重疊亦可能造成嚴重的牛樟果實自疏與提前落果，導致信賢苗圃牛樟人工林結果率極低。樟樹的徑向生長曲線具有季中遲緩的現象，此遲緩期正值夏季展葉期，可能反映兩者間的資源競爭。樟樹的徑向生長較預期早（積日72 ± 25, n = 6），可能和展葉期間較分散、樹冠物候相重疊較少所導致春季資源競爭較緩和有關。牛樟和樟樹的即時徑向生長速率和氣溫呈現正相關，而和降雨量或相對濕度則無顯著相關。
本研究另有三項發現：（1）相較於共優勢樹，牛樟優勢樹的徑向生長對溫度敏感度較高，可能因此較易受到氣候變遷的衝擊。（2）2011年秋季的月總日照時數較歷年短，可能延遲來年牛樟開花季並縮短徑向生長季。（3）台灣北部都市樟樹行道樹開花季較郊區樟樹林木晚，此現象與溫帶典型的都市效應相反。
本論文首次建立低海拔亞熱帶常綠闊葉樹的木材徑向生長曲線，結果顯示研究樹種與溫帶樹種間有差異。研究成果有助於解析台灣本地低海拔闊葉樹種的樹輪資訊。此外，都市與郊區樹木的物候差異可作為都市林管理規劃的參考。

關鍵字

樟樹 ； 牛樟 ； 葉狀花序 ； 資源分配 ； 樹冠物候 ； 林木社會階層 ； 徑向生長

並列摘要

Besides climatic factors, the wood radial growth is also regulated by tree crown phenology. The phenological regulation is important in regions with inapparent seasonality. Wood radial growth curve contains information about when and how the climate and crown phenology influence tree-ring formation. The studies of wood radial growth curve and tree crown phenology have focused mostly on conifers and deciduous broadleaf trees in temperate, boreal, and alpine ecosystems. In contrast, few were conducted on evergreen broadleaf trees in low-altitude subtropical forests. This study worked on two evergreen broadleaf trees with ecological representativeness in Taiwan. Stout camphor tree (Cinnamomum kanehirae Hayata) is an endemic, endangered species with high conservation value in Taiwan, while camphor laurel (C. camphora) is a native, widespread species with potential usage in studying geographic variation of phenology.
The wood radial increments were monitored by either pinning or micro-coring method on a biweekly basis for one to three years. Radial growth curves of trees were modeled collectively by semiparametric regression and fitted individually by using Gompertz function, logistic function, and cubic smoothing spline method. The maximum radial growth, instantaneous rate of radial growth and maximum radial growth rate were extracted. The relationships between these fitting parameters and the phenological parameters (i.e., onset, cessation, and length of the radial growing season) were analyzed. Besides, the climate data (i.e., temperature, precipitation, and relative humidity) and tree crown phenophases (i.e., budburst, bloom, fruit set, fruit drop, leaf flush, and leaf discoloration) were explored to identify the controlling factors of wood radial growth.
Stout camphor trees exhibited a sigmoid wood radial growth curve. The averaged onset of the radial growing season (Day Of the Year 126 ± 22.4 SD) was later than the extrapolation (DOY 100) using a model built for conifers in cold ecosystems. This surprising delay likely resulted from the competitive resource demands of bloom, fruit set, and leaf flushes within February and June. The overlapped phenophases might also lead to severe fruit thinning and subsequently premature abortion. On the other hand, camphor laurels had growth retardation amid the radial growing season. The retardation period corresponds to the leaf flush in summer, implying a resource competition. The onset of camphor laurels (DOY 72 ± 25 SD) was earlier than expected, possibly reflecting a less intensive resource competition in spring due to the evenly paced leaf flushes. For both studied species, the instantaneous rate of radial growth was related to air temperature in different patterns, but not to precipitation.
This study presented three additional findings. (1) The radial growth of dominant stout camphor trees was more sensitive to air temperature than codominant trees. Thus, the dominant trees will be more likely impacted by climate change. (2) The reduced sunshine hours in the autumn of 2011 was followed by the delayed flowering and truncated radial growing season of stout camphor trees in 2012. This implies that a climatic carry-over effect might also regulate tree crown phenophases and radial growth. (3) For camphor laurels, street trees bloomed later than rural trees, which contradicted to the results of temperate region.
In conclusion, wood radial growth curves for evergreen species in low-altitude subtropical Taiwan are constructed for the first time. The result highlight the different pattern of wood radial growth between local species and temperate trees. The local information of radial growing season may facilitate the interpretation of tree-ring profile. Otherwise, the knowledge of urban-rural differentiation in phenology may help in designing a more desirable plan in managing urban forests.

並列關鍵字

Cinnamomum camphora ； Cinnamomum kanehirae ； Leafy inflorescence ； Resource allocation ； Tree crown phenology ； Tree social class ； Wood radial growth

參考文獻

Rathcke B, Lacey EP (1985) Phenological patterns of terrestrial plants. Annu Rev Ecol Syst 16:179–214. doi: 10.1146/annurev.es.16.110185.001143

Akaike H (1973) Information theory and an extension of the maximum likelihood principle. In: Petran BN, Csaki F (eds) Second International Symposium on Information Theory. Akademiai Kiadi, pp 267–281

Ali NS, Trivedi C (2011) Botanic gardens and climate change: A review of scientific activities at the Royal Botanic Gardens, Kew. Biodivers Conserv 20:295–307. doi: 10.1007/s10531-010-9944-4

Antonucci S, Rossi S, Deslauriers A, et al (2015) Synchronisms and correlations of spring phenology between apical and lateral meristems in two boreal conifers. Tree Physiol 35:1086–1094. doi: 10.1093/treephys/tpv077

Ao Z-H, Xu Z-H, Lu Z-M, et al (2009) Niuchangchih (Antrodia camphorata) and its potential in treating liver diseases. J Ethnopharmacol 121:194–212. doi: 10.1016/j.jep.2008.10.039