車諾比十字樹

這棵樹的形狀像三叉戟或十字，位於車諾比核電廠4號反應堆1600公尺處，在第二次世界大戰，德國軍隊用來吊死俄斯士兵與游擊隊，也被稱為游擊隊之樹(partisan’s tree)。車諾比核災發生後，這棵樹也因過多輻射而死亡，2005 年左右被砍倒。

車諾比的聖以利亞教堂內畫作也出現這棵樹 

車諾比博物館以這棵樹為主視覺

資料來源:

https://www.forgottenchernobyl.net/a-miracle-in-chernobyl-story-of-the-pine-tree

 花旗松的年輪

(A)花旗松(Pseudotsuga menziesii)誕生。 (B) 生長迅速，形成較寬、均勻的年輪。 (C) “反應木”有樹枝壓到樹木而產生。 (D)生長被其它樹檔住太陽。 (E) 競爭樹木被移除，再次快速生長。 (F) 火燒傷了樹。 (G)長時間的干旱造成狹窄的年輪。 (H)可能是由昆蟲引起的狹窄的年輪。

growth of Douglas fir tree

Annual growth rings of a tree trunk

(A) A Douglas fir (Pseudotsuga menziesii) is born. (B) Growth is rapid, forming relatively broad, even rings. (C) “Reaction wood” is formed to help support the tree after something fell against it. (D) Growth is straight but crowded by other trees. (E) Competing trees are removed, and growth is again rapid. (F) Fire scars the tree. (G) Narrow rings are caused, probably by a prolonged dry spell. (H) Narrow rings may have been caused by an insect.

資料來源:

https://www.britannica.com/science/growth-ring-plant-anatomy

 台大師盼搶救百年黃檀 文學院持續溝通凝聚共識

（中央社記者許秩維台北6日電）台大文學院中庭的百年印度黃檀染上「褐根病」，經評估後規劃移除。台大植病系兼任教授孫岩章近日在樹下靜坐，呼籲用注射治療搶救黃檀；台大文學院則說將持續溝通並凝聚共識。

台灣大學文學院中庭的印度黃檀自日本帝國大學時期種下，至今已有百年歷史。詩人楊牧曾為它寫下「學院之樹」一詩，銘刻老樹昂揚且生生不息的精神，林文月等多名作家的文字紀錄裡，也曾出現印度黃檀。

台大文學院和總務處去年4月觀察到黃檀的葉片異常枯萎，經台大植物教學醫院檢驗後為褐根病且病況嚴重，雖經加強灌水、施肥、施藥等救治仍無起色。

台北市文化局去年8月也請樹木保護委員會代表現場會勘，判斷樹已枯死，並請台大文學院儘速移除樹木，文學院也於今年3月30日舉辦印度黃檀的告別儀式，並規劃近期內要移除黃檀，但目前僅先修剪枯枝，以維護周邊人員動線安全。

台大植物病理與微生物系兼任教授孫岩章近日發起救樹行動，也前往文學院的印度黃檀樹下靜坐，呼籲台大放下刀斧、讓樹醫免費為百年黃檀注射治療，搶救印度黃檀。

孫岩章今天告訴中央社記者，印度黃檀是許多文學院師生難以忘懷的歷史樹木，卻因染褐根病，將於近期被「連根移除」，但珍貴樹木一旦被移除，永遠無法複製回來，他身為樹木醫生之一，願挺身免費相救這個珍貴歷史樹木。

孫岩章表示，他近10年參與褐根病的治療技術研發，於2015年研發「淺孔注射法」來治療樹木褐根病，並曾成功搶救台中的老樹；而印度黃檀有8個主幹，其中4個主幹還有活的枝條，用淺孔注射藥劑仍有救活的機會，希望台大暫勿移除黃檀，讓他能及早為黃檀治療

台大文學院院長黃慕萱接受中央社記者訪問時表示，文學院對黃檀的感情很深，曾多次尋求專家協助救治，日前也再請台大植病系評估，但判斷黃檀根部已腐爛，若不移除，中庭其他樹可能會被傳染，且梅雨季節將至，枯枝掉落或黃檀傾倒可能造成人員受傷，才不得不做出移樹的沉痛決定。

黃慕萱提到，台大文學院2名副院長昨天有和孫岩章溝通，並完整告知黃檀的情況，但孫老師還是無法接受，文學院會持續溝通並凝聚共識，再來決定如何處理黃檀。（編輯：張芷瑄）1110406

資料來源:

https://www.cna.com.tw/news/ahel/202204060351.aspx?utm_source=cna.app&utm_medium=app&utm_campaign=inapp_share

 Newly Naturalized and Rediscovered Decalobanthus (Convolvulaceae) Species from Taiwan 

臺灣金鐘藤屬(旋花科)的新歸化種與再發現種 

Po-Hao Chen1, An-Ching Chung2, Shih-Siang Wong3, Zhi-Xiang Chang4, 

Shih-Wen Chung5 and Wei-Jie Huang5

陳柏豪1 、鍾安晴2*、翁士翔3、張智翔4、鐘詩文5、黃偉傑5 

1 Graduate Institute of Bioresources, National Pingtung University of Science and Technology, Pingtung, Taiwan, R.O.C. (國立 屏東科技大學農學院生物資源博士班，屏東，臺灣，中華民國) 

2 Liouguei Research Center, Taiwan Forestry Research Institute, Kaohsiung, Taiwan, R.O.C. (行政院農業委員會林業試驗所六 龜研究中心，高雄，臺灣，中華民國) 

3 Tree Walker Arboris Company Limited, Changhua, Taiwan, R.O.C. (樹沃客樹藝有限公司，彰化，臺灣，中華民國)

4 Fushan Research Center, Taiwan Forestry Research Institute, Yilan, Taiwan, R.O.C. (行政院農業委員會林業試驗所福山研究 

中心，宜蘭，臺灣，中華民國)

5 Botanical Garden Division, Taiwan Forestry Research Institute, Taipei, Taiwan, R.O.C. (行政院農業委員會林業試驗所植物 

園組，臺北，臺灣，中華民國)

*Corresponding author(通訊作者): An-Ching Chung, e-mail: cac335@tfri.gov.tw 

Abstract: Merremia s.l. has been proved polyphyly, and is now delimitated into 4 genera: Camonea Raf., Merremia Dennst. ex Endl., Decalobanthus Ooststr. and Distimake Raf. This article reports the two species of the genus Decalobanthus in Taiwan, the red flower one D. similis (Elmer) A. R. Simões & Staples, and the yellow flower one D. boisianus (Gagnep.) A. R. Simões & Staples var. boisianus. D. similis, the sole native species of the genus Decalo- banthus in Taiwan, had not been recorded in local flora since its first report in 1971, and was rediscovered in 2021. Also, a population of D. boisianus var. boisianus was newly found at the seashore in northern Taiwan in recent years, and is extremely aggressive in the field and would probably become a seriously invasive plant in Taiwan. Thus, it is important to continually monitor the expansion of D. boisianus var. boisianus population in Taiwan and to prevent it endangering the native plant communities. 

摘要:過去廣義的菜欒藤屬被證實為多系群，現今則劃分為4個屬:耳 節藤屬(Camonea Raf.)、菜欒藤屬 (Merremia Dennst. ex Endl.)、金鐘藤屬 (Decalobanthus Ooststr.)、萼龍藤屬(Distimake Raf.)。本文報導臺灣金鐘藤 

屬兩個物種─紅花的紅花金鐘藤(D. similis (Elmer) A. R. Simões & Staples) 及黃花的金鐘藤(D. boisianus (Gagnep.) A. R. Simões & Staples var. boi- sianus)。其中紅花金鐘藤在1971年發表後再無其他採集紀錄，直到2021 年再次發現其族群。另外於臺灣北部沿海地區發現金鐘藤的族群，於野 地是非常強勢的外來種，極有可能成為嚴重的入侵種，未來需持續監測 其擴散情形，以免對原生植物造成危害。 

Keywords: Convolvulaceae, Decalobanthus, invasive species, Merremia, Taiwan 

關鍵詞:旋花科、金鐘藤屬、入侵種、菜欒藤屬、臺灣 

Introduction 

The family Convolvulaceae comprising 1,660 species of 53 genera could be separated into 12 tribes (Staples and Brummitt, 2007; Christenhusz and Byng, 2016), of which the tribe Merremieae was divided into 9 genera in the current research (Simões and Staples, 2017). In the past, the genus Merremia in Merremieae consisted of over 1,000 species worldwide (Staples, 2010), in which 11 species were recorded in Taiwan, including 6 native and 5 naturalized species: M. tuberosa (L.) Rendle (Staples and Yang, 1998); M. dissecta (Jacq.) Hallier f. (Tsai et al., 2010); M. cissoides (Lam.) Hallier f. (Ko and Liu, 2011); M. umbellata (L.) Hallier f. (Chao et al., 2017) and M. quinquefolia (L.) Hallier f. (Chung et al., 2017). Recently, molecular phylogenetic evidence has shown that the genus Merremia was polyphyly and could be delimitated into 4 genera: Camonea Raf., Merremia Dennst. ex Endl., Decalobanthus Ooststr. and Distimake Raf. (Simões and Staples, 2017). Therefore, the species of the Merremia s.l. in Taiwan now include Camonea [C. umbellata (L.) A. R. Simões & Staples, C. vitifolia (Burm. f.) A. R. Simões & Staples]; Decalobanthus [D. similis (Elmer) A. R. Simões & Staples]; Disti- make [D. cissoides (Lam.) A. R. Simões & Staples, D. dissectus (Jacq.) A. R. Simões & Staples, D. quinatus (R.Br.) A. R. Simões & Staples, D. quinquefolius (L.) A. R. Simões & Staples, D. tuberosus (L.) A. R. Simões & Staples]; Merremia s.s. [ M. gemella (Burm.f.) Hallier f., M. hed- eracea (Burm.f.) Hallier f., M. hirta (L.) Merr.]. 

Among the 17 species of the genus Decalobanthus which mainly distributed in Asia and the Pacific region (Simões and Staples, 2017; Simões et al., 2020), only one species, D. simi- lis, has been recorded in Taiwan with no further collection after Chang (1971) first reported it in Bulletin of Taiwan Provincial Pingtung Institute of Agriculture. It was not until Dec 11, 2021 that Mr. Ming-Yu Kuo (郭明裕) rediscovered the population in Fenshuiling, Manzhou Township, Pingtung County, Taiwan. Of this taxon found in 2021, the characteristics e.g. leaves large, inflorescence corymbose cymes, sepals elliptic, glabrous, corolla red, corresponded to which Chang (1971) described. In this article, we provide detailed color photographs and additional voucher specimens of D. similis to assist in its identification. 

Moreover, during our recent field investigations, an unknown species of Decalobanthus was found at the seashore in northern Taiwan. Of this taxon, the inflorescences corymbose cymes, sepals broadly ovate, equal, outer 2 yellowish pubescent on abaxial surface, and corolla yellow. After detailed study in its morphology and comparison with known literatures (Van Ooststroom and Hoogland, 1953; Fang and Staples, 1995; Simões et al., 2020), we identified this species as Decalobanthus boisianus (Gagnep.) A. R. Simões & Staples var. boisianus, which is native from southern China, northern Vietnam to Laos. In this article, we describe it as a newly naturalized plant in Taiwan and provide taxonomic description and detailed color photographs to assist in its identification. 

Taxonomic treatment 

1. Decalobanthus boisianus (Gagnep.) A. R. Simões & Staples var. boisianus, Bot. J. Linn. Soc. 183(4): 569. 2017. 

金鐘藤 Fig. 1 

Basionym: Ipomoea boisiana Gagnep., Notul. Syst. (Paris) 3: 141. 1915.

Type: VIETNAM. Montagnes du Caï Kunh, Bois 138 (syntype P, P00608899 image!); Mt. Cha- Pa, Lecomte et Finet s.n. (syntype P, P03536883 image!; syntype P, P03536884 image!). LAOS. near Ken-trap, Spire 1049 (syntype P, P03536873 image!). 

Liana, whole plants with white latex; stems dextrorsely twining, terete, glabrous; young stems fistulose and yellowish pubescent. Leaves alternate, ovate to nearly orbicular, 8–28 cm 

× 6.5–24.5 cm, base cordate, margins entire, apex caudate, glabrous on both surfaces, 7–9 pinnate lateral veins; petiole 2–11.5 cm long, glabrous. Corymbose cymes axillary, 5–16 cm long; bracts lanceolate or narrowly triangular, ca. 3 mm long, densely yellowish pubescent, fugacious; peduncles 2.5–10 cm long, pubescent or glabrous; pedicels 1–1.5 cm long, enlarged in fruit. Sepals broadly ovate or nearly orbicular, equal, 6–7 mm × 5–6 mm, apex mucronate; outer 2 yellowish pubescent on abaxial surface; inner 3 glabrous. Corolla yellow, campanulate, ca. 2 cm long, ca. 3 cm in diameter, midpetaline bands yellowish pubescent on abaxial surface, limb ondulate; stamens 5, included; filaments 1–1.1 cm long, inserted at the mouth of the tube, 4 mm long, with 2 longitudinal pubescent lines below insertion; anthers basifixed, ca. 3 mm long, twisted; pistil 1, included, 1.2 cm long; stigma capitate, 2-lobed, white; ovary conical, green, glabrous, 1 mm long, 2-loculed, 4-ovuled, base with annular disc. Capsule subglobose, 1–1.2 cm in diameter, glabrous. Seeds 4, broadly trigonous-ovoid, 5 mm long, densely scaly pubescent along angles. 

Specimens examined: TAIWAN. New Taipei City, Bali Dist., 21 October, 2021, S.-W. Chung & W.-J. Huang 14929 (TAIF); 21 October, 2021, Z.-X. Chang ZXC002691 (TAIF); 30 October, 2021, P.-H. Chen & A.-C. Chung 3429~ 3434 (TAIE).

2. Decalobanthus similis (Elmer) A. R. Simões & Staples, Bot. J. Linn. Soc. 183(4): 571. 

2017. 

Basionym: Merremia similis Elmer, Leafl. Philipp. Bot. 1: 335. 1908; Chang, Bull. Taiwan Prov. Ping. Inst. Agr. 12: 15. 1971; Chang, Fl. Taiwan 4: 385. 1978; Staples and Yang, Fl. Taiwan, 2nd ed 4: 379. 1998.

Type: PHILIPPINES. Leyte, Palo, A.D.E. Elmer 7341 (isotype E, E00273913 image!, isotype K000830840 image!, isotype NY, NY00336585 image!). 

紅花金鐘藤Fig. 2 Specimens examined: TAIWAN. Pingtung County, Manzhou Township, Fenshuiling, 10 Dec., 1960, C.-E. Chang 2467 (PPI); 11 Jan, 1971, C.-E. Chang 6760 (PPI); 14 March, 1971, C.-E. Chang s.n. (PPI); 15 Dec., 2021, P.-H. Chen 3450 (TAIE); Z-X. Chang ZXC002831 (TAIF); 17 

Dec., 2021, S.-W. Chung 14949 (TAIF). 

Discussion 

Decalobanthus boisianus 

Decalobanthus boisianus has three varieties, including var. boisianus, var. fulvopilosus (Gagnep.) A. R. Simões & Staples distributed from southern China to northern Vietnam and var. sumatranus (Ooststr.) A. R. Simões & Staples distributed in Indonesia (Sumatra) (Simões et al., 2020). The branchlets, petioles, leaves, peduncles and pedicels are glabrous or yellowish pubescent in var. boisianus (Fang and Staples, 1995), namely the taxon naturalized in Taiwan, while being grayish-yellow tomentose or fulvous pubescent in the other two varieties (Van Ooststroom and Hoogland, 1953; Fang and Staples, 1995). The latter two varieties could be further distinguished from each other by the much longer hairs in var. fulvopilosa and the much shorter and less dense hairs in var. sumatranus (Van Ooststroom, 1939). 

Originally distributed in Hainan Island, the border of China and Vietnam to Laos, and Sarawak to east Kalimantan, D. boisianus var. boisianus had gradually spread out (Wang et al., 2005). It could reproduce both sexually and asexually, and is excellent in asexual reproduction (Lian et al., 2007). D. boisianus var. boisianus is a very aggressive species that grows fast and climbs strongly, covering the canopy of forest broadly, which could damage all the trees (Wu et al., 2007; Huang et al., 2013; Huang et al., 2015). Seeds of D. boisianus var. boisianus could germinate under the dense forest, but most of the seedlings fail to survive (Huang et al., 2013), thus it could be shade-intolerant. Seeds are able to drift and can be dispersed by seawater (Wu et al., 2007), thus this new population of D. boisianus var. boisianus probably arrived Taiwan through the ocean current. 

This population of D. boisianus var. boisianus in Taiwan was first recorded by the third author on 12 January 2019. Street view images available in Google Map (https://maps.google. com.tw; accessed 4 December 2021) revealed that the population had appeared and covered the canopy on roadside at least since 9 November 2019. In Taiwan, though it has been found only one location at the seashore of Bali, but it spread vastly and cover the bare ground, orchard, secondary forest, and alley trees. According to our filed survey, there is potential for D. boi- sianus var. boisianus to be seriously invasive in Taiwan because the habitat is almost covered by 

it (Fig.1A). It is important to continually monitor the expansion of D. boisianus var. boisianus 

population in Taiwan and to prevent it endangering the native plant communities. 

Decalobanthus similis 

Decalobanthus similis is distributed in Philippines (Leyte, Luzon, Mindanao, Panay, Samar, Sibuyan) and Taiwan (Staples, 2010). In Taiwan, there was only one record in Fenshuiling, Hengchun Peninsula from the first report (Chang, 1971), making it be suggested as Critically Endangered (CR) in the Red List of Taiwan Plants (Editorial Committee of the Red List of Taiwan Plants, 2017). It was not until this year that the population in Fenshuiling was rediscovered. Being a large liana, the stem diameter of D. similis could be up to 10 cm in the field, and its leaves could reach 25 cm in length, covering the canopy of the habitat (Fig.2A). While the plants seem to thrive in this area less than 0.2 ha, we did not find seedling regeneration of D. similis in the understory, but observed the capsules matured in last year, without seeds now and persistent at the branches. As for that, it is necessary to investigate nearby habitats to clarify the current situation of its population in Taiwan. 

References 

Chang, C. E., 1971. Unrecorded plants from Taiwan (VI). Bulletin of Taiwan Provincial Pingtung Institute of Agriculture 12: 13–18. 

Chang, C. E., 1978. Convolvulaceae. In: Li, H. L. et al. (eds.), Flora of Taiwan. Vol. 4. Pp. 347– 389. Epoch Publishing Co., Taipei. 

Chao, C. T., Chen P. H. and Wang, C. M., 2017. Two newly naturalized plant species in Taiwan: Astraea lobata and Merremia umbellata. Quarterly Journal of Forest Research 39(4): 285– 294. 

Christenhusz, M. J. M. and Byng, J. W., 2016. The number of known plants species in the world and its annual increase. Phytotaxa 261(3): 201–217. 

Chung, S. W., Hsu, T. C. and Chung, A. C., 2017. Merremia quinquefolia (Convolvulaceae), a newly naturalized plant in Taiwan. Taiwan Journal of Biodiversity 19(2): 123–129. 

Editorial Committee of the Red List of Taiwan Plants. 2017. The Red List of Vascular Plants of Taiwan, 2017. Endemic Species Research Institute, Forestry Bureau, Council of Agriculture, Executive Yuan and Taiwan Society of Plant Systematics, Nantou. 

Fang, R. C. and Staples, G., 1995. Convolvulaceae. In: Wu, C. Y. and Raven, P. H. (eds.), Flora of China, Vol. 16. Pp. 271–325. Science Press, Beijing, & Missouri Botanical Garden Press, St. Louis. 

Huang, Q. Q., Shen, Y. D., Fan, Z. W., Li, X. X., Song, X., Cheng, H. T. and Hou, Y. P., 2013. Effects of soil from different forest types in Wuzhi Mountain on the seedling growth of Merremia boisiana. Ecology and Environment Sciences 22: 95–99. 

Huang, Q. Q., Shen, Y. D., Li, X. X., Zhang, G. L., Huang, D. D. and Fan, Z. W., 2015. Effects of light and water availability on the morphology and allelopathy of the native outbreak species Merremia boisiana (Gagnep.) Oostr. Chinese Journal of Ecology 34(2): 438–444. 

Ko, Y. N. and Liu, H. Y., 2011. Merremia cissoids (Lam.) Hallier f. (Convolvulaceae), a newly naturalized plant to Taiwan. Taiwan Journal of Biodiversity 13(4): 345–348. 

Lian, J. Y., Cao, H. L., Wang, Z. G., Li, J., Ye, W. H. and Su, J., 2007. The community characteristics for invading damage of the forest killer-Merremia boisiana. Guihaia 27(3): 482–486. 

Liang, W. S., Fang, T. S., Yu, H. B. and Wang, Z., 2012. Risk analysis of Merremia boisiana in China. Guangdong Forestry Science and Technology 26(3): 42–45. 

Simões, A. R. and Staples., G. W., 2017. Dissolution of Convolvulaceae tribe Merremieae and a new classification of the constituent genera. Botanical Journal of the Linnean Society 183: 561–586. 

Simões, A. R., Pisuttimarn, P., Pornpongrungrueng, P. and Chatrou, L. W., 2020. New combinations in Decalobanthus (Convolvulaceae). Kew Bulletin 75(4): 1–6. 

Staples, G. W. and Yang, S. Z., 1998. Convolvulaceae. In: Huang, T. C. et al. (eds.), Flora of Taiwan, 2nd ed. Vol. 4. Pp. 341–384. Editorial Committee of the Flora of Taiwan, Department of Botany, NTU, Taipei, Taiwan. 

Staples, G. W., 2010. A checklist of Merremia (Convolvulaceae) in Astralasia and the Pacific. Gardens’ Bulletin Singapore 61(2): 483–522. 

Staples, G. W. and Brummitt, R. K., 2007. Convolvulaceae. In: Heywood, V. H., Brummit, R. K., Culham, A. and Seberg, O. (eds.), Flowering Plant Families of the World. Kew: Royal Botanic Gardens 108–110. 

Tsai, Y. C., Lee, P. J., Chang, Y. H. and Hsieh, T. H., 2010. Merremia dissecta (Jacq.) H. Hallier., a newly naturalized species in Taiwan. Journal of Ecology and Environmental Sciences 3 (2): 1–7. 

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(ed.), Flora Malesiana Ser. I, Vol. 4. Pp. 388–512. Noordhoff-Kolff, Djarkata.

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Ecology and Environment 14: 451–454.

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of Merremia boisiana in Hainan Province, China. Guangdong Forestry Science and Technology 23(1): 83–86. 

資料來源:

國立臺灣博物館學刊 

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 inReach® Mini 2 Black

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Share your location with loved ones back home at any time using your MapShare™ page or with your coordinates embedded in your messages.

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Share your location with loved ones back home at any time using your MapShare™ page or with your coordinates embedded in your messages.

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資料來源:

https://www.garmin.com/en-US/p/765374/pn/010-02602-01

 Using nature’s structures in wooden buildings

Tools for designing with forked tree branches

NANCY W. STAUFFERJANUARY 12, 2022MITEI

This photo shows some of the proposed tree forks in the researchers’ inventory. Their goal is to support the so-called circular economy of materials, an approach to sustainability that calls for “upcycling” such waste materials, in this case, by using them as structural joints in timber buildings. Credit: Felix Amtsberg

IN BRIEF

Forks in tree trunks and branches are exceptionally strong, yet they are rejected in timber construction because they are not straight. MIT researchers have developed an approach that enables architects to use discarded tree forks as load-bearing joints in their structures. Using digital and computational methods, the MIT process distributes a collection of discarded tree forks among the Y-shaped nodes in an architectural design, allocating them so as to maximize the use of the inherent strength in the wood fiber—and reallocating them instantly if the architect changes the design geometry. Computer-driven robotic machining adjusts and marks the forks for easy assembly with straight wooden elements. Using recovered material from felled city trees, the MIT team used this process to create part of a wooden pavilion destined for installation at the site of the felled trees.

Concern about climate change has focused significant attention on the buildings sector, in particular on the extraction and processing of construction materials. The concrete and steel industries together are responsible for as much as 15% of global carbon dioxide emissions. In contrast, wood provides a natural form of carbon sequestration, so there’s a move to use timber instead. Indeed, some countries are calling for public buildings to be made at least partly from timber, and large-scale timber buildings have been appearing around the world.

Observing those trends, Caitlin Mueller ’07, SM ’14, PhD ’14, an associate professor of architecture and civil and environmental engineering in the Building Technology Program at MIT, sees an opportunity for further sustainability gains. As the timber industry seeks to produce wooden replacements for traditional concrete and steel elements, the focus is on harvesting the straight sections of trees. Irregular sections such as knots and forks are turned into pellets and burned, or ground up to make garden mulch, which will decompose within a few years; both approaches release the carbon trapped in the wood to the atmosphere.

For the past four years, Mueller and her Digital Structures research group have been developing a strategy for “upcycling” those waste materials by using them in construction—not as cladding or finishes aimed at improving appearance but as structural components. “The greatest value you can give to a material is to give it a load-bearing role in a structure,” she says. But when builders use virgin materials, those structural components are the most emissions-intensive parts of buildings due to their large volume of high-strength materials. Using upcycled materials in place of those high-carbon systems is therefore especially impactful in reducing emissions.

Mueller and her team focus on tree forks, that is, spots where the trunk or branch of a tree divides in two, forming a Y-shaped piece. In architectural drawings, there are many similar Y-shaped nodes where straight elements come together. In such cases, those units must be strong enough to support critical loads.

“Tree forks are naturally engineered structural connections that work as cantilevers in trees, which means that they have the potential to transfer force very efficiently thanks to their internal fiber structure,” says Mueller. “If you take a tree fork and slice it down the middle, you see an unbelievable network of fibers that are intertwining to create these often three-dimensional load transfer points in a tree. We’re starting to do the same thing using 3D printing, but we’re nowhere near what nature does in terms of complex fiber orientation and geometry.”

She and her team have developed a five-step “design-to-fabrication workflow” that combines natural structures such as tree forks with the digital and computational tools now used in architectural design. While there’s long been a “craft” movement to use natural wood in railings and decorative features, the use of computational tools makes it possible to use wood in structural roles—without excessive cutting, which is costly and may compromise the natural geometry and internal grain structure of the wood.

Given the wide use of digital tools by today’s architects, Mueller believes that her approach is “at least potentially scalable and potentially achievable within our industrialized materials processing systems.” In addition, by combining tree forks with digital design tools, the novel approach can also support the trend among architects to explore new forms. “Many iconic buildings built in the past two decades have unexpected shapes,” says Mueller. “Tree branches have a very specific geometry that sometimes lends itself to an irregular or nonstandard architectural form—driven not by some arbitrary algorithm but by the material itself.”

Step 0: Find a source, set goals

Before starting their design-to-fabrication process, the researchers needed to locate a source of tree forks. Mueller found help in the Urban Forestry Division of the City of Somerville, Massachusetts, which maintains a digital inventory of more than 2,000 street trees—including more than 20 species—and records information about the location, approximate trunk diameter, and condition of each tree.

With permission from the forestry division, the team was on hand in 2018 when a large group of trees was cut down near the site of the new Somerville High School. Among the heavy equipment on site was a chipper, poised to turn all the waste wood into mulch. Instead, the workers obligingly put the waste wood into the researchers’ truck to be brought to MIT.

In their project, the MIT team sought not only to upcycle that waste material but also to use it to create a structure that would be valued by the public. “Where I live, the city has had to take down a lot of trees due to damage from an invasive species of beetle,” Mueller explains. “People get really upset—understandably. Trees are an important part of the urban fabric, providing shade and beauty.” She and her team hoped to reduce that animosity by “reinstalling the removed trees in the form of a new functional structure that would re-create the atmosphere and spatial experience previously provided by the felled trees.”

With their source and goals identified, the researchers were ready to demonstrate the five steps in their design-to-fabrication workflow for making spatial structures using an inventory of tree forks.

Step 1: Create a digital material library

The first task was to turn their collection of tree forks into a digital library. They began by cutting off excess material to produce isolated tree forks, some of which are shown in the photo above. They then created a 3D scan of each fork. Mueller notes that as a result of recent progress in photogrammetry (measuring objects using photographs) and 3D scanning, they could create high-resolution digital representations of the individual tree forks with relatively inexpensive equipment, even using apps that run on a typical smartphone.

In the digital library, each fork is represented by a “skeletonized” version showing three straight bars coming together at a point. The relative geometry and orientation of the branches are of particular interest because they determine the internal fiber orientation that gives the component its strength.

Step 2: Find the best match between the initial design and the material library

Like a tree, a typical architectural design is filled with Y-shaped nodes where three straight elements meet up to support a critical load. The goal was therefore to match the tree forks in the material library with the nodes in a sample architectural design.

First, the researchers developed a “mismatch metric” for quantifying how well the geometries of a particular tree fork aligned with a given design node. “We’re trying to line up the straight elements in the structure with where the branches originally were in the tree,” explains Mueller. “That gives us the optimal orientation for load transfer and maximizes use of the inherent strength of the wood fiber.” The poorer the alignment, the higher the mismatch metric.

The goal was to get the best overall distribution of all the tree forks among the nodes in the target design. Therefore, the researchers needed to try different fork-to-node distributions and, for each distribution, add up the individual fork-to-node mismatch errors to generate an overall, or global, matching score. The distribution with the best matching score would produce the most structurally efficient use of the total tree fork inventory.

Since performing that process manually would take far too long to be practical, they turned to the “Hungarian algorithm,” a technique developed in 1955 for solving such problems. “The brilliance of the algorithm is solving that [matching] problem very quickly,” Mueller says. She notes that it’s a very general-use algorithm. “It’s used for things like marriage match-making. It can be used any time you have two collections of things that you’re trying to find unique matches between. So, we definitely didn’t invent the algorithm, but we were the first to identify that it could be used for this problem.”

The figure above presents a sample structure design with three possible distributions of the tree forks in the researchers’ inventory. The forks colored green are well matched with their nodes; the strings in the design pass through the centerline of the fork. The red forks are less well matched. The top option includes many red forks, so it has lots of mismatches and a high global mismatch score. The bottom option achieves the most green forks and thus the lowest mismatch score of the three options.

Repeated tests showed that the matching score improved as the number of forks available in the material library increased—up to a point. In general, the researchers concluded that the mismatch score was lowest, thus best, when there were about three times as many forks in the material library as there were nodes in the target design.

Step 3: Balance designer intention with structural performance

The next step in the process was to incorporate the intention or preference of the designer. To permit that flexibility, each design includes a limited number of critical parameters, such as bar length and bending strain. Using those parameters, the designer can manually change the overall shape, or geometry, of the design or can use an algorithm that automatically changes, or “morphs,” the geometry. And every time the design geometry changes, the Hungarian algorithm recalculates the optimal fork-to-node matching.

“Because the Hungarian algorithm is extremely fast, all the morphing and the design updating can be really fluid,” notes Mueller. In addition, any change to a new geometry is followed by a structural analysis that checks the deflections, strain energy, and other performance measures of the structure. On occasion, the automatically generated design that yields the best matching score may deviate far from the designer’s initial intention. In such cases, an alternative solution can be found that satisfactorily balances the design intention with a low matching score.

Step 4: Automatically generate the machine code for fast cutting

When the structural geometry and distribution of tree forks have been finalized, it’s time to think about actually building the structure. To simplify assembly and maintenance, the researchers prepare the tree forks by recutting their end faces to better match adjoining straight timbers and cutting off any remaining bark to reduce susceptibility to rot and fire.

To guide that process, they developed a custom algorithm that automatically computes the cuts needed to make a given tree fork fit into its assigned node and to strip off the bark. The goal is to remove as little material as possible but also to avoid a complex, time-consuming machining process. “If we make too few cuts, we’ll cut off too much of the critical structural material. But we don’t want to make a million tiny cuts because it will take forever,” Mueller explains.

The photo above shows the setup they use to prepare their tree forks. The team uses facilities at the Autodesk Boston Technology Center Build Space, where the robots are far larger than any at MIT and the processing is all automated. To prepare each tree fork, they mount it on a robotic arm that pushes the joint through a traditional band saw in different orientations, guided by computer-generated instructions. The robot also mills all the holes for the structural connections. “That’s helpful because it ensures that everything is aligned the way you expect it to be,” says Mueller.

Step 5: Assemble the available forks and linear elements to build the structure

The final step is to assemble the structure. The tree-fork-based joints are all irregular, and combining them with the precut straight wooden elements could be difficult. However, they’re all labeled. “All the information for the geometry is embedded in the joint, so the assembly process is really low-tech,” says Mueller. “It’s like a child’s toy set. You just follow the instructions on the joints to put all the pieces together.”

The photograph above shows their final structure, which they installed temporarily on the MIT campus. Mueller notes that it was only a portion of the structure they plan to build. “It had 12 nodes that we designed and fabricated using our process,” she says, adding that the team’s work was “a little interrupted by the pandemic.” As activity on campus resumes, the researchers plan to finish designing and building the complete structure, which will include about 40 nodes and will be installed as an outdoor pavilion on the site of the felled trees in Somerville.

In addition, they will continue their research. Plans include working with larger material libraries, some with multi-branch forks, and replacing their 3D-scanning technique with computerized tomography scanning technologies that can automatically generate a detailed geometric representation of a tree fork, including its precise fiber orientation and density. And in a parallel project, they’ve been exploring using their process with other sources of materials, with one case study focusing on using material from a demolished wood-framed house to construct more than a dozen geodesic domes.

To Mueller, the work to date already provides new guidance for the architectural design process. With digital tools, it has become easy for architects to analyze the embodied carbon or future energy use of a design option. “Now we have a new metric of performance: How well am I using available resources?” she says. “With the Hungarian algorithm, we can compute that metric basically in real time, so we can work rapidly and creatively with that as another input to the design process.”

資料來源:

https://energy.mit.edu/news/using-natures-structures-in-wooden-buildings/