臺灣梅花鹿(Cervus nippon taiouanus)取食偏好及其對墾丁高位珊瑚礁森林更新之影響

Browsing preferences of Formosan Sika deer (Cervus nippon taiouanus) and its impact on the regeneration of Kenting Karst Forest

葉定宏(Yeh Ding-Hong)

指導教授 ： 洪國翔 ； 郭耀綸

國立屏東科技大學/農學院/生物資源研究所/博士(2023年)

https://doi.org/10.6346/NPUST202300005

摘要

野放的臺灣梅花鹿已對墾丁高位珊瑚礁森林的更新造成嚴重衝擊。本論文第一項研究之目的為暸解梅花鹿對墾丁高位珊瑚礁森林樹種葉片的取食偏好及稚樹遭梅花鹿磨角情形，探討鹿隻取食偏好與不同樹種稚樹族群變動率的關係。論文第二項研究先後設置面積890 m2及1.3 ha的兩處圍籬，阻隔梅花鹿啃食，在兩處也設置可供比對之無圍籬對照樣區，目的在於比較有、無梅花鹿啃食，對樹苗群落之物種豐度及樹苗更新動態的影響。在890 m2小圍籬內、外兩樣區也都栽植易遭梅花鹿危害的12種樹苗，評估該作業對樹苗族群量及物種多樣性的提升效果。
取食偏好試驗結果顯示，梅花鹿對受測77樹種葉片的啃食率具明顯差異，有9樹種全數葉片會被梅花鹿取食，適口性等級最高，例如山黃麻、稜果榕、血桐等。然而，有12樹種葉片完全不被梅花鹿取食，適口性等級最低，包括紅柴、樹杞、海州常山、厚殼樹、梧桐、白樹仔、石苓舅、大葉楠、臺灣山桂花、粗糠柴、臺灣梭羅樹及假酸漿。磨角痕跡調查結果發現樹幹磨損程度隨植株徑級加大而減輕，遭嚴重磨損植株的徑級以小於2 cm的幼齡稚樹居多。紅柴為梅花鹿喜歡磨角，毛柿則為避免磨角的樹種。梅花鹿對不同樹種具差異性的啃食率，與墾丁森林動態樣區2001～2013年間，26主要樹種的稚樹族群減少率有極顯著正相關，梅花鹿適口性越高的樹種，其稚樹族群減少率越大。此外，梅花鹿取食偏好較高的樹種，若其族群空間分布集中在隆起礁岩生育地，則其稚樹族群減少率較低，稚樹能躲避梅花鹿的取食傷害。
經兩年調查顯示890 m2小圍籬樣區內，植株高度≥ 10 cm的大苗、高度< 10 cm的中苗，以及新生苗的物種數與株數都提高，而對照樣區大苗及中苗該兩介量都下降，只有新生苗增加。對照樣區梅花鹿較偏好取食的大苗及中苗，數量減少的程度也都高於不好取食之樹種；相反的，三類取食偏好的苗木在圍籬樣區的數量都增加。圍籬樣區大苗的香農-威納及辛普森兩物種多樣性指數持續提高，但在對照樣區則下降。此外，物種數、株數及物種多樣性等三項介量，在1.3 ha大圍籬內、外樣區的變化趨勢與小圍籬樣區一致。本研究發現梅花鹿對樹苗群落的啃食壓力已下達植株高度< 10 cm的苗木。另一方面，人為栽植的12種樹苗在小圍籬外之對照樣區於短期內即遭嚴重啃食，栽植後2年期間只存活2種3株，而圍籬內仍存活11種120株，令圍籬樣區大苗群落的香農-威納多樣性指數由2.51提升為2.90。
本研究結論為梅花鹿取食行為有明顯的樹種偏好，設置圍籬阻絕梅花鹿，可提高樹苗群落的物種豐度並維持其更新，若無圍籬保護則梅花鹿較偏好取食之樹種的苗木難以更新建立。兩年調查期間小圍籬樣區之三類形體苗木整體的豐量已增為3.4倍，顯示樹苗群落恢復速度快。

關鍵字

取食偏好 ； 圍籬樣區 ； 天然更新 ； 樹苗群落 ； 物種多樣性指數

並列摘要

The reintroduced Formosan Sika deer has caused severe impacts to the regeneration of forest vegetation in the Kenting Karst Forest. In the first part of this study, browsing preferences of deer of leafbearing twigs were tested, and saplings of various species were surveyed for fraying scars caused by deer to investigate the relationship between browsing preferences and rates of change of juvenile populations of different tree species. In the second part of this study, the impacts of deer herbivory were studied by comparing the dynamics in species richness and natural regeneration of seedling communities in exclosure plots vs. unfenced control plots from exclosures of 890 m2 and 1.3 ha respectively. We also planted seedlings of 12 tree species prone to deer damage in 890 m2 exclosure treatment to evaluate the improvement of the seedling abundance and community diversity.
Results showed that, browsing rates significantly differed among 77 tested tree species. Twigs of 9 species were entirely browsed, including Trema orientalis, Ficus septica, Macaranga tanarius, etc., indicating that these species were the most palatable to deer. On the other hand, twigs of 12 species were not browsed at all, including Aglaia formosana, Ardisia sieboldii, Clerodendrum trichotomum, Ehretia acuminata, Firmiana simplex, Gelonium aequoreum, Glycosmis citrifolia, Machilus japonica var. kusanoi, Maesa perlaria var. formosana, Mallotus philippensis, Reevesia formosana, and Trichodesma calycosum, and thus were the least palatable. Surveys of fraying scars showed that damage to trees was alleviated as the diameter of the saplings increased, and the most severe fraying damage occurred in saplings with a diameter of ≤ 2 cm. The deer preferred saplings of Aglaia formosana and avoided saplings of Diospyros blancoi for their fraying behavior. The browsing rates of 26 tree species had significant positive correlations with rates of decline of juvenile populations between 2001 and 2013 in the Kenting Karst Forest Dynamic Plot. Results showed that the higher the palatability level of a tree species, the higher the rate of decline of its juvenile population. Declining rates of juvenile populations of species with higher palatability rates were lower if the population was primarily growing on exposed limestone habitats, which prevented browsing damage by deer.
During the 2-year investigation period of 890 m2 exclosure treatment, the species richness and abundance of large-sized (height ≥ 10 cm), middle-sized (height < 10 cm), and emerging seedlings in the exclosure plot all increased. On the other hand, large- and middle-sized seedlings in the control plot decreased, with only emerging seedlings increasing. In the control plot, the abundance of large- and middle-sized seedlings that were highly preferred by Formosan Sika deer were more greatly reduced compared to lower-preference seedlings. However, in the exclosure plot, amounts of higher-preference seedlings of all size classes increased. Values of the Shannon-Wiener index (H’) and Simpson’s index of species diversity of large-sized seedlings increased in the exclosure plot, but both indices decreased in the control plot. The changing pattern of species richness, abundance and H’ of 1.3 ha exclosure treatments were all similar to the 890 m2 exclosure treatment. This study found that the browsing pressure of Formosan Sika deer on seedling communities had lowered to individuals of < 10 cm in height. In addition, planted seedlings in the control plot were severely browsed within a short time, and only 2 species had 3 seedlings survive. While in the exclosure plot, 120 seedlings of 11 species survived. Therefore, the value of H’ of large-sized seedlings increased from 2.51 to 2.90 in the exclosure plot.
In conclusion, exclosure treatment increased the species richness of the seedling community and promoted natural recruits. Natural regeneration of tree species that are highly preferred by Formosan Sika deer will be hampered if there are no fences for protection. Abundances of these 3 sizes of seedlings had increased 3.4-times 2 years after establishing the 890 m2 exclosure plot. It showed that the recovery rate of the seedling community was relatively fast.

並列關鍵字

browsing preference ； exclosure plot ； natural regeneration ； seedling community ； species diversity index

參考文獻

郭耀綸、尤國霖、楊月玲、王相華 (2007) 颱風擾動對台灣南部墾丁森林林下光量及六種樹苗生長的影響。台灣林業科學 22(4): 367-380。

王相華、王玉婷、伍淑惠、蘇聲欣 (2019) 台灣梅花鹿磨角行為對墾丁高位珊瑚礁森林樹木的危害。台灣林業科學 34 (3): 207-215。

王相華、伍淑惠、孫義方、陳可芳 (2015) 墾丁高位珊瑚礁森林之幼齡稚樹在2001至2013年間急遽減少。國家公園學報 25(1): 17-23。

王相華、郭耀綸 (1995) 墾丁高位珊瑚礁原始林林下茄苳新生幼苗之族群動態。林業試驗所研究報告季刊 10(4): 383-389。

王相華、郭耀綸、潘順勇 (1997) 墾丁高位珊瑚礁森林樹冠疏開對二十種樹木種子發芽的影響。台灣林業科學 12 (3): 299-307。