HKWildlife.Net Forum 香港自然生態論壇
遊客:  註冊 | 登錄 | 龍尾 | YouTube | Facebook | English | Library | Blog | 幫助
 
fai1888
蟲卵
Rank: 1



UID 6821
Total 50
主題
回覆
精華 0
積分 86
種子 86
花蜜 50
閱讀權限 20
註冊 2017-2-20
Pri. Camera: 
狀態 離線
發表於 2017-5-5 23:25  資料 短消息 


QUOTE:
原帖由 mathew 於 2017-5-5 16:06 發表

一直討論原始植被, 原生動物.
請問如何定下界線?
i. 以地厘分布尚有間斷分布的難題;
ii. 若論從前(時間)有某物種, 應以那一標準決定? 討論間有提及宋朝, 1842年前/後, WWII, 何時存活於此地謂原生?

好問題,呢個好深,我自己都有咁唸過,無答案
更正一下,我覺得都起碼WWII前~~

[ 本帖最後由 fai1888 於 2017-5-8 18:01 編輯 ]
頂部
Aland
幼蟲
Rank: 2Rank: 2



UID 6332
Total 359
主題
回覆
精華 0
積分 5062
種子 5062
花蜜 356
閱讀權限 60
註冊 2015-1-28
Pri. Camera: 
狀態 離線
發表於 2017-5-9 09:59  資料 文集 短消息 


QUOTE:
原帖由 fai1888 於 2017-5-5 09:56 發表


假設大嶼山的物種的確比其他香地方少很多,我們多種原生植物後,say 20年後,再加上多一些rodents,如松鼠;理論上松鼠應該再不需要靠人類食物,因爲國外松鼠在殼斗科植物的確有很多文獻support.
  以香港氣候,應該多d evergree ...

我自己覺得大嶼山就算物種較少,殼斗科/茶科植物的比例其實不比新界低
尤其鳳凰山,基本上到某個高度之後殼斗科/茶科是優勢種
應該不需要靠刻意種植殼斗科植物維持新引入傳種者population

至於殼斗科在港島是否被松鼠有效傳播,我覺得難以單憑感覺下定論

你提到外國研究,確實,絕大部分殼斗科植物都靠scatter-hoarding animals傳播種子
但實際上scatter-hoarding animals亦紛陳多樣,很多地區其實靠雀鳥
要應用在香港身上,還需鄰近地區scatter-hoarding animals的資料
可惜華南地區deforestation嚴重,能保留原貌的地區不多,而研究亦相當缺乏
做一個簡單Google search,最近都要去到秦嶺:
https://www.researchgate.net/publication/257671850_Seed_dispersal_of_three_sympatric_oak_species_by_forest_rodents_in_the_Qinling_Mountains_Central_China

而要留意的是,松鼠絕對並非唯一一種scatter-hoarding mammals, 很多大型鼠類其實亦非常重要
有興趣可以參考http://onlinelibrary.wiley.com/doi/10.1111/1365-2745.12113/abstract
篇文有講油茶用小泡巨鼠傳種,亦有提到不同鼠類可以是seed disperser亦可是seed predator

最後更正一點
二戰前香港其實已經光禿一片
斬薪柴活動,在香港仍是農業主導時已經清除大部分原生樹林
二戰清除的,主要是後來政府所種植的植林
我上文用二戰做分界點,主要是因為二戰是香港最後一次大型deforestation,而非因為戰前香港森林好好景

[ 本帖最後由 Aland 於 2017-5-9 12:12 編輯 ]
頂部
Aland
幼蟲
Rank: 2Rank: 2



UID 6332
Total 359
主題
回覆
精華 0
積分 5062
種子 5062
花蜜 356
閱讀權限 60
註冊 2015-1-28
Pri. Camera: 
狀態 離線
發表於 2017-5-9 12:05  資料 文集 短消息 


QUOTE:
原帖由 mathew 於 2017-5-5 16:06 發表
其實我深受Jurassic Park的概念影響
重新引入herbivore, 大自然會怎樣調整population?
1. 缺乏食物?
會否在飢餓前過度採食 / 人類餵飼令population高於自然承載量 / ...
2. 由carnivore捕食?
現存野外的carnivore能否勝任 / 引入carnivore / ...
3. ......

有趣的問題......

我自己深信,任何物種都有carrying capacity,就算無明顯predator,population都不會無限增長
上面提到的野豬是一例
野豬在香港基本上無predator,但雖然現時數目可能已經超越以往有華南虎、有豹時的水平,對本地植披仍未至於產生嚴重影響
亦不會引致豬「豬」羅紀公園

事實上超越carrying capacity,乃常有之事
一個正常的動物群族,只要growth rate未算太低,population size都會oscillate and cyclically, or chaotically, go over the carrying capacity
可參考:http://openlandscapes.zalf.de/OpenLandscapesWiki_Glossaries/Aspects%20of%20Ecosystem%20Dynamics.aspx

當然,引入物種帶來生態災難歷史上例子不少(棕樹蛇、紅火蟻)
但一般認為主因是因為外來物種完全無天敵牽制,而parasitic load極低所致
引入毗鄰地區的物種引起生態災難已經鮮有聽聞,重新引入物種就更加少聽會造成負面影響

反觀上面提到的小泡巨鼠、松鼠
很難想象這類果食性的scatter-hoarding species可以引來什麼生態災難
尤其本地predator,例如豹貓、猛禽應該可以取食這些體型不大的rodents?
又,若果仍然擔心這些rodents會造成生態災難,可以先隔離一個patch做實驗,例如用外島(有先例,印象中丫洲就曾經用作測試菟絲子控制薇甘菊)

講真,我認同引入物種有風險
但當一個keystone species對維持一個地區的植披結構,生態系統有深遠影響
而不引入長遠而言會引致三四十種植物,連帶賴以生存的真菌、昆蟲一併消失的時候
我覺得至少要考慮承受有關風險落手去做

QUOTE:
一直討論原始植被, 原生動物.
請問如何定下界線?
i. 以地厘分布尚有間斷分布的難題;
ii. 若論從前(時間)有某物種, 應以那一標準決定? 討論間有提及宋朝, 1842年前/後, WWII, 何時存活於此地謂原生?

個人觀感(上次都有提到):
若一個物種透過自然傳播過程來到香港,該物種應該被視為原生

不過定義歸定義,要確認香港物種當中那些是原生種,幾乎不可能
而這個definition亦有灰色地帶
例如不少農地物種可能是透過天然過程來到香港,但物種在香港能夠立足,全賴人類開墾農地
這情況下又算不算原生?

而最後,將所有物種歸類為原生、非原生,有意義嗎?

[ 本帖最後由 Aland 於 2017-5-9 12:14 編輯 ]
頂部
mathew
成蟲
Rank: 4Rank: 4Rank: 4Rank: 4


UID 370
Total 2284
主題
回覆
精華 0
積分 17906
種子 17906
花蜜 2270
閱讀權限 60
註冊 2006-11-17
Pri. Camera:  Nikon
來自 鏡花緣
狀態 離線
發表於 2017-5-10 09:54  資料 主頁 文集 短消息 
回覆 #43 Aland 的帖子



QUOTE:
......

當然,引入物種帶來生態災難歷史上例子不少(棕樹蛇、紅火蟻)
但一般認為主因是因為外來物種完全無天敵牽制,而parasitic load極低所致
引入毗鄰地區的物種引起生態災難已經鮮有聽聞,重新引入物種就更加少聽會造成負面影響

反觀上面提到的小泡巨鼠、松鼠
很難想象這類果食性的scatter-hoarding species可以引來什麼生態災難
尤其本地predator,例如豹貓、猛禽應該可以取食這些體型不大的rodents?
又,若果仍然擔心這些rodents會造成生態災難,可以先隔離一個patch做實驗,例如用外島(有先例,印象中丫洲就曾經用作測試菟絲子控制薇甘菊)

講真,我認同引入物種有風險
但當一個keystone species對維持一個地區的植披結構,生態系統有深遠影響
而不引入長遠而言會引致三四十種植物,連帶賴以生存的真菌、昆蟲一併消失的時候
我覺得至少要考慮承受有關風險落手去做

好奇一問, 可否分享一些 "引入毗鄰地區/重新引入 物種" 的例子, 謝謝.

無論是想像/理論/實驗, 都只是推測, 目前我們有足夠的智識/智慧去作出這決定嗎?
在認知不足時, 我會偏向保守的反應/決定.

始終人類不是管理大自然, 而只是大自然的一部分, 應盡力與大自然共存.

QUOTE:
......

而最後,將所有物種歸類為原生、非原生,有意義嗎?

這要視乎在那一角度討論. 這討論最初正正在說赤腹松鼠為引入種, 沒有原生何來引入.

很務實的說, 若外來物種能找到其niche, 與其他物種有合理互動, 有何可議?
只是在主動引入的時候, 無論出發點為何, 應該萬分謹慎.




Olympus C750, Canon SX200IS, Sony QX10
Nikon D70s/D7000, AF Micro 60mm f/2.8D, AF 35mm f/2, AF 70-300mm f/4-5.6D, AFS 300mm f4, Kenko Extension Tube
討論野生植物為主
頂部
jasonpoon
蟲蛹
Rank: 3Rank: 3Rank: 3


UID 869
Total 1340
主題
回覆
精華 0
積分 2948
種子 2948
花蜜 1209
閱讀權限 50
註冊 2007-3-29
Pri. Camera:  Olympus
來自 HK
狀態 在線
發表於 2017-5-10 15:46  資料 短消息 


QUOTE:
原帖由 mathew 於 2017-5-10 09:54 AM 發表
好奇一問, 可否分享一些 "引入毗鄰地區/重新引入 物種" 的例子, 謝謝.

無論是想像/理論/實驗, 都只是推測, 目前我們有足夠的智識/智慧去作出這決定嗎?
在認知不足時, 我會偏向保守的反應/決定.

始終人 ...

Gambusia affinis (食蚊魚), the mosquito fish originally inhabiting Central America/Mexico was introducted to control mosqitoes in HK and many parts of the world after WWII. As for HK, this should be a long-range but not adjacent region introduction. It was quite well established once in the 1950's - 80's (personal hearsay & observation). It has since become rare perhaps following the decline of local farming activities. They frequent the field-side ditches, water pools for irrigation, etc. Cessation of farming has reduced the water quantity and quality in the ditches and possible overgrowth of weeds & water plants rendered their habitat less suitable for their existence. Increasing spraying of mosquito oil by the govt and pollution may also suffocated a lot of them. Being adapted to more stagnant water, they may not be able to establish themselves in fast flowing cleaner streams in HK. Competitive decline due to local mid-water species may also contribute.

Tilapia (or Oreochromis) mossambicus/niloticus/zillii species group & hybrids (金山鯽, 羅非魚, 福壽魚) was probably introduced into HK as early as in the 1940's, possibly from Indonesia or Africa directly. Until today, they are widely established in local reservoirs, muddy or sandy rivers, brackish waters and mangroves. Hybrids in culture and in the wild are highly possible contributing to increased adaptability especially to cold winter temperature. Massive deaths in winter due to cold front were seen as late as in 70's and 80's but fewer later on possible due to adaptation and global warming. They are omnivorous and probably preyed on bottom dwelling original fishes and invertebrates.

Xiphophorus helleri & spp. (青劍, 紅劍, 月魚, 鴛鴦) & Poecilia spp. (孔雀, 摩利) have been found in local streams increasingly probably from 1990's likely due to release from aquarium hobbyists. They are confirmed to have established breeding populations in reservoir catchments and local streams and ditches such as Tung Chung River. Being mid water fast moving omnivores originating around Middle  & South America, they may compete with common local species such as Barbodes semifasciolatus and Parazacco spilurus. However, lowland streams in HK are already fully and extensively human disturbed in many other aspects. The decline or disappearance of Barbodes semifasciolatus, Pseudoastromyzon sp. locally may be a result of their introduction and competition.

Various larger introduced aquarium fishes maybe fished or caught in reservoirs or catchments. I personally have known Chitala ornata (東洋刀) (Thailand & SE Asia), Pseudoplatystoma fasciatum (鴨嘴鯰) (S. America), Loricaria spp. (琵琶) (S. America). Some species of Channa (生魚, 鱧) may not be natural to HK.

Even one onshore seawater species is definitely introduced, the Red Drum (星鱸) (Sciaenops ocellatus) was originated from N. American East Coast and is a worldwide seawater aquaculture species.

本帖最近評分記錄
mathew   2017-5-10 16:19  種子  +10   內容充實, 其實想知'成功'例子. ...
頂部
jasonpoon
蟲蛹
Rank: 3Rank: 3Rank: 3


UID 869
Total 1340
主題
回覆
精華 0
積分 2948
種子 2948
花蜜 1209
閱讀權限 50
註冊 2007-3-29
Pri. Camera:  Olympus
來自 HK
狀態 在線
發表於 2017-5-10 17:55  資料 短消息 
以上其實只有食蚊魚係當局有心引入到野外的, 可能最初係想佢地係D靜水池塘繁育控制孑孓. 可惜那些水體有其他污染搞到魚兒都頂唔順

其他都唔算係有計劃的引入到野外...
頂部
jasonpoon
蟲蛹
Rank: 3Rank: 3Rank: 3


UID 869
Total 1340
主題
回覆
精華 0
積分 2948
種子 2948
花蜜 1209
閱讀權限 50
註冊 2007-3-29
Pri. Camera:  Olympus
來自 HK
狀態 在線
發表於 2017-5-11 05:07  資料 短消息 
經典的國際例子, 可參考:

1. 中國長江下游的四不像 (麋鹿) Elaphurus davidianus
https://zh.wikipedia.org/wiki/%E9%BA%8B%E9%B9%BF

2. 美國黃石國家公園的狼 Canis lupus
https://en.wikipedia.org/wiki/Hi ... lowstone#Subspecies

本帖最近評分記錄
Aland   2017-5-13 14:42  種子  +10   Nice examples
頂部
Aland
幼蟲
Rank: 2Rank: 2



UID 6332
Total 359
主題
回覆
精華 0
積分 5062
種子 5062
花蜜 356
閱讀權限 60
註冊 2015-1-28
Pri. Camera: 
狀態 離線
發表於 2017-5-13 14:40  資料 文集 短消息 


QUOTE:
原帖由 mathew 於 2017-5-10 09:54 發表
好奇一問, 可否分享一些 "引入毗鄰地區/重新引入 物種" 的例子, 謝謝.

無論是想像/理論/實驗, 都只是推測, 目前我們有足夠的智識/智慧去作出這決定嗎?
在認知不足時, 我會偏向保守的反應/決定.

始終人類不是管理大自然, 而只是大自然的一部分, 應盡力與大自然共存.

這要視乎在那一角度討論. 這討論最初正正在說赤腹松鼠為引入種, 沒有原生何來引入.

很務實的說, 若外來物種能找到其niche, 與其他物種有合理互動, 有何可議?
只是在主動引入的時候, 無論出發點為何, 應該萬分謹慎.

關於重新引入曾經出現過的keystone species,或其ecological equivalent,可以參考wikipedia "rewilding" 一頁
https://en.wikipedia.org/wiki/Rewilding_(conservation_biology)

實際上,此概念近幾年在歐美各國相當流行,有牛有鹿有熊有狼有馬,非常多樣化
其中一個經典例子為Oostvaardersplassen,當地政府非常大規模地重新引入物種,minimize management,以嘗試恢復昔日光景,並取得一定成果
http://www.wildeurope.org/index.php/restoration/national-strategies/rewilding-holland

當然過程中確實會引起爭議,尤其重新引入top predator
例如在Scotland重新引入消失了350年的狼,就在英國國內引起不少討論
(可參考:http://www.bbc.co.uk/news/magazine-33017511

反觀香港
我個人認為,可以與大自然共存當然最理想
但過去幾百年來人類對本地生態的干預太徹底,以不造成額外影響為由去抗拒active management/rewilding已經未必適切
上面有提到,香港的樹林很可能有非常龐大的extinction debt
以往deforestation/megafaunal extinctions所造成的影響,可能較想象中龐大,只是未曾完全彰顯出來而已
要去減少過去人類對本地系統所造成的破壞,需要active management
而重新引入一些小型的scatter-hoarding rodents,其實已經是風險較低,成本效益較高的選項

至於原生和引入種的問題
同意出發點其實是引入種究竟有否與環境產生合理互動(值得再討論的是,何謂“合理互動”?)
我相信無人會否定薇甘菊/福壽螺等物種,對本地生態平衡造成負面影響
但像蒲桃這類似乎相當融入本地生境的引入種,在保育過程中如何定位?
再極端少少,如上面所述,本地不少農地物種,例如各種蓼,其實有可能本質是若干年前的外來種
如是者,又是否值得再去尋根究底,一一分類?
頂部
Aland
幼蟲
Rank: 2Rank: 2



UID 6332
Total 359
主題
回覆
精華 0
積分 5062
種子 5062
花蜜 356
閱讀權限 60
註冊 2015-1-28
Pri. Camera: 
狀態 離線
發表於 2017-5-13 15:18  資料 文集 短消息 


QUOTE:
原帖由 jasonpoon 於 2017-5-5 15:27 發表
Can we argue in reverse? C. camphora was indeed very abundant in original lowland forest of HK and indeed S. China. the idea of re-cultivating trees for timber should be rare among early farmers in HK. why they do not plant in open deforested area but instead in their revered Fung Shui woods?

That is not impossible. If that is indeed the case, the question we should be asking ourselves is why is C. camphora so scarce in secondary lowland forests? Why is the regenerative ability of the species so low nowadays? Is it facing the same problem Fagaceae is facing currently, or is the regenerative ability affected by other factors such as pests and diseases? (galls on fruits of Cinnamomum spp. affecting fruit formation maybe?)

Returning to my hypothesis of camphor trees being deliberately planted in Fung Shui woods, I could see reasons why villagers might prefer planting camphor trees in Fung Shui woods of all places. To start with, Fung Shui woods are easily accessible. It is not preferable if a 樟木櫳 sized piece of timber has to be transported from far away back to the village. Also, if we refer back to the photos taken in that era, the hillslopes in large parts of Hong Kong are bare and deforested. These slopes are likely to be depleted of nutrients and very exposed to wind. Not suitable for plantation in a small scale. As you said, the demand for 樟木櫳 isn't that large. It is simply not worth it to create a whole plantation of camphor trees. Planting a few trees near the village might be more sensible for the villagers.

I think asking some old villagers might yield some answers.

QUOTE:
alas, while the floral composition maybe there, the too small size of the forest could not sustain the megafauna which disappeared dispite the final hiding places. if any sessile species may survive and breed in those Fung Shui woods separately, those woods may act as isolating islands and undergone genetic drift and possible speciation... look for evidence in wingless insects and worms maybe...

I agree that Fung Shui woods are unlikely to sustain large animals, but I think at least some insects should persist. While many birds, butterflies, and mammals disappeared, I vaguely remember that Hong Kong has a surprisingly high diversity of ant species. Likely a relic of the high diversity subtropical rainforests we once had.

To be honest, I don't think genetic drift and natural selection would be sufficient to result in speciation events among different Fung Shui woods. You need quite almost complete reproductive isolation to prevent the swamping effect as a result of gene flow. Personally, I believe that populations between different Fung Shui woods would definitely be less reproductively isolated than populations on small islands. Maybe we should start with finding new sessile species in Ninepin group?


Actually, I would quite like to know when did Fung Shui woods start to become isolated patches of forests? Or more generally, when did large scale deforestation in Hong Kong occur? According to Flora of Hong Kong (I think it's volume 2?), even the earliest travelers from Britain described Hong Kong as a bare island with no forest cover. So the deforestation must have occurred before that. Do we ever get records from 明清 about vegetative cover in Hong Kong?
頂部
jasonpoon
蟲蛹
Rank: 3Rank: 3Rank: 3


UID 869
Total 1340
主題
回覆
精華 0
積分 2948
種子 2948
花蜜 1209
閱讀權限 50
註冊 2007-3-29
Pri. Camera:  Olympus
來自 HK
狀態 在線
發表於 2017-5-14 16:19  資料 短消息 


QUOTE:
原帖由 Aland 於 2017-5-13 03:18 PM 發表

That is not impossible. If that is indeed the case, the question we should be asking ourselves is why is C. camphora  so scarce in secondary lowland forests? Why is the regenerative ability of the sp ...

Just another recent reading indicated that the planting of Aquilaria sinensis (土沉香) for incense (線香) making in HK (indeed the NT) was once a major economic produce that may even account for the name of 香港. That trade is likely to date back to around the Song Dynasty as ship sailing has to be advanced enough for sea trade.

A. sinensis could well be a key lowland tree species in "original" HK and indeed S. China lowland forests as it is endemic to S. China. If this craft of incense making is widespread once in NT villages, and if the logic of near Fung Shui wood cultivation is true, then we would expect remnants of old planted A. sinensis around Fung Shui woods. Is it the case?

As A. sinensis trees have been hunted badly, could a widespread plantation of this species (if botanically feasible) be done in HK?

[ 本帖最後由 jasonpoon 於 2017-5-14 19:01 編輯 ]
頂部
jasonpoon
蟲蛹
Rank: 3Rank: 3Rank: 3


UID 869
Total 1340
主題
回覆
精華 0
積分 2948
種子 2948
花蜜 1209
閱讀權限 50
註冊 2007-3-29
Pri. Camera:  Olympus
來自 HK
狀態 在線
發表於 2017-5-15 22:33  資料 短消息 
QUOTE
"I agree that Fung Shui woods are unlikely to sustain large animals, but I think at least some insects should persist. While many birds, butterflies, and mammals disappeared, I vaguely remember that Hong Kong has a surprisingly high diversity of ant species. Likely a relic of the high diversity subtropical rainforests we once had.

To be honest, I don't think genetic drift and natural selection would be sufficient to result in speciation events among different Fung Shui woods. You need quite almost complete reproductive isolation to prevent the swamping effect as a result of gene flow. Personally, I believe that populations between different Fung Shui woods would definitely be less reproductively isolated than populations on small islands. Maybe we should start with finding new sessile species in Ninepin group?

Actually, I would quite like to know when did Fung Shui woods start to become isolated patches of forests? Or more generally, when did large scale deforestation in Hong Kong occur? According to Flora of Hong Kong (I think it's volume 2?), even the earliest travelers from Britain described Hong Kong as a bare island with no forest cover. So the deforestation must have occurred before that. Do we ever get records from 明清 about vegetative cover in Hong Kong?"
END QUOTE


I once thought about the effect of typhoon in S. China on dispersal and genetic remixing of species especially for freshwater fishes which are easily isolated especially in hillstreams. Isolating mechanisms maybe alleviated by the frequent blown out individuals of small sizes.

Sources reported that early British colonists described HK as a "barren rock". However, I think this might be an overstatement as I doubt any Englishman had actually walked or charted the inland of NT. Systematic surveying of lands in NT only begin after the 1898 Convention and was done mainly by indian surveyors. There were history of early resistances from villagers silenced only by cannon blows from British warships. Throughout early to mid 20th century, urbanization happened mainly in HK Island and Kowloon areas. It is also a matter of question about the extend of deforestation during WWII. Major influx of people from China occurred in around 1949 and 1967. While the country parks were started around 1977.
頂部
mathew
成蟲
Rank: 4Rank: 4Rank: 4Rank: 4


UID 370
Total 2284
主題
回覆
精華 0
積分 17906
種子 17906
花蜜 2270
閱讀權限 60
註冊 2006-11-17
Pri. Camera:  Nikon
來自 鏡花緣
狀態 離線
發表於 2017-5-16 19:56  資料 主頁 文集 短消息 
回覆 #50 jasonpoon 的帖子



QUOTE:
Just another recent reading...

這類土沉香的文章, 要小心閱讀.
要好好判斷所考證的歷史資料可信性.




Olympus C750, Canon SX200IS, Sony QX10
Nikon D70s/D7000, AF Micro 60mm f/2.8D, AF 35mm f/2, AF 70-300mm f/4-5.6D, AFS 300mm f4, Kenko Extension Tube
討論野生植物為主
頂部
jasonpoon
蟲蛹
Rank: 3Rank: 3Rank: 3


UID 869
Total 1340
主題
回覆
精華 0
積分 2948
種子 2948
花蜜 1209
閱讀權限 50
註冊 2007-3-29
Pri. Camera:  Olympus
來自 HK
狀態 在線
發表於 2017-5-16 22:10  資料 短消息 


QUOTE:
原帖由 mathew 於 2017-5-16 07:56 PM 發表

這類土沉香的文章, 要小心閱讀.
要好好判斷所考證的歷史資料可信性.

Thanks indeed mathew. Everyone should exercise rationality and objectivity in science or life. Do you know of any evidence or report that indicate another story? Given the fact that controlling poaching is nearly impossible in the long run, the fate of the few surviving A. sinensis in the wild seems doomed.

In case it is possible to cultivate or investigate possible methods of propagation of the species in for eg. government nurseries, then this would be a concrete first step for preservation of the species.

The ecology of Aquilaria spp. in SE Asia points out that these species like to grow around mangroves or wetlands. Perhaps the lost of wetlands have contributed to their decline and rareness. It seems sadly that A. sinensis is more suitable for use as chinese herb or incense probably due to its higher sap content.

[ 本帖最後由 jasonpoon 於 2017-5-16 22:11 編輯 ]
頂部
Aland
幼蟲
Rank: 2Rank: 2



UID 6332
Total 359
主題
回覆
精華 0
積分 5062
種子 5062
花蜜 356
閱讀權限 60
註冊 2015-1-28
Pri. Camera: 
狀態 離線
發表於 2017-5-19 07:29  資料 文集 短消息 


QUOTE:
原帖由 jasonpoon 於 2017-5-14 16:19 發表



Just another recent reading indicated that the planting of Aquilaria sinensis (土沉香) for incense (線香) making in HK (indeed the NT) was once a major economic produce that may even account for th ...

Indeed Aquilaria sinensis is quite common in lowland forests and Feng Shui Woods. However, I have also read that most of the original plantations were destroyed with incense unsustainably exploited by villagers during 遷界令 in the Qing Dynasty, when almost all villages in Hong Kong were deserted. If this is true, then I suppose what we see nowadays is the progeny of the very few remaining trees after the 遷界令.

Also, unlike camphor trees, A. sinensis seems to be regenerating pretty successfully in lowland forests. Treelets of incense trees are pretty common despite being targeted by illegal poachers. This could be attributed to two factors: its shade tolerance, mentioned above; and the fact that its dispersal agent, large wasps such as 印度側異腹胡蜂 (Parapolybia indica indica), are still abundant and effective in dispersing the seeds. Therefore, I think it is unlikely that incense trees would be completely wiped out under poaching, which only targets large to medium trees. However, poaching is definitely causing a large drop in the population size of incense trees, and I agree that actively planting trees could be a way out in this case.

For your reference, I have witnessed wasps trying to remove the seeds of incense trees (see #63): http://www.hkwildlife.net/Forum/redirect.php?tid=5953&goto=lastpost#lastpost
The research paper in #63 looked into how chemical cues produced by the incense tree tricks the wasp into believing that the seed is an insect.
頂部
Aland
幼蟲
Rank: 2Rank: 2



UID 6332
Total 359
主題
回覆
精華 0
積分 5062
種子 5062
花蜜 356
閱讀權限 60
註冊 2015-1-28
Pri. Camera: 
狀態 離線
發表於 2017-5-19 09:13  資料 文集 短消息 


QUOTE:
原帖由 jasonpoon 於 2017-5-15 22:33 發表
I once thought about the effect of typhoon in S. China on dispersal and genetic remixing of species especially for freshwater fishes which are easily isolated especially in hillstreams. Isolating mechanisms maybe alleviated by the frequent blown out individuals of small sizes.

Typhoons might be important in genetic remixing. However, I suppose that is more relevant to insects, plants, and birds? It is hard to imagine fish being blown off from one stream to another. I actually think that freshwater fish, especially primary freshwater fish that never leaves the river basin it is in, are quite genetically isolated. There has been quite a lot of examples of impressive adaptive radiation and the evolution into different morphs in some freshwater fish taxa. Examples include the three-spine sticklebacks in North America showing high regional variation, guppies in Trinadad with different morphs below and above the waterfalls, and the amazing cichlids in Lake Victory and Lake Malawi. Even if there is gene mixing between populations, I believe birds carrying fish around and human activity might actually be a more plausible explanation? I wonder if anyone looked into the Fst values of primary freshwater fish in Hong Kong?

QUOTE:
Sources reported that early British colonists described HK as a "barren rock". However, I think this might be an overstatement as I doubt any Englishman had actually walked or charted the inland of NT. Systematic surveying of lands in NT only begin after the 1898 Convention and was done mainly by indian surveyors. There were history of early resistances from villagers silenced only by cannon blows from British warships. Throughout early to mid 20th century, urbanization happened mainly in HK Island and Kowloon areas. It is also a matter of question about the extend of deforestation during WWII. Major influx of people from China occurred in around 1949 and 1967. While the country parks were started around 1977.

http://twpcentre.weshare.hk/oceandeep3000/articles/756909

Photos of new territories from 1950 clearly shows hillslopes in New Territories are quite bare with only short vegetation, and the slopes that are actually forested are mainly covered with sparse pine trees. Clearly not the broadleaved subtropical rainforest one would expect in the absence of heavy human disturbance. At that time, the economy of New Territories was still heavily agricultural, and the deforestation is probably caused by villagers going uphill to collect fuelwood or directly using the slopes for 梯田 as some of the photos show. In fact agricultural activity in the New Territories could be dated back to settlements in Ho Chung Valley 4000 years ago. Evidence suggested that people in the Late Neolithic Period already started planting rice in the valley. Hence, vegetative change by agriculture in New Territories must have occurred very very long time ago. The main question is, how severe was it? When did most of our forests disappear?

I found a very detailed government account of changes in landscape in Hong Kong that may give us some answers:
http://www.pland.gov.hk/pland_en/p_study/prog_s/landscape/tech_report/ch5.htm

The basic idea is that, settlements from Neolithic period till 遷界令 in Qing Dynasty were only focused in flood plains and coastal areas. Agriculture, salt industry, and lime industry came into play in different times during this period. These industries, especially the lime industry, needs quite a lot of fuel wood from hillslopes. The resulting deforestation was gradual but substantial, with pollen data showing the dominance of grasses and the decline of pine trees/Fagaceae after the settlements are established. (The fact that other large tree families such as Lauraceae 樟科 is not represented in pollen data does not indicate that pine forests are dominant. It is probably because these families are insect pollinated and leave only a faint pollen record). The end of the 遷界令 in 1669 seems to be a very important point in the vegetative history in Hong Kong. In addition to the return of the people who left Hong Kong during the 遷界令, Hakka people moved into Hong Kong and created new settlements. Hakka people converted slopes to 梯田 and occupied even hilly areas.

Based on the information provided, I speculate that megafauna such as elephants and rhinos probably went locally extinct one by one since the Neolithic period. Gradual deforestation to provide fuel wood for salt and lime industries wiped out large animals dependent on large patches of forests, with Hakka settlements on mountains giving them a final hit. Finally, other more resilient predators such as tigers and foxes went locally extinct when rural population surged once again under British rule, with habitats heavily fragmented by roads and railways. Urbanization might actually be beneficial to preserving forests since people living in cities are no longer involved in agricultural activity, and does not have to depend on trees on hillslopes for fuel wood.

The main message is, the ecosystem in Hong Kong is degraded very early in history.
頂部
jasonpoon
蟲蛹
Rank: 3Rank: 3Rank: 3


UID 869
Total 1340
主題
回覆
精華 0
積分 2948
種子 2948
花蜜 1209
閱讀權限 50
註冊 2007-3-29
Pri. Camera:  Olympus
來自 HK
狀態 在線
發表於 2017-5-22 17:15  資料 短消息 
"Typhoons might be important in genetic remixing. However, I suppose that is more relevant to insects, plants, and birds? It is hard to imagine fish being blown off from one stream to another. I actually think that freshwater fish, especially primary freshwater fish that never leaves the river basin it is in, are quite genetically isolated. There has been quite a lot of examples of impressive adaptive radiation and the evolution into different morphs in some freshwater fish taxa. Examples include the three-spine sticklebacks in North America showing high regional variation, guppies in Trinadad with different morphs below and above the waterfalls, and the amazing cichlids in Lake Victory and Lake Malawi."

I must point out that the hypothesis has to find supports in Typhoon and Hurricane Belts of the world, amongst other factors. The occurance of geographically close varieties or subspecies in areas not affected by that level of wind disturbance is evolutionarily predicted. Adaptive radiation in African Rift Lake Cichlids depends on occurance of micro habitats within the lakes - that are relatively stable and not disturbed on large scale.

Possible wind dispersal for large animals such as snails and lizards are not uncommon in studies around the Caribbeans and East Atlantic Islands. Individuals need not be mature and could be smaller juveniles to be carried by typhoon scale wind. I think of variations and species of fishes in highly isolated primary freshwater environment eg. high reach of valleyed hillstreams...
頂部
Aland
幼蟲
Rank: 2Rank: 2



UID 6332
Total 359
主題
回覆
精華 0
積分 5062
種子 5062
花蜜 356
閱讀權限 60
註冊 2015-1-28
Pri. Camera: 
狀態 離線
發表於 2017-5-23 18:42  資料 文集 短消息 


QUOTE:
原帖由 jasonpoon 於 2017-5-22 17:15 發表
I must point out that the hypothesis has to find supports in Typhoon and Hurricane Belts of the world, amongst other factors. The occurance of geographically close varieties or subspecies in areas not affected by that level of wind disturbance is evolutionarily predicted. Adaptive radiation in African Rift Lake Cichlids depends on occurance of micro habitats within the lakes - that are relatively stable and not disturbed on large scale.

Possible wind dispersal for large animals such as snails and lizards are not uncommon in studies around the Caribbeans and East Atlantic Islands. Individuals need not be mature and could be smaller juveniles to be carried by typhoon scale wind. I think of variations and species of fishes in highly isolated primary freshwater environment eg. high reach of valleyed hillstreams...

Do you have any research papers related to how typhoons could disperse relatively larger animals such as lizards and snails? I have definitely hear about spiders and insects being dispersed by wind, but not much about snails and lizards.
頂部
jasonpoon
蟲蛹
Rank: 3Rank: 3Rank: 3


UID 869
Total 1340
主題
回覆
精華 0
積分 2948
種子 2948
花蜜 1209
閱讀權限 50
註冊 2007-3-29
Pri. Camera:  Olympus
來自 HK
狀態 在線
發表於 2017-5-23 21:49  資料 短消息 
General discussions on wind dispersal maybe searched in www.


For lizards/geckos, the following papers could be found:
Censky, Ellen J.; Hodge, Karim; Dudley, Judy (1998), Over-water dispersal of lizards due to hurricanes, Nature, 395: 556, doi:10.1038/26886

https://www.infona.pl/resource/b ... 8-8aed-d557f2360c79


For snails, the wiki reference is:
https://en.wikipedia.org/wiki/Orthalicus_reses


In general, there was a "Intermediate Disturbance Hypothesis" which theorized upon related issues of diversity and disturbance.

[ 本帖最後由 jasonpoon 於 2017-5-23 22:06 編輯 ]
頂部
 


Untitled Document


當前時區 GMT+8, 現在時間是 2017-5-23 22:46

Powered by Discuz! 5.0.0  © 2006-2008 HKWildlife.Net
Processed in 0.044183 second(s), 10 queries , Gzip enabled
清除 Cookies - 聯繫我們 - HKWildlife.Net - Archiver