wmartin

For some time now, I've believed it would be good idea to chop down many/most paper bark trees in Tai Po Kau Forest reserve.

Walking thro paper bark groves, they seem pretty bad for birds - and, by the looks of things, biodiversity overall. Not much else growing there; in an otherwise diverse forest area, seems a bit like monoculture - akin to gigantic wheat field!
These trees are often big; but felling them might help some of existing other trees grow, as well as more saplings etc, leading to enhanced biodiversity here I reckon. (Yes, something of a guess on my part - I'd be intarested in opinions here)

Prompted to post this morning as only just come across this:

December 2001, Porcupine! 24: 19-20
Is Paper Bark Tree becoming invasive in Hong Kong?
By Billy C.H. Hau
[not quite same issue - the paper barks in TPK were planted, I believe]

Even if naturalists in HK were to support idea, perhaps removing a few trees as a test, I imagine more than a few desk bound bureaucrats might be startled by the notion.

[ Last edited by Webcreeper at 12/09/2008 04:18 ]

wmartin

I hadn't heard re this before; but not at all surprised re officials. [As pretty much common knowledge in oonservation, really protecting biodiveristy doesn't just mean hands off approach, esp when it comes to exotic species.]

I emailed Billy Hau (assistant prof in HKU's ecol n biodiv dept] re this; his response:

Quote:

I would say in fire prone area, they should be cut because fire will allow the species to spread. If there is no fire, they will not be able to reproduce as their seeds will be trapped in the seed capsule and cannot germinate. This species needs fire to reproduce even in it's native range i.e. Australia. Those in TPK is probably ok. The strategy may be to thin out some of them mature trees and at the same time plant some native tree seedlings behind them. This improvement process will take a long time but we need some patients to due with forest.

As well as Tai Po Kau, there's also major paper bark stand in northwest Shing Mun area - roughly west of the real nice fung shui wood. Another place where I find birding quietens down a lot.

I also sent email re paper bark chopping to KM Yeung at AFCD; rather hope he'll pass to someone who will reply. But - as w H5N1 (and Deep Bay's rising mudflats) - science based replies not always the forte of afcd; hope this proves different.

[ Last edited by wmartin at 10/09/2008 09:54 ]

wmartin

Glad this has prompted some discussion, and there is some similar thinking from folk who know re birds etc.

As I understand it, paper barks planted in several places as they can grow in damp areas (even places that are flooded at times).
But, to me, they're too extensive already; I'd be up for retaining, say, the paper barks that grow right by Shing Mun Reservoir, and have bases underwater when the reservoir is very high. But those in northwest of the area are on what could be prime site.

Wider biodiversity is impacted.
Tai Po Kau, say, is tiny by forest standards; and within this, the area of good tree diversity is tinier still (if other tree species could use some thinning, to give more diversity a chance, would seem good too). Plus, typical to get biodiversity higher in lower areas, and closer to streams - so paper barks here, and at Shing Mun, "hogging" what should be one of richer parts of the forest. With better trees here, will get wider benefits.
Hong Kong has close to 400 native tree species; not at all a place where it's remotely natural to have single species stands dominating sectors of prime areas. In moist tropics, a tendency for tree species to be well spread, so an individual here, another there. This in turn leads to greater diversity overall; and surely more attractive to human visitors, even if they don't care too much about finding certain birds, butterflies or whatever.

Intersting re having them killed and left to stand, rot. Some, anyway.

Should be possible to find expert advice on such matters, inc from overseas.
I reckon Hong Kong should serve as strong example of forest regeneration in the tropics. (Reached this conclusion partly after reading some research on forests and conservation in Borneo: plenty of info there on forests that had been felled to varying extents, but not on planted/regenerated forests that were some decades old.)
But this example is based on far-sightedness in the past: what a superb idea to make Tai Po Kau a special area, with species diversity!
Nowadays, some more far-sightedness - and even courage(!) - could be helpful.

Already, Hong Kong's forests are immensely impoverished compared to their original state: can only guess what we have lost. (No breeding woodpeckers shows the terrible effecitiveness of past deforestation: should be several species here, based on sub-tropical forest in region)
Holding back biodiversity not so good, now, unless for strong reason.

wmartin

Briefly:

Good to see further replies n thought.

Yes, a complex issue.

I believe that assessments of insect diversity would be faster ways of better reflecting values of areas of forest (those with good tree variety, inc native species; those with woeful variety verging on monoculture, w non-natives)
Birds, though, v useful and obvious, tho ranges surely mostly larger than many a single species stand.

Species like magpie robin, spotted dove, long-tailed shrike not forest birds: naturally, I'd guess would have been more limited to places where trees fell down, or maybe fires. Man helped these, as sparrows.

Bit surprised re the Taiwan result; I'd figured that thinning paper barks would pretty quickly increase bird divdersity, initially with birds favouring clearings/shrub land.

I've a book by CIFOR (researches forests), on felling in Borneo - bit like reverse of situation we're discussiong, as go from full, natural forest, thro various degrees of felling timber. Initially, most species remain; but eventually, get fewer and fewer forest species, more of the generalists (and lower diversity overall, even if populations of some species pretty high).
In this, woodpecker diversity declined, but not to zero in any plots that weren't clear felled, as I recall. This led to me thinking just how horribly effective Hong Kong's deforestation was.

wmartin

Good to see article in yesterday's South China Morning Post, re AFCD having embarked "on a programme that will gradually phase out exotic tree species and replace them with local ones".
Says that at 21 country park sites, exotic species that had been widely planted on barren land after Second World War will be removed to make way for mix of local species.
"Thousands of the trees will be felled this winter, with new species belonging to local species to be planted in spring".

Yippee!

- now if could but get some of the axemen to come over to Cheung Chau, chop down a load of acacias, and replace with some mix of local species, my local patch might see an upsurge in bird diversity...