Most likely, they are a species which is poorly adapted to the climate and competition from other plants, and the seedlings do not survive.

Resin

Do these pines probably need some specific type of insect to pollinate? No, pines are wind-pollinated

Do seeds may need to be eaten by some animal to be fertile? No, although being buried by squirrels spreads some pines, and others actually need a forest fire.

Probably they aren't finding any good spot for seedlings to survive and sprout, or they sprout and are eaten immediately by something.

the link states:

The main pine species are Pinus taeda,P. elliottii,P. caribaea and P. caribaea x P. elliottii.
Growth rates are phenomenal with mean diameters of over 31cm at age 13
and 18-22 year rotations being the norm.

i googled 'pine forest in Argentina'

could Resin interpret his comment in regard to this info??? .. i am simply curious... as i never heard of any of them ....

perhaps if they are growing this fast ... there wont be many seedlings inside the plantation ... as they would be shaded out.. by the time the trees get to cone bearing age ... so then they would have to look to the periphery for seedlings ...

ken

Here is a link that might be useful: pdf link

Despite everybody planting P. abies and P. pungens in this area, I've never found chance seedlings of either. I think Ken has mentioned finding seedlings where he is, only 30 miles from my home. It's interesting the part environment plays on this.

At least in the case of P. elliottii, the home range-S. Florida-is a region where pyric plant communities are (or were) the rule. Fire may be necessary to open the cones, to clear away ground-layer competition, or some as yet unspecified function in the landscape.

Here in Wisconsin are many non-native spruce, most typically Picea abies and P. pungens. It would be false to state that these species never regenerate on their own, but it is a rare occurrence. We've discussed this here before, but so far as I remember, no satisfactory answer has been crafted to date.

It's a good question you ask, Alienado, and has implications across a wide area of the globe where non-native conifers are being grown-both from the standpoint of those who would like to see regeneration, and those for whom this would represent invasiveness.

+oM

[Quote]Most likely, they are a species which is poorly adapted to [...] competition from other plants, and the seedlings do not survive.[/quote]

The only other species present is the grass pictured in the image. I don't know how competitive is that grass, but it may explain why there are no other native trees.

Any tree planted, grows very well, with little or no care, and yet the mountains run for hundreds of kilometers without any tree on view.

[Quote][...] or they sprout and are eaten immediately by something[/quote]

The place has wild guinea pigs, some deer and guanacos. But it would be weird that not a single tree grows nearby, after decades. Someone should survive.

[Quote]could Resin interpret his comment in regard to this info??? [/quote]

Sure. I don't know what specific species they are, but I want to hear theories. I'm also leaded by curiosity.

[Quote]Despite everybody planting P. abies and P. pungens in this area, I've never found chance seedlings of either[/quote]

I googled 'Picea Pungens', and found that that species only reproduces after 20 years old!, and that the seeds only reproduce with more than 16 hours of light per day. Maybe these light conditions are more common near of the poles (the (south) latitude here is comparable to Miami, Florida, or North of Africa.

Here is a link that might be useful: Picea pungens

Alienado, I would suggest researching the original vegetation and plant community types of the region you describe, then look into the history of what has taken place there-most usually since European settlement-if that applies to the area. It can be difficult to trace backwards through time when all or virtually all of the original vegetation has been long gone. Also, are there any preserves at all, to help indicate what might have been growing there before?

Then too, grasses are often very tough competitors for tree seedlings. Around here for example are large stands of reed canary grass-Phalaris arundinacea-which all but precludes colonization by pioneer tree species, at least for a time. Land I own where this is the case is being slowly captured by balsam poplar-Populus balsamifera-albeit it takes time for this to happen. Grasses can be very staunch competitors.

+oM

Not a conifer, but do any of the Puya genus grow where you are? Patagonia is an amazingly fascinating place, biologically.

The specific questions you ask all have the answer "No" for practical purposes. But they are good questions, because planted trees grow well: therefore the problem is in the reproductive system. A short-cut to your basic question of "why no seedlings" can be gotten by answering the following questions from observation:
1. are there mature cones at any time of year?
2. if so, are there filled seeds in those cones?
3. do the cones open, to allow escape of the seeds?
If any of these answers are "No", then there is a breakdown in the normal reproductive system.
A simple experiment would be to harvest filled seeds (if any) and plant them 2 cm deep in soil from which the grass cover has been scraped away. Do this with some directly from the cone, and some that have been chilled 30 days in a refrigerator wrapped in a moist cloth or sand. Check frequently to look for germinants. Protect the seeds with metal screening.
Of course you also must find out what species you have. You should post good photos of cones and seeds, if you find some, needles, and bark. This forum can help.
Verify your basic observations of the absence of seedlings. I am skeptical about your statements about "dozens of decades" [really?], "not a single tree", and "totally wild". Don't accept impressions from years ago; make fresh observations to see if you can falsify your current beliefs. Find out if there are seed-eating rodents or ground birds present all over the area.You will have fun.

I get chance seedlings of Picea Abies - our summers tend to be somewhat cooler and the humidity fairly low which I read does help with germination rates. It's a pretty common yard tree here but many of them are now reaching the end of their useful life. I have them in all stages in abandoned soil filled pots left out on my patio. I've transplanted a few which are doing quite well - best when I don't uproot them but simply cut away the pot and plant the entire intact dirt ball - less impact on the environment they were used to.

Have a perfectly shaped two footer in a crack in my retaining wall steps. Can't get it out so it'll be a table top Christmas tree this year.

Some common pine wood I've seen sold here, grown in I think Chile, is Radiata pine. May be the same there being close neighbors?