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Interesting... it's hard to tell if the broadleaf evergreens like madrones go dormant or not. I always assumed they did and maybe only started growing during a warm spell in winter.
I don't know about madrones, but I know rhododendrons will droop their leaves during frost to preserve water which would signify that it's not fully dormant as it's still reacting to it's environment? Also Camellias flower in the middle of winter here. Also weeds do grow in the middle of winter and unattended gardens will be overgrown with them by the time early spring rolls around. Are there any trees/woody shrubs that actively put out new growth in the middle of winter in any subtropical climates?
also if you want to go into further detail on winter dormancy in relation to oceanic climates, you can discuss it in my new thread https://www.city-data.com/forum/weat...on-system.html since this thread is specifically about humid subtropical climates, Cfa.
I don't know about madrones, but I know rhododendrons will droop their leaves during frost to preserve water which would signify that it's not fully dormant as it's still reacting to it's environment? Also Camellias flower in the middle of winter here. Also weeds do grow in the middle of winter and unattended gardens will be overgrown with them by the time early spring rolls around. Are there any trees/woody shrubs that actively put out new growth in the middle of winter in any subtropical climates?
also if you want to go into further detail on winter dormancy in relation to oceanic climates, you can discuss it in my new thread https://www.city-data.com/forum/weat...on-system.html since this thread is specifically about humid subtropical climates, Cfa.
Good points... back to Cfa climates. I think Cfa should be split up into a temperate and subtropical categories as outlined in the thread you linked. It is way too broad under Koppen.
Personally I don't like palms in Atlanta. They look too out of place. We are firmly in a mixed forest area where palms aren't gonna grow randomly in nature on their own.
I'm afraid I'll have to contradict you on this one. Atlanta/DeKalb County is very near the native range of Dwarf Palmetto. Similarly, Dallas is actually within it despite not being on the Coastal Plain.
There are also non-Coastal Plain areas of Oklahoma and Arkansas with native dwarf palms. All they need is a warm climate - including ones with light freezes on average winter nights - and wet soil. I actually find it quite odd that they're not native to Memphis, which is on the swampy coastal plain and doesn't even get light freezes on the average winter night; very similar to Virginia Beach (P.S. yes there are actually native dwarf palms in Virginia Beach, but the USDA obviously under-reports counties on other maps too like this, this and this).
Some sources even suggest there are native dwarf palms near Chattanooga and/or Huntsville, too (which is entirely possible given their warm climates).
Quote:
Originally Posted by grega94
also if you want to go into further detail on winter dormancy in relation to oceanic climates, you can discuss it in my new thread https://www.city-data.com/forum/weat...on-system.html since this thread is specifically about humid subtropical climates, Cfa.
Except monocots, I'm pretty sure you need a winter mean of at least 10C/50F for even fast-growing evergreen stuff to put out growth all winter. Remaining active and performing photosynthesis aren't the same things as growing significantly. Palms, bamboos (including canes) and woody yuccas do sometimes put out new growth in winters that aren't very warm, but they have different wood and are still slower - not to mention most yuccas (even some woody ones) are just unique shrubs anyways, while bamboos are literally just giant grass with hard, tree-sized stems.
Which is why I believe places with winters over 10C/50F but under 18C/64F - even freeze-prone ones like Mobile and mild-summer ones like San Francisco - deserve a separate, semi-tropical title. Those climates also support citrus and some other mainly-tropical plants more easily than most climates outside that range, unless they're places like Eureka Calif. or Wellington that have few to no freezes per winter and are only barely below 10C/50F (but even they only support limited varieties of non-hardy citrus).
Last edited by Sun Belt-lover L.A.M.; 04-13-2020 at 02:50 AM..
I'm afraid I'll have to contradict you on this one. Atlanta/DeKalb County is very near the native range of Dwarf Palmetto. Similarly, Dallas is actually within it despite not being on the Coastal Plain.
There are also non-Coastal Plain areas of Oklahoma and Arkansas with native dwarf palms. All they need is a warm climate - including ones with light freezes on average winter nights - and wet soil. I actually find it quite odd that they're not native to Memphis, which is on the swampy coastal plain and doesn't even get light freezes on the average winter night; very similar to Virginia Beach (P.S. yes there are actually native dwarf palms in Virginia Beach, but the USDA obviously under-reports counties on other maps too like this, this and this).
Some sources even suggest there are native dwarf palms near Chattanooga and/or Huntsville, too (which is entirely possible given their warm climates).
Well admittedly drawf palmettos weren't quite what I had in mind.
I used to live in Houston where you'd see something like this or this. Obviously the shopping center palms were planted and I'm sure the ones on the highway were put there too. But they obviously can grow to a height I haven't seen anywhere in Atlanta. It's one thing for a homeowner or a development to care for a palm during cold outbreaks but I doubt TXDOT is caring for each individual palm off the freeways.
I've seen some palmettos, but they're very isolated and almost always put there on purpose. I get outside a lot and I don't think I've seen any that weren't obviously put there on purpose. I still think they look out of place compared to south Georgia, Houston, etc.
Which is why I believe places with winters over 10C/50F but under 18C/64F - even freeze-prone ones like Mobile and mild-summer ones like San Francisco - deserve a separate, semi-tropical title. Those climates also support citrus and some other mainly-tropical plants more easily than most climates outside that range, unless they're places like Eureka Calif. or Wellington that have few to no freezes per winter and are only barely below 10C/50F (but even they only support limited varieties of non-hardy citrus).
Your explanation somewhat works to explain the lower cutoff but why the upper cutoff at 18C/64F? What makes 16-17C different from 18C, and what does a 16-17C winter have in common with a 10C winter?
Your explanation somewhat works to explain the lower cutoff but why the upper cutoff at 18C/64F? What makes 16-17C different from 18C, and what does a 16-17C winter have in common with a 10C winter?
Koppen chose 18C as the boundary for fully tropical climates because it's the limit for long-term health of certain tropical palm species.
Koppen chose 18C as the boundary for fully tropical climates because it's the limit for long-term health of certain tropical palm species.
Besides that being not true, why do you agree with Koppen when he chooses 18C as the isotherm for tropical but not 0C as the isotherm for subtropical? What makes one more or less arbitrary than the other?
If you look at southeastern Africa, eastern Australia, northern Vietnam/SE China, and even Florida there is no clear ecological or floristic boundary that occurs at 18C. Around 15-16C seems like a better cutoff for contiguous tropical vegetation (where rainfall and/or lack of hard freezes allows) and/or significant spillover into the "subtropical" zone. The 21-22C boundary would be a good starting place for the contiguous deep tropics, places that likely remain tropical even during glacial periods. Plants from these areas are more likely to have no genetic resistance to any kind of cold or chill.
Besides that being not true, why do you agree with Koppen when he chooses 18C as the isotherm for tropical but not 0C as the isotherm for subtropical? What makes one more or less arbitrary than the other?
If you look at southeastern Africa, eastern Australia, northern Vietnam/SE China, and even Florida there is no clear ecological or floristic boundary that occurs at 18C. Around 15-16C seems like a better cutoff for contiguous tropical vegetation (where rainfall and/or lack of hard freezes allows) and/or significant spillover into the "subtropical" zone. The 21-22C boundary would be a good starting place for the contiguous deep tropics, places that likely remain tropical even during glacial periods. Plants from these areas are more likely to have no genetic resistance to any kind of cold or chill.
Oh. I thought it was at least close for coconut palms (Tampa and Brownsville have them, but they don't last long-term, similar to California Fan Palms in St. George or Las Cruces). I'd probably agree with 16C more than 15C or 21-22C, though, as Florida can get freezes rarely even over 18C, and 21-22C places would still cool off during glacial periods (although less).
However, there is a remnant of what was tropical rainforest during the Last Glacial Period that has neither expanded much nor disappeared, which is in far northern New Zealand. It doesn't even meet 15C though. Which is why I believe a semi-tropical category needs to be added between 10C and whatever isotherm is used for fully tropical climates. I imagine it can't have been below 10C even in the LGM, as it's right by the Pacific and was still tropical rainforest then. So warming has occurred quite unevenly, even far from the poles.
However, there is a remnant of what was tropical rainforest during the Last Glacial Period that has neither expanded much nor disappeared, which is in far northern New Zealand. It doesn't even meet 15C though. Which is why I believe a semi-tropical category needs to be added between 10C and whatever isotherm is used for fully tropical climates. I imagine it can't have been below 10C even in the LGM, as it's right by the Pacific and was still tropical rainforest then. So warming has occurred quite unevenly, even far from the poles.
New Zealand does have a lot of tropical descended vegetation from recognizable tropical genera but as far as actual continuity with solidly tropical zones, there isn't as strong as of a connection. Eastern Queensland at 27-28*S and the same latitude in SE Brazil, SE Africa etc share many of the same species (or even the majority) with areas 5-10 degrees closer to the equator. You could say biodiversity-wise they have more in common with somewhere 17 degrees from the equator than 37 degrees from the equator. Higher continental influence in east Asia and the American subtropics pushes this boundary closer to the equator around 26*N.
15C mean temperature is the magic number for coconuts. They only die in central Florida/south Texas mostly because of cold snaps. They do fine long term elsewhere in the world with winter mean temps mostly 15C+ with rare or nonexistent freezes
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Quote:
Originally Posted by Asagi
New Zealand does have a lot of tropical descended vegetation from recognizable tropical genera but as far as actual continuity with solidly tropical zones, there isn't as strong as of a connection. Eastern Queensland at 27-28*S and the same latitude in SE Brazil, SE Africa etc share many of the same species (or even the majority) with areas 5-10 degrees closer to the equator. You could say biodiversity-wise they have more in common with somewhere 17 degrees from the equator than 37 degrees from the equator. Higher continental influence in east Asia and the American subtropics pushes this boundary closer to the equator around 26*N.
15C mean temperature is the magic number for coconuts. They only die in central Florida/south Texas mostly because of cold snaps. They do fine long term elsewhere in the world with winter mean temps mostly 15C+ with rare or nonexistent freezes
They do best in year round humid heat, which is why their native area is coastal Vietnam and Phillipines
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