The best climate is the Subtropical,because respond better to the low and higth precipitation

Thanks Antonio,

Yes, absolutely. In tropical regions like those located at the tropical forests both temperature and humidity are in the good conditions for plant growth throughout the year and therefore they have not distinct or different seasons. But I am looking for a proxy to show past seasonality changes in such regions that you mentioned.

Dear Reza,

Compound-specific hydrogen isotopes of plant lipids may be the way forward here. For a start, have a look at Henderson et al. (2010, EPSL, 300, 205-214: Holocene precipitation seasonality captured by a dual hydrogen and oxygen isotope approach at Steel Lake, Minnesota), for example.

Cheers,

Jens

Thanks Koen.

Thank you Jens, I studied abstract of  your recommended paper, it seems to be helpful.

In very simply way to say is If you have appearance of cold and warm water  taxa of phytoplankton in assemblage. 

Dear Reza,

To me one of the best proxy to demonstrate clime change, is magnetic susceptibility, which is very cost and time effective method. This parameter has very high ability to record the smallest variation in climate change which in turn reflects variation in temperature and humidity.

With best wishes,

Habib.

You can also use as a proxy foraminifera and stalagmite cave deposits. 

climate proxies  to show seasonality changes  are dependent on the sediments, e.g., the fossil Coral

Thank you all for your answers. 

I know some archives like speleothem, coral and tree rings are very suitable to study seasonality changes but my focus is on lake sediment cores.

Dear Habib thank you,

There is a robust hypothesis which suggests Zagros Mountains as a part of the interior Middle East has experienced a longer hot, dry season during early Holocene which caused a delay in oak woodland expansion until the mid-Holocene. In your opinion is magnetism susceptibility (MS) able to demonstrate such subtle changes in the seasons?

In a core taken from a wetland located at the Zagros that I worked on, mean sedimentation rate was ~ 33 yr/cm and when we measured MS of the core by 1cm intervals it does not show any drastic change in the early Holocene climate. Thus, I think ability of MS to demonstrate such subtle changes is related to sedimentation rate of the lake and when sedimentation rate is high and it takes just a few years to deposit one centimeter of sediment, measuring MS in close intervals could help to study seasonality changes. So I think MS is an effective proxy to reveal the large climate changes like glacial/interglacial transitions. 

Thank you Simon for your answer.

Hi Reza :

Vegetation and selected plants or trees can bring, in some cases, information on rainfall seasonality. This is also shown by modeling approcah.

See e.g., for data :  Vincens A., Garcin Y. & Buchet G. (2007). Influence of rainfall seasonality on African lowland vegetation during the Late Quaternary: pollen evidence from Lake Masoko, Tanzania. Journal of Biogeography 34, 1274–1288.

and  for modelling approach :  Gritti E.S., C. Cassignat, O. Flores, R. Bonnefille, F. Chalié, J. Guiot, and D. Jolly (2010). Simulated effects of a seasonal precipitation change on the vegetation in tropical Africa. Clim. Past, 6, 169-178, 2010.

Phytoplankton ( in particular diatoms ) are potentially good indicators of seasonal variations of the surface lake water chemistry (hence, of the climate on the lake-catchment area), since they show a short duration life-cycle ( work in progress and publication in prep. on this use of diatom data ).

Very interesting and usefull question, your rise, Reza !

      Françoise.

I agree with Françoise Chalie regarding to diatoms. Last few years I'm also dealing with diatoms in Holocene coastal lake sediments and the papers are in preparation too. I'm looking forward to your paper Françoise.

Françoise, thanks a lot  for your answer.

Salam Reza, Hale chetori? Khoobi? Che khabar? As you know from my publications I have been looking at seasonality changes in the American West for the last 30 years, and am now investigating it in the pollen records that are already published. Remember that grasses are a good summer rainfall indicator, and that in general junipers are a good winter rainfall indicator. I am sure that oak's arrival in the Zagros is related to a change in seasonality as well as to a change in the total rainfall amount in the region. Erosion records from the region suggest reduced rainfall, and the pollen records from the south of Iran suggest monsoon penetration, while those in the north suggest increased strength of the westerlies bringing summer storms into the area from the Mediterranean. This is not the kind of rainfall and temperature regime that favored oak. Depending upon which oak you are talking about, most are winter wet, summer dry regime favoring. For example, those oaks in California. During the Pleistocene California Oaks seem to have retreated south into Mexico, were temperatures were warmer. I have a pollen record from a lake near Bakersfield, California which indicates that at the glacial maximum oak, which is abundant in the region today, was not present during the Glacial Maximum. So it seems that in California the re-advance of oak was related both to seasonality and temperature. Here is an example from Iran that you saw in my presentation in May...look at the period between 12500 and 8000 years ago. You can see that grasses are doing well, but those species which depend upon winter rainfall are not doing well. So pollen is an excellent measure of seasonality.

Looking for seasonality on a scale of 1000 and more...interesting.

Hi Dear, 

Away from my specialty, but I was reading in that topic for a while. Carbon isotopes in snail shells provide robust information about seasonality and environment. You may want to check out these articles: 

Carbon and oxygen isotope variations within the shell of an African land snail (Limicolaria kambeul chudeauiGermain): a high-resolution record of climate seasonality...MJ Leng, THE Heaton, HF Lamb, F Naggs - The Holocene, 1998 - hol.sagepub.com. 

Stable carbon and oxygen isotopic variations in modern Rabdotus land snail shells in the southern Great Plains, USA, and their relation to environment

GA Goodfriend, GL Ellis - Geochimica et Cosmochimica Acta, 2002 - Elsevier

Best, 

Mohammed

Hello Reza, 

I am not really experienced in seasonality studies, I was following the question because I found it interesting. Although there are already nice suggestions, you might want to check the outcome papers of PALEOVAN project. 

the project aimed paleoclimate reconstruction for lake Van in Eastern Turkey and there are ICDP cores which lots of people did multi proxy research. and here is the special issue :  

Quaternary Science Reviews

Volume 104, 15 November 2014, Pages 1–7

Special Issue: Results from the PALEOVAN Drilling Project: a 600,000 year long continental archive in the Near East

I hope that helps, 

Best,

Zeynep

Dear Peter,

Thanks for your answer.

I agree pollen analysis is a suitable proxy to show seasonality. But the Holocene vegetation changes of Zagros_Anti-Taurus especially abrupt expansion of the Poaceae in beginning of the Holocene and gradual increase of oak woodlands during early to Mid-Holocene made the interpretation of the pollen diagrams complicated. Up to now, there is not any palynological research in southern part of Iran which spans whole of the Holocene era, and our knowledge of palaeoclimate of this region is based on some sparse geomorphologic researches which suggest a wet period during early Holocene in the eastern and southeastern parts of Iran. This wet period is attributed to Indian summer monsoon expansion to these regions. Pollen diagrams of the Zagros and NW Iran show early Holocene has been warmer and drier than present and especially hot, dry season has been longer and all lakes have experienced low levels and Hashilan Wetland in middle Zagros has desiccated periodically. Some researchers suggested summer rainfall during early Holocene caused the expansion of grasses, but in my opinion Zagros has not received Mediterranean summer rainfall during the early Holocene. The dominant oak species of the Zagros is Quercus Brantii Lindl. This oak species can tolerate very low winter temperatures but is sensitive to high and especially late snowfall. Slight increases in growing-season moisture can favor the expansion of populations of this tree, whereas a long summer drought inhibits seed germination and establishment of its stands. Therefore, it seems the delay in Zagros oak woodland expansion is related to longer hot, dry seasons in the early Holocene. Gradual trend of the woodland expansion more probably is dependent on shortening of the hot, dry season from early to mid-Holocene.

Zeynep,

Thanks for your answer.

I have already studied the paper that you recommended to me. This is one of the main sources of information about climate conditions of the interior Middle East during late Pleistocene glacial and interglacial periods. The pollen analysis performed on 1 meter intervals and so these data could only be valuable to demonstrate the general trend of the climate conditions during the Quaternary, therefore due to the low resolution of the pollen analysis, the Holocene seasonality changes cannot be tracked in this research.

If you have diatoms in your samples, You should definitely tried to do some analyses on it. They could tell you not just about climate and seasons, they are very good indicator of environment (temperature, river influx, nutrients, salinity, sreatification, water level changes, oxic/anoxic conditions...).

Best wishes! :)

For to resolve proxy climate, they are two: subtropical climate (tropical dry) and semiarid climate, between the two is the displacement of climate change.

Changes in temperature and humidity in both cases are very clear, seasonal and annual basis. I try this in the process of desertification and climatological analysis of climate variability both states is agree with the seasons shortening or lengthening the period of moisture or drought.

In sediments and alluvial soils and lake sediments can be seen this kind of change by varying the deposition of salts and mineralogy and particle size of the materials.