Could phenological records from Chinese poems of the Tang and Song dynasties (618–1279 CE) be reliable evidence of past climate changes?

Phenological records in historical documents have been proven to be of unique value for reconstructing past climate changes. As a literary genre, poetry reached its peak in the Tang and Song dynasties (618–1279 CE) in China. Sources from this period could provide abundant phenological records in the absence of phenological observations. However, the reliability of phenological records from poems, as well as their processing methods, remains to be comprehensively summarized and discussed. In this paper, after introducing the certainties and uncertainties of phenological information in poems, the key processing steps and methods for deriving phenological records from poems and using them in past climate change studies are discussed: (1) two principles, namely the principle of conservatism and the principle of personal experience, should be followed to reduce uncertainties; (2) the phenological records in poems need to be filtered according to the types of poems, background information, rhetorical devices, spatial representations, and human influence; (3) animals and plants are identified at the species level according to their modern distributions and the sequences of different phenophases; (4) phenophases in poems are identified on the basis of modern observation criteria; (5) the dates and sites for the phenophases in poems are confirmed from background information and related studies. As a case study, 86 phenological records from poems of the Tang Dynasty in the Guanzhong region in China were extracted to reconstruct annual temperature anomalies in specific years in the period between 600 and 900 CE. Following this, the reconstruction from poems was compared with relevant reconstructions in published studies to demonstrate the validity and reliability of phenological records from poems in studies of past climate changes. This paper reveals that the phenological records from poems could be useful evidence of past climate changes after being scientifically processed. This could provide an important reference for future studies in this domain, in both principle and methodology, pursuant of extracting and applying phenological records from poems for larger areas and different periods in Chinese history.

How could phenological records from the Chinese poems of the Tang and Song Dynasties (618–1260 AD) be reliable evidence of past climate changes?

Phenological records in historical documents have been proved to be of unique value for reconstructing past climate changes. As a literary genre, poetry reached its peak period in the Tang and Song Dynasties (618–1260 AD) in China, which could provide abundant phenological records in this period when lacking phenological observations. However, the reliability of phenological records from poems as well as their processing methods remains to be comprehensively summarized and discussed. In this paper, after introducing the certainties and uncertainties of phenological information in poems, the key processing steps and methods for deriving phenological records from poems and using them in past climate change studies were discussed: (1) two principles namely the principle of conservative and the principle of personal experience should be followed to reduce the uncertainties; (2) the phenological records in poems need to be filtered according to the types of poems, the background information, the rhetorical devices and the spatial representations; (3) the animals and plants are identified to species level according to their modern distributions and the sequences of different phenophases; (4) the phenophases in poems are identified on the basis of modern observation criterion; (5) the dates and sites for the phenophases in poems are confirmed from background information and related studies. Finally, the temperature anomalies reconstructed by phenological records from poems were compared with those reconstructed by other historical documents in published studies to demonstrate the validity and reliability of phenological records from poems in studies of past climate changes. This paper proved that the phenological records from poems could be useful evidence of past climate changes after being scientifically processed and also provides a reference in both principle and methodology for the extraction and application of phenological records from poems.

SOME RESULTS OF PHENOLOGICAL OBSERVATIONS OVER THE MAIN NECTARIFEROUS-POLLINIFEROUS PLANTS OF THE CHUVASH REPUBLIC

It has been proven that favorable prerequisites for the development of bee colonies and the production of high honey flow are created in cases when the apiary is fully surrounded by nectariferous lands (landscapes): forests, meadows, gardens, fields and forest belts with biodiversity of nectar-pollen flora, i.e. a continuous honey flow appears or a flower-nectar conveyor is created. During the phenological observations, beekeepers assured themselves that in order to clearly and fully utilize the nectar-pollen flora, it is necessary to have information from many years of research on the progression of the flowering of the presented plants, starting from early spring and ending in the fall at the end of the beekeeping season. Accurately compiled data of perennial phenological records and a calendar of flowering of entomophilous plants guarantee the beekeeper's opportunities to more rationally control their actions in doing the beekeeping business and improving the honey flow by including newly introduced plants in the flower conveyor that more completely fill the non-honey flow periods. It is safe to hope that, based on the analysis of regular perennial phenological records, each apiary beekeeper can predict the honey flow and make an adjustment to the technology of keeping and caring for the bee colonies. The beekeepers of the apiary of OOO Pchelovodcheskoe of the Kravsnoarmeysky district of the Chuvash Republic have become convinced that by knowing the beginning and end of the full flowering of nectariferous-polliniferous plants, its duration can be determined. Depending on the strength of the honey flow, there are: a no honey flow period, when the bee colony on the control weights shows a decrease in the total mass; supporting honey flow, when the scales show from 0 to 0.6 kg of profit, while the honey in bee colonies does not increase in the direction of profit and does not accumulate in an amount sufficient for pumping the marketable honey; productive honey flow, when reference scales show from 1 kg or more of nectar profit per day. In this case, the amount of ripe honey in colonies will be sufficient for selection and pumping. It should be noted that the main honey flow is the strongest productive honey flow when from each main wintering colony, full unopened honeycomb frames from several honey chambers or shells are pumped out, which is the eventual result of the economic efficiency of the apiary. Analysis of the results of phenological observations allows us to note the shift of the period of the beginning and the end of flowering in other plant species. It should be noted that in both 2017 and 2018, the species composition of the flora in the investigated area has blossomed continuously, ending in August and September: in European goldenrod (Solidago virgaurea) - 01/09/2017 and 28/08/2018; in common globe thistle (Echinops sphaerocephalus) - 09/05/2017 and 08/20/2018.

Aerial map demonstrates erosional patterns and changing topography at Isimila, Tanzania

Phenological shifts represent one of the most robust bioindicators of climate change. While considerable multidecadal records of plant and animal phenology exist for the northern hemisphere, few noteworthy records are available for the southern hemisphere. We present one of the first phenological records of fish migration for the southern hemisphere, and one of the only phenological records for the southwest Indian Ocean. The so-called ‘sardine run’ – an annual winter migration of sardines, northeast of their summer spawning grounds on the Agulhas Bank off the coast of Durban, South Africa – has been well documented in local newspapers given the importance placed on fishing and fishing-tourism in the region. An analysis of the first arrival dates of sardines reveals a 1.3 day per decade delay over the period 1946–2012. Although this phenological shift reveals a poor association with sea surface temperatures (SST), it coincides with a poleward shift in the position of the 21 °C mean annual SST isotherm – the threshold temperature for sardine populations. The timing of sardine arrivals near Durban corresponds closely with the number of mid-latitude cyclones passing over the Durban coastline during the months of April and May. The strength of the run is strongly associated with ENSO conditions. The complex suite of factors associated with this phenological shift poses challenges in accurately modelling the future trajectory for this migratory event.

Progressive delays in the timing of sardine migration in the southwest Indian Ocean

Phenological shifts represent one of the most robust bioindicators of climate change. While considerable multidecadal records of plant and animal phenology exist for the northern hemisphere, few noteworthy records are available for the southern hemisphere. We present one of the first phenological records of fish migration for the southern hemisphere, and one of the only phenological records for the southwest Indian Ocean. The so-called ‘sardine run’ – an annual winter migration of sardines, northeast of their summer spawning grounds on the Agulhas Bank off the coast of Durban, South Africa – has been well documented in local newspapers given the importance placed on fishing and fishing-tourism in the region. An analysis of the first arrival dates of sardines reveals a 1.3 day per decade delay over the period 1946–2012. Although this phenological shift reveals a poor association with sea surface temperatures (SST), it coincides with a poleward shift in the position of the 21 °C mean annual SST isotherm – the threshold temperature for sardine populations. The timing of sardine arrivals near Durban corresponds closely with the number of mid-latitude cyclones passing over the Durban coastline during the months of April and May. The strength of the run is strongly associated with ENSO conditions. The complex suite of factors associated with this phenological shift poses challenges in accurately modelling the future trajectory for this migratory event.