Tea Plantation Frost Damage Early Warning Using a Two-Fold Method for Temperature Prediction

As the source and main producing area of tea in the world, China has formed unique tea culture, and achievedremarkable economic benefits. However, frequent meteorological disasters, particularly low temperature frostdamage in late spring has seriously threatened the growth status of tea trees and caused quality and yield reduction of tea industry. Thus, timely and accurate early warning of frost damage occurrence in specific tea garden isvery important for tea plantation management and economic values. Aiming at the problems existing in currentmeteorological disaster forecasting methods, such as difficulty in obtaining massive meteorological data, largeamount of calculation for predicted models and incomplete information on frost damage occurrence, this paperproposed a two-fold algorithm for short-term and real-time prediction of temperature using field environmentaldata, and temperature trend results from a nearest local weather station for accurate frost damage occurrence leveldetermination, so as to achieve a specific tea garden frost damage occurrence prediction in a microclimate. Timeseries meteorological data collected from a small weather station was used for testing and parameterization of atwo-fold method, and another dataset acquired from Tea Experimental Base of Zhejiang University was furtherused to validate the capability of a two-fold model for frost damage forecasting. Results showed that comparedwith the results of autoregressive integrated moving average (ARIMA) and multiple linear regression (MLR),the proposed two-fold method using a second order Furrier fitting model and a K-Nearest Neighbor model(K = 3) with three days historical temperature data exhibited excellent accuracy for frost damage occurrence prediction on consideration of both model accuracy and computation (98.46% forecasted duration of frost damage,and 95.38% for forecasted temperature at the onset time). For field test in a tea garden, the proposed methodaccurately predicted three times frost damage occurrences, including onset time, duration and occurrence level.These results suggested the newly-proposed two-fold method was suitable for tea plantation frost damage occurrence forecasting.

Threats and Avoidance Measures of Frost Damage of‘Shushanggan’Apricot in the Ili River Valley

[Objectives]To explore the threat factors of frost damage to‘Shushanggan’Apricot in the Ili River Valley,and to provide measures for avoiding frost damage.[Methods]Based on the meteorological data of the Ili River Valley counties and cities during the 12 years from 2010 to 2021 and using the critical low temperature of‘Shushanggan’Apricot as the main factor,we comprehensively analyzed the threats of low temperature in winter in January and late frost in April in spring in the Ili River Valley.[Results]During the 12 years,there were 4 years of low temperature below the critical(-26—-28℃)of‘Shushanggan’Apricot in the Ili River Valley counties and cities in January,accounting for 33.3%,and a total of 59 d.The frequency of occurrence was:Nilka County>Qapqal County>Yining City>Gongliu County>Huocheng County>Khorgos City>Yining County>Tekes County>Xinyuan County.In April,there were 9 years with a low temperature below the critical temperature(-0.6℃)flowering and fruit setting of‘Shushanggan’Apricot,accounting for 75%,and a total of 134 d.The frequency of occurrence was:Nilka County>Tekes County>Gongliu County>Yining County>Huocheng County>Khorgos City>Xinyuan County>Yining City>Qapqal County.The low temperature threats of‘Shushanggan’Apricot suitable cultivation areas were ranked as follows:Nilka County>Gongliu County>Tekes County>Qapqal County>Huocheng County>Yining City>Yining County>Khorgos City>Xinyuan County.Combined with the observation and survey of frost damage on the spot,we comprehensively analyzed and evaluated the cultivation area of‘Shushanggan’Apricot in the Ili River Valley:three counties(Nilka County,Gongliu County,and Tekes County)in the eastern region,except Xinyuan County,suffered frequent late frost damage,are suitable areas for the cultivation of‘Shushanggan’Apricot;three counties and two cities in the western region(Qapqal County,Huocheng County,Yining City,Yining County,Khorgos City)and Xinyuan County in the eastern region are suitable areas for‘Shushanggan’Apricot.The inversion zone at an altitude of 820-1100 in the valley is the superior area for‘Shushanggan’Apricot.[Conclusions]We explored the suitable areas in the origin area of‘Shushanggan’Apricot,and came up with measures to avoid frost damage,to provide a reference for the development of‘Shushanggan’Apricot.

Contrast in vulnerability to freezing-induced xylem embolism contributes to divergence in spring phenology between diffuse-and ring-porous temperate trees

Background:The spring phenology and growth strategy of temperate tree species can be strongly linked to their sensitivity to frosts,which deserve more profound investigations under the background of climate warming particularly considering the advancement of spring phenology as well as the increase in frequency and intensity of spring cold waves.Methods:Spring phenologies,stem radial growth characteristics,frost sensitivity of leaves and stem hydraulic systems were studied in five diffuse-porous and five ring-porous temperate tree species under a common garden condition.Results:The results showed that the spring leaf phenology of the diffuse-porous species was one to two weeks earlier than that of the ring-porous species.The ring-porous species had significantly higher stem hydraulic conductivity than the diffuse-porous species(1.81 and 0.95 kg·m^(-1)·s^(-1)·MPa^(-1),P<0.05)but were more vulnerable to freeze-thaw induced xylem embolism than the latter.After a simulated freeze-thaw event,the average percentage loss of hydraulic conductivity in the current year shoots increased from 26.0%(native embolism)to 86.7%in the ring-porous species,while it only increased from 21.3%to 38.3%in the diffuse-porous species.The spring phenology was clearly correlated with vulnerability to freeze-thaw induced embolism,with the more vulnerable ring-porous species exhibited substantially delayed phenology to reduce risks of catastrophic hydraulic dysfunction during spring frosts.Nevertheless,ring-porous species can offset the postponed onset of growth and gained even higher annual growth due to significantly higher hydraulic efficiency and leaf gas exchange rates.Conclusions:Contrasts between ring-porous and diffuse-porous species in resistance to freeze-thaw induced embolism suggest that they face different selective pressures from early spring frosts,which may at least be partially responsible for their divergence in spring phenology and growth strategy and can potentially lead to different responses to climate regime shifts.

Sprinkler irrigation system for tea frost protection and the application effect

A sprinkler irrigation system was designed and applied for a tea field to achieve frost protection through latent heat release when water turning into ice.Frost protection effects during night were tested at different irrigation application rates by monitoring air temperature around tea canopy(Tc).Temperature sensors were arranged at different distances from the sprinkler.The preliminary results showed that,when the sprinkler system worked continuously at the application rate of 2-4 mm/h before sunrise,tea canopy was covered with ice and Tc remained around 0℃,preventing tea plants from frost damage.But no more temperature rise was obviously observed at the application rates above 4 mm/h,which means less cost effectiveness.The system was stopped after sunrise when background air temperature rose back to 0℃and Tc increased by 2.2℃in one hour,while Tc of non-irrigated area increased by 4.8℃,which might cause thawing injuries to tea plants.The leaf surface temperature was lower than Tc,and the difference between the leaf surface temperature and Tc decreased with the increase of application rate.Therefore,the sprinkler irrigation system could achieve tea frost protection,and the recommended application rate was 2-4 mm/h for better protection effect.The system should keep running throughout frost night till half an hour after sunrise.The start and stop of the sprinkler irrigation system should be controlled based on Tc.

Tea leaf’s microstructure and ultrastructure response to low temperature in indicating critical damage temperature

To find out the critical damage temperature of tea leaf,a new method of subzero treatment was provided by fitting the air temperature data from six heavy frost events.Furthermore,the study explored the characteristics of Fuding Dabai tea plant response to low temperature stress of 2,0,
2,
4,
8,
10 and
15
C by observing the microstructure and ultrastructure changes of the leaves.All samples were collected in an ambient temperature of 8.6
C which served as control.Scanning electron microscopy(SEM)and transmission electron microscopy(TEM)were used to observe the microstructure and ultrastructure of stomata and mesophyll.SEM observation results indicated that stomata of tea leaves have an obvious low temperature stress when the temperature was lower than
2
C.The extent of opening of the stomata increased and enhanced guard cell protection of tea leaves against cold injury.However,dehydration,shrinkage and deformation of cells occurred as the temperature decreased from
2
C to
15
C.TEM observations showed that the cell nucleus,cell walls,chloroplasts and mitochondria all had normal structure at a temperature of 8.6
C where the membrane and granum lamella were clearly visible.As the temperature decreased to
2
C,the membrane system of tea leaf was the first to be damaged and the cell walls became fuzzy.Therefore,the leaf microstructure and ultrastructure showed obvious changes at
2
C,which might define the critical damage temperature for freeze damage of Fuding Dabai tea.Control strategy based this critical damage temperature is useful for wind machine frost protection in tea fields within the Yangtze River region.

Digital surface model applied to unmanned aerial vehicle based photogrammetry to assess potential biotic or abiotic effects on grapevine canopies

Accurate data acquisition and analysis to obtain crop canopy information are critical steps to understand plant growth dynamics and to assess the potential impacts of biotic or abiotic stresses on plant development.A versatile and easy to use monitoring system will allow researchers and growers to improve the follow-up management strategies within farms once potential problems have been detected.This study reviewed existing remote sensing platforms and relevant information applied to crops and specifically grapevines to equip a simple Unmanned Aerial Vehicle(UAV)using a visible high definition RGB camera.The objective of the proposed Unmanned Aerial System(UAS)was to implement a Digital Surface Model(DSM)in order to obtain accurate information about the affected or missing grapevines that can be attributed to potential biotic or abiotic stress effects.The analysis process started with a three-dimensional(3D)reconstruction from the RGB images collected from grapevines using the UAS and the Structure from Motion(SfM)technique to obtain the DSM applied on a per-plant basis.Then,the DSM was expressed as greyscale images according to the halftone technique to finally extract the information of affected and missing grapevines using computer vision algorithms based on canopy cover measurement and classification.To validate the automated method proposed,each grapevine row was visually inspected within the study area.The inspection was then compared to the digital assessment using the proposed UAS in order to validate calculations of affected and missing grapevines for the whole studied vineyard.Results showed that the percentage of affected and missing grapevines was 9.5%and 7.3%,respectively from the area studied.Therefore,for this specific study,the abiotic stress that affected the experimental vineyard(frost)impacted a total of 16.8%of plants.This study provided a new method for automatically surveying affected or missing grapevines in the field and an evaluation tool for plant growth conditions,which can be implemented for other uses such as canopy management,irrigation scheduling and other precision agricultural applications.