Nighttime transpiration of Populus euphratica during different phenophases

Evidence exists of nighttime transpiration and its potential impact on plant/water relations for species in a diversity of ecosystems. However, relevant data related to typical desert riparian forest species remains limited Accordingly, we measured sap flow velocity of Populus euphratica using the heat ratio method between 2012 and2014. Nocturnal stem sap flow was separated into nighttime and stem refilling using the ‘‘forecasted refilling''method. Nighttime transpiration was observed for each phenophase. The highest value was during the full foliation period but lowest during leaf expansion and defoliation periods. The contribution of nighttime transpiration to daytime transpiration was an average of 15% but this was comparatively higher during the defoliation period. Relationships between nighttime transpiration, vapor pressure deficits, and air temperatures were more closely associated than with wind speed in all phenophases. Moreover, we found that nighttime transpiration linearly correlated to vapour pressure deficit during the first and the full foliation periods, but nighttime transpiration showed exponential correlations to air temperatures during the same phenophases. Additionally, environmental drivers of transpiration were significantly different between nighttime and daytime(P \ 0.05). Driving forces behind nighttime transpiration were characterized by many factors, and integrated impacts between these multiple environmental factors were complex. Future studies should focus on these integrated impacts on nighttime transpiration, and the physiological mechanisms of nighttime transpiration should be investigated, given that this could also influence its occurrence and magnitude during different phenophases.

Impacts of climate warming on plants phenophases in China for the last 40 years

Based on plant phenology data from 26 stations of the Chinese Phenology Observation Network of the Chinese Academy of Sciences and the climate data, the change of plant phenophase in spring and the impact of climate warming on the plant phenophase in China for the last 40 years are analyzed. Furthermore, the geographical distribution models of phenophase in every decade are reconstructed, and the impact of climate warming on geographical distribution model of phenophase is studied as well. The results show that (i) the response of phenophase advance or delay to temperature change is nonlinear. Since the 1980s, at the same amplitude of temperature change, phenophase delay amplitude caused by temperature decrease is greater than phenophase advance amplitude caused by temperature increase; the rate of phenophase advance days decreases with temperature increase amplitude, and the rate of phenophase delay days increases with temperature decrease amplitude. (ii) The geographical distribution model between

Spatio-temporal responses of cropland phenophases to climate change in Northeast China

We investigated the responses of cropland phenophases to changes of agricultural thermal conditions in Northeast China using the SPOT-VGT Normalized Difference Vegetation Index （NDVI） ten-day-composed time-series data, observed crop phenophases and the climate data collected from 1990 to 2010. First, the phenological parameters, such as the dates of onset-of-growth, peak-of-growth and end-of-growth as well as the length of the growing season, were extracted from the smoothed NVDI time-series dataset and showed an obvious correlation with the observed crop phenophases, including the stages of seedling, heading, maturity and the length of the growth period. Secondly, the spatio-temporal trends of the major thermal conditions （the first date of ≥10℃, the first frost date, the length of the temperature-allowing growth period and the accumulated temperature （AT） of ≥10℃） in Northeast China were illustrated and analyzed over the past 20 years. Thirdly, we focused on the responses of cropland phenophases to the thermal conditions changes. The results showed that the onset-of-growth date had an obvious positive correlation with the first date of ≥10℃ （P 0.01）, especially in the northern part of the Songnen Plain, the eastern part of the Sanjiang Plain and the middle and eastern parts of Jilin Province. For the extracted length of growing season and the observed growth period, notable correlations were found in almost same regions （P 0.05）. However, there was no obvious correlation between the end-of-growth date and the first frost date in the study area. Opposite correlations were observed between the length of the growing season and the AT of ≥10℃. In the northern part of the Songnen Plain, the eastern part of the Sanjiang Plain and the middle part of Jilin and Liaoning Provinces, the positive correlation coefficients were higher than the critical value of 0.05, whereas the negative correlation coefficients reached a level of 0.55 （P 0.05） in the middle and southern parts of Heilongjiang Province and some parts of the Sanjiang Plain. This finding indicated that the crop growth periods were shortened because of the elevated temperature; in contrast, the extended growth period usually meant a crop transformation from early- or middle-maturing varieties into middle or late ones.

Differences in response of desert plants of different ecotypes to climate warming:a case study in Minqin, Northwest China

Globally climates are warming. How do desert plants of different ecotypes respond to the climate change？ This paper studied the differing responses to climate warming shown by desert plants of different ecotypes through analyzing the phenology and meteorological data of 22 desert plant species growing in Minqin Desert Bo- tanical Garden in Northwest China during the period 1974-2009. The results indicate： （1） The temperature in the study area has risen quickly since 1974, and plants＇ growing periods became longer. The spring phenology of mesophytes advanced, and the autumn phenology of xerophytes was delayed; （2） The starting dates of spring phenophase of mesophytes and xerophytes differed significantly and both showed an advancing trend; （3） The spring phenology of mesophytes advanced by more days than that of xerophytes, whereas the autumn phenology of mesophytes was delayed by less days than that of the xerophytes; and （4） Mesophytes are more sensitive than xerophytes to rising temperature in spring and falling temperature in autumn. These findings are of value in plant management and regional introduction of different species.

Phenological study of congeneric Myrcia species and Clethra scabra in wetland and drained habitats in a Montane Forest

Although important,phenological studies comparing congeneric species or the same species growing in different habitats are still scarce for the tropics.Herein,we integrate phylogeny,ecology and biometeorology to verify whether the phenophases of congeneric species Myrcia laruotteana and Myrcia amazonica or Clethra scabra differ when their populations inhabit wetland and drained habitats and to determine what abiotic factors affect the vegetative and reproductive phenophases of these species in distinct habitat patches.We collected data on phenological events of 80 trees for 1 year in Itacolomi State Park,Brazil,and related them to abiotic local factors.Contrary to our expectation,the phenophases of the congeneric species did not differ between habitats,but the reproductive phenophases of C.scabra did and was greater in drained soil.Phenophases of C.scabra were affected by the depth of the water table and maximum temperature in the wetland soil.Insolation,precipitation,maximum temperature and relative humidity influenced Myrcia and Clethra in the drained soil.The differences between C.scabra populations suggest that this species is phenotypically plastic and can present distinct phenophases depending on the habitat it inhabits.On the other hand,the congeneric Myrcia species may have similar phenophases in distinct habitats because of their shared similarities during their evolution.This study provides a better understanding of the ecology of these species and their adaptations to different abiotic conditions.Data of this nature are important in a changing world and can inform strategies for adaptive management.

Phenology of a tropical dry deciduous forest of Bhadra wildlife sanctuary,southern India

Introduction:This paper describes the leafing,flowering and fruiting phenology of canopy trees in the dry deciduous forest of Bhadra wildlife sanctuary from June 2004 to May 2006.Method:All the woody canopy individuals(>20 cm girth at breast height)were identified and tagged with a unique number along a transect of approximately 2 Km comprising 157 individuals of 22 species.Observations were made at monthly intervals from June 2004 to May 2006 for leafing,flowering and fruiting phenophases.Result:Leaf fall starts in September,with a peak in December and January.Leaf initiation begins in February,with a peak in April before the monsoon.Leaf expansion starts in February from pre-monsoon with a peak in May and July during the monsoon.Leaf senescence begins in September to November and peaks in January to March.Flower bud initiates in January with a peak in April and May,and pollination begins in April with a peak in May and July before the monsoon to onset of monsoon.Fruit bud initiates in May with a peak in September and October.Unripened fruit was observed in May with a peak in September and November.Fruit fall begins in November with a peak in March.Conclusion:Our results show that leafing and flowering activities occur in the summer or pre-monsoon.Fruiting patterns occur during the monsoon to post-monsoon season.Seasonality among various phenophases indicates that leaf senescence flower initiation and fruit fall have strong seasonality.