Effects of soil water decline on diurnal and seasonal variations in sap flux density for differently aged Japanese cypress (Chamaecyparis obtusa) trees

The effects of soil drought on transpiration are often neglected when predicting transpiration for forests in humid regions under the influence of the Asian monsoon. These effects have indeed been neglected for Japanese cypress, Chamaecyparis obtusa, a major plantation species in Japan and the surrounding area, probably because previous studies have reported no clear effects of soil drought on transpiration for Japanese cypress forests. However, a few studies have reported an apparent reduction in transpiration with soil drought for young Japanese cypress forests. It remains unclear whether such a reduction in transpiration is limited to young Japanese cypress forests or if it is not uncommon for mature Japanese cypress forests, which occupy a large area in Japan. To clarify this point, we conducted sap flux measurements in a year with soil drought on three differently aged Japanese cypress stands including mature (43 years old) and relatively young (23 and 26 years old) trees. In a diurnal time scale, a cross correlation analysis of sap flux density (Fd) and vapor pressure deficit (VPD) showed that the time lags between Fd and VPD were 1-3 h in dry soil conditions. These were larger than those of wet soil conditions (<1 h) for all sample trees. Fd at a given VPD in dry soil conditions was smaller than that in wet soil conditions for all sample trees; a 28%–63% reduction in the rate of change in Fd was observed under dry soil conditions. Because our results were obtained when the non-exceedance probability of recorded monthly precipitation was 9%–18%, the results suggest the need to consider the effects of soil drought more extensively. Those effects should be considered for not only relatively young but also mature Japanese cypress when predicting diurnal and seasonal patterns of transpiration in years with soil drought, and when predicting inter-annual patterns of transpiration for Japanese cypress despite humid temperate climate. 

Floral morphometric analysis of Prosopis affinis Spreng. (Fabaceae) suggests flexibility of the reproductive system in isolated populations within the Brazilian Pampa

Genetic diversity in European beech (Fagus sylvatica L.) seed stands in the Romanian Carpathians

In Romania, European beech (Fagus sylvatica L.) is the most important broadleaved tree species. The goal of the present study was to determine the genetic diversity and differentiation in and between natural beech populations from the Romanian Carpathians and the transmission of the genetic diversity to the next generation. The populations analyzed were registered as seed stands. Genetic analysis was based on ten nuclear microsatellites. The highest amount of genetic variation was within populations, whereas genetic differentiation between populations was low. In the adult populations the mean number of alleles per locus varied from 8.0 to 10.9, the effective number from 8.3 to 9.6. Heterozygosity ranged from 0.637 to 0.750 with the mean of 0.681(±0.018). The overall genetic differentiation FST between populations averaged 0.014. Geographic patterns within this region were not detected. Regenerating these stands naturally has not implied a reduction in the genetic variation in the following generation. Allelic richness, genetic diversity and heterozygosity in adult stands and their natural regeneration is not significantly different. Inbreeding effects were not observed (F between -0.032 and 0.061). The results complete the knowledge on genetic variation of beech in Romania and give insides into the genetic diversity of beech seed stands. They can be helpful too for the delineation of provenance regions in the Romanian Carpathians.

Adaptive genetic potential of European silver fir in Romania in the context of climate change

Five provenance tests with twenty-six European silver fir autochthonous populations were used in order to assess the response of populations to climate change. Height growth and diameter at breast height of trees at age 31 years were considered as response variables and eight climate variables as predictors. Climatic variables for the trial sites and for origin location of provenances were calculated from 1961 to 2010. The experiments revealed a large genetic variability within species level and a plastic response to climate change, which certainly has a genetic basis. The transfer to warmer climate has resulted in an increase of the provenances growth, in the trial sites situated on the lower vegetation layer. But growth is significantly influenced by mean annual temperature and annual precipitation of planting site and also by the differences in mean annual temperature, annual precipitation, monthly mean temperature in July and July precipitation between provenance site and test site. These are the climatic factors which should be associated with risk in case of the transfer of forest reproductive materials. The provenance origin should be especially considered if the species will be planted outside of its current climate optimum. The best provenances in terms of total height and diameter at 1.30 m came from origin climate close to site climate, small transfer distances. Based on growth response functions and RCP4.5 scenario, we could project the shifts in species distribution for 2050s and 2100s and identify vulnerable populations.