Reduced diurnal temperature range mitigates drought impacts on larch tree growth in North China.

Forests are facing climate changes such as warmer temperatures, accelerated snowmelt, increased drought, as well as changing diurnal temperature ranges (DTR) and cloud cover regimes. How tree growth is influenced by the changes in daily to monthly temperatures and its associations with droughts has been extensively investigated, however, few studies have focused on how changes in sub-daily temperatures i.e., DTR, influence tree growth during drought events. Here, we used a network of Larix principis-rupprechtii tree-ring data from 1989 to 2018, covering most of the distribution of planted larch across North China, to investigate how DTR, cloud cover and their interactions influence the relationship between drought stress and tree growth. DTR showed a negative correlation with larch growth in 95 % of sites (rmean = -0.30, significant in 42 % of sites). Cloud cover was positively correlated with growth in 87 % of sites (rmean = 0.13, significant in 5 % of sites). Enhanced tree growth was found at lower DTR in the absence of severe drought. Our findings highlight that in the absence of severe droughts, reduced DTR benefits tree growth, while increased cloud cover tended to benefit tree growth only during severe drought periods. Given how DTR influences drought impacts on tree growth, net tree growth was found to be larger in regions with smaller DTR.

Pyrene-porphyrin based ratiometric fluorescent sensor array for discrimination of glycosaminoglycans.

Accurate discrimination of common glycosaminoglycans (GAGs) before they are used in clinics is of great importance. Herein, a ratiometric sensor array Py-PP for discrimination of GAGs was constructed using three pyrene-porphyrin supramolecular complexes termed Py-PP1, Py-PP2 and Py-PP4. These complexes were readily synthesized by mixing pyrene-1-butyric acid (Py) and porphyrins PP1, PP2 and PP4 respectively. In the presence GAGs, the effective FRET from Py to porphyrin in the complex was influenced as a result of the competitive binding interactions between porphyrin and GAG. Controlled by the structural differences in the three porphyrins, complexes Py-PP1, Py-PP2 and Py-PP4 were determined to be cross-responsive towards tested GAGs including Hep, HA, Chs and DS. Distinctive fluorescence patterns were successfully generated for each GAG by the sensor array. The Py-PP sensor array was found to be powerful for discrimination of GAGs in both PBS and 5% serum media. Moreover, Py-PP was also successfully applied for reliable differentiation of Hep from other biological interferences and detection of trace GAG contaminants (0.1%, wt%) in Hep with 100% accuracy.

Porphyrin-GO Nanocomposites Based NIR Fluorescent Sensor Array for Heparin Sensing and Quality Control.

Heparin (Hep), widely used in clinics as an anticoagulant drug, has high degrees of heterogeneity and shares a similar disaccharide repeating unit with its GAG analogues. The development of reliable and convenient methods to discriminate Hep from its GAG analogues and detect trace GAG contaminants in Hep is meaningful for safe usage of Hep in clinics. Herein, five porphyrin-GO nanocomposites denoted as PP1-GO, PP2a-GO, PP2b-GO, PP3-GO, and PP4-GO were synthesized by assembling corresponding positively charged porphyrins onto the surface of GO. Controlled by a different number and position of the 4-N-methyl-pyridyl groups substituted at the porphyrins, these nanocomposites were determined to be cross-reactive toward Hep and other three commonly used GAGs including Chs, HA, and DS. A NIR sensor array PP-GO was thus constructed using these nanocomposites for GAGs discrimination and Hep quality control through pattern-based recognition. HCA and LDA calculated results indicated that PP-GO was powerful for discrimination of Hep and its GAG analogues in both PBS and even 10% serum media. Moreover, the PP-GO sensor array was successfully applied for the reliable discrimination of trace GAG contaminants in Hep with 100% accuracy.

Snowmelt and early to mid-growing season water availability augment tree growth during rapid warming in southern Asian boreal forests.

Boreal forests are facing profound changes in their growth environment, including warming-induced water deficits, extended growing seasons, accelerated snowmelt, and permafrost thaw. The influence of warming on trees varies regionally, but in most boreal forests studied to date, tree growth has been found to be negatively affected by increasing temperatures. Here, we used a network of Pinus sylvestris tree-ring collections spanning a wide climate gradient the southern end of the boreal forest in Asia to assess their response to climate change for the period 1958-2014. Contrary to findings in other boreal regions, we found that previously negative effects of temperature on tree growth turned positive in the northern portion of the study network after the onset of rapid warming. Trees in the drier portion did not show this reversal in their climatic response during the period of rapid warming. Abundant water availability during the growing season, particularly in the early to mid-growing season (May-July), is key to the reversal of tree sensitivity to climate. Advancement in the onset of growth appears to allow trees to take advantage of snowmelt water, such that tree growth increases with increasing temperatures during the rapidly warming period. The region's monsoonal climate delivers limited precipitation during the early growing season, and thus snowmelt likely covers the water deficit so trees are less stressed from the onset of earlier growth. Our results indicate that the growth response of P. sylvestris to increasing temperatures strongly related to increased early season water availability. Hence, boreal forests with sufficient water available during crucial parts of the growing season might be more able to withstand or even increase growth during periods of rising temperatures. We suspect that other regions of the boreal forest may be affected by similar dynamics.