δ13C and Water Use Efficiency in the Glucose of Annual Pine Tree Rings as Ecological Indicators of the Forests in the Most Industrialized Part of Poland

Environmental Factors at Different Canopy Heights Had Significant Effects on Leaf Water-Use Efficiency in Cold-Temperate Larch Forest

It is of great significance to study short-term water-use efficiency (WUEs) at different canopy heights for accurately evaluating the adaptability of cold-temperate larch (Larix gmelinii) forest to climate change. The stable isotope method combining data of gradient meteorology, photosynthetic properties and leaf structure were used to assess the influence of different canopy heights on short-term water-use efficiency (WUEs) in larch forests in the northern Da Hinggan Mountains. The results show that: (1) The rank of leaf WUEs at different canopy heights was upper canopy > middle canopy > lower canopy. The leaf WUEs in upper canopy was significantly higher than those in the middle and lower canopy (p < 0.01), and no significant difference was found between the middle and lower canopy (p > 0.05). (2) The environmental factors, the photosynthetic characteristics, the specific leaf weight (LMA) and stomatal density (SD) had significant impact (p < 0.05) on leaf WUEs at different canopy heights of larch forest. (3) The results of the weighted random forest analysis show that the main factor affecting WUEs in larch forests at different canopy heights was vapor pressure deficit (VPD), followed by relative humidity (RH) and net photosynthetic rate (Pn), while LMA and SD made relatively small contributions. This indicates that the variation of leaf WUEs at different canopy heights is mainly due to environmental factors. Our results highlight that the difference of environmental factors at different canopy heights should be considered in the future study of leaf WUE. Our results contribute to a better understanding of water utilization strategies and carbohydrate relations in the boreal forest ecosystems, which is of great significance for improving the sustainable management measures and strategies of boreal forest resources.

Stable carbon isotope as a signal index for monitoring grassland degradation

Grassland degradation due to overgrazing is common in many areas of the world. This study analyzed the potential of the stable carbon isotope (δ¹³C) value as a structural microcosmic index to monitor processes of grassland degradation. The δ¹³C values of plant leaves, roots and soils in non-grazed (NG) and over-grazed (OG) grassland were measured from samples collected from the seven types of grassland in China. We found that the leaf δ¹³C values of palatable species (δ¹³C_leaf) and root δ¹³C values (δ¹³C_root) in OG grasslands were reduced compared with those from NG grasslands. Furthermore, the δ¹³C_leaf and δ¹³C_soil were positive correlation with elevation and latitude, δ¹³C_root was negative correlation with them at high altitude (3000~5000m), and δ¹³C_root and δ¹³C_soil were negative correlation with them at low altitude (0~2000m), respectively. Consequently, tracing of the δ¹³C variations in grassland ecosystem can provide a powerful tool to evaluate the degree of grassland degradation.

The Impact of Climate, Sulfur Dioxide, and Industrial Dust on δ18O and δ13C in Glucose from Pine Tree Rings Growing in an Industrialized Area in the Southern Part of Poland

The mass spectrometric analysis of the impact of sulfur dioxide and dust emission on carbon and oxygen stable isotopic compositions of glucose hydrolysed from α-cellulose samples extracted from Scots pine growing in the vicinity of "Huta Katowice" steelworks was the main aim of this study. The annual rings covered the time span from 1975 to 2012 AD. The relationships between climatic conditions, sulfur dioxide, and industrial dust emission and oxygen and carbon isotopic compositions were analyzed using correlation function methods. This study shows the first analysis of carbon and oxygen stable isotopes in glucose as the bio-indicators of CO₂, sulfur dioxide, and industrial dust emission. The anticoincidence trend of δ¹⁸O and δ¹³C and dust and sulfur dioxide confirms that the decreases of dust and sulfur dioxide industrial emission increase δ¹⁸O and δ¹³C values in glucose.