Non-structural carbohydrates (NSC) affect tree growth and survival when photosynthesis is impacted by climate change, such as seasonal drought and extreme precipitation. Nevertheless, it is still unclear whether Eucalyptus suffers growth limitation under natural conditions and if trees recover under artificial cultivation. In present study, we conducted a field control experiment to compare the NSC storage in Eucalyptus urophylla × Eucalyptus grandis trees on fertilization and dry-season irrigation to determine the variations of NSC under drought stress. The results indicated total soluble sugar (TSS) was the primary existing form of NSC. In spatial patterns, NSC concentration showed gradient differences from source organ to sink organ, and finally accumulated in root. The TSS concentration showed a decreased trend with height except leaf, while the trend of starch concentration was contrast. Surprisingly, fertilization and dry-season irrigation had not changed the carbon distribution among all tissues but reduced the TSS concentration in most organs. The fast-growing E. urophylla × E. grandis will consume the assimilates and carbohydrates of storage organs, but maintains the NSC concentration at a certain threshold. Our results help to comprehend the NSC allocation and improve the productivity of E. urophylla × E. grandis plantations in seasonal arid areas.

Leaves are essential for photosynthesis and gas exchange, and their growth characteristics are the key factors that influence the carbon budget. Eucalyptus is widely afforested in south China due to its fast-growing and high-yield features. Water and fertilizer are the main factors affecting plant growth. Studying the effects of different water and fertilizer treatments on the growth of Eucalyptus leaves under seasonal drought could further elucidate the optimal additions for Eucalyptus productivity. In this study, we investigated the leaf area, length, width, perimeter, and expansion rates of the commercial species E. urophylla × E. grandis under different treatments of dry season irrigation and fertilizer application to elucidate the growth dynamics of the leaves. The results indicated that both dry season irrigation and fertilizer could affect whole leaf expansion. Leaf area was largest when water and fertilizer were added at the same time. In this experiment, we found that fertilization had a significant effect on the leaf shape index of the Eucalyptus leaves. The leaf shape index was larger with the fertilizer treatment, which made the leaves slender. Dry season irrigation shorten the peak period of leaf growth and increase the leaf area. Our results help to further understand the mechanism of Eucalyptus productivity under seasonal drought and provide theoretical support for Eucalyptus production.

Posted facial expressions on social networks have been used as a gauge to assess the emotional perceptions of urban forest visitors. This approach may be limited by the randomness of visitor numbers and park locations, which may not be accounted for by the range of data in local tree inventories. Spatial interpolation can be used to predict stand characteristics and detect their relationship with posted facial expressions. Shaoguan was used as the study area where a tree inventory was used to extract data from 74 forest stands (each sized 30 m × 20 m), in which the range was increased by interpolating the stand characteristics of another 12 urban forest parks. Visitors smiled more in parks in regions with a high population or a large built-up area, where trees had strong trunks and dense canopies. People who displayed sad faces were more likely to visit parks located in regions of hilly mountains or farmlands, where soils had a greater total nitrogen concentration and organic matter. Our study illustrates a successful case in using data from a local tree inventory to predict stand characteristics of forest parks that attracted frequent visits.