Developing Additive Systems of Biomass Equations for Robinia pseudoacacia L. in the Region of Loess Plateau of Western Shanxi Province, China

Does increasing forest age lead to greater trade-offs in ecosystem services? A study of a Robinia pseudoacacia artificial forest on the Loess Plateau, China

Artificial forest ecosystems offer various ecosystem services (ES) and help mitigate climate change effects. Trade-offs or synergies exist among ES in artificial forests. Although forest age influences ES and ecosystem processes, the long-term dynamics of trade-offs among ES in artificial forests and during vegetation restorations remain unclear, complicating vegetation and sustainable management. We studied a Robinia pseudoacacia plantation on the Loess Plateau, China, with a restoration time of 10-44 years. The entropy weight method was used to assess five ES (carbon sequestration, water conservation, soil conservation, understory plant diversity, and runoff and sediment reduction) and investigate how ES change with forest age. The root mean square deviation (RMSD) was used to quantify the trade-offs among ES, and redundancy analysis (RDA) analysis was used to identify the key factors influencing the ES and trade-offs. The results showed that (1) as forest age increased, ES scores initially increased and then decreased. The optimal range for ES values was observed during the middle-aged to mature stages of the forest. (2) Before reaching maturity, the planted forests primarily delivered services related to water conservation and runoff and sediment reduction. (3) In young forests, ES showed a synergistic relationship (RMSD = 0.06), whereas trade-offs occurred in forests at other ages. The largest trade-off was observed in middle-aged forests. (4) The ES pairs with the dominant trade-offs in planted forests differed at different forest age stages. The largest trade-off occurred between carbon sequestration and water conservation (RMSD = 0.28). RDA analysis showed that understory vegetation coverage had a positive correlation with all ES. The ES indicators that significantly (P < 0.001) affected the water‑carbon trade-off were tree carbon storage, soil organic carbon storage, soil total nitrogen, and soil total phosphorus. Thus, the water and carbon relationship must be balanced, and the key factors affecting ES trade-offs in forest management must be regulated to support ES multifunctionality.

Additive Root Biomass Equations for Betula platyphylla Suk. Plantations in Northeast China

Most of the forest biomass models that have been developed so far focus on the study of the aboveground biomass of forest trees and the prediction of belowground biomass remains obviously insufficient. Moreover, most of the existing studies on the estimation of the belowground biomass of trees have considered roots as a whole, ignoring the differences in composition and function of roots within different diameter classes. In this study, we measured the root biomass of birch plantation forests in northeastern China using extensive destructive sampling, in which we divided the root system into three parts: coarse, medium, and fine roots. We selected the best model base form from three common allometric biomass equations and determined the most appropriate error structure for the two sets of models using likelihood comparisons. The additive and disaggregated models were fitted using maximum likelihood with open-source software. We also added the site factor as a dummy variable into the two models. Finally, the competency of the two models was tested using ten-fold cross-validation. The results showed that both models could provide relatively accurate estimates of birch root biomass but that the disaggregated model performed slightly better than the additive model.

Productivity of Black Locust (Robinia pseudoacacia L.) Grown on a Varying Habitats in Southeastern Poland

This study investigated growth performances of black locust (Robinia pseudoacacia L.) tree species in various soil and agro-climatic conditions in Poland. Implementing of research was based on monoculture black locust stands in which it was possible to carry out dendrometric tests allowing us to learn about their volume. These stands were located on marginal soils. In the sample plots selected for the study, the parameters of stands (main and secondary) were determined, such as number and social structure of trees, average tree height, average diameter at breast height (DBH), and volume. The volume was determined with division into trunks and branches and wood thickness classes (0.0–1.0 cm, 1.1–5.0 cm, 5.1–10.0 cm and then every 5 cm). During the research, it was found that sunlight and moisture conditions mainly affect the volume. It has been noticed that the content of nutrients in the soil plays a minor role because black locust grows very well in poorly fertile soils, often subject to erosion processes. Black locust grows well on damp, shaded slopes with northern exposures. In such areas, the stand volume was the highest (353.8 m3 ha−1), exceeding the average volume of the remaining 35-year-old stands on sandy soils by 60%. Along with the increase in the age of stands, the share of trunk wood increased with the wood of branches. The share of wood up to 5.0 cm was small in older stands, at most a dozen or so percent. However, in young stands (4- and 8-year-old), the share of the thickness class up to 5 cm was even 65% of the stand volume. In 35-year-old stands, wood fractions of 15.1–20.0 cm were dominant. In the oldest, 64-year-old stand, over 30 cm thick wood constituted 44% of the stand volume. However, statistical analysis showed, with p = 0.1644, no differences existed between the thickness of the individual thickness classes.