[Characteristics and influence factors of rainfall redistribution in eight typical plantations in the loess area in West Shanxi, China]. / 晋西黄土区8ç§å ¸åž‹æž—åˆ†é™é›¨å†åˆ†é ç‰¹å¾ä¸Žå½±å“å› ç´ .

Aiming for clarifying the potential distribution characteristics of canopy rainfall partitioning of the loess area, we explored the process of rainfall partitioning across eight typical forest stands (Pinus tabuliformis forest, Robinia pseudoacacia forest, Platycladus orientalis forest, mixed forest of Robinia pseudoacacia-Pinus tabuliformis, mixed forest of Platycladus orientalis-Robinia pseudoacacia, Quercus wutaishanica forest, Populus davidiana forest, mixed forest of Quercus wutaishanica-Populus davidiana), and used boosted regression trees (BRT) to quantify the relative influences of stand structures and meteorological environment factors. We established multiple regression relationships according to the most influential factors extracted by BRT, and applied to the dataset of mining to verify the performance of the BRT-derived predictive model. The results showed that the percentages of throughfall (TF), stemflow (SF), and canopy interception (Ic) in total precipitation were 24.5%-95.1%, 0-13.6%, and 0.7%-55.7% among eight typical forest stands, respectively. For the individual rainfall threshold of TF, coniferous forest (3.06±1.21 mm) was significantly higher than broad-leaved forest (1.97±0.52 mm), but there was no significant difference between coniferous forest and broad-leaved mixed forest (3.01±0.98 mm). There was no significant difference in the individual rainfall threshold of SF among different composition stands. BRT analysis showed that stand structure factors accounted for a relatively small proportion for TF and SF, respectively. By contrast, stand structure factors dominated the Ic. Rainfall was the most important factor in determining TF and SF. Tree height was the most important factor in determining Ic, followed by rainfall, canopy area, diameter at breast height, and stand density. Compared with the general linear function and the power function, the prediction effect of BRT prediction model constructed here on TF and SF had been further improved, and the prediction of canopy interception still needed to explore. In conclusion, the BRT model could better quantitatively evaluate the effects of stand structure and meteorological environmental factors on rainfall partitioning components, and the performance of the BRT predictive model could satisfy and lay the foundation for the optimization strategy for stand configuration.

Water source of Robinia pseudoacacia and Platycladus orientalis plantations under different soil moisture conditions in the Loess Plateau of Western Shanxi, China.

Water is a key factor limiting plant growth in loess regions. Studying water use by different afforestation species under different water conditions is crucial to understand the drought resistance mechanisms of plants in arid and semi-arid regions. We analyzed water use at different depths by the afforestation species Robinia pseudoacacia and Platycladus orientalis under the drought treatment (100% no throughfall, DT) and the natural rainfall (control, CK) by stable isotope (δ18O, δ2H) technique and explored their drought adaptability. The results showed that R. pseudoacacia mainly absorbed soil water at 0-40 cm soil layer in the wet months (June and September), with a contribution rate of 68.0%±2.4%, and at four layers (0-10, 10-40, 40-60, and 60-120 cm) evenly in the dry months (July and August) in the CK. In contrast, P. orientalis mainly absorbed soil water at 0-40 cm layer in both the wet and dry months, with the contribution rate being 77.0%±2.4% and 57.4%±3.0%, respectively. In the DT, the water-use depths of R. pseudoacacia and P. orientalis tended to move downward with the decreases of soil water content. The water-use depths of R. pseudoacacia changed from 0-40 cm to 60-120 cm, while that of P. orientalis changed from 0-40 cm to the four layers mentioned evenly. R. pseudoacacia and P. orientalis could adjust water-use depths under different water conditions and showed strong drought adaptability, a feature of great significance for evaluating the stress resistance and stability of local plantations.