[Response of understory species distribution of Robinia pseudoacacia plantation to environmental factors in loess hilly region, China.] / é»„åœŸä¸˜é™µåŒºåˆºæ§ç¾¤è½æž—ä¸‹ç‰©ç§åˆ†å¸ƒå¯¹çŽ¯å¢ƒå› å­çš„å“åº”.

We explored the distribution characteristics and influencing factors of understory species in Robinia pseudoacacia plantation in Wuqi, Ansai, Mizhi, Yichuan and other places, in combination with niche breadth, soil, altitude and other environmental factors. We analyzed the response mechanism of species distribution to environmental factor to provide a scientific basis for the mana-gement of R. pseudoacacia plantation in loess hilly region. The results showed that the broadly distributed understory species in R. pseudoacacia plantation were Setaria viridis, Heteropappus altaicus, Artemisia scoparia, Poa sphondylodes, Artemisia leucophylla, Ixeris sonchifolia, and Incarvillea sinensis. With the increasing rehabilitationage, the dominant understory species distribution followed the order: Artemisia capillaries → P. sphondylodes → A. scoparia → others (Rubia cordifolia, Rosa rubus and so on) → A. leucophylla → S. viridis. Results from principal component analysis showed that soil total phosphorus (25.6%), altitude (20.3%) and soil total nitrogen (19.3%) were the key factors influencing understory species distribution in R. pseudoacacia plantation. Soil organic carbon content, soil total nitrogen content, soil total phosphorus content, soil water content and the number of understory species distribution in R. pseudoacacia plantation were generally positively correlated with the degree of correlation varying across different species. There was no correlation between the slope aspect and the understory species distribution in R. pseudoacacia plantation. In conclusion, topography and soil factors played important roles in driving understory species distribution. The steeper the slope, the higher the altitude, the fewer understory species in R. pseudoacacia plantation. Understory species distribution was mainly affected by soil total phosphorus content and altitude. The understory species distribution reflected the differences of soil nutrient status, which had a certain guiding role in the management of R. pseudoacacia plantation.

[Stoichiometric characteristics of Artemisia sacrorum communities under different site conditions and their correlation with soil nutrients]. / ä¸åŒç«‹åœ°é“æ†è’¿åŒ–å­¦è®¡é‡ç‰¹å¾åŠå ¶ä¸ŽåœŸå£¤å »åˆ†çš„å ³ç³».

We explored the stoichiometric characteristic of Artemisia sacrorum communities and its correlation with soil characters by considering the aspect and slope position, and variation of soil nutrient in Yangqingchuan catchment of Wuqi. Our results showed that total carbon, total nitrogen, total phosphorus contents and C:N ratio in A. sacrorum (both shoot and root) in the top of hillock>sunny slope>semi-shady slope>shady slope. The C:P ratio in shoot and the N:P ratio in root decreased consistently. The N:P ratio in shoot and the C:P ratio in root decreased first and then increased. While the total nitrogen and total phosphorus in shoot, and the organic carbon in root increased first and then decreased with the decreases of slope position, the C:N ratio and N:P ratio in shoot decreased first and then increased. The stoichiometric characteristic of A. sacrorum communities was positively correlated with the soil stoichiometric characteristics. However, the C:N ratio, C:P ratio and N:P ratio of A. sacrorum and the total phosphorus of root were negatively correlated to corresponding soil indices. The correlation between shoot nutrition and soil was greater than that between soil and root nutrition. In conclusion, middle position of shady slope was optimal for the growth of A. sacrorum. The stoichiometric characteristics of plants were significantly correlated with soil nutrient condition. Aspect and slope position had a significant effect on the stoichiometric cha-racteristics of A. sacrorum community and soil. Proper A. sacrorum community could help restore soil nutrition.