施肥对柚木幼林生长及林下植被的影响

为探究施肥对柚木（Tectona grandis L. f.）幼林生长及林下植被多样性的影响，以广西4年生的柚木人工林为研究对象，采用随机区组试验设计，开展不同肥种配比组合试验（F1，0.5 kg氮磷钾复合肥+1.0 kg钙肥+1.0 kg硫酸镁肥；F2，1.0 kg氮磷钾复合肥+0.5 kg钙肥+0.5 kg硫酸镁肥；F3，1.0 kg氮磷钾复合肥+0.5 kg硫酸镁肥；F4，1.0 kg氮磷钾复合肥+0.5 kg钙镁磷肥；CK，不施肥）。结果表明：施肥显著加快了柚木树高、胸径和单株材积的生长，各指标年均增量分别比不施肥（CK）提高了0.13~0.32 m、0.17~0.26 cm和4.35~9.63 dm³，其中F3配比组合处理生长增量最大，且胸径和材积生长率比CK显著增加了10.35%、10.55%。幼林林下植物相对丰富，植被种类涉及25科39属42种，其中菊科（Compositae）与禾本科（Gramineae）植物为主要优势种。不同处理间林下植被物种Shannon-Wiener指数（H′）、Simpson指数（D）和Pielou均匀度指数（J_sw）差异显著（P<0.05），F1、F3处理的3个物种指数显著高于CK，而各处理Gleason物种丰富度指数（D_g）差异不明显，不同处理间生长及林下植被多样性等12个指标综合评价得分由高到低依次为F3、F1、F4、F2、CK。4年生柚木幼林合理施肥，可以促进林木生长，还可提高林下物种丰富度和多样性；1.0 kg氮磷钾复合肥和0.5 kg硫酸镁肥的低投入配方施肥，更有利于促进柚木人工林生长和群落的稳定。

Effects of Fertilizing on Trees Growth and Understory Vegetation of Young Teak Plantation

To investigate the effects of fertilization on teak growth and understory vegetation diversity， the four-year-old teak Tectona grandis L. f. plantation in Guangxi was studied by randomized block design and carried out different kinds of fertilizer treatment respectively（included F1： 0.5 kg NPK complex fertilizer， 1.0 kg calcium fertilizer and 1.0 kg MgSO₄ fertilizer； F2： 1.0kg NPK complex fertilizer， 0.5 kg calcium fertilizer and 0.5 kg MgSO₄ fertilizer； F3：1.0 kg NPK complex fertilizer and 0.5 kg MgSO₄ fertilizer； F4： 1.0 kg NPK complex fertilizer； CK： no fertilization）. The results showed that fertilization significantly accelerated growth of teak tree height， diameter at breast height and volume. Compared with control， the average annual increment of H， D_BH and V increased 0.13-0.32 m， 0.17-0.26 cm and 4.35-9.63 dm³， respectively. The growth increment of F3 was the largest， and the growth rate of D_BH and V promoted significantly by 10.35% and 10.55% than CK. Understory vegetation types of young teak plantation were relatively abundant and involved 25 families， 39 genera and 42 species， among which Compositae and Gramineae were the main dominant species. There were significant distinctions in Shannon-Wiener index（H′）， Simpson index（D） and Pielou evenness index（J_sw） （P<0.05） and these indexes of F1 and F3 treatments were significantly higher than CK， but the Gleason species richness index（D_g） was no significant（P>0.05） between five treatments. The comprehensive evaluation scores of 12 indexes that included tree growth and understory were F3，F1，F4，F2，CK in turn. The rational fertilization of 4-year-old young teak plantation could promote the growth of trees and increase the richness and diversity of understory. The low-input application of 1.0 kg NPK fertilizer and 0.5 kg MgSO₄ fertilizer in young teak plantation is more beneficial to the growth and community stability.