退化柞蚕林封育对枯落物和表层土壤持水效能的影响

柞蚕林是辽东山区退化最严重的森林类型之一,因多年反复刈割导致生长逐渐衰退、更新能力下降,局部出现空地甚至土壤开始砂化,涵养水源和保持水土等生态功能明显降低。以辽东山区的退化柞蚕林为研究对象,分析了在封育9、12、21a后森林的枯落物及表层土壤持水效能。结果表明:退化柞蚕林经过封育恢复后,封育恢复时间越长,林地枯落物累积量增加的越显著,枯落物持水能力和有效拦蓄降雨能力提高也越明显。对照(未封育)、封育9、12、21a柞蚕林枯落物储量分别为3.69、7.92、8.41 t/hm~2和8.74 t/hm~2;最大持水量分别为6.23、14.71、15.81 t/hm~2和17.18 t/hm~2,有效拦蓄量分别为4.78、10.87、11.70、12.78 t/hm~2。枯落物持水量与浸水时间存在显著的相关关系(P0.001),自然对数模型模拟拟合效果最好(R~20.9)。退化柞蚕林经过封育恢复后,表层土壤水文物理性质的改善随着封育恢复时间的增加而越来越明显,封育9、12和21年柞蚕林表层土壤容重分别比对照退化柞蚕林降低了5.51%、12.60%、17.32%,毛管持水量分别增加了7.01%、28.98%、54.83%,非毛管持水量分别增加了46.14%、126.19%、187.19%。本研究结果说明退化柞蚕林封育能够通过提高其林地枯落物和改善土壤物理性质,增加表层土壤持水效能,对恢复和改善退化柞蚕林地的生态环境、恢复森林生产力具有重要作用。

Effects of enclosure and recovery for degraded Tussah-feeding oak forests on litter and surface soil water holding capacity characteristics

Tussah-feeding oak forests (here after referred to as TF oak forests) are seriously degraded forests in the mountainous areas of Eastern Liaoning Province. Owing to repeated cutting every year, the trees grow slowly and their ability to regenerate is markedly decreased. When open spaces appear, the soil begins to become sandy, which causes a decline in ecosystem services such as water storage and soil conservation. In this study, the water holding capacity of the litter and surface soil were investigated in a degraded TF oak forest after 9, 12, and 21 years of enclosure to facilitate recovery. In addition, the degraded TF oak forest was studied to identify the effects of enclosure and recovery time on the water holding capacity of litter and surface soil, using the spatial sequence as opposed to the time succession sequence. Litter in degraded TF oak forests increased significantly after enclosure, with more litter accumulating with increased enclosure time. Litter accumulation after 9, 12, and 21 years of enclosure was 7.92, 8.41, and 8.74 t/hm², respectively, which was 1.15, 1.28, and 1.37 times greater than those of the degraded TF oak forest, respectively. Longer enclosure times were associated with better litter water-holding capacity and improved rainfall retention. The maximum water holding capacity of TF oak forest after 9, 12, and 21 years of enclosure was 14.71, 15.81, and 17.18 t/hm², respectively, which was 1.36-, 1.54-, and 1.76-fold higher than that of the degraded TF oak forest. The effective retention capacity of TF oak forest after 9, 12, and 21 years of enclosure was 10.87, 11.70, and 12.78 t/hm², respectively, which was 1.29-, 1.46-, and 1.69-fold higher than that of the degraded TF oak forest, respectively. Litter water holding capacity and immersion time were significantly correlated (P < 0.001). The best fitting curve for this relationship took the form Hl=a + b ln t, and the coefficients of determination for all enclosures (R²) were greater than 0.9. The hydro-physical properties of surface soil of degraded TF oak forests improved following enclosure, with longer enclosure times associated with greater improvements in surface soil hydro-physical properties. Compared to the degraded TF oak forests, soil bulk density at 0-15 cm depth was reduced by 5.51%, 12.60%, and 17.32% in the TF oak forests after 9, 12, and 21 years of enclosure, while total porosity increased by 12.21%, 41.85%, and 72.35%, respectively. Longer enclosure times were associated with increased soil water storage capacity. Compared to the degraded TF oak forests, water holding capacity in soil capillary pores increased by 7.01%, 28.98%, and 54.83%, while water holding capacity in soil non-capillary pores increased by 46.14%, 126.19%, and 187.19%, respectively in the TF oak forests after 9, 12, and 21 years of enclosure. Litter and surface soil water holding capacity were improved significantly after enclosure and recovery of degraded TF oak forests. Thus, enclosure played an important role the recovery and improvement of the local ecological environment, and increased forest productivity.