Huang Li, Zhou Lihua, Wang Jingmei, Jin Cheng, Hu Siwei, Qian Shenhua, Lin Dunmei, Zhao Liang, Yang Yongchuan
Key Laboratory of the Three Gorges Reservoir Region's Eco-Environment Ministry of Education Chongqing University Chongqing China.
Joint International Research Laboratory of Green Building and Built Environment Ministry of Education Chongqing University Chongqing China.
Ecol Evol. 2020 Sep 9;10(19):10657-10671. doi: 10.1002/ece3.6719. eCollection 2020 Oct.
Declining forests usually face uncertain regeneration dynamics and recovery trajectories, which are challenging to forest management. In this study, we investigated the decline pattern of and examined the effects on conspecific seedling regeneration. We found that 61.45% of adult individuals were in decline and the smaller DBH size classes of trees (10-40 cm) had a greater probability of decline. Most of the intermediate decline (94.52%) and nondecline individuals (95.23%) did not worsen, and the crowns of 21.91% of the intermediate decline trees were recovered during 2013-2018. Adult tree decline had a negative effect on seed production (mean mature seed density of nondecline, intermediate decline, and high decline individuals was 167.3, 63.3, and 2.1 seeds/m, respectively), but no effect on key seed traits. The seed survival rate of declining trees was greater than that of nondeclining trees at both the seed production and seed dispersal stages. The seed to seedling transition rates in canopy gaps, decline habitats, and nondecline habitats were 7.94%, 9.47%, and 109.24%, respectively. The survival rate and height growth of newly germinated seedlings were positively correlated with the light condition, which was notably accelerated in the canopy gaps. Taken together, these results indicate that the reduction in seed production of some adult trees had a weakly negative effect on new seedling recruitment, while the improved environmental condition after the decline significantly enhanced the survival and growth of both advanced and new germinated seedlings. Looking at the overall life history, the short-term defoliation and mortality of some adult trees can be regarded as a natural forest disturbance that favors conspecific seedling regeneration. High-intensity management measures would be unnecessary in cases of an emerging intermediate decline in this forest.
森林衰退通常面临不确定的更新动态和恢复轨迹,这给森林管理带来了挑战。在本研究中,我们调查了[具体树种]的衰退模式,并研究了其对同种幼苗更新的影响。我们发现,61.45%的成年个体处于衰退状态,较小胸径级别的树木(10 - 40厘米)衰退的可能性更大。大多数中度衰退个体(94.52%)和未衰退个体(95.23%)没有恶化,2013 - 2018年期间,21.91%的中度衰退树木树冠得到恢复。成年树木衰退对种子产量有负面影响(未衰退、中度衰退和高度衰退个体的平均成熟种子密度分别为167.3、63.3和2.1粒/平方米),但对关键种子性状没有影响。在种子生产和种子传播阶段,衰退树木的种子存活率均高于未衰退树木。林冠间隙、衰退生境和未衰退生境中的种子到幼苗转化率分别为7.94%、9.47%和109.24%。新发芽幼苗的存活率和高度生长与光照条件呈正相关,在林冠间隙中显著加快。综合来看,这些结果表明,一些成年树木种子产量的减少对新幼苗的招募有微弱的负面影响,而衰退后环境条件的改善显著提高了已发育和新发芽幼苗的存活率和生长。从整个生活史来看,一些[具体树种]成年树木的短期落叶和死亡可被视为有利于同种幼苗更新的自然森林干扰。在这片森林出现中度衰退的情况下,无需采取高强度管理措施。