The effects of Sasa and canopy gap formation on tree regeneration in an old beech forest

Abstract. We examined the response of tree seedling emergence and survival to the dieback of Sasa and canopy gap formation in an old‐growth forest near Lake Towada, northern Japan. Synchronous death of Sasa occurred in 1995. We established four types of sampling sites differing in forest canopy conditions (Closed or Gap) and Sasa status (Dead or Live). Gap‐Dead sites had the highest light levels and the greatest fluctuation in soil temperatures. The death of Sasa alone facilitated the emergence (Acer japonicum, Fagus crenata, Fraxinus lanuginosa, and Tilia japonica) and survival (Acanthopanax sciadophylloides, F. crenata, F. lanuginosa, Kalopanax pictus, and Sorbus commixta) of species with a seedling bank strategy. Cercidiphyllum japonicum grew at all sites at a higher density than other species, but survived well only in Gap‐Dead sites. This behaviour was associated with a seed rain strategy. The additive effects of Sasa death and canopy gap formation promoted seedling emergence of pioneer tree species (Betula maximowicziana, Lindera umbellata, and Magnolia obovata), probably through break of dormancy by the large temperature fluctuation. In addition, the scarcity of advance regeneration in canopy gaps due to Sasa cover facilitates the regeneration of pioneer species. The dominance and dieback cycle of Sasa contributes to species diversity in this forest.     

Influence of a developing tree canopy on the yield of Pennisetum pedicellatum sown on a mine spoil

Abstract. Shoot and root biomass yield of a sown grass, Pennisetum pedicellatum, were measured at below-canopy, canopy edge and open locations in young monoculture stands of eight tree species planted on a coalmine spoil. Incident light as percentage of full sunlight decreased from open to canopy edge to below-canopy locations. The shoot and root weights of Pennisetum in different tree stands for each of the three locations were significantly different and were significantly related to each other, and to percentage sunlight across all tree species plots and locations. The gradient of incident light was the principal factor governing the gradient of grass biomass under developing canopies of tree plantations on the mine spoil.     

降水变化和种间竞争对红松和蒙古栎幼苗生长的影响

针对全球变暖导致的降水格局的变化,选择长白山红松针阔叶混交林主要树种蒙古栎和红松幼苗为研究对象,在野外自然条件下人工模拟增、减水30%对单种和混种的针阔叶树种形态、生长和生物量分配的影响. 结果表明：对于蒙古栎幼苗,与单种处理相比,混种显著增加了其冠幅和主根长,与对照处理相比,减水处理显著提高了其茎质比、降低了其主根长; 对于红松幼苗,与单种处理相比,混种显著减少了其基径、树高、叶片数和根、茎、叶质量及总干质量,与对照处理相比,减水处理显著降低了其主根长、叶片数、叶质量和总干质量以及叶质比,同时显著提高了茎质比. 增水处理对二者的影响均不显著. 在树木生长初期,种间竞争和降水格局变化对蒙古栎和红松幼苗形态和生长均产生显著影响,对红松幼苗的影响更大.