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Title: [Effects of Chinese fir litter cover on its seedling emergence and early growth].
Author: Zhao C, Cai YB, Huang X, Liu QQ, Zhu CX, Yu JD, Wang ZN, Liu B.
Journal: Ying Yong Sheng Tai Xue Bao; 2019 Feb 20; 30(2):481-488. PubMed ID: 30915799.
Abstract:
Litter accumulation can strongly affect seedling emergence and early growth through both physical and chemical mechanisms, and can further influence natural regeneration. Chinese fir (Cunninghamia lanceolata) is one of the most important afforestation tree species. Its natural regeneration is poor, possibly due to the thick leaf accumulation inhibiting seedling emergence and growth. We used natural and plastic litter to study the effects of Chinese fir litter on its own seedling emergence and early growth, as well as to assess whether the effect was physical or chemical. In this experiment, two litter types (natural and plastic litter) and four different litter amounts (control, 0 g·m^-2; low, 200 g·m^-2; medium, 400 g·m^-2; high, 800 g·m^-2) were used. The results showed that compared to the control (0 g·m^-2), low litter amount (200 g·m^-2) exerted a slight positive effect on seedling emergence, whereas high litter amount (800 g·m^-2) significantly reduced the seedling emergence and survival rate in the case of both natural and plastic litter. With increasing litter amount, root length of seedlings decreased and stem length increased. The highest and lowest root mass, leaf mass, and total mass of seedlings were observed for the low and high litter amount, respectively, in the case of both natural and plastic litter. The root:shoot ratio of seedlings decreased with the increasing litter amount for both natural and plastic litter. The photosynthesis:non-photosynthesis biomass ratio of the seedlings was higher under all litter cover treatments, compared to that in the control. Because the effect of the same amounts of the natural and plastic litter on seedling emergence and early growth did not differ, the litter layer's short-term influence was primarily physical. As the litter cover increased, the initial slight positive effects on seedling emergence and early growth could shift to inhibitory effects. Moreover, to penetrate the thick litter layer, Chinese fir seedlings allocated more resources toward stems and aboveground growth. This study provided evidence for litter amount being a key ecological factor that affects the seedling development and subsequent natural regeneration of Chinese fir. 凋落物可通过物理和化学作用显著影响幼苗出土和早期生长,进而影响天然更新.杉木是中国南方重要的造林树种,但存在着天然更新障碍,其原因可能是林下较厚的凋落物层阻碍了杉木幼苗出土和早期生长.本试验利用覆盖自然和塑料凋落物来研究凋落物对杉木幼苗出土和早期生长的影响,并检验其影响是物理作用还是化学作用.本试验设置2种凋落物类型(自然和塑料凋落物)和4个覆盖厚度(对照,0 g·m^-2;浅层,200 g·m^-2;中层,400 g·m^-2;深层,800 g·m^-2).结果表明: 与对照(0 g·m^-2)相比,浅层(200 g·m^-2)凋落物覆盖对出苗率有促进作用但不显著,深层(800 g·m^-2)凋落物覆盖对出苗率和存活率有显著抑制作用.随着凋落物覆盖厚度的增加,幼苗根长不断减小,而茎长逐渐增加.凋落物浅层覆盖下杉木幼苗的根生物量、叶生物量和总生物量均最大,深层覆盖下最小.幼苗的根冠比随着凋落物覆盖厚度的增加而不断减小.与对照相比,凋落物覆盖下幼苗光合与非光合组织生物量比均有所增加.相同覆盖厚度下,自然和塑料凋落物对杉木幼苗出土和早期生长的影响均无显著差异,表明短期内凋落物覆盖对幼苗出土和早期生长的影响主要是物理作用.随着凋落物覆盖厚度的增加,杉木幼苗出土和早期生长表现为先促进后抑制,且杉木幼苗为了穿过厚厚的凋落物层倾向于把资源分配给地上部分.本研究结果为凋落物是影响杉木幼苗建植和天然更新的一个重要生态因子提供了试验证据.

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