栎类天然次生林不同组分及土壤碳氮分布对森林抚育的响应

Carbon and nitrogen distribution with forest tending in a natural secondary oak forest

森林抚育作为重要的森林经营措施,深刻影响着森林生态系统碳储量及其分布。根据抚育前后中幼龄栎类Quercus天然次生林林分密度,分为轻度(21%),中度(35%),重度(54%)和对照(0%)等4个抚育处理水平,抚育2a后进行测树学调查,研究乔木层各组分、林下植被、凋落物层和土壤碳储量及碳氮分布特征。结果表明:基于16株树干解析资料建立的栎类单株生物量估算模型,可以用来估算栎类各组分生物量;不同抚育强度栎类天然次生林乔木层干、皮、枝、叶和根组分中,叶的碳、氮质量分数最大;乔木层、林下植被和凋落物层碳、氮质量分数均随抚育强度增大而增加,碳氮比(C/N)均随抚育强度增大有减小的趋势;不同抚育强度乔木层各组分生物量和碳储量大小顺序为干>枝>根>叶>皮,轻度、中度、重度和对照的乔木层碳储量分别为21.42,32.62,51.24,14.35t·hm^(-2);林下植被、凋落物层生物量和碳储量大小关系为对照>轻度>中度>重度,各层碳储量大小关系均为乔木层>凋落物层>林下植被层;重度抚育有利于提高土壤表层有机碳、全氮质量分数及碳储量,重度抚育时3个指标值分别达到16.93 g·kg^(-1),3.88 g·kg^(-1)和22.79 t·hm^(-2)。森林抚育有利于栎类天然次生林乔木层、林下植被层生物量和碳储量的提高,不利于凋落物层碳储功能的发挥,而乔木层在栎类天然次生林中碳储量最大,碳汇潜力也最大。

Forest tending is a crucial practice in the forest ecosystem management, which has a profound impact on forest ecosystem carbon（C） and nitrogen（N） storage and its distribution. However, a great deal of uncertainty remains concerning how plant carbon and nitrogen distribution may be affected by forest tending. In this study, a natural Quercus（oak） secondary forest under different tending intensity treatments（ 21%, 35%, and54%） with a control（nontending） was investigated in west mountains area of Henan Province. The characteristics of plant carbon storage as well as the distribution of plant carbon and nitrogen in four stand types with forest tending were studied. Trees under different tending intensity treatments were surveyed after two years of forest tending. Our results show that forest tending operations had a significant influence on plant carbon and nitrogen distribution. Prior to estimate the stand biomass, an estimation model of a single plant biomass was established based on the data of sixteen trees. The plant carbon content and nitrogen content of stem was higher than that of bark, branch, leaf, and root of Quercus in different forest tending treatments. Biomass and carbon storage for all tending intensities in the tree population followed the order of stem 〉branch〉 root〉 leaf〉 bark. Plant carbon storage for light intensity was 21.42 t·hm^-2, for moderate intensity was 32.62 t·hm^-2, for heavy intensity was 51.24 t·hm^-2, and for the control was 14.35 t·hm^-2. The biomass and plant carbon storage of understory vegetation and litter in different forest tending treatments followed the order of control 〉light〉 moderate〉 heavy. The plant carbon storage in different vegetation layers followed the order of overstory〉 litter〉 understory. Results showed that heavy intensity tending was more beneficial than other treatments to improve soil organic carbon content, soil total nitrogen content, and the accumulation of soil carbon. This study showed that forest tending was beneficial and could provide a basis for forest carbon sink evaluation to assist in scientific and reasonable forest tending management.