甘肃兴隆山不同演替阶段典型森林群落的凋落物动态

【目的】分析不同演替阶段典型森林群落凋落物的量、组成特征及月动态,了解兴隆山森林生态系统碳贮量和养分循环状况。【方法】采用凋落物收集器法,对甘肃兴隆山森林演替阶段的3种典型森林群落针阔混交林(山杨(Populus davidiana)-白桦(Betula platyphylla)-青杄(Picea wilosonii)林)和暗针叶林(青杄-灌木林和青杄-箭竹(Fargesia nitida)-苔藓林)的凋落物量、组分、月动态进行了观测与研究。【结果】3种典型森林群落年凋落物量5 534.48～7 951.25 kg/hm²,大小排序为:山杨-白桦-青杄林>青杄-灌木林>青杄-箭竹-苔藓林,针阔混交林高于暗针叶林; 凋落量随森林正向演替的进行而不断减少。山杨-白桦-青杄林中以叶(44.91%)、杂物(20.53%)、枝(15.86%)、果(14.74%)为主,青杄-灌木林中以叶(41.22%)、杂物(23.58%)、枝(18.53%)、果(13.32%)为主,青杄-箭竹-苔藓林中以叶(37.48%)、杂物(27.51%)、枝(22.35%)为主; 在叶凋落物中,针阔混交林以阔叶为主,暗针叶林则以针叶为主。3种典型森林群落凋落量动态模式均为双峰型,但最高峰和最低峰出现时期有所不同,针阔混交林最高峰在10月,最低峰在7月; 暗针叶林最高峰在4—5月,最低峰在8—9月。针叶凋落量动态模式呈双峰型,高峰期出现在4月和10月; 阔叶、杂物、枝、果和花凋落动态模式呈单峰型,阔叶最高峰在10月,杂物、枝和果在4—5月,花在5—6月; 树皮凋落动态无明显变化规律。【结论】森林演替对凋落量及其凋落物组成影响明显; 随森林由阳性落叶阔叶林向阴性针叶林方向演替,森林年凋落量逐渐变小; 阔叶凋落量所占比例逐渐减小,而针叶所占比例逐渐增加。

Litterfall dynamics of typical forest communities at different succession stages in Xinglong Mountain of Gansu Province,China

【Objective】Provide a scientific basis for research on forest ecosystem carbon storage and nutrient cycling, by analyzing the quantity, seasonal changes and components of litterfall in three typical forests at different successional stages in the Xinglong Mountain of Gansu Province, China. 【Method】By using a litter trap, the quantity, components(needles, broadleaves, branches, flowers, fruits, bark and unclassified litter)of litterfalls and their monthly dynamics were measured in two successional stages of coniferous and broadleaf mixed forest(Populus davidiana-Betula platyphylla-Picea wilosonii forest)to dark coniferous forest(Picea wilsonii-shrub forest and Picea wilsonii-Fargesia nitida-moss forest)from August 2011 to July 2015.【Result】Annual litterfall amount ranged from 5 534.48 kg/hm² to 7 951.25 kg/hm² for the three forest communities, with the order ranked as Populus davidiana-B. platyphylla-Picea wilosonii forest >Picea wilsonii-shrub forest >Picea wilsonii-F. nitida-moss forest. The litterfall amount of the coniferous and broadleaf mixed forest was remarkably higher than that of the dark coniferous forest. The annual litterfall amount decreased gradually along with forest succession. Leaves(44.91%), unclassified(20.53%), branches(15.86%)and fruits(14.74%)were the main components of litter in the Populus davidiana-B. platyphylla-Picea wilosonii forest; leaves(41.22%), unclassified(23.58%), branches(18.53%)and fruits(13.32%)were the main components of litter in the Picea wilsonii-shrub forest; and leaves(37.48%), unclassified(27.51%), and branches(22.35%)were the main components of litter in the Picea wilsonii-F. nitida-moss forest. In leaf litter, broadleaves were dominant for the coniferous and broadleaf mixed forest, while needles were dominant for the dark coniferous forest. In all three communities, the annual dynamics of litterfall showed double-peaked curve patterns, although the timing of the highest and lowest points were different. For the coniferous and broadleaf mixed forest, the highest and lowest points occurred in October and July, respectively. For the dark coniferous forest, the highest and lowest points occurred in April or May and August or September, respectively. A double-peaked curve also described the monthly dynamics of needle litter, where the high points occurred in April or May and October. A single-peaked curve described the monthly dynamic of broadleaves, unclassified litter, branches, fruits and flowers. The highest peak of broadleaves occurred in October, while those for unclassified liter, branches, and fruits occurred in April or May, and that for flowers occurred in May or June. There was no obvious pattern for bark litter.【Conclusion】There was an obvious effect of forest succession on the amount and composition of litter. As forest succession progressed from deciduous broadleaf forest to dark coniferous forest, the annual litterfall amount decreased gradually. The percentage of annual litterfall of broadleaves gradually decreased, while that of needles gradually increased.