亚热带不同次生林地凋落物持水特性及季节变化

为了解亚热带不同演替阶段次生林地的凋落物持水特性规律，选取湖南大山冲森林公园保存完好的三种亚热带典型次生林地，按两月一次采集新近的凋落物并采用水浸泡法测定凋落物持水量、持水率和吸水速率，对比分析不同森林类型凋落物持水性差异及其与凋落物碳氮凋落量的关系。结果表明：（1）三种次生林地凋落物量及组成均表现出特有的变化规律。针叶林和常绿阔叶林凋落物量以夏季5-9月最大，落叶阔叶林凋落物则以春、秋两个季节最大；（2）三种次生林地凋落物的饱和持水量、半饱和时间以及与水亲和力均呈现显著季节性变化特征。针叶林凋落物饱和持水量在5-7月达到最高为（59.68±2.91） g/m²，常绿阔叶林凋落物饱和持水量则在9月达到最高，落叶阔叶林凋落物饱和持水量在11月份达到最高为（190.60±8.81） g/m²；三种次生林凋落物的半饱和时间均以11月份为最低，且落叶阔叶林凋落物半饱和时间比其他两种次生林地更低，全年平均（0.62±0.12） h；凋落物的水亲和力系数，全年均以落叶阔叶林最大为142.72±26.12；（3）落叶阔叶林凋落物饱和持水率全年显著高于其他两种次生林（P<0.01），且针叶林和落叶阔叶林凋落物饱和持水率均在11月份达到最大值；（4）落叶阔叶林凋落物吸水速率A值显著低于其他两种次生林（P<0.01），而针叶林凋落物吸水速率系数B值显著高于其他两种次生林（P<0.01）；（5）凋落物饱和持水量与凋落物水亲和力和饱和持水率存在显著正相关关系，与凋落物凋落碳氮总量同样存在显著正相关关系；凋落物饱和持水率与凋落物半饱和时间、吸水速率系数A和B值存在显著负相关，与凋落物碳含量和C/N比极显著负相关，与凋落物氮含量极显著正相关（P<0.01）。综上，不同次生林类型凋落物持水性存在显著差异，凋落物持水性与凋落物碳氮量存在显著联系，该研究为深入探讨森林生态环境效应提供了支撑，丰富了森林凋落物持水特性的研究理论。

Seasonal changes of litter water-holding characteristics under different secondary forests in subtropical area

In order to understand litter water-holding characteristics in secondary forests under different succession stages, three typically subtropical secondary forests were selected in Dashanchong Forest Park in Hunan Province. New litters were collected in every two months and measured its water holding capacity, water holding rate and water absorption rate by water soaking method. Then, the water holding capacity of litters in different forest types were compared. The relationships were analyzed between water holding capacity and carbon and nitrogen contents in litters. The results showed that:(1) the amounts and composition of litters in the three secondary forests presented unique changes. The amounts of litters in coniferous forest and evergreen broad-leaved forest were the largest from May to September in summer, while amounts of litters in deciduous broad-leaved forest were the largest in spring and autumn. (2) The saturated water holding capacity, half saturation time, and water affinity coefficients of litters in three secondary forests exhibited significantly seasonal variation characteristics. The saturated water holding capacity in coniferous forest litters reached a maximum of (59.68±2.91) g/m² from May to July, and the saturated water holding capacity in evergreen broad-leaved forest reached a maximum in September; the saturated water holding capacity of deciduous broad-leaved forest reached (190.60±8.81) g/m² in November. The half saturation time of litters in the three secondary forests was the lowest in November, and the half saturation time in deciduous broad-leaved forest litters was lower than that of other two forests types, with an annual average of (0.62±0.12) h; the litters'' water affinity coefficient was 142.72±26.12 in deciduous broad-leaved forest in the whole year. (3) The saturated water holding rate of litters in the deciduous broad-leaved forest was significantly higher than that in the other types throughout the year (P<0.01). The saturated water holding rate of litters in coniferous forest and deciduous broad-leaved forest reached the maximum in November. (4) The water absorption rate coefficient A of litters in deciduous broad-leaved forest was significantly lower than that in the other types (P<0.01), while the water absorption rate coefficient B in coniferous forest litters was significantly higher than that in the other types (P<0.01). (5) The saturated water holding capacity of litters showed significantly positive correlations with water affinity coefficients, saturated water holding rate, the total amount of carbon and nitrogen in litters. The saturated water holding rate showed significantly negative correlation with half saturation time and water absorption rate coefficient A and B, significantly negative correlations with carbon content and C/N ratio in litters, and significantly positive correlations with nitrogen content in litters (P<0.01). In summary, the water holding capacity of litters in the three secondary forests were significantly different. The water holding capacity was significantly correlated with carbon and nitrogen content in litters. This study enriches the research theory of litter water-holding characteristics and provides a theoretical basis for in-depth discussion of the ecological and environmental effects of forest litters.