神农架常绿落叶阔叶混交林凋落物动态及影响因素

Litter dynamics of evergreen deciduous broad-leaved mixed forests and its influential factors in Shennongjia, China

凋落物是陆地生态系统的重要组成部分,凋落物动态特征可以反映出生态系统的存在状况以及环境对植被的影响作用。为探究北亚热带常绿落叶阔叶混交林凋落物产量及现存量的动态及其影响因素,该研究观测了神农架地区一处典型植被2009–2015年的凋落物产量及现存量,据此分析其动态特征及其与气象因素的关系。研究结果表明:该森林凋落物平均年产量及现存量分别为5.94 t·hm^(–2)和10.46 t·hm^(–2),2009至2014年均无明显年际变化趋势,但在2015年均显著降低,且当年倒春寒天数显著高于其他年份;季节动态变化呈现双峰型,峰值分别出现在3–5月和10月;凋落物月产量与当月的前第1–4个月的月平均气温正相关,与当月的前第8–10个月的月平均气温负相关,且与当月的前第6–7及第10个月的月平均相对湿度负相关;凋落物产量季节性指数平均值为0.032,与年平均气温显著正相关。可见,长时间倒春寒现象会显著影响凋落物年产量及现存量,月平均气温和相对湿度对凋落物产量季节动态的影响有明显的滞后性,且年平均气温对北亚热带主要森林类型的凋落物产量季节性指数有显著影响。

Aims Litter is an important component of terrestrial ecosystems. The dynamics of litter can reflect the stage of terrestrial ecosystems and the impact of environment on vegetation. Our objective was to explore the dynamics of litter production and standing crop in evergreen deciduous broad-leaved mixed forests and the underlying factors. Methods During 2009–2015, we observed the litter production and the standing crop of a typical vegetation at Shennongjia, Hubei Province and analyzed their dynamics and relationships with meteorological factors. Important findings 1） The results showed that the average annual litter production and standing crop were 5.94 t·hm^-2 and 10.46 t·hm^-2, respectively. Additionally, there was no remarkable inter-annual changing trend between 2009 and 2014, nevertheless a significant lower value appeared in 2015 with much more days of late spring coldness. 2） The seasonal dynamics presented double peaks, in March to May and October separately. 3） The monthly litter production was positively correlated with the monthly average air temperature of the previous 1–4 months, but negatively correlated with that in the 8 th, 9 th and 10 th months before the month. In addition, it was negatively associated with the monthly average relative humidity of the 6 th, 7 th and 10 th months before the month. 4） The average seasonality index of litter production was 0.032, which was strongly positively correlated with the annual average air temperature. We concluded that the phenomenon of long-term late spring coldness will affect annual litter production and standing crop significantly. The monthly average air temperature and relative humidity had significant lag effect on the seasonal dynamics of litter production, and the annual average air temperature had positive influence on the seasonality index of litter production in the major forest types in north subtropics.