关键词: CO₂浓度, 叶绿素荧光, 粳稻, 光系统Ⅱ

Abstract: Litterfall plays an important role in nutrient cycling and energy flow in terrestrial ecosystems. We collected 532 literatures published in 1970-2017 that studied forest litterfall, extracted 373 data points, and established a database of litterfall in natural forests in China. The production, composition and seasonal dynamics of the litterfall were analyzed, and their relationships with temperature and precipitation were examined at the national scale. The results showed that mean annual litterfall production of the natural forests in China was (5.33±2.87) t·hm^-2. With respect to litterfall production at the national scale, the rank of forest types was: rainforest > evergreen broadleaved forest > broadleaved and coniferous mixed forest > deciduous broadleaved forest > coniferous forest. Across different climatic zones, litterfall production of subtropical broad leaved forest and broadleaved and coniferous mixed forest were significantly higher than that in the temperate zone. There were no significant differences in litterfall production between tropical coniferous forests and temperate coniferous forests. In all the forests, leaf was the main component of litterfall, which accounted for 67.49%±9.75% of the total. The contribution of branch, reproductive organ, and other components was 16.45%±7.30%, 8.16%±5.18% and 7.88%±5.72%, respectively. Among them, the proportion of leaf of the deciduous broadleaved forest was the highest, accounting for 75.07%±9.92%. There were no significant differences in leaf litter among the other forest types. The seasonal dynamics of the litterfall in Chinese natural forests as a whole showed a bimodal pattern, with peaks occurring in April and October. When separated by forest types, rain forest and deciduous broadleaved forest showed a unimodal pattern, broadleaved and coniferous mixed forest showed a bimodal pattern, and evergreen broadleaved forest and coniferous forest showed a multimodal pattern. At the national scale, litterfall production was positively correlated with mean annual temperature and mean annual precipitation. The responses of forest litter production to hydrothermal factors were different among different climatic zones. In the temperate areas, litterfall production was positively correlated with mean annual temperature and mean annual precipitation, while in the subtropical areas, litterfall production was positively correlated with mean annual temperature, and there was no significant correlation between litterfall production and mean annual precipitation. In the tropical areas, litterfall production was negatively correlated with mean annual temperature but had no significant correlation with mean annual precipitation. This study provides implications for the studies of nutrient cycling in forest ecosystems and data support for the studies of carbon cycling in the context of global climate change.

Key words: chlorophyll fluorescence, PSⅡ, CO₂ concentration, Japonica rice