火烧强度对中亚热带人工造林初期土壤呼吸的影响

在热带和亚热带森林中，火烧是一种清理采伐迹地的有效管理措施。尽管许多研究表明，火烧刺激了土壤的碳排放，但对亚热带火强度对土壤呼吸的影响还缺乏了解。在中亚热带米槠常绿阔叶次生林采伐迹地上，设置高火烧强度（HF）、低火烧强度（LF）炼山造林处理，利用LI-8100对造林初期（2012年3月-2012年12月）土壤呼吸进行测定，同时监测观测期土壤温度、含水量以及降雨量等气象因子，分析不同火烧强度对中亚热带造林初期土壤呼吸及排放量的影响，同时探讨影响土壤呼吸变化的主要因素。结果表明：（1）观测期间不同火烧强度对土壤呼吸的影响呈现出明显的时间变化特征：与对照（CT）相比，土壤呼吸在火烧后2个月以内显著增加（P<0.05），HF和LF分别增加76.3%和55.3%；在火烧后2-5个月内三种处理间没有显著差异（P>0.05）；但之后，火烧处理土壤呼吸显著低于CT （P<0.05），HF和LF分别降低40%和32.6%；在观测期间火烧处理没有导致土壤CO₂累计排放量的增加。（2）火烧处理下，仅HF处理中土壤呼吸与土壤温度显著相关（P<0.05），但拟合决定系数较低。（3）单次降水事件会导致火烧处理下土壤呼吸的增加，而对照无明显增加；但连续性降水事件中，降雨早期促进土壤呼吸，而后期呈现出抑制作用。

Effect of fire intensity on soil respiration in the early stage of afforestation in mid-subtropic

Slash burning is an effective management to clean plant residue before seedling plant in tropical and subtropical forests. Although many studies have been showed that slash burning stimulated carbon emission from soil, there still lack understanding on how fire intensities on soil respiration in subtropics. In this study, clear cutting an evergreen broad-leaved secondary forest dominated by Castanopsis carlesii and leaving the plant residue on the surface soil before slash burning are used. The High fire intensity (HF) and low fire intensity (LF) treatments were set up after slash burning. Soil respiration was measured by LI-8100 at the early stage of the tree plantation (from March to December, 2012), and soil temperature, soil water content and rainfall were surveyed simultaneously. The results show that:(1) slash burning stimulated soil respiration but highly temporal variation with times. Compared with the control (CT), soil respiration in HF and LF increased by 76.3% and 55.3% in the first two months after slash burning (P<0.05), respectively. However, there were no significant differences among treatments from 2nd-5th months after slash burning (P>0.05). Then, slash burning decreased soil respiration after the 5th month (P<0.05), while HF and LF decreased by 40% and 32.6% to CT, respectively. Thus, slash burning did not stimulated the sum of soil CO₂ emission during the observation period. (2) soil respiration was significantly correlated with soil temperature in the HF treatment (P<0.05) with low fitting determination. However, no significant correlation between soil respiration and soil temperature was found in other treatments. (3) A single precipitation event stimulated soil respiration rate in both HF and LF, but not in the CT. We also found that rainfall promoted soil respiration in the early time and inhibited soil respiration in the late time during the continuous precipitation.