多重干湿交替格局下土壤Birch效应的响应机制

The Response of Birch Effect Under Multiple Wet-dry Cycles

为了探究多重干湿交替格局及土壤团聚体粒径对土壤呼吸作用尤其是Birch效应的影响机理,以3种不同团聚体粒径的表层土(0～20 cm)为受试土壤,通过采用室内孵育试验的方法,研究了多重干湿交替循环及不同土壤团聚体粒径对Birch效应产生的影响。结果表明:复水促进了土壤呼吸作用,增加了土壤微生物生物量,但对微生物量和呼吸作用产生的激增效应并没有持续很长时间。复水3 h后呼吸速率达到峰值,并且随着干湿周期频率的增加而降低,其中大土粒降低幅度最小。不同土壤团聚体粒径对Birch效应的影响强度不同,但二者并不是简单的线性关系。总之,土壤团聚体能够保护部分有机质不被微生物分解矿化,多重干湿交替干扰了这种保护作用,提高了有机碳的生物相容性。Birch效应中被矿化的有机碳更多是来自于新的有机质的暴露,部分来自干旱期微生物细胞内积累的溶质。值得注意的是随着干湿循环数的增加,被暴露的新的有机质在被矿化分解前可能还存在其他中间过程。

In order to research the especially Birch effect, based on effect of multiple wet-dry cycles and soil aggregate size on soil respiration three different aggregate size surface soil （0-20 cm） for the tested soil, through the use of indoor incubation test method, research the multiple wet-dry cycles and different soil aggregate size to Birch effect. The results showed that, after water promoted the soil respiration, increased the soil microbial biomass, but the surge effect did not last long. Respiratory rate was peak after rewet 3 h, and the more wet-dry cycles, the lower respiration rate. Different soil aggregate grain size of Birch effect of strength different, but they had not a simple linear relationship. The results also showed that, the soil aggregates could protect soil organic matter from decomposing by microbe, while multiple wet-dry cycles interfere with this protection function and improved the organic carbon biocompatibility. A large amount of carbon source from Birch effects came from the new organic matter of exposure, a little the accumulation of solutes in cells during dry period. It was worth noting that before the new organic matter from the exposure was mineralized and decomposed, other process might still exist.