桂林会仙喀斯特湿地芦苇群落土壤氮的季节变化

Seasonal change of soil nitrogen content in reed vegetation of Huixian Karst Wetland,Guilin,China

该研究以桂林会仙喀斯特湿地典型芦苇植物群落土壤为对象,研究了土壤氮含量的季节动态变化特征,探讨了土壤氮对水热季节变化的响应趋势。结果表明:土壤有机氮在全氮中所占比例较大,0~10 cm土层的全氮与0~10 cm和10~20 cm土层的速效氮季节变化特征一致,表现为夏季>秋季>春季>冬季;10~20 cm和20~30 cm土层的全氮和有机氮均表现为春季>夏季>秋季>冬季。0~10 cm土层的有机氮和10~20 cm土层的速效氮变化趋势一致,表现为秋季>夏季>春季>冬季。各层土壤硝态氮呈现出先升高后降低的单峰曲线变化趋势,均表现为夏季>春季>秋季>冬季,并与铵态氮0~10 cm和10~20 cm土层的季节变化趋势相一致。20~30 cm土层的铵态氮与0~10 cm和20~30 cm土层的土壤微生物量氮含量时间动态一致,均表现为春季>秋季>夏季>冬季,10~20 cm土层的微生物量氮表现为秋季>春季>夏季>冬季的趋势。土壤铵态氮含量明显高于硝态氮,各层土壤铵态氮含量基本呈现出不规则"M"形的双峰曲线变化。会仙喀斯特湿地典型芦苇植物群落不同土层土壤各形态氮含量的动态特征对水热变化的季节响应差异较大,不同月份之间有所不同,但均在冬季含量最低,与月均气温和月均降雨量的变化关系表现为不完全的同步趋势。土壤氮含量季节变化特征的差异主要与气温、水分条件、不同生长期芦苇吸收利用、土壤有机碳、凋落物养分的归还以及有机氮矿化等影响有关。该研究结果为桂林会仙喀斯特国家湿地公园生态功能恢复与可持续发展利用提供了科学依据。

In order to investigate the dynamic variation characteristics of soil nitrogen content in soils of reed community in Huixian Karst Wetland,the different levels of soil samples（ 0-10 cm,10-20 cm and 20-30 cm） were analyzed in laboratory. The results showed that organic nitrogen played a dominant role in the content of total nitrogen. The seasonal changes characteristics of total nitrogen in 0-10 cm soil layer were consistent with that of available nitrogen content in 0-20 cm soil layer,which had higher content in summer,followed by autumn and spring,with the lowest contents in winter. The order for seasonal variation of total nitrogen in 10-20 cm and 20-30 cm soil layers was spring,summer,autumn and winter,the same as organic nitrogen content. The trend for seasonal changes of organic nitrogen content in 0-10 cm soil layer was similar to available nitrogen in 10-20 cm soil layer,which showed that the content was higher in autumn,followed by summer and spring,with the lowest contents in winter. The variation of soil nitrate nitrogen showed a single peak curve during growing season,increased first and then decreased,which was the same to ammonium nitrogen content in 0-20 cm soil layer. The seasonal variation of ammonium nitrogen in 20-30 cm soil layer was consistent with microbial biomass nitrogen content in 0-20 cm soil layer,which showed that the contents were the highest in sping,lower in both autumn and summer,and the lowest in winter. The content of ammonium nitrogen was higher apparently than that of nitrate nitrogen,the changing trends of ammonium nitrogen in each soil layer appeared in an anomalous＂M＂shape. The seasonal difference of microbial biomass nitrogen in 10-20 cm soil was evident,and decreasing amplitude in season was autumn,spring,summer and winter in turn. The characteristics of various nitrogen forms in soils of reed community in Huixian Karst Wetland showed distinct differences with seasons,and the lowest in winter. Soil nitrogen content are important indicators for reflecting the status of soil nutrients and quality. In general,the contents and distributions of total nitrogen,ammonium nitrogen,nitrate nitrogen,available nitrogen,organic nitrogen,microbial biomass nitrogen in soils of reed community in Huixian Karst Wetland were maily influenced by multiple factors,such as plant absorption at different growth periods,soil organic carbon,the nutrient return of the plant litters,average monthly temperature,water conditions,soil organic nitrogen mineralization and so on. This study provides scientific reference for recovery of ecological fumtions and sustainable development and utilization of Huixian Karst Wetland Park.