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三峡库区消落带会经历周期性的淹水-出露循环过程,消落带在出露期大量植物生长,淹水期植物体淹没腐解并释放氮磷养分,可能加剧三峡水库水环境压力.狗牙根[Cynodon dactylon(Linn.)Pers.]是三峡库区分布最广泛的优势植物之一.针对三峡水库水环境条件(温度、p H和光照)变化对狗牙根淹水条件下矿化分解及养分释放过程的影响进行了研究.结果表明,狗牙根淹水后,植物残体矿化分解,干重下降,全氮和全磷含量减少.狗牙根浸泡200 d后,25℃和15℃时总氮(TN)释放量分别为(2.66±0.29)g·kg~(-1)和(3.76±0.04)g·kg~(-1),总磷(TP)释放量分别为(0.79±0.03)g·kg~(-1)和(1.40±0.02)g·kg~(-1);上覆水p H为5.0、7.0、9.0时,TN释放量分别为(3.76±0.08)、(2.66±0.29)、(2.55±0.12)g·kg~(-1),TP的释放量分别为(1.53±0.04)、(0.79±0.03)、(1.70±0.07)g·kg~(-1);避光时上覆水TN和TP的释放量为(3.87±0.14)g·kg~(-1)和(1.78±0.08)g·kg~(-1).氮的释放以颗粒态氮(PN)为主,占80%以上,而颗粒态磷(PP)占比在50%左右.随三峡水环境条件变化,如温度降低,狗牙根的氮磷浸泡释放量增大;而酸、碱性水体较中性条件有利于氮磷释放;避光时狗牙根的氮磷释放得到促进.研究结果表明三峡水库冬季蓄水或污水排放导致的水环境变化将进一步促进消落带植物淹水分解及养分释放,从而可能加剧三峡库区水体富营养化.
The fluctuating zone of the Three Gorges reservoir area will experience periodic flooding-dewatered circulation processes. During the exhumation period, a large number of plant growth occurs in the ebb and take part in the flooding period, and submergence, decomposition and release of nitrogen and phosphorus nutrients may aggravate the water environment of the Three Gorges Reservoir (Cynodon dactylon (Linn.) Pers.] Is one of the most widely distributed and dominant plants in the Three Gorges Reservoir area.According to the change of water environmental conditions (temperature, pH and light) The results showed that after the bermudagrass flooded, the mineral residues decomposed, the dry weight decreased, and the contents of total nitrogen and total phosphorus decreased.After soaking for 200 days, The total nitrogen (TN) release amount was (2.66 ± 0.29) g · kg -1 and (3.76 ± 0.04) g · kg -1 at 15 ℃, and the total phosphorus release was ( 0.79 ± 0.03 g · kg -1 and 1.40 ± 0.02 g · kg -1, respectively. When the overlying water p H was 5.0, 7.0, 9.0, the TN release was (3.76 ± 0.08), (2.66 ± 0.29) and (2.55 ± 0.12) g · kg -1, and the release of TP were (1.53 ± 0.04), (0.79 ± 0.03) and (1.70 ± 0.07) g · kg -1 ). The release amounts of TN and TP in overlying water were (3.87 ± 0.14) g · kg -1 and (1.78 ± 0.08) g · kg -1 in darkness. (PN), accounting for more than 80%, while the content of particulate phosphorus (PP) was about 50% .With the changes of water environment in the Three Gorges Project, such as the decrease of temperature, the release of nitrogen and phosphorus , While acid and alkaline water were more favorable for the release of nitrogen and phosphorus than those for neutral water.The release of nitrogen and phosphorus in Bermudagrass was enhanced when light was dark.The results showed that the water environment change caused by the impoundment of water and sewage in the Three Gorges Reservoir would be further promoted The flooding decomposition and nutrient release of the plant in the ebb zone may increase the eutrophication of the water in the Three Gorges reservoir area.