| Emergent plants is an important component of the ecosystem, it plays an important rolein the process of purificated the qulity of water and increased the effects of landscape forlakeshore. This article carried out simulation and field experiment in differentmonths,different harvesting frequency and different positions of the harvest, based on thestudy of the emergent plant growth characteristics and the impact to water environment inthe progress of growth and decay and combined with the survey of distribution withemergent plant from the whole lakeshore,to study the regrows status of the emergentplant and the impact on the water environmen after harvest which was to study primarilythe key parameters of emergent plant harvesting.The main results were as follows.1. The total biomass of emergent plants in the whole lakeshore was2563.5tons,theZ.caduciflora was the dominant species in their communities constitute (62.5%), P.australis (17.5%) and T. latifolia (11.3%) also had a certain distribution area.Zizaniacaduciflora and Phragnites australis began to germinate in March， fast-growing duringApril to June, stable in August, began to decline in November. The biomass of Typhalatifolia attained to maximum in July and began to decline in September.2.In the goocess process of emergent plants,It has significantly inhibitory effect to thealgae and degradation effect to TN during the period (April-June) of rapid growth foremergent plants,and with the gradual goowth into the stable phase,the effects decreasedin July.3.The decomposition rate of S. validus was the largest among these aquatic plants, andthe next was that of Z. caduciflora and T. latifolia, the slowest was that of P. australisduring the decomposition processes. The order of total nitrogen amounts released fromfour aquatic plants (per dry weight) was S. validus, Z. caduciflora/T. latifolia and P.australis and the order of total phosphorus amounts released was S. validus, Z.caduciflora, T. latifolia and P. australis. In the decomposition process,The concentrationsof total nitrogen, total phosphorus and COD increased rapidly during the initial stage ofthese plants decomposition processes, and then they decreased slowly. However, thevalues of pH and DO decreased quickly during the initial stage, and then increasedslowly.Combing spatial distribution investigation of emergent aquatic plants in thelakeshore, total nitrogen and total phosphorus loads released form these emergent aquaticplants in decomposition of the lakeshore was estimated. The percentage of nitrogendecomposed was higher than that of phosphorus, and the proportion of decomposedphosphorus entered in water was higher than that of nitrogen.The amounts of totalnitrogen and total phosphorus contained in four aquatic plants in the lakeshore of LakeErhai is17.6t and2.88t. The amount of total nitrogen and total phosphorus decomposedfrom these plants was6.19t and1.12t and2.58t and0.89t entered into water after shortterm decomposition.4.It had significantly effect to improve the water quality by emergent plantsharversting.August was better for regeneration of Z. Caduciflora.in October，comparedwith August，regeneration rate was decrease29.6%，the length and diameter ofregeneration plant respectively decrease26.9%and25.9%. Repeat harvest had inhibiting effect to subject， compared with August and October single cutting， maximumregeneration ratio of repeated cutting for the same pieces of experiment quadrat haddecrease37.1%and10.6%.thus, harvest management should be based on single cutting.on the phytal zone(depth of water<15cm),best cutting position of Z. caduciflora was30cm above sludge， which had the regeneration rate of93.4%.on the profundalzone(depth of water>50cm),along with water level was better，the regeneration rate was100%. In the coming year,the plants’ density increased, diameter and height decreased,biomass did not change after the November harvest of Z. caduciflora. The diversity ofemergent plants had no significant changes after August and November harvest. |
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