Effects Of Kandelia Candel Mangrove Restoration On Soil Physical, Chemical And Biochemical Parameters In Jiulong River Estuary

Effects of restoration of Kandelia candel mangrove vegetation on soil physical, chemical and biochemical parameters were investigated in Jiulongjiang river estuary. At Site Qingjiao-Baijiao,one five-year old replanted forest,one six-year old replanted forest,one eight-year old replanted forest,one nature forest and one barren beach plot were selected.Meanwhile,one twenty-year old replanted forest,one forty-four-year old replanted forest and one barren beach plot were selected at Site Caoputou.The aim of this study was to explore variation of soil parameters along with development of replanted mangroves.Water content,pH and interstitial water salinity decreased with restoration time at both Qingjiao-Baijiao and Caoputou.MANOVA indicated that restoration time had remarkable effects on pH(p＜0.001) and soil pH values in the barren beach and natural mature K.candel mangroves were 6.64 and 4.56 at Qingjiao-Baijiao,respectively. Soil volume weight increased with soil depth,but fractal dimension of surface layer was highest.At mid flat,water content and interstitial water salinity was highest, while fractal dimension was lowest with value of 2.1208.For nutrients,restoration time had remarkable effects on total nitrogen, NH₄⁺-N,available phosphorus,organic carbon,humic acid and fulvic acid at both sites(p＜0.001).Total nitrogen in K.candel mangroves was higher than in barren beach,while total phosphorus in K.candel mangroves is lower than in barren beach; NH₄⁺-N and available phosphorus increased with restoration time,and their contents were 20.26 and 0.8154 mg/kg in the barren beach at Qingjiao-Baijiao,183.55 and 15.6950 mg/kg in the natural mature K.candel mangrove.Organic carbon in the natural mature K.candel mangrove and barren beach were 22.3526 and 13.0981 g/kg respectively.Organic carbon increased with restoration time at Caoputou,and humic substances,humic acid and fulvic acid were siginificantly correlated with organic carbon(r=0.904,p＜0.01;r=0.839,p＜0.01;r=0.817,p＜0.01),with the same tendency with organic carbon.NH₄⁺-N significantly increased with soil depth(p＜0.001).Tide level had remarkable effects on total phosphorus,NH₄⁺-N,organic carbon,humic acid (p＜0.001):total phosphorus was highest in inner flat,while NH₄⁺-N was highest in outer flat,and others were highest at mid flat.This showed that mid flat had most abundant nutrients and suitable for mangrove growth.For soil biochemical parameters,restoration time also had remarkable effects on microbial respiration,urease activity,catalase activity(p＜0.001).With restoration time,microbial respiration and urease activity increased but catalase activity decreased.Urease activity in the barren beach and natural mature forest are 17.75 and 46.27 mg NH₃-N/gDW,catalase activity in the barren beach and natural mature forest arel 7.07 and 11.44 ml 0.1N KMnO₄/gDW respectively.With increase in soil depth in natural mature forest,microbial respiration and urease activity increased but catalase activity decreased.As for tide level,microbial respiration,urease activity and catalase activity were lowest in outer fiat,showing that microbial activities were low due to long-time tidal inundation.In a conclusion,mangrove restoration of K.candel had remarkable enhancement on soil physical,chemical and biochemicalc parameters.