Biological Nutrient Cycling And Ability Of Solid Carbon In Acacia Cincinnata And E.urophylla×E.gradis Plantations On The Sandy Coastal Plain Soil

Casuarina equisetifolia as the main tree species of protection forest in thesoutheast coastal sandy land of China, In recent years, the Casuarina equisetifoliaappears many problems, such as a single species, the growth decline and to updatedifficulties. In this paper, we’ve studied the nutrient cycling and carbon sequestrationcapacity of two tree species-Acacia cincinnata and E.urophylla×E.gradis, in order tobe able to find the two as the coastal sandy land shelterbelt trees and practical basis.The results were as follows:1. There’re obvious differences between Acacia cincinnata andE.urophylla×E.gradis with8years in the growth of plantation. Their average DBH（8.5cm<11.31cm）, tree heigh（t7.5m<13.9m）, individual volume（0.0226m³<0.0634m³）and preservation rate respectively（82.6%<94.13%）are markedly different. Thetotal biomass of plantation tree layer of Acacia cincinnata is38.67t·hm^-2, the averagebiomass of root in various organs is the biggest (12.69t·hm^-2), which accounts for32.81%of the total biomass, and the order of each organ biomass is: root> trunk>branch> bark> leaf. On the other hand, the total biomass of plantation tree layer ofeucalyptus is79.75t·hm^-2，the average biomass of trunk in various organs is thebiggest (39.12t·hm^-2), which accounts for46.18%of the total biomass, and the leafbiomass is minimum which accounts for only4.2%, and the order of each organbiomass is: trunk> root> branch> bark> leaf.2. The annual output of artificial forest litter of Acacia cincinnata is3565.2kg·hm^-2approximately. The main components of litterfall are leaves, and annualamount is2418.33kg·hm^-2that accounts for67.83%of the annual output of artificialforest litter of Acacia cincinnata. The next are mixed, their annual amount is810.87kg·hm^-2which accounts for22.74%. The least are fruits and barks, and the annuallitterfall amount of them respectively is11.33kg·hm^-2and25.33kg·hm^-2. On theother hand, the annual output of artificial forest litter of E.urophylla×E.gradis is6745.93kg·hm^-2that is about2times as much as Acacia cincinnata. The annuallitterfall amount of its leaves is4151kg·hm^-2accounting for61.53%of the totallitterfall amount, which are the main components. The annual litterfall amounts ofbranches and barks are about the same, and their annual litterfall amounts are850.13kg·hm^-2and853.27kg·hm^-2, accounting for12.60%and12.65%of the annuallitterfall amount of E.urophylla×E.gradis respectively. 3. The monthly dynamic changes of litterfall of Acacia cincinnata plantation inone year show unimodal pattern. It reaches the maximum in July when the litterfallamount is824.33kg·hm^-2, and it reaches the minimum in January when the litterfallamount is only30.67kg·hm^-2.While the monthly dynamic changes of litterfall ofE.urophylla×E.gradis plantation show bimodal l pattern. It reaches its peak in Mayand July when the amounts are1587.2kg·hm^-2and1499.2kg·hm^-2respectively.Theseasonal dynamics of annual litterfall amount of Acacia cincinnata is: summer>spring> autumn> winter. The maximum amount of litterfall is in summer when theamount is2050.5kg·hm^-2accounting for57.52%of the total amount, while theminimum amount is in winter which accounts for only7.31%. And the seasonaldynamics of annual litterfall amount of E.urophylla×E.gradis is: summer> autumn>spring> winter. The maximum amount of litterfall is in summer just like Acaciacincinnata when the amount is4315.2kg·hm^-2accounting for63.97%of the totalamount.4. The decomposition coefficient of Volume pod Acacia cincinnata plantations litterleaves is less than Tail giant E.urophylla×E.gradis, which are0.4105and0.7069respectively。The half-life period of Volume pod Acacia cincinnata is1.69a, turnoverperiod is7.3a, while the two numbers of Tail giant E.urophylla×E.gradis are0.98aand4.2a respectively. The nitrogen return quantity of Volume pod Acacia cincinnataplantations litter leaves and Tail giant E.urophylla×E.gradis are51.54kg·hm^-2and58.44kg·hm^-2，phosphorus return quantity is0.929kg·hm^-2，which is far less than Tailgiant E.urophylla×E.gradis plantations3.141kg·hm^-2，potassium return quantity are6.851kg·hm^-2and22.386kg·hm^-2,calcium return quantity are17.113kg·hm^-2and48.032kg·hm^-2，magnesium return quantity are13.427kg·hm^-2and19.581kg·hm^-2，sodium return quantity are0.016kg·hm^-2and0.042kg·hm^-2，ferrum return quantityare0.746kg·hm^-2and2.042kg·hm^-2，manganese return quantity are0.541kg·hm^-2and5.69kg·hm^-2，zinc return quantity are0.124kg·hm^-2and0.253kg·hm^-2, copperreturn quantity are0.026kg·hm^-2and0.042kg·hm^-2.5. The biomass of volume pod Acacia cincinnata litter layer is far less than that of tailgiant E.urophylla×E.gradis.They are respectively2.31t·hm^-2and14.54t·hm^-2. Bothbranches respectively account21.41%and39.03%in the total biomass of thelitter.The nitrogen’s volume in the volume pod Acacia cincinnata plantations litterlayer is the biggest, the sodium the minimum, specific volume size is:N>Ca>Mg>K>Fe> Mg>P> Ze> Cu> Na, the biggest volume of tail of giantE.urophylla×E.gradis plantation forests nitrogen litter layer is nitrogen, similarly, thesmallest is sodium, specific volume order is: N> Ca> K> Mg> Mg> Fe> P> Ze>Cu> Na. The maximum water holding capacity of volume Acacia cincinnata podsand tail giant E.urophylla×E.gradis plantations litter layer are6.36t·hm^-2and38.75t·hm^-2;The maximum held rate and maximum held amount of volume pod Acaciacincinnata plantations litter were262.67%and36.21t·hm^-2. The effective held rate onaverage of volume pod Acacia cincinnata plantations litter layer is223.27%, whichis higher than that of the tail giant E.urophylla×E.gradis’213.93%, combining thevolume amount of both litter layer, the volume of effective held amount were5.11t·hm^-2and30.78t·hm^-2respectively. 6. The total carbon reserve of Volume pod Acacia cincinnata and Tail giantE.urophylla×E.gradis plantations are24.82t·hm^-2and49.58t·hm^-2respectively.Among them, the storage of arborous layer is the largest, which are17.02t·hm^-2and36.98t·hm^-2, accounted for68.57%and74.59%of the total. While storage in soillayer are7.13t·hm^-2and6.41t·hm^-2, only accounted for28.73%and12.93%of thetotal.