| Purple soil is one kind of important unirrigated tilth soil in southern China. Its ecosystems subject a severe erosion and degradation due to low soil antierodibility, high rainfall and rain intensity, and anthropogenic disturbance. It is an urgent issue for local ecological improvement and economical development to initiate a program of ecological restoration and rehabilitation. Although some hardness measures had been taken for a long time and those ecological profits gained thereby such as control of soil erosion and improved soil fertility had been indicated, the mechanism of ecological restoration in such degraded ecosystems has scarcely been addressed.In guidance with the theory of ecological restoration and rehabilitation, we systemically compared the ecological profits among three harness measures, viz., a rough restoration (Treatment I), a refined restoration (Treatment II) , and a restoration by closing hill land (Treatment III) in Hekou, Ninghua, Fujian, compared with that with no-treatment (control), based on an overall investigation on soil anty-erosion, soil fertility, productivity, nutrient cycling, energy, carbon sequestration and biodiversity. An effort was also input on the exploration of a restoration mechanism in order to direct the future practice.The results were showed following:1. The soil antierodibility of different treatments was as follows: HI> II > I . Microbe quantity, soil enzyme activity and soil chemical properties were significantly increased in different treatments. The stand biomass of three treatments was in the order of III> II > I, of which more than 90% were accounted for by the tree layers. The stand productivities of the three communities (HI, II, I) were 7.719,6.495 and 0.961t/hm2.a, respectively.2. The nutrient accumulation of three treatment ecosystems was in the sequence of N> K> P> Ca> Mg, and the annual nutrient retention and return could be ranked as: N>K>Ca>Mg>P. The annual nutrient retention, return and uptake of treatment III t were all markedly higher than those of control.3. The mean gross caloric values of stand biomass in different treatment communities were 20.80, 20.16 and 20.03 kJ/g, respectively. The standing crop of energy in the three treatment communities were respectively 8.7, 27.5, and 42.2 times as much as that of the control community (4179.4 kJ.m-2). The annual net production of energy in different communities ranked in the order of HI> II> I>control, the same for the annual energy return and annual energy retention. The rate of transformation of the solar energy was 0.09% (I), 0.61% (II), 0.75% (III), and 0.04% (control), respectively.4. The average C concentrations of the stand biomass in different communities were in the sequence of control> I> II>III. The carbon reserves of the three treatment ecosystems were 8.5, 25.6, and 37.6 t/hm2, respectively. The annual carbon assimilation were respectively 397.64 , 2650.39, and 3029.88kg/hm2 ?a, amounts equal to 1458.01, 9718.10, and 11109.56 kgCO2.hm-1 .a-1.5. The values of the a -diversity indices (DSH , DGI , DMc , PIE, and OD) could be ranked as: III>II> I >control, and the P -diversity index between different communities was the sequence of control-III> I -Decontrol- II > I -II>II-III>control- I . The PCA analysis indicated an order of restoration degree as: III> II > I >control.In a conclusion, the stage of degradation an ecosystem endures has an important impact on the ecological restoration. Different treatments must be taken according to the degraded stage of an ecosystem, and actions must be taken before an ecosystem becomes severely degraded if a less costly restoration is expected. |
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