| The karst rocky desertification area has high exposed bedrock,discontinuous soil,shallow soil layers and the development of dual three-dimensional structures.Water deficit induces drought stress,the ecological environment is fragile,and economic development lags behind.In recent years,with the rocky desertification control and regional economic development,the cultivation of economic fruit forest and the development of grassland animal husbandry have been carried out in many places,however,due to structural defects of forest-shrub-grass,extensive management of water and nutrients and continuous planting of economic forests which caused that soil fertility declined,productivity gradually decreased and economic benefits continued to decline.Therefore,it is necessary to carry out research on ecological restoration and forestry industry comprehensive management techniques,cultivate mixed forests with multi-layered and different-aged to coordinate ecological niches and resource levels,maintain soil nutrient balance promote forest-shrub-grass structure optimization and function efficiency,realize the synergy and trade-off between economic benefits,ecological benefits and social benefits and push the region out of poverty.This paper comprehensively uses a combination of geography,ecology,botany,agronomy,biochemistry and other multidisciplinary knowledge,taking Zhenfeng-Guanling demonstration area with middle-intensity rocky desertification in Huajiang and Salaxi demonstration area with potential-light rocky desertification in Bijie as the study area,we have analyzed the spatial distribution patterns of soil nutrients,the biomass,growth characteristics and nutrient content of different tissues and organs of typical economic plants in different grade rocky desertification land from 2015 to 2017,discussed the ecological restoration and forest industry comprehensive management techniques under different grades of rocky desertification based on the soil nutrient balance under different vegetation types and integrated the technology system of ecological restoration and forest industry comprehensive management in the rock desertification area.1.There was no significant difference in bulk density of surface soil between Huajiang demonstration area and Salaxi demonstration area(P?0.05),the average value of which was 1.01g/cm~3 and 1.07 g/cm~3,respectively,however,the soil bulk density increased with the increase of soil depth,and the soil bulk density in the transition zone from 10-20 cm to 20-30 cm changed the most,nearly 0.1 g/cm~3,and the bulk density of soil layer under 40 cm gradually stabilized which was 1.15 g/cm~3.the soil bulk density increased first and then decreased with the increase of rocky desertification levels in the different grade rocky desertification,and the soil bulk density of the light rocky desertification land was the highest with an average value of 1.08 g/cm~3.2.The TOC and AP of soil in the karst plateau-gorge were lower than the karst plateau-mountain,the TP content was opposite and there was no significant difference in other nutrient contents.In general,the soil nutrient content in rocky desertification areas was high,among which the TOC,TN,TP and AN content were all in level I or level II national standards for soil nutrients,the TK and AK content were moderate,most of them are in level III or level IV,and the AP content of soil was extremely low,mostly less than 5 mg/kg,and the effective rate was less than 0.5%.However,the change rule of soil nutrient in the rocky desertification regions were more consistent,the effect of soil nutrient concentration was obvious in the rocky desertification areas,the soil nutrient content decreased first and then increased with the degree of rocky desertification deepening,the soil nutrient content in the light rocky desertification area was the lowest,the soil nutrient content in the non-rocky desertification was high and the soil nutrient content,the soil nutrient content in the intensity rocky desertification area was significantly higher than other grade rocky desertification(P?0.05).3.The C content of average nutrient content in different plants in rocky desertification areas was highest and the N content was lowest,N and K content were different,the average content of nutrient elements for Lonicera japonica Thunb,Hylocereus undatus and Pennisetum sinese was C?N?K?P,the average content of nutrient elements in other specie was C?N?K?P.The contents of essential nutrients in different organs of different species varied greatly,but the nutrient contents in leaves and fruits were higher,accounting for 2%-4%of the dry matter of organs,and the essential nutrient content of branches was relatively small,the nutrient content in the branches of arbor-shrub was higher than that of mature arbor-shrubs.The enrichment coefficients of soil nutrients in different organs of plants were mostly expressed as N?P?K,and only Carya cathayensis peels and Hylocereus undatus stalks were different.4.The plant biomass in the rocky desertification area was greatly influenced by the age of trees and the plant species,and the biomass increased with the age of the trees.The overall performance of plant species was mature arbor?shrubs?young arbors,the distribution pattern of biomass mainly shows that the biomass of arbor-shrub is mostly distributed on branches,the specific performance was Tectona grandis(87.2%)?Morus alba(72.4%)?Rosa roxburghii(68.3%)?Carya cathayensis(64.2%)?Zanthoxylum Bungeanu(59.0%).The change rule of nutrient reserves and biomass of plant organs in rocky desertification areas are consistent,but it is not proportional to biomass,the storage characteristics of different nutrient elements in different species are consistent with the average content of nutrient elements,that is,the nutrient reserves of Lonicera japonica Thunb,Hylocereus undatus and Pennisetum sinese are C?K?N?P,and the nutrient elements reserves of other species are C?N?K?P.5.There was a significant difference in the nutrient content of vegetation litter in the rocky desertification area(P?0.05),the nutrient content of the Rosa roxburghii,Lonicera japonica,Carya cathayensis,Morus alba and Broussonetia kazinoki was high,which was 26.25 g/kg,25.39g/kg,23.21 g/kg,21.66 g/kg and 21.13 g/kg respectively,and Tectona grandis litter had the lowest nutrient content,which was 8.65g/kg.Compared with the two study areas,the nutrient content of vegetation litter in the Salaxi demonstration area was relatively high.The nutrient cycling rates of different vegetation ecosystems were concentrated between 10%and 25%,the overall performance was that the arborous species had lower nutrient cycling rates,and the nutrient cycling rate of the shrub-rattan plants was relatively high,and the nutrient cycling rate of Lonicera japonica Thunb was highest,reaching 25.5%.The loss rate of soil nutrient of economical vegetation ecosystem in rocky desertification area was relatively high,most of which was above50%,the overall characteristics was showed that grassland?fruit forest?timber forest,among which showed that Pennisetum sinese(97.7%)?Dactylis glomerata(92.8%)?Hylocereus undatus(89.2%)?Morus alba(86.8%)?Zanthoxylum Bungeanu(84.2%)?Broussonetia kazinoki(84.0%)?Rosa roxburghii(79.0%)?Lonicera japonica(79.0%)?Tectona grandis(45.9%).6.According to the unique niche conditions in the rocky desertification area and the relationship between the nutrient balance of forest-shrub-grass,this paper was put forward space allocation and nutrient regulation technology,such as Zanthoxylum Bungeanu+Lonicera japonica/Arachis hypogaea,Carya cathayensis+Rosa roxburghii,Hylocereus undatus+Medicago sativa,Rosa roxburghii+Dactylis glomerata,Morus alba+Dactylis glomerata,Zanthoxylum Bungeanu+Broussonetia kazinoki,and key technologies such as efficient planting of Pennisetum sinese and soil moisture conservation.Based on the climate conditions of the north and south subtropics,the natural environment and socioeconomic conditions of different rocky desertification grades,this paper was put forward ecological conservation and forest industry composite management technologies the potential rocky desertification which was suitable to cool climate zones and warm climate zones,optimal allocation of forest-shrub-grass and high efficiency production technology of the light rocky desertification,fast-growing and high efficient planting of forest-shrub-grass and artificial induction and restoration technology of medium rocky desertification,artificial restoration and close hillsides technology of intensity rocky desertification,which were integrated technology system of ecosystem restoration and forest industry comprehensive management in the karst rocky desertification area. |
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