| Plantation is the main source of China's timber materials,but because of the defects such as low productivity,poor quality,etc,people from all walks had attached great importance to the scientific promotion of plantation ecological benefits.Natural forest is considered to be an ecosystem with complex species composition,rich biodiversity.And it has stabler ecosystems than plantation.Comparing the difference between plantation and natural forest in aspects of stand composition,site condition,etc,which is benefical to perfect the technologies in breeding forest scientifically,give full play to ecological benefits and ultimately lay the foundation for the sustainable management of forest.This paper selected three plantations dominated by native tree species?i.e.,Castanopsis hystrix,Michelia chapensis,and Michelia maudiae?and natural secondary forests as the research objects in the subtropical area.Comparing the understory species characteristics,soil physical-chemical properties,soil seed bank,and stability among these four forest stands.Health assessment were also evaluated by using the method of principal component analysis in terms of relevant indicators which were mentioned above,in order to identify the properties that potentially restricted the development of forests and provide the scientific basis for the development ecological benefits in forest.The main conclusions are as follows:?1?The effect of the CCH method was reasonable,It showed significant difference at 0.01levels and provided favorable conditions for the growth of understory vegetation to promote their growth.The structure of plantation was simpler than natural secondary forest.Natural secondary forest was rich in diameter structure?the same to age structure?,which was more suitable for succession to stable communities.?2?The number of understory vegetation species in the three stands showed natural secondary forest?61 species?>Michelia plantation?43 species?>Castanopsis hystrix plantation?41 species?.Natural secondary forest was the most abundant species in three stands,but it was no obvious advantages in the number of subjects?the understory vegetation in natural secondary forest belonged to 35 families,it belonged to 34 families in Michelia plantation,and in Castanopsis hystrix plantation belongs to 33 families?.The species composition of the plantations was significantly different from that of natural secondary forests.The dominant species of plantation was Maesa japonica and Piper puberulum,but in natural secondary forest was Machilus kwangtungensis and Castanopsis fissa.In the shrub layer,The Shannon-Wiener diversity index showed Natural secondary forest?1.95±0.40?>Castanopsis hystrix plantation?1.61±0.51?>Michelia plantation?1.23±0.30?and in the herb layer it showed Castanopsis hystrix plantation?2.55±0.50?>Michelia plantation?2.53±0.31?>Natural secondary forest?2.34±0.38?.The shrub layer diversity index was inversely related to the herb layer.The stability result of understory vegetation in three stands showed the plant community was stable state in natural secondary forests.The complexity of species diversity and plant community structure were both positively correlated with the stability of community stability and determined the maintenance of community stability,the development of community succession.?3?At the soil depth of 0?20 cm,the content of organic matter,total nitrogen and total phosphorus was characterized by Castanopsis hystrix plantation(34.74±13.29 g·kg-1,1.56±0.49 g·kg-1,and 0.43±0.13 g·kg-1)>Michelia plantation(28.20±9.97 g·kg-1,1.27±0.34g·kg-1,and 0.30±0.10 g·kg-1)>natural secondary forest(22.78±8.52 g·kg-1,1.07±0.33 g·kg-1,and 0.25±0.04 g·kg-1).At the soil depth of 20?40 cm,the soil organic matter,total nitrogen and total phosphorus in plantation and natural secondary forest still showed Castanopsis hystrix plantation(24.22±7.51 g·kg-1,1.23±0.32 g·kg-1,and 0.42±0.11 g·kg-1)>Michelia plantation(21.80±8.34 g·kg-1,1.04±0.28g·kg-1,and 0.29±0.11 g·kg-1)>natural secondary forest(16.15±6.42 g·kg-1,0.83±0.23 g·kg-1,and 0.24±0.04 g·kg-1).Soil physical-chemical properties of three plantations were significantly different except for the nitrate nitrogen?P<0.05?.Soil organic matter content was closely related to understory species diversity?P<0.05?.The herb layer had the significant correlation with nitrogen and phosphorus contents?P<0.05?,and was more susceptible to changes of soil physical-chemical properties than shrub layer.?4?The seed storage of seed banks in the three forest stands was poor,and the species composition of the soil seed bank in different forest was mainly the shrub plants.There were no significant differences in different plantations.The similarity coefficient soil seed bank and the aboveground vegetations in plantation was lower than that in natural secondary forest.The result showed:the similarity between soil seed bank and aboveground vegetation is enhanced with the succession of community,and all of these were lower than those of other scholars.?5?The method was used by selecting 24 indicators which could represent the forest productivity,soil nutrient,stand structure and restoration and renewal ability,in order to evaluate the plantation health assessment.The results showed the average health score of the plantation was natural secondary forest?2.24?>Michelia plantation?-1.00?>Castanopsis hystrix plantation?-1.24?.The factors which affected the health of forest stands were soil p H,soil K,P content,shrub herb diversity index and richness index,stand age structure and seedling number,and it was mainly concentrated in soil nutrient and stand structure.It proved that maintaining the health and stability of the plantations should focus on enriching the plantation structure and maintaining soil nutrients,thereby promoting the maximization of the ecological benefits of the plantation. |
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