Study On The Ecological Characteristics Of Drepanostachyum Luodianense In Guizhou Karst Area

Karst habitat is a kind of fragile ecology environment,which has followed typical characters: shallow and less soil,high rate of bare stone,serious soil erosion,low soil nutrient content and bad growth condition.Drepanostaehyum luodianense only distributes and grows well in adverse Karst regions,such as Luo Dian,Ping Tang and Chengguan of Chang Shun district in Guizhou province.To explore the growth adaptability,analyze the endangered mechanism and provide the theoretical foundation of the protection and exploitation of D.luodianense,species selection and reasonable collocation in the process of rocky desertification control.Based on the ways of field investigation, comparative analysis and system analysis,the adaptability characteristics of D.luodianense was studied in the Karst microhabitat,modular,cloning,population,community and so on.The results showed that:1 The habitat of D.luodianense can be divided into six kinds of microhabitats:soil surface,stone surface,stone ditch,stone crevice,stone slot,stone cavern.D.luodianense grows in the other 5 microhabitats except stone surface.For the growth of D.luodianense,soil surface is the optimal,stone cavern is the worst,while there is no significant difference in other three microhabitats.So,it can be divided into three types:stone surface,stone-soil combination surface and soil-stone combination surface.The main utilized microhabitats should be stone ditch,stone crevice and stone slot when D. luodianense is used to forestation.2 The optimum LAI of D.luodianense is 7.1893.The net photosynthetic rate curve of D. luodianense is bimodal,to be accompanied by significant "nap" phenomenon,and which two peaks appear at 12:00 and 15:00.The determination of light response curve shows that the light compensation point of D.luodianense is 13.57μmol·m^-2·s^-1,while the light saturation point reach up to 1200μmol·m^-2·s^-1.And all those proved that D.luodianense is a shade-tolerant bamboo species.3 The growth of branch and leaf modular of D.luodianense in isolated habitats is better than that in forest edge and inside forest.But branch length in forest edge is better than that in isolated habitats and forest habitats.With the increase of tree ages,there are different fluctuations in the average branching angle at all levels,but the average angle is about 35°.With further increase of tree ages,both the average branch angle and the height of natural pruning increases gradually,while the average number of branches in stems decreases.The clonal modular growth of D.luodianense tends to K-strategy in forest edge and isolated habitats,while it is R-strategy in inside forest habitats.4 Clonal architecture of D.luodianense appears obvious plasticity under different soil moisture circumstances,which is mainly reflected in the spacer length and branching intensity.The branch angles of the clonal ramets of D.luodianense are relatively fixed in four kinds of angles mainly:15°,40°,70° and 110°.D.luodianense can adjust foraging behavior through clonal plasticity.As a kind of clonal plant,D.luodianense has an obvious characteristic of physiological integration.5 There is a series of adaptive feature of D.luodianense in population level.It has high shoot-emergence number,high mortality and low bamboo grown-up rate.The shortage of nutrition is the main reason for the high mortality.In the distribution of D.luodianense,the age structure of the population is growing,but it tends to be stable.There is a great relationship between the distribution pattern and the sampling scale.With the increase of research scale,the clonal distribution pattern changes from random to cluster-based type,and the clonal ramets distribution pattern is an enhanced cluster-based type.The population regulation of D.luodianense belongs to density dependence type, which is affected by clonal density and clonal ramets density.The environment capacity of D. luodianense is about 100/m².6 D.luodianense is the dominant species and the only constructive species in this kind of community which families and genera composing are quite scattered and reflect significant tropical features and obvious transition characteristics.The species diversity indexes of D.luodianense community are close to 1 at all levels,thus,it is a relatively stable community.There are rich viable seeds in the community's soil seed bank.7 D.luodianense can adapt well and influence the community environment markedly where it distributes.In the same environment,D.luodianense community not only can obviously improve the soil's physical and chemical properties but also can effect in soil and water conservation better than the shrub community and grassland.8 There are three possible reasons that D.luodianense is an endangered species.Firstly,it has been excessive lopped and utilized.Secondly,it has special characteristics of clonal growth and the soil space is narrow in Krast region.Thirdly,it needs strict climate conditions.9 As the species for restoration and reconstruction in Karst ecosystem,D.luodianense can be used to treat rocky desertification in the south and southwest of Guizhou provinces,most parts of Yunnan provinces,Guangxi provinces,Chongqing and Hunan provinces.