Effects Of Land Use Types On The Biodiversity Of Winter Active Collembola In The Sanjiang Plain

Land use change is one of the most important parts of global change, and directlyaffects biodiversity world widely. Sanjiang Plain is the largest concentrated area offreshwater wetlands in China, while large-scale reclamation of wetland significantlyaffects the local climate and ecosystem function. Collembola is one of the three largestsoil organism groups in soil, and play an important role in soil material and energyrecycles. The winter of Sanjiang Plain last nearly six months, during which almost all thesoil animals including collembolans are inactive, while some species of Collembola areactive in winter with the adaptation to cold temperatures. By placing pitfall traps in theground and within the snow profile and making direct in-field observations on the snowsurface in wetlands, reclaimed soybean fields and reclaimed forest plantations from2011to2013, we investigated the species of winter-active collembolans in Sanjiang Plain ofChina, studied the effects of land use changes on the biodiversity, abundance andcommunity structure of collembolans in winter during the period of snow cover, andstudied the winter activities of collembolans in different land use types and the jumpingand migrating behaviour and the migration potential of winter-active collembolans.In total3465individual of collembolans were captured by pitfall traps on the groundand identified to8species from6families. Desoria sp.1, Desoria sp.2and Desoria sp.3were the three dominant species. Land use changes do not significantly affect winteractive Collembolan biodiversity, while significantly affect Collembolan abundances andcommunity structures, the abundance of collembolans in wetland> soybean field> forestplantation. The frequency of Desoria sp.3in soybean field and forest plantation significantly higher than in wetland, while the frequency of Desoria sp.2in soybean fieldand plantation significantly lower than in wetland. Land use change significantly affectthe density of collembolans on the snow surface, wetland=soybean field> forestplantation. Land use change significantly affect the abundance of collembolans within thesnow profile, wetland> soybean field> forest plantation.The activities of collembolans were affected by land use types, sampling time andtemperatures in snow environments. The densities on the snow surface and abundanceswithin the snow profile were higher in the land use type where the abundance werehigher under snow cover; Collembolan activities were mostly affected by winter seasons,the abundance increased from early winter to late winter with a peak at March, after whenthe abundance decreased sharply; the density of collembolans on the snow surface andabundance within the snow profile reached their highest values at the peak activity period;the densities of collembolans on the snow surface fluctuated according to the supraniveanand subnivean temperatures; commonly, the highest values were found in the middle ofthe day with the highest temperatures.The daily densities of collembolans on the snow surface increased first and thendecreased as time changes, which was significantly affect by supranivean temperatures.Generally, the densities were zero before0700h and after1800h in a day and werehighest between1400h and1500h, the highest densities were119individuals/m2onthe snow surface in wetland,152individuals/m2in soybean field, and64individuals/m2in plantation. The densities of collembolans on the snow surface decreased fromMarch22nd to28th, and only a few collembolans were found on the snow surface afterMarch26th. The abundances of collembolans within the snow profile were also affectedby the supranivean temperatures but were not significantly affect by the fluctuations oftemperatures. The abundances of collembolans within the snow profile decreased fromMarch22nd to28th, and only a few collembolans were found within the snow profileafter March24th. All the collembolans active on the snow surface and within the snowprofile were affected by temperatures; no collembolan was active when the temperaturewas too low in the evening.All the three dominant species of Collembola found on the snow surface in theSanjiang Plain were found performing jumping and migrating behaviors. The migration of Collembola was consisting of directional jumps and short crawls between landing andthe next jumping. The three dominant species performed remarkable jumping abilities inone single step, nearly about20-40times distance to their own body lengths. Thejumping abilities were different according to the species, and were affected by thetemperatures, the structure of the snow surface and the level of winds. Collembolansceased jumping when the temperature is relatively low and the wind is strong. Eachcollembolan jumped in a certain direction, but no mass migration phenomenon was foundon the snow surface. All the collembolans could migrate in straight lines, but themigration direction was not exactly the same as the jumping direction thanks to thedirection of the wind. The migration efficiency was high with an average speed of10-30m h-1, so an approximately of about200m migration distance was possible for anindividual in a day, and it was estimated that an individual of Collembola can migrate3km during the whole winter (i.e. the whole year, without the consideration of growingseasons).