| Sphagnum wetlands in subtropical mountains own very important ecological values.In addition to their general ecological functions concerning carbon sequestration,hydrological adjusting and biodiversity maintenance and protection like other peatlands,they also act as headstreams of some important rivers.However,human activities have recently caused severe destruction and degradation of these Sphagnum wetlands,leading to reduced performance of ecological functions,which emphasizes the urgent need for restoring these wetlands.Until now,research on the Sphagnum wetlands restoration are mainly conducted on the low altitudes of cold and temperate zones in high latitude of the Northern Hemisphere,making the restoration technique can not be well applied to restore the Sphagnum wetlands in subtropical mountains with high altitudes.Based on the field and greenhouse experiments on the high-altitude mountains in western Hubei,China,we studied the effects of microenvironment(including hydrological microenvironment,microclimate environment,and nutrient microenvironment)on the growth of Sphagnum palustre—the key species in subtropical mountain regions and the underlying mechanisms.In addition,through the combination with specific engineering measures,both a series of optimal microenvironment parameters and standards for engineering measures were determined.The main conclusions are:(1)Both the microtopography types and the gradient within a given microtopography affected the tissues water content in S.palustre through changes in water table,thereby impacting the growth of S.palustre.In subtropical mountains of China,microtopography reshaping is not essential for the successful recolonization of S.palustre,however,reducing the height difference and slope gradient within the microtopography can be favorable for S.palustre growth.Microtopographies that maintained height difference within 10 cm with gentle slope,and water table within-10 cm but are not flooded are the best conditions for S.palustre growth.(2)Both the mulch types and mulch density affected the growth of S.palustre through influences on its microclimate environment(including temperature and humidity,and light intensity).In subtropical mountains,mulching with one layer of shading net with 70%shading coefficient is best for S.palustre growth.The straw mulch that commonly used in traditional restoration work was not the only option.Compared with straws,which are scarce in subtropical mountains,the stalk of corn and the shading net,which either the main local crops or can be easily bought from local market,are the better choice for S.plaustre growth after transplanting.(3)Fertilization-and substrate-induced changes in nitrogen and phosphorus contents underlie different patterns of S.palustre growth.In addition,Fertilization-and substrate-induced changes in p H probably also underlie different patterns of S.palustre growth.Except for peat,which is used as the only substrate in traditional in situ peatlands restoration technique,the yellow-brown soil,which is widely distributed in subtropical mountain regions,is also the substrate suitable for S.palustre growth,mainly because its favorable nutrient content and its acidic environment that was close to the original habitat.These results allowed for Sphagnum wetlands restoration on large,less restrictive scales.In addition,the growth of S.palustre was limited by phosphorus availability not nitrogen availability,with the optimal phosphorus addition being 0.2?0.5g m-2year-1 and capitula phosphorus content being approximately 2 mg g-1.In the short term,nitrogen addition did not significantly affect S.palustre productivity in peat,but negatively affected S.palustre productivity in the yellow-brown soil,mainly by inhibiting the length growth,promoting the decomposition and decay,inhibiting the photosynthesis by stimulating other epiphytes growth which resulted in increased competition for light resource.(4)The common peatland restoration method using the upper parts(usually within 10 cm)of S.palustre as transplanted materials is practical and has no destructive effects on the source S.palstre populations in the areas where they are collected.However,considering both the growth efficiency and protection on source populations,a planting method using only capitula may be a better choice for Sphagnum restoration.(5)Changes in the growth environment of S.palustre resulted in its changes in the growth pattern.S.palustre could took place both lateral expansion and longitudinal elongation in the relatively favorable environment;while only focused on the lateral expansion with increasing number of capitula in the relatively harsh environment.At the early transplanting stage on the bare surface,maintaining a stable high water table condition can promote the lateral expansion of S.palustre,which in turn would accelerate the formation of dense hydrological adjustable S.palustre carpets,thereby further contributing to a virtuous cycle of S.palustre growth.Therefore,of the Sphagnum wetlands restoration techniques,water management plays a decisive role in the early transplanting stage of Sphagnum and needs to be emphasized.This research would provide both theoretical basis and practice guidance on the protection and restoration of Sphagnum wetlands in subtropical mountains.Moreover,it also has the important practical significance for establishing a sustainable production of S.palustre and thereby speeding up the poverty-reduction in subtropical mountains. |
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