Release Characteristics Of Silicon And Other Elements During The Litter Decomposition Of 12 Tree Species In Northern Fujian Province

Litter is an important source of biological silicon.The difference of release rate of silicon from different tree species during the decomposition of litter is of great significance to the silicon cycle in forest ecosystem.In this study,the litter of 12 evergreen broad-leaved forest species was collected in the common-garden of Fujian Sanming Forest Ecosystem and Global Change National Observation and Research Station.And the samples were determined for Si and C,N,P,K,Ca,Mg,Al and other elements in the litter of which was got by Field litter decomposition bag method.Analyzed the dynamic changes of Si and other 7 elements and studied the release characteristics of plant silicon content and other chemical components during the situ decomposition process of 12 tree species.The correlation between plant silicon and its chemical components and the decomposition rate of litter has been preliminarily established.The main conclusions were as follows:(1)There are significant differences in the decomposition rate of litter among 12 tree species: arranged from largest to smallest as Castanopsis carlesii(Hemsl.)Hay >Sapindus mukorossi Gaertn.> Liriodendron chinense(Hemsl.)Sargent > Liquidambar formosana Hance > Michelia macclurei Dany > Elaeocarpus decipiens Hemsl >Cinnamomum camphora(L.)Persl > Pinus massoniana Lamb > Schima superba Gardn.et Champ > Cunninghamia lanceolate(Lamb.)Hook > Lindera communis Hemsl >Photinia fraseri Dress.The time variation of litter decomposition of 50% and 95% of different species of evergreen broad-leaved forest in this area was estimated to be0.65?1.78 a and 2.81?7.69 a,respectively.It shows that the decomposition rate of various tree species has small differences in the early stage,but there are significant differences in the late decomposition rate among the tree species.(2)The content of silicon among 12 tree species of litter varies greatly,and the content is not lower than that of individual beneficial plants such as K and Mg.The litter contents of 12 species were: 2.00±0.22g/kg(Pinus massoniana Lamb),2.74±0.23g/kg(Cunninghamia lanceolata(Lamb.)Hook),5.17±0.49g/kg(Sapindus mukorossi Gaertn),3.07±0.15g/kg(Liriodendron chinense(Hemsl.)Sargent),6.25±0.06g/kg(Liquidambar formosana Hance),7.61±0.22g/kg(Lindera communis Hemsl),6.10±0.61g/kg(Castanopsis carlesii(Hemsl.)Hay),7.03±0.35g/kg(Cinnamomum camphora(L.)Persl),5.08±0.15g/kg(Elaeocarpus decipiens Hemsl),7.13±0.39g/kg(Schima superba Gardn.et Champ),1.08±0.06g/kg(Photinia fraseri Dress),8.62±0.17 g/kg(Michelia macclurei Dany).After 365 d of decomposition,the cumulation coefficients(NAI)of silicon in the litter of 12 tree species were220.47%(Pinus massoniana Lamb)? 169.17%(Cunninghamia lanceolata(Lamb.)Hook)?51.74%(Sapindus mukorossi Gaertn)?120.07%(Liriodendron chinense(Hemsl.)Sargent)?77.02%(Liquidambar formosana Hance)?29.38%(Lindera communis Hemsl)?54.57%(Castanopsis carlesii(Hemsl.)Hay)?56.17%(Cinnamomum camphora(L.)Persl)?89.63%(Elaeocarpus decipiens Hemsl)?79.61 %(Schima superba Gardn.et Champ)?195.62%(Photinia fraseri Dress)?41.43%(Michelia macclurei Dany),respectively;Four tree species(Pinus massoniana Lamb,Cunninghamia lanceolata(Lamb.)Hook,Liriodendron chinense(Hemsl.)Sargent and Photinia fraseri Dress)had a net accumulation of silicon during the decomposition of litter,and the remaining eight tree species(Sapindus mukorossi Gaertn,Liquidambar formosana Hance,Lindera communis Hemsl,Castanopsis carlesii(Hemsl.)Hay,Cinnamomum camphora(L.)Persl,Elaeocarpus decipiens Hemsl,Schima superba Gardn.et Champ,Michelia macclurei Dany)had a net release of silicon during the decomposition process of litter.The decomposition process of the litter of 12 species of trees showed that the order of the contribution of plants to the biogeochemical silicon cycle in forest ecosystems is as follows: evergreen broad-leaved tree species > deciduous broad-leaved tree species >evergreen coniferous tree species.(3)The release characteristics of nutrients were different in the decomposition of litter in 12 species.N,P,Si,K,Ca,Mg,Al and lignin were enriched to varying degrees in litter residues of 12 tree species.Coniferous trees are easy to form acidic environment when decomposing,which is beneficial to the enrichment of Si,K and Al elements.The release of Ca between different tree species depends on the substrate quality determined by tree species factors and its habitat,and the decomposition rate of litter is significantly related to the initial content of Ca.Climate conditions in the same period of rain and heat in the middle subtropical zone are beneficial to the disintegration of refractory components in litter and the rapid loss of mineral elements such as Mg elements.(4)Si/N,lignin,C/N and lignin/Si,as the most important factors affecting the decomposition process of litter,explained 60.60% of the total variation.The mass residue rate was significantly positively correlated with C,Si/Al and Si/Al,and significantly negatively correlated with Si,Al,Ca,Si/C and Si/P.It shows that the mineral elements have a significant impact on the decomposition of litter during the decomposition process,especially the three mineral elements of Si,Al and Ca.(5)The correlation between Si and Al,Ca,Si/C,and Si/P,dry mass residue rate reached a significant level,and the correlation with Si/Al showed a significant negative correlation.The correlation with the content of C element showed a very significant negative correlation.It can be seen that Si can promote the absorption of Al and Ca elements in the litter of forest tree species,and high-silicon plants can absorb Al in the soil to form chelates,which can slow the soil from being poisoned by Al.It also shows that the increase of Ca can promote the absorption and utilization of Si by plants.