Litter Decomposition Across Altitude Gradient

As one of the key processes that account for a huge majority of the biological carbon processing on planet Earth,decomposition of organic matter,such as litter,is responsible for huge amounts of the carbon dioxide returned to the atmosphere,and responsible for the formation of humic substance that contribute to soil fertility as well as the long term storage of carbon.However,it occurs mainly on or below ground.As such,it is largely out of sight.And also,it can be affected by multiple factors.As a variety of environmental types in a small spatial range,the altitudinal gradient is an ideal place for studying the response mechanism of litter decomposition to environmental change.In this study,in order to explore the effect of environmental factors on the decomposition dynamics of litter,¹⁵N-labeled litter of Quercus variabilis was used for decomposition and was placed on four different altitudes of Lushan and Baotianman respectively.The ¹⁵N-labeled litter and soil under litter bag were collected and analyzed regularly.After one year litter decomposition,results showed that temperature and soil microbe were the main factors affecting the litter decomposition rate along the altitudinal gradient of Lushan and Baotianman.The results were as follows:(1)As the elevation of both mountains rised,the soil p H value showed no obvious tendency with the altitudes of the two mountains.With the altitude increasing of Lushan,the soil urease,sucrase and cellulase activities gradually increased.However,none of the above enzymatic activities showed obvious changes along the altitudes of Baotianman.In addition,with the elevation increasing,the total PLFA content of soil microorganism on Lushan tended to decrease firstly and then increase,while it was contrary on Baotianman.(2)In the first 3 months,the decomposition rate of litter was the fastest.After 1 year's decomposition,the loss rate of the litter on the two mountains has shown a decreasing trend with increased elevation,except for the highest elevation of Lushan.(3)After 1 year's decomposition,the contents of C,K,C/N,and abundances of ¹⁵N in litter on the two mountains showed a decreasing trend,while the contents of N,Ca,Fe,Al and S increased.Besides,the contents of P and Mg showed differences on the two mountains and at different elevations.On the whole,there was no obvious link between the changes of these elements contents and the altitude.(4)After 1 year's decomposition,the release rate of each element in litter on Lushan showed K>Mg>P>C>S>Ca>N>Fe>Al,and it was showed K>Mg>C>P>S>N>Ca>Fe>Al on Baotianman,the two trends are basically consistent.Among them,K had the highest release rate,followed by Mg,in addition,Fe and Al have been in a state of enrichment.Furthermore,with the increase of Baotianman's altitudes,the net release rate of C,N,P,K,Mg and S in litter decreased,and the net enrichment of Ca,Fe and Al increased.(5)Along the altitudinal gradient,temperature and soil microbe were the main factors that affected the litter decomposition rate.