| Litter decomposition is an important process in the nutrient cycle of terrestrial ecosystems,with litter matrix quality,external environment and decomposition interaction affecting the rate of litter decomposition.The home-field advantage of litter decomposition is another important manifestation of the biological role in controlling the decomposition characteristics in addition to substrate quality and physicochemical environment,which can affect the accuracy of simulations by 8%.Therefore,the home-field advantage may potentially affect the nutrient return efficiency of plantation forests by influencing the process of litter decomposition in the silvicultural process.However,there are few studies on the performance of the home-field advantage of litter decomposition of the main afforestation species in subtropical China.Therefore,this study investigated litter mass loss,nutrient release,lignin and cellulose degradation,and the dynamics of microbial biomass related to litter in different plantation types using litterbags decomposition method for three major plantation tree species(Pinus massoniana,Cunninghamia lanceolata,and Quercus variabilis)in the subtropical region of China.The study aimed to explore the effects of substrate quality,climatic zone,and decomposition time on the formation of home-field advantage of litter decomposition,and provide scientific basis for the selection of plantation tree species and nutrient management in subtropical plantation forests.The main results are as follows:(1)Through regression simulation using the Olson negative exponential decay model,in contrast,the six species of litter decomposed fastest in Subtropical South of C.lanceolata or Q.variabilis plantations and slowest in Subtropical North of Q.variabilis plantations(excluding SP).The 50% and 95% decomposition time of the six species of litter decreased by 2.11 and 9.12 years respectively.In addition,the decomposition constant k of NP and SP in the three types of Subtropical South plantations was higher than that in the three types of Subtropical North plantations.During the entire decomposition period,the mass loss rate of the six species of litter per 30 days was higher in the T1 and T2 periods,and decreased gradually with the progress of decomposition time.(2)During the decomposition process,the carbon concentration,lignin concentration,and cellulose concentration of the six species of litter in different plantation types exhibited an exponential decrease trend,while the nitrogen concentration and phosphorus concentration exhibited an exponential increase trend.The overall carbon release rate of the six species of litter was highest from T0 to T1;the overall nitrogen release rate was highest from T2 to T3 or from T3 to T4;the overall lignin degradation rate was highest from T2 to T3;and the overall cellulose degradation rate was highest from T1 to T2.The carbon release rate of the six species of litter gradually decreased every 30 days,and was generally higher in the T1 and T2 periods;the nitrogen release rate of SP and SQ gradually decreased every 30 days,and was generally lowest in the P.massoniana plantations in Subtropical North from T3 to T6;the phosphorus release rate of NQ,SP,SC,and SQ gradually decreased every 30 days,and was generally highest in the C.lanceolata or Q.variabilis plantations of Subtropical South from T2 to T6;the cellulose degradation rate of the six species of litter gradually decreased every 30 days,and was generally higher in the T1 and T2 periods.During the experiment,nitrogen,phosphorus elements,and lignin were enriched in the litter.The nitrogen and phosphorus enrichment rate of NP every 30 days gradually decreased,with the highest value observed in the T1 period.The lignin enrichment of the six species of litter occurred mainly in the T1 and T2 periods,and the lignin enrichment rate was generally highest in the C.lanceolata plantation of Subtropical South and lowest in the P.massoniana plantation of Subtropical South.(3)As decomposition time progressed,the overall carbon to nitrogen ratio,carbon to phosphorus ratio,nitrogen to phosphorus ratio,lignin to nitrogen and lignin to phosphorus ratios of the six litter species in the different plantation types gradually decreased.The carbon-to-nitrogen ratios of NP and SQ,the carbon-to-phosphorus ratio of NQ,and the lignin-to-nitrogen ratios of NC and SC were highest in the Subtropical Southern of Q.variabilis plantations,followed by Subtropical Southern of C.lanceolata plantations and Subtropical South of P.massoniana plantation during T2-T5.The carbon-to-phosphorus ratio of NP during T1-T5 and NC during T1-T4 and the lignin-to-phosphorus ratio of NP during T3-T5 and SP during T2-T5 were highest in the Subtropical Southern of P.massoniana plantation,followed by Subtropical Northern of Q.variabilis plantations,Subtropical Southern of Q.variabilis plantations,and Subtropical Southern of C.lanceolata plantations.(4)The microbial biomass carbon of all six species of leaf litter in different plantation types tended to decrease and then increase with decomposition time,with higher values at T1 and T6 and lower values at T2 or T3.The microbial biomass nitrogen of the six species of litter in different plantation types showed higher values at T4-T6 with the progress of decomposition time.(5)During the entire experiment,there was home-field advantage of 30-day mass loss rate for both P.massoniana and C.lanceolata leaf litter decomposition in the Subtropical Southern and Northern climate zones.No home-field advantage of 30-day mass loss rate was observed for Q.variabilis leaf litter in either the Southern or Northern Subtropical climate zones.However,the home-field advantage of 30-day mass loss rate was observed for all five leaf litter species(except for SP)in different climate zones.Home-field advantage of carbon,nitrogen,phosphorus,lignin,and cellulose release/degradation rates were observed for all six litter species in both the Southern and Northern Subtropical climate zones,as well as in different climate zones.When litter decomposition was carried out between different climate zones,the home-field advantage of nitrogen and phosphorus release,as well as cellulose degradation,for P.massoniana litter showed a decreasing trend in incidence,while the home-field advantage of carbon release and nitrogen release for C.lanceolata litter showed an increasing trend,and the frequency of home-field advantage for mass loss and phosphorus release did not change.The home-field advantage of mass loss,phosphorus release,and lignin degradation for Q.variabilis litter showed an increasing trend in incidence.(6)The 30-day mass loss rate,carbon and nitrogen release rate of the six species of litter are highly positively correlated with litter lignin concentration,lignin-to-phosphorus ratio,microbial biomass carbon concentration,and average temperature and humidity of the plantation.They are highly negatively correlated with litter nitrogen concentration and lignin-to-nitrogen ratio,and significantly negatively correlated with microbial biomass nitrogen concentration.The 30-day phosphorus release rate and cellulose degradation rate of the six species of litter are highly positively correlated with litter nitrogen concentration and lignin-to-phosphorus ratio,and highly negatively correlated with litter nitrogen concentration and lignin-to-nitrogen ratio,and significantly negatively correlated with microbial biomass nitrogen concentration.The home-field advantage of litter carbon-to-nitrogen ratio on the 30-day nitrogen and phosphorus release rates and cellulose degradation rate of the six species of litter are highly positively correlated.The home-field advantage of 30-day mass loss rate,lignin and cellulose degradation rates of the six species of litter are highly positively correlated with litter lignin-to-phosphorus ratio.The home-field advantage of 30-day carbon release rate of the six species of litter is highly negatively correlated with litter lignin-to-phosphorus ratio.Therefore,it can be seen that the mutual placement of different types of litter in different climatic zones and plantation types changes the decomposition environment of the litter,and the related microbial biomass also changes dynamically,thereby changing the litter’s quality loss,carbon,nitrogen,and phosphorus release,lignin and cellulose degradation,and corresponding home-field advantage.Therefore,further understanding the characteristics of home-field advantage on litter decomposition with changes in substrate quality and climatic zones can not only deepen our understanding of material cycling and energy flow in forest ecosystems,but also provide important scientific basis for sustainable management of forest ecosystems. |
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