| Plant litter decomposition is a crucial driver of carbon and nutrient cycling in ecosystems,therefore playing an important role in maintaining the ecosystem structure and functions therein.Previous studies have found that the plant economics spectrum(PES)can predict the decomposition pattern across woody species via the "after-life effect".Due to the functional,morphological,physiological and structural differences in the various plant organs,the decomposition rates of plant organs vary in their responses to the PES effect.In addition,invertebrates make huge contributions to decomposition,and their feeding preferences toward different plant organs are vastly distinctive.However,there is still a lack of comprehensive understanding of how the interactions of dead plant materials with invertebrates affect the coordination between the decomposition of different plant organs.Moreover,although wood-decaying fungi are one of the main decomposer groups in dead wood decomposition in the early stage,how they and invertebrates jointly affect the interspecific variation in dead wood decomposition rate predicted by the PES still remains unclear.To work out these convoluted relationships,we carried out a long-term plant decomposition experiment in Tiantong Mountain and Putuo Mountain,Zhejiang Province,in which we chose leaves,twigs(2 cm),coarse branches(5 cm)and logs(20 cm)of 41 woody plants representing different resource use strategies(the fast-slow economics spectrum).We measured the functional traits of different plant organs,monitored the mass loss rate of each organ and the dynamics of dominant decomposer animals as well as wood-decaying fungi communities across woody species for a period of 3 years.This study aims to answer the following scientific questions: 1)Whether the decomposition rates of different leaf litters and woody debris(twig)are coordinated in response to the PES effect,and how the invertebrates involved affect the coordination between the leaf litter and woody debris(twig)decomposition;2)Whether the decomposition rates of woody debris of different diameter classes are coordinated in response to the PES effect,and how termitesmediate the PES effect among different diameter classes;3)How do the PES,wood-decaying fungi and termites affect the interspecific variation in the dead wood decomposition rates interactively?The main results are as below:1.Major twig consumers termites and the litter feeder Arippara indicator Walker significantly changed twig and litter mass loss trajectories predicted by the PES,respectively,thereby regulating the coordination between twig and litter decomposition.Specifically,in the initial stage of decomposition,the leaf economics spectrum(LES)and leaf litter mass loss were linearly positively correlated,in other words,the litter decomposition trajectory was predicted perfectly by LES.However,the relationship vanished in the mid-late stage of decomposition,when Arippara indicator Walker larvae appeared.The larvae abundance was linearly positively correlated with the leaf litter mass loss and displayed an inverted U-shaped relationship with the LES.The wood economics spectrum(WES)was linearly positively correlated with twig mass loss.With the increase of decomposition time,the explanatory power of WES on twig mass loss increased.Termite feeding intensity had a linear positive correlation not only with twig mass loss,but also with WES.Further analysis revealed that there was a significant positive correlation between the Arippara indicator Walker larvae abundance and the deviation between leaf and twig mass losses,that is,when the abundance increased,the degree of decoupling between leaf and twig decomposition rates became more dramatic,whereas termite intensity was negatively correlated with the deviation between leaf and twig mass losses,that is,when termite feeding activity intensified,the leaf and twig decomposition rates coupled more closely.2.The WES predicts the interspecific variations in twig,coarse branch and log decomposition;on the other hand,the termite intensity alters the coordination among their decomposabilities.In detail,the WES had positively significant relationships with different diameters wood.The explanatory power of WES on the wood mass losses reached its pinnacle at the early stage in all diameter classes.As the decomposition process went on,the discrepancy between their decomposition patternsbecame larger.Termite intensity was linearly positively correlated with WES and 2cm diameter twig mass loss.In 5 cm diameter coarse branch,the relationship between termite intensity and WES illustrated a liner trajectory in first 12 months,and subsequently transformed into an inverted U-shaped curve in 18 months.There were significant positive correlations between termite intensity,20 cm log mass loss and WES.Further analysis suggested that termite food preference caused termites to change the decomposition trajectories of acquisitive(fast growing)species across diameter classes;the mass loss rate of 5 cm coarse branch of fast growing end was higher than that of 2 cm twigs;in contrast,termites fed less on conservative(slow growing)species and did not change the decomposition trajectory of different diameter classes wood on the slow growing end.Because logs barely started to decompose at that moment,termite feeding intensity and the WES cannot explain the diameter effect on decomposability.This result shows termite feeding intensity interfered with coordination between twig and coarse wood decomposability,but it also had a little impact on diameter effect.3.Wood stem(log)debris has significant WES effect.Termites and wood-decaying fungi abundance was closely related to WES,the termite intensity amplified the impact of wood-decaying fungi on log decomposition.In detail,when the termite intensity was low,the termite consumption volume and wood-decaying fungi intensity(e.g.the wood decaying fungi coverage,the coverage of dominant fungi species,hyphal density,the depth of hyphal invasion)were positively correlated with the WES.In the high termite abundance environment,termite abundance and wood-decaying fungi intensity indices showed inverted U-shaped distributions along the WES axis;log debris volume consumed by termites had a positive relationship with the WES.In addition,when the termite activity intensity was low,the wood-decaying fungi intensity had a synergy with the termite intensity along the WES axis,which in turn,promoted the decomposition of acquisitive end species;when the termite activity intensity was high,the termite consumption volume was the largest in the acquisitive end of WES,which consequently altered the positive relationship between wood-decaying fungi and WES into a negative one.On the whole,the WES was the dominant factor in driving the pattern of log mass loss across woody species.The WES explained much more termite intensity than it did the wood-decaying fungi intensity,and the termite intensity predicted better the wood mass loss than wood-decaying fungi intensity indices did.In summary,this thesis explored the fast-slow economics spectrum effect on the leaf,twig,coarse branch and log mass losses,and the regulatory effects that the dominant invertebrate and wood-decaying fungi decomposers imposed on decomposition process in eastern Zhejiang.Our study suggests the significant“after-life” effects of the PES and diameter difference of woody organs.The coordination between the decomposition trajectories of leaf litter or dead wood debris(twig litter)predicted by the PES differed,owing to the differences in the properties of decomposition substrates,distinctive feeding preferences of invertebrates and the variation in wood-decaying fungi community compositions.The results of this research advance our understanding of the interactive effect of plants and decomposer animals on plant decomposition,and also help to reveal the forest ecosystem carbon and nutrient cycling mechanism in the region as well as provide theoretical support for biodiversity and ecosystem function managements in subtropical forest. |
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