| Cunninghamia lanceolata is a special tree species of China, as well as one of the most important fast-growing timber species, which has 2000 years cultural history. Currently, the traditional intensive management mode regard its principal purpose as timber production, fast-growing and high-yield, which evidently fostered nowadays predatory, intensity, soil-nutrition consumed cultivation of Cunninghamia lanceolata plantation. As a result, a dark bloom of this characters has emerged, the sustained goal has already created a series of ecological problems, including Cunninghamia lanceolata plantations’simple structure, the loss of biodiversity, serious erosion, soil degradation, inferior ability of resisting disasters, especially for the soil degradation of Cunninghamia lanceolata plantation duing to the successive planting, may potentially threaten, even constraint Cunninghamia lanceolata plantations’sustainable management. Summarizing domestic and foreign failure, new theories and technologies of plantation management, we may effortlessly found that the serious biodiversity loss of Cunninghamia lanceolata plantation may account for the different ecological problems, thus, how to restore and reconstruct the biodiversity of Cunninghamia lanceolata plantations are urged to be disposed during the sustainable management of Cunninghamia lanceolata plantation.Forest litter, which bridge the connection between ecosystem above-ground and underground, playing a key role in the material circulation and nutrition balance of forest ecosystem. Consequently, it can act as a good medium to reveal the relationship between species diversity and soil ecosystem function. Besides, in terrestrial ecosystem, soil microorganism dominate the biogeochemical cycle, as well as mediate the core ecological process including litter decomposition, soil carbon sequestration, soil nutrient cycling. Soil microorganism regulates the process of decomposition, promotes soil nutrient cycling with its community structure, abundance, activity, and litter decomposition in turn shift microorganism’s community structure, abundance, activity with its chemical-varied composition. Thus, litter decomposition and variation of microorganism community structures and functions may affect and restrain each other.In this paper, field pot experiments were applied, five different species including Cunninghamia lanceolata(S), Michelia macelurei(H), MangLietia yuyuanensis(R), Phoeba bournei(N), Schima superba(M) were chosen, as well as 1-5 species leaf litter were mixed to substitute the species diversity, probing into the impacts of leaf litter diversity on soil carbon、 nitrogen forms and soil microbial diversity, revealing the mechanisms of Cunninghamia lanceolata plantations’ species diversity with soil ecosystem functions, together with the idea of restoring and reconstructing the biodiversity of Cunninghamia lanceolata plantations, optimizing mixed species, sustainable management of Cunninghamia lanceolata plantation. This experiment were designed as two different parts, including single species leaf litter decomposition and mixed species leaf litter decomposition, the leaf litter diversity exerted different impacts on relevant indicators of surface soil at the end of 16 months.The results are as follows:(1) Total phosphorus content as well as total potassium content of soil were didn’t shaped by single species leaf litter or mixed species leaf litter decomposition, while, available Phosphorus and Potassium were considerably altered by both of them. Moreover, available Phosphorus of soil covered by broad leaf litter only as well as leaf litter diversity mixed, especially for the litter mixed groups, including SHR, SHN, SHRN, SHRNM were all higher than that covered by S only.(2) There were no significant difference of total carbon and nitrogen content among the groups of leaf litter decomposed along, while, soil total nitrogen content appears gradient response to the leaf litter mixed decomposition, with a regular order of 5 species mixed>4 species mixed>3 species mixed>2 species mixed. Similarly, soil C/N appeared opposite gradient response to the leaf litter mixed, with a regular order of 5 species mixed<4 species mixed<3 species mixed<2 species mixed< S.(3) Soil dissolved organic carbon (DOC) presented not significant difference (p>0.05) among leaf litter decomposed along, but significant difference (p<0.05) of dissolved organic nitrogen (DON). Soil DOC of leaf litter mixed decomposition presented extremely significant (p<0.01) difference, with a order of SHN>SHRNM>SHRN>SR>SRN>SM>SHR>S>SN>SH>CK.(4) In the experiments of single species leaf litter decomposition, S decreased soil DOC, broad leaf litter all increased soil DOC. H, N, M leaf litter decomposed along respectively presented 2.53,2.45,2.72 times as much DOC as the soil of S, and H, N, R, M leaf litter decomposed along respectively presented 3.72、2.88、1.88、2.08 times as much DON as the soil of S. In the experiments of mixed species leaf litter decomposition, soil DOC appeared a significant difference, presenting a order of SHR>SH> SM>SHRN> SN> SHRNM>CK> SHN> S> SH> SRN, while soil DON didn’t, with a order of SHR>SN>SH>SR> SHRN>S>CK> SM> SHN> SRN>SHRNM.(5) The cellulose activity of soil covered with single species leaf litter, were all higher than that of CK, but R, N, M leaf litter decomposed alone were all lower than that of S, respectively as much as 58.2%,38.8%,55.1% of S. On the contrary, the invertase、acid phosphatase、peroxidase activity of soil covered with broad leaf litter, were all higher than that of S. Cellulose、polyphenol oxidase activity of soil covered with mixed species leaf litter were all lower than that of S, whereas invertase、acid phosphatase together with peroxidase activity were all lower than that of S. Soil urease presented no regular variations both in leaf litter decomposed alone and mixed leaf litter decomposition.(6) The contents of total microbe PLFA together with bacterial PLFA、fungi PLFA、gram-positive bacteria PLFA、gram-negative bacteria PLFA of soil presented extremely significant (p<0.01) difference among mixed leaf litter decomposition. The addition of S leaf litter didn’t increased the biomass of soil bacterial、fungi、actinomycetes, but the addition of mixed leaf litter, especially for SHR、SN、SHN、SHRN、SHRNM, profoundly increased the abundance of three kinds of microbes than that of S and CK.(7) The addition of S leaf litter along presented a highest ratio of soil G+:G, indicating that the proportion of soil G+ were increased on the condition of S leaf litter decomposed along and the diversity of leaf litter mixed may foster soil G+ thriving. The addition of SN leaf litter considerably increased the proportion of soil bacterial, whereas, other leaf litter diversity groups as well as S, increased the proportion of soil fungi, especially for S、SR、SHR、SHN considerably shifted the microbe of soil from bacterial-domination to fungi-domination.(8) The Shannon-wiener indicator of soil microbe PLFA presented a range from 2.06 to 2.39, and a order SHR> SHN> SN> SHRN> SRN>S>SR>SHRNM> SM> SH>CK, indicating that appropriate leaf litter mixed groups may benefit the diversity of microbial community, but leaf litter mixed diversity didn’t necessarily signify the diversity of microbial community.(9) Principal components analysis (PCA) showed that the primary four components can account for 86.39% variations of soil microbial community diversity, demonstrated that primary four components can well explain major variations of soil microbial community diversity information. PCA and cluster analysis all proved that the litter diversity groups can be divided into three Sasses, the prevailing Sass, including the groups of SN、SHR, presented a higher content in all different PLFA, the sub-optimal Sass, including the groups of SHN、SHRN、SHRNM、SH、SM, presented a higher content in cy 19:0, i 17:0, the inferior Sass, including the groups of CK、S、SH、SRN, presented a lower content in 18:2ω6,9、18:1ω9c、9Me18:0、10Me19:0.(10) 24 environmental variables (including soil factors and litter quality) were involved, to make a redundancy analysis (RDA) of environmental variables effect on microbial communities in soil covered by mixed tree species litter, the results showed that 24 environmental variables could account for 83.8% information of microbial community diversity, and the remarkable variables were cellulose of litter (P=0.005), total phosphorus of soil (P=0.004), lignin of litter (P=0.018), exchange acidity of soil (P=0.01), soil pH (P=0.013), ammonium nitrogen of soil (P=0.047) were respectively account for 13.5%,11%,6.9%,7.1%,5.1%,4.5% soil microbial communities diversity. Moreover, cellulose of litter, ammonium nitrogen of soil, lignin of litter mainly explained the fungi and actinomycetes communities diversity, whereas, exchange acidity of soil, soil pH mainly explained the actinomycetes communities diversity.(11) The average utilization capacity of carbon sources for microbial communities in soil covered with single leaf litter, presenting a order of R> H> N> S> M>CK, and more than 2 species leaf litter mixed were all induce a higher capacity than that of less than 2species leaf litter mixed. Comparing with the addition of S leaf litter only, the addition of broad leaf litter will considerably promoting the carbon sources of phenolic acids higher utilization by soil microbial communities, no matter in broad leaf litter decomposition only or leaf litter diversity mixed decomposition.(12) The addition of broad leaf litter only as well as addition of diversity-mixed leaf litter were all induce higher Shannon-wiener indicator of carbon sources utilization than that of addition S leaf litter only and CK, and the addition of SR leaf litter would induce highest Shannon-wiener indicator (3.35).(13) PCA of carbon sources utilization indicated that, carbohydrates and amino acids my be the major carbon sources for microbial communities of soil added single leaf litter, polycarboxylic acids, arbohydrates and amino acids my be the major carbon sources for microbial communities of soil added diversity-mixed leaf litter. RDA results indicated that MBC (P=0.002)、ammonium nitrogen of soil (P=0.002)、MBN (P=0.002)、Cellulose (P=0.002)、soil moisture content (P=0.004)、DOC (P=0.008)、exchangeable aluminum (P=0.002) were the remarkable environmental variables which could respectively response 21.3%,18.6%,13.2%,9.9%,7.7%, 6.1%,7.2% diversity information of carbon sources utilized by microbes in single leaf litter added soil. Exchangeable aluminum (P=0.002)、C/N (P=0.002)、nitrate nitrogen (P=0.002) soil moisture content (P=0.002)、total phosphor (P=0.002)、total nitrogen (P=0.002) peroxidase (P=0.004)、MBN (P=0.002) were the remarkable environmental factors which could respectively response 13.4%,10.9%,9.3%,7.9%,7.4%,7.0%,5.1%,4.8% diversity information of carbon sources utilized by microbes in diversity-mixed leaf litter added soil.(14) The results of high-throughput sequencing showed that, the number of reads passing quality control for every soil sample was 10029-105099, unifying the sequencing depth, the reads passing quality control can be classified as 2786-3400 OTUs, with a order of SR>SHRNM> SHN> SHRN> SN> SHR>S.OTUs、Chao1、Ace numbers all indicated that the addition of diversity-mixed leaf litter would induce higher bacteria abundance than that of addition of S only.(15) The range of Shannon-wiener indicator of bacteria communities was 6.4923-6.6970, with a order of SHR>SR> SHRN>SHRNM> SHN> SN>S, indicating that the addition of diversity-mixed leaf litter would induce higher bacteria communities diversity than that of addition of S only.(16) The reads passing quality control of bacteria genes for 7 soil samples could be identified to more than 23phylums,108 families,180genus, and presented no significant difference in phylums composition, but a significant difference in families and genus composition. Actinobacteria, Proteobacteria, Chloroflexi, Acidobacteria, Bacteroidetes, Firmicutes were the abundance dominant phylums. Comparing with the addition of S leaf litter only, the addition of diversity-mixed leaf litter would considerably decrease the abundance of some dominant phylums in S soil, such as Chloroflexi, Acidobacteria, TM7, meanwhile, increase the abundance of some inferior phylums in S soil such as Spirochaetes, Thermotogae, Synergistetes, Actinobacteria(17) The cumulative abundance of 9 superior phylums, the results of PCA indicated that primary four components can account for 96.85% variations of soil bacteria communities diversity, PC1 can explained 42.82% variations of variations, presented a high correlation with Acidobacteria (r=-0.7648,p<0.01), Bacteroidetes (r=0.9445.p<0.01), Gemmatimonadetes (r=-0.9445,p<0.01). PC2 can explained 29.66% variations of PLFA, presented a high correlation with Chloroflexi (r=0.7603, p<0.01)、TM7 (r=0.9428, p<0.01)、Armatimonadetes (r=0.6658, p<0.01)(18) RDA results indicated that available phosphorus、Cellulose、DOC、total carbon、were the remarkable environmental variables which could respectively account for 40.4%、26.8%、14.1%、 10.5%、5.9% variations of soil bacteria communities.(19) Comparing with the addition of S leaf litter only, the addition of diversity-mixed leaf litter, including SHN, SHRNM, SHR, SHRN, would considerably improve the soil ecological functions, while, SH and SM all deteriorate the soil ecological functions. |
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