| New emerging ecological stoichiometry aims to study the balance of multiple chemicalelements by studying stoichiometry of the main chemical elements (C, N, P, etc.) to reveal therelationship between the characteristics and behaviours of organisms and ecosystems, whichcould link different levels of individuals, community and landscape together to reveal thegrowth characteristics of plants and the important role of limited factors. This method mayopen a new approach to quantitatively describe the relationship between productivity and mainchemical elements in Phyllostachys pubescens forest. Thus, in this study, in mainPhyllostachys pubescens distribution areas (Fujian, Jiangxi, Zhejiang, Hunan, etc),bamboo-soil-litter was considered as research objects to study C, N and P content and theirstoichiometry in Phyllostachys pubescens forest of different ages (1-6years), differentproductivity levels (I:30000±1000kg·hm-2·a-1, II:34000±1000kg·hm-2·a-1, III:37000±1000kg·hm-2·a-1, IV:42000±1000kg·hm-2·a-1, V:47000±1000kg·hm-2·a-1) and differentdistribution areas, further to reveal the stoichiometry characteristics of individual, communityand regional distribution of bamboo forest, and to illustrate the relationship betweenstoichiometry and productivity levels in Phyllostachys pubescens forest, which could providebasic theory for scientifical management. The main results are:1. Individually, C, N, P content and C:N, C:P, N:P of same organ showed significantdifference with the increase of age. Productivity, the nutrient quantity and ratios differed fromdifferent ages, which was consistent to “growth rate” hypothesis. N and P content increasedfirst and then decreased with the increasing age. C:N and C:P were both highest at age5, N:Pwas lowest at age3, and was highest at age5, indicating3-year old Phyllostachys pubescenshad strong metabolism, rizhome expansion, high potential productivity, and N supply mighthad significant effect on3-year Phyllostachys pubescens forest; N:P was highest at age5, indicating bamboo at age5had highest holding efficiency of N, harvesting bamboo at this time,P utilization efficiency was highest.2. The difference of plant and soil C, N and P content was significant in Phyllostachyspubescens forest of difference productivity levels at stand level, but the difference was notconsistent between plant and soil C:N, C:P, N:P. Plant C:N, C:P, N:P of was not statisticallysignificant difference, while soil C:N, C:P, N:P was statistically significant difference. Thecorrelation between plant and soil was not significant.(1) Plant C, N and P content was statistically significant different in Phyllostachyspubescens forest of different productivity levels, but the difference of C: N, C: P, N: P did notreach a significant level. N:P of leaves was12.60-13.69in Phyllostachys pubescens forest ofdifferent productivity levels, and coefficient variation was12.31%, indicating stoichiometry ofmain elements fluctuated in a small range along with different productivity levels inPhyllostachys pubescens forest, which was in line with “internal stability” hypothesis.Meanwhile, N: P <14suggested N was the limited element in Phyllostachys pubescens forestin study areas.(2) Distribution of soil organic matter, N, P, H-N and A-P showed significant changes, andthe difference of ratios of stoichiometry reached a significant level. N:P was4.50-13.89, whichdecreased with the increase of productivity. Changes of soil N:P was consistent with thechanges of productivity synchronously, which was more sensitive compared to leaves, andcould be the potential indication index to the degradation of Phyllostachys pubescens forest.The relationship between soil stoichiometry and plant stoichiometry was not significant, butthe coefficient leaf stoichiometry was higher that of soil stoichiometry, indicating the changesof soil nutrient content and stoichiometry affected bamboo nutrient content and theirstoichiometry to some extent.(3) The number of the significant correlation between nutrient cycling characteristic andplant, soil was9for N:P,8for C:P, and2for C:N, respectively, in Phyllostachys pubescensforest of different productivity levels, showing nutrient cycling characteristic wassignificantly affected by C and P. 3. Regionally, the stoichiometry characteristic of main nutrients showed obviousdifferentiation.(1) Change law along with latitude: leaf N and P content and N:P increased with theincrease of latitude, and C:N and C:P decreased with the increased of latitude; litter N content,C:P and N:P increased with the increase of latitude, and P content, C:N decreased with theincrease of latitude. Soil C, N content, C:P and N:P increased with the increase of latitude, andP content and C:N decreased with the increase of latitude.(2) Change law along with longitude: leaf N and P content deceased with the increasinglongitude, and C:N, C:P and N:P increased with increasing longitude; litter in N, P contentincreased with increasing latitude, and C: N, C: P and N: P decreased with increasing longitude;soil layer C, N, P content and C: P, N: P decreased with increasing longitude, and C: N ratioincreased with increasing longitude.(3) Regional distribution of ecological stoichiometry characteristics in Phyllostachyspubescens forest: leaf C: N, C: P and N: P were25.32,143.36and5.66, respectively; litter C:N, C: P and N: P were30.89,593.16, and19.20, respectively; soil C: N, C: P and N: P were12.71,54.24and4.27, respectively. When N:P<16, Phyllostachys pubescens forest was limitedby N; while14<N:P<16, Phyllostachys pubescens forest was limited by both N and P; andN:P>16, Phyllostachys pubescens forest was limited by P. Data in our study indicatedPhyllostachys pubescens in China was mainly limited by N, seldom by P.In summary, in the individual level values of the major ecological stoichiometry inPhyllostachys pubescens was in line “growth rate hypothesis”; in the community level thevalues were in line with “internal stability” hypothesis, showing obvious differentiation onregional scale. Leaf N: P illustrated the growth of Phyllostachys pubescens forest was mainlylimited by N, rather than P, and soil N:P had strong indication to productivity changes inbamboo forest. Based on current management level, bamboo forest could meet the basic Pdemand, thus N input and management should be enhanced. However, increase P input in Plimited areas could alleviate N limitation and increase stand productivity. |
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