| Understory plants is an important part of plantation ecosystem.It plays an important ecological function in maintaining soil fertility of woodland and water conservation, but also to cultivate the target species compete with water and nutrients, therefore, research understory in plantation has been taken seriously. Nitrogen(N) and phosphorus(P) is the most important restrictive elements in forest ecosystem, and interaction between each other, the combined effect of plant growth and the stability of ecosystem. Currently, more and more research about nitrogen and phosphorus fertilizer on absorbing nutrient and forest trees productivity, but little about understory plant diversity and its nutrient dynamics. We choose the typical middle-age hills and mountains fir plantation as the study site object, in 2011, with two kind of levels of N added(5 and 10 g m-2 a-1), a level of P added(5 g m-2 a-1), N and P addition together and control a total of 6 treatments 5 replication completely randomized block in situ field study; in 2012 and 2013 growing season and non-growing season survey understory plant diversity and biomass in the determination; in 2013 growing season and non-growing season randomly collected eight major understory plant leaves or underground parts of plants in 30 plots, N and P contents were measured; understory plant diversity, biomass, nutrient conditions change after evaluation and main understory plant nutrient response pattern and the Inner Association, provide a scientific basis for Chinese fir understory vegetation management and response atmospheric N deposition. The major results as following:(1) The first year after fertilization, phosphorus fertilization increased the understory plant species richness, evenness index, Shanon-Wiener index, nitrogen fertilizer had no significant effect; the second year, in response to both understory plant diversity of nitrogen and phosphate fertilizer processing not significant. Two years growing season and non-growing season understory plant biomass were no significant differences between the different fertilization treatments. Meanwhile, the discovery of the second growing season understory plant biomass was significantly positively correlated with species richness, a significant negative correlation with uniformity. Inferred, light conditions determine the spatial distribution pattern of understory plants is a key factor determining ecological factors understory plant diversity and productivity. Just change the nutrient supply in the short term impact of the understory plant diversity, estimates and nutrient availability can not only promote the growth of understory plants, but also to enhance the growth rate of Chinese fir and change the spatial distribution of canopy, thus affecting understory light distribution. Therefore, the effects of fertilization on understory vegetation and ultimately had to act together in response to the target trees.(2) Understory plants of different nutrient content of nitrogen, phosphorous and interaction of different response. Wherein the nitrogen increase Clerodendrum cyrtophyllum, Cibotium barometz, Adinandra millettii, Loropetalum chinensis and Syzygium grijsii leaf nitrogen content in growing season, increase non-growing season Cibotium barometz and Rubus corchorifolius leaf nitrogen content; improved Clerodendrum cyrtophyllum, Loropetalum chinensis and Dicranopteris dichotoma growing season leaves phosphorus content; P fertilizer increase Dicranopteris dichotoma growing season nitrogen content, increased Dicranopteris dichotoma leaf nitrogen content in growing season and non-growing season; improve Uncaria Woodwardia, Adinandra millettii, Loropetalum, Dicranopteris, Syzygium grijsii and Dicranopteris dichotoma growing season phosphorus content in leaves, improve Uncaria, Cibotium barometz, Adinandra millettii and Dicranopteris leaves phosphorus content in non-growing season. Furthermore, nitrogen and phosphate fertilizer for Dicranopteris,Loropetalum and leaf nitrogen content of Rubus corchorifolius leaf nitrogen content in the non-growing season; phosphorus content of Uncaria, Loropetalum, Dicranopteris and raspberry leaves growing season, non Woodwardia phosphorus content growing season there was a significant interaction. Obviously, understory plant nutrient content of the response pattern of the overall performance of the growing season fertilization, in response to ferns and evergreen plants sensitive than non-growing season sensitive than deciduous plants, phosphate fertilizer response is stronger than the strength of the response to nitrogen fertilizer.(3) Nitrogen increase N/P ratio Clerodendrum cyrtophyllum and Loropetalum chinensis in growing season, improve Clerodendrum cyrtophyllum and Rubus corchorifoliusleaves non-growing season N/P ratio; P fertilizer reduces Clerodendrum cyrtophyllum, Dicranopteris dichotoma, Loropetalum chinensis, Rubus corchorifolius and Uncaria rhynchophylla growing season leaves N/P ratio, lower Dicranopteris dichotoma, Clerodendrum cyrtophyllum, Cibotium barometz, Dicranopteris dichotoma and Uncaria rhynchophylla leaves non-growing season N/P ratio. Furthermore, nitrogen and phosphate fertilizer for the growing season Loropetalum chinensis and Clerodendrum cyrtophyllum, Rubus corchorifolius leaves non-growing season N/P ratio of the interaction is significant. Obviously, understory plant N/P ratio is mainly controlled by fertilizer, indicating that the plantation may be relatively abundant nitrogen, phosphorus relative lack of ecosystems.In summary, the response of Chinese Fir Plantation hilly red zone understory plants fertilization varied. The main differences in nutrient content understory plants to fertilization response pattern suggests that fertilizer plants will affect the forest resources in the capture of competition, thereby changing the composition and community characteristics of understory plant species, but in the short term and understory plant biodiversity changes in productivity is mainly determined by the heterogeneous spatial pattern of light and other resources. The results also suggest that further study of diversity and biomass of understory plants to be selected for a number of key species Long Term Monitoring. |
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