Study On Desert Plant Community Succession And Nutrient Elements Driving

Plant community succession is a varying process that combined lots of ecological processes and factors. However, the unified succession theory and mechanism has not yet been reached due to diverse ecosystem. Ecological stoichiometry, a new theory that dealing with balance between multiple elements and environment and analyzing its impact on ecological processes, provided a research method for succession process from the view of nutrient stoichiometry. Desert vegetation played a crucial role in biodiversity protection and regional ecosystems stability maintenance in arid zone. The studies on succession and ecological stoichiometry of desert vegetation helped reveal the regional diversity process and nutrients drive mechanisms on community succession, which is conducive to vegetation management and restoration, fragile ecosystems conservation and response of desert vegetation to global climate change and other scientific issues.This paper studied the typical desert vegetation characteristics, nutrient stoichiometry of plant leaves and surface soil in the Ebinur Lake wetland national nature reserve, aimed to answer the following questions:(1) What’s relationship between community characteristics and soil water and salt and nutrition, and how the relationship response to succession dynamics.(2) How the nutritional characteristics of desert plant leaves and soil changing along succession stages, as well as the relationship among plant leaves and soil nutrient and soil water and salinity.(3) How the relationship of community characteristics with soil water and salinity, and with soil nutrients. The mainly results achieved as the following:1. Vegetation composition, soil water congtent, soil salinity, and soil organic matter had a close relationship, and all presented certain regular changes along gradient of distant to river; vegetations in studied area were divided to3succession stages according to gradient features of vegetation and soil, including Populus euphratica-Nitraria schoberi-Phragmites australis (SSⅠ). Haloxylon ammodondron Reaumuria soongorica-Salsola collina (SS Ⅱ), and Haloxylon ammodendron-Suaeda dendroides-Horaninowia ulicina (SSⅢ) respectively.2. Rank/abundance pattern and a diversity were significantly different among3succession stages, specifically, Rank/abundance pattern of SS Ⅱ was significantly different from SSⅠ and SSⅢ (P<0.05), and a diversity of SS Ⅱ was significantly lower than SSⅠ and SSⅢ; dissimilarity measure index of β diversity decreased from SSⅠ to SSⅢ community, and similarity index overall increased from SSⅠ to SSⅢ, with SSⅡ decreased slightly, which indicated the similarities of plant composition from SSⅡ to SSIII were improved.3. Community association of each stages were not significant negative, interspecific competition was greater than facilitation; SSⅠ showed the highest competitive intensity, in SSⅡ, competition intensity was similar to facilitation, in SSⅢ, competition intensity was a little stronger than facilitation; interspecies relationship pattern was consistent with community associations, facilitation species pairs were overall increased from SSⅠ to SSⅢ stage, and mutually beneficial effect between species were improved; community stability were slightly improved from SSⅠ to SSⅢ, but each succession stage still in an unstable state.4. Plant organic carbon (C) content decreased slightly from SSⅠ to SSIII stages, C content of species level generally increased from SS I to SSⅢ stages, specifically, Kalidium foliatum, R. soongorica and S. collina etc. were low C content species; both of community and species level nitrogen (N) content decreased from SSⅠ to SSⅢ stage, N limit of plants was aggravated, species of Chenopodiaceae that distributed near to riparian contained higher N content than Leguminous plants indicated the key role of soil water in N circle in studied area; plants in the study area were generally subject to phosphorus (P) limited, and the limitation intensified from SSⅠ to SSⅢ stages; most of the low P content species contained relatively low N content, which indicated that plants tends to limited by both of N and P nutrition along succession process; plants sulphur (S) content in the study area were generally much higher, and significantly different among species. Generally, S-rich species had lower N content.5. Plants in the study area had higher potassium (K) content and moderate magnesium (Mg) content, both of them increased from SSⅠ to SSⅢ; plants had moderate calcium (Ca) content and high sodium (Na) content, plant Ca and Na content decreased from SSⅠ to SSIII; changes of K, Ca, Na and Mg elements along succession stages may be the reflection of plant water uptake strategy adaption, or resistance decline and enhanced photosynthesis; plant ferrum (Fe) content increased significantly from SS Ⅰ to SSⅢ stages, while manganese (Mn), copper (Cu) and zinc (Zn) contents reduced in varying degrees, changes of the4elements along succession stage in overall reflected its auxiliary function in photosynthesis declined.6. Both of C content of community soil (soil that under plant canopy) and controlled soil (soilthat outside plant canopy) declined significant from SS I to SSIII, which mean that improvement of plants to soil nutrient conditions reduced; N content change trend of community soil and controlled soil were similar to soil C,"N fertilizer " effect of vegetation on soil in SSⅠ was significant, but the effect weakened obviously in SS II and SSⅢ; soil in the study area was lack of P extremely, and plants P almost no return to soil; overall soil S content was high in study area, and vegetation cover had no significant effect on the dynamics of soil S.7. Ca, Na and Mg content of community soil decreased significantly along the SS Ⅰ-SSⅢ, while K content increased nonsignificantly,4elements had no significant difference between community soil and controlled soil, which indicated that soil initial K, Ca, Na and Mg content was stable, and vegetation cover had no significant effect on soil K, Ca, Na and Mg dynamic; soil Fe, Mn, Cu and Zn element were overall stable, and had no significant response to vegetation cover except for Zn.8. The average ratio of vegetation C:N, C:P and N:P were22.40,513.66and24.17respectively, which were overall higher than that of similar zone; plants in study area general lack of N and P, and the deficiency state exacerbated with distance to the river increased; controlled soil C:N elevated from SSⅠ to SSⅢ, namely soil N supply reduced, controlled soil C:P and N:P declined from SSⅠ to SSⅢ, which indicated soil in near riparian region that lack of P extremely had transformed to N and P limited in far from riparian region.9. The overall correlation between plant nutrition and soil elements was weak. Positive correlation of soil C and N reduced from SSⅠto SSIII when vegetation covered, while positive correlation of soil C and P improved, correlation among soil C, N and S were also improved in different degree; positive correlation of soil K, Na and Mg intensified from SSⅠ to SSⅢ stage in a whole; soil Ca was significantly negatively correlated with C, N, P in SSⅠ and positively correlated with C, N, P in SSⅡ respectively; conclusively, soil elements correlations were improved under vegetation cover from SS I to SSⅢ, except the correlation of soil C with N and S; the above mentioned indicated that vegetation cover prompted relationship of soil elements more closely.Vegetation cover reduced influence of soil water on soil elements in a whole, particularly the impact on soil C, N, P, S, Ca, Na and Mg; meanwhile, vegetation cover increased the salinity positive influence on soil N, P, S and Mg, but reduced the positive influence on soil C, Ca, Na and K.10. The influence of soil volume water content (SVWC) on diversity variations were not significantly in each succession stage, with the highest R2in SSⅢ, the overall effects of SVWC on diversity were improvement on low SVWC level, and tend to no significant effect or influence on diversity complicated on high SVWC level; impact of soil EC and pH on diversity declined from SS Ⅰ to SSⅢ, plant diversity increased linearly when soil EC less than about12ms/cm and pH below8.3in SSⅠ, however, plant diversity began to decreased as soil EC and pH increased continuingly, influence of soil EC and pH on diversity tend to complicated in SS Ⅱ and SSIII when soil salinity and alkalinity aggravated. In conclusion, SVWC effects on plant diversity improved from SS I to SSIII, while soil EC and pH impacts on diversity decreased.Soil C and N impacts on diversity declined from SS I to SSⅢ; the nonlinear relationship between soil P and plant diversity were complex in SS I, namely diversity changed greatly when soil P content increased, effects of soil P on diversity were peaked in SS Ⅱ. Effect of soil S on plant diversity improved from SS I to SSⅢ, increased soil S lead to plant diversity decreased; influence of soil K on diversity strengthened from SS I to SSIII, relationship of soil K and diversity became complicated when soil K increased more than17.0g/kg; increased soil Na and Mg content overall hinder diversity promotion. In conclusion, impacts of soil C, N and P on diversity weakened from SS I to SSⅢ; relationships between diversity and most of soil elements were complex in SS Ⅱ, and overall tend to complicated when elements content relative high.11. Increase of soil water, salinity, C, N, S, Ca, Na, Mg and Cu generaly lead to enhanced community competitive effect, while increase of soil P, K, Fe, Mn and Zn element contributed to species mutually beneficial; community stability improved nonsignificantly with increase of soil water and salinity, while increasing of soil C, N, P, S, Ca, Na, Mg and Cu elements conduced to community stability, and of them soil P had the most significant effect.