濒危植物裸果木(Gymnocarpos przewalskii)与其伴生种种间联结性及群落稳定性

Community Stability and Interspecific Association between the Endangered Plant Gymnocarpos przewalskii and Its Associated Species

以濒危植物裸果木(Gymnocarpos przewalskii)为研究对象,在安西极旱荒漠国家级自然保护区的南区和北区内分别设置50个样方,基于2×2列关联表,运用方差比率法(VR)、卡平方(χ~2)、联结系数(AC)、点相关系数(PCC)、Ochiai指数(OI)、共同出现百分数(PC)的种间联结分析和M.Godron群落稳定法,分析了裸果木与23种主要伴生种的种间联结性和群落的稳定性。结果显示:北区和南区裸果木与伴生种正联结均多于负联结,但南区VR>1,检验统计量W<χ~2_(0.05,N),群落总体表现为不显著的正联结,而北区VR>1,W>χ~2_(0.05,N),群落总体表现为显著正联结。北区与裸果木极显著正联结的有膜果麻黄(Ephedra przewalskii)、沙蒿(Artemisia desertorum)、霸王(Zygophyllum xanthoxylon)等3种植物,显著负联结的只有泡泡刺(Nitraria sphaerocarpa);南区与裸果木极显著正联结的只有膜果麻黄,无显著负联结物种。南北二区种类倒数累计百分数和累计盖度的比值均远离20/80,群落不稳定,但北区的稳定性好于南区。上述结果表明,极旱荒漠地区只有极少的伴生种与裸果木存在显著种间联结关系,大多数表现为不显著的种间联结关系,因而裸果木趋于独立存活,其群落总体处于不稳定状态。

Gymnocarpos przewalskii is an endangered xerophytes distributed in the desert regions of northern China.In this investigation,based on the 2×2 contingency table,50 quadrats were set in the south and the north district of Anxi Extra-Arid Desert National Nature Reserve respectively.In order to study the community stability and interspecific association between G.przewalskii and its associated species.M.Godron's method,variance ratio(VR),χ~2-test,association coefficient(AC),point correlation coefficient(PPC),Ochiai index(OI)and percentage cooccurrence(PC)was employed in this study.The results showed that:positive association between G.przewalskii and its associated species were more pronounced than negative association both in northern(VR>1,W >χ~2_(0.05,N))and southern district(VR>1,W <χ~2_(0.05,N)),but only southern district had reached significant level.G.przewalskiiis significant positive associated with Ephedra przewalskii,Artemisia desertorumand Zygophyllum xanthoxylonand significant negative associated with Nitraria sphaerocarpain northern district.However,in southern district,there were no significant negative associated species and Ephedra przewalskii is the only species which significant positive associated with G.przewalskii.The community stability in northern district was better than south though the ratios of cumulative inverse of species number to cumulated relative frequency were distinctly different from20/80 in both of the two districts,which indicate instability.In conclusion,few species had significant positive association with G.przewalskii in extra-arid region.Therefore,the population of G.przewalskii tend to be independent and the community was still in unstable state.