Plant community composition, soil nutrients, tussock morphometrics, C. rubra root colonisation, soil microbial PLFA and NLFA in 75 plots that vary in invasive Calluna vulgaris density, Tongariro National Park, New Zealand

We studied invasion by an ericoid mycorrhizal host plant (Calluna vulgaris L., heather) in alpine tussock grasslands in New Zealand. We investigate the effects of increasing C. vulgaris density on the plant and soil microbial community and on mycorrhization in the dominant native species (Chionochloa rubra Z., red tussock), an arbuscular mycorrhizal host. We show that variation in plant community composition among sites was driven by C. vulgaris density. Higher densities of C. vulgaris were associated with a reduced diameter of C. rubra plants and lower densities of neighbouring plant species, especially woody shrubs. Belowground, we show that higher densities of C. vulgaris were associated with lower rates of mycorrhization in native C. rubra and higher abundances of the fungal fatty acid methyl ester (FAME) biomarker but had little effect on the total microbial community biomass, suggesting that increased ericoid mycorrhizal fungal biomass increased the ratio of fungi relative to bacteria in high C. vulgaris density stands.

本研究针对新西兰高山草丛草原中的杜鹃花类菌根（ericoid mycorrhizal）宿主植物帚石楠（Calluna vulgaris L., heather）的入侵过程展开探究。本研究考察了帚石楠密度升高对植株与土壤微生物群落的影响，以及对本土优势物种红穗茅（Chionochloa rubra Z., red tussock，一种丛枝菌根（arbuscular mycorrhizal）宿主）的菌根侵染率的影响。研究结果表明，不同样地间植物群落组成的差异由帚石楠密度主导。帚石楠密度越高，红穗茅的植株直径越小，伴生植物（尤以木本灌木为甚）的种群密度越低。在地下生态层面，研究发现帚石楠密度升高与本土红穗茅的菌根侵染率降低相关，同时伴随真菌脂肪酸甲酯（FAME）生物标志物的丰度上升，但对微生物群落总生物量无显著影响。该结果提示，在帚石楠高密度的群落样地中，杜鹃花类菌根真菌生物量的提升会提高真菌与细菌的生物量比值。