Mature temperate woodlands are commonly dominated by ectomycorrhizal trees, whereas understory plants predominantly form arbuscular mycorrhizal associations. Due to differences in plant-fungus compatibility between canopy and ground layer vegetation the 'mycorrhizal mediation hypothesis' predicts that herbaceous plant establishment may be limited by a lack of suitable mycorrhizal fungal inoculum.We examined plant species data for 103 woodlands across Great Britain recorded in 1971 and in 2000 to test whether herbaceous plant species richness was related to the proportion of arbuscular mycorrhizal woody plants. We compared the effect of mycorrhizal type with other important drivers of woodland plant species richness.We found a positive effect of the relative abundance of arbuscular mycorrhizal woody plants on herbaceous plant species richness. The size of the observed effect was smaller than that of pH. Moreover, the effect persisted over time, despite many woodlands undergoing marked successional change and increased understorey shading.This work supports the mycorrhizal mediation hypothesis in British woodlands and suggests that increased abundance of arbuscular mycorrhizal woody plants is associated with greater understory plant species richness.
Receftyed 20 May !asg, i,q fin=! fo,-18 &!y !99g, a~ep!ed for p&!ica!icn 2A Jn!y 1995 Abstract. We have investigated p-and n-doped distributed Bragg reflector stacks (DBRs)'in several material systems in order to evaluate their use in multi quantum weii CMCiWJ micra resonator moduiaiors. we nave shown inai over 80% reflectivity can be obtained using 12 periods in a p-type Gao.351no.~Aso.,5Po.25/lnP or Alo.osGao.3sln0.~3A~/Ab.~81n0.52A~. Laltice-matched n-doped Gao.471no.53AdlnP and Gao.4,1no.53As/Al~.4sln~.52As DBRs are shown to give 98% reflectivi with only absorption edge of lattice-matched GalnAs to enable its use in 1.55 wm DBRs. 20 periods. We have found that n doping of greater than 1 x loT8 cm-2 .shifts '. the
Synthesis.Habitat heterogeneity measures included the presence of coppicing, open areas such as 35 rides and riparian zones and the difference between species assemblages in different plots in the 36 woodland. Results suggest that to maximize vascular plant diversity, woodlands should be managed 37 for heterogeneity. In addition, the increase in richness with exposure to surrounding natural habitats 38 suggests that woodlands should be large and connected. This implies that if possible current 39 woodlands should be increased in size, rather than creating new smaller disconnected sites. 40
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