Effects of different legume species and densities on arbuscular mycorrhizal fungal communities in a karst grassland ecosystem.

Legumes can increase nitrogen (N) input to soil via N2 fixation, and arbuscular mycorrhizal fungi (AMF) can colonize legumes, which further promotes the acquisition of nutrients such as phosphorus (P). Nevertheless, little is known about how different legume species or planting densities affect soil AMF communities. We measured soil AMF abundance, diversity, and community composition in two legume species that had been planted at two densities in a karst grassland. Five treatments were used: control (CK), Amorpha fruticosa at 1.5 × 2 m density (AFD1), A. fruticosa at 1 × 1 m density (AFD2), Indigofera atropurpurea at 1.5 × 2 m density (IAD1), and I. atropurpurea at 1 × 1 m density (IAD2). The results showed that A. fruticosa plots were significantly richer in Redeckera spp., while I. atropurpurea plots were richer in Septoglomus. AMF abundance in AFD1, AFD2, and IAD1 was significantly higher than in CK, but AMF abundance in IAD2 was significantly lower than that in the other treatments. AMF richness and Chao1 estimator in AFD1 were significantly higher than in CK. Funneliformis, Septoglomus, and Acaulospora were significantly more abundant in IAD2 than in the other treatments. The interaction between legume species and density had a significant effect on AMF abundance and community composition. AMF abundance and diversity were significantly negatively and positively correlated with available P and microbial biomass N, respectively. These results suggest that different species and densities of legumes may increase available N, which could improve AMF abundance and alleviate soil P deficiencies. Planting A. fruticosa or I. atropurpurea at a low density may be an effective method to increase AMF colonization of roots, and thus, nutrient transport in karst grasslands.

Xiao D ，Tan Y ，Liu X ，Yang R ，Zhang W ，He X ，Wang K ... -  《-》

Nitrogen fertilizer and Amorpha fruticosa leguminous shrub diversely affect the diazotroph communities in an artificial forage grassland.

Soil diazotrophs have been known to be essential in biological nitrogen (N) fixation, which contributes to the sustainability of agricultural ecosystems. However, there remains an inadequacy of research on the effects of different N inputs from N fertilization and from symbiotic N fixation associated with legumes on the diazotroph communities in agricultural ecosystems. Hence, we investigated the variations in diazotroph abundance and community composition as well as the soil properties with different N inputs in the Guimu-1 hybrid elephant grass cultivation on karst soils in China. We conducted six different N treatments: control, Amorpha fruticosa planting at a spacing of 1.5 × 2 m (AFD1), A. fruticosa planting at a spacing of 1 × 2 m (AFD2), N fertilization (N), A. fruticosa planting at a spacing of 1.5 × 2 m with N fertilization (AFD1N), and A. fruticosa planting at a spacing of 1 × 2 m with N fertilization (AFD2N). Our results showed that the interaction between sampling time and N fertilization significantly affected the diazotroph abundance. In July, the diazotroph abundance significantly decreased in the N fertilization treatments: N, AFD1N, and AFD2N, compared to that in the control. The richness and Chao1 estimator of diazotrophs significantly increased in AFD2N and AFD1 correspondingly in December and July, relative to those in the control. Co-occurrence networks showed species-species interactions with high negative correlations that occurred more in the control than in the N input plots. The N input from N fertilization and legume planting directly increased the ammonium N and nitrate N and consequently affected the dissolved organic N and pH of the soil, thereby altering the diazotroph abundance and richness. Our findings demonstrated that both N fertilization and legumes could reduce the interspecific competition among diazotroph species by providing greater N availability in the forage grass.

Xiao D ，Liu X ，Yang R ，Tan Y ，Zhang W ，He X ，Xu Z ，Wang K ... -  《-》

[Various effects on the Abundance and Composition of Arbuscular Mycorrhizal Fungal Communities in Soils in Karst Shrub Ecosystems].

Liang YM ，Su YR ，He XY ，Chen XB ，Hu YJ ... -  《-》

Arbuscular Mycorrhizal Fungi Alter Plant and Soil C:N:P Stoichiometries Under Warming and Nitrogen Input in a Semiarid Meadow of China.

Mei L ，Yang X ，Cao H ，Zhang T ，Guo J ... -  《-》

Mechanistic understanding of interspecific interaction between a C4 grass and a C3 legume via arbuscular mycorrhizal fungi, as influenced by soil phosphorus availability using a (13) C and (15) N dual-labelled organic patch.

Arbuscular mycorrhizal fungi (AMF) can improve plant nutrient acquisition, either by directly supplying nutrients to plants or by promoting soil organic matter mineralization, thereby affecting interspecific plant relationships in natural communities. We examined the mechanism by which the addition of P affects interspecific interactions between a C4 grass (Bothriochloa ischaemum, a dominant species in natural grasslands) and a C3 legume (Lespedeza davurica, a subordinate species in natural grasslands) via AMF and plant growth, by continuous 13 C and 15 N labelling, combined with soil enzyme analyses. The results of 15 N labelling revealed that P addition affected the shoot uptake of N via AMF by B. ischaemum and L. davurica differently. Specifically, the addition of P significantly increased the shoot uptake of N via AMF by B. ischaemum but significantly decreased that by L. davurica. Interspecific plant interactions via AMF significantly facilitated the plant N uptake via AMF by B. ischaemum but significantly inhibited that by L. davurica under P-limited soil conditions, whereas the opposite effect was observed in the case of excess P. This was consistent with the impact of interspecific plant interaction via AMF on arbuscular mycorrhizal (AM) benefit for plant growth. Our data indicate that the capability of plant N uptake via AMF is an important mechanism that influences interspecific relationships between C4 grasses and C3 legumes. Moreover, the effect of AMF on the activities of the soil enzymes responsible for N and P mineralization substantially contributed to the consequence of interspecific plant interaction via AMF for plant growth.

Liu H ，Wu Y ，Xu H ，Ai Z ，Zhang J ，Liu G ，Xue S ... -  《-》