RESUMO
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.
Assuntos
Carbono/metabolismo , Lespedeza/fisiologia , Micorrizas/fisiologia , Nitrogênio/metabolismo , Fósforo/metabolismo , Poaceae/fisiologia , Transporte Biológico , Isótopos de Carbono/análise , Lespedeza/microbiologia , Isótopos de Nitrogênio/análise , Raízes de Plantas/microbiologia , Raízes de Plantas/fisiologia , Brotos de Planta/microbiologia , Brotos de Planta/fisiologia , Poaceae/microbiologia , Solo/químicaRESUMO
Slope aspect is an important topographic factor for a micro-ecosystem environment that may affect macro- and micronutrients in plants and soil. The south-, northwest-, and north-facing slopes were selected to investigate the influence of slope aspect on the concentrations, storage, and allocation of macro- and micronutrients in Artemisia sacrorum on the Loess Plateau in China. The concentrations of available manganese (Mn) in both rhizosphere and non-rhizosphere soils reached their maximum on the north-facing slope. The concentrations of available iron (Fe) in rhizosphere soil and available copper (Cu) in non-rhizosphere soil reached their maximum on the south-facing slope. Slope aspect significantly affected the total concentrations of potassium (K), calcium (Ca), magnesium (Mg), Cu, and Mn in rhizosphere and non-rhizosphere soils, and all of these elements reached their maximum on the northwest-facing slope. Slope aspect significantly influenced the concentrations of aboveground K, Ca, and Mg, sodium (Na), Mn, and belowground K in A. sacrorum, and the concentrations of aboveground K, Ca, Mg, and Na and belowground Mn, Na, Fe, Ca, and Mg in weed. Most elements in A. sacrorum and the weeds reached their maximum on the south-facing slope. Slope aspect significantly changed the aboveground-to-belowground concentration ratios of K, Ca, and Na in A. sacrorum and weed. Slope aspect significantly affected the storage of macro- and micronutrients in A. sacrorum and weed but not the storage in the plants of the entire plot. Slope aspect predominantly affected the storage allocation of macro- and micronutrients in A. sacrorum but not those in weed. Slope aspect is an important topographic factor that affects the macro- and micronutrients in plants and soil in micro-ecosystem environments.
Assuntos
Artemisia , Ecossistema , China , Micronutrientes , SoloRESUMO
The 9-, 17-, 30- and 37-year-old Robinia pseudoacacia plantations in the loess hilly region were investigated to study the dynamics and allocation patterns of carbon and nitrogen storage. The results showed that the ranges of carbon and nitrogen contents were 435.9-493.4 g x kg(-1) and 6.8-21.0 g x kg(-1) in the arbor layer, 396.3-459.2 g x kg(-1) and 14.2-23.5 g x kg(-1) in the herb and litter layer, and 2.7-10.7 g x kg(-1) and 0.2-0.7 g x kg(-1) in the soil layer, respectively. The branch was the major carbon and nitrogen pool in the arbor layer, accounting for 46.9%-63.3% and 39.3%-57.8%, respectively. The maximum storage values were 30.1 and 1.8 Mg x hm(-2) for carbon and nitrogen, respectively, in the 0-20 cm soil layer in the 37-year-old R. pseudoacacia plantation. The total carbon and nitrogen storage in the R. pseudoacacia plantation ecosystem increased with increasing forest age, and the maximum values were 127.9 Mg x hm(-2) and 6512.8 kg x hm(-2) for carbon and nitrogen storage, respectively, in the 37-year-old R. pseudoacacia plantation. Soil layer was the major carbon and nitrogen pool of R. pseudoacacia plantation ecosystem, accounting for 63.3%-83.3% and 80.3%-91.4%, respectively.