| In order to study the effect of site condition on soil, litter and plant leaf stoichiometryand their relationship, soil, litter and leaf samples were collected from different positions inforest zone, forest-grassed zone and grass zone on the Loess Plateau. The results showed that:(1)In forest zone, soil organic carbon (OC), total nitrogen (TN) and total phosphorus (TP)showed that Shady lower slope> Sunny lower slope> Shady middle slope> Sunny middleslope> Hill top, moreover, OC and TN were more sensitive than TP, while total potassium(TK) was relatively stable. Soil C:N and P:K changed little, being11.62and0.03, respectively,while other nutrient stoichiometry ratios were consistent with soil total nutrients contents. C:P,C:K, N:P and N:K were25.05,0.91,2.13and0.08, respectively. Litter total nutrients contentschanged with the site condition slightly, representing the different rules. The biggest litter C:N,C:P and N:P were obtained in Hill top, significantly bigger than other treatments. However,litter C:K, N:K and P:K were bigger in Hill top and Shady middle slope. The average litterC:N、C:P、C:K、N:P、N:K and P:K were38.39,272.55,116.78,6.81,3.08and0.45,respectively.Artemisia gmelinii, Syzygium aromaticum and Rosa Xanthina leaves totalnutrients contents and various stoichiometry ratios changed complicatedly. Artemisia gmeliniileaf contained more nutrients, while Rosa Xanthina leaves contained less. However, thestoichiometry ratios were reversed exactly, this showed that the Rosa Xanthina leaves had thebetter nutrient use efficiency. The leaves C:N、C:P、C:K、N:P、N:K and P:K were23.60,277.78,27.84,10.72,1.20and0.12, respectively. There was lacking of nitrogen in studyarea.(2)In forest-grass zone, soil OC, TN and TP contents was relatively slow, and there wasno obvious difference in different site conditions, while TK was highest in Sunny middleslope. Soil average C:N、C:P、C:K、N:P、N:K and P:K were9.79,8.26,0.25,0.87,0.03and0.03, respectively. Similarly, litter nutrients contents were low and showed different changerules with site conditions. OC, TN and TP were higher in shady slope than sunny slope,especially for OC and TN. While the biggest TK was observed in Sunny lower slope. Theaverage litter C:N、C:P、C:K、N:P、N:K and P:K were54.01,132.55,67.50,2.77,1.28and0.54, respectively.Artemisia gmelinii, Artemisia giraldii and Lespedezadavurica (Laxm.) Schindl. leaves total nutrients contents and various stoichiometry ratios changedcomplicatedly. Artemisia gmelinii and Artemisia giraldii leaves nutrients contents werehomogeneous and changed consistently. Artemisia gmelini and Artemisia giraldii also had thebetter nutrient use efficiency than Lespedezadavurica (Laxm.) Schindl.. The leaves C:N、C:P、C:K、N:P、N:K and P:K were26.55,226.94,31.83,8.72,1.33and0.18, respectively.(3)In grass zone, soil OC, TN and TK represented higher in Sunny middle slope, Hill topand Shady lower slope, lower in Sunny lower slope and Shady middle slope. While TP changelittle in different site conditions. Soil nutrient stoichiometry ratios showed little change, beinglower than the national average. Nutrient ratios were more stable than total nutrients. Soilaverage C:N、C:P、C:K、N:P、N:K and P:K were9.69,8.09,0.25,0.84,0.03and0.03.LitterOC was stable, while TN was higher in shady slope than sunny slope, and lower slope and hilltop than middle slope. TP was reverse with TN, representing sunny slope> hill top> shadyslope, middle slope> lower slope. Similarly, TK manifested middle slope> lower slope.Litter nutrient stoichiometry ratios showed different changes with site conditions, and TP wasdominant element to regulate the ratios. The average litter C:N、C:P、C:K、N:P、N:K and P:Kwere41.62,160.47,94.56,4.10,2.32and0.62, respectively.Artemisia gmelini and Artemisiagiraldii showed homogeneous change, representing sunny slope higher than shady slope.These two plants had the better carbon, phosphorus and potassium storage abilities, whileLespedezadavurica (Laxm.) Schindl. accumulated nitrogen more strongly. Leaves nutrientstoichiometry changed differently with the site conditions. The leaves C:N、C:P、C:K、N:P、N:K and P:K were18.35,154.73,27.56,9.28,1.82and0.19, respectively. There was lackingof nitrogen in study area. Artemisia gmelinii and Artemisia giraldii had the better nitrogen useefficiency while Lespedezadavurica (Laxm.) Schindl. had the better phosphorus andpotassium use efficiency.(4)Soil nutrient stoichiometry ratios in forest zone were significantly higher which inforest-grass zone and grass zone, whereas, there was no significant different between the lattertwo zones. Litter and Artemisia gmelinii leaf nutrient stoichiometry ratios changedcomplicatedly in different vegetation zones, without consistent law. Litter C:N wassignificantly positive related with Artemisia gmelinii leaf C:N, similarly with P:K. Soilstoichiometry ratios was unrelated with litter and Artemisia gmelinii leaf stoichiometry ratios. |
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