ABSTRACT
To explore changes in soil aggregate stability along an elevation gradient, and its regulating factors, soil samples were taken from the 0-10 cm surface layer at 3 different elevations on Taibai Mountain. We measured and analyzed the distribution of soil aggregates, physical and chemical properties, microbial biomass, and extracellular enzymes. The results showed that: â the soil aggregates from the 3 elevations had mean weight diameters (MWD) of 2.17 mm, 1.83 mm, and 1.82 mm (increasing elevation), and geometric mean diameters (GMD) of 1.66 mm, 1.39 mm, and 1.32 mm, respectively. â¡ The change in soil aggregate stability along an elevation gradient was regulated by extracellular enzymes in the soil, in particular, the LAP in soil meso-aggregate and the BG in soil micro-aggregate. ⢠Microorganisms can alleviate the N limitation at high elevations by adjusting the relative production of extracellular enzymes and altering nutrient utilization efficiency, which also changes soil aggregate stability along an elevation gradient. The results of this study have important scientific significance for soil quality evaluation and ecological environment protection in Taibai Mountain.
Subject(s)
Altitude , Soil , Biomass , NutrientsABSTRACT
Based on a 9-year field experiment, soil samples under straw mulching (SM), plastic film mulching (FM) and no mulching (CK) were incubated at 15, 25 and 35 â for 60 d to investigate the responses of soil respiration to warming and its temperature sensitivity. The results showed that during the whole incubation period, soil respiration rate exhibited a unimodal distribution, while the cumulative soil respiration increased with an "S" curve. The cumulative soil respiration during the first 30 d accounted for about 75%-85% of total during the whole incubation period. The cumulative SM increased by 19.4% compared with CK, whereas no difference was detected between CK and FM. At 25 â and 35 â, the mean soil respiration rate increased by 17.0% and 36.8%, and the cumulative CO2 release of soil respiration increased by 13.1% and 33.6%, respectively, compared with 15 â. No interaction was detected between mulching method and temperature. 97.7%-99.9% of variation in soil respiration could be explained by temperature change, with soil respiration being positively correlated with organic carbon and total nitrogen content. Compared with no mulching and plastic film mulching, straw mulching could significantly promote soil respiration by increasing the input of organic matter in the soil, but reduced the temperature sensitivity of soil respiration. Straw mulching rather than plastic film mulching would be more efficient at reducing CO2 emission in the Loess Plateau dryland farming area under the context of global warming.
Subject(s)
Soil , Zea mays , Agriculture , China , Temperature , Triticum , WaterABSTRACT
To objectively evaluate and compare the stability and sustainability of different planting patterns of typical watersheds in Loess Plateau of China after the Grain for Green Project, this paper used the emergy analysis method to quantify the emergy inputs and outputs of three watersheds with different planting patterns, i.e., both grains and fruit trees (Gaoxigou watershed), mainly grains (Wuliwan watershed) and mainly fruit trees (Miaozuigou watershed). In addition, an emergy analysis system was established to evaluate the suitability of the three patterns from the perspectives of natural resources pressure as well as social and economic development levels. More than 75% of the total emergy inputs of all the three watersheds were purchased, and nonrenewable emergy inputs had a much larger contribution than renewable emergy inputs, indicating the characteristic of low emergy self-sufficient ratio and considerable high environmental loading ratio. The pattern of planting grains had high emergy inputs but low emergy outputs, while the patterns of planting fruit trees and planting both had high emergy inputs and outputs. The energy densities of all three patterns reached two times of the average of agricultural systems in China. Especially, the net emergy of planting grains pattern was the lowest while that of planting both grains and fruit trees was the highest. The environmental sustainability index (ESI) of planting grains pattern was less than 1 and both emergy and ESI were much lower than national averages. The ESI of planting both grains and fruit trees pattern was the highest. In summary, comparison of the three patterns showed that planting both grains and fruit trees had better sustainability and high stability and the emergy production efficiency was high. Thus, it was suggested to change the agricultural development from watershed based units to multi-industry integrated mode.
