不同林龄植被培肥改良土壤效益研究

在黄土丘陵沟壑区森林植被能够明显改善生态环境 ,防止土地退化 ,提高土壤中有机质、速效氮和速效钾的含量 ,降低土壤pH和容重 ;快速显著地增加土体中 >0 .2 5mm水稳性团聚体和 >5 0 μm微团粒的数量 ,使土壤结构改善 ,协调供应养分和水分的能力提高 ;能促进黏粒形成 ,坚实度增加 ,土壤的抗蚀性和抗冲性提高 ,有效地减少水土流失。植被对土壤的培肥改良是一种正向持续反馈机制 ,时间越长 ,效益越显著

Effects of nitrogen fertilization on soil respiration in temperate grassland in Inner Mongolia, China

Nitrogen addition to soil can play a vital role in influencing the losses of soil carbon by respiration in N-deficient terrestrial ecosystems. The aim of this study was to clarify the effects of different levels of nitrogen fertilization (HN, 200 kg N ha(-1) year(-1); MN, 100 kg N ha(-1) year(-1); LN, 50 kg N ha(-1) year(-1)) on soil respiration compared with non-fertilization (CK, 0 kg N ha(-1) year(-1)), from July 2007 to September 2008, in temperate grassland in Inner Mongolia, China. Results showed that N fertilization did not change the seasonal patterns of soil respiration, which were mainly controlled by soil heat-water conditions. However, N fertilization could change the relationships between soil respiration and soil temperature, and water regimes. Soil respiration dependence on soil moisture was increased by N fertilization, and the soil temperature sensitivity was similar in the treatments of HN, LN, and CK treatments (Q (10) varied within 1.70-1.74) but was slightly reduced in MN treatment (Q (10) = 1.63). N fertilization increased soil CO2 emission in the order MN > HN > LN compared with the CK treatment. The positive effects reached a significant level for HN and MN (P < 0.05) and reached a marginally significant level for LN (P = 0.059 < 0.1) based on the cumulative soil respiration during the 2007 growing season after fertilization (July-September 2007). Furthermore, the differences between the three fertilization treatments and CK reached the very significant level of 0.01 on the basis of the data during the first entire year after fertilization (July 2007-June 2008). The annual total soil respiration was 53, 57, and 24% higher than in the CK plots (465 g m(-2) year(-1)). However, the positive effects did not reach the significant level for any treatment in the 2008 growing season after the second year fertilization (July-September 2008, P > 0.05). The pairwise differences between the three N-level treatments were not significant in either year (P > 0.05).