荒漠草原不同雨量带土壤-植物-微生物C、N、P及其化学计量特征

降水作为关键性驱动因子深刻影响着荒漠草原生态系统养分循环过程。采用生态化学计量学方法,调查了荒漠草原不同雨量带土壤-植物-微生物C、N、P及其生态化学计量特征对降水格局的适应性规律。研究区不同雨量带土壤C、N、P随降水梯度的递减亦呈现递减趋势。平均土壤C∶N∶P比例为28.9∶2.7∶1,主要受到P元素控制。不同雨量带平均土壤MBC∶MBN∶MBP比例为108.6∶5.6∶1,表现出明显的C富集现象。不同雨量带平均植物C∶N∶P比例为117.4∶6.7∶1,表现为明显的C、N缺乏或P富集。降水为主的气候原因造成了研究区环境中P含量相对较高,并直接反映在了植物化学计量特征上。研究区土壤C和N之间具有极显著的正相关关系(P0.01),相关系数高达0.98。植物N和P之间具有显著的正相关关系(P0.05),相关系数为0.90。土壤N与植物C、P分别呈显著正相关和显著负相关(P0.05),相关系数分别为0.84和-0.82。降水在塑造荒漠草原生态格局以及驱动生态系统养分循环过程中发挥了关键性作用。

Soil-plant-microbial C, N, P and their stoichiometric characteristics in different rainfall zones of desert steppe

As a critical driving factor of ecosystem, precipitation plays a key role in shaping ecological landscape pattern in desert steppe. However, the response and adaptation mechanism of ecosystem nutrient cycle on precipitation remain unclear due to the complexity of spatio-temporal precipitation variation. In this study, soil-plant-|microbial C, N, P and their stoichiometric characteristics in different rainfall zones in the Darhan Muminggan Joint Banner were analyzed to investigate the nutrient utilization strategy of desert ecosystem driven by precipitation. The results show that, the mean TOC, TN, and TP contents of soil in different rainfall zones are 13.39 g/kg, 1.27 g/kg, and 0.46 g/kg, respectively. The mean soil C:N:P ratio is 28.9:2.7:1 in the study area, which is mainly controlled by P. The soil C, N and P contents in different rainfall zones in the study area shows a decreasing trend with the decrease of precipitation gradient. The C:N, C:P, and N:P ratios also indicate a decreasing trend with the decrease of precipitation gradient, which mainly reflects the difference of organic matter accumulation and mineralization ability in different rainfall zones. The mean microbial biomass C, N, and P contents in different rainfall zones are 0.37 g/kg, 0.022 g/kg, and 0.0039 g/kg, respectively. The mean C:N:P ratio of soil microbial biomass is 108.6:5.6:1 in different rainfall zones, which shows a C enrichment. The soil microbial biomass N:P ratio declines with the decreasing of precipitation. The mean C, N, and P contents of plants in different rainfall zones are 39.15%, 2.24%, and 0.33%, respectively. The mean plant C:N:P ratio is 117.4:6.7:1, which presents a limitation of C and N or a enrichment of P. The climatic reasons caused a relatively high P content in the environment of the study area. The P content of plants increases gradually with the decrease of precipitation. The plant C:N, C:P and C:N:P ratios in different rainfall zones show a decreasing trend with the decrease of precipitation. The N:P ratio of plants is more narrower than C:N and C:P ratios. The C:N and C:P ratios of Stipa breviflora are apparently higher than those of Stipa krylovii, which exists in the enclosed area. Under the same hydrothermal and nutrient conditions, Stipa breviflora shows a higher nutrient use efficiency (CUE), and therefore, is more suitable to survive in the harsh desertification environment. Compared with microorganism, the C:N, C:P and C:N:P ratios of plants are more narrower, and thus are more suitable as predictors of nutrient limitation. A significantly positive correlation at P < 0.01 is found between C and N contents in soil, which has a correlation coefficient of 0.98. The plant N and P show a significantly positive correlation (P < 0.05) with their correlation coefficient of 0.90. Among soil, plant, and microbial biomass in the study area, soil N has a significantly positive correlation (P < 0.05) and a significantly negative correlation (P < 0.05) with plant C (correlation coefficient 0.84) and P (correlation coefficient -0.82), respectively. The rest do not reach the significant level.