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以黄土高原典型小流域(羊圈沟小流域)内刺槐人工林为对象,通过测定叶片尺度水碳交换过程及主要影响因素,探究了叶片尺度水碳交换随坡向和林龄的变化,并分析了叶片养分变化对水碳交换过程的潜在影响。结果表明:(1)11年生与27年生刺槐处于不同的生长阶段,前者水碳交换的强度高于后者。(2)半阳坡中光合固碳、水分利用效率及CO_2供应能力强的刺槐所占比例高于阳坡,说明半阳坡更适合刺槐生长。(3)叶片N、K含量在样方间的变化趋势为:半阳坡>阳坡,27年生>11年生,说明半阳坡刺槐的生长状况好于阳坡,高林龄刺槐的生长状况好于低林龄刺槐。同时,各样方间K含量具有显著差异,说明K对坡向及林龄的变化较为敏感。因此,与阳坡相比,该区域未来人工刺槐林建设应优先选择水热条件更为适宜的半阳坡,且在富含有效钾的土壤中进行植被恢复是提高植物水分利用效率的潜在途径,该研究结果对于未来干旱半干旱区退耕还林方案的改进及已有人工林的管理具有借鉴意义。
Based on the Robinia pseudoacacia plantation in a typical small watershed of the Loess Plateau (Yangcungou watershed), carbon exchange process and its main influencing factors in leaf-scale water were studied. The potential impact of leaf nutrient changes on water-carbon exchange was analyzed. The results showed that: (1) 11-year-old and 27-year-old Robinia pseudoacacia were in different stages of growth. The former had higher water-carbon exchange intensity than the latter. (2) The proportion of Robinia pseudoacacia in the semi-sunny slope with photosynthetic carbon fixation, water use efficiency and CO 2 supply ability is higher than that in the sunny slope, indicating that the semi-sunny slope is more suitable for the growth of the locust. (3) The change trend of N and K content in leaves was in the order of semi-sunny slope> sunny slope and 27-year-old> 11-year-old, which indicated that the growth of Robinia pseudoacacia on the semi-sunny slope was better than that on the sunny slope, Robinia pseudoacacia in low forest age. At the same time, the content of K was significantly different among different samples, indicating that K was more sensitive to changes of aspect and age. Therefore, compared with the sunny slope, the artificial Robinia pseudoacacia forest in the future should give priority to the semi-sunny slope with more suitable hydrothermal conditions, and the restoration of vegetation in the soil rich in available K is the potential way to improve the water use efficiency The results of this study are of reference for the improvement of the program of returning the grain plots to forestry in the future arid and semi-arid areas and the management of existing plantations.