无芒隐子草(Cleistogenes songorica)叶片生态解剖及氮磷化学计量特征对载畜率的响应

Responses of Cleistogenes songorica Blade Ecological Anatomy and N/P Stoichiometry to Stocking Rates

摘要: 无芒隐子草为多年生强旱生密丛禾草，是荒漠草原的建群种和优势种，不仅适口性好，而且具有抗热、抗旱、耐寒和耐践踏等特性，对荒漠草原生态系统的恢复和保育具有重要作用。该文以内蒙古荒漠草原无芒隐子草为研究对象，分析了不同载畜率(不放牧、轻度放牧、中度放牧、重度放牧)对无芒隐子草叶片解剖结构和N、P化学计量特征的影响，以探究无芒隐子草叶片上述性状对环境改变的响应与适应对策。结果表明：不同载畜率水平下，无芒隐子草叶片解剖结构除了上、下表皮细胞厚度之外，其余的指标均产生了显著变化(P < 0.05)，但随着载畜率的增加没有明显的一致性变化规律。所有的放牧处理均显著增加了无芒隐子草叶片中的全N含量(P < 0.05)。轻度和中度放牧没有显著影响叶片全P含量，而重度放牧显著降低了叶片的全P含量(P < 0.05)。任何放牧处理对叶片N:P比均没有显著影响。在CK条件下，无芒隐子草叶片的全N含量与上表皮细胞面积之间存在显著的负相关(P < 0.05)。在MG条件下，全P含量与上表皮细胞面积之间存在显著的正相关(P < 0.05)，同时与主脉厚度之间存在着极显著负相关(P < 0.01)。因此，在不同载畜率下，无芒隐子草叶片解剖结构及N、P化学计量学特征的变化和二者之间的关系均存在一定的差别。

Abstract: Cleistogenes songorica, a perennial herb, is the constructive and dominant species of desert steppe in northern China. With excellent palatability as well as heat/drought/cold tolerance and trampling resistance, this species has significant effects on the restoration and conservation of desert steppe. In order to understand the response and adaption strategy of Cleistogenes songorica to grazing, we carried out field experiment to examine the influence of different stocking rates on its blade anatomy structure and N/P stoichiometry. Leaf samples of Cleistogenes songorica (3rd totally matured and sun-sloped disease-free blade from the top) were collected from a controlled-experimental platform with four stocking densities, which has been lasting for nine years on the desert steppe of Inner Mongolia. Using paraffin method, upper epidermal cuticle thickness, lower epidermis thickness, upper epidermal cell thickness, lower epidermis cell thickness, upper epidermal cell area, lower epidermis cell area, main vein thickness, leaf thickness, measured using high-power microscope. Total N and P contents were measured by Semi-micro kjeldahl determination and the H2SO4-HClO4 fusion method, respectively. All leaf anatomic characters of Cleistogenes songorica, except for upper and lower epidermal cell thickness, showed significant variation among different grazing rates (P < 0.05). However, there was no consistent pattern for the changes of these anatomic characters with the increase of stocking rates. Leaf N and P contents showed limited changes under LG and MG levels. Grazing significantly increased leaf N contents (P < 0.05), with the highest value in HG. Total P contents in HG were significantly lower than the 3 others (P < 0.05). Leaf N:P was highest in HG and lowest in MG. In the control plots, leaf N contents were negatively correlated with upper epidermal cell area (P < 0.05). In the MG plots, total P contents were positively correlated with upper epidermal cell area (P < 0.05) and negatively correlated with main vein thickness (P < 0.05).