短花针茅(Stipa breviflora)叶片δ^(13)C对载畜率的响应

Respons of Stipa breviflora Leaf δ^(13)C to Stocking Rates

叶片δ^(13)C值、养分含量等特征体现了植物为获取最大碳收获所采取的生存适应策略,同时δ^(13)C值还可以指示植物的长期水分利用效率,了解荒漠草原短花针植物的水分及资源利用策略有助于人们掌握其生长机制,对分析短花针茅应对干扰的生态对策有重要意义。采用稳定性碳同位素技术,通过测定荒漠草原短花针茅(Stipa breviflora)叶片稳定性同位素值(δ^(13)C),结合植物叶片碳(C)、氮(N)、碳氮比(C/N)、水分含量(LWC)等生理指标,探讨不同载畜率下短花针茅叶片的适应机理。结果表明,短花针茅叶片δ^(13)C值随放牧强度的增大而显著减小(P=0.041),其中对照处理为-26.8‰,轻度放牧处理为-27.2‰,中度和重度放牧处理分别为-27.4‰和-27.5‰,表明随着放牧强度的增大,植物的水分利用效率降低。随着放牧强度的增大,短花针茅叶片N质量分数增大(P=0.003),从对照到重度放牧处理依次为2.1%、2.3%、2.5%和2.7%;C质量分数减小,但不显著(P=0.076),从对照到重度放牧处理依次为46.3%、46.1%、46.1%和45.3%;C/N显著降低(P=0.004),对照到重度放牧处理依次为26.1%、20.7%、19.6%、18.5%,表明随着放牧干扰的增强,植物积累有机物质及资源利用能力下降。相关分析发现短花针茅叶片δ^(13)C值与N质量分数呈显著负相关(r=-0.690,P<0.05),与C质量分数、C/N呈显著正相关(r=0.565,r=0.668;P<0.01);叶片δ^(13)C值可指示植物有机物质的积累和资源利用能力。

The carbon stable isotope （δ^13C） value and nutrient content in plant leaves reflect the survival and adaption strategy of plants to absorb carbon maximum optimally. The long-term water use efficiency （WUE） of plant was indicated by the δ^13C value as well. The objective of this study was to assess the effect of different stocking rates on resource utilization of Stipa breviflora. The δ^13C, carbon （C）, nitrogen （N）, C/N ratio, water content （LWC） in leaves were determined to analyze the adaption mechanism. Results showed that： the δ13C value in S. breviflora leaves reduced （P=0.041） as stocking rates increased, and they were -26.8‰, -27.2‰, -27.4‰, and -27.5‰ in control check （CK）, light grazed （LG）, moderate grazed （MG） and heavy grazed （HG）, respectively. That also meant the WUE decreased with increasing stocking rates. The N percent in S. breviflora leaves elevated as stocking rates increased, and they were 2.1%, 2.3%, 2.5% and 2.7%, respectively. While the C percent in S. breviflora leaves were not observed differences （P=0.076） and they were 46.3%, 46.1%, 46.1% and 45.3% with increasing stocking rates. The C/N ratio in S. breviflora leaves were lowered （P=0.004） as stocking rates increased, and they were 26.1%, 20.7%, 19.6% and 18.5%, respectively. That meant organic matter accumulation and resource absorption of S. breviflora declined with increasing stocking rates. The δ^13C were negatively associated with N percent （r=-0.690, P〈0.05） while positively related to C percent and C/N ratio （r=0.565, r=0.668; P〈0.01）. Leaf δ13C values could indicate the accumulation of plant organic matter and resource utilization.