Large regional-scale variation in C3/C4 distribution pattern of Inner Mongolia steppe is revealed by grazer wool carbon isotope composition
Large regional-scale variation in C3/C4 distribution pattern of Inner Mongolia steppe is revealed by grazer wool carbon isotope composition
复制标题
放牧毛碳同位素组成揭示内蒙古草原C3/C4分布格局的大区域变化
DOI：
10.5194/bg-6-795-2009
复制
发表时间：
2009-01-01
期刊：
影响因子：
4.9
通讯作者：
Schnyder, H.
中科院分区：
文献类型：
--
作者：
Auerswald, K.;Wittmer, M. H. O. M.;Schnyder, H.
通过对内蒙古中国草原植被和绵羊羊毛碳同位素数据的地统计分析，探讨了内蒙古草原C3/C4分布的空间分异规律。在0.2万km2的面积内，采集了群落现存量(n=118)和绵羊毛(n=146)。采集了连续十年(1998-2007年)的样本。群落生物量样本代表了约1000平方米(“群落尺度”)的垂直植被的碳同位素组成，而羊毛的时空尺度反映了牧群在一年内(约5-10平方公里，“农场尺度”)放牧的整个地区的碳同位素组成。羊毛和植被的成对采样显示，相对于植被，羊毛中的13C富集量为2.7±0.7‰(95%可信区间)，但这一变化与环境参数或放牧率没有明显的关系。C3和C4植被(分别为13Δ3和13Δ4)的13C判别混合模型估算了C4植物在地上生物量中的比例(Pc4，%)，考虑了大气CO2中13C的变化对样品同位素组成的影响，以及海拔和干旱对13Δ3的影响。PC4平均为19%，但差异很大：在群落尺度上是全尺度的(0%~100%)，在农场尺度上是0%~85%。农田尺度上PC4的变化在约250公里范围内表现出明显的区域格局。重要的是，PC4明显高于最热月份的22°C等温线，该等温线是从年度高分辨率地图获得的，并在不同的采样年份中平均。这与C3和C4植物的量子产量或光能利用效率的C3/C4交叉温度的预测是一致的。尽管如此，温度梯度只占农场范围内PC4变化的10%，这表明在这个范围内，额外的因素控制着PC4。
This work explored the spatial variation of C3/C4 distribution in the Inner Mongolia, P. R. China, steppe by geostatistical analysis of carbon isotope data of vegetation and sheep wool. Standing community biomass (n=118) and sheep wool (n=146) were sampled in a ~0.2 Mio km2area. Samples from ten consecutive years (1998–2007) were obtained. Community biomass samples represented the carbon isotopic composition of standing vegetation on about 1000 m2("community-scale"), whereas the spatio-temporal scale of wool reflected the isotope composition of the entire area grazed by the herd during a 1-yr period (~5–10 km2, "farm-scale"). Pair wise sampling of wool and vegetation revealed a13C-enrichment of 2.7±0.7‰ (95% confidence interval) in wool relative to vegetation, but this shift exhibited no apparent relationships with environmental parameters or stocking rate. The proportion of C4 plants in above-ground biomass (PC4, %) was estimated with a two-member mixing model of13C discrimination by C3 and C4 vegetation (13Δ3and13Δ4, respectively), in accounting for the effects of changing13C in atmospheric CO2on sample isotope composition, and of altitude and aridity on13Δ3. PC4averaged 19%, but the variation was enormous: full-scale (0% to 100%) at community-scale, and 0% to 85% at farm-scale. The farm-scale variation of PC4exhibited a clear regional pattern over a range of ~250 km. Importantly PC4was significantly higher above the 22°C isotherm of the warmest month, which was obtained from annual high-resolution maps and averaged over the different sampling years. This is consistent with predictions from C3/C4 crossover temperature of quantum yield or light use efficiency in C3 and C4 plants. Still, temperature gradients accounted for only 10% of the farm-scale variation of PC4, indicating that additional factors control PC4on this scale.