Abstract Extensive livestock production is one of the activities that, without requiring habitat conversion, contributes to grassland conservation and human well-being. In Uruguay, approximately 60% of the land is covered by natural temperate grasslands, which are entirely devoted to extensive livestock production, mainly cattle and sheep. In this study we described the spatial and temporal variability of aboveground net primary productivity (ANPP), net secondary productivity (NSP) and trophic efficiency (TEf) of temperate grasslands in two geomorphological regions of Uruguay (Basaltic “Cuesta” and Eastern Hills), and explored their relationship with the mean and annual precipitation (MAP and PPT, respectively). Specifically, we asked whether Uruguayan grasslands are able to damp precipitation variability at the levels of vegetation and herbivores. Additionally, we searched for lag effects of precipitation on primary and secondary productivity. The study period included seven growing seasons, from 2005 to 2012. PPT, ANPP and NSP were calculated monthly for 32 sections (administrative units) of both regions, and aggregated at the growing season level. NSP-related data included not only livestock numbers, but also livestock births, mortality and transportation, as well as milk and wool production. ANPP showed a clear inter-regional difference, the Eastern Hills region was more productive (69,814 MJ.ha−1.y−1) than the Basaltic “Cuesta” (60,762 MJ.ha−1.y−1). NSP showed no inter-regional differences (742 vs. 754 MJ.ha−1.y−1, respectively) and TEf was higher in Basaltic “Cuesta” (0.0125) than in Eastern Hills (0.0107). As expected, ANPP was strongly determined by the amount of rainfall, both in space and time. Although we did not find a relationship between current year NSP and ANPP, secondary productivity was positively related with PPT and ANPP with a two-year lag in Basaltic “Cuesta”. Also, we found that the interannual variabilities of ANPP and NSP were, respectively, 60 and 40% lower than the variability of precipitation, but contrary to our expectation, NSP was 40% more variable than ANPP. Only 1.17% of the energy captured by grasslands in Uruguay is converted into domestic herbivore production, a value close to the average reported for other grasslands and savannas.

中文翻译：

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乌拉圭牧场不同营养级降水变异的阻尼和滞后效应

摘要 畜牧业的粗放生产是一种无需改变栖息地就有助于草原保护和人类福祉的活动。在乌拉圭，大约 60% 的土地被天然温带草原覆盖，这些草原完全用于粗放的牲畜生产，主要是牛和羊。在这项研究中，我们描述了乌拉圭两个地貌区（玄武岩“Cuesta”和东山）温带草原地上净初级生产力（ANPP）、净次级生产力（NSP）和营养效率（TEf）的时空变异性，并探讨了它们与平均和年降水量（分别为 MAP 和 PPT）的关系。具体而言，我们询问乌拉圭草原是否能够抑制植被和食草动物水平的降水变化。此外，我们还研究了降水对初级和次级生产力的滞后效应。研究期间包括7个生长季，从2005年到2012年。PPT、ANPP和NSP每月计算两个地区的32个部门（行政单位），并在生长季层面进行汇总。NSP 相关数据不仅包括牲畜数量，还包括牲畜出生、死亡率和运输，以及牛奶和羊毛产量。ANPP 显示出明显的区域间差异，东山地区的生产力（69,814 MJ.ha-1.y-1）比玄武岩“Cuesta”（60,762 MJ.ha-1.y-1）更高。NSP 没有显示区域间差异（分别为 742 和 754 MJ.ha-1.y-1），玄武岩“Cuesta”（0.0125）的 TEf 高于东山（0.0107）。正如预期的那样，ANPP 很大程度上取决于降雨量，无论是空间还是时间。虽然我们没有发现当年 NSP 和 ANPP 之间的关系，但在玄武岩“Cuesta”，二次生产力与 PPT 和 ANPP 呈正相关，滞后两年。此外，我们发现 ANPP 和 NSP 的年际变率分别比降水变率低 60% 和 40%，但与我们的预期相反，NSP 的变率比 ANPP 大 40%。乌拉圭草原捕获的能量中只有 1.17% 转化为国内食草动物生产，接近其他草原和稀树草原报道的平均值。我们发现 ANPP 和 NSP 的年际变率分别比降水变率低 60% 和 40%，但与我们的预期相反，NSP 的变率比 ANPP 大 40%。乌拉圭草原捕获的能量中只有 1.17% 转化为国内食草动物生产，接近其他草原和稀树草原报道的平均值。我们发现 ANPP 和 NSP 的年际变率分别比降水变率低 60% 和 40%，但与我们的预期相反，NSP 的变率比 ANPP 大 40%。乌拉圭草原捕获的能量中只有 1.17% 转化为国内食草动物生产，接近其他草原和稀树草原报道的平均值。