Exclosure cages are often used for estimating biomass accumulation on continuously stocked pastures in grazing experiments. The microclimate inside the cages may affect the estimates of biomass accumulation, but this has not been previously identified or quantified. We evaluated how the exclusion from grazing for 21 days in Mulato II brachiariagrass (Brachiaria brizantha × Brachiaria decumbens × Brachiaria ruziziensis) pastures affected canopy air temperature (T) and relative humidity (RH) and how this related to biomass accumulation. We also evaluated the effect of the exclosure cage on wind speed (WS) and incoming solar radiation (SR), and how these impacted evapotranspiration (ET) and estimates of biomass accumulation on grazed canopies maintained at 20- and 30-cm height under continuous stocking. Regardless of canopy height, changes in canopy structure during the exclusion period up to 21 days did not affect T and RH (averages of 24.3 °C and 88.7%, respectively), indicating that the air circulation was not affected by the exclusion. The cage structure reduced SR by 5%, although there were times during clear days when SR was slightly greater inside the cage than outside. The cage also reduced WS by 4.4%. Smaller SR and WS resulted in less ET inside the cages than outside, although with close values (2.9 vs. 3.0 mm day⁻¹; P = 0.0494). The biomass accumulation rate was greater inside than outside the cages for both canopy heights. This overestimation would be 5.8 and 9.7% greater if the structure of the cage did not reduce the SR, WS, and ET.

在放牧实验中，封闭笼通常用于估计连续放养牧场上的生物量积累。笼子内的小气候可能会影响对生物量积累的估计，但这以前没有被确定或量化。我们评估了在 Mulato II brachiariagrass ( Brachiaria brizantha  ×  Brachiaria decumbens  ×  Brachiaria ruziziensis) 中如何排除放牧 21 天) 牧场影响冠层空气温度 (T) 和相对湿度 (RH) 以及这与生物量积累的关系。我们还评估了封闭笼对风速 (WS) 和入射太阳辐射 (SR) 的影响，以及这些影响如何影响蒸散量 (ET) 以及在连续条件下保持在 20 和 30 厘米高度的放牧树冠上的生物量积累估计袜。无论冠层高度如何，在长达 21 天的排除期内冠层结构的变化不影响 T 和 RH（平均值分别为 24.3°C 和 88.7%），表明空气循环不受排除的影响。笼子结构将 SR 降低了 5%，尽管有时在晴朗的日子里，笼子内部的 SR 略大于外部。笼子还将 WS 降低了 4.4%。^-1 ; P  = 0.0494）。两种冠层高度的生物量积累率在网箱内均大于网箱外。如果笼子的结构没有降低 SR、WS 和 ET，那么这个高估会高出 5.8% 和 9.7%。