The introduction of domestic ungulates has altered the natural grazing regime, promoting the invasion of exotic woody plants being seasonality or stoking season one of the key factors regulating the grazing regime. The Pampean Mountain grasslands of Central Argentina have been intensively transformed by the presence of feral horse populations that have increased the last 40 years, coinciding with an increased abundance of Pinus halepensis dispersed from cultivated stands. In this study, we evaluated the effect of the seasonal variation in perennial grasses defoliation (no defoliation; continuous defoliation; defoliation during autumn-winter and defoliation during spring-summer) on the establishment of P. halepensis seedlings and the response of the dominant perennial grasses (Nasella tenuis and Piptochaetium lejopodum) to defoliation in areas with different grazing histories, following a split-plot design. The establishment of P. halepensis was highest in the grazed areas and in treatments where the defoliation of the perennial grasses was practiced throughout the year or during autumn-winter. Perennial grasses respond differently to defoliation according to the grazing history. In the grazed areas, defoliation negatively affected the perennial grasses during all the study period, showing the scarce resilience after grazing while in ungrazed areas, the perennial grasses were little affected by the seasonality of defoliation. Both, above- and belowground competition affected the establishment of P. halepensis, according to defoliation treatment and grazing history. The information obtained allows the elaboration of management recommendations to avoid the propagation of P. halepensis; therefore, the seasonal management of the grazing is a recommended practice toprevent or reduce the intensity of feral horse grazing during the autumn and winter months.

引入有蹄类动物已经改变了自然放牧制度，促进了外来木本植物的入侵是季节性或行季节，这是调节放牧制度的关键因素之一。阿根廷中部的Pampean山草原进行了深入的野生马种群的存在已经增加了近40年，具有丰富的增加相吻合转化地中海松从看台上种植分散。在这项研究中，我们评估了多年生禾草落叶的季节性变化（无落叶；连续落叶；秋冬期间的落叶和春夏期间的落叶）对P. halepensis幼苗的建立和优势多年生植物的响应的影响。草（按照分块设计，在有不同放牧历史的地区将Nasella tenuis和Piptochaetium lejopodum剥离。的建立P. halepensis是最高的放牧区，在其中多年生牧草的落叶在全年或在秋冬季实行的治疗方法。根据放牧历史，多年生禾草对落叶的反应不同。在放牧地区，落叶在整个研究期间均对多年生禾草产生负面影响，显示放牧后稀疏的复原力，而在未草皮地区，多年生禾草不受落叶季节的影响。地上竞争和地下竞争都影响了哈利木对虾的建立，根据脱叶处理和放牧史。获得的信息使管理建议的拟订可以避免哈尔滨假单胞菌的传播; 因此，建议在夏季和冬季进行季节性管理，以防止或减少野马放牧的强度。