Grazing Intensity Controls the Seasonal Utilization of Functionally Diverse Patches by Mediating Herbivore Selectivity

IF 2.4 3区 环境科学与生态学 Q2 ECOLOGY
Nicolas Caram , Felipe Casalás , Pablo Soca , Marcelo O. Wallau , Lynn E. Sollenberger , Mónica Cadenazzi , Pablo Boggiano
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引用次数: 0

Abstract

Understanding the mechanistic link between plant functional traits and foraging patterns across seasons and grazing intensities is crucial for implementing sustainable grazing systems and predicting ecological successions. We assessed the interaction effects of grazing intensity, season, and leaf functional traits on herbivore grazing patterns in a native grassland composed of functionally diverse patches in four 10–14 ha paddocks managed under lenient or moderate grazing intensities. Seasonal botanical composition was estimated in permanent 20 × 20 cm patches. Defoliation events of species in patches were recorded every 7–10 d, four times during summer-autumn, and five times during winter and spring. Leaf dry matter content, specific area, tensile strength, and width of dominant grass species were measured seasonally, and species were allocated to functional groups. The proportion of total defoliation events occurring in each functional group and their selectivity index were estimated for each period and season. We tested the relationship between trait community weighted mean in the pasture and that grazed by cattle for each quadrant and period within seasons. Cows focused grazing on resource-acquisitive strategy species with wider and more tender leaves during summer-autumn under both grazing intensities. As herbage mass and accumulation decreased during winter, cows shifted their foraging strategy toward shorter patches and previously rejected, tougher-thinner leaves and resource-conservative strategy species stockpiled from summer-autumn, not overgrazing the resource-acquisitive species. However, this general pattern was modulated by grazing intensity; cows grazed taller patches and more tender and wider-leaved species under lenient than moderate grazing intensity. Thus, the spatiotemporal heterogeneity of desired and rejected stockpiled patches of different functional groups was managed by integrating seasonality, grazing intensity, and leaf functional traits. Therefore, the general principle of foraging selectivity toward desired species can be altered by management practices and inherent species attributes, maintaining communities of species of different ecosystem functions in equilibrium.

放牧强度通过调节食草动物的选择性来控制对功能多样化斑块的季节性利用
了解不同季节和不同放牧强度下植物功能特征与觅食模式之间的机理联系对于实施可持续放牧系统和预测生态演替至关重要。我们评估了放牧强度、季节和叶片功能特性对食草动物放牧模式的交互影响,这片原生草地由功能多样的斑块组成,分布在四个 10-14 公顷的围场中,放牧强度为宽松或适度。在 20 × 20 厘米的永久性斑块中估测了季节性植物组成。每隔 7-10 天记录一次斑块中物种的落叶情况,夏秋季记录四次,冬春季记录五次。按季节测量主要草种的叶片干物质含量、比面积、抗张强度和宽度,并将草种归入功能组。我们估算了每个时期和季节发生在每个功能群落中的总落叶事件比例及其选择性指数。我们测试了牧场中性状群落加权平均值与牛在季节内每个象限和每个时期所吃牧草的性状群落加权平均值之间的关系。在两种放牧强度下,奶牛在夏秋两季都集中放牧叶片较宽、较嫩的资源获取策略物种。随着冬季草料质量和累积量的减少,奶牛的觅食策略转向了较短的草块和之前被拒绝的、叶片较硬较薄的物种,以及夏秋季节储备的资源保护策略物种,而不是过度放牧资源获取型物种。然而,这种一般模式会受到放牧强度的影响;与中等放牧强度相比,奶牛在宽松的放牧强度下会放牧更高的斑块以及更嫩、叶片更宽的物种。因此,通过综合季节性、放牧强度和叶片功能特性,可以管理不同功能组的所需和所弃堆积斑块的时空异质性。因此,对所需物种觅食选择性的一般原则可以通过管理措施和固有物种属性来改变,从而维持不同生态系统功能物种群落的平衡。
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来源期刊
Rangeland Ecology & Management
Rangeland Ecology & Management 农林科学-环境科学
CiteScore
4.60
自引率
13.00%
发文量
87
审稿时长
12-24 weeks
期刊介绍: Rangeland Ecology & Management publishes all topics-including ecology, management, socioeconomic and policy-pertaining to global rangelands. The journal''s mission is to inform academics, ecosystem managers and policy makers of science-based information to promote sound rangeland stewardship. Author submissions are published in five manuscript categories: original research papers, high-profile forum topics, concept syntheses, as well as research and technical notes. Rangelands represent approximately 50% of the Earth''s land area and provision multiple ecosystem services for large human populations. This expansive and diverse land area functions as coupled human-ecological systems. Knowledge of both social and biophysical system components and their interactions represent the foundation for informed rangeland stewardship. Rangeland Ecology & Management uniquely integrates information from multiple system components to address current and pending challenges confronting global rangelands.
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