RIEPT Trials - Ecosystems T: Isothennic savannas

In 1978, CIAT's Tropical Pastures Program, with the cooperation of national research institutions active in pastures research, took the initiative of forming the RIEPT (Red Internacional de Evaluación de Pastos Tropicales - i.e . lnternational Tropical Pastures Evaluation Network). Its central objectives were defined as, To contribute to the search for new pasture germplasm for the different production ecosystems prevalent in the poor, acid soils of the vast agricultural frontiers of the continent; Developing extrapolations based on knowledge of the range of ecosystems and subecosystems to which germplasm can adapt; Developing and promoting scientific capabilities within the network in order to achieve efficiency in the experimentation process, which, in a dynamic and sequential manner, will incorporate promising germplasm in pastures and put these in appropriate production systems.(Toledo, 1982) To fulfill these objectives, RIEPT was relied on Regional Trials A (RTAs) representing major ecosystems (well-drained isohyperthennic and isothennic savannas; poorly drained savannas; and rainy and semievergreen seasonal tropical forests), and carried out Regional Trials B (RTBs) at sites representative of the subecosystems found within these five major ecosystems. In the RTAs, an evaluation of the adaptation potential of germplasm under the conditions of a major ecosystem was first made, that is, the potential survival of the germplasm is assessed. The materials that survive and also show a high degree of productivity were exposed to subecosystem conditions in the RTBs, where evaluations were conducted under cutting to measure seasonal productivity (that is, under maximum and minimum rainfall), and so obtain a measurement that integrates adaptability and productivity potential. Until this stage, evaluations were made monoculture, in small plots, with the only purpose of selecting germplasm adapted to the natural conditions (soil, climate, biotic pressures) of different ecosystems. By using uniform evaluation methodologies, it was possible to make multilocational analyses that could extrapolate from known adaptation ranges of the selected germplasm. However, that agronomic experimentation (RTAs and RTBs) was not in any way sufficient to comply with the final objective of incorporating new germplasm options in pastures for animal production systems at the continent's agricultural frontiers. RIEPT therefore proposed to carry out regional trials under grazing in two phases. In the first, known as Regional Trials C (RTCs), the idea was to incorporate new germplasm in pastures to study its potential compatibility under grazing in small plots in terms of productivity (dry-matter yields and carrying capacity) and persistence (dynamics of botanical composition, changes in plant architecture, and seed reserves) under different grazing management systems. In the second phase, Regional Trials D (RTDs), the best pastures in terms of productivity, persistence, and ease of management were compared with the best pastures under traditional use. In these trials, pasture productivity as animal products (beef, milk, and calves) within the context of the predominant production system in each region were measured. This dataset provides RIEPT trial data for activities conducted in isothennic savannas.

1978年，国际热带农业中心（CIAT）的热带牧草项目联合活跃于牧草研究领域的各国国家级科研机构，牵头组建了国际热带牧草评估网络（Red Internacional de Evaluación de Pastos Tropicales，简称RIEPT）。其核心宗旨明确为：一是为该大陆广袤农业边疆区贫瘠酸性土壤中广泛分布的各类生产型生态系统寻觅新型牧草种质资源；二是基于种质资源可适配的生态系统及亚生态系统范围的研究成果，推导其适配边界；三是建设并推广网络内部的科研能力，以提升试验流程效率，进而以动态递进的方式将优质牧草种质纳入牧草种植体系，并将其应用于适配的生产系统中（Toledo，1982）。为达成上述目标，RIEPT依托代表主要生态系统的区域试验A（Regional Trials A，简称RTAs）——涵盖排水良好的恒热稀树草原与等温稀树草原、排水不良的稀树草原，以及多雨半常绿季节性热带森林——开展试验，并在上述5类主要生态系统内的亚生态系统代表性点位实施区域试验B（Regional Trials B，简称RTBs）。在区域试验A中，研究人员首先针对主要生态系统条件下的种质适配潜力开展评估，即测定种质的潜在存活能力。经筛选存活且表现出较高生产力的材料，将在区域试验B中接受亚生态系统条件的检验：该试验通过刈割处理开展评估，以测定其季节生产力（即分别在最大与最小降雨条件下），进而得到整合了适应性与生产潜力的评价指标。截至该阶段，所有评估均采用单作小区试验，仅用于筛选适配不同生态系统自然条件（土壤、气候、生物胁迫）的种质资源。通过统一的评估方法，研究人员可开展多地点分析，从而基于已明确的筛选种质适配范围进行外推。然而，此类农艺试验（区域试验A与B）完全不足以实现将新型牧草种质应用于该大陆农业边疆区畜牧生产系统的最终目标。为此，RIEPT提出分两阶段开展放牧条件下的区域试验。第一阶段即区域试验C（Regional Trials C，简称RTCs），旨在将新型牧草种质纳入种植体系，研究其在不同放牧管理系统下、小区尺度的放牧条件中的适配性，具体包括生产力（干物质产量与载畜量）及持久性（植物组成动态、植株结构变化与种子储备）。第二阶段为区域试验D（Regional Trials D，简称RTDs），将表现最优的牧草（基于生产力、持久性与管理便捷性）与传统种植的优质牧草开展对比试验。在该类试验中，研究人员将结合各区域主流生产系统的背景，测定以动物产品（牛肉、牛乳与犊牛）形式体现的牧草生产力。本数据集收录了在等温稀树草原中开展的RIEPT系列试验相关数据。