RIEPT Trials - Ecosystems H: Isohyperthennic 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 isohyperthennic savannas.1978年，国际热带农业中心（CIAT）的热带牧草项目联合全球活跃于牧草研究的国家级科研机构，牵头组建了国际热带牧草评价网络（Red Internacional de Evaluación de Pastos Tropicales，简称RIEPT）。该网络的核心宗旨为：一是为美洲大陆广袤边远农业区域的贫瘠酸性土壤中广泛分布的各类生产型生态系统筛选新型牧草种质资源；二是基于种质资源可适配的生态系统及亚生态系统范围，构建适配推演模型；三是培养并提升网络内部的科研能力，以优化试验流程，进而以动态有序的方式将优良牧草种质纳入种植体系，并应用于适配的生产系统（Toledo, 1982）。 为达成上述目标，RIEPT依托代表主要生态类型的区域试验A（Regional Trials A，简称RTAs）——涵盖排水良好的恒湿热带稀树草原、恒温热带稀树草原、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点位开展区域试验B（Regional Trials B，简称RTBs）。在RTAs中，首先针对种质在对应主要生态系统条件下的适配潜力开展评价，即评估种质的潜在存活能力。存活且表现出较高生产性能的材料，将在RTBs中接受亚生态系统条件下的评价：通过刈割处理测定其季节生产性能（即在最大和最小降雨量条件下），以综合衡量其适应性与生产潜力。截至该阶段，所有评价均采用小面积单一种植模式，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。通过统一的评价方法，可开展多地点分析，进而推演筛选出的种质资源的已知适配范围。 然而，此类农艺试验（RTAs与RTBs）仍不足以实现最终目标——将新型牧草种质资源应用于美洲大陆边远农业区域的畜牧生产系统。为此，RIEPT提出分两阶段开展放牧条件下的区域试验：第一阶段为区域试验C（Regional Trials C，简称RTCs），旨在将新型牧草种质纳入种植体系，在小面积地块中研究不同放牧管理系统下，牧草在放牧条件下的适配性，具体包括生产性能（干物质产量（dry-matter yields）与载畜量（carrying capacity））及持久性（植物组成（botanical composition）动态、植株结构（plant architecture）变化与种子储备（seed reserves）变化）。第二阶段为区域试验D（Regional Trials D，简称RTDs），将在生产性能、持久性与管理便利性方面表现最优的牧草，与传统主推牧草开展对比试验。此类试验将结合各区域主流生产系统，测定牧草转化为动物产品（牛肉、牛乳与犊牛）的生产效率。 本数据集收录了恒湿热带稀树草原区域内RIEPT相关试验的数据。