CONTEXT

Planting fruit trees in a market gardening system creates a mixed fruit tree – vegetable system with the potential to address certain environmental issues. However, it results in a complex system where labor has to be allocated between the two activities.

OBJECTIVE

Our objective is to simulate possible trajectories for a perennial transition from market gardening to mixed fruit tree – vegetable systems, in order to study the required trade-offs.

METHODS

We modeled the transition using viability theory, a framework with states, controls and constraints that guarantees sustainability along a transition trajectory. It was used in two iterations, the first step computing a target to be reached during the second step. Trajectory samples were computed from the sets of viable states at each time step.

RESULTS AND CONCLUSIONS

In order to guarantee sustainability, at the end of the transition process the farm must not only respect the constraints but belong to a subset of the domain they define. The study of viable trajectories shows a trade-off between capital and working hours, and thus different suitable strategies for the timing of orchard planting and the choice of crop rotations. Some strategies present bottlenecks where the flexibility of the farm is greatly reduced.

SIGNIFICANCE

The variety of resulting viable trajectories means that choosing between them can call upon criteria that are not implemented in the model, such as personal preferences. The establishment of a target through viability computation and the study of trajectory sets avoids the imposition of an a priori normativity.

中文翻译：

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从商品园艺到混合果树-蔬菜系统的常年过渡

语境

在商品园艺系统中种植果树会形成一个果树-蔬菜混合系统，有可能解决某些环境问题。然而，它会导致一个复杂的系统，其中必须在两个活动之间分配劳动力。

客观的

我们的目标是模拟从商品园艺到混合果树-蔬菜系统的常年过渡的可能轨迹，以研究所需的权衡。

方法

我们使用可行性理论对过渡进行建模，这是一个包含状态、控制和约束的框架，可确保沿过渡轨迹的可持续性。它用于两次迭代，第一步计算第二步要达到的目标。轨迹样本是根据每个时间步长的可行状态集计算的。

结果和结论

为了保证可持续性，在过渡过程结束时，农场不仅必须尊重约束，而且必须属于他们定义的域的子集。对可行轨迹的研究显示了资本和工作时间之间的权衡，以及果园种植时间和作物轮作选择的不同合适策略。一些策略存在瓶颈，农场的灵活性大大降低。

意义

由此产生的可行轨迹的多样性意味着在它们之间进行选择可以调用模型中未实现的标准，例如个人偏好。通过可行性计算和轨迹集研究建立目标避免了先验规范性的强加。