Experiments lasting multiple lifetimes?

In week 4 of our critical thinking tutorials, we tackled a comprehensive paper by Likens et al., (1970) describing the original Hubbard-Brook experiments. The study aimed to determine the effect of afforestation and herbicide application on:

  • The quantity of stream water flowing out of the watershed
  • Chemical relationships within the forest ecosystem (e.g. nutrient relationships and eutrophication).
The Hubbard Brook Experimental Forest.

The Hubbard Brook Experimental Forest

What did the study do that has never been done before?

In the 1960s, this was the first small watershed approach to study elemental budgets and cycles. Ultimately it is also the first study to have led to the development of a Long Term Ecological Research Network, which now plays a key role for long-term scientific studies in the United States.

We, as a group, were struck by the magnitude of the original study. The fact that the experiments were carried out on an entire watershed ecosystem with multiple watersheds to apply treatments to is incredible. Looking more into the ongoing study now, the study site has been expanded and encompasses even more individual watersheds so that multiple replications of the treatments can be applied. Although this was all impressive, we began to question how representative this study might be for watersheds in other environments with different site characteristics….

How widely should the conclusions of the study be applied?

We noticed the Hubbard Brook watersheds have certain site characteristics that may not be present in other watersheds throughout the world. For example, the area is surrounded by northern hardwood vegetation and the streams are located on watertight bedrock. Different site characteristics may influence the stream characteristics being measured. We acknowledged the difficulty of carrying out global experimentation and the lack of funds, which calls for a reasoned reduction in the number of study sites, perhaps focusing on ecologically important areas. Generally, no site can be representative of an entire region but extrapolation of local patterns to global scales is central to the application of research insights and policy-making.

More points on the study design…

We discussed what we would change if we could carry out the Hubbard Brooks experiment again. In general more samples of stream water and precipitation should be taken in time and space. More replicates of the actual watersheds would also be needed to ensure there was no pseudoreplication (see last week’s blog post!). We then began questioning the reason for the herbicide application and how this would affect the results. We also questioned whether the prevention of regrowth would prevent the ecosystem’s capacity to buffer the effects of deforestation.

Buffer Capacity and LTER

How important is the environment’s ability to buffer against disturbances? We stressed the importance of the buffering capacity of ecosystems for the future in light of climate change and ongoing human disturbance.

To monitor changes within ecosystems, such as stream flow and nutrient budgets, we discovered the Long Term Ecological Research Network. This is a network of study sites that are being monitored over several decades. The aim is to extract trends from data sets put together using common protocols and approaches. Originally we thought this was a great idea but questioned the feasibility of conducting such research over the world as a whole.


The US Long-term Ecological Research Network

Long-term trends can be valuable for testing individual effects of various factors (e.g. climate change and habitat destruction) and could be useful for policy making in the future. However, delving into the research network further, we discovered that the majority of funding comes from the National Science Foundation, and the grants are given in a 6-year renewal format. It is more difficult than we initially thought to get long-term funding, with the threat of being cut off after 6 years, which would significantly reduce the value of the long-term time series as a whole.

Overall, we did find the concept of a long-term research network useful and would encourage the idea of having something similar in Europe. Especially since the main aims of the American version are:

  • Make data more accessible to the broader scientific community using common data management protocols, cross-site and cross-agency research
  • Participate in network level and science synthesis activities

Perhaps the LTER concept can, if adopted throughout the world, contribute to developing more effective global data sets that will have generic data collection methods and metrics. In the future, this collaboration could reap major rewards for the analysis of long-term ecological data, which could result in more focused science and effective policy-making.

By Lisa


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