A new study reveals that dead trees store considerably more carbon than previously estimated, playing a significant role in the global carbon cycle. Researchers found that decay rates in deadwood are influenced more by climate and wood traits than by insects and fungi, with drier climates preserving deadwood and its stored carbon for longer periods. This finding challenges existing climate models, which may underestimate the carbon storage capacity of forests, especially as climate change leads to drier conditions in some regions. The slow decay in dry climates suggests these dead trees represent a substantial, long-term carbon sink that must be accounted for to accurately predict future atmospheric carbon dioxide levels.
Terry Tao explores the problem of efficiently decomposing a large factorial n! into a product of factors of roughly equal size √n. He outlines several approaches, including a naive iterative method that repeatedly divides n! by the largest integer below √n, and a more sophisticated approach leveraging prime factorization. The prime factorization method cleverly groups primes into products close to the target size, offering significant computational advantages. While both methods achieve the desired decomposition, the prime factorization technique highlights the interplay between the smooth structure of factorials (captured by their prime decomposition) and the goal of obtaining uniformly large factors. Tao emphasizes the efficiency gains from working with the prime factorization, and suggests potential generalizations and connections to other mathematical concepts like smooth numbers and the Dickman function.
Hacker News users discussed the surprising difficulty of factoring large factorials, even when not seeking prime factorization. One commenter highlighted the connection to cryptography, pointing out that if factoring factorials were easy, breaking RSA would be as well. Another questioned the practical applications of this type of factorization, while others appreciated the mathematical puzzle aspect. The discussion also touched upon the computational complexity of factoring and the effectiveness of different factoring algorithms in this specific context. Some commenters shared resources and further reading on related topics in number theory. The general sentiment was one of appreciation for the mathematical curiosity presented by Terry Tao's blog post.
This 1972 paper by Parnas compares two system decomposition strategies: one based on flowcharts and step-wise refinement, and another based on information hiding. Parnas argues that decomposing a system into modules based on hiding design decisions behind interfaces leads to more stable and flexible systems. He demonstrates this by comparing two proposed modularizations of a KWIC (Key Word in Context) indexing system. The information hiding approach results in modules that are less interconnected and therefore less affected by changes in implementation details or requirements. This approach prioritizes minimizing inter-module communication and dependencies, making the resulting system easier to modify and maintain in the long run.
HN commenters discuss Parnas's modularity paper, largely agreeing with its core principles. Several highlight the enduring relevance of information hiding and minimizing inter-module dependencies to reduce complexity and facilitate change. Some commenters share anecdotes about encountering poorly designed systems violating these principles, reinforcing the paper's importance. The concept of "secrets" as the basis of modularity resonated, with discussions about how it applies to various levels of software design, from low-level functions to larger architectural components. A few commenters also touch upon the balance between pure theory and practical application, acknowledging the complexities of real-world software development.
Summary of Comments ( 45 )
https://news.ycombinator.com/item?id=43681679
HN commenters largely discussed the methodology of the study, questioning whether the 5-year timeframe was sufficient to draw long-term conclusions about carbon sequestration in deadwood. Some pointed out the potential for rapid decomposition in certain environments or due to insect activity, while others emphasized the importance of distinguishing between different types of trees and decay processes. Several users highlighted the interconnectedness of forest ecosystems, noting the role of deadwood in supporting fungi, insects, and soil health, ultimately influencing overall carbon storage. A few commenters also questioned the practical implications of the research, wondering if it justified leaving dead trees in place versus utilizing them for biofuel or other purposes. There was also discussion of the article's somewhat misleading title, as the study focuses on the rate of carbon release, not the absolute amount stored.
The Hacker News post titled "Dead trees keep surprisingly large amounts of carbon out of atmosphere" generated a modest discussion with a few interesting points.
Several commenters questioned the methodology and interpretation of the study. One commenter pointed out the apparent contradiction between the article stating that deadwood accounts for 10.9% of forest carbon storage, while also claiming it keeps a "surprisingly large" amount of carbon out of the atmosphere. They argued that 10.9% doesn't seem particularly large, especially when considering the total carbon storage capacity of living trees and soil. This commenter also highlighted the importance of distinguishing between above-ground and below-ground biomass, as well as different decomposition rates in various climates.
Another commenter delved into the complexities of carbon cycling, emphasizing that dead trees don't "keep" carbon out of the atmosphere indefinitely. They explained that decomposition ultimately releases the stored carbon back into the atmosphere. This comment emphasized the importance of understanding the timescale involved in these processes and the dynamic nature of carbon flow within an ecosystem. Furthermore, they highlighted how human interventions, such as logging practices and prescribed burns, influence the decomposition rate and subsequent carbon release.
A different commenter raised the issue of the study's focus on North American forests. They suggested that extrapolating these findings to global forests might be problematic, given the variability in forest composition, climate, and decomposition rates across different regions. This underscores the need for more research to understand the role of deadwood in carbon storage in diverse ecosystems worldwide.
Finally, one commenter expressed skepticism about the study's claim that dead trees contribute to a "net cooling effect." They argued that while shading might have a localized cooling effect, the decomposition process releases heat, potentially offsetting any cooling benefits. This comment highlighted the complex interplay of factors influencing overall temperature regulation in forest ecosystems.
While the discussion wasn't extensive, these comments brought up critical aspects related to the interpretation of the study's findings, including the relative significance of the 10.9% figure, the dynamic nature of carbon cycling, regional variations in forest ecosystems, and the complexities of the study's cooling effect claim.