Climate change and biodiversity loss are severe and intertwined global threats. Land-based efforts to address both require an understanding of the spatial relationships between carbon storage and biodiversity. Here, we present a systematic review and meta-analysis of the strength of these spatial relationships across the literature. We synthesize the estimated spatial correlations and infer how different factors (spatial scale, metrics, biome, human pressure) impact these strengths using linear mixed-effect models. Our results show that spatial scale is a significant factor, and the combination of metrics used to express carbon storage and biodiversity plays a more important role. While relationships are moderately positive across all conditions, the strength of the relationships decreases significantly from global to local scales. We find large variations in the strength for different metrics, across different biomes, and in the presence or absence of human pressure. We find a stronger relationship in natural rather than human-dominated landscapes for temperate forests, grasslands and deserts, but the opposite for tropical and subtropical forests. Ecosystem-level biodiversity proxies (habitat quality) show strong relationships to the total carbon pool, while taxonomic metrics (species richness) show a weaker relationship. The largest negative relationship is between total carbon and flora & fauna species richness. Our results suggest different synergies for different dimensions of carbon storage and biodiversity and shed light on where further effort is needed.

1. Temperature is commonly acknowledged as one of the primary forces driving ectotherm vector populations, most notably by influencing metabolic rates and survival. Although numerous experiments have shown this for a wide variety of organisms, the vast majority has been conducted at constant temperatures and changes therein, while temperature is far from constant in nature, and includes seasonal and diurnal cycles. As fluctuating temperatures have been described to affect metabolic processes at (sub)cellular level, this calls for studies evaluating the relative importance of temperature fluctuations and the changes therein. 2. To gain insight in the effects of temperature fluctuations on ectotherm development, survival, and sex-ratio, we developed an inexpensive, easily reproducible, and open-source, Arduino-based temperature control system, which emulates natural sinusoidal fluctuations around the average temperature. We used this novel setup to compare the effects of constant (mean) temperatures, most commonly used in experiments, block schemes and natural sinusoidal fluctuations as well as an extreme variant with twice its amplitude using the cosmopolitan mosquito species Culex pipiens s.l. as a study organism. 3. Our system accurately replicated the preprogrammed temperature treatments under outdoor conditions, even more accurately than traditional methods. While no effects were detected on survival and sex-ratio within the ranges of variation evaluated, development was sped up considerably by including temperature fluctuations, especially during pupation, where development under constant temperatures took almost a week (30%) longer than under natural fluctuations. Doubling the amplitude further decreased development time by 1.5 days. 4. These results highlight the importance of including (natural) oscillations in experiments on ectotherm organisms – both aquatic and terrestrial – that use temperature as a variable. Ultimately, these results have major repercussions for downstream effects at larger scales that may be studied with applications such as ecological niche models, disease risk models and assessing ecosystem services that rely on ectotherm organisms.

The extramatrical mycelium of ectomycorrhizal fungi (EMF) is an important source of soil carbon. While the importance of recalcitrant compounds in the fungal cell wall has been reported earlier, the contribution of abundant and more labile components, like glucans, and the role of their temporal dynamics during decomposition remains unknown. We examined how the decomposition of EMF mycelium is related to the dynamics of 3 main fungal cell wall components; chitin, melanin, and glucans. Across six EMF species, the initial concentrations of the three components were not a good predictor of necromass loss after 6 weeks. However, the dynamics of chitin concentration during the decomposition process contributed to the weekly necromass degradation, with trends of chitin loss dynamics being dissimilar across the fungal species. In contrast, the dynamics of loss of melanin and glucans was not related to the weekly necromass loss. Given similar total necromass loss across species, we suggest that glucans and chitin are not discriminated by decomposers. This mechanism compensates for the interspecific difference in their initial concentration. Our results indicate that fungal necromass decomposition does not behave similarly to plant litter, while it is critical to soil carbon dynamics.