The 2011 Philip C. Jessup International Law

The State of Rigalia and the State of Ardenia submit the present dispute concerning the Zetian Provinces to the International Court of Justice by Special Agreement, dated 5 May 2010, pursuant to article 40(1) of the Statute of the International Court ofJustice

Andean grasslands are as productive as tropical cloud forests

We aim to assess net primary productivity (NPP) and carbon cycling in Andean tropical alpine grasslands (puna) and compare it with NPP of tropical montane cloud forests. We ask the following questions: (1) how do NPP and soil respiration of grasslands vary over the seasonal cycle? (2) how do burning and grazing affect puna productivity? (3) if the montane forest expands into the puna, what will be the resulting change in productivity? The study sites are located at the South-eastern Peruvian Andes; one grassland site and the forest sites are in Wayqecha biological station, and another grassland site in Manu National Park. At each grassland site, we selected a burnt and an unburnt area, installed unfenced and fenced transects in each area, and monitored above-ground productivity (NPPAG), below-ground productivity (NPPBG) and soil respiration (Rs) for 2 yr. In the forest, we monitored NPPAG, NPPBG and Rs for 2–4 yr. Grassland NPP varied between 4.6 ± 0.25 (disturbed areas) to 15.3 ± 0.9 Mg C ha-1 yr-1 (undisturbed areas) and cloud forest NPP was between 7.05 ± 0.39 and 8.0 ± 0.47 Mg C ha-1 yr-1, while soil carbon stocks were in the range of 126 ± 22 to 285 ± 31Mg C ha-1. There were no significant differences on NPP between the puna and forest sites. The most undisturbed site had significantly higher NPP than other grassland sites, but no differences were found when relating grazing and fire at other sites. There were lower residence times of above-ground biomass compared to below-ground biomass. There was a strong seasonal signal on grassland NPPAG and NPPBG, with a shift on allocation at the beginning of the austral summer. High elevation tropical grasslands can be as productive as adjacent cloud forests, but have very different carbon cycling and retention properties than cloud forests. S Online supplementary data available from stacks.iop.org/ERL/9/115011/mmedia Keywords: tropical alpine wetlands, above-ground productivity, below-ground productivity, fire, grazing, disturbances, pun

Plant trait and vegetation data along a 1314 m elevation gradient with fire history in Puna grasslands, Per\ufa

\ua9 2024. The Author(s). Alpine grassland vegetation supports globally important biodiversity and ecosystems that are increasingly threatened by climate warming and other environmental changes. Trait-based approaches can support understanding of vegetation responses to global change drivers and consequences for ecosystem functioning. In six sites along a 1314 m elevational gradient in Puna grasslands in the Peruvian Andes, we collected datasets on vascular plant composition, plant functional traits, biomass, ecosystem fluxes, and climate data over three years. The data were collected in the wet and dry season and from plots with different fire histories. We selected traits associated with plant resource use, growth, and life history strategies (leaf area, leaf dry/wet mass, leaf thickness, specific leaf area, leaf dry matter content, leaf C, N, P content, C and N isotopes). The trait dataset contains 3,665 plant records from 145 taxa, 54,036 trait measurements (increasing the trait data coverage of the regional flora by 420%) covering 14 traits and 121 plant taxa (ca. 40% of which have no previous publicly available trait data) across 33 families

Basin-wide variation in tree hydraulic safety margins predicts the carbon balance of Amazon forests

Tropical forests face increasing climate risk1,2, yet our ability to predict their response to climate change is limited by poor understanding of their resistance to water stress. Although xylem embolism resistance thresholds (for example, Ψ50) and hydraulic safety margins (for example, HSM50) are important predictors of drought-induced mortality risk3–5, little is known about how these vary across Earth’s largest tropical forest. Here, we present a pan-Amazon, fully standardized hydraulic traits dataset and use it to assess regional variation in drought sensitivity and hydraulic trait ability to predict species distributions and long-term forest biomass accumulation. Parameters Ψ50 and HSM50 vary markedly across the Amazon and are related to average long-term rainfall characteristics. Both Ψ50 and HSM50 influence the biogeographical distribution of Amazon tree species. However, HSM50 was the only significant predictor of observed decadal-scale changes in forest biomass. Old-growth forests with wide HSM50 are gaining more biomass than are low HSM50 forests. We propose that this may be associated with a growth–mortality trade-off whereby trees in forests consisting of fast-growing species take greater hydraulic risks and face greater mortality risk. Moreover, in regions of more pronounced climatic change, we find evidence that forests are losing biomass, suggesting that species in these regions may be operating beyond their hydraulic limits. Continued climate change is likely to further reduce HSM50 in the Amazon6,7, with strong implications for the Amazon carbon sink

Basin-wide variation in tree hydraulic safety margins predicts the carbon balance of Amazon forests

This is the final version. Available on open access from Nature Research via the DOI in this recordData availability: The pan-Amazonian HT dataset (Ψ 50, Ψ dry and HSM50) and branch wood density per species per site, as well as forest dynamic and climate data per plot presented in this study are available as a ForestPlots.net data package at https://forestplots.net/data-packages/Tavares-et-al-2023. Basal area weighted mean LMA is shown in Supplementary Table 2. Species stem wood density data were obtained from Global Wood Density database65,66. Species WDA data were extracted from ref. 45.Code availability: The codes to recreate the main analyses and the main figures presented in this study are available as a ForestPlots.net data package at https://forestplots.net/data-packages/Tavares-et-al-2023.Tropical forests face increasing climate risk, yet our ability to predict their response to climate change is limited by poor understanding of their resistance to water stress. Although xylem embolism resistance thresholds (for example, Ψ 50) and hydraulic safety margins (for example, HSM50) are important predictors of drought-induced mortality risk, little is known about how these vary across Earth’s largest tropical forest. Here, we present a pan-Amazon, fully standardized hydraulic traits dataset and use it to assess regional variation in drought sensitivity and hydraulic trait ability to predict species distributions and long-term forest biomass accumulation. Parameters Ψ 50 and HSM50 vary markedly across the Amazon and are related to average long-term rainfall characteristics. Both Ψ 50 and HSM50 influence the biogeographical distribution of Amazon tree species. However, HSM50 was the only significant predictor of observed decadal-scale changes in forest biomass. Old-growth forests with wide HSM50 are gaining more biomass than are low HSM50 forests. We propose that this may be associated with a growth–mortality trade-off whereby trees in forests consisting of fast-growing species take greater hydraulic risks and face greater mortality risk. Moreover, in regions of more pronounced climatic change, we find evidence that forests are losing biomass, suggesting that species in these regions may be operating beyond their hydraulic limits. Continued climate change is likely to further reduce HSM50 in the Amazon, with strong implications for the Amazon carbon sink

Many shades of green: the dynamic tropical forest–savannah transition zones

The forest-savanna transition is the most widespread ecotone in tropical areas, separating two of the most productive terrestrial ecosystems. Here we review current understanding of the factors that shape this transition, and how it may change under various drivers of local or global change. At broadest scales the location of the transition is shaped by water availability, mediated strongly at local scales by fire regimes, herbivory pressure and spatial variation in soil properties. The frequently dynamic nature of this transition suggests that forest and savanna can exist as alternative stable states, maintained and separated by fire-grass feedbacks and tree shade-fire suppression feedback. However, this theory is still contested and the relative contributions of the main biotic and abiotic drivers and their interactions are yet not fully understood. These drivers interplay with a wide range of ecological processes and attributes at the global, continental, regional and local scales. The evolutionary history of the biotic and abiotic drivers and processes plays an important role on the current distributions of these transitions as well as in their species composition and ecosystem functioning. This ecotone can be sensitive to shifts in climate and other driving factors, but is also potentially stabilised by negative feedback processes. There is abundant evidence that these transitions are shifting under contemporary global and local change, but the direction of shift varies according to region. However, it still remains uncertain how these transitions will respond to rapid and multi-faceted ongoing current changes, and how increasing human influence will interact with these shifts

Many shades of green: the dynamic tropical forest–savannah transition zones

The forest-savanna transition is the most widespread ecotone in tropical areas, separating two of the most productive terrestrial ecosystems. Here we review current understanding of the factors that shape this transition, and how it may change under various drivers of local or global change. At broadest scales the location of the transition is shaped by water availability, mediated strongly at local scales by fire regimes, herbivory pressure and spatial variation in soil properties. The frequently dynamic nature of this transition suggests that forest and savanna can exist as alternative stable states, maintained and separated by fire-grass feedbacks and tree shade-fire suppression feedback. However, this theory is still contested and the relative contributions of the main biotic and abiotic drivers and their interactions are yet not fully understood. These drivers interplay with a wide range of ecological processes and attributes at the global, continental, regional and local scales. The evolutionary history of the biotic and abiotic drivers and processes plays an important role on the current distributions of these transitions as well as in their species composition and ecosystem functioning. This ecotone can be sensitive to shifts in climate and other driving factors, but is also potentially stabilised by negative feedback processes. There is abundant evidence that these transitions are shifting under contemporary global and local change, but the direction of shift varies according to region. However, it still remains uncertain how these transitions will respond to rapid and multi-faceted ongoing current changes, and how increasing human influence will interact with these shifts

Application of remote sensing to understanding fire regimes and biomass burning emissions of the tropical Andes

In the tropical Andes, there have been very few systematic studies aimed at understanding the biomass burning dynamics in the area. This paper seeks to advance on our understanding of burning regimes in this region, with the first detailed and comprehensive assessment of fire occurrence and the derived gross biomass burning emissions of an area of the Peruvian tropical Andes. We selected an area of 2.8 million hectares at altitudes over 2000¿m. We analyzed fire occurrence over a 12 year period with three types of satellite data. Fire dynamics showed a large intra-annual and interannual variability, with most fires occurring May–October (the period coinciding with the dry season). Total area burned decreased with increasing rainfall until a given rainfall threshold beyond which no relationship was found. The estimated fire return interval (FRI) for the area is 37¿years for grasslands, which is within the range reported for grasslands, and 65¿years for forests, which is remarkably shorter than other reported FRI in tropical moist forests. The greatest contribution (60–70%, depending on the data source) to biomass burning emissions came from burned montane cloud forests (4.5 million Mg CO2 over the study period), despite accounting for only 7.4–10% of the total burned area. Gross aboveground biomass emissions (7.55¿±¿2.14 Tg CO2; 0.43¿±¿0.04 Tg CO; 24,012¿±¿2685¿Mg CH4 for the study area) were larger than previously reported for the tropical Andes

Deciphering the stability of grassland productivity in response to rainfall manipulation experiments

Aim Rainfall manipulation experiments are essential tools for deciphering the mechanisms leading to variation in ecosystem stability across sites. Here, we gathered articles reporting results of experimental droughts on the above‐ground biomass of grasslands to identify which indices have been used to assess stability, to evaluate the overall grassland responses to drought and to quantify the relative importance of drought characteristics and climatic conditions for explaining variation in stability. Location Global. Time period 1989–2018. Major taxa studied Grasslands. Methods We used meta‐analytical approaches to evaluate overall grassland stability in terms of resistance, recovery and resilience, and multi‐model inference to assess the relative importance of different moderators on explaining the variability of those three stability properties. Results Numerous indices of stability have been used, but they are inadequate for comparisons across sites. After applying standardized indices, we found that grasslands were resilient (biomass remained unchanged 1 year after drought) and exhibited a trade‐off between low resistance (biomass was lost during drought) and high recovery (new biomass was produced after drought). Overall, climatic conditions and drought characteristics (intensity, duration and frequency) were not important to explain the differences in stability observed across grasslands. Main conclusions Grasslands are resilient, but if drought events last > 1 year, there might be long‐term declines of biomass production owing to incomplete recovery. Despite the hundreds of experiments conducted in grasslands across the globe, the results are still inconclusive because of four important shortcomings: 50% of the studies have failed to create drought; 81% have not included recovery and resilience, assessing only resistance; 87% have not applied quantitative indices to assess stability; and < 1% of the studies were conducted on tropical grasslands. We discuss how to overcome those limitations to improve our ability to ensure stable grassland productivity under climate change

Deciphering the stability of grassland productivity in response to rainfall manipulation experiments

Aim Rainfall manipulation experiments are essential tools for deciphering the mechanisms leading to variation in ecosystem stability across sites. Here, we gathered articles reporting results of experimental droughts on the above‐ground biomass of grasslands to identify which indices have been used to assess stability, to evaluate the overall grassland responses to drought and to quantify the relative importance of drought characteristics and climatic conditions for explaining variation in stability. Location Global. Time period 1989–2018. Major taxa studied Grasslands. Methods We used meta‐analytical approaches to evaluate overall grassland stability in terms of resistance, recovery and resilience, and multi‐model inference to assess the relative importance of different moderators on explaining the variability of those three stability properties. Results Numerous indices of stability have been used, but they are inadequate for comparisons across sites. After applying standardized indices, we found that grasslands were resilient (biomass remained unchanged 1 year after drought) and exhibited a trade‐off between low resistance (biomass was lost during drought) and high recovery (new biomass was produced after drought). Overall, climatic conditions and drought characteristics (intensity, duration and frequency) were not important to explain the differences in stability observed across grasslands. Main conclusions Grasslands are resilient, but if drought events last > 1 year, there might be long‐term declines of biomass production owing to incomplete recovery. Despite the hundreds of experiments conducted in grasslands across the globe, the results are still inconclusive because of four important shortcomings: 50% of the studies have failed to create drought; 81% have not included recovery and resilience, assessing only resistance; 87% have not applied quantitative indices to assess stability; and < 1% of the studies were conducted on tropical grasslands. We discuss how to overcome those limitations to improve our ability to ensure stable grassland productivity under climate change