Search

• The degradation interpretation matrix guides decisions for UN SDG Indicator 15.3.1. • Some remediation activities can cause land to be classified as degraded. • Biophysical information alone is insufficient to determine land degradation state. The Land Degradation Neutrality Initiative of the UN Convention to Combat Desertification (UNCCD) encourages each of the 123 signatory countries to stabilise or reduce their extent of degraded land. Land degradation is assessed using the methods described in the Good Practice Guidance (GPG) document for Sustainable Development Goal (SDG) Indicator 15.3.1 (the proportion of land that is degraded over total land area), using three sub-indicators: land cover change, land productivity and soil organic carbon (SOC) stocks (as a proxy for carbon stocks above and below ground). The GPG identifies degraded areas by aggregating the sub-indicator assessments using a one-out-all-out (1OAO) approach, in which an area is identified as degraded if any one or more of the sub-indicators shows degradation i.e. a land cover transition defined as degradation, a reduction in productivity, and/or a reduction in SOC stocks. Under some circumstances, however, the 1OAO method can result in a counterintuitive degradation assessment, such as where the removal of invasive plant species reduces plant biomass, which would normally suggest degradation of net primary production, but which in this circumstance is considered a positive change in the context of land remediation activities. Each country has the opportunity to report areas within its sovereign bounds as an error of 'false positive' or 'false negative' degradation with sufficient justification, however it is vital that this is done in a way that ensures consistency of reporting amongst countries at regional and global scales. This paper describes scenarios in which the 1OAO process can lead to a counterintuitive degradation assessment, focusing on the potential impacts of invasive plants, woody encroachment (i.e. bush encroachment), and land remediation activities on SOC stocks as examples. We present an interpretation matrix to assist with determining how to report degradation in these cases, and help identify the drivers of degradation and potential remediation activities. Increased clarity around degradation labelling and interpretation could improve reporting consistency and transparency, and increase the efficiency and effectiveness of land degradation remediation actions. [ABSTRACT FROM AUTHOR]

The clearing of natural vegetation for agriculture has reduced the capacity of natural systems to provide ecosystem functions. Ecological restoration can restore desirable ecosystem functions, such as creating habitat for animal conservation and carbon sequestration as woody biomass. In order to maintain these beneficial ecosystem functions, restoration projects need to mature into self‐perpetuating communities. Here we compared the ecological attributes of two types of restoration, "active" tree plantings with "passive" natural forest regeneration ("natural regrowth") to existing remnant vegetation in a cleared agricultural landscape. Specifically, we measured differences between forest categories in factors that may predict future restoration failure or ecosystem collapse: aboveground plant biomass and biomass accrual over time (for regrowing stands), plant density and size class distributions, and diversity of functional groups based on seed dispersal and growth strategy traits. We found that natural regrowth and planted forests were similar in many ecological characteristics, including biomass accrual. Despite this, planted stands contained fewer tree recruit and shrub individuals, which may be due to limited recruitment in plantings. If this continues, these forests may be at risk of collapsing into nonforest states after mature trees senesce. Lower shrub density and richness of mid‐story trees may lead to lower structural complexity in planting plots, and alongside lower richness of fleshy‐fruited plant species may reduce animal resources and animal use of the restored stand. In our study region, natural regrowth may result in restored woodland communities with greater conservation and carbon mitigation value. [ABSTRACT FROM AUTHOR]

The article discusses an analysis of global patterns of variation in an individual tree. It examines the allocation of carbon acquired by plants from the atmosphere, studies with contradictory results regarding the causes of stand-level variation, and findings on correlation or interaction between tree size and climatic water deficit.

Accurate ground-based estimation of the carbon stored in terrestrial ecosystems is critical to quantifying the global carbon budget. Allometric models provide cost-effective methods for biomass prediction. But do such models vary with ecoregion or plant functional type? We compiled 15 054 measurements of individual tree or shrub biomass from across Australia to examine the generality of allometric models for above-ground biomass prediction. This provided a robust case study because Australia includes ecoregions ranging from arid shrublands to tropical rainforests, and has a rich history of biomass research, particularly in planted forests. Regardless of ecoregion, for five broad categories of plant functional type (shrubs; multistemmed trees; trees of the genus Eucalyptus and closely related genera; other trees of high wood density; and other trees of low wood density), relationships between biomass and stem diameter were generic. Simple power-law models explained 84-95% of the variation in biomass, with little improvement in model performance when other plant variables (height, bole wood density), or site characteristics (climate, age, management) were included. Predictions of stand-based biomass from allometric models of varying levels of generalization (species-specific, plant functional type) were validated using whole-plot harvest data from 17 contrasting stands (range: 9-356 Mg ha−1). Losses in efficiency of prediction were <1% if generalized models were used in place of species-specific models. Furthermore, application of generalized multispecies models did not introduce significant bias in biomass prediction in 92% of the 53 species tested. Further, overall efficiency of stand-level biomass prediction was 99%, with a mean absolute prediction error of only 13%. Hence, for cost-effective prediction of biomass across a wide range of stands, we recommend use of generic allometric models based on plant functional types. Development of new species-specific models is only warranted when gains in accuracy of stand-based predictions are relatively high (e.g. high-value monocultures). [ABSTRACT FROM AUTHOR]

• 441 root:shoot records were compiled for 32 locations in south temperate forests. • Root:shoot ratios were size-invariant in most tree taxa assessed. • Most dicots had similar root:shoot ratios between south and north temperate forests. • Divergences in root allocation were only noted for gymnosperms and tree ferns. • Low rainfall:temperature ratio conditions led to high root biomass allocation. Accurate quantification of total forest biomass requires sound estimates of root biomass. Because roots are challenging to measure in situ , data are sparse, and this has limited our understanding of root allocation across a range of forest types. Increased sampling in the oceanic and cool temperate forests of the southern hemisphere means we are now able to better understand biomass allocation in this biome. Here we compile and systematically review root:shoot ratios for these forests and examine the taxonomic, regional, and environmental determinants of variability in biomass allocation to roots. Specifically, we assess whether limited access to resources resulting from low temperatures or low rainfall:temperature ratios increases root allocation. A literature and database search identified 441 root:shoot records from 25 studies and 32 locations around the South Pacific. Records were weighted by excavated area as a measure of sampling effort. Root:shoot ratios for eucalypts in southeast Australia (0.277) and southern beech in South America (0.275) were 6–7% above the global mean of 0.26, while southern beech (0.233) and other dicots (0.234) in New Zealand were consistent with values reported for temperate (mostly northern hemisphere) broadleaved forests. Low root:shoot ratios (of trees ≥5 cm stem diameter) relative to the global mean were noted for South American gymnosperms (0.219), seemingly driven by low values in the Cupressaceae, and New Zealand tree ferns (0.194). Size effects were taxon dependent, with a marked decline in root:shoot ratios with increasing stem size for the southern beech in South America and modest effects for other combinations of taxa and region. A clear signal of increasing root allocation with declining rainfall:temperature ratios was detected, but no major effects of temperature were noted within the range of the data. Our findings support current approaches to biomass and carbon estimation but leave room for refinement, with specific recommendations given for the New Zealand context. [ABSTRACT FROM AUTHOR]