Background The programme of work on agricultural biodiversity, adopted by the Conference of Parties in decision V/5, makes provision for case studies on various topics to identify management practices, technologies and policies that promote the positive and mitigate the negative impacts of agriculture on biodiversity, and enhance productivity and the capacity to sustain livelihoods. More specifically, activity 2.1 of the Programme of Work calls for a series of case studies, in a range of environments and production systems, and in each region: (a) To identify key goods and services provided by agricultural biodiversity, needs for the conservation and sustainable use of components of this biological diversity in agricultural ecosystems, and threats to such diversity;

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Convention on Biological Diversity

1 Possible patterns in nutrient resorption efficiency (% of the leaf nutrient pool resorbed) from senescing leaves of perennials were examined at both the intra- and the interspecific level. Most of the data used originated from studies with evergreen and deciduous shrubs and trees. 2 Combining all data, mean nutrient resorption efficiency was 50% for N (n = 287) and 52% for P (n = 226). N resorption efficiency of evergreen shrubs and trees (47%) was significantly lower than in deciduous shrubs and trees (54%), whereas P resorption efficiency did not differ significantly between these growth-forms (51 and 50%, respectively). Although nutrient resorption is an important nutrient conservation mechanism at the species level, it does not differ strongly between growth-forms. 3 Mean N and P concentrations in leaves of deciduous shrubs and trees were about 60% higher than in evergreen species. There were only small differences in mean resorption efficiency and nutrient concentrations in leaf litter of deciduous species were therefore much higher than in evergreens. This implies that, in comparison with deciduous species, the low nutrient concentrations in mature leaves of evergreens contribute far more to nutrient conservation than does nutrient resorption. 4 Relations between leaf nutrient status and leaf nutrient resorption were absent or very weak. Assuming that leaf nutrient status reflects nutrient availability, this implies that nutrient resorption is only weakly controlled by nutrient availability. 5 At the intraspecific level, nutrient resorption was not very responsive to increased nutrient availability. There was no response in 63% of the experiments analysed (covering 60 spp.), whereas in 32% there was a decrease in N resorption in response to increased nutrient availability. For P (37 species analysed) there was no response in 57% of the cases and in 35% of the cases P resorption decreased upon enhanced nutrient supply. Evergreen shrubs and trees showed especially low responsiveness. 6 This review shows that there are no clear nutritional controls on nutrient resorption efficiency. Future research should focus on the biochemical basis of variation in nutrient resorption efficiency and on the factors, other than nutrient availability, that control nutrient resorption efficiency.

https://www.jstor.org/stable/pdfplus/2261481.pdf

Nutrient resorption from senescing leaves of perennials: are there general patterns?

Leaf area index (LAI) is a key structural characteristic of forest ecosystems because of the role of green leaves in controlling many biological and physical processes in plant canopies. Accurate LAI estimates are required in studies of ecophysiology, atmosphere-ecosystem interactions, and global change. The objective of this paper is to evaluate LAI values obtained by several research teams using different methods for a broad spectrum of boreal forest types in support of the international Boreal Ecosystem-Atmosphere Study (BOREAS). These methods include destructive sampling and optical instruments: the tracing radiation and architecture of canopies (TRAC), the LAI-2000 plant canopy analyzer, hemispherical photography, and the Sunfleck Ceptometer. The latter three calculate LAI from measured radiation transmittance (gap fraction) using inversion models that assume a random spatial distribution of leaves. It is shown that these instruments underestimate LAI of boreal forest stands where the foliage is clumped. The TRAC quantifies the clumping effect by measuring the canopy gap size distribution. For deciduous stands the clumping index measured from TRAC includes the clumping effect at all scales, but for conifer stands it only resolves the clumping effect at scales larger than the shoot (the basic collection of needles). To determine foliage clumping within conifer shoots, a video camera and rotational light table system was used. The major difficulties in determining the surface area of small conifer needles have been largely overcome by the use of an accurate volume displacement method. Hemispherical photography has the advantage that it also provides a permanent image record of the canopies. Typically, LAI falls in the range from 1 to 4 for jack pine and aspen forests and from 1 to 6 for black spruce. Our comparative studies provide the most comprehensive set of LAI estimates available for boreal forests and demonstrate that optical techniques, combined with limited direct foliage sampling, can be used to obtain quick and accurate LAI measurements.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/97JD01107

Leaf area index of boreal forests: theory, techniques, and measurements

Use of fluorochromes for direct enumeration of total bacteria in environmental samples: past and present.

Although trees have responded to global warming in the past - to temperatures higher than they are now - the rate of change predicted in the 21st century is likely to be unprecedented. Greenhouse gas emissions could cause a 3-6°C increase in mean land surface temperature at high and temperate latitudes. Despite this, few experiments have isolated the effects of temperature for this scenario on trees and forests. This review focuses on tree and forest responses at boreal and temperate latitudes, ranging from the cellular to the ecosystem level. Adaptation to varying temperatures revolves around the trade-off between utilizing the full growing season and minimizing frost damage through proper timing of hardening in autumn and dehardening in spring. But the evolutionary change in these traits must be sufficiently rapid to compensate for the temperature changes. Many species have a positive response to increased temperature - but how close are we to the optima? Management is critical for a positive response of forest growth to a warmer climate, and selection of the best species for the new conditions will be of vital importance. Contents Summary 369 I. Introduction 370 II. Photosynthesis and respiration 370 III. Soil organic matter decomposition and mineralization 373 IV. Phenology and frost hardiness 376 V. Whole tree experimental responses to warming 380 VI. Changes in species distribution at warmer temperatures 381 VII. Adaptation and evolution 383 VIII. Ecosystem level responses to warming 387 Acknowledgements 390 References 390 Appendix I. Temperature response functions 399.

https://nph.onlinelibrary.wiley.com/doi/pdf/10.1046/j.1469-8137.2001.00057.x

Tree and forest functioning in response to global warming

Forest plantations in the early stages of establishment are considered as hierarchical biological systems, and some implications for the design of research projects and the education of regeneratio...

An ecophysiological basis for understanding plantation establishment

Intensive Silvicultural Treatment: Impacts on Soil Fertility and Planted Conifer Response

The establishment of boreal and sub-boreal conifer plantations : an integrated analysis of environmental conditions and seedling growth

A factorial experiment was used to examine the effects of soil temperature, brush competition, and fertility on the postplanting growth and development of white spruce (Piceaglauca (Moench) Voss) a...

Growth and acclimation of planted white pine and white spruce seedlings in response to environmental conditions

Since June 1992, significant progress has been made in defining sustainable forest management. The approach taken has been to establish criteria and indicators of sustainable forest management. The criteria constitute a set of key elements that define the scope of the concept of sustainable forest management. They reflect a series of broadly held societal values—the environmental, social and economic benefits of forests that should be maintained for future generations. Indicators are chosen to provide measurable features of each criterion. These criteria and indicators should serve a number of purposes, by providing (1) a set of key terms that can be used in future international discussions on forests, (2) a framework against which countries can evaluate their forest policies, (3) a mechanism for rationalizing and evaluating international aid and technical cooperation programs, and (4) a means of resolving difficulties in international discussions on trade in products from sustainably managed forests. The criteria and indicators have been developed through a series of regional and international processes that are very similar in approach. The challenge now is to put them into practice, to refine the measurement and definition of the indicators, and to explore linkages between national-level criteria and indicators and the implementation of sustainable forest management at the working level.

David G. Brand

Papers

An ecophysiological basis for understanding plantation establishment

Intensive Silvicultural Treatment: Impacts on Soil Fertility and Planted Conifer Response

The establishment of boreal and sub-boreal conifer plantations : an integrated analysis of environmental conditions and seedling growth

Growth and acclimation of planted white pine and white spruce seedlings in response to environmental conditions

Criteria and indicators for the conservation and sustainable management of forests: Progress to date and future directions