R.W. Verburg

Effects of fire and selective logging on the tree species composition of lowland dipterocarp forest in East Kalimantan, Indonesia

Tree species composition (diameter at breast height (dbh) ≥ 10 cm) was studied in primary, selectively logged and heavily burnt forests in East Kalimantan, Indonesia. The number of trees, tree species, and the Fisherss-α diversity index were determined for the first 15 years (burnt forest) and 25 years (selectively logged forest) after disturbance. Additionally the population structure of six common and typical Macaranga pioneer tree species was compared through time between selectively logged, burnt and primary forest. Both selectively logged and burnt forest showed a significant reduction in number of trees and tree species per surface area directly after disturbance. Fire especially affected dominant tree species, while for selective logging the opposite was observed. In selectively logged forest the number of trees, tree species and the Fisherss-α index reached pre-disturbance levels within c. 15 years. For burnt forest, only the number of trees recovered to pre-disturbance levels. The number of tree species stayed constant after disturbance, while the Fisherss-α index decreased. The six studied Macaranga pioneer tree species seedlings were present in all forest types. Their density seems to be unrelated to light levels in the forest understorey but strongly related to the number of mature parent trees. Their sapling densities were strongly related to light levels in the forest understorey. The studied Macaranga species formed an important part of both under- and over-storey in burnt forest 15 years after disturbance, while they were almost absent in the understorey and only moderately common in the overstorey of selectively logged forest.

Effects of selective logging on tree diversity, composition and plant functional type patterns in a Bornean rain forest

The effects of selective logging on tree diversity, changes in tree species composition and plant functional types were studied with the use of seven permanent plots in virgin and in logged forest. All plots were located in a lowland dipterocarp rain forest in East Kalimantan on the island of Borneo. Just after logging and during the following 20 yr tree diversity measured as Fishers’ a was not significantly affected in logged forest plots. Temporal shifts in tree species composition were analysed with Principal Component Analysis (PCA). Logged forest plots had much larger changes over time than virgin forest plots. In the smallest diameter class, some logged forest plots showed a distinct trajectory in PCA space compared to virgin forest plots, while in larger diameter classes movement of logged plots in PCA space was random. This suggests that there is no predetermined community to which logged forest plots tend to shift when recovering from logging. We found a significant negative correlation between diameter increments and the species-specific wood densities of tree species. Species-specific wood density and potential tree height were used to assign species to five PFTs. As expected, logging increased the fraction of softwood stems in small diameter classes. In the largest diameter classes (> 50 cm DBH) a strong decrease of softwood emergent stems was found in logged forest plots. After more than 20 yr no recruitment was found of softwood emergent stems in selectively logged forest.

The effect of plant size on vegetative reproduction in a pseudo-annual

The relationship between plant size and vegetative reproduction in clonal plants appears complex because vegetative expansion, growth, and reproduction are not clearly separable in such plants. In ‘pseudo-annuals’, which are clonal plants surviving the winter only as seeds and hibernacles produced by the rhizome apices, vegetative growth and reproduction are clearly separate processes so that the relationship between vegetative reproduction and plant size can be studied. We used the pseudo-annual Helianthus x laetiflorus Pers. to study the relationship between plant size and total rhizome biomass, rhizome (hibernacle) biomass, and number of hibernacles. We manipulated resource acquisition of the plants by reducing leaf area (leaf-clipping) and by fertilization, thus affecting plant size. Furthermore, we studied the success of thin and thick hibernacles in terms of future growth and reproduction in a separate experiment. The results showed that vegetative reproduction was positively related to plant size. The ratio between the number of hibernacles and mean hibernacle weight was affected by plant size in such a way that in small plants both number of hibernacles and mean hibernacle weight were reduced to the same extent as compared to those in large plants. However, the size distributions of plants of the next generation growing from thin and thick hibernacles did not differ. It remains unclear therefore why this pseudo-annual species produces thick hibernacles at all.

Differences in allocation patterns in clonal and sexual offspring in a woodland pseudo-annual

Abstract We compared the patterns of allocation to reproduction among seed-derived and clonal offspring of a woodland pseudo-annual. Pseudo-annuals are clonal plants which survive the winter only as seeds and hibernacles produced by the rhizome system. Previous studies indicate that flowering is related to the size of these hibernacles. Since seedlings do not have a hibernacle, we did not expect that these plants would reproduce sexually. Assuming a trade-off between sexual and asexual reproduction, and assuming a linear relationship between vegetative plant weight and weight of all reproductive structures (i.e., rhizomes, hibernacles, inflorescences, and seeds), we expected that seed-derived plants would have a stronger biomass allocation to rhizomes and hibernacles. Since resource supply affects plant size, and thus hibernacle and seed production, we also subjected the plants to different levels of shade. At the start of the experiment seed-derived and clonal offspring hardly differed in total fresh weight. At the final harvest in September seed-derived and clonal offspring did not differ in vegetative plant weight (i.e., leaves, stems, and roots). Only light availability significantly affected these plant structures. As predicted, seed-derived plants did not flower in either of the light treatments. Seed-derived plants allocated more biomass to rhizomes and hibernacles, but this was only significant in the highest-light treatment. This result was due only to an increase in the number of hibernacles. Dry weight of single hibernacles was not affected by plant type. The ecological implications of this allocation pattern are discussed.

Inherent allocation patterns and potential growth rates of herbaceous climbing plants

We tested the hypothesis that herbaceous climbing plants, unlike non-climbing herbs, maximize height growth and leaf area, with minimal expenditure in support structures. The enhanced investment in leaf area was expected to result in high relative growth rates in terms of biomass increment.Four leguminous herbaceous climbers from nutrient-poor sites and four non-leguminous herbaceous climbers from nutrient-rich sites, were compared with non-climbing, self-supporting leguminous and non-leguminous herbaceous species from similar habitats. Plants were grown in hydroponic cultures in controlled environment chambers.All climbers had inherently taller shoots than self-supporting plants when compared at an equal amount of total plant dry weight, due to longer stems per unit of support biomass. In contrast to the hypothesis, the relative growth rates of all climbers were relatively low compared to the range found for self-supporting species. The biomass allocation patterns of the non-leguminous climbers were similar to those of the self-supporting species. Leguminous climbers allocated more biomass to support tissue and less biomass to leaves than non-climbers. As a result, height growth was even more emphasized in leguminous climbers than in non-leguminous climbers. Climbing legumes had high rates of net carbon gain, which partly compensated the lower relative leaf weight.We conclude that leguminous herbaceous climbers maximize height growth by a large investment in support biomass, enabling them to keep a large proportion of their leaves in the better illuminated environment at the top of the vegetation canopy.

Vegetative propagation and sexual reproduction in the woodland understorey pseudo-annual Circaea lutetiana L.

On the forest floor of deciduous woodlands, relative light intensity gradually declines during the early growing season. The woodland understorey pseudo-annual Circaea lutetiana L. completes its life-cycle at the end of summer. These pseudo-annuals are clonal plants which survive the winter only as seeds and as hibernacles produced by the rhizome apices. In this paper, we asked several questions related to the life-history of C. lutetiana. It was found that shoot formation in early spring did not exhaust the old hibernacle. A trade-off between rhizome + hibernacle number and weight might be expected when plants grow under resource limitation. It was hypothesised that both number and weight of rhizomes and hibernacles will be affected by light availability. Since the effect of resource supply on the size number trade-off will depend on the developmental pattern of the rhizome system, rhizome development was studied as well. Soon after the shoots emerged, 1st order rhizomes were formed in May on the nodes of the old hibernacle. First-order rhizomes branched in June and 2nd order rhizomes (side-branches) were continuously produced throughout the growing season. The phenology and developmental rate of plants growing in different light treatments were plastic. On average 30% of rhizome biomass was formed during the vegetative phase, and rhizome and fruit production were only partly separated in time. The ratio of total rhizome biomass to total fruit biomass was not affected by light. Also flower bud removal did not lead to an increase in rhizome production, which suggests that division of biomass to both reproductive modes is rather rigid. The number of 1st order rhizomes was not affected by the light treatments. Under light limitation, both rhizome number and weight of single rhizomes were reduced. In contrast, fruit number, but not weight of single fruits, was limited.

Institutional Context for Sustainable Development

With the presentation of the Brundtland UN commission report ‘Our common future’ in 1987 (WCED, 1987) the issue of sustainable develop-ment was put on the political agenda. It was defined as ‘a development that meets the needs of the present without compromising the ability of future generations to meet their own needs’. The concept has been much debated and criticized (Redclift, 1992) and numerous alternative definitions have been proposed (such as Robinson, 2002). (And it has been noted that this was not the first use of the term.)No consensus has been – or is likely to be – reached on any other defi-nition; in part because for most people the concept is normative. What is clear is that the central issue is the potential, or actual, conflict between development and the environment, and hence between the interests of present and future generations (see Weaver and Rotmans, 2006). Ewert et al. (2006) have argued, with respect to the sustainability of agricul-tural systems, that the appropriate definition will depend on the specific problem to be analysed.Our particular concern in this book is the impact on sustainable devel-opment of alternative land use policies in developing countries. While we do not see it as necessary to propose an alternative to the WCED defini-tion of SD, it is appropriate to clarify how we interpret it, as a basis for the analysis that follows.In the literature the term ‘sustainable’ is sometimes used to mean simply ‘capable of lasting over time’; as for example in the expression ‘sustain-able institutions’. To avoid confusion, we will use the term ‘sustainable’ in a more restricted sense: relating specifically to the environment. Thus, in the expression ‘sustainable development’, ‘sustainable’ will refer only to the environmental dimension, and we will avoid referring to a system

A checklist for model credibility, salience, and legitimacy to improve information transfer in environmental policy assessments

Modelers involved in environmental policy assessments are commonly confronted with the lack of uptake of model output by policy actors. Actors have different expectations of models, condensed into three quality criteria: credibility, salience, and legitimacy. The fulfilment of quality criteria is also dynamic as expectations vary, change, and possibly counteract each other. We present a checklist for modelers involved in model-based assessments that is aimed at the identification and monitoring of issues, limitations and trade-offs regarding model quality criteria. It draws upon the literature of integrated assessments as well as case study analysis of environmental policy assessments for the Dutch government, based on expert interviews and embedded experience. The checklist is intended to be consulted during assessments; its application may result in greater awareness among modelers involved in assessments regarding model quality criteria, and may positively affect the uptake of model-based knowledge from environmental policy assessments by policy actors. Model credibility, salience and legitimacy are affected by various factors.Factors are summarized based on interviews, literature and a case study.A model evaluation checklist for modelers is presented to help detect such factors.The checklist may improve the uptake of model-based output by decision makers.

Planning nature in urbanized countries. An analysis of monetary and non-monetary impacts of conservation policy scenarios in the Netherlands

Planning and conserving nature areas are challenging tasks in urbanized and intensively used countries like the Netherlands. This paper supports decision making and public policy debate about these tasks in both an empirical and a methodological way. Empirically, we explore policy alternatives by determining the potential consequences of different nature policy scenarios in the Netherlands. Methodologically, we employ a mixed monetary and non-monetary evaluation method known as multi-criteria cost-benefit analysis (MCCBA). We evaluate four new future directions of Dutch nature policy that address four dominant stakeholder demands: biodiversity conservation, the provision of ecosystem services, recreational potential as well as economic gains. To balance compact presentation of evaluation outcomes on the one hand and information richness of results on the other, we distinguish between two impact indicator sets: three “headline” and ten “elaborate” indicators. Using these indicators we discuss the quantitative assessment of the four nature policy scenarios by comparing them to two other scenarios, reflecting the 2010 stand-still baseline situation (2010) as well as a reference policy (Trend). In total, we evaluate six scenarios; four present new directions and two reflect existing or recently (2010) halted practices. Our findings first of all show that even in an urbanized country like the Netherlands, with its intensive competition among land use functions, serious gains in national and international biodiversity are possible. Second, we find that it is doubtful whether stimulating the provision of regulating ecosystem services in a country which applies intensive and profitable agricultural techniques is beneficial. Other countries or areas that are less suitable for intensive agricultural practices may be more logical for this. Finally we demonstrate that increasing urban recreational green space − a common challenge for many urban areas − can only be achieved at relatively high costs, while it does not seem to lead to relatively high scores on nature appreciation. Nature appreciation seems to be served better by wilder nature than by park-like nature.

Biomass on Peat Soils

Energy security has become a priority as the world’s population increases and its standard of living improves, thus increasing energy consumption. As the demand for energy increases, there is growing concern about the possible exhaustion of finite supplies of fossil fuels in the not-too-distant future. In addition to the problem of availability, combustion of fossil fuels also has negative environmental effects: air pollution (e.g. particulates, nitrogen oxides, carbon monoxide and sulphur dioxide) produced through the combustion of fossil fuels, threatens human health as well as plant and animal life. Furthermore, the combustion of fossil fuels releases carbon dioxide and other greenhouse gases into the atmosphere, thus contributing to an increase in global temperature. These considerations lead to a search for alternative, renewable sources of energy, one of which is bioenergy.