Forests Of Different Ages Research Articles

The fungal and bacterial biomass (selective inhibition) and the production of CO2 and N2O by soddy-podzolic soils of postagrogenic biogeocenoses

In the humus horizon of soddy-podzolic soils of postagrogenic cenoses and primary forests, the contributions of the fungi and bacteria were determined by the selective inhibition of the substrate-induced respiration (SIR) by antibiotics; the basal (microbial) respiration and the net-produced nitrous oxide (N2O) were also determined. The procedure of the SIR separation using antibiotics (cycloheximide and streptomycin) into the fungal and bacterial components was optimized. It was shown that the fungi: bacteria ratio was 1.58, 2.04, 1.55, 1.39, 2.09, and 1.86 for the cropland, fallow, and different-aged forests (20, 45, 90, and 450 years), respectively. The fungal and bacterial production of CO2 in the primary forest soil was higher than in the cropland by 6.3 and 11.4 times, respectively. The production of N2O in the soils of the primary and secondary (90-year-old) forests (3 and 7 ng N-N2O/g soil per hour, respectively) was 2–13 times lower than in the postagrogenic cenoses, where low values were also found for the microbial biomass carbon (Cmic), its components (the Cmic-bacteria and Cmic-fungi), and the portion of Cmic in the organic carbon of the soil. A conclusion was drawn about the misbalance of the microbial processes in the overgrown cropland accompanied by the increased production of N2O by the soil during its enrichment with an organic substrate (glucose).

Relative contributions of soil, foliar, and woody tissue respiration to total ecosystem respiration in four pine forests of different ages

Carbon dioxide (CO2) emissions from soil, foliage, and live woody tissue were measured throughout the year in afforested, white pine (Pinus strobus L.) stands (67, 32, 17, and 4 years old as of 2006), growing in a northern temperate climate. The data were used to estimate annual ecosystem respiration (Re) and its component fluxes, including soil, foliar, and woody tissue respiration; to investigate major environmental factors causing intersite and temporal variability in the observed fluxes; and to compare chamber‐based Re estimates with eddy covariance‐based estimates. While temperature was the dominant driving factor of temporal variability in component fluxes, intersite variability in CO2 emissions was attributed to differences in stand physiological characteristics, such as the presence of the LFH soil horizon, its carbon‐to‐nitrogen ratio, and the amount of canopy cover. Additional factors that contributed to flux variability included the frequency of precipitation events, vapor pressure deficit and stem diameter, depending on the component considered. Estimated annual chamber‐based totals of Re across the four stands were 1526 ± 137, 1278 ± 137, 1985 ± 293, and 773 ± 46 g C m−2 yr−1 for the 67‐, 32‐, 17‐, and 4‐year‐old stands, respectively. Soil respiration dominated emissions at the 4‐year‐old stand, while foliar respiration dominated emissions at the 17‐year‐old stand. In contrast, at the two oldest stands, soil and foliar respirations were comparable. Soil respiration accounted for 44%, 44%, 26%, and 70% of annual Re, across the 67‐, 32‐, 17‐, and 4‐year‐old stands, while foliar respiration accounted for 48%, 41%, 60%, and 30% of annual Re, across the respective sites. Wood respiration was the smallest component of annual Re across the stands (8%, 15%, 14%, and 0.1%, respectively). The chamber‐based Re values were higher than tower‐based eddy covariance Re estimates, on average by 18%, 70%, 18%, and 36% at the 67‐, 32‐, 17‐, and 4‐year‐old stands, respectively. This study contributes to our general understanding of the age‐related effects and the role of climate on carbon emissions from various components of afforested ecosystems. Our results suggest that foliar respiration could be comparable to or higher than soil respiration in its contribution to Re in young to mature, planted or afforested, ecosystems. They also suggest that site quality and stand age are important factors to be considered in future studies of carbon dynamics of afforested stands.

Mangrove Forest and Soil Development on a Rapidly Accreting Shore in New Zealand

Mangrove forests are rapidly expanding their distribution in New Zealand, which is at the southern limit of their range. We investigated how these expanding mangrove forests develop through time. We assessed patterns in forest structure and function at the Firth of Thames, which is a rapidly accreting mangrove site in New Zealand where 1 km of mangrove of Avicennia marina has established seaward since the 1950s. Across the intertidal region, mangrove forest structure was highly variable. We used bomb-pulse radiocarbon dating to age the forest. Two major forest establishment events were identified; one in 1978–1981 and another in 1991–1995. These events coincided with sustained El Nino activity and are likely the result of reduced wind and wave energy at the site during these periods. We used the two forests of different ages to assess whether mangroves in New Zealand mature at similar rates as other mangroves and whether they conform to classic models of succession. The timing of forest maturation is similar in New Zealand as in more tropical locations with trees exhibiting features of mature forests as they age from about 10 to about 30 years. In older forest (~30 years old) trees become larger and stands more homogenous than in the younger forest (~10 years old). Carbon and nutrient concentrations in soils increased and soils become more aerobic in older forest compared to younger forest. Additionally, using fertilization experiments, we established that despite reduced growth rates in older forests, nitrogen remained limiting to growth in both older and young forests. However, in contrast to classic successional models leaf tissue nutrient concentrations and nutrient conservation (nutrient resorption from senescence leaf tissue) were similar in forests of differing ages and did not vary with fertilization. We conclude that mangrove forest expansion in New Zealand is influenced by climatic factors. Mangrove forests mature rapidly, even at the limits of their range and they satisfy many of the successional patterns predicted by Odum (1969) for the early stages of forest succession.

Accumulation of Soil Carbon and Phosphorus Contents of a Rehabilitated Forest

The world's tropical rainforests are decreasing at an alarming rate as they are converted to agricultural land, pasture, and plantations. Decreasing tropical forests affect global warming. As a result, afforestation progams have been suggested to mitigate this problem. The objective of this study was to determine the carbon and phosphorus accumulation of a rehabilitated forest of different ages. The size of the study area was 47.5 ha. Soil samples were collected from the 0-, 6-, 12-, and 17-year-old rehabilitated forest. Twenty samples were taken randomly with a soil auger at depths of 0–20 and 20–40 cm. The procedures outlined in the Materials and Methods section were used to analyze the soil samples for pH, total C, organic matter, total P, C/P ratio, yield of humic acid (HA), and cation exchange capacity (CEC). The soil pH decreased significantly with increasing age of forest rehabilitation regardless of depth. Age did not affect CEC of the rehabilitated forest. Soil organic matter (SOM), total C, and total P contents increased with age. However, C/P ratio decreased with time at 0–20 cm. Accumulation of HA with time and soil depth was not consistent. The rehabilitated forest has shown signs of being a C and P sink.

Conservation implications of rainforest use patterns: mature forests provide more resources but secondary forests supply more medicine

Summary 1. Tropical rainforests are a global conservation priority. Robust arguments supporting rainforest conservation can attract funding and shape land‐use management. However, some popular assertions regarding the value of tropical forests remain largely untested. 2. This study tests the validity of two arguments in support of mature tropical rainforest conservation: first, that these forests should be conserved based on their value as potential sources of medicine. This argument requires mature forests to be better sources of medicine than alternative land‐use types, including secondary forests. Second, secondary forest use may help conserve mature forests by providing sufficient resources to buffer against resource extraction in mature forests. 3. The research was conducted in three communities in the Cordillera Azul, Peru, where 369 individuals from 66 households were surveyed. Participants recorded all flora and fauna collected in mature (>20 years) and secondary forests over 180 days in six use categories (food, medicine, wood, weavings, adornments and ‘other’). Ecological knowledge of secondary and mature forest species was assessed for male and female household heads. 4. Households used 346 folk species (as defined by local classification systems) from 3668 collection events. Individuals had better knowledge of secondary forest species, but more access to mature forests. Participants collected significantly more medicines from secondary than from mature forests. In other major use categories (food, wood, weaving, adornment), secondary forests provided fewer resources than mature forests. Participants collected a different set of species from secondary and mature forests, with only 130 folk species (38%) collected in both secondary and mature forests. 5. Synthesis and applications. The arguments to protect mature rainforests as sources of new drugs may be overstated, because secondary forests can provide more medicinal plant resources than mature forests, and landscapes that incorporate forests of different ages can maximize availability of medicinal plant species. Conservation efforts must take a landscape level approach given the spread of resource use across different forest types. Because of the heterogeneity of resource availability and use among community members, and the dynamic nature of resource use on forest frontiers, conservation should embrace participatory adaptive management approaches that incorporate a variety of resource users.

Plant functional constraints on foliar N:P ratios in a tropical forest landscape

AbstractAlthough large scale analyses of foliar N:P ratios suggest and overall pattern of P limitation in tropical forests, analyses within the biome are less indicative of a consistent pattern of nutrient limitation. High tree species diversity and soil heterogeneity are important factors driving the variability of foliar chemistry in the tropics; however, this variability could be reduced at the level of the functional characteristics of the species present at a site. In this study it is hypothesized that foliar N:P ratios would be more constrained when the species are grouped according to functional characteristics, and would reveal patterns of nutrient limitation. The study was conducted in a tropical forest landscape of the Porce region in Colombia, which consists of patches of primary and secondary forests of different ages. The functional groupings revealed consistent patterns of conservative N cycling in species present at young secondary sites, as well as conservative P cycling of the species present later in succession and in primary forests. Although the observed data have limitations in terms of capturing the overall variability for each functional group, the classification used here provided support for the proposed hypotheses. It is concluded that functional composition, rather than taxonomic composition, can potentially improve our understanding of nutrient cycling in tropical forests.

Differential susceptibility of tree species to oviposition by periodical cicadas

Abstract 1. Periodical cicadas occur widely in deciduous forests of eastern North America and represent the largest insect emergences in the world. Their effects on forest community dynamics, via oviposition damage and root feeding, are potentially great but not well understood. If tree species vary in their susceptibility to cicada oviposition and root colonization, then periodical cicadas may affect ecological interactions among tree species and forest composition.2. We measured oviposition damage on 63 tree species at 52 sites in southern Indiana, U.S.A. for two broods of periodical cicadas. We compared oviposition damage among different sites, habitats, and tree species. We also measured cicada emergence rates in mature and successional forest habitats and from beneath different tree species.3. Certain tree species received significantly more oviposition damage than others, and the most and least damaged species were consistent between the two broods. For some species, oviposition damage varied between mature and successional sites. Despite the differences in oviposition rates among species, there was no difference in emergence rates from beneath different tree species, suggesting that initial differences in cicada density among tree species are not maintained through the nymphal life cycle.4. Cicadas oviposited more at successional sites, but emerged more in mature forest stands, suggesting that successive generations of cicadas represent a shifting mosaic between forests of different ages. As tree species consistently vary in their susceptibility to oviposition damage, periodical cicadas could alter local competitive interactions and therefore affect forest dynamics.

Soil quality and organic carbon ratios in mountain agroecosystems of South-east Spain

Soil physical and chemical characteristics as well as climatic and geomorphological factors have been determined in 68 sites of a mountain calcimorphic ecosystem (Sierra María-Los Vélez Natural Park, Almería) in Southeastern Spain. Land use and vegetation were natural pine forest, evergreen oak forest, reforested pine forest of different ages, bush, juniper forest, and olive, almond and cereal crops under conventional tillage. By using multivariate data treatments, 17 soil variables were processed. A large part of the total variability was controlled by local topographical features through their effect on moisture retention and vegetation. Most characteristics were significantly correlated with total organic C (mean = 28.5 ± 4.6 g kg − 1 ), which demonstrates the central role of the organic matter in the functioning of the whole ecosystem. New soil quality descriptors consisting of ratios to soil organic carbon were obtained, informing about the specific activity (per C unit) or performance of the organic matter, independently of its total content. When soil data are directly processed by using principal component analysis, we found a set of high quality soils under natural and old reforested forests, where environmental services provided by soil depend on the high levels of quality descriptors related to organic carbon, e.g. cation exchange capacity (CEC), total porosity, or aggregate stability. When variables such as CEC, porosity and aggregate stability are calculated as ratios to the total organic carbon, a new classification pattern is obtained, allowing to detect soils with organic matter of high maturity which in general do not coincide with soils with high organic matter content. The results suggest the assessment of soil quality based on ratios informing on the organic matter performance should be emphasized as an alternative to direct descriptors based on the total organic carbon content.

Cryptogams in Estonian Alvar Forests: Species Composition and their Substrata in Stands of Different Age and Management Intensity

Species-rich alvar forests represent a rare vegetation type in northern Europe. They grow locally on shallow soils formed on calcareous parent material. The aim of this study was to compare cryptogam species richness and composition on various substrata in alvar forests of different age and management rate. Altogether 101 bryophyte and 54 lichen species were recorded. Substratum explained species variance more than did the stand age or management intensity. Younger and older forests had a different bryophyte and lichen species composition. Decaying wood was the richest as cryptogam species substratum. It had quite a unique bryophyte composition, including a high amount of hepatics. Juniperus communis appeared to be an important substratum for cryptogam species diversity in alvar forests. Bryophyte species composition appeared to be similar on the bases of Pinus sylvestris, Betula pendula and Picea abies and different on J. communis. Most of the recorded threatened bryophyte species grew in old subnatural ...

Phosphorus cycling in primary and secondary seasonally dry tropical forests in Mexico

• Primary forests in the seasonally dry tropical regions of Mexico are disappearing under land-use pressure, creating a mosaic of secondary forests of different ages. • In this study we measured the aboveground litterfall phosphorus (P) fluxes, litter-layer and soil P pools to compare the P cycles in primary and secondary seasonally dry tropical forests. Our hypothesis was that the previous agricultural land use of secondary forests would bring about a lower P flux in the litterfall, lower soil P pool, and higher nutrient resorption proficiency than in primary forests, as well as an increase of relative amounts of available P provided by the soil with forest aging. • The expected litterfall P flux increase in the secondary forest following a previous agricultural land use did not occur. Phosphorus return to the soil by aboveground litterfall was unaffected by the succession stage of the forest. In addition, the total soil P pool did not change with forest age. However, available soil P (bicarbonate P-inorganic and P-organic pools) and hydroxide inorganic P pools were higher in primary than in secondary forest soils. Phosphorus concentration in litterfall increased significantly with forest age, suggesting that P is cycled more efficiently (by a higher nutrient resorption proficiency) when soil available P is less abundant. Despite these differences among forests, the results of our study gave evidence that P requirements by plants in primary and secondary forests are sufficiently met by the accumulation of dissolved (water extractable) P in the forest floor during the dry season and by soil bicarbonate-P pools. • Our study on the effects of land cover change on P cycling, following the discontinuation of agricultural practices, leads to the conclusion that this ecosystem P dynamics will vary depending on the successional stage of the forests, and is strongly influenced by the seasonal rainfall pattern which determines plant-available P.

Bryophytes and decaying wood in Hepatica site-type boreo-nemoral Pinus sylvestris forests in Southern Estonia

The aim of the study was to establish the amount of decaying wood (logs and stumps) in various groups of Hepatica site-type pine forests of different age and management intensity and to analyse the composition of bryophytes in dependence of these factors. The average volume of CWD in old unmanaged forests was 47.5 m 3/ha, which is rather well comparable with respective estimations from Fennoscandia. Reduced human impact contributes positively to the amount of CWD. Diversity of log diameter classes and decay stages is larger in old forests. Altogether 73 bryophyte species were recorded, 65 species on logs and 55 on stumps. Species richness on stumps was higher in managed forests than in unmanaged ones. At the same time, the species having high indicator value for man-cut stumps are very common species in boreal forests and grow on other substrata as well. Species composition and ecological conditions differed between stumps and logs. Logs are more humid microhabitats than stumps, therefore the occurrence of hepatics is more frequent on them. According to species composition on decaying wood the old unmanaged forests distinguished from others. As the differences of substratum characteristics were notable between old and young forests, the stand age described a considerable part of species variance on logs.

Altitudinal differences in the leaf fitness of juvenile and mature alpine spruce trees (Picea crassifolia)

In many plant species, leaf morphology varies with altitude, an effect that has been attributed to temperature. It remains uncertain whether such a trend applies equally to juvenile and mature trees across altitudinal gradients in semi-arid mountain regions. We examined altitude-related differences in a variety of needle characteristics of juvenile (2-m tall) and mature (5-m tall) alpine spruce (Picea crassifolia Kom.) trees growing at altitudes between 2501 and 3450 m in the Qilian Mountains of northwest China. We found that stable carbon isotope composition (delta(13)C), area- and mass-based leaf nitrogen concentration (N(a), N(m)), number of stomata per gram of nitrogen (St/N), number of stomata per unit leaf mass (St/LM), projected leaf area per 100 needles (LA) and leaf mass per unit area (LMA) varied nonlinearly with altitude for both juvenile and mature trees, with a relationship reversal point at about 3100 m. Stomatal density (SD) of juvenile trees remained unchanged with altitude, whereas SD and stomatal number per unit length (SNL) of mature spruce initially increased with altitude, but subsequently decreased. Although several measured indices were generally found to be higher in mature trees than in juvenile trees, N(m), leaf carbon concentration (C(m)), leaf water concentration (LWC), St/N, LA and St/LM showed inconsistent differences between trees of different ages along the altitudinal gradient. In both juvenile and mature trees, delta(13)C correlated significantly with LMA, N(m), N(a), SNL, St/LM and St/N. Stomatal density, LWC and LA were only significantly correlated with delta(13)C in mature trees. These findings suggest that there are distinct ecophysiological differences between the needles of juvenile and mature trees that determine their response to changes in altitude in semi-arid mountainous regions. Variations in the fitness of forests of different ages may have important implications for modeling forest responses to changes in environmental conditions, such as predicted future temperature increases in high altitude areas associated with climate change.

Changes of macro-benthic faunal community with stand age of rehabilitated Kandelia candel mangrove in Jiulongjiang Estuary, China

Distribution properties of macro-benthic faunal communities were compared among rehabilitated Kandelia candel forests of different ages in Jiulongjiang Estuary, China. From July 2005 to April 2006, seasonal surveys were conducted within four representative forests—K4, K7, K19 and K43, with ages of 4, 7, 19 and 43 years, respectively. Two non-vegetated flats (NF1 and NF2) were set as the references. Numbers of faunal species in rehabilitated forests were higher than NF1 and NF2, while younger forests (K4 and K7) generally had more macro-benthic fauna species than older ones (K19 and K43). Among the total 24 species recorded, Uca arcuata, Metaplax elegans, Phascolosoma esculenta and Littoraria melanostoma were dominant. Macro-benthic faunal community structures were different among the four rehabilitated K. candel forests. The dominant species in younger forests was M. elegans, while U. arcuata had a higher abundance than M. elegans in non-vegetation flats and older forests. Gastropods were abundant in younger forests. Distribution properties of dominant species differed among rehabilitated K. candel forests. U. arcuata had the largest density in non-vegetated flats, and was infrequent in younger forests. M. elegans had high abundances in younger forests. High abundance of P. esculenta was found in older forests, while L. melanostoma was more abundant in younger forests. Since both macro-benthic faunal community and vegetation were similar in K19 and K43, rehabilitated K. candel mangrove was considered steady 19 years after being planted. That is, in the case of macro-benthic fauna and vegetation, a K. candel mangrove may evolve to a mature state at a stand age of about 20 years.

Decomposition of organic matter and nutrient mineralisation in wood ant (Formica rufa group) mounds in boreal coniferous forests of different age

Wood ants (Formica rufa group) are dominating ecosystem elements of the boreal region due to their wide and abundant occurrence. They collect and concentrate organic material from the surrounding forest floor by building large above-ground mounds. These mounds have higher temperature and lower water content than the surrounding forest floor. We studied how these peculiar environmental conditions affected mass loss and carbon (C), nitrogen (N), phosphorus (P) and potassium (K) mineralisation of organic matter in boreal Norway spruce (Picea abies L. Karst.)-dominated mixed forest stands of four different age classes (5-, 30-, 60-, and 100-year-old) situated in eastern Finland using the litter bag technique. Norway spruce needle litter was incubated in inhabited and abandoned wood ant mounds as well as on the surrounding forest floor. We expected decomposition to be extremely slow due to the dryness of the mounds. Mass losses inside inhabited mounds were lower compared to the surrounding forest floor (on average 30 vs 50% after 2 years) but not as low as we expected, which might be a result of ant and microbial activity in the mounds. Decomposition in the abandoned mounds proceeded similarly as on the forest floor. Nutrient mineralisation proceeded more slowly in the ant mounds than on the surrounding forest floor. Mineralisation occurred for all studied nutrients in the ant mounds, except for N, which net amount remained stable during the years of the experiment. When wood ant mounds are abandoned and their porous and dry structure is no longer maintained by the ants, their decomposition is accelerated, and nutrients may be available for uptake by plants, although the nutrient mineralisation seems still to remain lower compared to the surrounding forest floor. However, eventually the mound material will be decomposed and nutrients mineralised, thus providing a nutrient hot spot increasing the heterogeneity of forest floor nutrient availability.

Resource use and seed dispersal by red howler monkeys (<i>Alouatta seniculus</i>) in a Colombian Andean forest


 
 
 As part of a study of responses by red howler monkeys (Alouatta seniculus) to forest fragmentation, we studied red howlers in an extensive forest including a habitat mosaic of old-growth forest, secondary forest of different ages, and non-commercial monospecific plantations of exotic Chinese ash (Fraxinus chinensis) and pines, to produce baseline information on resource use and their role as seed dispersers. We followed three troops for six months, encompassing a dry and a wet season; in total, they fed on 48 species of trees, including fruits, leaves and flowers, but each group relied on a limited set of species available within its home range, particularly in the Moraceae and Cecropiaceae. This contrasts with lowland forest, where howlers feed on a larger variety of species. We observed no season of generalized fruit scarcity, as is the case in the lowlands. However, localized fruit scarcities in howler home ranges occurred. Howlers fed on relatively small quantities of leaves when fruit was available, and became primarily folivorous when fruit was unavailable. Howlers transported a mean of 2.3 species of seeds per fecal sample, to a mean distance of 116 m from the parent tree. More importantly, howlers are transporting seeds to ash and pine plantations, helping to enrich these habitats.
 
 

The influence of pine forests of different ages on the biological activity of layland soils in the middle Angara River basin

The influence of pine forests of different ages (from 25 to 85 years) restoring on old plow land soils is reflected in the biological processes proceeding in them. The drastic decrease in the absolute and relative number of actinomycetes, along with an increase of the fungal population in the microbial complexes of the soils (within the whole profiles), indicates that the microbocenoses acquire “forest” properties. In the soils under the younger pine forests, the processes of microbiological mineralization and specific respiration activity are more active than in the soils under the older pine forests. With the age of the pine forests, the soil profiles become more differentiated according to the eluvial-illuvial type.

Mycorrhizal fungal diversity in willow forests of different age along the river Waal, The Netherlands

In The Netherlands, riparian edge forests are often dominated by Salix species because they are well adapted to anaerobic soil conditions. Willows play therefore an important role in rehabilitation of natural riparian edge forests. They associate with both arbuscular mycorrhizal (AM) and ectomycorrhizal (EM) fungi which are essential for successful restoration of natural ecosystems, but it is still unknown what communities of mycorrhizal fungi develop on Salix species in this environment. Salix alba L. (white willow) forests of three different ages (10, 20 and 60 years old) under restoration management along the river Waal were studied by molecular techniques to describe species composition of mycorrhizal fungi in roots and soil surrounding the trees. Presence of AM colonization was not determined in the roots of S. alba and only EM fungi were observed. Frequencies of EM root tips were below 9% at all sites. Twelve types of mycorrhizal fungi were distinguished in the roots. The mycorrhizal below-ground communities were dominated by Tuber species and to our best knowledge, this is the first molecular indication that Tuber spp. are associated with roots of Salix species. The basidiomycetous fungi including Hebeloma and thelephoroid spp. were found mainly in the 20-year-old forest with the lowest soil nutrient concentrations and were apparently able to withstand flooding. A tendency was observed for higher frequencies of mycorrhizal roots with lower nutrient concentrations and higher soil pH among the sites of different age. The results demonstrate that only a limited number of mycorrhizal fungi can resist the harsh conditions caused by flooding and drought.

Collembolan community dynamics during deciduous forests regeneration in Japan

Summary The structure and feeding group composition of collembolan communities were studied in secondary deciduous forests of different ages to investigate the collembolan community response to environmental changes associated with forest cycles. The study was carried out at eight sites forming a chronosequence (1, 4, 12, 24, 51, 54, 71 and 128 years after clear cutting) of deciduous forest stands in northern Ibaraki (Japan). Total collembolan density and species richness was low at the 1-year-old site, and there was little difference in density among sites over 4 years of age. The density of sucking feeders was especially low at the 1-year-old site. Species richness of trees of a diameter at breast height (DBH)

DIVERSITY OF ARBOREAL SPIDERS IN PRIMARY AND DISTURBED TROPICAL FORESTS

Abstract This study investigates how arboreal spider communities in SE-Asian primary lowland rain forests change after anthropogenic disturbance. Two types of secondary forests were distinguished: 1) forests adjacent to each other, which finally merged into primary forest and 2) forests that were isolated by at least 10 km from the primary forest. Three forests of different age were investigated from each type and compared with undisturbed primary forest. All disturbed forests had been used some years for agriculture and were then left between 5 and 50 years to regenerate naturally. Spiders from at least seven trees per forest type were collected using insecticidal knockdown fogging and sorted to species or morphospecies level. Spiders represented between 5–10% of all canopy arthropods. A similar number of spiders were collected per square meter from all trees. However, communities in the primary forest differed greatly in their alpha- and beta-diversity and in community structure from those in the distur...

Modeling the age of tropical moist forest fragments in heavily-cleared lowland landscapes of Colombia

Increasingly, large areas of native tropical forests are being transformed into a mosaic of human dominated land uses with scattered mature remnants and secondary forests. In general, at the end of the land clearing process, the landscape will have two forest components: a stable component of surviving mature forests, and a dynamic component of secondary forests of different ages. As the proportion of mature forests continues to decline, secondary forests play an increasing role in the conservation and restoration of biodiversity. This paper aims to predict and explain spatial and temporal patterns in the age of remnant mature and secondary forests in lowland Colombian landscapes. We analyse the age distributions of forest fragments, using detailed temporal land cover data derived from aerial photographs. Ordinal logistic regression analysis was applied to model the spatial dynamics of mature and secondary forest patches. In particular, the effect of soil fertility, accessibility and auto-correlated neighbourhood terms on forest age and time of isolation of remnant patches was assessed. In heavily transformed landscapes, forests account for approximately 8% of the total landscape area, of which three quarters are comprised of secondary forests. Secondary forest growth adjacent to mature forest patches increases mean patch size and core area, and therefore plays an important ecological role in maintaining landscape structure. The regression models show that forest age is positively associated with the amount of neighbouring forest, and negatively associated with the amount of neighbouring secondary vegetation, so the older the forest is the less secondary vegetation there is adjacent to it. Accessibility and soil fertility also have a negative but variable influence on the age of forest remnants. The probability of future clearing if current conditions hold is higher for regenerated than mature forests. The challenge of biodiversity conservation and restoration in dynamic and spatially heterogeneous landscape mosaics composed of mature and secondary forests is discussed.