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Successional development and agroforestry
Published in Stephen R. Gliessman, V. Ernesto Méndez, Victor M. Izzo, Eric W. Engles, Andrew Gerlicz, Agroecology, 2023
Stephen R. Gliessman, V. Ernesto Méndez, Victor M. Izzo, Eric W. Engles, Andrew Gerlicz
In some natural ecosystems, the frequency, intensity, and scale of disturbance is such that the system never reaches full maturity, but is nevertheless able to maintain the species diversity, resilience, and energy-use efficiency characteristic of a mature ecosystem. Where hurricanes occur, for example, these high-intensity disturbance events—as long as they are low in frequency—help to generate forest systems with both high species diversity and high biomass (Vandermeer et al. 2000; Mascaro et al. 2005). Ecologists studying these systems have posited the intermediate disturbance hypothesis, which states that in natural ecosystems where environmental disturbances are neither too frequent nor too seldom (i.e., at some intermediate frequency) both diversity and productivity can be high (Connell 1978; Connell & Slayter 1977; Bongers et al. 2009). The required level of intermediate disturbance can come about through a variety of different combinations of disturbance frequency, disturbance intensity, and disturbance scale (see Table 15.2). Under these kinds of disturbance regimes, it appears that systems can exhibit the early-successional characteristic of high productivity while retaining the high species diversity characteristic of mature ecosystems.
Soil Invertebrates: Responses to Forest Types in Changbai Mountains
Published in Yeqiao Wang, Landscape and Land Capacity, 2020
Fifty-two taxa of the soil invertebrates were collected in the PMFs and SSFs, the highest among the five forest types. The previous studies revealed that the main factors that could potentially affect soil invertebrates’ diversity included the quality, quantity, and species of plant litter.[14] Comparing with other forests, PMF had the greatest richness of plant species and the most complex community structure of vegetation in the Changbai Mountains.[15] These provided a favorable condition for soil invertebrates in the PMF. Due to the fact that the SFF is in the primary stage of a secondary succession, a variety of pioneer species have emerged. Some previous studies have demonstrated that new species of plants could establish a microenvironment and change the characteristics of the soil humus, which would consequently supply increasing amounts of food for soil invertebrates.[16,17] We also observed that 66,883 ind. m–2 of soil invertebrates were found in the (SMFs), the highest abundance among the five forest types. The intermediate disturbance hypothesis indicates that the intermediate disturbance can promote species diversity in ecological communities and permit more numerous species’ invasion and colonization.[18] Comparing with other forest types in the Changbai Mountains, a relatively intermediate disturbance was found in the SMFs, and it may promote the richness of soil invertebrates. Additionally, the lowest number of soil invertebrates’ taxa (43 taxa) was observed in the SBF. It is known that increased forest stand densities can result in higher amounts of water and nutrients in the lower levels,[19] which restrict the growing of the understory plants.[20] The SBF is mainly composed of Acer mono and Betula platyphylla, and a large number of saplings are in there; thus, it had a highest shrub coverage and a single tree species composition. This resulted in a singleness of the litter species and a deterioration of the soil environment, which consequently decreased species richness of soil invertebrates.
Ecosystems: Planning and Trade-offs
Published in Brian D. Fath, Sven E. Jørgensen, Megan Cole, Managing Biological and Ecological Systems, 2020
Ioan M. Ciumasu, Keith Culver, Mihai Costica, Jean-Paul Vanderlinden
Niemelä describes urban ecology in the context of the relation between ecology and urban planning, where urban planning is a type of land-use planning.[84] He makes the essential observation that urban nature has been regarded in prior studies as a true field experiment about human impact on ecosystems. This resonates with the wider preoccupations with the place of urban areas within the landscapes, for example, with the degrees of vegetation cover[85] or habitat patch corridors to avoid excessive habitat fragmentation in highly urbanized areas and to allow landscape connectivity between local plant/animal populations as part of the wider metapopulations (network of local populations) within landscapes. In a previous communication concerned with the place of cities as a human social construct within local ecosystems, we have described the city in terms of an ecosystem disturbance.[86] Applying current ecological theory—the intermediate disturbance hypothesis (IDH) and island biogeography theory (IB)—we have identified an ecological taxonomy of cities and city areas as a function of disturbance intensity in a local biogeographical context: small city/city periphery (low disturbance intensity), medium-sized city/city near-center (intermediate disturbance intensity), and large city/city center (high disturbance intensity). Within this framework, any urban unit can be described on a gradient of ecological disturbance and in the local biogeographical context, with biodiversity theories and indices serving as proxies for the state and dynamics of ecosystems and ecosystems–humans dynamics.[87,88]
Effects of agricultural landscapes and land uses in highly biodiverse tropical streams of the Ecuadorian Choco
Published in Inland Waters, 2019
Andrés Morabowen, Verónica Crespo-Pérez, Blanca Ríos-Touma
The lack of significance in the community metrics (diversity [S], abundance [N], and density) in streams draining different land use types may be because (1) diversity of these rivers is high enough that the differences can only be seen in certain taxa, and (2) these communities may be resilient to negative impacts because high diversity and high density of macrobenthos allow constant recolonization. Although nonsignificant, macroinvertebrate richness was low in monoculture streams compared to forest and agroforestry lands (Fig. 5), and we did find a significant increase in Shannon diversity (N1) of agroforestry land streams compared to the other land uses. We think this finding might be a case of intermediate disturbance hypothesis (Townsend et al. 1997), in which new niches are open in streams draining these lands.