Effects of hay management and native species sowing on grassland community structure, biomass, and restoration

Landscape heterogeneity is key to forecasting outcomes of plant reintroduction

Conservation and restoration projects often involve starting new populations by introducing individuals into portions of their native or projected range. Such efforts can help meet many related goals, including habitat creation, ecosystem service provisioning, assisted migration, and the reintroduction of imperiled species following local extirpation. The outcomes of reintroduction efforts, however, are highly variable, with results ranging from local extinction to dramatic population growth; reasons for this variation remain unclear. Here, we ask whether population growth following plant reintroductions is governed by variation at two scales: the scale of individual habitat patches to which individuals are reintroduced, and larger among-landscape scales in which similar patches may be situated in landscapes that differ in matrix type, soil conditions, and other factors. Quantifying demographic variation at these two scales will help prioritize locations for introduction and, once introductions take place, forecast population growth. This work took place within a large-scale habitat fragmentation experiment, where individuals of two perennial forb species were reintroduced into eight replicate ~50-ha landscapes, each containing a set of five ~1-ha patches that varied in their degree of isolation (connected by habitat corridors or unconnected) and edge-to-area ratio. Using data on individual growth, survival, reproductive output, and recruitment collected one to two years after reintroduction, we developed models to forecast population growth, then compared forecasts to observed population sizes, three and six years later. Both the type of patch (connected and unconnected) and identity of the landscape to which individuals were reintroduced had effects on forecasted population growth rates, but only variation associated with landscape identity was an accurate predictor of subsequently observed population growth rates. Models that did not include landscape identity had minimal forecasting ability, revealing the key importance of variation at this scale for accurate prediction. Of the five demographic rates used to model population dynamics, seed production was the most important source of forecast error in population growth rates. Our results point to the importance of accounting for landscape-scale variation in demographic models and demonstrate how such models might assist with prioritizing particular landscapes for species reintroduction projects.

Roles of Arbuscular Mycorrhizal Fungi and Soil Abiotic Conditions in the Establishment of a Dry Grassland Community

BACKGROUND

The importance of soil biota in the composition of mature plant communities is commonly acknowledged. In contrast, the role of soil biota in the early establishment of new plant communities and their relative importance for soil abiotic conditions are still poorly understood.

AIMS AND METHODS

The aim of this study was to understand the effects of soil origin and soil fungal communities on the composition of a newly established dry grassland plant community. We used soil from two different origins (dry grassland and abandoned field) with different pH and nutrient and mineral content. Grassland microcosms were established by sowing seeds of 54 species of dry grassland plants into the studied soils. To suppress soil fungi, half of the pots were regularly treated with fungicide. In this way, we studied the independent and combined effects of soil origin and soil community on the establishment of dry grassland communities.

KEY RESULTS

The effect of suppressing the soil fungal community on the richness and composition of the plant communities was much stronger than the effect of soil origin. Contrary to our expectations, the effects of these two factors were largely additive, indicating the same degree of importance of soil fungal communities in the establishment of species-rich plant communities in the soils from both origins. The negative effect of suppressing soil fungi on species richness, however, occurred later in the soil from the abandoned field than in the soil from the grassland. This result likely occurred because the negative effects of the suppression of fungi in the field soil were caused mainly by changes in plant community composition and increased competition. In contrast, in the grassland soil, the absence of soil fungi was limiting for plants already at the early stages of their establishment, i.e., in the phases of germination and early recruitment. While fungicide affects not only arbuscular mycorrhizal fungi but also other biota, our data indicate that changes in the AMF communities are the most likely drivers of the observed changes. The effects of other soil biota, however, cannot be fully excluded.

CONCLUSIONS

These results suggest that the availability of soil fungi may not be the most important limiting factor for the establishment of grassland species in abandoned fields if we manage to reduce the intensity of competition at these sites e.g., by mowing or grazing.

Effects of mowing on methane uptake in a semiarid grassland in northern China

BACKGROUND

Mowing is a widely adopted management practice for the semiarid steppe in China and affects CH(4) exchange. However, the magnitude and the underlying mechanisms for CH(4) uptake in response to mowing remain uncertain.

METHODOLOGY/PRINCIPAL FINDINGS

In two consecutive growing seasons, we measured the effect of mowing on CH(4) uptake in a steppe community. Vegetation was mowed to 2 cm (M2), 5 cm (M5), 10 cm (M10), 15 cm (M15) above soil surface, respectively, and control was set as non-mowing (NM). Compared with control, CH(4) uptake was substantially enhanced at almost all the mowing treatments except for M15 plots of 2009. CH(4) uptake was significantly correlated with soil microbial biomass carbon, microbial biomass nitrogen, and soil moisture. Mowing affects CH(4) uptake primarily through its effect on some biotic factors, such as net primary productivity, soil microbial C\N supply and soil microbial activities, while soil temperature and moisture were less important.

CONCLUSIONS/SIGNIFICANCE

This study found that mowing affects the fluxes of CH(4) in the semiarid temperate steppe of north China.

TMDL implementation in agricultural landscapes: a communicative and systemic approach

Increasingly, total maximum daily load (TMDL) limits are being defined for agricultural watersheds. Reductions in non-point source pollution are often needed to meet TMDL limits, and improvements in management of annual crops appear insufficient to achieve the necessary reductions. Increased adoption of perennial crops and other changes in agricultural land use also appear necessary, but face major barriers. We outline a novel strategy that aims to create new economic opportunities for land-owners and other stakeholders and thereby to attract their voluntary participation in land-use change needed to meet TMDLs. Our strategy has two key elements. First, focused efforts are needed to create new economic enterprises that capitalize on the productive potential of multifunctional agriculture (MFA). MFA seeks to produce a wide range of goods and ecosystem services by well-designed deployment of annual and perennial crops across agricultural landscapes and watersheds; new revenue from MFA may substantially finance land-use change needed to meet TMDLs. Second, efforts to capitalize on MFA should use a novel methodology, the Communicative/Systemic Approach (C/SA). C/SA uses an integrative GIS-based spatial modeling framework for systematically assessing tradeoffs and synergies in design and evaluation of multifunctional agricultural landscapes, closely linked to deliberation and design processes by which multiple stakeholders can collaboratively create appropriate and acceptable MFA landscape designs. We anticipate that application of C/SA will strongly accelerate TMDL implementation, by aligning the interests of multiple stakeholders whose active support is needed to change agricultural land use and thereby meet TMDL goals.