In northern hardwood forests, litter decomposition might be affected by nutrient availability, species composition, stand age, or access by decomposers. We investigated these factors at the Bartlett Experimental Forest in New Hampshire. Leaf litter of early and late successional species was collected from four stands that had full factorial nitrogen and phosphorus additions to the soil and were deployed in bags of two mesh sizes (63 µm and 2 mm) in two young and two mature stands. Litter bags were collected three times over the next 2 years, and mass loss was described as an exponential function of time represented by a thermal sum. Litter from young stands had higher initial N and P concentrations and decomposed more quickly than litter from mature stands (p = 0.005), regardless of where it was deployed. Litter decomposed more quickly in fine mesh bags that excluded mesofauna (p < 0.001), which might be explained by the greater rigidity of the large mesh material making poor contact with the soil. Neither nutrient addition (p = 0.94 for N, p = 0.26 for P) nor the age of the stand in which bags were deployed (p = 0.36) had a detectable effect on rates of litter decomposition. 
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                            Elevated P availability slows N recycling in northern hardwood forests
                        
                    
    
            Nutrient cycling in forest ecosystems can be sensitive to disturbances that change the availability of one nutrient relative to others, altering the synchrony in nutrient cycles that is expected to develop in undisturbed systems. We asked whether the relative availabilities of nitrogen (N) and phosphorus (P) differ with forest successional age after harvest, and tested effects of adding one nutrient on availability and recycling of the other, in a factorial nitrogen (N) × phosphorus (P) fertilization study in multiple early- and mid-successional and mature northern hardwood forest stands in central NH, USA. We did not find effects of forest age on resin-available N:P ratios, which varied widely among successional forest stands and were related to net N mineralization potentials in the forest floor of each stand. P addition suppressed resin-N availability by 31 % and lowered litterfall N recycling by 10 %, but we detected no effects on net N mineralization potentials. P addition also increased nitrification potentials in the organic horizon by up to 60 %, mostly in combination with added N. The effects of added N depended on P; lower resin-P in mature stands and lower litterfall P recycling in stands of all ages were detected only when P was added with N. We conclude that P limitation influences N recycling across forest age classes in these northern hardwoods, with some indication of stronger effects in successional stands. However, net N mineralization potentials better predicted the resin-N response to added P than did stand age. Our results suggest that alleviating P limitation promotes N limitation over time, especially in more rapidly growing successional forests, by increasing biotic demand for N, reducing its recycling in litterfall, and potentially by reducing net N mineralization. 
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                            - Award ID(s):
- 1637685
- PAR ID:
- 10572688
- Publisher / Repository:
- Elsevier
- Date Published:
- Journal Name:
- Forest Ecology and Management
- Volume:
- 570
- Issue:
- C
- ISSN:
- 0378-1127
- Page Range / eLocation ID:
- 122203
- Subject(s) / Keyword(s):
- N and P cycling N:P ratios Northern hardwoods Nutrient fertilization Nutrient limitation Plant-soil feedbacks
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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